100% renewable energy

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/100%25_renewable_energy

 

The Shepherds Flat Wind Farm is an 845 megawatt (MW) wind farm in the U.S. state of Oregon.

 

The 550 MW Desert Sunlight Solar Farm in California.

 

The 392 MW Ivanpah Solar Power Facility in California: The facility's three towers.

 

Construction of the Salt Tanks which provide efficient thermal energy storage  so that output can be provided after the sun goes down, and output can be scheduled to meet demand requirements. The 280 MW Solana Generating Station is designed to provide six hours of energy storage. This allows the plant to generate about 38 percent of its rated capacity over the course of a year.

 

Global public support for different energy sources (2011) based on a poll by Ipsos Global @dvisor

 

Comparing trends in worldwide energy use, the growth of renewable energy to 2015 is the green line

 

The endeavor to use 100% renewable energy for electricity, heating/cooling and transport is motivated by global warming, pollution and other environmental issues, as well as economic and energy security concerns. Shifting the total global primary energy supply to renewable sources requires a transition of the energy system. According to the Intergovernmental Panel on Climate Change there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown more quickly than even advocates anticipated. As of 2019, however, it needs to grow six times faster to limit global warming to 2 °C (3.6 °F).

100% renewable energy in a country is typically a more challenging goal than carbon neutrality. The latter is a climate mitigation target, politically decided by many countries, and may also be achieved by balancing the total carbon footprint of the country (not only emissions from energy and fuel) with carbon dioxide removal and carbon projects abroad.

In 2014, renewable sources such as wind, geothermal, solar, biomass, and burnt waste provided 19% of the total energy consumed worldwide, with roughly half of that coming from traditional use of biomass. The most important sector is electricity with a renewable share of 22.8%, most of it coming from hydropower with a share of 16.6%, followed by wind with 3.1%. As of 2018 according to REN21 transformation is picking up speed in the power sector, but urgent action is required in heating, cooling and transport. There are many places around the world with grids that are run almost exclusively on renewable energy. At the national level, at least 30 nations already have renewable energy contributing more than 20% of the energy supply.

According to a review of the 181 peer-reviewed papers on 100% renewable energy which were published until 2018, "[t]he great majority of all publications highlights the technical feasibility and economic viability of 100% RE systems." While there are still many publications which focus on electricity only, there is a growing number of papers that cover different energy sectors and sector-coupled, integrated energy systems. This cross-sectoral, holistic approach is seen as an important feature of 100% renewable energy systems and is based on the assumption "that the best solutions can be found only if one focuses on the synergies between the sectors" of the energy system such as electricity, heat, transport or industry.

Professors S. Pacala and Robert H. Socolow of Princeton University have developed a series of "climate stabilization wedges" that can allow us to maintain our quality of life while avoiding catastrophic climate change, and "renewable energy sources," in aggregate, constitute the largest number of their "wedges."

Mark Z. Jacobson, professor of civil and environmental engineering at Stanford University and director of its Atmosphere and Energy program, says that producing all new energy with wind power, solar power, and hydropower by 2030 is feasible, and that existing energy supply arrangements could be replaced by 2050. Barriers to implementing the renewable energy plan are seen to be "primarily social and political, not technological or economic". Jacobson says that energy costs today with a wind, solar, and water system should be similar to today's energy costs from other optimally cost-effective strategies. The main obstacle against this scenario is the lack of political will. His conclusions have been disputed by other researchers. Jacobson published a response that disputed the piece point by point and claimed that the authors were motivated by allegiance to energy technologies that the 2015 paper excluded.

Similarly, in the United States, the independent National Research Council has noted that "sufficient domestic renewable resources exist to allow renewable electricity to play a significant role in future electricity generation and thus help confront issues related to climate change, energy security, and the escalation of energy costs ... Renewable energy is an attractive option because renewable resources available in the United States, taken collectively, can supply significantly greater amounts of electricity than the total current or projected domestic demand."

The main barriers to the widespread implementation of large-scale renewable energy and low-carbon energy strategies are political rather than technological. According to the 2013 Post Carbon Pathways report, which reviewed many international studies, the key roadblocks are: climate change denial, the fossil fuels lobby, political inaction, unsustainable energy consumption, outdated energy infrastructure, and financial constraints.

History

Using 100% renewable energy was first suggested in a paper in Science  published in 1975 by Danish physicist Bent Sørensen, which was followed by several other proposals. In 1976 energy policy analyst Amory Lovins coined the term "soft energy path" to describe an alternative future where energy efficiency and appropriate renewable energy sources steadily replace a centralized energy system based on fossil and nuclear fuels.

In 1998 the first detailed analysis of scenarios with very high shares of renewables were published. These were followed by the first detailed 100% scenarios. In 2006 a PhD thesis was published by Czisch in which it was shown that in a 100% renewable scenario energy supply could match demand in every hour of the year in Europe and North Africa. In the same year Danish Energy professor Henrik Lund published a first paper in which he addresses the optimal combination of renewables, which was followed by several other papers on the transition to 100% renewable energy in Denmark. Since then Lund has been publishing several papers on 100% renewable energy. After 2009 publications began to rise steeply, covering 100% scenarios for countries in Europe, America, Australia and other parts of the world.

Even in the early 21st century it was extraordinary for scientists and decision-makers to consider the concept of 100% renewable electricity. However, renewable energy progress has been so rapid that things have totally changed since then:

Solar photovoltaic modules have dropped about 75 percent in price. Current scientific and technological advances in the laboratory suggest that they will soon be so cheap that the principal cost of going solar on residential and commercial buildings will be installation. On-shore wind power is spreading over all continents and is economically competitive with fossil and nuclear power in several regions. Concentrated solar thermal power (CST) with thermal storage has moved from the demonstration stage of maturity to the limited commercial stage and still has the potential for further cost reductions of about 50 percent.

Renewable energy use has grown much faster than even advocates had anticipated. Wind turbines generate 39 percent of Danish electricity, and Denmark has many biogas digesters and waste-to-energy plants as well. Together, wind and biomass provide 44% of the electricity consumed by the country's six million inhabitants. In 2010, Portugal's 10 million people produced more than half their electricity from indigenous renewable energy resources. Spain's 40 million inhabitants meet one-third of their electrical needs from renewables.

Renewable energy has a history of strong public support. In America, for example, a 2013 Gallup survey showed that two in three Americans want the U.S. to increase domestic energy production using solar power (76%), wind power (71%), and natural gas (65%). Far fewer want more petroleum production (46%) and more nuclear power (37%). Least favored is coal, with about one in three Americans favouring it.

REN21 says renewable energy already plays a significant role and there are many policy targets which aim to increase this:

At the national level, at least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond, and some 120 countries have various policy targets for longer-term shares of renewable energy, including a binding 20% by 2020 target for the European Union. Some countries have much higher long-term policy targets of up to 100% renewables. Outside Europe, a diverse group of 20 or more other countries target renewable energy shares in the 2020–2030 time frame that range from 10% to 50%.

Nuclear power involves accident risks with substantial consequences (e.g., Fukushima nuclear disaster, Chernobyl disaster) and the expensive problem of safe long-term high-level radioactive waste management, and carbon capture and storage has rather limited safe storage potentials. These constraints have also led to an interest in 100% renewable energy. A well established body of academic literature has been written over the past decade, evaluating scenarios for 100% renewable energy for various geographical areas. In recent years, more detailed analyses have emerged from government and industry sources. The incentive to use 100% renewable energy is created by global warming and ecological as well as economic concerns, post peak oil.

The first country to propose 100% renewable energy was Iceland, in 1998. Proposals have been made for Japan in 2003, and for Australia in 2011. Albania, Iceland, and Paraguay obtain essentially all of their electricity from renewable sources (Albania and Paraguay 100% from hydroelectricity, Iceland 72% hydro and 28% geothermal). Norway obtains nearly all of its electricity from renewable sources (97 percent from hydropower). Iceland proposed using hydrogen for transportation and its fishing fleet. Australia proposed biofuel for those elements of transportation not easily converted to electricity. The road map for the United States, commitment by Denmark, and Vision 2050 for Europe set a 2050 timeline for converting to 100% renewable energy, later reduced to 2040 in 2011. Zero Carbon Britain 2030 proposes eliminating carbon emissions in Britain by 2030 by transitioning to renewable energy. In 2015, Hawaii enacted a law that the Renewable Portfolio Standard shall be 100 percent by 2045. This is often confused with renewable energy. If electricity produced on the grid is 65 GWh from fossil fuel and 35 GWh from renewable energy and rooftop off grid solar produces 80 GWh of renewable energy then the total renewable energy is 115 GWh and the total electricity on the grid is 100 GWh. Then the RPS is 115 percent.

Cities like Paris and Strasbourg in France, planned to use 100% renewable energy by 2050.

It is estimated that the world will spend an extra $8 trillion over the next 25 years to prolong the use of non-renewable resources, a cost that would be eliminated by transitioning instead to 100% renewable energy. Research that has been published in Energy Policy suggests that converting the entire world to 100% renewable energy by 2050 is both possible and affordable, but requires political support. It would require building many more wind turbines and solar power systems but wouldn't utilize bioenergy. Other changes involve use of electric cars and the development of enhanced transmission grids and storage. As part of the Paris Agreement, countries periodically update their climate change targets for the future, by 2018 no G20 country had committed to a 100% renewable target.

Until 2018 there were 181 peer-reviewed papers on 100% renewable energy. In the same year, 100% renewable energy was also mentioned in the Special Report on Global Warming of 1.5 °C as a potential means to "expand the range of 1.5 °C pathways", if the findings can be corroborated.

Recent developments

The Fourth Revolution: Energy is a German documentary film released in 2010. It shows the vision of a global society, which lives in a world where the energy is produced 100% with renewable energies, showing a complete reconstruction of the economy, to reach this goal. In 2011, Hermann Scheer wrote the book The Energy Imperative: 100 Percent Renewable Now, published by Routledge.

Reinventing Fire is a book by Amory Lovins released in October 2011. By combining reduced energy use with energy efficiency gains, Lovins says that there will be a $5 trillion saving and a faster-growing economy. This can all be done with the profitable commercialization of existing energy-saving technologies, through market forces, led by business. Former US president Bill Clinton says the book is a "wise, detailed and comprehensive blueprint". The first paragraph of the preface says:

Imagine fuel without fear. No climate change. No oil spills, dead coal miners, dirty air, devastated lands, lost wildlife. No energy poverty. No oil-fed wars, tyrannies, or terrorists. Nothing to run out. Nothing to cut off. Nothing to worry about. Just energy abundance, benign and affordable, for all, for ever.

The Intergovernmental Panel on Climate Change has said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. In a 2011 review of 164 recent scenarios of future renewable energy growth, the report noted that the majority expected renewable sources to supply more than 17% of total energy by 2030, and 27% by 2050; the highest forecast projected 43% supplied by renewables by 2030 and 77% by 2050.

In 2011, the International Energy Agency has said that solar energy technologies, in its many forms, can make considerable contributions to solving some of the most urgent problems the world now faces:

The development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries' energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared.

In 2011, the refereed journal Energy Policy published two articles by Mark Z. Jacobson, a professor of engineering at Stanford University, and research scientist Mark A. Delucchi, about changing our energy supply mix and "Providing all global energy with wind, water, and solar power". The articles analyze the feasibility of providing worldwide energy for electric power, transportation, and heating/cooling from wind, water, and sunlight (WWS), which are safe clean options. In Part I, Jacobson and Delucchi discuss WWS energy system characteristics, aspects of energy demand, WWS resource availability, WWS devices needed, and material requirements. They estimate that 3,800,000 5 MW wind turbines, 5350 100 MW geothermal power plants, and 270 new 1300 MW hydroelectric power plants will be required. In terms of solar power, an additional 49,000 300 MW concentrating solar plants, 40,000 300 MW solar photovoltaic power plants, and 1.7 billion 3 kW rooftop photovoltaic systems will also be needed. Such an extensive WWS infrastructure could decrease world power demand by 30%. In Part II, Jacobson and Delucchi address variability of supply, system economics, and energy policy initiatives associated with a WWS system. The authors advocate producing all new energy with WWS by 2030 and replacing existing energy supply arrangements by 2050. Barriers to implementing the renewable energy plan are seen to be "primarily social and political, not technological or economic". Energy costs with a WWS system should be similar to today's energy costs.

In general, Jacobson has said wind, water and solar technologies can provide 100 percent of the world's energy, eliminating all fossil fuels. He advocates a "smart mix" of renewable energy sources to reliably meet electricity demand:

Because the wind blows during stormy conditions when the sun does not shine and the sun often shines on calm days with little wind, combining wind and solar can go a long way toward meeting demand, especially when geothermal provides a steady base and hydroelectric can be called on to fill in the gaps.

A 2012 study by the University of Delaware for a 72 GW system considered 28 billion combinations of renewable energy and storage and found the most cost-effective, for the PJM Interconnection, would use 17 GW of solar, 68 GW of offshore wind, and 115 GW of onshore wind, although at times as much as three times the demand would be provided. 0.1% of the time would require generation from other sources.

In March 2012, Denmark's parliament agreed on a comprehensive new set promotional programs for energy efficiency and renewable energy that will lead to the country getting 100 percent of electricity, heat and fuels from renewables by 2050. IRENEC is an annual conference on 100% renewable energy started in 2011 by Eurosolar Turkey. The 2013 conference was in Istanbul.

More recently, Jacobson and his colleagues have developed detailed proposals for switching to 100% renewable energy produced by wind, water and sunlight, for New York, California and Washington states, by 2050. As of 2014, a more expansive new plan for the 50 states has been drawn up, which includes an online interactive map showing the renewable resource potential of each of the 50 states. The 50-state plan is part of The Solutions Project, an independent outreach effort led by Jacobson, actor Mark Ruffalo, and film director Josh Fox.

As of 2014, many detailed assessments show that the energy service needs of a world enjoying radically higher levels of wellbeing, can be economically met entirely through the diverse currently available technological and organisational innovations around wind, solar, biomass, biofuel, hydro, ocean and geothermal energy. Debate over detailed plans remain, but transformations in global energy services based entirely around renewable energy are in principle technically practicable, economically feasible, socially viable, and so realisable. This prospect underpins the ambitious commitment by Germany, one of the world's most successful industrial economies, to undertake a major energy transition, Energiewende.

In 2015 a study was published in Energy and Environmental Science that describes a pathway to 100% renewable energy in the United States by 2050 without using biomass. Implementation of this roadmap is regarded as both environmentally and economically feasible and reasonable, as by 2050 it would save about $600 Billion Dollars health costs a year due to reduced air pollution and $3.3 Trillion global warming costs. This would translate in yearly cost savings per head of around $8300 compared to a business as usual pathway. According to that study, barriers that could hamper implementation are neither technical nor economic but social and political, as most people didn't know that benefits from such a transformation far exceeded the costs.

In June 2017, twenty-one researchers published an article in the Proceedings of the National Academy of Sciences of the United States of America rejecting Jacobson's earlier PNAS article, accusing him of modeling errors and of using invalid modeling tools. They further asserted he made implausible assumptions through his reliance upon increasing national energy storage from 43 minutes to 7 weeks, increasing hydrogen production by 100,000%, and increasing hydropower by the equivalent of 600 Hoover Dams. Article authors David G. Victor called Jacobson's work "dangerous" and Ken Caldeira emphasized that increasing hydropower output by 1,300 gigawatts, a 25% increase, is the equivalent flow of 100 Mississippi Rivers. Jacobson published a response in the same issue of the PNAS and also authored a blog post where he asserted the researchers were advocates of the fossil fuel industry. Another study published in 2017 confirmed the earlier results for a 100% renewable power system for North America, without changes in hydropower assumptions, but with more realistic emphasis on a balanced storage portfolio, in particular seasonal storage, and for competitive economics.

Grid integration simulation

In 2015, Jacobson and Delucchi, together with Mary Cameron and Bethany Frew, examined with computer simulation (LOADMATCH), in more detail how a wind-water-solar (WWS) system can track the energy demand from minute to minute. This turned out to be possible in the United States for 6 years, including WWS variability by extreme weather events. In 2017, the plan was further developed for 139 countries by a team of 27 researchers and in 2018, Jacobson and Delucchi with Mary Cameron and Brian Mathiesen published the LOADMATCH results for 20 regions in which the 139 countries in the world are divided. According to this research, a WWS system can follow the demand in all regions.

The program LOADMATCH receives as input estimated series, per half minute during 2050-2055, of

• the energy demand
• the intermittent wind and solar energy supply predicted with a 3D global climate / weather model GATOR-GCMOM
• the hydropower, geothermal, tidal and wave energy

and specifications of

• the capacities and maximum loading / unloading speeds of the different types of storage
• losses due to storage, transport, distribution and maintenance
• a demand-supply management system (smart grid).

The program has been carried out for each region 10-20 times with adapted input for the storage capacities, until a solution was found in which the energy demand was followed, per half minute for 5 years, with low costs.

The WWS system is assumed to connect in the electric network

• geographically dispersed variable energy sources, concentrated solar power (CSP) and hydro power
• storage facilities: pumped hydro, as heat in CSP plants, in batteries, as hydrogen by electrolysis of water, or as compressed air underground.

Places with near 100% renewable electricity

See: List of countries by electricity production from renewable sources

Some places have high percentages, for example the electricity sector in Denmark, as of 2014, is 45% wind power, with plans in place to reach 85%. The electricity sector in Canada and the electricity sector in New Zealand have even higher percentages of renewables (mostly hydro), 65% and 75% respectively, and Austria is approaching 70%. As of 2015, the electricity sector in Germany sometimes meets almost 100% of the electricity demand with PV and wind power, and renewable electricity is over 25%. Albania has 94.8% of installed capacity as hydroelectric, 5.2% diesel generator; but Albania imports 39% of its electricity. In 2016, Portugal achieved 100% renewable electricity for four days between 7 May and 11 May, partly because efficient energy use had reduced electricity demand. France and Sweden have low carbon intensity, since they predominantly use a mixture of nuclear power and hydroelectricity. 

 

Although electricity is currently a big fraction of primary energy; it is to be expected that with renewable energy deployment primary energy use will go down sharply as electricity use increases, as it is likely to be combined with some degree of further electrification. For example, electric cars achieve much better fuel efficiency than fossil fuel cars, and another example is renewable heat such as in the case of Denmark which is proposing to move to greater use of heat pumps for heating buildings which provide multiple kilowatts of heat per kilowatt of electricity. 

100% clean electricity

Other electricity generating sources are considered clean, though not necessarily renewable, as they also do not emit carbon dioxide or other greenhouse gases. The largest of these is nuclear energy which produces no emissions. Carbon capture and storage projects may still use coal or natural gas but capture carbon dioxide for storage or alternative uses. Pathways to eliminate greenhouse gases may include these in addition to renewable energy so as to avoid shutting down existing plants and allow for flexibility in designing a carbon-free electric grid.

In 2018 California passed SB 100, which will mandate 100% clean, carbon-free by 2045, including a 60% renewable electricity goal by 2030. 2019 legislation in Washington will also require 100% clean electricity by 2045, eliminating coal by 2025. Further states and territories that will require 100% carbon-free electricity are Hawaii, Maine, Nevada, New Mexico, New York, Puerto Rico, and Washington, DC.

Obstacles

The most significant barriers to the widespread implementation of large-scale renewable energy and low carbon energy strategies, at the pace required to prevent runaway climate change, are primarily political and not technological. According to the 2013 Post Carbon Pathways report, which reviewed many international studies, the key roadblocks are:

• Climate change denial
• Efforts to impede renewable energy by the fossil fuel industry
• Political paralysis
• Unsustainable consumption of energy and resources
• Path dependencies and outdated infrastructure
• Financial and governance constraints

NASA Climate scientist James Hansen discusses the problem with rapid phase out of fossil fuels and said that while it is conceivable in places such as New Zealand and Norway, "suggesting that renewables will let us phase rapidly off fossil fuels in the United States, China, India, or the world as a whole is almost the equivalent of believing in the Easter Bunny and Tooth Fairy." In 2013, Smil analyzed proposals to depend on wind and solar-generated electricity including the proposals of Jacobson and colleagues, and writing in an issue of Spectrum prepared by the Institute of Electrical and Electronics Engineers, he identified numerous points of concern, such as cost, intermittent power supply, growing NIMBYism, and a lack of infrastructure as negative factors and said that "History and a consideration of the technical requirements show that the problem is much greater than these advocates have supposed." Smil and Hansen are concerned about the variable output of solar and wind power, but American physicist Amory Lovins has said that the electricity grid can cope, just as it routinely backs up nonworking coal-fired and nuclear plants with working ones.

In 1999 American academic Dr. Gregory Unruh published a dissertation identifying the systemic barriers to the adoption and diffusion of renewable energy technologies. This theoretical framework was called Carbon Lock-in and pointed to the creation of self-reinforcing feedbacks that arise through the co-evolution of large technological systems, like electricity and transportation networks, with the social and political institutions that support and benefit from system growth. Once established, these techno-institutional complexes become "locked-in" and resist efforts to transform them towards more environmentally sustainable systems based on renewable sources.

Lester R. Brown founder and president of the Earth Policy Institute, a nonprofit research organization based in Washington, D.C., says a rapid transition to 100% renewable energy is both possible and necessary. Brown compares with the U.S. entry into World War II and the subsequent rapid mobilization and transformation of the US industry and economy. A quick transition to 100% renewable energy and saving of our civilization is proposed by Brown to follow an approach with similar urgency.

The International Energy Agency says that there has been too much attention on issue of the variability of renewable electricity production. The issue of intermittent supply applies to popular renewable technologies, mainly wind power and solar photovoltaics, and its significance depends on a range of factors which include the market penetration of the renewables concerned, the balance of plant and the wider connectivity of the system, as well as the demand side flexibility. Variability will rarely be a barrier to increased renewable energy deployment when dispatchable generation such as hydroelectricity or solar thermal storage is also available. But at high levels of market penetration it requires careful analysis and management, and additional costs may be required for back-up or system modification. Renewable electricity supply in the 20-50+% penetration range has already been implemented in several European systems, albeit in the context of an integrated European grid system.

In 2011, the Intergovernmental Panel on Climate Change, the world's leading climate researchers selected by the United Nations, said "as infrastructure and energy systems develop, in spite of the complexities, there are few, if any, fundamental technological limits to integrating a portfolio of renewable energy technologies to meet a majority share of total energy demand in locations where suitable renewable resources exist or can be supplied". IPCC scenarios "generally indicate that growth in renewable energy will be widespread around the world". The IPCC said that if governments were supportive, and the full complement of renewable energy technologies were deployed, renewable energy supply could account for almost 80% of the world's energy use within forty years. Rajendra Pachauri, chairman of the IPCC, said the necessary investment in renewables would cost only about 1% of global GDP annually. This approach could contain greenhouse gas levels to less than 450 parts per million, the safe level beyond which climate change becomes catastrophic and irreversible.

In November 2014 the Intergovernmental Panel on Climate Change came out with their fifth report, saying that in the absence of any one technology (such as bioenergy, carbon dioxide capture and storage, nuclear, wind and solar), climate change mitigation costs can increase substantially depending on which technology is absent. For example, it may cost 40% more to reduce carbon emissions without carbon dioxide capture. (Table 3.2)

Google spent $30 million on their RE

Seasonal Energy Storage

Hydropower is currently the only large scale low-carbon seasonal energy storage. In countries with high variation in energy demand by season (for example the UK uses far more gas for heating in the winter than it uses electricity) but lacking hydropower electrical interconnectors to countries with lots of hydropower (e.g. UK - Norway) will probably be insufficient and development of a hydrogen economy will likely be needed: this is being trialled in the UK and 8 TWh of inter-seasonal hydrogen energy storage has been proposed.

In Australia as well as storing renewable energy as hydrogen it is also proposed to be exported in the form of ammonia.

Geothermal energy (updated)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Geothermal_energy

 

Geothermal power center in the Usulután Department, El Salvador.

 

Steam rising from the Nesjavellir Geothermal Power Station in Iceland

 

A geothermal energy plant near the Salton Sea, California.

 

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials (in currently uncertain but possibly roughly equal proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective geothermal originates from the Greek roots γη (geo), meaning earth, and θερμος (thermos), meaning hot.

Earth's internal heat is thermal energy generated from radioactive decay and continual heat loss from Earth's formation. Temperatures at the core–mantle boundary may reach over 4000 °C (7,200 °F). The high temperature and pressure in Earth's interior cause some rock to melt and solid mantle to behave plastically, resulting in portions of the mantle convecting upward since it is lighter than the surrounding rock. Rock and water is heated in the crust, sometimes up to 370 °C (700 °F).

With water from hot springs, geothermal energy has been used for bathing since Paleolithic times and for space heating since ancient Roman times, but it is now better known for electricity generation. Worldwide, 11,700 megawatts (MW) of geothermal power was available in 2013. An additional 28 gigawatts of direct geothermal heating capacity is installed for district heating, space heating, spas, industrial processes, desalination and agricultural applications as of 2010.

Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. 

The earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, plate boundary movement and interest rates. Pilot programs like EWEB's customer opt in Green Power Program show that customers would be willing to pay a little more for a renewable energy source like geothermal. But as a result of government assisted research and industry experience, the cost of generating geothermal power has decreased by 25% over the 1980s and 1990s. In 2001, geothermal energy costs between two and ten US cents per kWh.

History

The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd century BC

Hot springs have been used for bathing at least since Paleolithic times. The oldest known spa is a stone pool on China's Lisan mountain built in the Qin Dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. In the first century AD, Romans conquered Aquae Sulis, now Bath, Somerset, England, and used the hot springs there to feed public baths and underfloor heating. The admission fees for these baths probably represent the first commercial use of geothermal power. The world's oldest geothermal district heating system in Chaudes-Aigues, France, has been operating since the 15th century. The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy.

In 1892, America's first district heating system in Boise, Idaho was powered directly by geothermal energy, and was copied in Klamath Falls, Oregon in 1900. The first known building in the world to utilize geothermal energy as its primary heat source was the Hot Lake Hotel in Union County, Oregon, whose construction was completed in 1907. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time. Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his house. Steam and hot water from geysers began heating homes in Iceland starting in 1943.

Global geothermal electric capacity. Upper red line is installed capacity; lower green line is realized production.

 

In the 20th century, demand for electricity led to the consideration of geothermal power as a generating source. Prince Piero Ginori Conti tested the first geothermal power generator on 4 July 1904, at the same Larderello dry steam field where geothermal acid extraction began. It successfully lit four light bulbs. Later, in 1911, the world's first commercial geothermal power plant was built there. It was the world's only industrial producer of geothermal electricity until New Zealand built a plant in 1958. In 2012, it produced some 594 megawatts.

Lord Kelvin invented the heat pump in 1852, and Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912. But it was not until the late 1940s that the geothermal heat pump was successfully implemented. The earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange system, but sources disagree as to the exact timeline of his invention. J. Donald Kroeker designed the first commercial geothermal heat pump to heat the Commonwealth Building (Portland, Oregon) and demonstrated it in 1946. Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948. The technology became popular in Sweden as a result of the 1973 oil crisis, and has been growing slowly in worldwide acceptance since then. The 1979 development of polybutylene pipe greatly augmented the heat pump's economic viability.

In 1960, Pacific Gas and Electric began operation of the first successful geothermal electric power plant in the United States at The Geysers in California. The original turbine lasted for more than 30 years and produced 11 MW net power.

The binary cycle power plant was first demonstrated in 1967 in the USSR and later introduced to the US in 1981. This technology allows the generation of electricity from much lower temperature resources than previously. In 2006, a binary cycle plant in Chena Hot Springs, Alaska, came on-line, producing electricity from a record low fluid temperature of 57 °C (135 °F).

Electricity

Direct Use Data 2015

Country	Usage (MWt) 2015
United States	17,415.91
Philippines	3.30
Indonesia	2.30
Mexico	155.82
Italy	1,014.00
New Zealand	487.45
Iceland	2,040.00
Japan	2,186.17
Iran	81.50
El Salvador	3.36
Kenya	22.40
Costa Rica	1.00
Russia	308.20
Turkey	2,886.30
Papua-New Guinea	0.10
Guatemala	2.31
Portugal	35.20
China	17,870.00
France	2,346.90
Ethiopia	2.20
Germany	2,848.60
Austria	903.40
Australia	16.09
Thailand	128.51

The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which was expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in online capacity since 2005. IGA projects growth to 18,500 MW by 2015, due to the projects presently under consideration, often in areas previously assumed to have little exploitable resources.

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California. The Philippines is the second highest producer, with 1,904 MW of capacity online. Geothermal power makes up approximately 27% of Philippine electricity generation.

In 2016, Indonesia set in third with 1,647 MW online behind USA at 3,450 MW and the Philippines at 1,870 MW, but Indonesia will become second due to an additional online 130 MW at the end of 2016 and 255 MW in 2017. Indonesia's 28,994 MW are the largest geothermal reserves in the world, and it is predicted to overtake the US in the next decade.

Installed geothermal electric capacity

Country	Capacity (MW) 2007	Capacity (MW) 2010	% of national electricity production	% of global geothermal production
United States	2687	3086	0.3	29
Philippines	1969.7	1904	27	18
Indonesia	992	1197	3.7	11
Mexico	953	958	3	9
Italy	810.5	843	1.5	8
New Zealand	471.6	628	10	6
Iceland	421.2	575	30	5
Japan	535.2	536	0.1	5
Iran	250	250
El Salvador	204.2	204	25
Kenya	128.8	167	11.2
Costa Rica	162.5	166	14
Nicaragua	87.4	88	10
Russia	79	82
Turkey	38	82
Papua-New Guinea	56	56
Guatemala	53	52
Portugal	23	29
China	27.8	24
France	14.7	16
Ethiopia	7.3	7.3
Germany	8.4	6.6
Austria	1.1	1.4
Australia	0.2	1.1
Thailand	0.3	0.3
TOTAL	9,981.9	10,959.7

Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Forêts, France, while an earlier effort in Basel, Switzerland was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America.

The thermal efficiency of geothermal electric plants is low, around 10–23%, because geothermal fluids do not reach the high temperatures of steam from boilers. The laws of thermodynamics limits the efficiency of heat engines in extracting useful energy. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. System efficiency does not materially affect operational costs as it would for plants that use fuel, but it does affect return on the capital used to build the plant. In order to produce more energy than the pumps consume, electricity generation requires relatively hot fields and specialized heat cycles. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor can be quite large – up to 96% has been demonstrated. The global average was 73% in 2005. 

Types

Geothermal energy comes in either vapor-dominated or liquid-dominated forms. Larderello and The Geysers are vapor-dominated. Vapor-dominated sites offer temperatures from 240 to 300 °C that produce superheated steam. 

Liquid-dominated plants

Liquid-dominated reservoirs (LDRs) are more common with temperatures greater than 200 °C (392 °F) and are found near young volcanoes surrounding the Pacific Ocean and in rift zones and hot spots. Flash plants are the common way to generate electricity from these sources. Pumps are generally not required, powered instead when the water turns to steam. Most wells generate 2-10 MWe. Steam is separated from a liquid via cyclone separators, while the liquid is returned to the reservoir for reheating/reuse. As of 2013, the largest liquid system is Cerro Prieto in Mexico, which generates 750 MWe from temperatures reaching 350 °C (662 °F). The Salton Sea field in Southern California offers the potential of generating 2000 MWe.

Lower temperature LDRs (120–200 °C) require pumping. They are common in extensional terrains, where heating takes place via deep circulation along faults, such as in the Western US and Turkey. Water passes through a heat exchanger in a Rankine cycle binary plant. The water vaporizes an organic working fluid that drives a turbine. These binary plants originated in the Soviet Union in the late 1960s and predominate in new US plants. Binary plants have no emissions.

Thermal energy

Lower temperature sources produce the energy equivalent of 100M BBL per year. Sources with temperatures of 30–150 °C are used without conversion to electricity as district heating, greenhouses, fisheries, mineral recovery, industrial process heating and bathing in 75 countries. Heat pumps extract energy from shallow sources at 10–20 °C in 43 countries for use in space heating and cooling. Home heating is the fastest-growing means of exploiting geothermal energy, with global annual growth rate of 30% in 2005 and 20% in 2012.

Approximately 270 petajoules (PJ) of geothermal heating was used in 2004. More than half went for space heating, and another third for heated pools. The remainder supported industrial and agricultural applications. Global installed capacity was 28 GW, but capacity factors tend to be low (30% on average) since heat is mostly needed in winter. Some 88 PJ for space heating was extracted by an estimated 1.3 million geothermal heat pumps with a total capacity of 15 GW.

Heat for these purposes may also be extracted from co-generation at a geothermal electrical plant.

Heating is cost-effective at many more sites than electricity generation. At natural hot springs or geysers, water can be piped directly into radiators. In the hot, dry ground, earth tubes or downhole heat exchangers can collect the heat. However, even in areas where the ground is colder than room temperature, heat can often be extracted with a geothermal heat pump more cost-effectively and cleanly than by conventional furnaces. These devices draw on much shallower and colder resources than traditional geothermal techniques. They frequently combine functions, including air conditioning, seasonal thermal energy storage, solar energy collection, and electric heating. Heat pumps can be used for space heating essentially anywhere.

Iceland is the world leader in direct applications. Some 92.5% of its homes are heated with geothermal energy, saving Iceland over $100 million annually in avoided oil imports. Reykjavík, Iceland has the world's biggest district heating system, often used to heat pathways and roads to hinder the accumulation of ice. Once known as the most polluted city in the world, it is now one of the cleanest.

Enhanced geothermal

Enhanced geothermal systems (EGS) actively inject water into wells to be heated and pumped back out. The water is injected under high pressure to expand existing rock fissures to enable the water to freely flow in and out. The technique was adapted from oil and gas extraction techniques. However, the geologic formations are deeper and no toxic chemicals are used, reducing the possibility of environmental damage. Drillers can employ directional drilling to expand the size of the reservoir.

Small-scale EGS have been installed in the Rhine Graben at Soultz-sous-Forêts in France and at Landau and Insheim in Germany.

Economics

Geothermal power requires no fuel (except for pumps), and is therefore immune to fuel cost fluctuations. However, capital costs are significant. Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. A typical well doublet (extraction and injection wells) in Nevada can support 4.5 megawatts (MW) and costs about $10 million to drill, with a 20% failure rate.

A power plant at The Geysers

 

In total, electrical plant construction and well drilling cost about €2–5 million per MW of electrical capacity, while the break–even price is 0.04–0.10 € per kW·h. Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and break–even above $0.054 per kW·h in 2007. Direct heating applications can use much shallower wells with lower temperatures, so smaller systems with lower costs and risks are feasible. Residential geothermal heat pumps with a capacity of 10  kilowatt (kW) are routinely installed for around $1–3,000 per  kilowatt. District heating systems may benefit from economies of scale if demand is geographically dense, as in cities and greenhouses, but otherwise, piping installation dominates capital costs. The capital cost of one such district heating system in Bavaria was estimated at somewhat over 1 million € per  MW. Direct systems of any size are much simpler than electric generators and have lower maintenance costs per kW·h, but they must consume electricity to run pumps and compressors. Some governments subsidize geothermal projects. 

Geothermal power is highly scalable: from a rural village to an entire city.

The most developed geothermal field in the United States is The Geysers in Northern California.

Geothermal projects have several stages of development. Each phase has associated risks. At the early stages of reconnaissance and geophysical surveys, many projects are canceled, making that phase unsuitable for traditional lending. Projects moving forward from the identification, exploration and exploratory drilling often trade equity for financing.

Resources

Enhanced geothermal system 1:Reservoir 2:Pump house 3:Heat exchanger 4:Turbine hall 5:Production well 6:Injection well 7:Hot water to district heating 8:Porous sediments 9:Observation well 10:Crystalline bedrock

The Earth's internal thermal energy flows to the surface by conduction at a rate of 44.2 terawatts (TW), and is replenished by radioactive decay of minerals at a rate of 30 TW. These power rates are more than double humanity's current energy consumption from all primary sources, but most of this energy flow is not recoverable. In addition to the internal heat flows, the top layer of the surface to a depth of 10 meters (33 ft) is heated by solar energy during the summer, and releases that energy and cools during the winter. 

Outside of the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per kilometer of depth in most of the world. The conductive heat flux averages 0.1 MW/km². These values are much higher near tectonic plate boundaries where the crust is thinner. They may be further augmented by fluid circulation, either through magma conduits, hot springs, hydrothermal circulation or a combination of these.

A geothermal heat pump can extract enough heat from shallow ground anywhere in the world to provide home heating, but industrial applications need the higher temperatures of deep resources. The thermal efficiency and profitability of electricity generation is particularly sensitive to temperature. The most demanding applications receive the greatest benefit from a high natural heat flux, ideally from using a hot spring. The next best option is to drill a well into a hot aquifer. If no adequate aquifer is available, an artificial one may be built by injecting water to hydraulically fracture the bedrock. This last approach is called hot dry rock geothermal energy in Europe, or enhanced geothermal systems in North America. Much greater potential may be available from this approach than from conventional tapping of natural aquifers.

Estimates of the potential for electricity generation from geothermal energy vary sixfold, from .035to2TW depending on the scale of investments. Upper estimates of geothermal resources assume enhanced geothermal wells as deep as 10 kilometres (6 mi), whereas existing geothermal wells are rarely more than 3 kilometres (2 mi) deep. Wells of this depth are now common in the petroleum industry. The deepest research well in the world, the Kola superdeep borehole, is 12 kilometres (7 mi) deep.

Myanmar Engineering Society has identified at least 39 locations (in Myanmar) capable of geothermal power production and some of these hydrothermal reservoirs lie quite close to Yangon which is a significant underutilized resource.

Production

According to the Geothermal Energy Association (GEA) installed geothermal capacity in the United States grew by 5%, or 147.05 MW, since the last annual survey in March 2012. This increase came from seven geothermal projects that began production in 2012. GEA also revised its 2011 estimate of installed capacity upward by 128 MW, bringing current installed U.S. geothermal capacity to 3,386 MW.

Renewability and sustainability

Geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth's heat content. The Earth has an internal heat content of 10³¹ joules (3·10¹⁵ TWh), approximately 100 billion times the 2010 worldwide annual energy consumption. About 20% of this is residual heat from planetary accretion, and the remainder is attributed to higher radioactive decay rates that existed in the past. Natural heat flows are not in equilibrium, and the planet is slowly cooling down on geologic timescales. Human extraction taps a minute fraction of the natural outflow, often without accelerating it. According to most official descriptions of geothermal energy use, it is currently called renewable and sustainable because it returns an equal volume of water to the area that the heat extraction takes place, but at a somewhat lower temperature. For instance, the water leaving the ground is 300 degrees, and the water returning is 200 degrees, the energy obtained is the difference in heat that is extracted. Current research estimates of impact on the heat loss from the earth’s core are based on a studies done up through 2012. However, if household and industrial uses of this energy source were to expand dramatically over coming years, based on a diminishing fossil fuel supply and a growing world population which is rapidly industrializing requiring additional energy sources, then the estimates on the impact on the earth's cooling rate would need to be re-evaluated.

A more technical description of the earth’s core energy would be to state that it is vast and enormous in quantity, but calling it unlimited and renewable in nature is a misnomer which might well fit today's current levels of use; but perhaps, just like humanity's impact on weather through global warming, there was a long held belief that human activity such as car emissions were minor, and could not impact weather conditions, but when an expanding number of cars reach a critical point, a global impact resulted.

Geothermal power is also considered to be sustainable thanks to its power to sustain the Earth's intricate ecosystems. By using geothermal sources of energy present generations of humans will not endanger the capability of future generations to use their own resources to the same amount that those energy sources are presently used. Further, due to its low emissions geothermal energy is considered to have excellent potential for mitigation of global warming [DJS -- by whom?]. 

Electricity Generation at Poihipi, New Zealand

 

Electricity Generation at Ohaaki, New Zealand

 

Electricity Generation at Wairakei, New Zealand

 

Even though geothermal power is globally sustainable, extraction must still be monitored to avoid local depletion. Over the course of decades, individual wells draw down local temperatures and water levels until a new equilibrium is reached with natural flows. The three oldest sites, at Larderello, Wairakei, and the Geysers have experienced reduced output because of local depletion. Heat and water, in uncertain proportions, were extracted faster than they were replenished. If production is reduced and water is reinjected, these wells could theoretically recover their full potential. Such mitigation strategies have already been implemented at some sites. The long-term sustainability of geothermal energy has been demonstrated at the Lardarello field in Italy since 1913, at the Wairakei field in New Zealand since 1958, and at The Geysers field in California since 1960.

Falling electricity production may be boosted through drilling additional supply boreholes, as at Poihipi and Ohaaki. The Wairakei power station has been running much longer, with its first unit commissioned in November 1958, and it attained its peak generation of 173 MW in 1965, but already the supply of high-pressure steam was faltering, in 1982 being derated to intermediate pressure and the station managing 157 MW. Around the start of the 21st century it was managing about 150 MW, then in 2005 two 8 MW isopentane systems were added, boosting the station's output by about 14 MW. Detailed data are unavailable, being lost due to re-organisations. One such re-organisation in 1996 causes the absence of early data for Poihipi (started 1996), and the gap in 1996/7 for Wairakei and Ohaaki; half-hourly data for Ohaaki's first few months of operation are also missing, as well as for most of Wairakei's history.

Environmental effects

Geothermal power station in the Philippines

 

Krafla Geothermal Station in northeast Iceland

 

Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO
₂), hydrogen sulfide (H
₂S), methane (CH
₄) and ammonia (NH
₃). These pollutants contribute to global warming, acid rain, and noxious smells if released. Existing geothermal electric plants emit an average of 122 kilograms (269 lb) of CO
₂ per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust.

In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic elements such as mercury, arsenic, boron, and antimony. These chemicals precipitate as the water cools, and can cause environmental damage if released. The modern practice of injecting cooled geothermal fluids back into the Earth to stimulate production has the side benefit of reducing this environmental risk.

Direct geothermal heating systems contain pumps and compressors, which may consume energy from a polluting source. This parasitic load is normally a fraction of the heat output, so it is always less polluting than electric heating. However, if the electricity is produced by burning fossil fuels, then the net emissions of geothermal heating may be comparable to directly burning the fuel for heat. For example, a geothermal heat pump powered by electricity from a combined cycle natural gas plant would produce about as much pollution as a natural gas condensing furnace of the same size. Therefore, the environmental value of direct geothermal heating applications is highly dependent on the emissions intensity of the neighboring electric grid. 

Plant construction can adversely affect land stability. Subsidence has occurred in the Wairakei field in New Zealand. In Staufen im Breisgau, Germany, tectonic uplift occurred instead, due to a previously isolated anhydrite layer coming in contact with water and turning into gypsum, doubling its volume. Enhanced geothermal systems can trigger earthquakes as part of hydraulic fracturing. The project in Basel, Switzerland was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection.

Geothermal has minimal land and freshwater requirements. Geothermal plants use 3.5 square kilometres (1.4 sq mi) per gigawatt of electrical production (not capacity) versus 32 square kilometres (12 sq mi) and 12 square kilometres (4.6 sq mi) for coal facilities and wind farms respectively.^[13] They use 20 litres (5.3 US gal) of freshwater per MW·h versus over 1,000 litres (260 US gal) per MW·h for nuclear, coal, or oil.

Legal frameworks

Some of the legal issues raised by geothermal energy resources include questions of ownership and allocation of the resource, the grant of exploration permits, exploitation rights, royalties, and the extent to which geothermal energy issues have been recognized in existing planning and environmental laws. Other questions concern overlap between geothermal and mineral or petroleum tenements. Broader issues concern the extent to which the legal framework for encouragement of renewable energy assists in encouraging geothermal industry innovation and development.