Future low carbon energy systems - Copenhagen Cleantech Cluster

Catalogue of energy technologies4The main uses of geothermal energy are:water from springs or reservoirs near the surfacesteam at very high temperature (300 to 700 degreesFahrenheit). Geothermal power plants are generallybuilt where geothermal reservoirs are located within amile or two of the surfacetemperatures near the earth's surface (less than 100metres) for space heatingInstalled geothermal generating capacity in the EU was 893MWe in 2005, mostly in Italy and Iceland. European productionof geothermal energy for heating was 2.3 Mtoe in 2005.Most geothermal heat is produced in Turkey and Iceland.The first plant in Denmark opened in 1984 in Thisted. Thesecond, which opened in 2005 at Margretheholm, supplies1% of the total heat demand in Copenhagen.The resources are huge in many parts of the world, henceonly market conditions sets limits for the application.In its Alternative Policy Scenario, the International EnergyAgency (IEA) assumes an installed capacity of 3,000 MWe inOECD Europe by 2030 [8]. Today the technology to extract heatfrom underground aquifers is well known, but the energy availableat shallow or moderate depths is limited, However, a hugeenergy resource exists at greater depths, including in Denmark.Denmark has huge potential for geothermal energy, and highoil prices have encouraged an increasing number of cities toembark on geothermal projects. It is difficult, however, topredict the share of geothermal energy in the future Danishenergy system. In some countries, including Denmark, geothermalenergy is not available at a high enough temperaturefor electricity production. District heating systems based onheat pumps, however, can make good use of low-temperaturegeothermal energy.4.1.13 Hydro, ocean, wave and tidalThis group of energy supply technologies is based on theuse of potential, kinetic or thermal energy of water as energysource and show different stage of development. Hydropower and pumped hydro storage systems have for manyyears been fully commercially competitive in many parts ofthe world. On the other hand ocean energy, including waveand tidal are at an early stage of development.OECD and non-OECD countries produce roughly equalamounts of hydroelectricity. Little growth is expected inOECD countries, where most hydro potential has alreadybeen realised: on average, capacity has increased by just0.5% annually since 1990. The OECD nations produced1,343 TWh of hydroelectricity in 2003, the largest contributorsbeing Canada (338 TWh), the USA (306 TWh) andLarge hydro remains one of the lowest-cost generating technologies,although environmental constraints, resettlementimpacts and the limited availability of sites have restrictedfurther growth in many countries. Large hydro supplied 16%of global electricity in 2004, down from 19% a decade ago.Large hydro capacity totaled about 720 GW worldwide in2004 and has grown historically at slightly more than 2% annually.China installed nearly 8 GW of large hydro in 2004,taking the country to number one in terms of installed capacity(74 GW). With the completion of the Three Gorges Dam,China will add some 18.2 GW of hydro capacity in 2009.Small hydropower has developed for more than a century,and total installed capacity worldwide is now 61 GW. Morethan half of this is in China, where an ongoing boom insmall hydro construction added nearly 4 GW of capacity in2004. Other countries with active efforts include Australia,Ocean currents, some of which run close to Europeancoasts, carry a lot of kinetic energy. Part of this energy canbe captured by submarine “windmills” and converted intoelectricity. These are more compact than the wind turbinesused on land, simply because water is much denser than air.The available power is about 1.2 kW/m2 for a current speedof 2 m/s, and 4 kW/m2 for a current of 3 m/s. The main Europeancountries with useful current power potential areFrance and the UK.Ocean tides can be exploited for only four or five hours percycle, so power from a single plant is intermittent. A suitablydesigned tidal plant can, however, operate as a pumped storagesystem, using electricity during periods of low demandto store energy that can be recovered later. The only large,modern example of a tidal power plant is the 240 MW LaRance plant, built in France in the 1960s, which represents91% of world tidal power capacity.Wave energy can be seen as stored wind energy, and couldtherefore form an interesting partnership with wind energy.Waves normally persist for six to eight hours after the winddrops, potentially allowing wave power to smooth out someof the variability inherent in wind power.Risø Energy Report 723