What renewables are• These are resources found in nature that are self-regenerating:• These sources are normally used to produce clean (or green)energy. This production does not lead to climate change and doesnot involve emission of pollutants.• A related term is sustainable energy: this concept refers togenerating energy with an awareness of the future, i.e. in a way thatwould enable future generations to meet their energy needs too. Theconcept is related not only to renewables, but also to energyefficiency.
Renewable energy is growing in importance and popularity:• because of the desire and necessity to avert irreversibleclimate damage;• because of increasing oil prices;• because of the unreliability of non-renewable resources(e.g. the depletion of oil wells).• In view of all these and other factors, governmentsworldwide support renewables with various incentives.• This, in turn, encourages entrepreneurs to make large-scaleinvestments in renewable energy.
Main types of renewable energy • Solar energy • Wind energy • Hydropower (water power) • Biofuels • Geothermal energyThere are many sources of renewable energy, but all of them,except geothermal energy, are more or less directly related tothe sun: the main source of clean and sustainable energy forthe earth.
Solar energyApart from the everyday applications of solar energy, such as room lighting, it isharnessed by two quite different methods: photovoltaics and solar thermal. Photovoltaics (PV): the Solar thermal energy (STE): a application of solar cells technology that uses solar to convert sunlight directly energy to produce thermal into electricity. When PV energy, i.e. heat. There are low-, cells are assembled, they medium-, and high-temperature form a PV module (or solar thermal collectors. The first panel). An installation of two types are flat plates panels is called a PV generally used to heat water. array. High-temperature collectors Solar cells are often made concentrate sunlight with mirrors from wafers: slices of or lenses and are mostly used to semiconductor material, produce electricity. This such as silicon crystal. technique is known as World leaders in PV use: concentrated solar power Germany, USA, Spain (CSP).
Solar energy (2)CSP systems are also ableto track the movement ofthe sun. The radiation There are various concentratingthey concentrate is used technologies, the most prominentas a heat source for a being the solar trough, theconventional plant to parabolic dish and the solar powerproduce heat or electricity tower.[concentrating solarthermal (CST) systems] oris directed to PV surfaces A notable and ambitious project isto generate electrical the solar power satellite: a systempower [concentrating PV of solar collectors in space that(CPV) technology]. would be directly exposed to the sun’s radiation and would transmitCSP allows solar the generated power to a largeinstallations to increase antenna on the earth. The costs fortheir productivity. CSP the satellite’s construction,plants take up smaller however, would be very high.areas, which helps toreduce costs.
Wind energyThe energy of wind is Wind energy currentlyharnessed with wind turbines. generates only 1% of allThey are usually grouped in electricity on a global scale,wind farms (sometimes called but its share is growingwind parks). There are onshore rapidly. In Denmark, for farms (which, example, wind already however, are often accounts for 19% of the total near water); electricity production. nearshore farms (on land or on sea within several km Since wind is intermittent, turbines can’t constantly of a coast); and work at their full offshore parks capacities. The ratio of (ten km or more actual annual productivity from land). to the theoretical maximum capacity isWorld leaders in wind energy use: called capacity factor. ItGermany, USA, Spain, India typically reaches 20% to 40%.
Another technology that Hydropower utilizes a dam but no reservoir is the run-of-Hydropower (also Hydropower was harnessed with the-rivercalled hydraulic or waterwheels to operate hydroelectricwater power) is generation. Here, watermills, sawmills, textilederived from the the dam cuts machines and others long beforeforce of moving electric power came into use. across the river,water. Since water ensuring wateris much denser will fall from itsthan air, its Hydropower supplies some 19% of upper edge, passmovement all electricity in the world. It is through turbines generally far cheaper than fossilgenerates more and flow back fuels or nuclear energy.energy than wind into the lowerdoes. level of the river. Hydroelectricity is mostly In some run-of-Electricity generated in dams. Water is the-rivergenerated with first collected in dams, then let installations,hydropower is flow through turbines. A great water is directedcalled advantage of this technology is into a pipe, fromhydroelectricity. that the amount of energy where it passes produced can be easily adjusted through turbines to the level of demand by and returns into controlling the outflow of water. the river.
Hydropower (2) The lack of a reservoir reduces the negative environmental impact of the power installations. However, there are certain problems related to dams, such as highconstruction and maintenance costs, the risk of dam breakage, and perils for waterfauna. To avoid these complications, damless hydroelectricity has been created. Another up-and-coming electric source is Tidal power technologies convert wave power. One wave power technology the energy of tides into electricity. employs buoyant objects that the waves Their biggest advantage is the fact move, creating electricity. With wind that tides are much more turbines, the air fluctuations caused by the predictable than wind or solar moving water can also be used to produce energy. However, tidal power is power. A project that uses the movement not very common yet. of the water below its surface has also been Tidal energy is captured with tidal developed. stream systems which use the kinetic energy of moving water to The first wave farm (a World drive turbines. A less popular collection of wave power leaders in technology to capture tidal energy generators) in the world was opened in 2008 in hydropower are barrages (similar to dams), which use the water’s potential Portugal. Its capacity is use: China, energy. Barrages are not preferred 2.25 MW. Scotland plans to Brazil, because of higher costs and bad build an even larger facility Canada, environmental effects. with a 3 MW capacity. USA, India
Biomass and biofuel Biomass consists of living or recently dead organisms or other biological material, i.e. carbon. Biomass is used to produce biofuel. The most common material for biofuels are photosynthetic plants. A plant especially grown to be used for biofuel manufacturing is known as an energy crop.Biodiesel is a very Biogas is produced by the Bioalcohol (orcommon biofuel. It is biological breakdown of organic alcohol fuel) ismade from oils matter in the absence of produced with the(extracted from oxygen. The biodegradable help of fermentation-maize, soy, rapeseed, materials in question can be inducingsunflower, palm fruit manure, sewage, green waste microorganisms. Theand sometimes from (plant parts), household and most common isanimal products) that industrial waste. Biogases are ethanol fuel (orundergo chemical rich in methane. They can be bioethanol) that isprocessing. Used used to generate heat, electric widely used instead ofedible vegetable oil is or mechanical energy, or as fuel petrol to power cars insometimes for vehicles. some countries,transformed into predominantly Brazil. Biogas is produced in facilitiesbiodiesel too. for biological treatment ofBiodiesel is mixed with waste. It is also formed World leaders inmineral diesel to be naturally in landfills where it biomass use: USA,used in diesel engines. contributes to the greenhouse Germany, Brazil, effect. UK
Geothermal energy This type of energy is obtained by tapping the heat of the earth, which is mostly in the form of hot water and steam. Various technologies are used to get to the heat under the earth’s surface at different depths. In some areas of the planetSeveral metres under geothermal energy is closer to thethe earth’s surface the surface and therefore easier totemperature is between Geothermal power harness. One of the most favourable10° and 16°C. In winter stations are areas is Iceland with its highthis heat can be expensive to build concentration of volcanoes.brought to buildings but their operating Geothermal sources account for 19%with pipes. costs are low. A of Iceland’s electricity production, significant and geothermal heating is used inAnother technology advantage is thatuses deep wells in hot 87% of homes in the country. geothermal energy Iceland also plans to go fully fossil-rock in which fluid is is not dependent onheated to produce fuel free in the near future. weather conditions.steam, which then A major The country with the greatestdrives turbines to disadvantage is the geothermal energy production,generate electricity. risk for land however, is the USA. There is theThe facilities that stability in the biggest dry steam field, The Geysers,enable this process are region where such with an annual capacity of 750 MW.called dry steam, flash a plant issteam and binary-cycle Another country with significant constructed.plants. geothermal energy resources and production is the Philippines.
Pros and cons We can’t run out of renewables Biomass and geothermalbecause nature replenishes them energy need wise faster than we consume them. management to avoid their depletion. The use of domestic power If clean energy becomes generators (e.g. solar prevalent, the electricity panels on the roof) reduces transmission and distribution the strain on power systems must be distribution systems. transformed and managed more actively (why: see next slide). Green electricity is becoming increasingly accessible to the average consumer. Renewable heat is still expensive and hard to access. Renewables are generally not hazardous Some green energy installations to the environment. take up large pieces of land that can be used to grow crops.
Distributed generation Traditional energy generation is mostly done in centralized facilities from where energy must travel a lot to reach the end consumer:large plant power power substation consumer transmission distribution This is done to achieve economies of scale, or to bring energy generation closer to the resource (e.g. mines) and away from populated areas (for health reasons). However, some of the energy, especially heat, is lost during the transportation. By contrast, renewables are often associated with distributed generation (also called dispersed generation or decentralized energy). This is producing energy in many small facilities and transporting it over short distances. Roof solar panels and wind turbines are examples of distributed energy resources (DERs).In order for renewable energy to become massively used, energysystems must be adjusted to reflect the shift from centralized todispersed generation.
What energy qualifies as renewable Some scientists and politicians argue that nuclear energy is renewable since the resources from which it is derived (such as uranium) would not be exhausted in millions of years.These claims, however, havenot been proven;furthermore, nuclear energyhas an extremely dangerousbyproduct: nuclear waste.For this reason, governments Fossil fuels could be regarded as biomassdon’t recognize nuclear since their have biological origin; howeverenergy as renewable and it is they are neither sustainable nor greennot eligible for state because:subsidies. •this is organic material that has undergone millennium-long geological transformation; •thus, the regeneration rates of fossil fuels are extremely slower than the rate at which they are consumed; •fossil fuels emit CO2 when burnt.
Feed-in tariffs Feed-in tariffs were introduced as early as 1978 in the USA. Now, they are implemented in Since renewables are still around 50 countriesinnovative and in active development, around the world.they are often not competitive withtraditional energy sources. Therefore, In Germany, for example,green-minded governments provide feed-in tariffs arevarious incentives that encourage regulated by theinvestments in the sector and promote renewables lawits faster development. Among the most (Erneubare-Energien-common is the feed-in tariff. This is an Gesetz). The programme adds around EUR 1 toobligation imposed on utilities by the each monthly residentialgovernment to buy a certain amount of electricity bill, whichrenewable electricity at prices higher translates into billions ofthan the markets rates. The higher euro of subsidies for theexpenditure for the utility is passed on to clean energy sector eachits customers. The increase of prices that year. The country aims atcustomers have to bear is usually small, generating 12.5% of its electricity frombut these small contributions are a renewable sources bypowerful and effective way to support 2010. The percentagegreen energy. should rise to 20 by 2020.
So, in a word…A plethora of renewable energy is all around us, with even more ways to make use of it.