Fact Sheet - Renewable Energy
Solar energy
Solar energy involves capturing and harnessing the sun’s energy. There are three main ways of doing this:
- Passive solar design ensures that a building’s form and fabric captures the sun’s energy and reduces the need for artificial light and heating.
- Active solar water heating converts solar radiation into heat, which can be used directly or stored.
- Solar photovoltaic (PV) panels or solar cells convert daylight into electricity.
How it works
Passive solar design
Passive solar design involves the application of design principles (such as south-facing windows) to make sure that excess heat loss is avoided and solar radiation is captured, in order to minimise the need for heating and lighting. The reverse is also true, so that minimising the capture of solar radiation, coupled with the use of natural ventilation, helps to reduce dependency on mechanical systems such as air conditioning.
Active solar water heating
Active solar water heating uses collectors, usually on the roof of a building, to capture and store the sun’s heat via water storage systems. The collectors provide heat to a fluid that circulates to a water tank. The heat is primarily used for heating water in domestic dwellings, industrial facilities and commercial buildings. This includes the growing market for solar swimming pool heaters.
Solar photovoltaics
Solar photovoltaics (PVs) convert energy from daylight into electricity using a semiconductor material such as silicon. When light hits the semiconductor, the energy in the light is absorbed, ‘exciting’ the electrons in the semiconductor so that they break free from their atoms. This allows the electrons to flow through the semiconductor material (in a similar manner to a normal electrical circuit) producing electricity.
There are a number of PV technologies, including polycrystalline, monocrystalline and thin-film. Solar PV cells can be arranged in panels on a building’s roof or walls, and can often directly feed electricity into the building. With the latest PV technology, cells can also be integrated into the roof tiles themselves.
Groups of solar PV cells can be added together to provide increasing levels of power. This can range from small, kilowatt-sized solar panels for use in domestic households, to larger arrays, which function as separate solar power plants feeding ower directly into the electricity grid.
Solar PV cells can be used in both stand-alone and grid-connected systems.
Solar energy is only produced during the day and also varies in output due to cloud cover. In the case of small-scale solar PV systems, batteries or other forms of electricity storage can be used to store the electricity for periods when the output is low but the demand is high. For solar thermal systems, the hot water can be stored for a limited period of time in well-insulated water tanks.
Current use in the UK
Passive solar design is a proven design approach that can reduce energy costs for buildings. In the UK, significant progress has been made in solar uptake in the non-domestic buildings sector. Uptake in the domestic sector has been slower. However, its application is expected to continue to grow as part of the practice of good building design.
A small, established market currently exists for active solar heating (also known as ‘solar thermal’ or ‘solar water heating’) in the UK, with fairly steady sales into the domestic and commercial sectors since the mid-1980s. Around 10,000 solar thermal systems are installed in the UK every year, and there are now over 100,000 systems in place.
In 2003, total capacity for solar photovoltaics (pv) in the UK was approximately 6 megawatts. This is a small proportion of its potential.
Under the Major Photovoltaics Demonstration Programme (PVMDP) there have been a number of installations given grant funding. These range from individual household installations to schools, social housing and a number of prominent buildings, including the London Transport Museum and the CIS Tower in Manchester, which, once complete, will be one of the largest PV installations in Europe . Remote locations are also ideally suited to PV installations and the PVMDP has supported installations in remote locations including the Island of Foula, Shetland's most westerly island. With a population of just 31, it is completely isolated from the national grid and must generate all its power locally. The grant was used to build a hybrid system that will provide 100 per cent of the island's power requirements through the use of a photovoltaic array fitted to the community hall roof and a hydro electric plant.
Likely contribution of solar to the renewables targets
Solar PV can deliver clean, silent electricity at point of use, and has the potential to meet a significant proportion of our electricity needs in the future. However, due to its current cost it is only likely to make a small contribution to the 2010 renewables target.
Future development
Indications are that the cost of PV systems are falling as the efficiency of solar panels increases and the cost of manufacturing declines due to the introduction of new technologies, such as thin-film solar PV. The DTI’s Renewables Innovation Review estimated that solar PV could become cost-competitive with other forms of electricity generation by 2020–30. The bottom end of the range indicates the case where solar panels are incorporated into buildings at the stage of construction, which is cheaper than retrofitting. This will increase the economic appeal of systems and the range of attractive applications. There are also thousands of PV systems currently in operation in the UK, meeting small power requirements in applications such as phone booths and roadside monitoring systems.
Solar energy in your community
Jobs
The solar technology industry is growing. The number of accredited photovoltaic (PV) installation companies has also risen from 7 in 2002 to 45 in 2004 (source: Renewable Power Association) and in 2004, Sharp, a new manufacturing facility, opened in Wrexham. As the technology improves, greater opportunities in R&D, construction and installation are expected.
Intrusion
Solar PV or active solar heating panels are typically placed on roofs, keeping visual intrusion to a minimum. New designs integrate solar panels into tiles and slates, effectively forming a direct part of a building’s roof.
In addition, solar systems do not have moving parts, making their operation virtually silent. This also means that they require little maintenance. They typically have lifetime performance of 20–25 years.
Pollution
Solar technologies produce no air pollution and emit little or no noise during operation.
Distribution
Because generation happens at the point of use, transmission and distribution costs, as well as negative environmental mpacts, are avoided.
Materials
There is some environmental concern over the use of heavy metals such as cadmium and lead in batteries used in some systems for storage purposes. Work is ongoing to replace these with more environmentally friendly alternatives and to make sure that if these types of batteries are used, they are recycled properly and not sent to landfill.
While the majority of existing solar PV cells are based on silicon, some of the newer thin-film technologies contain heavy metals, such as cadmium in cadmium telluride cells (CdTe). However, these are generally in minute quantities, and in the form of more environmentally stable compounds. It should also be noted that small quantities of some heavy metals including cadmium are released during combustion of coal. The use of cadmium in solar panels provides a purpose for taking potentially damaging cadmium, which is produced as a by-product of activities such as zinc mining, and converting it into a ore environmentally friendly form.
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 Wind
The use of wind as a renewable energy resource involves harnessing the power contained in moving air. Wind represents a vast source of energy that has already been harnessed for hundreds of years. The UK has the largest potential wind energy resource in Europe and wind power is currently one of the most developed and cost-effective renewable energy technologies.Wind turbines can be situated either onshore or offshore. Offshore wind is just beginning to be developed, but has enormous potential.
Can I install a wind turbine on my property?
Yes. Many people are now choosing to installed a small wind power system to help power their homes. However, there are several factors you will need to take into consideration, such as maintenance costs and where to site the turbine. The British Wind Energy Association (BWEA) provides useful information on where to start. You can visit the BWEA's website at www.bwea.com
Do I need planning permission?
If you are installing a small-scale wind system, it is possible that you may be able to proceed without the need for planning permission. However, there are a number of instances where planning permission may be required, r example if the micro-turbine will sit higher than the apex of the roof of your building. Therefore you should always contact your local district or borough council and speak to a planner before proceeding.
Where can I find out about grants?
The main source of funding for small-scale renewable installations is the Clear Skies programme (www.clear-skies.org). This national DTI-funded programme forms part of the Community Renewables Initiative. People based in Scotland should contact the Scottish Community and Householder Renewables Initiative at www.est.org.uk/schri.
The Energy Saving Trust website www.est.org.uk provides links to an online 'grant finder'. This allows you to search the grants you are eligible for, according to your circumstances and postcode.
How can I find and an approved installer?You can search a database of registered installers on the Clear kies programme website at www.clear-skies.org.
You can also search for BWEA members on the BWEA website at www.bwea.com.
How can I find out about wind farm developments in my area?
You can contact the BWEA or your local council. Alternatively, the Yes2Wind website at www.yes2wind.com has a wind farm locator facility.
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Wave and Tidal
Wave energy
As ocean waves are created by the interaction of wind with the surface of the sea, waves have the potential to provide an unlimited source of renewable energy. Wave energy can be extracted and converted into electricity by wave power machines. They can be deployed either on the shoreline or in deeper waters offshore.
Wave energy
How it works
There are three main types of wave power machines, some of which sit on the shoreline while others are free-floating:
Oscillating water column
An oscillating water column is a partially submerged, hollow structure that is installed in the ocean. It is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves cause the water column to rise and fall, which in turn compresses and depresses the air column. This trapped air is allowed to flow to and from the atmosphere via a Wells turbine, which has the ability to rotate in the same direction regardless of the direction of the airflow. The rotation of the turbine is used to generate electricity.
Buoyant moored device
A buoyant moored device floats on or just below the surface of the water and is moored to the sea floor. A wave power machine needs to resist the motion of the waves in order to generate power: part of the machine needs to move while another part remains still. In this type of device, the mooring is static and is arranged in such a way that the waves’ motion will move only one part of the machine.
Hinged contour device
A hinged contour device is able to operate at greater depths than the buoyant moored device. Here, the resistance to the waves is created by the alternate motion of the waves, which raises and lowers different sections of the machine relative to each other, pushing hydraulic fluid through hydraulic pumps to generate electricity.
The main problem with wave power is that the sea is a very harsh, unforgiving environment. An economically-viable wave power machine will need to generate power over a wide range of wave sizes, as well as being able to withstand the largest and most severe storms and other potential problems such as algae, barnacles and corrosion.
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Hydrogen
Hydrogen is an ‘energy carrier’ rather than a fuel source because it can only be produced using energy. It can be produced from fossil fuels such as natural gas or coal by the application of heat, but it can also be produced using renewable energy. Producing this would allow the whole of the energy chain to produce only low or even zero greenhouse gas emissions.
How it works
Hydrogen can be used in two main ways:
- in a fuel cell, where it produces zero emissions at the point of use in normal combustion, where it produces lower emissions of pollutants than fossil fuels.
Whether or not there are carbon emissions associated with the use of hydrogen depends upon how the hydrogen is itself produced.
Producing hydrogen from fuel cells
A fuel cell is an energy conversion device that uses an electrochemical process to convert hydrogen into electricity without combustion. It produces electricity with a conversion efficiency of up to 50 per cent. In a combined heat and power (CHP) installation, an overall efficiency of up to 80 per cent may be possible by utilising the heat that is also produced as a by-product of this process.
Fuel cells are not a new idea; the principle was discovered over 160 years ago. Until recently, their use was restricted to thelaboratory and in applications such as space travel. Fuel cells provided power for the Gemini and Apollo spacecraft, and still provide power for the space shuttles.
Potentially, fuel cells can be made in any size to power anything, from mobile phones to power plants. However, costs are between 10 and 100 times too high (depending on application) for them to compete with existing (albeit polluting) technologies. Possible applications include replacements for internal combustion engines for transport, powering portable devices, and electricity and heat for homes and buildings.
A fuel cell contains an anode and a cathode insulated by an electrolyte situated between them. Hydrogen is supplied to the anode while oxygen is supplied to the cathode. The two gases try to join, but because of the electrolyte, the hydrogen atom splits into a proton and an electron. The proton passes freely through the electrolyte. The electron takes a different route, creating an electric current before recombining with the hydrogen and oxygen, creating a molecule of water. This chemical rocess generates electrical and thermal energy but produces pure water as a by-product.
There are many different types of fuel-cell technology, with different characteristics such as power output and operating temperature, and each fuel-cell technology will only be suitable for certain types of application, for example large or small-scale stationary power generation, transport or portable battery replacement.
A fuel-cell system can utilise hydrogen from any source including hydrocarbon fuels, such as natural gas and methanol. However, emissions from this system can be lower than the cleanest method of normal fossil fuel combustion.
Producing hydrogen from renewable energy sources
There are numerous ways of producing hydrogen from renewable energy sources. It can be produced from a variety of biomass feedstocks, such as agricultural crops and wastes, sewage sludge or municipal solid waste, by thermochemical (pyrolysis or gasification) or biological processes that break down complex organic molecules into simpler molecules ncluding hydrogen.
Hydrogen can also be produced from renewably generated electricity, via electrolysis, to split water into hydrogen and oxygen. Wind and solar resources are much larger than biomass resources and it would be possible to produce electrolytic hydrogen in most parts of the UK. This provides a way of storing renewably generated electricity on a much larger scale than is currently possible with existing battery technology. As some renewable sources are intermittent (for example, electricity is only generated when the wind is blowing at certain speeds or if the sun is shining), the electrical energy can be converted to chemical energy in the form of stored hydrogen for use when renewable sources are not available. However, the efficiency of the best large-scale electrolysers is only about 70 per cent, and the subsequent conversion of hydrogen into electricity may not exceed 50 per cent.
Hydrogen energy in your community
Jobs
Hydrogen fuel-cell technology is expected to provide new opportunities for other key industry sectors, a platform for growth in high-value exports, and significant growth in knowledge-based jobs.
Emissions
The main emission from hydrogen fuel-cell vehicles is water and is therefore environmentally friendly. However, quantities of greenhouse gases and other pollutants associated with the production of hydrogen vary significantly. Key determining factors are the hydrogen production technology used and the primary source of fuel used for producing the hydrogen. Currently, most of the hydrogen used in fuel cells is produced from natural gas, which means continuing carbon dioxide emissions.
Groundwater contamination
Damaged or unused conventional vehicles can leak oil and other contaminants on the ground. The risk of this type of contamination is hugely reduced with renewable energy-sourced fuel-cell vehicles.
Noise Hydrogen fuel-cell vehicles are generally quieter than traditionally powered vehicles.
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Hydroelectric
Hydroelectric power is the energy derived from flowing water in rivers, or from man-made installations where water flows from a high-level reservoir down through a tunnel and away from the dam. Water power was used for centuries to power machinery, for example for grinding corn or in mills and factories, but was largely replaced by steam power in the Industrial Revolution. Water power is now mainly used to generate electrical energy.
How it works
Turbines placed within the flow of water extract its kinetic energy and convert it to mechanical energy. This causes the turbines to rotate at high speed. The turbines drive a generator that converts the mechanical energy into electrical energy. The amount of hydroelectric power that can be generated is related to the water flow and the vertical distance (known as ‘head’) through which the water has fallen.
In the smallest hydroelectric schemes, the head of water can be a few metres; in larger schemes, the power station that houses the turbines is often hundreds of metres below the reservoir.
Hydroelectric systems can be connected to the main electricity grid, or can be part of a stand-alone power system. In a rid-connected system, any electricity generated in excess of consumption on site can be ‘sold’ to electricity companies. In an off-grid hydroelectric system, electricity can be supplied directly to the user or via a battery bank.
There are three main types of hydroelectric schemes:
- storage schemes
- run-of-river schemes
- pumped storage.
In storage schemes, a dam impounds water in a reservoir that feeds the turbine and generator, usually located within the dam itself.Run-of-river schemes utilise the natural flow of a river, where the continuity of flow can be enhanced by a weir. Both storage and run-of-river schemes can be diversion schemes where water is channelled from a river, lake or dammed reservoir to a remote powerhouse containing the turbine and generator. A canal or low-pressure tunnel transports the water to this end point and then back to the river or to another watercourse.
Pumped storage incorporates two reservoirs. At times of low demand, generally at night, electricity is used to pump water from the lower to the upper basin. This water is then released to create power at a time when demand, and therefore price, is high. Pumped storage is not a renewable application as it is reliant upon an electricity supply and energy losses are always involved when pumping the water. However, by providing a rapid supply of electricity in response to sudden changes in demand, it does have value in aiding the overall efficiency of the generation infrastructure.
Tidal barrage systems can, like run-of-river schemes, use the incoming and outgoing tidal flow, or, like pumped storage chemes, store the incoming tidal flow in a reservoir to be released at low tide.
Hydroelectric energy in your community
Jobs
Large-scale hydroelectric schemes are usually built in remote areas away from centres of population. They can be a valuable source of employment to the area during construction and operation.
Recreation The creation of a reservoir can offer recreational and tourist opportunities.
Intrusion
Small-scale hydroelectric schemes in particular are quiet and visually unobtrusive. Large-scale hydroelectric projects cause an increase in traffic during the construction phase, which can be long and very noisy.
Visual impact
Most hydropower schemes can add positively to the visual environment, although some dams and eroded reservoir shorelines can have a negative visual impact.
Cost
For houses with no mains connection, but with access to a micro-hydro site, a good hydroelectric system can generate a steady, reliable electricity supply at a lower cost than other renewable technologies. Though still quite high, total system costsare often less than the cost of a grid connection, with no electricity bills to follow. Micro-hydro schemes have proved useful for powering remote domestic communities and as part of development projects in less developed countries.
Public attitudes
Most participants in a DTI renewable energy survey had heard of hydroelectric power but had little understanding of how it worked. Hydroelectric power was accepted as an established method of supplying energy. There were no negative views on this source of energy and some considered hydroelectric schemes as tourist attractions. For instance, the Pitlochry hydropower plant is one of the top 10 visitor attractions in Scotland. Some referred to watermills producing energy and the fact that this method of generating power has historic roots. Participants were concerned about the social impact of hydroelectric schemes, particularly if such schemes required the flooding of valleys, and were opposed to hydroelectric schemes under such circumstances.River ecology
Hydroelectric power schemes need an abstraction licence from the Environment Agency. Under this licence, the effect of the turbine on a river’s ecosystem will be investigated. The river’s ecology is protected by restricting the proportion of the total flow diverted through the turbine. Large hydroelectric power schemes may include fish ladders to allow migrating salmon and sea trout to pass into the upper river to spawn.
Energy balance
With small-scale hydroelectric schemes, the embodied energy of a scheme (the energy used in the manufacture of the components and construction) is typically equalled by the energy generated by the scheme within nine months of commissioning.
EmissionsEmissions are not a problem on small-scale schemes. In larger schemes that have involved flooding, some carbon dioxide emissions may come from decaying vegetation in the short term.
Noise
Turbines can produce some noise but this can be mitigated relatively easily.
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Biomass
Biomass, also known as biofuels or bioenergy, is obtained from organic matter, either directly from plants or indirectly from industrial, commercial, domestic or agricultural products.The use of biomass is generally classed as a ‘carbon-neutral’ process because the carbon dioxide released during the generation of energy is balanced by that absorbed by plants during their growth. However, it is important to account for any other energy inputs that may affect this carbon-neutral balance on a case-by-case basis, for example any use of fertiliser, or energy consumed in vehicles when harvesting or transporting t Biomass falls into three main groups:
- Dependent resources: These are the co-products and waste generated from agricultural, industrial and commercial processes. This includes forest products, waste wood, straw, slurry, chicken litter and industrial and municipal wastes (such as food processing wastes). For example, for every tonne of wheat harvested, a certain amount of ‘waste’ straw is created, or for every tree felled to make furniture, a certain percentage cannot be used. These co-products can be utilisedas biomass fuels, for example, in combustion.
- Dedicated energy crops: These are short-rotation crops, such as coppice, miscanthus, willow and poplar, which are grown specifically to generate biomass fuel.
- Multi-functional crops: These are crops that can be used to create different types of energy. For example, the ears of wheat can be used to create fuel (including bioethanol and biodiesel), while straw can be used to generate electricity.
Biomass can be converted into heat and electricity in a number of ways. Depending on its source, these processes include burning, pyrolysis (the decomposition or transformation of a compound caused by heat), gasification (the conversion of solid biomass into a gaseous fuel), anaerobic digestion (the decomposition of an organic biodegradable material by bacterial ction in the absence of air, and in warm, moist conditions) or fermentation.
Woody biomass
Energy can be derived from woody biomass sources (including forest products, waste wood and straw) using combustion systems, which can be used to heat anything from a domestic stove or hot water system to an entire community. Biomass can also be used on its own or by co-firing it with fossil fuels in power stations, reducing greenhouse gas emissions by replacing a component of the fossil fuel required. In industrial or agricultural use, boilers fuelled by woody biomass such as cardboard, wood and waste pellets or straw can help reduce waste removal costs.
Biogas, landfill gas and fermentation harness the natural process of anaerobic digestion.
Biogas
Biogas is generated from concentrations of sewage or manure. These are usually in the form of slurry comprising mostly ater (almost 95 per cent). The slurry is fed into a digester, either continuously or in batches. Digestion takes from about 10 days up to several weeks, at a temperature of 35°C.
Landfill gas
Landfill gas arises from waste deposited underground in landfill sites. Biodegradable organic waste decomposes anaerobically to produce a gas that is roughly an even mixture of carbon dioxide and methane. The methane content gives it the potential as a fuel, which can then be used to generate electricity or to provide process heat. The amount of gas available from a landfill site depends on the type of waste, moisture content, temperature, acidity of the waste and the design of the site. Gas is drawn up from vertical or horizontal wells through a system of pipes. The generating equipment is usually contained within the same area as the extraction plant.
Fermentation
Fermentation occurs when anaerobic digestion converts sugars into ethanol with the use of micro-organisms, usually yeast. Bioethanol can be used as a transport fuel by mixing it with petrol or using it directly in a modified combustion engine. Sugar cane or beet is the most efficient source but potatoes, corn, wheat and barley can also be used. Processes that produce bioethanol from woody material, such as forestry residues, energy crops and waste paper, are also approaching commercial viability and a number of pilot plants are proposed for the UK.
Biodiesel can be made from vegetable oils, animal fats or recycled cooking oils. However, the production of biodiesel requires a high amount of energy, offsetting its ability to reduce carbon emissions. However, it still provides an improvement over fossil fuels, typically reducing lifecycle carbon dioxide emissions by over 60 per cent.
Many biomass facilities are relatively small-scale and therefore have few impacts on the local community.
Jobs
Biomass offers the greatest potential for job creation among all the renewable technologies. A switch from traditional food crop production to non-food biomass production can potentially help reduce the decline of jobs in agricultural regions. It is estimated that Europe-wide, over 300,000 jobs could be created from biomass fuel production by 2020 (source: EC Altener study).
Revenue
Extra revenue from selling energy, fertiliser and fibre products can have a positive effect on rural development.
Odours Anaerobic digestion treatment stabilises slurries, significantly reducing odours, improving working conditions and lessening nuisance for neighbours.
Public attitudes
A DTI-commissioned survey of the public attitude to renewable energy showed that few participants had heard of the term biomass. Even those who lived near to biomass plants were unfamiliar with it. Participants found it difficult to distinguish between biomass and incineration, and did not see biomass as environmentally friendly. There was also confusion as to whether biomass plants could burn household waste and concern that burning animal waste would be odorous. Participants were concerned about lorries bringing material to the plant, and about emissions and odours from biomass plants themselves.
Overall impactThe use of biomass has largely positive implications for the environment due to its carbon-neutral status. However, there are also issues, described below, which need to be carefully considered to avoid any potentially negative impacts.
Production
Although woody biomass such as forest products, short-rotation coppice, untreated wood products, straw and energy crops require production, handling and processing, these resources are generally considered to be sustainable, especially when sourced within the UK.
Transportation
The transportation of materials to the plants by lorry can cause some pollution and disruption, although this can be minimised by scheduling freight transport at less disruptive times of day.
Visual impact The introduction of unfamiliar crops and the potential for mono-cultural planting schemes, as well as the subsequent effects on the local ecosystem, need to be considered.
Emissions
Anaerobic digestion schemes capture gases such as methane for use as a fuel which otherwise, under current disposal practice, would be released into the atmosphere.
Residues
A properly-managed anaerobic digestion scheme contains nutrients found in animal slurries and food residues that can otherwise leach out in high concentrations and pollute soil and water courses. The by-products arising from anaerobic digesters have value as a fertiliser and soil improver. Incombustible materials such as ash created under incineration schemes also have to be removed. However, ash arising from the combustion of wood fuels can also have value as a fertiliser.
By-products
Combustion chambers used for the combustion of biomass need to be well managed to ensure that by-products such as particulates and polyaromatic hydrocarbons cannot escape to the atmosphere.
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Geothermal
Geothermal energy involves the exploitation of different grades of thermal energy stored within the earth.
In certain geological areas, heat from deep within the earth’s interior can rise up to the surface. Whenever water enters fissures in this hot rock, it can become heated and can emerge on the surface as hot springs, or even as steam, creating eatures such as steam vents, geysers and hot mud springs. Alternatively, heated water can be trapped below the earth’s surface as a geothermal reservoir. This heat can reach temperatures of 400°C. It can be accessed by drilling to depths of over two miles.
Ground-source heat is a different form of geothermal energy. It is extracted from the low-temperature heat (10–20°C) that is found at relatively shallow depths within the earth’s crust. This source of heat remains at a relatively constant temperature all year and can be taken from the ground itself or from groundwater. Heat pumps can increase the temperature to provide a more useful output temperature of around 40–50°C, ideal for low-temperature heating systems like under floor systems and radiant panels. How it works
Geothermal energy can be used directly to provide heating. Alternatively, geothermal power plants can access steam, heat or hot water from geothermal reservoirs, which can be used to turn generators and produce electricity. After the geothermal energy has been extracted from the water, the water is returned down the well into the reservoir and reheated. There are several types of geothermal power plant available, depending on the temperature and pressure of the geothermal source.
Ground-source heat pumps are not strictly a renewable source of energy, because they require electricity to extract and make use of low-grade heat. However, there is no reason why this electricity could not be generated by another form of renewable energy. Heat pumps can be very energy efficient, producing four or five times the amount of heat energy for every unit of electrical energy needed. A heat pump takes the heat from a refrigerant fluid (or water) that is in contact with the ground, extracts the heat from this source and transfers it to a heat sink where it can then be circulated through a heating system. Although the refrigerant fluid is cooled by this process, it can be re-circulated back through the ground where it willabsorb more heat before being passed through the heat pump again.
Heat pumps do not produce electricity; however, they can provide heating and can be operated in reverse to provide cooling. They can be used in most kinds of building and have both domestic and commercial applicati Geothermal
Current use in the UK
There is only one geothermal power plant in operation in the UK, in Southampton. Ground-source heat pumps were first popular in the early 1980s, when electricity was cheaper than gas. They are now becoming more popular, with an increasing number of heat pumps installed throughout the UK in homes, commercial buildings and swimming pools. This is because of their energy-efficient status and due to the fact that gas prices are once more beginning to rise relative to electricity prices.There are currently around 250 ground-source heat pumps installed in the UK every year. Since 1992 around 3,000 heat pumps have been installed in single family homes.
Future development
It has been estimated that there are 1,550 large industrial sites in the UK where heat-pump systems could be installed, with an average size of 800 kilowatts of thermal power. There is more limited potential for further geothermal plants in the UK as sites need hot rock relatively near to the surface and which is sufficiently fractured to allow the passage of (heated) water. There are areas of hot rocks in the North Pennines, parts of southern England and Derbyshire.
Geothermal energy in your community
Public buildings
Ground-source heat pumps are especially suitable for buildings that have a demand for heating and cooling and have long ours of usage, such as hotels and hospitals. A heat-pump system becomes more efficient with use when compared with a conventional fossil-fuel system.
Visual impact
The technology used in ground-source heating systems has very low visual impact and most of the infrastructure can be hidden beneath the ground. Heat pumps can be housed within existing buildings.
Viability
Not every area is suitable for geothermal energy, and the UK has a far more limited resource compared with other countries such as Iceland or New Zealand. Heat pumps require access to sufficient areas of ground surrounding the development or to suitable, proximal bodies of water and groundwater. Lakes, canals and tidal mudflats are potential sources of heat for heat pumps. Areas underlain by aquifers are particularly suited to large ground-source heat schemes.Gas emissions
Geothermal fluids contain dissolved gases. When these gases are brought to the surface, a reduction in pressure can allow them to be released from the solution. The gases typically contained in geothermal fluids are carbon dioxide (CO2) and hydrogen sulphide (H2S). Geothermal plants do not produce any oxides of nitrogen (NOx) or sulphur dioxide (SO2). They also produce much less carbon dioxide than gas, coal or oil-fired plants.
Land use
Geothermal power plants require relatively little space. Rivers do not need to be dammed and forests do not need to be cut down. Exploitation of geothermal energy does not create any mineshafts, tunnels, open pits, waste heaps or oil spills. Geothermal plants can sit among potentially sensitive developments such as farmland and forests and can share land with cattle and local wildlife.Noise
Heat-pump installations are unobtrusive and noise- and pollution-free. If the compressor is driven by fossil fuel-generated electricity, they will release some carbon dioxide. However, they have lower emissions than conventional gas or oil boilers and the power required to drive the heat pump could be sourced from renewable technologies.
Source - DTI
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