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Tuesday, October 20, 2020

Energy storage

From Wikipedia, the free encyclopedia

The Llyn Stwlan dam of the Ffestiniog Pumped Storage Scheme in Wales. The lower power station has four water turbines which can generate a total of 360 MW of electricity for several hours, an example of artificial energy storage and conversion.

Energy storage is the capture of energy produced at one time for use at a later time. A device that stores energy is generally called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.

Some technologies provide short-term energy storage, while others can endure for much longer. Bulk energy storage is currently dominated by hydroelectric dams, both conventional as well as pumped. Grid energy storage is a collection of methods used for energy storage on a large scale within an electrical power grid.

Common examples of energy storage are the rechargeable battery, which stores chemical energy readily convertible to electricity to operate a mobile phone, the hydroelectric dam, which stores energy in a reservoir as gravitational potential energy, and ice storage tanks, which store ice frozen by cheaper energy at night to meet peak daytime demand for cooling. Fossil fuels such as coal and gasoline store ancient energy derived from sunlight by organisms that later died, became buried and over time were then converted into these fuels. Food (which is made by the same process as fossil fuels) is a form of energy stored in chemical form.

History

Recent history

In the 20th century grid, electrical power was largely generated by burning fossil fuel. When less power was required, less fuel was burned. Concerns with air pollution, energy imports, and global warming have spawned the growth of renewable energy such as solar and wind power. Wind power is uncontrolled and may be generating at a time when no additional power is needed. Solar power varies with cloud cover and at best is only available during daylight hours, while demand often peaks after sunset (see duck curve). Interest in storing power from these intermittent sources grows as the renewable energy industry begins to generate a larger fraction of overall energy consumption.

Off grid electrical use was a niche market in the 20th century, but in the 21st century, it has expanded. Portable devices are in use all over the world. Solar panels are now common in the rural settings worldwide. Access to electricity is now a question of economics and financial viability, and not solely on technical aspects. However, powering transportation without burning fuel remains in development.

Methods

Outline

The following list includes a variety of types of energy storage:

Mechanical

Energy can be stored in water pumped to a higher elevation using pumped storage methods or by moving solid matter to higher locations (gravity batteries). Other commercial mechanical methods include compressing air and flywheels that convert electric energy into internal energy or kinetic energy and then back again when electrical demand peaks.

Hydroelectricity

Hydroelectric dams with reservoirs can be operated to provide electricity at times of peak demand. Water is stored in the reservoir during periods of low demand and released when demand is high. The net effect is similar to pumped storage, but without the pumping loss.

While a hydroelectric dam does not directly store energy from other generating units, it behaves equivalently by lowering output in periods of excess electricity from other sources. In this mode, dams are one of the most efficient forms of energy storage, because only the timing of its generation changes. Hydroelectric turbines have a start-up time on the order of a few minutes.

Pumped hydro

The Sir Adam Beck Generating Complex at Niagara Falls, Canada, which includes a large pumped storage hydroelectricity reservoir to provide an extra 174 MW of electricity during periods of peak demand.

Worldwide, pumped-storage hydroelectricity (PSH) is the largest-capacity form of active grid energy storage available, and, as of March 2012, the Electric Power Research Institute (EPRI) reports that PSH accounts for more than 99% of bulk storage capacity worldwide, representing around 127,000 MW. PSH energy efficiency varies in practice between 70% and 80%, with claims of up to 87%.

At times of low electrical demand, excess generation capacity is used to pump water from a lower source into a higher reservoir. When demand grows, water is released back into a lower reservoir (or waterway or body of water) through a turbine, generating electricity. Reversible turbine-generator assemblies act as both a pump and turbine (usually a Francis turbine design). Nearly all facilities use the height difference between two water bodies. Pure pumped-storage plants shift the water between reservoirs, while the "pump-back" approach is a combination of pumped storage and conventional hydroelectric plants that use natural stream-flow.

Compressed air

A compressed air locomotive used inside a mine between 1928 and 1961.

Compressed air energy storage (CAES) uses surplus energy to compress air for subsequent electricity generation. Small-scale systems have long been used in such applications as propulsion of mine locomotives. The compressed air is stored in an underground reservoir, such as a salt dome.

Compressed-air energy storage (CAES) plants can bridge the gap between production volatility and load. CAES storage addresses the energy needs of consumers by effectively providing readily available energy to meet demand. Renewable energy sources like wind and solar energy vary. So at times when they provide little power, they need to be supplemented with other forms of energy to meet energy demand. Compressed-air energy storage plants can take in the surplus energy output of renewable energy sources during times of energy over-production. This stored energy can be used at a later time when demand for electricity increases or energy resource availability decreases.

Compression of air creates heat; the air is warmer after compression. Expansion requires heat. If no extra heat is added, the air will be much colder after expansion. If the heat generated during compression can be stored and used during expansion, efficiency improves considerably. A CAES system can deal with the heat in three ways. Air storage can be adiabatic, diabatic, or isothermal. Another approach uses compressed air to power vehicles.

Flywheel

The main components of a typical flywheel.
 
A Flybrid Kinetic Energy Recovery System flywheel. Built for use on Formula 1 racing cars, it is employed to recover and reuse kinetic energy captured during braking.

Flywheel energy storage (FES) works by accelerating a rotor (a flywheel) to a very high speed, holding energy as rotational energy. When energy is added the rotational speed of the flywheel increases, and when energy is extracted, the speed declines, due to conservation of energy.

Most FES systems use electricity to accelerate and decelerate the flywheel, but devices that directly use mechanical energy are under consideration.

FES systems have rotors made of high strength carbon-fiber composites, suspended by magnetic bearings and spinning at speeds from 20,000 to over 50,000 revolutions per minute (rpm) in a vacuum enclosure. Such flywheels can reach maximum speed ("charge") in a matter of minutes. The flywheel system is connected to a combination electric motor/generator.

FES systems have relatively long lifetimes (lasting decades with little or no maintenance; full-cycle lifetimes quoted for flywheels range from in excess of 105, up to 107, cycles of use), high specific energy (100–130 W·h/kg, or 360–500 kJ/kg) and power density.

Solid mass gravitational

Changing the altitude of solid masses can store or release energy via an elevating system driven by an electric motor/generator. Studies suggest energy can begin to be released with as little as 1 second warning, making the method a useful supplemental feed into an electricity grid to balance load surges.

Efficiencies can be as high as 85% recovery of stored energy.

This can be achieved by siting the masses inside old vertical mine shafts or in specially constructed towers where the heavy weights are winched up to store energy and allowed a controlled descent to release it. At 2020 a prototype vertical store is being built in Edinburgh , Scotland 

Potential energy storage or gravity energy storage was under active development in 2013 in association with the California Independent System Operator. It examined the movement of earth-filled hopper rail cars driven by electric locomotives from lower to higher elevations.er proposed methods include:-

  • using rails and cranes to move concrete weights up and down;
  • using high-altitude solar-powered balloon platforms supporting winches to raise and lower solid masses slung underneath them,
  • using winches supported by an ocean barge to take advantage of a 4 km (13,000 ft) elevation difference between the sea surface and the seabed,
District heating accumulation tower from Theiss near Krems an der Donau in Lower Austria with a thermal capacity of 2 GWh

Thermal

Thermal energy storage (TES) is the temporary storage or removal of heat.

Sensible heat thermal

Sensible heat storage take advantage of sensible heat in a material to store energy.

Seasonal thermal energy storage (STES) allows heat or cold to be used months after it was collected from waste energy or natural sources. The material can be stored in contained aquifers, clusters of boreholes in geological substrates such as sand or crystalline bedrock, in lined pits filled with gravel and water, or water-filled mines. Seasonal thermal energy storage (STES) projects often have paybacks in four to six years. An example is Drake Landing Solar Community in Canada, for which 97% of the year-round heat is provided by solar-thermal collectors on the garage roofs, with a borehole thermal energy store (BTES) being the enabling technology. In Braedstrup, Denmark, the community's solar district heating system also uses STES, at a temperature of 65 °C (149 °F). A heat pump, which is run only when there is surplus wind power available on the national grid, is used to raise the temperature to 80 °C (176 °F) for distribution. When surplus wind generated electricity is not available, a gas-fired boiler is used. Twenty percent of Braedstrup's heat is solar.

Latent heat thermal (LHTES)

Latent heat thermal energy storage systems work by transferring heat to or from a material to change its phase. A phase-change is the melting, solidifying, vaporizing or liquifying. Such a material is called a phase change material (PCM). Materials used in LHTESs often have a high latent heat so that at their specific temperature, the phase change absorbs a large amount of energy, much more than sensible heat.

A steam accumulator is a type of LHTES where the phase change is between liquid and gas and uses the latent heat of vaporization of water.

Cryogenic thermal energy storage

Air can be liquefied by cooling using electricity and stored as a cryogen with existing technologies.. The liquid air can then be expanded through a turbine and the energy recovered as electricity. The system was demonstrated at a pilot plant in the UK in 2012 . [38]

Electrochemical

Rechargeable battery

A rechargeable battery bank used as an uninterruptible power supply in a data center

A rechargeable battery comprises one or more electrochemical cells. It is known as a 'secondary cell' because its electrochemical reactions are electrically reversible. Rechargeable batteries come in many shapes and sizes, ranging from button cells to megawatt grid systems.

Rechargeable batteries have lower total cost of use and environmental impact than non-rechargeable (disposable) batteries. Some rechargeable battery types are available in the same form factors as disposables. Rechargeable batteries have higher initial cost but can be recharged very cheaply and used many times.

Common rechargeable battery chemistries include:

  • Lead–acid battery: Lead acid batteries hold the largest market share of electric storage products. A single cell produces about 2V when charged. In the charged state the metallic lead negative electrode and the lead sulfate positive electrode are immersed in a dilute sulfuric acid (H2SO4) electrolyte. In the discharge process electrons are pushed out of the cell as lead sulfate is formed at the negative electrode while the electrolyte is reduced to water.
  • Lead-acid battery technology has been developed extensively. Upkeep requires minimal labor and its cost is low. The battery's available energy capacity is subject to a quick discharge resulting in a low life span and low energy density.
Flow battery

A flow battery works by passing a solution over a membrane where ions are exchanged to charge or discharge the cell. Cell voltage is chemically determined by the Nernst equation and ranges, in practical applications, from 1.0 V to 2.2 V. Storage capacity depends on the volume of solution. A flow battery is technically akin both to a fuel cell and an electrochemical accumulator cell. Commercial applications are for long half-cycle storage such as backup grid power.

Supercapacitor

One of a fleet of electric capabuses powered by supercapacitors, at a quick-charge station-bus stop, in service during Expo 2010 Shanghai China. Charging rails can be seen suspended over the bus.

Supercapacitors, also called electric double-layer capacitors (EDLC) or ultracapacitors, are a family of electrochemical capacitors that do not have conventional solid dielectrics. Capacitance is determined by two storage principles, double-layer capacitance and pseudocapacitance.

Supercapacitors bridge the gap between conventional capacitors and rechargeable batteries. They store the most energy per unit volume or mass (energy density) among capacitors. They support up to 10,000 farads/1.2 Volt, up to 10,000 times that of electrolytic capacitors, but deliver or accept less than half as much power per unit time (power density).

While supercapacitors have specific energy and energy densities that are approximately 10% of batteries, their power density is generally 10 to 100 times greater. This results in much shorter charge/discharge cycles. Also, they tolerate many more charge-discharge cycles than batteries.

Supercapacitors have many applications, including:

  • Low supply current for memory backup in static random-access memory (SRAM)
  • Power for cars, buses, trains, cranes and elevators, including energy recovery from braking, short-term energy storage and burst-mode power delivery

Other chemical

Power to gas

Power to gas is the conversion of electricity to a gaseous fuel such as hydrogen or methane. The three commercial methods use electricity to reduce water into hydrogen and oxygen by means of electrolysis.

In the first method, hydrogen is injected into the natural gas grid or is used for transportation. The second method is to combine the hydrogen with carbon dioxide to produce methane using a methanation reaction such as the Sabatier reaction, or biological methanation, resulting in an extra energy conversion loss of 8%. The methane may then be fed into the natural gas grid. The third method uses the output gas of a wood gas generator or a biogas plant, after the biogas upgrader is mixed with the hydrogen from the electrolyzer, to upgrade the quality of the biogas.

Hydrogen

The element hydrogen can be a form of stored energy. Hydrogen can produce electricity via a hydrogen fuel cell.

At penetrations below 20% of the grid demand, renewables do not severely change the economics; but beyond about 20% of the total demand, external storage becomes important. If these sources are used to make ionic hydrogen, they can be freely expanded. A 5-year community-based pilot program using wind turbines and hydrogen generators began in 2007 in the remote community of Ramea, Newfoundland and Labrador. A similar project began in 2004 on Utsira, a small Norwegian island.

Energy losses involved in the hydrogen storage cycle come from the electrolysis of water, liquification or compression of the hydrogen and conversion to electricity.

About 50 kW·h (180 MJ) of solar energy is required to produce a kilogram of hydrogen, so the cost of the electricity is crucial. At $0.03/kWh, a common off-peak high-voltage line rate in the United States, hydrogen costs $1.50 per kilogram for the electricity, equivalent to $1.50/gallon for gasoline. Other costs include the electrolyzer plant, hydrogen compressors or liquefaction, storage and transportation.

Hydrogen can also be produced from aluminum and water by stripping aluminum's naturally-occurring aluminum oxide barrier and introducing it to water. This method is beneficial because recycled aluminum cans can be used to generate hydrogen, however systems to harness this option have not been commercially developed and are much more complex than electrolysis systems.mon methods to strip the oxide layer include caustic catalysts such as sodium hydroxide and alloys with gallium, mercury and other metals.

Underground hydrogen storage is the practice of hydrogen storage in caverns, salt domes and depleted oil and gas fields. Large quantities of gaseous hydrogen have been stored in caverns by Imperial Chemical Industries for many years without any difficulties. The European Hyunder project indicated in 2013 that storage of wind and solar energy using underground hydrogen would require 85 caverns.

Methane

Methane is the simplest hydrocarbon with the molecular formula CH4. Methane is more easily stored and transported than hydrogen. Storage and combustion infrastructure (pipelines, gasometers, power plants) are mature.

Synthetic natural gas (syngas or SNG) can be created in a multi-step process, starting with hydrogen and oxygen. Hydrogen is then reacted with carbon dioxide in a Sabatier process, producing methane and water. Methane can be stored and later used to produce electricity. The resulting water is recycled, reducing the need for water. In the electrolysis stage, oxygen is stored for methane combustion in a pure oxygen environment at an adjacent power plant, eliminating nitrogen oxides.

Methane combustion produces carbon dioxide (CO2) and water. The carbon dioxide can be recycled to boost the Sabatier process and water can be recycled for further electrolysis. Methane production, storage and combustion recycles the reaction products.

The CO2 has economic value as a component of an energy storage vector, not a cost as in carbon capture and storage.

Power to liquid

Power to liquid is similar to power to gas except that the hydrogen is converted into liquids such as methanol or ammonia. These are easier to handle than gases, and requires fewer safety precautions than hydrogen. They can be used for transportation, including aircraft, but also for industrial purposes or in the power sector.

Biofuels

Main article: Biofuel

Various biofuels such as biodiesel, vegetable oil, alcohol fuels, or biomass can replace fossil fuels. Various chemical processes can convert the carbon and hydrogen in coal, natural gas, plant and animal biomass and organic wastes into short hydrocarbons suitable as replacements for existing hydrocarbon fuels. Examples are Fischer–Tropsch diesel, methanol, dimethyl ether and syngas. This diesel source was used extensively in World War II in Germany, which faced limited access to crude oil supplies. South Africa produces most of the country's diesel from coal for similar reasons. A long term oil price above US$35/bbl may make such large scale synthetic liquid fuels economical.

Aluminum

Aluminum has been proposed as an energy store by a number of researchers. Its electrochemical equivalent (8.04 Ah/cm3) is nearly four times greater than that of lithium (2.06 Ah/cm3). Energy can be extracted from aluminum by reacting it with water to generate hydrogen. However, it must first be stripped of its natural oxide layer, a process which requires pulverization, chemical reactions with caustic substances, or alloys. The byproduct of the reaction to create hydrogen is aluminum oxide, which can be recycled into aluminum with the Hall–Héroult process, making the reaction theoretically renewable. If the Hall-Heroult Process is run using solar or wind power, aluminum could be used to store the energy produced at higher efficiency than direct solar electrolysis.

Boron, silicon, and zinc

Boron, silicon, and zinc have been proposed as energy storage solutions.

Other chemical

The organic compound norbornadiene converts to quadricyclane upon exposure to light, storing solar energy as the energy of chemical bonds. A working system has been developed in Sweden as a molecular solar thermal system.

Electrical methods

Capacitor

This mylar-film, oil-filled capacitor has very low inductance and low resistance, to provide the high-power (70 megawatts) and the very high speed (1.2 microsecond) discharges needed to operate a dye laser.

A capacitor (originally known as a 'condenser') is a passive two-terminal electrical component used to store energy electrostatically. Practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e., insulator). A capacitor can store electric energy when disconnected from its charging circuit, so it can be used like a temporary battery, or like other types of rechargeable energy storage system. Capacitors are commonly used in electronic devices to maintain power supply while batteries change. (This prevents loss of information in volatile memory.) 

Conventional capacitors provide less than 360 joules per kilogram, while a conventional alkaline battery has a density of 590 kJ/kg.

Capacitors store energy in an electrostatic field between their plates. Given a potential difference across the conductors (e.g., when a capacitor is attached across a battery), an electric field develops across the dielectric, causing positive charge (+Q) to collect on one plate and negative charge (-Q) to collect on the other plate. If a battery is attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor. However, if an accelerating or alternating voltage is applied across the leads of the capacitor, a displacement current can flow. Besides capacitor plates, charge can also be stored in a dielectric layer.

Capacitance is greater given a narrower separation between conductors and when the conductors have a larger surface area. In practice, the dielectric between the plates emits a small amount of leakage current and has an electric field strength limit, known as the breakdown voltage. However, the effect of recovery of a dielectric after a high-voltage breakdown holds promise for a new generation of self-healing capacitors. The conductors and leads introduce undesired inductance and resistance.

Research is assessing the quantum effects of nanoscale capacitors for digital quantum batteries.

Superconducting magnetics

Superconducting magnetic energy storage (SMES) systems store energy in a magnetic field created by the flow of direct current in a superconducting coil that has been cooled to a temperature below its superconducting critical temperature. A typical SMES system includes a superconducting coil, power conditioning system and refrigerator. Once the superconducting coil is charged, the current does not decay and the magnetic energy can be stored indefinitely.

The stored energy can be released to the network by discharging the coil. The associated inverter/rectifier accounts for about 2–3% energy loss in each direction. SMES loses the least amount of electricity in the energy storage process compared to other methods of storing energy. SMES systems offer round-trip efficiency greater than 95%.

Due to the energy requirements of refrigeration and the cost of superconducting wire, SMES is used for short duration storage such as improving power quality. It also has applications in grid balancing.

Applications

Mills

The classic application before the industrial revolution was the control of waterways to drive water mills for processing grain or powering machinery. Complex systems of reservoirs and dams were constructed to store and release water (and the potential energy it contained) when required.

Homes

Home energy storage is expected to become increasingly common given the growing importance of distributed generation of renewable energies (especially photovoltaics) and the important share of energy consumption in buildings.[73] To exceed a self-sufficiency of 40% in a household equipped with photovoltaics, energy storage is needed.[73] Multiple manufacturers produce rechargeable battery systems for storing energy, generally to hold surplus energy from home solar or wind generation. Today, for home energy storage, Li-ion batteries are preferable to lead-acid ones given their similar cost but much better performance.[74]

Tesla Motors produces two models of the Tesla Powerwall. One is a 10 kWh weekly cycle version for backup applications and the other is a 7 kWh version for daily cycle applications. In 2016, a limited version of the Tesla Powerpack 2 cost $398(US)/kWh to store electricity worth 12.5 cents/kWh (US average grid price) making a positive return on investment doubtful unless electricity prices are higher than 30 cents/kWh.

RoseWater Energy produces two models of the "Energy & Storage System", the HUB 120 and SB20. Both versions provide 28.8 kWh of output, enabling it to run larger houses or light commercial premises, and protecting custom installations. The system provides five key elements into one system, including providing a clean 60 Hz Sine wave, zero transfer time, industrial-grade surge protection, renewable energy grid sell-back (optional), and battery backup.

Enphase Energy announced an integrated system that allows home users to store, monitor and manage electricity. The system stores 1.2 kWh of energy and 275W/500W power output.

Storing wind or solar energy using thermal energy storage though less flexible, is considerably cheaper than batteries. A simple 52-gallon electric water heater can store roughly 12 kWh of energy for supplementing hot water or space heating.

For purely financial purposes in areas where net metering is available, home generated electricity may be sold to the grid through a grid-tie inverter without the use of batteries for storage.

Grid electricity and power stations

Renewable energy

Construction of the Salt Tanks which provide efficient thermal energy storage so that electricity can be generated after the sun goes down, and output can be scheduled to meet demand. The 280 MW Solana Generating Station is designed to provide six hours of storage. This allows the plant to generate about 38% of its rated capacity over the course of a year.
 
The 150 MW Andasol solar power station in Spain is a parabolic trough solar thermal power plant that stores energy in tanks of molten salt so that it can continue generating electricity when the sun is not shining.

The largest source and the greatest store of renewable energy is provided by hydroelectric dams. A large reservoir behind a dam can store enough water to average the annual flow of a river between dry and wet seasons. A very large reservoir can store enough water to average the flow of a river between dry and wet years. While a hydroelectric dam does not directly store energy from intermittent sources, it does balance the grid by lowering its output and retaining its water when power is generated by solar or wind. If wind or solar generation exceeds the region's hydroelectric capacity, then some additional source of energy is needed.

Many renewable energy sources (notably solar and wind) produce variable power. Storage systems can level out the imbalances between supply and demand that this causes. Electricity must be used as it is generated or converted immediately into storable forms.

The main method of electrical grid storage is pumped-storage hydroelectricity. Areas of the world such as Norway, Wales, Japan and the US have used elevated geographic features for reservoirs, using electrically powered pumps to fill them. When needed, the water passes through generators and converts the gravitational potential of the falling water into electricity. Pumped storage in Norway, which gets almost all its electricity from hydro, has currently a capacity of 1.4 GW but since the total installed capacity is nearly 32 GW and 75% of that is regulable, it can be expanded significantly.

Some forms of storage that produce electricity include pumped-storage hydroelectric dams, rechargeable batteries, thermal storage including molten salts which can efficiently store and release very large quantities of heat energy, and compressed air energy storage, flywheels, cryogenic systems and superconducting magnetic coils.

Surplus power can also be converted into methane (sabatier process) with stockage in the natural gas network.

In 2011, the Bonneville Power Administration in Northwestern United States created an experimental program to absorb excess wind and hydro power generated at night or during stormy periods that are accompanied by high winds. Under central control, home appliances absorb surplus energy by heating ceramic bricks in special space heaters to hundreds of degrees and by boosting the temperature of modified hot water heater tanks. After charging, the appliances provide home heating and hot water as needed. The experimental system was created as a result of a severe 2010 storm that overproduced renewable energy to the extent that all conventional power sources were shut down, or in the case of a nuclear power plant, reduced to its lowest possible operating level, leaving a large area running almost completely on renewable energy.

Another advanced method used at the former Solar Two project in the United States and the Solar Tres Power Tower in Spain uses molten salt to store thermal energy captured from the sun and then convert it and dispatch it as electrical power. The system pumps molten salt through a tower or other special conduits to be heated by the sun. Insulated tanks store the solution. Electricity is produced by turning water to steam that is fed to turbines.

Since the early 21st century batteries have been applied to utility scale load-leveling and frequency regulation capabilities.

In vehicle-to-grid storage, electric vehicles that are plugged into the energy grid can deliver stored electrical energy from their batteries into the grid when needed.

Air conditioning

Thermal energy storage (TES) can be used for air conditioning. It is most widely used for cooling single large buildings and/or groups of smaller buildings. Commercial air conditioning systems are the biggest contributors to peak electrical loads. In 2009, thermal storage was used in over 3,300 buildings in over 35 countries. It works by chilling material at night and using the chilled material for cooling during the hotter daytime periods.

The most popular technique is ice storage, which requires less space than water and is cheaper than fuel cells or flywheels. In this application, a standard chiller runs at night to produce an ice pile. Water circulates through the pile during the day to chill water that would normally be the chiller's daytime output.

A partial storage system minimizes capital investment by running the chillers nearly 24 hours a day. At night, they produce ice for storage and during the day they chill water. Water circulating through the melting ice augments the production of chilled water. Such a system makes ice for 16 to 18 hours a day and melts ice for six hours a day. Capital expenditures are reduced because the chillers can be just 40% - 50% of the size needed for a conventional, no-storage design. Storage sufficient to store half a day's available heat is usually adequate.

A full storage system shuts off the chillers during peak load hours. Capital costs are higher, as such a system requires larger chillers and a larger ice storage system.

This ice is produced when electrical utility rates are lower. Off-peak cooling systems can lower energy costs. The U.S. Green Building Council has developed the Leadership in Energy and Environmental Design (LEED) program to encourage the design of reduced-environmental impact buildings. Off-peak cooling may help toward LEED Certification.

Thermal storage for heating is less common than for cooling. An example of thermal storage is storing solar heat to be used for heating at night.

Latent heat can also be stored in technical phase change materials (PCMs). These can be encapsulated in wall and ceiling panels, to moderate room temperatures.

Transport

Liquid hydrocarbon fuels are the most commonly used forms of energy storage for use in transportation, followed by a growing use of Battery Electric Vehicles and Hybrid Electric Vehicles. Other energy carriers such as hydrogen can be used to avoid producing greenhouse gases.

Public transport systems like trams and trolleybuses require electricity, but due to their variability in movement, a steady supply of electricity via renewable energy is challenging. Photovoltaic systems installed on the roofs of buildings can be used to power public transportation systems during periods in which there is increased demand for electricity and access to other forms of energy are not readily available.

Electronics

Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems they stabilize voltage and power flow.

Use cases

The United States Department of Energy International Energy Storage Database (IESDB), is a free-access database of energy storage projects and policies funded by the United States Department of Energy Office of Electricity and Sandia National Labs.

Capacity

Storage capacity is the amount of energy extracted from a power plant energy storage system; usually measured in joules or kilowatt-hours and their multiples, it may be given in number of hours of electricity production at power plant nameplate capacity; when storage is of primary type (i.e., thermal or pumped-water), output is sourced only with the power plant embedded storage system.

Economics

The economics of energy storage strictly depends on the reserve service requested, and several uncertainty factors affect the profitability of energy storage. Therefore, not every storage method is technically and economically suitable for the storage of several MWh, and the optimal size of the energy storage is market and location dependent.

Moreover, ESS are affected by several risks, e.g.:

1) Techno-economic risks, which are related to the specific technology;

2) Market risks, which are the factors that affect the electricity supply system;

3) Regulation and policy risks.

Therefore, traditional techniques based on deterministic Discounted Cash Flow (DCF) for the investment appraisal are not fully adequate to evaluate these risks and uncertainties and the investor's flexibility to deal with them. Hence, the literature recommends to assess the value of risks and uncertainties through the Real Option Analysis (ROA), which is a valuable method in uncertain contexts.

The economic valuation of large-scale applications (including pumped hydro storage and compressed air) considers benefits including: curtailment avoidance, grid congestion avoidance, price arbitrage and carbon-free energy delivery. In one technical assessment by the Carnegie Mellon Electricity Industry Centre, economic goals could be met using batteries if their capital cost was $30 to $50 per kilowatt-hour.

A metric of energy efficiency of storage is energy storage on energy invested (ESOI), which is the amount of energy that can be stored by a technology, divided by the amount of energy required to build that technology. The higher the ESOI, the better the storage technology is energetically. For lithium-ion batteries this is around 10, and for lead acid batteries it is about 2. Other forms of storage such as pumped hydroelectric storage generally have higher ESOI, such as 210.

Research

Germany

In 2013, the German Federal government allocated €200M (approximately US$270M) for research, and another €50M to subsidize battery storage in residential rooftop solar panels, according to a representative of the German Energy Storage Association.

Siemens AG commissioned a production-research plant to open in 2015 at the Zentrum für Sonnenenergie und Wasserstoff (ZSW, the German Center for Solar Energy and Hydrogen Research in the State of Baden-Württemberg), a university/industry collaboration in Stuttgart, Ulm and Widderstall, staffed by approximately 350 scientists, researchers, engineers, and technicians. The plant develops new near-production manufacturing materials and processes (NPMM&P) using a computerized Supervisory Control and Data Acquisition (SCADA) system. It aims to enable the expansion of rechargeable battery production with increased quality and lower cost.

United States

In 2014, research and test centers opened to evaluate energy storage technologies. Among them was the Advanced Systems Test Laboratory at the University of Wisconsin at Madison in Wisconsin State, which partnered with battery manufacturer Johnson Controls. The laboratory was created as part of the university's newly opened Wisconsin Energy Institute. Their goals include the evaluation of state-of-the-art and next generation electric vehicle batteries, including their use as grid supplements.

The State of New York unveiled its New York Battery and Energy Storage Technology (NY-BEST) Test and Commercialization Center at Eastman Business Park in Rochester, New York, at a cost of $23 million for its almost 1,700 m2 laboratory. The center includes the Center for Future Energy Systems, a collaboration between Cornell University of Ithaca, New York and the Rensselaer Polytechnic Institute in Troy, New York. NY-BEST tests, validates and independently certifies diverse forms of energy storage intended for commercial use.

On September 27, 2017, Senators Al Franken of Minnesota and Martin Heinrich of New Mexico introduced Advancing Grid Storage Act (AGSA), which would devote more than $1 billion in research, technical assistance and grants to encourage energy storage in the United States.

United Kingdom

In the United Kingdom, some 14 industry and government agencies allied with seven British universities in May 2014 to create the SUPERGEN Energy Storage Hub in order to assist in the coordination of energy storage technology research and development.

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Friday, October 16, 2020

Identity politics

From Wikipedia, the free encyclopedia

Identity politics is a term that describes a political approach wherein people of a particular religion, race, social background, class or other identifying factor form exclusive socio-political alliances, moving away from broad-based, coalitional politics to support and follow political movements that share a particular identifying quality with them. Its aim is to support and center the concerns, agendas, and projects of particular groups, in accord with specific social and political changes.

The term was coined by the Combahee River Collective in 1977. It took on widespread usage in the early 1980s, and in the ensuing decades has been employed in myriad cases with radically different connotations dependent upon the term's context. It has gained currency with the emergence of social activism, manifesting in various dialogues within the feminist, American civil rights, and LGBT movements, as well as multiple nationalist and postcolonial organizations.

In academic usage, the term identity politics refers to a wide range of political activities and theoretical analyses rooted in experiences of injustice shared by different, often excluded social groups. In this context, identity politics aims to reclaim greater self-determination and political freedom for marginalized peoples through understanding particular paradigms and lifestyle factors, and challenging externally imposed characterizations and limitations, instead of organizing solely around status quo belief systems or traditional party affiliations. Identity is used "as a tool to frame political claims, promote political ideologies, or stimulate and orient social and political action, usually in a larger context of inequality or injustice and with the aim of asserting group distinctiveness and belonging and gaining power and recognition."

Contemporary applications of identity politics describe peoples of specific race, ethnicity, sex, gender identity, sexual orientation, age, economic class, disability status, education, religion, language, profession, political party, veteran status, and geographic location. These identity labels are not mutually exclusive but are, in many cases, compounded into one when describing hyper-specific groups (a concept known as intersectionality)—for example: African-American, homosexual women constitutes a particular hyper-specific identity class.

History

The term identity politics may have been used in political discourse since at least the 1970s. The first known written appearance of the term is found in the April 1977 statement of the Black feminist group, Combahee River Collective, which was originally printed in 1979's Capitalist Patriarchy and the Case for Socialist Feminism, later in Home Girls: A Black Feminist Anthology, ed. by Barbara Smith. She and the Combahee River Collective, of which she was a founding member, have been credited with coining the term. In their terminal statement, they said:

[A]s children we realized that we were different from boys and that we were treated different—for example, when we were told in the same breath to be quiet both for the sake of being 'ladylike' and to make us less objectionable in the eyes of white people. In the process of consciousness-raising, actually life-sharing, we began to recognize the commonality of our experiences and, from the sharing and growing consciousness, to build a politics that will change our lives and inevitably end our oppression....We realize that the only people who care enough about us to work consistently for our liberation are us. Our politics evolve from a healthy love for ourselves, our sisters and our community which allows us to continue our struggle and work. This focusing upon our own oppression is embodied in the concept of identity politics. We believe that the most profound and potentially most radical politics come directly out of our own identity, as opposed to working to end somebody else's oppression.

— Combahee River Collective, "The Combahee River Collective Statement"

Identity politics, as a mode of categorizing, are closely connected to the ascription that some social groups are oppressed (such as women, ethnic minorities, and sexual minorities); that is, the claim that individuals belonging to those groups are, by virtue of their identity, more vulnerable to forms of oppression such as cultural imperialism, violence, exploitation of labour, marginalization, or subjugation. Therefore, these lines of social difference can be seen as ways to gain empowerment or avenues through which to work towards a more equal society. In the United States, identity politics is usually ascribed to these oppressed minority groups who are fighting discrimination. In Canada and Spain, identity politics has been used to describe separatist movements; in Africa, Asia, and eastern Europe, it has described violent nationalist and ethnic conflicts. Overall, in Europe, identity politics are exclusionary and based on the idea that the silent majority needs to be protected from globalization and immigration.

Some groups have combined identity politics with Marxist social class analysis and class consciousness—the most notable example being the Black Panther Party—but this is not necessarily characteristic of the form. Another example is the group MOVE, which mixed Black nationalism with anarcho-primitivism (a radical form of green politics based on the idea that civilization is an instrument of oppression, advocating the return to a hunter gatherer society). Identity politics can be left-wing or right-wing, with examples of the latter being Ulster Loyalism, Islamism and Christian Identity movements, and the former being queer nationalism and black nationalism.

During the 1980s, the politics of identity became very prominent and it was linked to a new wave of social movement activism.

Debates and criticism

Nature of the movement

The term identity politics has been applied retroactively to varying movements that long predate its coinage. Historian Arthur Schlesinger Jr. discussed identity politics extensively in his 1991 book The Disuniting of America. Schlesinger, a strong supporter of liberal conceptions of civil rights, argues that a liberal democracy requires a common basis for culture and society to function. Rather than seeing civil society as already fractured along lines of power and powerlessness (according to race, ethnicity, sexuality, etc.), Schlesinger suggests that basing politics on group marginalization is itself what fractures the civil polity, and that identity politics therefore works against creating real opportunities for ending marginalization. Schlesinger believes that:

movements for civil rights should aim toward full acceptance and integration of marginalized groups into the mainstream culture, rather than … perpetuating that marginalization through affirmations of difference.

Similarly Brendan O'Neill has suggested that identity politics causes (rather than simply recognizing and acting on) political schisms along lines of social identity. Thus, he contrasts the politics of gay liberation and identity politics by saying:

[Peter] Tatchell also had, back in the day, … a commitment to the politics of liberation, which encouraged gays to come out and live and engage. Now, we have the politics of identity, which invites people to stay in, to look inward, to obsess over the body and the self, to surround themselves with a moral forcefield to protect their worldview—which has nothing to do with the world—from any questioning."

In these and other ways, a political perspective oriented to one's own well being can be recast as causing the divisions that it insists upon making visible.

In this same vein, author Owen Jones argues that identity politics often marginalize the working class, saying that:

In the 1950s and 1960s, left-wing intellectuals who were both inspired and informed by a powerful labour movement wrote hundreds of books and articles on working-class issues. Such work would help shape the views of politicians at the very top of the Labour Party. Today, progressive intellectuals are far more interested in issues of identity. ... Of course, the struggles for the emancipation of women, gays, and ethnic minorities are exceptionally important causes. New Labour has co-opted them, passing genuinely progressive legislation on gay equality and women's rights, for example. But it is an agenda that has happily co-existed with the sidelining of the working class in politics, allowing New Labour to protect its radical flank while pressing ahead with Thatcherite policies.

— Owen Jones, Chavs: The Demonization of the Working Class

LGBT issues

The gay liberation movement of the late 1960s through the mid-1980s urged lesbians and gay men to engage in radical direct action, and to counter societal shame with gay pride. In the feminist spirit of the personal being political, the most basic form of activism was an emphasis on coming out to family, friends and colleagues, and living life as an openly lesbian or gay person. While the 1970s were the peak of "gay liberation" in New York City and other urban areas in the United States, "gay liberation" was the term still used instead of "gay pride" in more oppressive areas into the mid-1980s, with some organizations opting for the more inclusive, "lesbian and gay liberation". While women and transgender activists had lobbied for more inclusive names from the beginning of the movement, the initialism LGBT, or "Queer" as a counterculture shorthand for LGBT, did not gain much acceptance as an umbrella term until much later in the 1980s, and in some areas not until the '90s or even '00s. During this period in the United States, identity politics were largely seen in these communities in the definitions espoused by writers such as self-identified, "black, dyke, feminist, poet, mother" Audre Lorde's view, that lived experience matters, defines us, and is the only thing that grants authority to speak on these topics; that, "If I didn't define myself for myself, I would be crunched into other people's fantasies for me and eaten alive."

By the 2000s, in some areas of postmodern queer studies (notably those around gender) the idea of "identity politics" began to shift away from that of naming and claiming lived experience, and authority arising from lived experience, to one emphasizing choice and performance. Some who draw on the work of authors like Judith Butler particularly stress this concept of remaking and unmaking performative identities. Writers in the field of Queer theory have at times taken this to the extent as to now argue that "queer", despite generations of specific use to describe a "non-heterosexual" sexual orientation, no longer needs to refer to any specific sexual orientation at all; that it is now only about "disrupting the mainstream", with author David M. Halperin arguing that straight people may now also self-identify as "queer". However, many LGBT people believe this concept of "queer heterosexuality" is an oxymoron and offensive form of cultural appropriation which not only robs gays and lesbians of their identities, but makes invisible and irrelevant the actual, lived experience of oppression that causes them to be marginalized in the first place. "It desexualizes identity, when the issue is precisely about a sexual identity."

Some supporters of identity politics take stances based on Gayatri Chakravorty Spivak's work (namely, "Can the Subaltern Speak?") and have described some forms of identity politics as strategic essentialism, a form which has sought to work with hegemonic discourses to reform the understanding of "universal" goals.

Critiques and criticisms of identity politics

The Industrial Workers of the World poster "Pyramid of Capitalist System" (1911)

Critics argue that groups based on a particular shared identity (e.g. race, or gender identity) can divert energy and attention from more fundamental issues, similar to the history of divide and rule strategies. Chris Hedges has criticized identity politics as one of the factors making up a form of "corporate capitalism" that only masquerades as a political platform, and which he believes "will never halt the rising social inequality, unchecked militarism, evisceration of civil liberties and omnipotence of the organs of security and surveillance." Sociologist Charles Derber asserts that the American left is "largely an identity-politics party" and that it "offers no broad critique of the political economy of capitalism. It focuses on reforms for Blacks and women and so forth. But it doesn’t offer a contextual analysis within capitalism." Both he and David North of the Socialist Equality Party posit that these fragmented and isolated identity movements which permeate the left have allowed for a far-right resurgence.

Critiques of identity politics have also been expressed on other grounds by writers such as Eric Hobsbawm, Todd Gitlin, Michael Tomasky, Richard Rorty, Michael Parenti, Jodi Dean, and Sean Wilentz.

Hobsbawm criticized nationalisms and the principle of national self-determination adopted in many countries after World War I, since national governments are often merely an expression of a ruling class or power, and their proliferation was a source of the wars of the 20th century. Hence, Hobsbawm argues that identity politics, such as queer nationalism, Islamism, Cornish nationalism or Ulster loyalism are just other versions of bourgeois nationalism. The view that identity politics (rooted in challenging racism, sexism, and the like) obscures class inequality is widespread in the United States and other Western nations. This framing ignores how class-based politics are identity politics themselves, according to Jeff Sparrow.

Intersectional critiques

In her journal article Mapping the Margins: Intersectionality, Identity Politics and Violence against Women of Color, Kimberle Crenshaw treats identity politics as a process that brings people together based on a shared aspect of their identity. Crenshaw applauds identity politics for bringing African Americans (and other non-white people), gays and lesbians, and other oppressed groups together in community and progress. But she critiques it because "it frequently conflates or ignores intragroup differences." Crenshaw argues that for Black women, at least two aspects of their identity are the subject of oppression: their race and their sex. Thus, although identity politics are useful, we must be aware of the role of intersectionality. Nira Yuval-Davis supports Crenshaw's critiques in Intersectionality and Feminist Politics and explains that "Identities are individual and collective narratives that answer the question 'who am/are I/we?" 

In Mapping the Margins, Crenshaw illustrates her point using the Clarence Thomas/Anita Hill controversy. Anita Hill accused US Supreme Court Justice nominee Clarence Thomas of sexual harassment; Thomas would be the second African American judge on the Supreme Court. Crenshaw argues that Hill was then deemed anti-Black in the movement against racism, and although she came forward on the feminist issue of sexual harassment, she was excluded because when considering feminism, it is the narrative of white middle-class women that prevails. Crenshaw concludes that acknowledging intersecting categories when groups unite on the basis of identity politics is better than ignoring categories altogether.

Examples

A Le Monde/IFOP poll in January 2011 conducted in France and Germany found that a majority felt Muslims are "scattered improperly"; an analyst for IFOP said the results indicated something "beyond linking immigration with security or immigration with unemployment, to linking Islam with a threat to identity".

Racial and ethnocultural

Ethnic and racial identity politics are commonly referenced in popular culture, and are increasingly analyzed in media and social commentary as an interconnected part of politics and society. Both a majority and minority group phenomenon, racial identity politics can develop as a reaction to the historical legacy of race-based oppression of a people, as well as a general group identity issue:

Racial identity politics utilizes racial consciousness - or the group's collective memory and experiences - as the essential framework for interpreting the actions and interests of all other social groups.

Carol M. Swain has argued that non-white ethnic pride and an "emphasis on racial identity politics" is fomenting the rise of white nationalism. Anthropologist Michael Messner has suggested that the Million Man March was an example of racial identity politics in the United States.

Arab identity politics

Arab identity politics concerns the identity-based politics derived from the racial or ethnocultural consciousness of Arab people. In the regionalism of the Middle East, it has particular meaning in relation to the national and cultural identities of non-Arab countries, such as Turkey, Iran and North African countries. In their 2010 Being Arab: Arabism and the Politics of Recognition, academics Christopher Wise and Paul James challenged the view that, in the post-Afghanistan and Iraq invasion era, Arab identity-driven politics were ending. Refuting the view that had "drawn many analysts to conclude that the era of Arab identity politics has passed", Wise and James examined its development as a viable alternative to Islamic fundamentalism in the Arab world.

According to Marc Lynch, the post-Arab Spring era has seen increasing Arab identity politics, which is "marked by state-state rivalries as well as state-society conflicts". Lynch believes this is creating a new Arab Cold War, no longer characterized by Sunni-Shia sectarian divides but by a reemergent Arab identity in the region. Najla Said has explored her lifelong experience with Arab identity politics in her book Looking for Palestine.

Māori identity politics

Due to somewhat competing tribe-based versus pan-Māori concepts, there is both an internal and external utilization of Māori identity politics in New Zealand. Projected outwards, Māori identity politics has been a disrupting force in the politics of New Zealand and post-colonial conceptions of nationhood. Its development has also been explored as causing parallel ethnic identity developments in non-Māori populations. Academic Alison Jones, in her co-written Tuai: A Traveller in Two Worlds, suggests that a form of Māori identity politics, directly oppositional to Pākehā (white New Zealanders), has helped provide a "basis for internal collaboration and a politics of strength".

A 2009, Ministry of Social Development journal identified Māori identity politics, and societal reactions to it, as the most prominent factor behind significant changes in self-identification from the 2006 New Zealand census.

White identity politics

White identity politics concerns the manifestation of the ethnocultural identity of white people in various national political settings such as the United States or Australia.

In 1998, political scientists Jeffrey Kaplan and Leonard Weinberg predicted that, by the late 20th-century, a "Euro-American radical right" would promote a trans-national white identity politics, which would invoke populist grievance narratives and encourage hostility against non-white peoples and multiculturalism. In the United States, mainstream news has identified Donald Trump's presidency as a signal of increasing and widespread utilization of white identity politics within the Republican Party and political landscape. Political journalists such as Michael Scherer and David Smith have reported on its development since the mid-2010s.

Ron Brownstein believes that President Trump uses "White Identity Politics" to bolster his base and that this will ultimately limit his ability to reach out to non-White American voters for the 2020 United States presidential election. A four-year Reuters and Ipsos analysis concurred that "Trump's brand of white identity politics may be less effective in the 2020 election campaign." Alternatively, examining the same poll, David Smith has written that "Trump’s embrace of white identity politics may work to his advantage" in 2020. During the Democratic primaries, presidential candidate Pete Buttigieg publicly warned that the president and his administration were using white identity politics, which he said was the most divisive form of identity politics. Columnist Reihan Salam writes that he is not convinced that Trump uses "white identity politics" given the fact that he still has significant support from liberal and moderate Republicans – who are more favorable toward immigration and the legalization of undocumented immigrants – but believes that it could become a bigger issue as whites become a minority and assert their rights like other minority groups. Salam also states that an increase in "white identity" politics is far from certain given the very high rates of intermarriage and the historical example of the once Anglo-Protestant cultural majority embracing a more inclusive white cultural majority which included Jews, Italians, Poles, Arabs, and Irish.

Columnist Ross Douthat has argued that it has been important to American politics since the Richard Nixon-era of the Republican Party, and historian Nell Irvin Painter has analyzed Eric Kaufmann's thesis that the phenomenon is caused by immigration-derived racial diversity, which reduces the white majority, and an "anti-majority adversary culture". Writing in Vox, political commentator Ezra Klein believes that demographic change has fueled the emergence of white identity politics.

Gender

Gender identity politics is an approach that views politics, both in practice and as an academic discipline, as having a gendered nature and that gender is an identity that influences how people think.

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Reliability of Wikipedia

From Wikipedia, the free encyclopedia
 
Elaine Herzberg
Born
Elaine Marie Wood

August 2, 1968
Phoenix, Arizona, U.S.
DiedMarch 18, 2018 (aged 49)
Tempe, Arizona, U.S.
Burial placePhoenix, Arizona
NationalityAmerican
EducationApache Junction High School, Apache Junction, Arizona
Known forFirst pedestrian to be killed by a self-driving car
Spouse(s)Mike Herzberg (until his death); Rolf Erich Ziemann (until Elaine's death)

The death of Elaine Herzberg (August 2, 1968 – March 18, 2018) was the first recorded case of a pedestrian fatality involving a self-driving (autonomous) car, after a collision that occurred late in the evening of March 18, 2018. Herzberg was pushing a bicycle across a four-lane road in Tempe, Arizona, United States, when she was struck by an Uber test vehicle, which was operating in self-drive mode with a human safety backup driver sitting in the driving seat. Herzberg was taken to the local hospital where she died of her injuries.

Following the fatal incident, Uber suspended testing of self-driving vehicles in Arizona, where such testing had been sanctioned since August 2016. Uber chose not to renew its permit for testing self-driving vehicles in California when it expired at the end of March 2018.

Herzberg was the first pedestrian killed by a self-driving car; a driver had been killed by a semi-autonomous car almost two years earlier. A Washington Post reporter compared Herzberg's fate with that of Bridget Driscoll who, in the United Kingdom in 1896, was the first pedestrian to be killed by an automobile. The Arizona incident has magnified the importance of collision avoidance systems for self-driving vehicles.

Collision summary

Herzberg was crossing Mill Avenue (North) from west to east, approximately 360 feet (110 m) south of the intersection with Curry Road, outside the designated pedestrian crosswalk, close to the Red Mountain Freeway. She was pushing a bicycle laden with shopping bags, and had crossed at least two lanes of traffic when she was struck at approximately 9:58 pm MST (UTC−07:00) by a prototype Uber self-driving car based on a Volvo XC90, which was traveling north on Mill. The vehicle had been operating in autonomous mode since 9:39 pm, nineteen minutes before it struck and killed Herzberg. The car's human safety backup driver, Ms. Rafaela Vasquez, did not intervene in time to prevent the collision. Vehicle telemetry obtained after the crash showed that the human operator responded by moving the steering wheel less than a second before impact, and she engaged the brakes less than a second after impact.

Cause investigation

The self-driving Uber Volvo XC90 involved in the collision, with damage on the right front side

The county district attorney's office recused itself from the investigation, due to a prior joint partnership with Uber promoting their services as an alternative to driving under the influence of alcohol.

Accounts of the crash have been conflicting in terms of the speed limit at the place of the accident. According to Tempe police the car was traveling in a 35 mph (56 km/h) zone, but this is contradicted by a posted speed limit of 45 mph (72 km/h).  Some later points of focus by federal investigators have indicated that the absolute maximum speed permitted by law may not be material in the nocturnal crash.

The National Transportation Safety Board (NTSB) sent a team of federal investigators to gather data from vehicle instruments, and to examine vehicle condition along with the actions taken by the safety driver. Their preliminary findings were substantiated by multiple event data recorders and proved the vehicle was traveling 43 miles per hour (69 km/h) when Herzberg was first detected 6 seconds (378 feet (115 m)) before impact; during 4 seconds the self driving system did not infer that emergency braking was needed. A vehicle traveling 43 mph (69 km/h) can generally stop within 89 feet (27 m) once the brakes are applied. Because the machine needed to be 1.3 seconds (82 feet (25 m)) away prior to discerning that emergency braking was required, whereas at least that much distance was required to stop, it was exceeding its assured clear distance ahead. The system failed to behave properly. A total stopping distance of 76 feet itself would imply a safe speed under 25 mph (40 km/h). Human intervention was still legally required. Computer perception–reaction time would have been a speed limiting factor had the technology been superior to humans in ambiguous situations; however, the nascent computerized braking technology was disabled the day of the crash, and the machine's apparent 4-second perception–reaction (alarm) time allowed the car to travel 250 feet (76 m). Video released by the police on March 21 showed the safety driver was not watching the road moments before the vehicle struck Herzberg.

Environment

Vicinity of Mill Avenue (running north–south) and Curry/Washington (east–west) in Tempe, Arizona

Tempe Police Chief Sylvia Moir was quoted stating the collision was "unavoidable" based on the initial police investigation, which included a review of the video captured by an onboard camera. Moir faulted Herzberg for crossing the road in an unsafe manner: "It is dangerous to cross roadways in the evening hour when well-illuminated, managed crosswalks are available." According to Uber, safety drivers were trained to keep their hands very close to the wheel all the time while driving the vehicle so they were ready to quickly take control if necessary.

The driver said it was like a flash, the person walked out in front of them. His [sic] first alert to the collision was the sound of the collision. [...] it's very clear it would have been difficult to avoid this collision in any kind of mode (autonomous or human-driven) based on how she came from the shadows right into the roadway.

— Chief Sylvia Moir, Tempe Police, San Francisco Chronicle interview, March 19, 2018
Aerial photograph of the area where the collision occurred, facing approximately north. Mill Avenue runs from the top left corner to the bottom right corner (north–south), and the ornamental brick-lined median is just south of the intersection with Curry/Washington.

Tempe police released video on March 21 showing footage recorded by two onboard cameras: one forward-looking, and one capturing the safety driver's actions. The forward-facing video shows that the self-driving car was traveling in the far right lane when it struck Herzberg. The driver-facing video shows the safety driver was looking down prior to the collision. The Uber operator is responsible for intervening and taking manual control when necessary as well as for monitoring diagnostic messages, which are displayed on a screen in the center console. In an interview conducted after the crash with NTSB, the driver stated she was monitoring the center stack at the time of the collision.

After the Uber video was released, journalist Carolyn Said noted the police explanation of Herzberg's path meant she had already crossed two lanes of traffic before she was struck by the autonomous vehicle. The Marquee Theatre and Tempe Town Lake are west of Mill Avenue, and pedestrians commonly cross mid-street without detouring north to the crosswalk at Curry. According to reporting by the Phoenix New Times, Mill Avenue contains what appears to be a brick-paved path in the median between the northbound and southbound lanes; however, posted signs prohibit pedestrians from crossing in that location. When the second of the Mill Avenue bridges over the town lake was added in 1994 for northbound traffic, the X-shaped crossover in the median was installed to accommodate the potential closing of one of the two road bridges. The purpose of this brick-paved structure is purely to divert cars from one side to the other if a bridge is closed to traffic, and although it may look like a crosswalk for pedestrians, it is in fact a temporary roadway with vertical curbs and warning signs.

Software issues

Michael Ramsey, a self-driving car expert with Gartner, characterized the video as showing "a complete failure of the system to recognize an obviously seen person who is visible for quite some distance in the frame. Uber has some serious explaining to do about why this person wasn't seen and why the system didn't engage."

James Arrowood, a lawyer specializing in driverless cars in Arizona, incorrectly speculated the software may have decided to proceed after assuming that Herzberg would yield the right of way. Arizona law (ARS 28-793) states that pedestrians crossing the street outside a crosswalk shall yield to cars. Per Arrowood, "The computer makes a decision. It says, 'Hey, there is this object moving 10 or 15 feet to left of me, do I move or not?' It (could be) programmed, I have a right of way, on the assumption that whatever is moving will yield the right of way." The NTSB preliminary report, however, noted that the software did order the car to brake 1.3 seconds before the collision.

A video shot from the vehicle's dashboard camera showed the safety driver looking down, away from the road. It also appeared that the driver's hands were not hovering above the steering wheel, which is what drivers are instructed to do so they can quickly retake control of the car. Uber moved from two employees in every car to one. The paired employees had been splitting duties: one ready to take over if the autonomous system failed, and another to keep an eye on what the computers were detecting. The second person was responsible for keeping track of system performance as well as labeling data on a laptop computer. Mr. Kallman, the Uber spokesman, said the second person was in the car for purely data related tasks, not safety. When Uber moved to a single operator, some employees expressed safety concerns to managers, according to the two people familiar with Uber's operations. They were worried that going solo would make it harder to remain alert during hours of monotonous driving.

Playback of self-driving system data at 1.3 seconds before impact. Distances shown in meters.

The recorded telemetry showed the system had detected Herzberg six seconds before the crash, and classified her first as an unknown object, then as a vehicle, and finally as a bicycle, each of which had a different predicted path according to the autonomy logic. 1.3 seconds prior to the impact, the system determined that emergency braking was required, which is normally performed by the vehicle operator. However, the system was not designed to alert the operator, and did not make an emergency stop on its own accord, as "emergency braking maneuvers are not enabled while the vehicle is under computer control, to reduce the potential for erratic vehicle behavior", according to NTSB.

Sensor issues

Brad Templeton, who provided consulting for autonomous driving competitor Waymo, noted the car was equipped with advanced sensors, including radar and LiDAR, which would not have been affected by the darkness. Templeton stated "I know the [sensor] technology is better than that, so I do feel that it must be Uber's failure." Arrowood also recognized potential sensor issues: "Really what we are going to ask is, at what point should or could those sensors recognize the movement off to the left. Presumably she was somewhere in the darkness."

In a press event conducted by Uber in Tempe in 2017, safety drivers touted the sensor technology, saying they were effective at anticipating jaywalkers, especially in the darkness, stopping the autonomous vehicles before the safety driver can even see pedestrians. However, manual intervention by the safety drivers was required to avoid a collision with another vehicle on at least one instance with a reporter from The Arizona Republic riding along.

Uber announced they would replace their Ford Fusion-based self-driving fleet with cars based on the Volvo XC90 in August 2016; the XC90s sold to Uber would be prepared to receive Uber's vehicle control hardware and software, but would not include any of Volvo's own advanced driver-assistance systems. Uber characterized the sensor suite attached to the Fusion as the "desktop" model, and the one attached to the XC90 as the "laptop", hoping to develop the "smartphone" soon. According to Uber, the suite for the XC90 was developed in approximately four months. The XC90 as modified by Uber included a single roof-mounted LiDAR sensor and 10 radar sensors, providing 360° coverage around the vehicle. In comparison, the Fusion had seven LiDAR sensors (including one mounted on the roof) and seven radar sensors. According to Velodyne, the supplier of Uber's LiDAR, the single roof-mounted LiDAR sensor has a narrow vertical range that prevents it from detecting obstacles low to the ground, creating a blind spot around the vehicle. Marta Hall, the president of Velodyne commented "If you're going to avoid pedestrians, you're going to need to have a side lidar to see those pedestrians and avoid them, especially at night." However, the augmented radar sensor suite would be able to detect obstacles in the LiDAR blind spot.

Distraction

On Thursday, June 21, the Tempe Police Department released a detailed report along with media captured after the collision, including an audio recording of the 911 call made by the safety driver, Rafaela Vasquez and an initial on-scene interview with a responding officer, captured by body worn video. After the crash, police obtained search warrants for Vasquez's cellphones as well as records from the video streaming services Netflix, YouTube, and Hulu. The investigation concluded that because the data showed she was streaming The Voice over Hulu at the time of the collision, and the driver-facing camera in the Volvo showed "her face appears to react and show a smirk or laugh at various points during the time she is looking down", Vasquez may have been distracted from her primary job of monitoring road and vehicle conditions. Tempe police concluded the crash was "entirely avoidable" and faulted Vasquez for her "disregard for assigned job function to intervene in a hazardous situation".

Records indicate that streaming began at 9:16 pm and ended at 9:59 pm. Based on an examination of the video captured by the driver-facing camera, Vasquez was looking down toward her right knee 166 times for a total of 6 minutes, 47 seconds during the 21 minutes, 48 seconds preceding the crash. Just prior to the crash, Vasquez was looking at her lap for 5.3 seconds; she looked up half a second before the impact. Vasquez stated in her post-crash interview with the NTSB that she had been monitoring system messages on the center console, and that she did not use either one of her cell phones until she called 911. According to an unnamed Uber source, safety drivers are not responsible for monitoring diagnostic messages. Vasquez also told responding police officers she kept her hands near the steering wheel in preparation to take control if required, which contradicted the driver-facing video, which did not show her hands near the wheel. Police concluded that given the same conditions, Herzberg would have been visible to 85% of motorists at a distance of 143 feet (44 m), 5.7 seconds before the car struck Herzberg. According to the police report, Vasquez should have been able to apply the brakes at least 0.57 seconds sooner, which would have provided Herzberg sufficient time to pass safely in front of the car.

The police report was turned over to the Yavapai County Attorney's Office for review of possible manslaughter charges. The Maricopa County Attorney's Office recused itself from prosecution over a potential conflict of interest, as it had earlier participated with Uber in a March 2016 campaign against drunk driving. On March 4, 2019 Yavapai County Attorney released a letter indicating there is "no basis for criminal liability" against Uber Corporation; that potential charges against the driver should be further investigated by Maricopa County Attorney; and that the Tempe Police Department should analyze the case to gather additional evidence.

Other factors

According to the preliminary report of the collision released by the NTSB, Herzberg had tested positive for methamphetamine and marijuana in a toxicology test carried out after the collision. Residual toxicology itself does not establish if or when she was under their influence, and hence an actual factor. Inhibited faculties can hypothetically factor into one's relative ability for last-minute self-preservation. However, her mere presence on the roadway far in the distance ahead of the car was the factor which invoked the machine's duty to brake; the common legal duty to avoid her and other objects being general and preexisting.

On May 24, NTSB released a preliminary incident report, the news release saying that Herzberg "was dressed in dark clothing, did not look in the direction of the vehicle... crossed... in a section not directly illuminated by lighting... entered the roadway from a brick median, where signs...warn pedestrians to use a crosswalk... 360 feet north." Six seconds before impact, the vehicle was traveling 43 mph (69 km/h), and the system identified the woman and bicycle as an unknown object, next as a vehicle, then as a bicycle. At 1.3 seconds before hitting the pedestrian and her bike, the system flagged the need for emergency braking, but it failed to do so, as the car hit Herzberg at 39 mph (63 km/h).

The forward-looking Uber dashcam did not pick up Herzberg until approximately 1.4 seconds before the collision, suggesting (as the sheriff did) that the crash may have been completely unavoidable even if Vasquez hadn't been distracted in the seconds leading up to the crash.

However, night-time video shot by other motorists in the days following the crash, plus their comments, suggest that the area may have been better illuminated than the dashcam footage, viewed in isolation would suggest. This raises the possibility that Herzberg's appearing so late in the Uber video could merely be an indication that the camera had insufficient sensitivity or was otherwise poorly calibrated for the environment and setting in which it was operating. If these crowd-sourced re-creations are indeed representative of the visibility conditions on the actual night that the accident occurred, then Herzberg would have been visible to Vasquez as soon as there was a clear sight line had Vasquez only been looking ahead, refuting the assertion that the accident was unavoidable.

Complicating things even further, there is evidence that suggests the discrepancies in visibility between the dashcam footage and the civilian re-creation submissions are not at all invented or illusory, but are, instead, real phenomena whose progenitor is purported to be the set of severely under-powered headlights installed on the car Vasquez was monitoring. While all of these potential scenarios will likely affect any charging decisions and/or other legal actions (if they materialize at all), none currently have any objective validation or otherwise meaningful support, especially in relation to one another.

While jaywalking can constitute the illegal preemptive of control of the roadway, it is not necessarily the proximate cause of an accident. Had Herzberg instead been a moose or a disabled school bus in legal control of the roadway, passengers of the self-driving car—which failed to assure a clear stopping distance within its radius of vision—may have been killed instead. Motor vehicle operators must always be watchful for children, animals, and other hazards which may encroach into the roadway.

Coordination with state government

Prior to the fatal incident, Arizona Governor Doug Ducey had encouraged Uber to enter the state. He signed Executive Order 2015-09 on August 25, 2015, entitled "Self-Driving Vehicle Testing and Piloting in the State of Arizona; Self-Driving Vehicle Oversight Committee", establishing a welcoming attitude to autonomous vehicle testing. According to Ducey's office, the committee, which consists of eight state employees appointed by the governor, has met twice since it was formed.

In December 2016, Ducey had released a statement welcoming Uber's autonomous cars: "Arizona welcomes Uber self-driving cars with open arms and wide open roads. While California puts the brakes on innovation and change with more bureaucracy and more regulation, Arizona is paving the way for new technology and new businesses." Emails between Uber and the office of the governor showed that Ducey was informed that the testing of self-driving vehicles would begin in August 2016, several months ahead of the official announcement welcoming Uber in December. On March 1, 2018, Ducey signed Executive Order (XO) 2018-04, outlining regulations for autonomous vehicles. Notably, XO 2018-04 requires the company testing self-driving cars to provide a written statement that "the fully autonomous vehicle will achieve a minimal risk condition" if a failure occurs.

Aftermath

After the collision that killed Herzberg, Uber ceased testing self-driving vehicles in all four cities (Tempe, San Francisco, Pittsburgh, and Toronto) where it had deployed them. On March 26, Governor Ducey sent a letter to Uber CEO Dara Khosrowshahi, suspending Uber's testing of self-driving cars in the state. In the letter, Ducey stated "As governor, my top priority is public safety. Improving public safety has always been the emphasis of Arizona's approach to autonomous vehicle testing, and my expectation is that public safety is also the top priority for all who operate this technology in the state of Arizona." Uber also announced it would not renew its permit to test self-driving cars in California after the California Department of Motor Vehicles wrote to inform Uber that its permit would expire on March 31, and "any follow-up analysis or investigations from the recent crash in Arizona" would have to be addressed before the permit could be renewed.

Legal woes for Uber were among the collision fallout. Herzberg's daughter retained the law firm Bellah Perez, and together with the husband quickly reached an undisclosed settlement on March 28 while local and federal authorities continued their investigation. Herzberg's mother, father, and son also retaining legal counsel. While a confidential settlement buried the liability issue, it suggested a sufficient legal cause of action. The abundance of event data recorders left few questions of fact for a jury to decide. Although the Yavapai County Attorney declined to charge Uber with a criminal violation in 2019 for the death of Herzberg, a Maricopa County grand jury indicted the safety driver on one count of negligent homicide in 2020.

The incident caused some companies to temporarily cease road testing of self-driving vehicles. Nvidia CEO Jensen Huang has stated "We don't know that we would do anything different, but we should give ourselves time to see if we can learn from that incident." Uber acknowledged that mistakes were made in its brash pursuit to ultimately create a safer driving environment.

Later in the year, Uber issued a reflective 70-page safety report in which Uber stated the potential for its self-driving cars to be safer than those driven by humans, however some of their employees worry that Uber is taking shortcuts to hit internal milestones. To be legal in all states for private use, or anywhere at the commercial level, the technology must hard code assured clear distance ahead driving.

The National Highway Traffic Safety Administration and the American Automobile Association had previously identified nighttime driving as an area for safety improvement. This follows similar changes in attitudes against tolerating drunk driving, starting in the late 1970s through the 1990s, and has occurred in concert with a cultural shift towards active lifestyles and multi-modal use of roadways which has been formally adopted by the National Association of City Transportation Officials.

After the collision that killed Herzberg on March 18, 2018, Uber returned their self-driving cars to the roads in public testing in Pittsburgh, Pennsylvania on December 20, 2018. Uber said they received authorization from the Pennsylvania Department of Transportation. Uber said they were also pursuing the same with cars on roads in San Francisco, California and Toronto, Ontario.

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