Verificationism is based on verifying propositions. The distinctive claim of verificationism is that the result of such verifications is, by definition, truth. That is, truth is reducible to this process of verification.
According to perspectivalism and relativism, a proposition is only true relative to a particular perspective. Roughly, a proposition is true relative to a perspective if and only if it is accepted, endorsed, or legitimated by that perspective.
Many authors writing on the topic of the notion of truth advocate
or endorse combinations of the above positions. Each of these epistemic
conceptions of truth can be subjected to various criticisms. Some
criticisms apply across the board, while others are more specific.
In positivism, a proposition is meaningful, and thus capable of being true or false, if and only if it is verifiable by sensoryexperiences.
A-priorism, often used in the domains of logic and mathematics, holds a proposition true if and only if a priori reasoning can verify it. In the related certainty theory, associated with Descartes and Spinoza, a proposition is true if and only if it is known with certainty.
Logical positivism attempts to combine positivism with a version of a-priorism.
Another theory of truth which is related to a-priorism is the
concept-containment theory of truth. The concept-containment theory of
truth is the view that a proposition is true if and only if the concept
of the predicate of the proposition is "contained in" the concept of the
subject. For example, the proposition that bachelors are unmarried men
is true, on this view, because the concept of the predicate (unmarried
men) is contained in the concept of the subject (bachelor). A
contemporary reading of the concept-containment theory of truth is to
say that every true proposition is an analytically true proposition.
Perspectivist views
According to perspectivalism and relativism, a proposition is only true relative to a particular perspective. The Sophists' relativist and Nietzsche's
philosophy are some of the most famous examples of such
perspectivalism. There are four main versions of perspectivalism, and
some interesting subdivisions:
Individual perspectivalism
According
to individual perspectivalism, perspectives are the points of view of
particular individual persons. So, a proposition is true for a person if
and only if it is accepted or believed by that person (i.e., "true for
me").
Discourse perspectivalism
According to discourse perspectivalism, a perspective is simply any system of discourse, and it is a matter of convention which one chooses. A proposition is true relative to that particular discourse if and only if it is somehow produced (or "legitimated") by the methods of that particular discourse. An example of this appears in the philosophy of mathematics: formalism. A proposition is true relative to a set of assumptions just in case it is a deductive consequence of those assumptions.
A perspective is, roughly, the broad opinions, and perhaps norms and practices, of a community
of people, perhaps all having some special feature in common. So, a
proposition is true (for a community C) if, and only if, there is a consensus amongst the members of C for believing it.
Power
In the power-oriented view, a perspective is a community enforced by power, authority, military might, privilege, etc. So, a proposition is true if it "makes us powerful" or is "produced by power", thus the slogan "truth is power".
Truth-generating perspectives are collectives opposed to, or engaged in struggle against, power and authority. For example, the collective perspective of the "proletariat". So, proposition is true if it is the "product of political struggle" for the "emancipation of the workers" (Adorno). This view is again associated with some social constructivists (e.g., feministepistemologists).
Transcendental perspectivalism
On this conception, a truth-conferring perspective is something transcendental, and outside immediate human reach. The idea is that there is a transcendental or ideal epistemic perspective and truth is, roughly, what is accepted or recognized-as-true from that ideal perspective. There are two subvarieties of transcendental perspectivalism:
Coherentism
The ideal epistemic perspective is the set of "maximally coherent and consistent
propositions". A proposition is true if and only if it is a member of
this maximally coherent and consistent set of propositions (associated
with several German and British 19th century idealists).
Theological perspectivalism
Theologically, the ideal epistemic perspective is that of God ("God's point of view"). From this perspective, a proposition is true if and only if it agrees with the thoughts of God.
Pragmatic views
Although the pragmatic theory of truth
is not strictly classifiable as an epistemic theory of truth, it does
bear a relationship to theories of truth that are based on concepts of
inquiry and knowledge.
The ideal epistemic perspective is that of "completed science",
which will appear in the (temporal) "limit of scientific inquiry". A
proposition is true if and only if, in the long run it will come to be
accepted by a group of inquirers using scientific rational inquiry. This can also be modalized:
a proposition is true if, and only if, in the long run it would come to
be accepted by a group of inquirers, if they were to use scientific
rational inquiry. This view is thus a modification of the consensus
view. The consensus need to satisfy certain constraints in order for the
accepted propositions to be true. For example, the methods used must be
those of scientific inquiry (criticism, observation, reproducibility,
etc.). This "modification" of the consensus view is an appeal to the
correspondence theory of truth, which is opposed to the consensus theory
of truth.
Long-run scientific pragmatism was defended by Charles Sanders Peirce. A variant of this viewpoint is associated with Jürgen Habermas, though he later abandoned it.
Similar to regular biofuels, carbon-negative fuels only remain
carbon-negative as long as the fuel is not combusted. Upon combustion,
the carbon they contain (i.e. taken from industrial sources) is released
again into the atmosphere (thus leveling out the environmental
benefit). The time between fuel production and combustion of the fuel
(the carbon storage time) can thus be quite short (far shorter than the
100 year storage time set for afforestation/reforestation projects under the Kyoto Protocol. or even underground carbon storage.
Carbon-neutral fuels are used in Germany and Iceland for distributed storage of renewable energy,
minimizing problems of wind and solar intermittency, and enabling
transmission of wind, water, and solar power through existing natural
gas pipelines. Such renewable fuels
could alleviate the costs and dependency issues of imported fossil
fuels without requiring either electrification of the vehicle fleet or
conversion to hydrogen or other fuels, enabling continued compatible and
affordable vehicles. A 250 kilowatt synthetic methane plant has been built in Germany and it is being scaled up to 10 megawatts.
Carbon credits can also play an important role for carbon-negative fuels.
Production
Carbon-neutral
fuels are synthetic hydrocarbons. They can be produced in chemical
reactions between carbon dioxide, which can be captured from power
plants or the air, and hydrogen, which is created by the electrolysis of
water using renewable energy. The fuel, often referred to as electrofuel, stores the energy that was used in the production of the hydrogen.
Coal can also be used to produce the hydrogen, but that would not be a
carbon-neutral source. Carbon dioxide can be captured and buried, making
fossil fuels carbon-neutral, although not renewable. Carbon capture
from exhaust gas can make carbon-neutral fuels carbon negative. Other
hydrocarbons can be broken down to produce hydrogen and carbon dioxide
which could then be stored while the hydrogen is used for energy or
fuel, which would also be carbon-neutral.
The most energy-efficient fuel to produce is hydrogen gas, which can be used in hydrogen fuel cell vehicles, and which requires the fewest process steps to produce.
There are a few more fuels that can be created using hydrogen. Formic acid for example can be made by reacting the hydrogen with CO2. Formic acid combined with CO2 can form isobutanol.
Methanol can be made from a chemical reaction of a carbon-dioxide
molecule with three hydrogen molecules to produce methanol and water.
The stored energy can be recovered by burning the methanol in a
combustion engine, releasing carbon dioxide, water, and heat. Methane
can be produced in a similar reaction. Special precautions against
methane leaks are important since methane is nearly 100 times as potent
as CO2, in terms of Global warming potential. More energy can be used to combine methanol or methane into larger hydrocarbon fuel molecules.
Researchers have also suggested using methanol to produce dimethyl ether.
This fuel could be used as a substitute for diesel fuel due to its
ability to self ignite under high pressure and temperature. It is
already being used in some areas for heating and energy generation. It
is nontoxic, but must be stored under pressure. Larger hydrocarbons and ethanol can also be produced from carbon dioxide and hydrogen.
All synthetic hydrocarbons are generally produced at temperatures of 200–300 °C, and at pressures of 20 to 50 bar. Catalysts
are usually used to improve the efficiency of the reaction and create
the desired type of hydrocarbon fuel. Such reactions are exothermic and
use about 3 mol of hydrogen per mole of carbon dioxide involved. They
also produce large amounts of water as a byproduct.
Sources of carbon for recycling
The most economical source of carbon for recycling into fuel is flue-gas emissions from fossil-fuel combustion where it can be obtained for about US$7.50 per ton.
However, this is not carbon-neutral, since the carbon is of fossil
origin, therefore moving carbon from the geosphere to the atmosphere.
Automobile exhaust gas capture has also been seen as economical but
would require extensive design changes or retrofitting. Since carbonic acid in seawater is in chemical equilibrium with atmospheric carbon dioxide, extraction of carbon from seawater has been studied. Researchers have estimated that carbon extraction from seawater would cost about $50 per ton. Carbon capture from ambient air is more costly, at between $94 and $232 per ton and is considered impractical for fuel synthesis or carbon sequestration.
Direct air capture is less developed than other methods. Proposals for
this method involve using a caustic chemical to react with carbon
dioxide in the air to produce carbonates. These can then be broken down and hydrated to release pure CO2
gas and regenerate the caustic chemical. This process requires more
energy than other methods because carbon dioxide is at much lower
concentrations in the atmosphere than in other sources.
Researchers have also suggested using biomass as a carbon source
for fuel production. Adding hydrogen to the biomass would reduce its
carbon to produce fuel. This method has the advantage of using plant
matter to cheaply capture carbon dioxide. The plants also add some
chemical energy to the fuel from biological molecules. This may be a
more efficient use of biomass than conventional biofuel
because it uses most of the carbon and chemical energy from the biomass
instead of releasing as much energy and carbon. Its main disadvantage
is, as with conventional ethanol production, it competes with food
production.
Renewable and nuclear energy costs
Nighttime wind power is considered the most economical form of electrical power with which to synthesize fuel, because the load curve
for electricity peaks sharply during the warmest hours of the day, but
wind tends to blow slightly more at night than during the day.
Therefore, the price of nighttime wind power is often much less
expensive than any alternative. Off-peak wind power prices in high wind
penetration areas of the U.S. averaged 1.64 cents per kilowatt-hour in 2009, but only 0.71 cents/kWh during the least expensive six hours of the day. Typically, wholesale electricity costs 2 to 5 cents/kWh during the day. Commercial fuel synthesis companies suggest they can produce gasoline for less than petroleum fuels when oil costs more than $55 per barrel.
In 2010, a team of process chemists led by Heather Willauer of the U.S. Navy, estimates that 100 megawatts of electricity can produce 160 cubic metres (41,000 US gal) of jet fuel
per day and shipboard production from nuclear power would cost about
$1,600 per cubic metre ($6/US gal). While that was about twice the
petroleum fuel cost in 2010, it is expected to be much less than the
market price in less than five years if recent trends continue. Moreover, since the delivery of fuel to a carrier battle group costs about $2,100 per cubic metre ($8/US gal), shipboard production is already much less expensive.
Willauer said seawater is the "best option" for a source of synthetic jet fuel. By April 2014, Willauer's team had not yet made fuel to the standard required by military jets,
but they were able in September 2013 to use the fuel to fly a
radio-controlled model airplane powered by a common two-stroke internal
combustion engine.
Because the process requires a large input of electrical energy, a
plausible first step of implementation would be for American
nuclear-powered aircraft carriers (the Nimitz-class and the Gerald R. Ford-class) to manufacture their own jet fuel. The U.S. Navy is expected to deploy the technology some time in the 2020s.
Demonstration projects and commercial development
A 250 kilowatt methane synthesis plant was constructed by the Center for Solar Energy and Hydrogen Research (ZSW) at Baden-Württemberg and the Fraunhofer Society in Germany and began operating in 2010. It is being upgraded to 10 megawatts, scheduled for completion in autumn, 2012.
Audi has constructed a carbon-neutral liquefied natural gas (LNG) plant in Werlte, Germany. The plant is intended to produce transportation fuel to offset LNG used in their A3 Sportback g-tron automobiles, and can keep 2,800 metric tons of CO2 out of the environment per year at its initial capacity.
Carbon-neutral
fuels can lead to greenhouse gas remediation because carbon dioxide gas
would be reused to produce fuel instead of being released into the
atmosphere. Capturing the carbon dioxide in flue gas emissions from
power plants would eliminate their greenhouse gas emissions, although
burning the fuel in vehicles would release that carbon because there is
no economical way to capture those emissions. This approach would reduce net carbon dioxide emission by about 50% if it were used on all fossil fuel power plants. Most coal and natural gas power plants have been predicted to be economically retrofittable with carbon dioxide scrubbers for carbon capture to recycle flue exhaust or for carbon sequestration. Such recycling is expected to not only cost less than the excess economic impacts of climate change if it were not done, but also to pay for itself as global fuel demand growth and peak oil shortages increase the price of petroleum and fungiblenatural gas.
Capturing CO2 directly from the air or extracting
carbonic acid from seawater would also reduce the amount of carbon
dioxide in the environment, and create a closed cycle of carbon to
eliminate new carbon dioxide emissions.
Use of these methods would eliminate the need for fossil fuels
entirely, assuming that enough renewable energy could be generated to
produce the fuel. Using synthetic hydrocarbons to produce synthetic
materials such as plastics could result in permanent sequestration of
carbon from the atmosphere.
Technologies
Traditional fuels, methanol or ethanol
Some authorities have recommended producing methanol
instead of traditional transportation fuels. It is a liquid at normal
temperatures and can be toxic if ingested. Methanol has a higher octane rating than gasoline but a lower energy density,
and can be mixed with other fuels or used on its own. It may also be
used in the production of more complex hydrocarbons and polymers. Direct
methanol fuel cells have been developed by Caltech's Jet Propulsion Laboratory to convert methanol and oxygen into electricity.
It is possible to convert methanol into gasoline, jet fuel or other
hydrocarbons, but that requires additional energy and more complex
production facilities.
Methanol is slightly more corrosive than traditional fuels, requiring
automobile modifications on the order of US$100 each to use it.
Microalgae is a potential carbon neutral fuel, but efforts to turn it into one have been unsuccessful so far. Microalgae are aquatic organisms living in a large and diverse group. They are unicellular organisms that do not have complex cell structures like plants. However, they are still photo autotrophic, able to use solar energy to convert chemical forms via photosynthesis. They are typically found in freshwater and marine system and there are approximately 50,000 species that has been found.
Microalgae will be a huge substitute for the needs of fuel in the era of global warming. Growing microalgae is important in supporting the global movement of reducing global CO2 emissions. Microalgae has a better ability, compared to conventional biofuel crops, in acting as a CO2fixation source as they convert CO2 into biomass via photosynthesis at higher rates. Microalgae is a better CO2 converter than conventional biofuel crops.
With that being said, a considerable interest to cultivate
microalgae has been increasing in the past several years. Microalgae is
seen as a potential feedstock for biofuel production as their ability to
produce polysaccharides and triglycerides (sugars and fats) which are both raw materials for bioethanol and biodiesel fuel.
Microalgae also can be used as a livestock feed due to their proteins.
Even more, some species of microalgae produce valuable compounds such as
pigments and pharmaceuticals.
Production
Two
main ways of cultivating microalgae are raceway pond systems and
photo-bioreactors. Raceway pond systems are constructed by a closed loop
oval channel that has a paddle wheel to circulate water and prevent
sedimentation. The channel is open to the air and its depth is in the
range of 0.25–0.4 m (0.82–1.31 ft).
The pond needs to be kept shallow since self-shading and optical
absorption can cause the limitation of light penetration through the
solution of algae broth. PBRs's culture medium is constructed by closed
transparent array of tubes. It has a central reservoir which circulated
the microalgae broth. PBRs is an easier system to be controlled compare
to the raceway pond system, yet it costs a larger overall production
expenses.
The carbon emissions from microalgae biomass produced in raceway
ponds could be compared to the emissions from conventional biodiesel by
having inputs of energy and nutrients as carbon intensive. The
corresponding emissions from microalgae biomass produced in PBRs could
also be compared and might even exceed the emissions from conventional
fossil diesel. The inefficiency is due to the amount of electricity used
to pump the algae broth around the system. Using co-product to generate
electricity is one strategy that might improve the overall carbon
balance. Another thing that needs to be acknowledged is that
environmental impacts can also come from water management, carbon
dioxide handling, and nutrient supply, several aspects that could
constrain system design and implementation options. But, in general,
Raceway Pond systems demonstrate a more attractive energy balance than
PBR systems.
Economy
Production
cost of microalgae-biofuel through implementation of raceway pond
systems is dominated by the operational cost which includes labour, raw
materials, and utilities. In raceway pond system, during the cultivation
process, electricity takes up the largest energy fraction of total
operational energy requirements. It is used to circulate the microalgae
cultures. It takes up an energy fraction ranging from 22% to 79%.
In contrast, capital cost dominates the cost of production of
microalgae-biofuel in PBRs. This system has a high installation cost
though the operational cost is relatively lower than raceway pond
systems.
Microalgae-biofuel production costs a larger amount of money
compared to fossil fuel production. The cost estimation of producing
microalgae-biofuel is around $3.1 per litre ($11.57/US gal). Meanwhile, data provided by California Energy Commission shows that fossil fuel production in California costs $0.48 per litre ($1.820/US gal) by October, 2018. This price ratio leads many to choose fossil fuel for economic reasons, even as this results in increased emissions of carbon dioxide and other greenhouse gases. Advancement in renewable energy is being developed to reduce this production cost.
Environmental impact
There are several known environmental impacts of cultivating microalgae:
Water resource
There could be an increasing demand of fresh water as microalgaes are aquatic organisms. Fresh water is used to compensate evaporation
in raceway pond systems. It is used for cooling purpose. Using
recirculating water might compensate for the needs of the water but it
comes with a greater risk of infection and inhibition: bacteria, fungi, viruses.
These inhibitors are found in greater concentrations in recycled waters
along with non-living inhibitors such as organic and inorganic
chemicals and remaining metabolites from destroyed microalgae cells.
Algae toxicity
Many microalgae species could produce some toxins (ranging from ammonia to physiologically active polypeptides and polysaccharides)
in some point in their life cycle. These algae toxins may be important
and valuable products in their applications in biomedical, toxicological
and chemical research. However, they also come with negative effects.
These toxins can be either acute or chronic. The acute example is the paralytic shellfish poisoning that may cause death. One of the chronic one is the carcinogenic
and ulcerative tissue slow changes caused by carrageenan toxins
produced in red tides. Since the high variability of toxins producing
microalgae species, the presence or absence of toxins in a pond will not
always be able to be predicted. It all depends on the environment and ecosystem condition.
Diesel from water and carbon dioxide
Audi has co-developed E-diesel, a carbon-neutral fuel with a high cetane number.
It is also working on E-benzin, which is created using a similar process.
Production
Water
undergoes electrolysis at high temperatures to form Hydrogen gas and
Oxygen gas. The energy to perform this is extracted from renewable
sources such as wind power. Then, the hydrogen is reacted with
compressed carbon dioxide captured by direct air capture.
The reaction produces blue crude which consists of hydrocarbon. The
blue crude is then refined to produce high efficiency E-diesel.
This method is, however, still debatable because with the current
production capability it can only produce 3,000 liters in a few months,
0.0002% of the daily production of fuel in the US.
Furthermore, the thermodynamic and economic feasibility of this
technology have been questioned. An article suggests that this
technology does not create an alternative to fossil fuel but rather
converting renewable energy into liquid fuel. The article also states
that the energy return on energy invested using fossil diesel is 18
times higher than that for e-diesel.
History
Investigation
of carbon-neutral fuels has been ongoing for decades. A 1965 report
suggested synthesizing methanol from carbon dioxide in air using nuclear
power for a mobile fuel depot. Shipboard production of synthetic fuel using nuclear power was studied in 1977 and 1995. A 1984 report studied the recovery of carbon dioxide from fossil fuel plants. A 1995 report compared converting vehicle fleets for the use of carbon-neutral methanol with the further synthesis of gasoline.
A solar combisystem provides both solar space heating and cooling as well as hot water from a common array of solar thermal collectors, usually backed up by an auxiliary non-solar heat source.
Solar combisystems may range in size from those installed in
individual properties to those serving several in a block heating
scheme. Those serving larger groups of properties district heating tend to be called central solar heating schemes.
Many types of solar combisystems are produced - over 20 were identified in the first international survey, conducted as part of IEA SHC Task 14
in 1997. The systems on the market in a particular country may be more
restricted, however, as different systems have tended to evolve in
different countries. Prior to the 1990s such systems tended to be
custom-built for each property. Since then commercialised packages have
developed and are now generally used.
Depending on the size of the combisystem installed, the annual space heating contribution can range from 10% to 60% or more in ultra-low energyPassivhaus-type buildings; even up to 100% where a large interseasonal thermal store
or concentrating solar thermal heat is used. The remaining heat
requirement is supplied by one or more auxiliary sources in order to
maintain the heat supply once the solar heated water is exhausted. Such
auxiliary heat sources may also use other renewable energy sources (when a geothermal heat pump is used, the combisystem is called geosolar) and, sometimes, rechargeable batteries.
During 2001, around 50% of all the domestic solar collectors installed in Austria, Switzerland, Denmark, and Norway were to supply combisystems, while in Sweden it was greater. In Germany,
where the total collector area installed (900,000 m2) was much larger
than in the other countries, 25% was for combisystem installations.
Combisystems have also been installed in Canada since the mid-1980s.
Following the work of IEA SHC Task 26 (1998 to 2002), solar combisystems can be classified according to two main aspects; firstly by the heat (or cool) storage category (the way in which water is added to and drawn from the storage tank and its effect on stratification); secondly by the auxiliary heat (or cool) management category (the way in which non-solar-thermal auxiliary heaters or coolers can be integrated into the system).
Maintaining stratification
(the variation in water temperature from cooler at the foot of a tank
to warmer at the top) is important so that the combisystem can supply
hot or cool water and space heating and cooling water at different
temperatures.
Heat and cool storage categories
Category
Description
A
No controlled storage device for space heating and cooling.
B
Heat and cool management and stratification enhancement by means of
multiple tanks and/or by multiple inlet/outlet pipes and/or by three- or
four-way valves to control flow through the inlet/outlet pipes.
C
Heat and cool management using natural convection in storage tanks and/or between them to maintain stratification to a certain extent.
D
Heat and cool management using natural convection in storage tanks and built-in stratification devices.
B/D
Heat and cool management by natural convection in storage tanks and
built-in stratifiers as well as multiple tanks and/or multiple
inlet/outlet pipes and/or three- or four-way valves to control flow
through the inlet/outlet pipes.
Auxiliary heat and cool management categories
Category
Description
M (mixed mode)
The space heating loop is fed from a single store heated by both solar collectors and the auxiliary heater.
P (parallel mode)
The space heating and cooling loop is fed alternatively by the solar collectors
(or a solar water storage tank), or by the auxiliary heater or cooler;
or there is no hydraulic connection between the solar heat and cool
distribution and the auxiliary heat emissions.
S (serial mode)
The space heating and cooling loop may be fed by the auxiliary
heater, or by both the solar collectors (or a solar water storage tank)
and the auxiliary heater connected in series on the return line of the
space heating loop.
A solar combisystem may therefore be described as being of type B/DS, CS, etc.
Within these types, systems may be configured in many different
ways. For the individual house they may – or may not – have the storage
tanks, controls and auxiliary heater and cooler integrated into a single
prefabricated package. In contrast, there are also large centralised systems serving a number of properties.
The simplest combisystems – the Type A – have no "controlled storage device". Instead they pump warm (or cool) water from the solar collectors through underfloor central heating pipes embedded in the concrete floor slab. The floor slab is thickened to provide thermal mass and so that the heat and cool from the pipes (at the bottom of the slab) is released during the evening.
Combisystem design
The
size and complexity of combisystems, and the number of options
available, mean that comparing design alternatives is not
straightforward. Useful approximations of performance can be produced
relatively easily, however accurate predictions remain difficult.
Tools for designing solar combisystems are available, varying from manufacturer's guidelines to nomograms (such as the one developed for IEA SHC Task 26) to various computer simulation software of varying complexity and accuracy.
Among the software and packages are CombiSun (released free by the Task 26 team, which can be used for basic system sizing) and the free SHWwin (Austria, in German). Other commercial systems are available.
The element unique to combisystems is the way that these
technologies are combined, and the control systems used to integrate
them, plus any stratifier technology that might be employed.
Relationship to low energy building
By the end of the 20th century solar hot water systems had been capable of meeting a significant portion of domestic hot water requirements in many climate zones. However it was only with the development of reliable low-energy building
techniques in the last decades of the century that extending such
systems for space heating became realistic in temperate and colder climatic zones.
As heat demand reduces, the overall size and cost of the system
is reduced, and the lower water temperatures typical of solar heating
may be more readily used - especially when coupled with underfloor heating or wall heating. The volume occupied by the equipment also reduces, which also increases the flexibility of its location.
In common with other heating systems in low-energy buildings,
system performance is more sensitive to the number of occupants, room
temperature and ventilation rates, when compared to regular buildings
where such effects are small in relation to the higher overall energy
demand.
Seasonal thermal energy storage (or STES) is the
storage of heat or cold for periods of up to several months. The thermal
energy can be collected whenever it is available and be used whenever
needed, such as in the opposing season. For example, heat from solar
collectors or waste heat
from air conditioning equipment can be gathered in hot months for space
heating use when needed, including during winter months. Waste heat
from industrial process can similarly be stored and be used much later.
Or the natural cold of winter air can be stored for summertime air conditioning.
STES stores can serve district heating systems, as well as single
buildings or complexes. Among seasonal storages used for heating, the
design peak annual temperatures generally are in the range of 27 to
80 °C (81 to 180 °F), and the temperature difference occurring in the
storage over the course of a year can be several tens of degrees. Some
systems use a heat pump to help charge and discharge the storage during
part or all of the cycle. For cooling applications, often only
circulation pumps are used. A less common term for STES technologies is
interseasonal thermal energy storage.
There
are several types of STES technology, covering a range of applications
from single small buildings to community district heating networks.
Generally, efficiency increases and the specific construction cost
decreases with size.
Underground thermal energy storage
UTES (underground thermal energy storage), in which the
storage medium may be geological strata ranging from earth or sand to
solid bedrock, or aquifers. UTES technologies include:
ATES (aquifer thermal energy storage).
An ATES store is composed of a doublet, totaling two or more wells into
a deep aquifer that is contained between impermeable geological layers
above and below. One half of the doublet is for water extraction and the
other half for reinjection, so the aquifer is kept in hydrological
balance, with no net extraction. The heat (or cold) storage medium is
the water and the substrate it occupies. Germany’s Reichstag building has been both heated and cooled since 1999 with ATES stores, in two aquifers at different depths.
In the Netherlands there are well over 1,000 ATES systems, which are now a standard construction option.
A significant system has been operating at Richard Stockton College (New Jersey) for several years.
ATES has a lower installation cost than BTES because usually fewer
holes are drilled, but ATES has a higher operating cost. Also, ATES
requires particular underground conditions to be feasible, including the
presence of an aquifer.
BTES (borehole thermal energy storage). BTES stores can be constructed wherever boreholes
can be drilled, and are composed of one to hundreds of vertical
boreholes, typically 155 mm (6.102 in) in diameter. Systems of all sizes
have been built, including many quite large.
The strata can be anything from sand to crystalline hardrock, and
depending on engineering factors the depth can be from 50 to 300 metres
(164 to 984 ft). Spacings have ranged from 3 to 8 metres (9.8 to
26.2 ft). Thermal models can be used to predict seasonal temperature
variation in the ground, including the establishment of a stable
temperature regime which is achieved by matching the inputs and outputs
of heat over one or more annual cycles. Warm-temperature seasonal heat
stores can be created using borehole fields to store surplus heat
captured in summer to actively raise the temperature of large thermal
banks of soil so that heat can be extracted more easily (and more
cheaply) in winter. Interseasonal Heat Transfer uses water circulating in pipes embedded in asphalt solar collectors to transfer heat to Thermal Banks
created in borehole fields. A ground source heat pump is used in winter
to extract the warmth from the Thermal Bank to provide space heating
via underfloor heating.
A high Coefficient of Performance is obtained because the heat pump
starts with a warm temperature of 25 °C (77 °F) from the thermal store,
instead of a cold temperature of 10 °C (50 °F) from the ground.
A BTES operating at Richard Stockton College since 1995 at a peak of
about 29 °C (84.2 °F) consists of 400 boreholes 130 metres (427 ft) deep
under a 3.5-acre (1.4 ha) parking lot. It has a heat loss of 2% over
six months.
The upper temperature limit for a BTES store is 85 °C (185 °F) due to
characteristics of the PEX pipe used for BHEs, but most do not approach
that limit. Boreholes can be either grout- or water-filled depending on
geological conditions, and usually have a life expectancy in excess of
100 years. Both a BTES and its associated district heating system can be
expanded incrementally after operation begins, as at Neckarsulm,
Germany.
BTES stores generally do not impair use of the land, and can exist under
buildings, agricultural fields and parking lots. An example of one of
the several kinds of STES illustrates well the capability of
interseasonal heat storage. In Alberta, Canada, the homes of the Drake Landing Solar Community
(in operation since 2007), get 97% of their year-round heat from a
district heat system that is supplied by solar heat from solar-thermal
panels on garage roofs. This feat – a world record – is enabled by
interseasonal heat storage in a large mass of native rock that is under a
central park. The thermal exchange occurs via a cluster of 144
boreholes, drilled 37 metres (121 ft) into the earth. Each borehole is
155 mm (6.1 in) in diameter and contains a simple heat exchanger made of
small diameter plastic pipe, through which water is circulated. No heat
pumps are involved.
CTES (cavern or mine thermal energy storage).
STES stores are possible in flooded mines, purpose-built chambers, or
abandoned underground oil stores (e.g. those mined into crystalline
hardrock in Norway), if they are close enough to a heat (or cold) source
and market.
Energy Pilings. During construction of large buildings, BHE
heat exchangers much like those used for BTES stores have been spiraled
inside the cages of reinforcement bars for pilings, with concrete then
poured in place. The pilings and surrounding strata then become the
storage medium.
GIITS (geo interseasonal insulated thermal storage). During
construction of any building with a primary slab floor, an area
approximately the footprint of the building to be heated, and > 1 m
in depth, is insulated on all 6 sides typically with HDPE
closed cell insulation. Pipes are used to transfer solar energy into
the insulated area, as well as extracting heat as required on demand. If
there is significant internal ground water flow, remedial actions are
needed to prevent it.
Surface and above ground technologies
Pit Storage.
Lined, shallow dug pits that are filled with gravel and water as the
storage medium are used for STES in many Danish district heating
systems. Storage pits are covered with a layer of insulation and then
soil, and are used for agriculture or other purposes. A system in
Marstal, Denmark, includes a pit storage supplied with heat from a field
of solar-thermal panels. It is initially providing 20% of the
year-round heat for the village and is being expanded to provide twice
that. The world's largest pit store (200,000 m3 (7,000,000 cu ft)) was commissioned
in Vojens, Denmark, in 2015, and allows solar heat to provide 50% of
the annual energy for the world's largest solar-enabled district heating
system.
Large-scale thermal storage with water. Large scale STES water storage tanks can be built above ground, insulated, and then covered with soil.
Horizontal heat exchangers. For small installations, a heat exchanger of corrugated plastic pipe can be shallow-buried in a trench to create a STES.
Earth-bermed buildings. Stores heat passively in surrounding soil.
Salt hydrate technology This technology achieves significantly higher storage densities than water-based heat storage.
Conferences and organizations
The International Energy Agency'sEnergy Conservation through Energy Storage (ECES) Programme
has held triennial global energy conferences since 1981. The
conferences originally focused exclusively on STES, but now that those
technologies are mature other topics such as phase change materials (PCM)
and electrical energy storage are also being covered. Since 1985 each
conference has had "stock" (for storage) at the end of its name; e.g.
EcoStock, ThermaStock.
They are held at various locations around the world. Most recent were
InnoStock 2012 (the 12th International Conference on Thermal Energy
Storage) in Lleida, Spain and GreenStock 2015 in Beijing.
EnerStock 2018 will be held in Adana, Turkey in April 2018.
The IEA-ECES programme continues the work of the earlier International Council for Thermal Energy Storage
which from 1978 to 1990 had a quarterly newsletter and was initially
sponsored by the U.S. Department of Energy. The newsletter was initially
called ATES Newsletter, and after BTES became a feasible technology it was changed to STES Newsletter.
Use of STES for small, passively heated buildings
Small
passively heated buildings typically use the soil adjoining the
building as a low-temperature seasonal heat store that in the annual
cycle reaches a maximum temperature similar to average annual air
temperature, with the temperature drawn down for heating in colder
months. Such systems are a feature of building design, as some simple
but significant differences from 'traditional' buildings are necessary.
At a depth of about 20 feet (6 m) in the soil, the temperature is
naturally stable within a year-round range,
if the draw down does not exceed the natural capacity for solar
restoration of heat. Such storage systems operate within a narrow range
of storage temperatures over the course of a year, as opposed to the
other STES systems described above for which large annual temperature
differences are intended.
Two basic passive solar building technologies were developed in
the US during the 1970s and 1980s. They utilize direct heat conduction
to and from thermally isolated, moisture-protected soil as a seasonal
storage medium for space heating, with direct conduction as the heat
return method. In one method, "passive annual heat storage" (PAHS),
the building’s windows and other exterior surfaces capture solar heat
which is transferred by conduction through the floors, walls, and
sometimes the roof, into adjoining thermally buffered soil.
When the interior spaces are cooler than the storage medium, heat is conducted back to the living space.
The other method, “annualized geothermal solar” (AGS) uses a separate
solar collector to capture heat. The collected heat is delivered to a
storage device (soil, gravel bed or water tank) either passively by the
convection of the heat transfer medium (e.g. air or water) or actively
by pumping it. This method is usually implemented with a capacity
designed for six months of heating.
A number of examples of the use of solar thermal storage from across the world include: Suffolk One
a college in East Anglia, England, that uses a thermal collector of
pipe buried in the bus turning area to collect solar energy that is then
stored in 18 boreholes each 100 metres (330 ft) deep for use in winter
heating. Drake Landing Solar Community
in Canada uses solar thermal collectors on the garage roofs of 52
homes, which is then stored in an array of 35 metres (115 ft) deep
boreholes. The ground can reach temperatures in excess of 70 °C which is
then used to heat the houses passively. The scheme has been running
successfully since 2007. In Brædstrup,
Denmark, some 8,000 square metres (86,000 sq ft) of solar thermal
collectors are used to collect some 4,000,000 kWh/year similarly stored
in an array of 50 metres (160 ft) deep boreholes.
Liquid engineering
Architect Matyas Gutai obtained an EU grant to construct a house in Hungary
which uses extensive water filled wall panels as heat collectors and
reservoirs with underground heat storage water tanks. The design uses
microprocessor control.
Small buildings with internal STES water tanks
A
number of homes and small apartment buildings have demonstrated
combining a large internal water tank for heat storage with roof-mounted
solar-thermal collectors. Storage temperatures of 90 °C (194 °F) are
sufficient to supply both domestic hot water and space heating. The
first such house was MIT Solar House #1, in 1939. An eight-unit
apartment building in Oberburg, Switzerland was built in 1989, with three tanks storing a total of 118 m3
(4,167 cubic feet) that store more heat than the building requires.
Since 2011, that design is now being replicated in new buildings.
In Berlin, the “Zero Heating Energy House”, was built in 1997 in as part of the IEA Task 13 low energy housing demonstration project. It stores water at temperatures up to 90 °C (194 °F) inside a 20 m3 (706 cubic feet) tank in the basement.
A similar example was built in Ireland in 2009, as a prototype. The solar seasonal store consists of a 23 m3 (812 cu ft) tank, filled with water, which was installed in the ground, heavily insulated all around, to store heat from evacuated solar tubes during the year. The system was installed as an experiment to heat the world's first standardized pre-fabricated passive house in Galway, Ireland.
The aim was to find out if this heat would be sufficient to eliminate
the need for any electricity in the already highly efficient home during
the winter months.
Use of STES in greenhouses
STES is also used extensively for the heating of greenhouses.
ATES is the kind of storage commonly in use for this application. In
summer, the greenhouse is cooled with ground water, pumped from the
“cold well” in the aquifer. The water is heated in the process, and is
returned to the “warm well” in the aquifer. When the greenhouse needs
heat, such as to extend the growing season, water is withdrawn from the
warm well, becomes chilled while serving its heating function, and is
returned to the cold well. This is a very efficient system of free cooling, which uses only circulation pumps and no heat pumps.
Treatments for influenza include a range of medications and therapies that are used in response to disease influenza. Treatments may either directly target the influenza virus itself; or instead they may just offer relief to symptoms of the disease, while the body's own immune system works to recover from infection.
The two main classes of antiviral drugs used against influenza are neuraminidase inhibitors, such as zanamivir and oseltamivir, or inhibitors of the viral M2 protein, such as amantadine and rimantadine.
These drugs can reduce the severity of symptoms if taken soon after
infection and can also be taken to decrease the risk of infection.
However, virus strains have emerged that show drug resistance to both classes of drug.
Consult a physician early on for best possible treatment
Remain alert for emergency warning signs
Warning signs are symptoms that indicate that the disease is becoming
serious and needs immediate medical attention. These include:
Difficulty breathing or shortness of breath
Pain or pressure in the chest or abdomen
Dizziness
Confusion
Severe or persistent vomiting
In children other warning signs include irritability, failing to wake
up and interact, rapid breathing, and a blueish skin color. Another
warning sign in children is if the flu symptoms appear to resolve, but
then reappear with fever and a bad cough.
Antiviral drugs
Antiviral drugs
directly target the viruses responsible for influenza infections.
Generally, anti-viral drugs work optimally when taken within a few days
of the onset of symptoms. Certain drugs are used prophylactically, that is they are used in uninfected individuals to guard against infection.
Four licensed influenza antiviral agents are available in the United States: amantadine, rimantadine, zanamivir, and oseltamivir.
They are available through prescription only. These drugs fall into
categories as either M2-inhibitors (admantane derivatives) or
neuraminidase inhibitors as illustrated in the following table.
Note: Neuraminidase inhibitors are approved for prophylaxis use in children and adults.
In Russia and China a drug called arbidol
is also used as a treatment. Testing of the drug has predominantly
occurred in these countries and, although no clinical trials have been
published demonstrating this is an effective drug, some data suggest
that this could be a useful treatment for influenza.
Peramivir
Peramivir, an experimental anti-influenza drug, developed by BioCryst Pharmaceuticals has not yet been approved for sale in the United States.
This drug can be given as an injection, so may be particularly useful
in serious cases of influenza where the patient is unconscious and oral
or inhaled drug administration is therefore difficult.
In October 2009, it was reported that the experimental antiviral drugPeramivir had been effective in treating serious cases of swine flu. On October 23, the U.S. Food and Drug Administration (FDA) issued an Emergency Use Authorization
for Peramivir (now expired), leading to wider and faster availability
for patients. Since the FDA's decisions and actions are closely watched
around the world, this move is likely to also increase demand for
Peramivir internationally.
Interferons
Interferons
are cellular signalling factors produced in response to viral
infection. Research into the use of interferons to combat influenza
began in the 1960s in the Soviet Union, culminating in a trial of 14,000 subjects at the height of the Hong Kong Flu
of 1969, in which those treated prophylactically with interferon were
more than 50% less likely to suffer symptoms, though evidence of latent
infection was present. In these early studies leukocytes were collected from donated blood and exposed to a high dose of Newcastle disease,
causing them to release interferons. Although interferon therapies
became widespread in the Soviet Union, the method was doubted in the
United States after high doses of interferon proved ineffective in
trials. Though the 1969 study used 256 units of interferon, subsequent
studies used up to 8.4 million units. It has since been proposed that
activity of interferon is highest at low concentrations. Phase III trials in Australia are planned for 2010, and initial trials are planned in the U.S. for late 2009.
Interferons have also been investigated as adjuvants to enhance to effectiveness of influenza vaccines.
This work was based on experiments in mice that suggested that type I
interferons could enhance the effectiveness of influenza vaccines in
mice.
However, a clinical trial in 2008 found that oral dosing of elderly
patients with interferon-alpha actually reduced their immune response to
an influenza vaccine.
Viferon is a suppository of (non-pegylated) interferon alpha-2b, ascorbic acid (vitamin C), and tocopherol (vitamin E) which was reported in two small studies to be as effective as arbidol. It is sold in Russia for $4–$9 per suppository depending on dose.Another interferon alfa-2b medicine, "Grippferon", nasal drops, is used for treatment and emergency prevention of Influenza and cold. Its manufacturers have appealed to the WHO to consider its use against avian influenza
and H1N1 Influenza 09 (Human Swine Flu), stating that it was used
successfully in Russia for eight years, but that "the medical profession
in Europe and the USA is not informed about this medicine".
Drug resistance
Influenza viruses can show resistance to anti-viral drugs. Like the development of bacterial antibiotic resistance, this can result from over-use of these drugs. For example, a study published in the June 2009 Issue of Nature Biotechnology emphasized the urgent need for augmentation of oseltamivir (Tamiflu) stockpiles with additional antiviral drugs including zanamivir
(Relenza) based on an evaluation of the performance of these drugs in
the scenario that the 2009 H1N1 'Swine Flu' neuraminidase (NA) were to
acquire the tamiflu-resistance (His274Tyr) mutation which is currently
widespread in seasonal H1N1 strains.
Yet another example is in the case of the amantadines treatment may lead
to the rapid production of resistant viruses, and over-use of these
drugs has probably contributed to the spread of resistance.
In particular, this high-level of resistance may be due to the easy
availability of amantadines as part of over-the-counter cold remedies in
countries such as China and Russia, and their use to prevent outbreaks of influenza in farmed poultry.
On the other hand, a few strains resistant to neuraminidase
inhibitors have emerged and circulated in the absence of much use of the
drugs involved, and the frequency with which drug resistant strains
appears shows little correlation with the level of use of these drugs.
However, laboratory studies have shown that it is possible for the use
of sub-optimal doses of these drugs as a prophylactic measure might
contribute to the development of drug resistance.
During the United States 2005–2006 influenza season, increasing incidence of drug resistance by strain H3N2
to amantadine and rimantadine led the CDC to recommend oseltamivir as a
prophylactic drug, and the use of either oseltamivir or zanamivir as
treatment.
Over-the-counter medication
Antiviral drugs are prescription-only medication in the United States. Readily available over-the-counter medications do not directly affect the disease, but they do provide relief from influenza symptoms, as illustrated in the table below.
Children and teenagers with flu symptoms (particularly fever) should avoid taking aspirin as taking aspirin in the presence of influenza infection (especially Influenzavirus B) can lead to Reye's syndrome, a rare but potentially fatal disease of the brain.
Off-label uses of other drugs
Several generic prescription medications might prove useful to treat a potential H5N1 avian flu outbreak, including statins, fibrates, and chloroquine.
Nutritional supplements and herbal medicines
Malnutrition can reduce the ability of the body to resist infections and is a common cause of immunodeficiency in the developing world. For instance, in a study in Ecuador, micronutrient deficiencies were found to be common in the elderly, especially for vitamin C, vitamin D, vitamin B-6, vitamin B-12, folic acid, and zinc, and these are thought to weaken the immune system or cause anemia and thus place people at greater risk of respiratory infections such as influenza.
Seasonal variation in sunlight exposure, which is required for vitamin
D synthesis within the body, has been proposed as one of the factors
accounting for the seasonality of influenza.
A meta-analysis of 13 studies indicated some support for adjunctive
vitamin D therapy for influenza, but called for more rigorous clinical
trials to settle the issue conclusively.
The activity of N-acetylcysteine (NAC) against influenza was first suggested in 1966.
In 1997 a randomized clinical trial found that volunteers taking
1.2 grams of N-acetylcysteine daily for six months were as likely as
those taking placebo to be infected by influenza, but only 25% of them experienced clinical symptoms, as contrasted with 67% of the control group. The authors concluded that resistance to flu symptoms was associated with a shift in cell mediated immunity from anergy toward normoergy, as measured by the degree of skin reactivity to seven common antigens such as tetanus and Candida albicans.
Several animal studies found that in a mouse model of lethal
infection with a high dose of influenza, oral supplementation with one
gram of N-acetylcysteine per kilogram of body weight daily increased the
rate of survival, either when administered alone or in combination with
the antiviral drugs ribavirin or oseltamivir. NAC was shown to block or reduce cytopathic effects in influenza-infected macrophages, to reduce DNA fragmentation (apoptosis) in equine influenza-infected canine kidney cells, and to reduce RANTES production in cultured airway cells in response to influenza virus by 18%. The compound has been proposed for treatment of influenza.
Elderberry
A few news reports have suggested the use of an elderberry(Sambucus nigra) extract as a potential preventative against the 2009 flu pandemic. The preparation has been reported to reduce the duration of influenza symptoms by raising levels of cytokines.
However, the use of the preparation has been described as "imprudent"
when an influenza strain causes death in healthy adults by cytokine storm leading to primary viral pneumonia.
The manufacturer cites a lack of evidence for cytokine-related risks,
but labels the product only as an antioxidant and food supplement.
"Kan Jang"
The mixture of Eleutherococcus senticosus ("Siberian ginseng") and Andrographis paniculata, sold under the trade name Kan Jang, was reported in the Journal of Herbal Pharmacotherapy to outperform amantadine in reducing influenza-related sick time and complications in a Volgograd pilot study of 71 patients in 2003. Prior to this, an extract of Eleutherococcus senticosus was shown to inhibit replication of RNA but not DNA viruses in vitro. Among nine Chinese medicinal herbs tested, Andrographis paniculata was shown to be most effective in inhibiting RANTES secretion by H1N1 influenza infected cells in cell culture, with an IC50 for the ethanol extract of 1.2 milligrams per liter.
Green Tea
High dietary intake of green tea
(specifically, catechins and theanine that is found in tea products)
has been correlated with reduced risk of contracting influenza, as well
as having an antiviral effect upon types A and B.
Specifically, the high levels of epigallocatechin gallate, epicatechin
gallate, and epigallocatechin present in green tea were found to inhibit
influenza virus replication. Additionally, topical application has been suggested to possibly act as a mild disinfectant.
Regular dietary intake of green tea has been associated with stronger
immune response to infection, through the enhancement of T-Cell
function.
Passive immunity
Transfused antibodies
An alternative to vaccination used in the 1918 flu pandemic
was the direct transfusion of blood, plasma, or serum from recovered
patients. Though medical experiments of the era lacked some procedural
refinements, eight publications from 1918-1925 reported that the
treatment could approximately halve the mortality in hospitalized severe
cases with an average case-fatality rate of 37% when untreated.
Bovine colostrum might also serve as a source of antibodies for some applications.
Ex vivo culture of T lymphocytes
Human T lymphocytes can be expanded in vitro using beads holding specific antigens to activate the cells and stimulate growth. Clonal populations of CD8+ cytotoxic T cells have been grown which carry T cell receptors specific to influenza. These work much like antibodies but are permanently bound to these cells. (See cellular immunity).
High concentrations of N-acetylcysteine have been used to enhance
growth of these cells. This method is still in early research.
