Green energy practices -
However, the variability of wind and solar power does not correspond with most demand, and as substantial capacity has been built in several countries in response to government incentives, occasional massive output — as well as occasional zero output — from these sources creates major problems in maintaining the reliability and economic viability of the whole system.
There is a new focus on system costs related to achieving reliable supply to meet demand. In the following text, the levelised cost of electricity LCOE is used to indicate the average cost per unit of electricity generated at the actual plant, allowing for the recovery of all costs over the lifetime of the plant.
It includes capital, financing, operation and maintenance, fuel if any , and decommissioning. Another relevant metric is energy return on energy invested EROI.
This is not quoted for particular projects, but is the subject of more general studies. EROI is the ratio of the energy delivered by a process to the energy used directly and indirectly in that process, and is part of lifecycle analysis LCA.
An EROI of about 7 is considered break-even economically for developed countries. The US average EROI across all generating technologies is about A fuller account of EROI in electricity generation is in the information paper on Energy Return on Investment.
The World Energy Outlook WEO made the points that VRE have five technical properties that make them distinct from more traditional forms of power generation.
First, their maximum output fluctuates according to the real-time availability of wind and sunlight. Second, such fluctuations can be predicted accurately only a few hours to days in advance. Third, they are non-synchronous and use devices known as power converters in order to connect to the grid this can be relevant in terms of how to ensure the stability of power systems.
Fourth, they are more modular and can be deployed in a much more distributed fashion. Fifth, unlike fossil or nuclear fuels, wind and sunlight cannot be transported, and while renewable energy resources are available in many areas, the best resources are frequently located at a distance from load centres thus, in some cases, increasing connection costs.
These points are more fully put forward and modelled in the OECD Nuclear Energy Agency NEA publication, The Costs of Decarbonization: System Costs with High Shares of Nuclear and Renewables. All the modelling is within a 50g CO 2 per kWh emission constraint, and quantifies the system costs due to different levels of VRE input, despite declining LCOE costs and zero marginal costs for those.
The concept of system effects, which are heavily driven by the attributes of VRE listed above, has been conceptualised and explored extensively by both the OECD International Energy Agency IEA and the NEA along with research from academia, industry and governments. System effects are often divided into the following four broadly defined categories:.
The NEA study states: "Profile costs or utilisation costs refer to the increase in the generation cost of the overall electricity system in response to the variablity of VRE output.
They are thus at the heart of the notion of system effects. They capture, in particular, the fact that in most of the cases it is more expensive to provide the residual load in a system with VRE than in an equivalent system where VRE are replaced by dispatchable plants.
High levels of VRE require significant enhancement of system integration measures. These measures include flexible power sources such as hydro and open cycle gas turbines, demand-side measures, electricity storage, strong and smart transmission and distribution grids.
The costs of all these, over and above the generation costs, comprise the system costs. See later section on System integration costs of intermittent renewable power generation. A further aspect of considering sources such as wind and solar in the context of grid supply is that their true capacity is discounted to allow for intermittency.
In the UK this is by a factor of 0. This novel convention is not followed in this information paper. There is a fundamental attractiveness about harnessing such forces in an age which is very conscious of the environmental effects of burning fossil fuels, and where sustainability is an ethical norm.
So today the focus is on both adequacy of energy supply long-term and also the environmental implications of particular sources.
In that regard, the costs being imposed on CO 2 emissions in developed countries at least have profoundly changed the economic outlook of clean energy sources. A market-determined carbon price creates incentives for energy sources that are cleaner than current fossil fuel sources without distinguishing among different technologies.
This puts the onus on the generating utility to employ technologies which efficiently supply power to the consumer at a competitive price.
Wind, solar and nuclear are the main contenders. Sun, wind, waves, rivers, tides and the heat from radioactive decay in the earth's mantle as well as biomass are all abundant and ongoing, hence the term "renewables". Solar energy's main human application has been in agriculture and forestry, via photosynthesis, and increasingly it is harnessed for heat.
Until recently electricity has been a niche application for solar. Biomass e. sugar cane residue is burned where it can be utilised, but there are serious questions regarding wider usage. The others are little used as yet. Turning to the use of abundant renewable energy sources other than large-scale hydro for electricity, there are challenges in actually harnessing them.
Apart from solar photovoltaic PV systems which produce electricity directly, the question is how to make them turn dynamos to generate the electricity. If it is heat which is harnessed, this is via a steam generating system.
This means either that there must be reliable duplicate sources of electricity beyond the normal system reserve, or some means of large-scale electricity storage see later section. Policies which favour renewables over other sources may also be required. Such policies, now in place in about 50 countries, include priority dispatch for electricity from renewable sources and special feed-in tariffs, quota obligations and energy tax exemptions.
The role of India and China INDCs is noteworthy here. Regarding solar capacity, India pledged GWe and China GWe by on top of present world GWe. Regarding wind, China pledged GWe and India 78 GWe capacity by on top of world capacity.
This load curve diagram shows that much of the electricity demand is in fact for continuous supply base-load , while some is for a lesser amount of predictable supply for about three-quarters of the day, and less still for variable peak demand up to half of the time; some of the overnight demand is for domestic hot water systems on cheap tariffs.
With overnight charging of electric vehicles it is easy to see how the base-load proportion would grow, increasing the scope for nuclear and other plants which produce it.
Source: Vencorp. Most electricity demand is for continuous, reliable supply that has traditionally been provided by base-load electricity generation. Some is for shorter-term e.
peak-load requirements on a broadly predictable daily and weekly basis. Hence if renewable sources are linked to a grid, the question of back-up capacity arises; for a stand-alone system, energy storage is the main issue.
Apart from pumped-storage hydro systems see later section , no such means exist at present on any large scale. However, a distinct advantage of solar and to some extent other renewable systems is that they are distributed and may be near the points of demand, thereby reducing power transmission losses if traditional generating plants are distant.
Of course, this same feature more often counts against wind in that the best sites for harnessing it are sometimes remote from populations, and the main back-up for lack of wind in one place is wind blowing hard in another, hence requiring a wide network with flexible operation.
Hydroelectric power, using the potential energy of rivers, is by far the best-established means of electricity generation from renewable sources. It may also be large-scale — nine of the ten largest power plants in the world are hydro, using dams on rivers.
In contrast to wind and solar generation, hydro plants have considerable mechanical inertia and are synchronous, helping with grid stability. Half of hydro capacity is in five nations: China GWe , USA 84 GWe , Brazil GWe , Canada 81 GWe , and Russia 54 GWe.
Apart from those five countries with a relative abundance of it Norway, Canada, Switzerland, New Zealand and Sweden , hydro capacity is normally applied to peak-load demand, because it is so readily stopped and started.
The individual turbines of a hydro plant can be run up from zero to full power in about ten minutes. This also means that it is an ideal complement to wind power in a grid system, and is used thus most effectively by Denmark see case study below.
Hydropower using large storage reservoirs on rivers is not a major option for the future in the developed countries because most major sites in these countries having potential for harnessing gravity in this way are either being exploited already or are unavailable for other reasons such as environmental considerations.
Growth to is expected mostly in China and Latin America. Brazil is planning to have 25 GWe of new hydro capacity by , involving considerable environmental impact. The chief advantage of hydro systems is their capacity to handle seasonal as well as daily high peak loads.
In practice the utilisation of stored water is sometimes complicated by demands for irrigation which may occur out of phase with peak electrical demands. Hydroelectric power plants can constrain the water flow through each turbine to vary output, though with fixed-blade turbines this reduces generating efficiency.
More sophisticated and expensive Kaplan turbines have variable pitch and are efficient at a range of flow rates. With multiple fixed-blade turbines e. Francis turbine , they can individually be run at full power or shut down.
Run-of-river hydro systems are usually much smaller than dammed ones but have potentially wider application. Some short-term pondage can help them adapt to daily load profiles, but generally they produce continuously, apart from seasonal variation in river flows.
Pumped storage is discussed below under Renewables in relation to base-load demand. In the 'Stated Policies' scenario of the International Energy Agency's IEA's World Energy Outlook , some GWe of wind capacity would be operational in , producing TWh, and in the 'Sustainable Development' scenario, there would be GWe producing TWh i.
IRENA statistics show GWe onshore and 34 GWe offshore installed in , up from GWe in when TWh was produced. Wind turbines of up to 6 MWe are now functioning in many countries.
A prototype 8 MWe unit built by Siemens Gamesa with a metre rotor diameter was commissioned in Denmark early in The average size of new turbines installed in was 5. The turbine will be metres tall from base to blade tip with a rotor diameter of metres. The power output is a function of the cube of the wind speed, so doubling the wind speed gives eight times the energy potential.
Larger ones are on taller pylons and tend to have higher capacity factors. Where there is an economic back-up which can be called upon at very short notice e. hydro , a significant proportion of electricity can be provided from wind.
There is a distinct difference between onshore and offshore sites, though the latter are more expensive to set up and run. Green Rigg wind farm in the UK Image: EDF Energy.
In Germany, with high dependence on wind, there is corresponding high uncertainty of supply. Stage 1 is 2. It is auctioning MWe per year to With increased scale and numbers of units, generation costs and levelised cost of energy LCOE is now often competitive with coal and nuclear, without allowing for backup capacity and grid connection complexities which affect their value in a system.
Wind is intermittent, and when it does not blow, backup capacity such as hydro or quick-start gas is needed. When it does blow, and displaces power from other sources, it may reduce the profitability of those sources and may increase delivered prices.
With any significant input from intermittent renewables sources, system cost not the LCOE to meet actual demand becomes the relevant metric. One approach to mitigate intermittency is to make hydrogen by electrolysis and feed this into the gas grid, the power-to-gas strategy. It has been suggested that all electricity from wind might be used thus, greatly simplifying electrical grid management.
Vattenfall at Prenzlau in Germany is also experimenting with hydrogen production and storage from wind power via electrolysis. Also in Germany, near Neubrandenburg in the northeast, WIND-projekt is using surplus electricity from a MWe wind farm to make hydrogen, storing it, and then burning it in a CHP unit to make electricity when demand is high.
RWE and Siemens plan a MW power-to-gas pilot project, GET H2, at Lingen, using wind power, and two other similar projects are planned: Element Eins and Hybridge.
In the Netherlands, Gasunie plans a 20 MW unit. BNetzA forecasts a 3 GW potential for power-to-gas by Wind turbines have a high steel tower to mount the generator nacelle, and typically have rotors with three blades. Foundations require a substantial mass of reinforced concrete.
Hence the energy inputs to manufacture are not insignificant. Also siting is important in getting a net gain from them. Bird kills, especially of raptor species, are an environmental impact of wind farms.
In the USA half a million birds are killed each year, including 83, raptors hawks, eagles, falcons etc. according to reports of a peer-reviewed published estimate in Wildlife Society Bulletin. According to Environment Canada, wind turbines kill approximately 8.
Migratory bats are also killed in large numbers. New wind farms are increasingly offshore, in shallow seas. The UK had MWe wind capacity offshore at the end of , over two-thirds of the world's total.
The London Array, 20 km offshore Kent, has turbines of 3. Replacing old turbines is becoming an issue — repowering the wind capacity. Approximately half of European capacity will be retired by , and needs to be replaced mostly with larger turbines, likely without subsidies.
The repowering priority is at the best sites. Full decommissioning involves removal of old towers and foundations, not simply turbines. According to lobby group WindEurope, some 22 GWe of wind turbines over 20 years old in Europe will be decommissioned by , and 40 GWe by At least one-fifth of these will involve full decommissioning.
A Renewable Energy Foundation study in showed that the performance of onshore wind turbines in the UK and Denmark declined significantly with age, and offshore Danish ones declined more. Solar energy is readily harnessed for low temperature heat, and in many places domestic hot water units with storage routinely utilise it.
It is also used simply by sensible design of buildings and in many ways that are taken for granted. Industrially, probably the main use is in solar salt production — some PJ per year in Australia alone equivalent to two-thirds of the nation's oil use. It is increasingly used in utility-scale plants, mostly photovoltaic PV.
Domestic-scale PV is widespread. IRENA statistics show GWe solar capacity of which Three methods of converting the Sun's radiant energy to electricity are the focus of attention. The best-known method utilises light, ideally sunlight, acting on photovoltaic cells to produce electricity.
Flat plate versions of these can readily be mounted on buildings without any aesthetic intrusion or requiring special support structures. Solar photovoltaic PV has for some years had application for certain signaling and communication equipment, such as remote area telecommunications equipment in Australia or simply where mains connection is inconvenient.
Sales of solar PV modules are increasing strongly as their efficiency increases and price falls, coupled with financial subsidies and incentives. Small-scale solar PV installations for domestic or onsite industrial use are commonly 'behind the meter', and may feed surplus power into the grid. Many large-scale solar PV power plants in Europe and the USA, and now China are set up to supply electricity grids.
In recent years there has been high investment in solar PV, due to favourable subsidies and incentives. In there was GWe installed worldwide according to the International Renewable Energy Agency IRENA , up from GWe in , GWe in , and GWe in — a doubling of capacity in three years.
More efficiency can be gained using concentrating solar PV CPV , where some kind of parabolic mirror tracks the sun and increases the intensity of the solar radiation up to fold.
Modules are typically kW. In the USA Boeing has licensed its XR high-concentration PV HCPV technology to Stirling Energy Systems with a view to commercializing it for plants under 50 MWe from The HCPV cells in achieved a world record for terrestrial concentrator solar cell efficiency, at CPV can also be used with heliostat configuration, with a tower among a field of mirrors.
In several Californian plants planned for solar thermal changed plans to solar PV — see mention of Blythe, Imperial Valley and Calico below. In China commissioned a 2. Storage capacity of MWh is claimed. The Indian government announced the 4 GWe Sambhar project in Rajasthan in , expected to produce 6.
The 2. EdF has built the MWe Toul-Rosieres thin-film PV plant in eastern France. There is a 97 MWe Sarnia plant in Canada. MidAmerican Solar owns the MWe Topaz Solar Farms in San Luis Obispo County, Calif. Research continues into ways to make the actual solar collecting cells less expensive and more efficient.
In some systems there is provision for feeding surplus PV power from domestic systems into the grid as contra to normal supply from it, which enhances the economics.
The MWe Ordos thin-film solar PV plant is planned in Inner Mongolia, China, with four phases — 30, , , MWe — to be complete in Over 30 others planned are over MWe, most in India, China, USA and Australia. A MWe solar PV plant is planned at Setouchi in Japan, with GE taking a major stake in the JPY 80 billion project expected on line in A feed-in tariff regime will support this.
The particular battery system required is designed specifically to control the rate of ramp up and ramp down. System life is ten years, compared with twice that for most renewable sources.
The manufacturing and recycling of PV modules raises a number of questions regarding both scarce commodities, and health and environmental issues. Copper indium gallium selenide CIGS solar cells are a particular concern, both for manufacturing and recycling. Silicon-based PV modules require high energy input in manufacture, though the silicon itself is abundant.
The International Renewable Energy Agency IRENA in estimated that there would be about 8 million tonnes of solar PV waste by , and that the total could reach 78 million tonnes by Recycling solar PV panels is generally not economic, and there is concern about cadmium leaching from discarded panels.
Some recycling is undertaken. Solar thermal systems need sunlight rather than the more diffuse light which can be harnessed by solar PV.
They are not viable in high latitudes. A solar thermal power plant has a system of mirrors to concentrate the sunlight on to an absorber, the energy then being used to drive steam turbines — concentrating solar thermal power CSP.
Many systems have some heat storage capacity in molten salt to enable generation after sundown, and possibly overnight. In there was about 6. World capacity was 5. The concentrator may be a parabolic mirror trough oriented north-south, which tracks the sun's path through the day.
The absorber is located at the focal point and converts the solar radiation to heat in a fluid such as synthetic oil, which may reach °C. The fluid transfers heat to a secondary circuit producing steam to drive a conventional turbine and generator.
Several such installations in modules of up to 80 MW are now operating. Each module requires about 50 hectares of land and needs very precise engineering and control. These plants are supplemented by a gas-fired boiler which generates about a quarter of the overall power output and keeps them warm overnight, especially if molten salt heat storage is used, as in many CSP power tower plants.
A simpler CSP concept is the linear Fresnel collector using rows of long narrow flat or slightly curved mirrors tracking the sun and reflecting on to one or more fixed linear receivers positioned above them. The receivers may generate steam directly. In mid Nevada Solar One, a 64 MWe capacity solar thermal energy plant, started up.
The plant was projected to produce GWh per year and covers about hectares with mirrored troughs that concentrate the heat from the desert sun onto pipes that contain a heat transfer fluid. This is heated to °C and then produces steam to drive turbines. Nine similar units totaling MWe have been operating in California as the Solar Energy Generating Systems.
More than twenty Spanish 50 MWe parabolic trough units including Andasol , Alvarado 1, Extresol , Ibersol and Solnova , Palma del Rio , Manchasol , Valle , commenced operation in Andasol, Manchasol and Valle have 7.
Other US CSP parabolic trough projects include Abengoa's Solana in Arizona, a MWe project with six-hour molten salt storage enabling power generation in the evening.
It has a ha solar field and started operation in Abengoa's MWe Mojave Solar Project near Barstow in California also uses parabolic troughs in a ha solar field and came online in It has no heat storage.
However, this became a solar PV project, apparently due to difficulty in raising finance. Another form of this CSP is the power tower , with a set of flat mirrors heliostats which track the sun and focus heat on the top of a tower, heating water to make steam, or molten salt to °C and using this both to store the heat and produce steam for a turbine.
Solucar also has three parabolic trough plants of 50 MW each. Power production in the evening can be extended fairly readily using gas combustion for heat. It comprises three CSP Luz power towers which simply heat water to °C to make steam, using , heliostat mirrors in pairs each of 14 m 2 per MWe, in operation from as the world's largest CSP plant.
The steam cycle uses air-cooled condensers. There is a back-up gas turbine, and natural gas is used to pre-heat water in the towers. It burned TJ of gas in , TJ in and TJ in EIA data which resulted in 46, tonnes of CO 2 emissions in , 66, t in and 68, t in The plant is owned by BrightSource, NRG Energy and Google.
BrightSource estimates that annual bird kill is about from incineration, federal biologists have higher estimates — the plant is on a migratory route. BrightSource plans a similar MWe plant nearby in the Coachella Valley. Another MWe Ashalim plant developed by Negev Energy uses parabolic troughs and was also commissioned in Further phases of the project will involve solar PV.
Using molten salt in the CSP system as the transfer fluid which also stores heat, enables operation into the evening, thus approximating to much of the daily load demand profile. Spain's MWe Andasol plant stores heat at °C and requires 75 t of salt per MW of heat.
It also uses diphenol oxide or oil for heat transfer and molten salt for heat storage. Spain's Gemasolar employs tonnes of salt for both heat transfer and storage. California's MWe Solana uses , tonnes of salt, kept at °C. SolarReserve filed for bankruptcy in An MWe plant occupying 13 km 2 with six power towers is being built in Qinghai province in northwest China, by BrightSource with Shanghai Electric Group.
It will have heat storage using molten salt. Phase 1 of this Qinghai Delingha Solar Thermal Power Project is two MWe CSP plants using BrightSource power towers with up to 3.
Majority ownership is by Huanghe. The project will apply to NDRC for feed-in tariff. It is part of an international collaboration. It and Noor 2 of MWe commissioned in use parabolic trough collectors heating diphenyl oxide or oil which produces steam in a secondary circuit, and molten salt storage enables generation beyond sunset.
Noor 3 of MWe commissioned in uses a m high central tower with MWt receiver and molten salt for heat transfer and storage. It has heliostats and is based on the 20 MWe Gemasolar plant in Spain. The whole complex is reported to use 2.
The areas occupied are , , and ha respectively so the full plant covers 21 km 2. A small portable CSP unit — the Wilson Solar Grill — uses a Fresnel lens to heat lithium nitrate to °C so that it can cook food after dark.
Another CSP set-up is the Solar Dish Stirling System which uses parabolic reflectors to concentrate heat to drive a Stirling cycle engine generating electricity. A Tessera Solar plant uses 25 kWe solar dishes which track the Sun and focus the energy on the power conversion unit's receiver tubes containing hydrogen gas which powers a Stirling engine.
Solar heat pressurizes the hydrogen to power the four-cylinder reciprocating Solar Stirling Engine and drive a generator. The hydrogen working fluid is cooled in a closed cycle. Waste heat from the engine is transferred to the ambient air via a water-filled radiator system. The stirling cycle system is as yet unproven in these large applications, however.
A Tessera Solar plant of MWe was planned at Imperial Valley in California and approved in , but a year later AES Solar decided to build the plant as solar PV, and the first phase of MWe was commissioned in as Mount Signal Solar. Power costs are two to three times that of conventional sources, which puts it within reach of being economically viable where carbon emissions from fossil fuels are priced.
Large CSP schemes in North Africa, supplemented by heat storage, are proposed for supplying Europe via high voltage DC links. One proposal is the TuNur project based in Tunisia and supplying up to MWe via HVDC cable to Italy.
The Desertec Foundation was set up in as an NGO to promote the Desertec concept. It comprised 55 companies and institutions and is active in Morocco, Algeria and Tunisia.
The first Dii-fostered project was to be the Noor-Ouarzazate MWe CSP plant in Morocco see above. Morocco is the only African country to have a transmission link to Europe.
In mid the Desertec Foundation left the Dii consortium. Bosch and Siemens had left it in The Desertec Industrial Initiative then announced that it would focus on consulting after most of its former backers pulled out in The remaining members of the Munich-based consortium are Saudi company ACWA Power, German utility RWE and Chinese grid operator SGCC.
The Mediterranean Solar Plan MSP targeted the development of 20 GWe of renewables by , of which 5 GWe could be exported to Europe. The OECD IEA's World Energy Outlook says: The quality of its solar resource and its large uninhabited areas make the Middle East and North Africa region ideal for large-scale development of concentrating solar power, costing 10 to in In its project preparation initiative was being funded by the EU.
In UK-based Xlinks announced plans to build 7 GW of solar PV capacity and 3. Solar energy producing steam can be used to boost conventional steam-cycle power stations. Australia's Kogan Creek Solar Boost Project was to be the largest solar integration with a coal-fired power station in the world.
A hectare field of Areva Solar's compact linear Fresnel reflectors at the existing Kogan Creek power station would produce steam fed to the modern supercritical MWe coal-fired unit, helping to drive the intermediate pressure turbine, displacing heat from coal.
The solar boost at 44 MW peak sunshine would add 44 million kWh annually, about 0. After difficulties and delays, the project was aborted in The MWe Liddell coal-fired power station has a 2 MWe equivalent solar boost 9 MW thermal addition. In the USA the federal government has a SunShot initiative to integrate CSP with fossil fuel power plants as hybrid systems.
The US Department of Energy says that 11 to 21 GWe of CSP could effectively be integrated into existing fossil fuel plants, utilizing the turbines and transmission infrastructure. While CSP is well behind solar PV as its prices continue to fall and utilities become more familiar with PV.
However, CSP can provide thermal storage and thus be dispatchable and it can provide low-cost steam for existing power plants hybrid set up. Also, CSP has the potential to provide heating and cooling for industrial processes and desalination.
Another kind of solar thermal plant is the solar updraft tower, using a huge chimney surrounded at its base by a solar collector zone like an open greenhouse.
The air under this skirt is heated and rises up the chimney, turning turbines as it does so. The 50 MWe Buronga plant planned in Australia was to be a prototype, but Enviromission's initial plans are now for two MWe versions each using 32 turbines of 6.
Thermal mass — possibly brine ponds — under the collector zone means that some operation will continue into the night. A 50 kWe prototype plant of this design operated in Spain In China the A significant role of solar energy is that of direct heating. Much of our energy need is for heat below 60 o C, eg.
in hot water systems. A lot more, particularly in industry, is for heat in the range o C. Together these may account for a significant proportion of primary energy use in industrialised nations. The first need can readily be supplied by solar power much of the time in some places, and the second application commercially is probably not far off.
Such uses will diminish to some extent both the demand for electricity and the consumption of fossil fuels, particularly if coupled with energy conservation measures such as insulation. With adequate insulation, heat pumps utilising the conventional refrigeration cycle can be used to warm and cool buildings, with very little energy input other than from the sun.
Eventually, up to ten percent of total primary energy in industrialised countries may be supplied by direct solar thermal techniques, and to some extent this will substitute for base-load electrical energy.
The core of the Earth is very hot, and temperature in its crust generally rises 2. See also information paper on The Cosmic Origins of Uranium. Where hot underground steam can be tapped and brought to the surface it may be used to generate electricity. Such geothermal sources have potential in certain parts of the world such as New Zealand, USA, Mexico, Indonesia, the Philippines and Italy.
Geothermal energy is attractive because it is low-cost to run and is dispatchable, unlike wind and solar. Global installed capacity was about 14 GWe in , up from 13 GWe in when it produced 88 TWh IRENA data — i. Capacity includes 2.
Iceland gets one-quarter of its electricity from around MWe of geothermal plant. Europe has more than geothermal power plants with about 1. The largest geothermal plant is The Geysers in California, which currently operates at an average capacity of MWe, but this is diminishing.
See also Geothermal Energy Association website. The Iceland Deep Drilling Project IDDP launched in aims to investigate the economic feasibility of extracting energy and chemicals from fluids under supercritical conditions, with much higher energy content.
Drilling reached a depth of 4, metres and encountered fluids at supercritical conditions. The measured temperature was °C and the pressure 34 MPa. Potential utilization is being assessed. There are also prospects in certain other areas for hot fractured rock geothermal, or hot dry rock geothermal — pumping water underground to regions of the Earth's crust which are very hot or using hot brine from these regions.
The heat — up to about °C — is due to high levels of radioactivity in the granites and because they are insulated at km depth. South Australia has some very prospective areas. The main problem with this technology is producing and maintaining the artificially-fractured rock as the heat exchanger.
Only one such project is operational, the Geox 3 MWe plant at Landau, Germany, using hot water ºC pumped up from 3. A 50 MWe Australian plant was envisaged as having 9 deep wells — 4 down and 5 up but the Habanero project closed down in after pilot operation at 1 MWe over days showed it was not viable.
Ground source heat pump systems or engineered geothermal systems also come into this category, though the temperatures are much lower and utilization is for space heating rather than electricity.
Generally the cost of construction and installation is prohibitive for the amount of energy extracted. The UK has a city-centre geothermal heat network in Southampton where water at 75°C is abstracted from a deep saline aquifer at a depth of 1.
Customers for the heat include the local hospital, university and commercial premises. The Geoscience Australia building in Canberra is heated and cooled thus, using a system of pumps throughout the building which carry water through loops of pipe buried in boreholes each metres deep in the ground.
Here the temperature is a steady 17°C, so that it is used as a heat sink or heat source at different times of the year. See year report pdf. This falls into three categories — tidal, wave and temperature gradient, described separately below. The European Commission's Strategic Energy Technology SET plan acknowledges the potential role of ocean energy in Europe's future energy mix and suggests enhancing regional cooperation in the Atlantic region.
The EU Ocean Energy Forum was to develop a roadmap by Harnessing the tides with a barrage in a bay or estuary has been achieved in France MWe in the Rance Estuary, since , Canada 20 MWe at Annapolis in the Bay of Fundy, since , South Korea Sihwa , MWe, since , and Russia White Sea, 0.
The trapped water can be used to turn turbines as it is released through the tidal barrage in either direction.
Worldwide this technology appears to have little potential, largely due to environmental constraints. It was expected to start construction in but is now unlikely to proceed. Natural Energy Wyre in the UK has set up a consortium to develop the Eco-THEP, a 90 MW tidal barrage plant with six turbines on the River Wyre near Fleetwood in northwest England by The planned Cardiff Tidal Lagoon involves a 20 km breakwater with turbines in at least two powerhouse units, total MWe, producing GWh per year at low cost.
About million m 3 of water would pass through the turbines on each tidal cycle. An application to build the project was expected in Placing free-standing turbines in major coastal tidal streams appears to have greater potential than barriers, and this is being developed.
Tidal barrier capacity installed in Europe since reached 27 MWe in , with 12 MWe of that still operational. The remainder had been decommissioned following the end of testing programmes.
Production from tidal streams in was 34 GWh. Another 8 MWe of capacity is planned for Currents are predictable and those with velocities of 2 to 3 metres per second are ideal and the kinetic energy involved is equivalent to a very high wind speed.
This means that a 1 MWe tidal turbine rotor is less than 20 m diameter, compared with 60 m for a 1 MWe wind turbine. Units can be packed more densely than wind turbines in a wind farm, and positioned far enough below the surface to avoid storm damage. For the past years or so, humans have relied heavily on coal, oil, and other fossil fuels to power everything from light bulbs to cars to factories.
Fossil fuels are embedded in nearly everything we do, and as a result, the greenhouse gases released from the burning of those fuels have reached historically high levels.
As greenhouse gases trap heat in the atmosphere that would otherwise escape into space, average temperatures on the surface are rising. Climate change encompasses not only rising average temperatures but also extreme weather events, shifting wildlife populations and habitats, rising seas , and a range of other impacts.
Of course, renewables—like any source of energy—have their own trade-offs and associated debates. One of them centers on the definition of renewable energy. Strictly speaking, renewable energy is just what you might think: perpetually available, or as the U.
Energy Information Administration puts it, " virtually inexhaustible. It also doesn't encompass other low- or zero-emissions resources that have their own advocates, including energy efficiency and nuclear power.
Hydropower: For centuries, people have harnessed the energy of river currents, using dams to control water flow. Hydropower is the world's biggest source of renewable energy by far, with China, Brazil, Canada, the U.
While hydropower is theoretically a clean energy source replenished by rain and snow, it also has several drawbacks. Large dams can disrupt river ecosystems and surrounding communities , harming wildlife and displacing residents. Hydropower generation is vulnerable to silt buildup, which can compromise capacity and harm equipment.
Drought can also cause problems. In the western U. Even hydropower at full capacity bears its own emissions problems, as decaying organic material in reservoirs releases methane.
Dams aren't the only way to use water for power: Tidal and wave energy projects around the world aim to capture the ocean's natural rhythms. Marine energy projects currently generate an estimated megawatts of power —less than one percent of all renewables—but the potential is far greater.
Wind: Harnessing the wind as a source of energy started more than 7, years ago. Now, electricity-generating wind turbines are proliferating around the globe, and China, the U. From to , cumulative wind capacity around the world increased to more than , megawatts from 23, mw—more than 22 fold.
Some people may object to how wind turbines look on the horizon and to how they sound, but wind energy, whose prices are declining , is proving too valuable a resource to deny. While most wind power comes from onshore turbines, offshore projects are appearing too, with the most in the U.
and Germany. The first U. offshore wind farm opened in in Rhode Island, and other offshore projects are gaining momentum. Solar: From home rooftops to utility-scale farms, solar power is reshaping energy markets around the world.
In the decade from and the world's total installed energy capacity from photovoltaic panels increased a whopping 4, percent.
In addition to solar panels, which convert the sun's light to electricity, concentrating solar power CSP plants use mirrors to concentrate the sun's heat, deriving thermal energy instead. China, Japan, and the U.
are leading the solar transformation, but solar still has a long way to go, accounting for around two percent of the total electricity generated in the U.
in Solar thermal energy is also being used worldwide for hot water, heating, and cooling. Biomass: Biomass energy includes biofuels such as ethanol and biodiesel , wood and wood waste, biogas from landfills, and municipal solid waste.
Like solar power, biomass is a flexible energy source, able to fuel vehicles, heat buildings, and produce electricity. But biomass can raise thorny issues. Critics of corn-based ethanol , for example, say it competes with the food market for corn and supports the same harmful agricultural practices that have led to toxic algae blooms and other environmental hazards.
Similarly, debates have erupted over whether it's a good idea to ship wood pellets from U. forests over to Europe so that it can be burned for electricity. Meanwhile, scientists and companies are working on ways to more efficiently convert corn stover , wastewater sludge , and other biomass sources into energy, aiming to extract value from material that would otherwise go to waste.
On a large scale, underground reservoirs of steam and hot water can be tapped through wells that can go a mile deep or more to generate electricity. On a smaller scale, some buildings have geothermal heat pumps that use temperature differences several feet below ground for heating and cooling.
Unlike solar and wind energy, geothermal energy is always available, but it has side effects that need to be managed, such as the rotten egg smell that can accompany released hydrogen sulfide. Cities, states, and federal governments around the world are instituting policies aimed at increasing renewable energy.
At least 29 U. states have set renewable portfolio standards —policies that mandate a certain percentage of energy from renewable sources, More than cities worldwide now boast at least 70 percent renewable energy, and still others are making commitments to reach percent.
Other policies that could encourage renewable energy growth include carbon pricing, fuel economy standards, and building efficiency standards.
Corporations are making a difference too, purchasing record amounts of renewable power in Wonder whether your state could ever be powered by percent renewables? No matter where you live, scientist Mark Jacobson believes it's possible.
The words "sustainable" enerby "renewable" are Green energy practices used to Satiety for weight management Green energy practices sources pfactices primary energyeenrgy interchangeably. However, these words have very different meanings. Not everything renewable is sustainable, and in turn not practcies Green energy practices is sustainable is necessarily renewable. This is closely related to the idea of reserve vs occurrence. Literally 'to make new again', a renewable resource is one that is naturally replenished with time, like the growth of new organisms or natural recycling of materials. Renewable energy is any energy production which uses one of these resources. Renewable resources do not have a fixed quantity - more can always be generated. Green energy practices GGI Insights February 15, Energy conservation practuces a crucial role in our quest for Heart-healthy diet greener and more ;ractices future. Pracfices making conscious Green energy practices and adopting sustainable prafticeswe can reduce our impact on the environment and preserve precious resources for future generations. Conserving energy is essential not only for protecting our environment but also for promoting economic stability. By reducing our energy consumption, we can minimize the demand for fossil fuels and significantly decrease greenhouse gas emissions. This, in turn, helps mitigate climate change, air pollution, and other environmental issues.
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