Energy Sources: Off-shore Wind

Transcription

1 Energy Sources: Off-shore Wind At sea, winds are stronger and steadier than on land, so offshore wind farms deliver a higher power per unit area than onshore wind farms. The Kentish Flats wind farm in the Thames Estuary, about 8.5 km offshore from Whitstable and Herne Bay, which started operation at the end of 2005, was predicted to have an average power per unit area of 3.2W/m2. In 2006, its average power per unit area was 2.6W/m2.

2 The Physics of Wind The answer does not depend on d, but does depend on v 3.

3 The Physics of Wind

4 Variation of Wind Speed with Height

5 Standard Windmill Properties

6 Standard Windmill Properties

7 The Numbers for Britain Land Based

8 The Numbers for Britain Shallow Offshore Within British territorial waters, the shallow area is about km2, most of it off the coast of England and Wales. This area is about two Wales. The average power available from shallow offshore wind farms occupying the whole of this area would be 120GW, or 48 kwh/d per person. But it s hard to imagine this arrangement being satisfactory for shipping. The requirement for shipping corridors and fishing areas must reduce the plausiblyavailable area; I propose that we assume the available fraction is one third. We estimate the maximum plausible power from shallow offshore wind is 16 kwh/d per person.

9 The Numbers for Britain Deep Offshore The area with depths between 25m and 50m is about km2 the size of Scotland. Assuming again a power per unit area of 3W/m2, deep offshore wind farms could deliver another 240GW, or 96 kwh/d per person, if turbines completely filled this area. Again, we must make corridors for shipping (i.e. 1/3rd). The outcome: if an area equal to a 9 km-wide strip all round the coast were filled with turbines, deep offshore wind could deliver a power of 32 kwh/d per person. One issue may be costs of operation. Some off shore windmills are failing in 18 months due to challenging salt water conditions.

10 And for the Birds Do windmills kill huge numbers of birds? Wind farms recently got adverse publicity from Norway, where the wind turbines on Smola, a set of islands off the north-west coast, killed 9 white-tailed eagles in 10 months. I share the concern of BirdLife International for the welfare of rare birds. But I think, as always, it s important to do the numbers. It s been estimated that birds per year are killed by wind turbines in Denmark, where windmills generate 9% of the electricity. Horror! Ban windmills! We also learn, moreover, that traffic kills one million birds per year in Denmark. Thirty-times-greater horror! Thirty-times-greater incentive to ban cars! And in Britain, 55million birds per year are killed by cats (figure 10.6).

11 And for the Birds

12 Geothermal Power Geothermal Energy is energy stored as heat beneath the surface of the solid earth

13 Geothermal Power Locations GWh/a IT SE FR DE (BMU) AT DE GR PT SF BE NL DK UK IR LU SP

14 Geothermal U.S. Locations CALIFORNIA NEVADA IDAHO OREGON UTAH WASHINGTON HAWAII NEW MEXICO ALASKA COLORADO ARIZONA Current Projected 2015 Estimate 2025 Estimate Geothermal is currently about 1% of US power. Geothermal resource assessment shows that nine western states together have the potential to provide 20 percent of national electricity needs 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

15 Geothermal Power Locations Iceland is one of the more countries successful in using geothermal energy: -86% of their space heating uses geothermal energy. -16% of their electricity generation uses geothermal energy. The largest group of geothermal power plants in the world is located at The Geysers, in California.

16 Geothermal Power: The Geysers The Geysers is a complex of 22 geothermal power plants, drawing stream from more than 350 wells, located in the Mayacamas Mountains 72 miles (116 km) north of SF. The largest in the world, the Geysers has 1517 MW of active installed capacity with an average production factor of 63% (955 MW). The Geysers electrical plant reached peak production in 1987, at that time serving 1.8 million people. Since then, the steam field has been in gradual decline as its underground water source decreases. Currently, the Geysers produce enough electricity for 1.1 million people. Techniques developed from Enhanced Geothermal Systems research will increase the production of the region in the future. By reinjecting greywater from the nearby city of Santa Rosa, existing wells will be recharged.

17 Geothermal Power: The Geysers

18 Geothermal -- Some Facts In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost competitive with conventional energy sources. Enhanced geothermal systems tend to be on the high side of these ranges, with capital costs above $4 million per MW and levelized costs above $0.054 per kwh in 2007 Geothermal plants can be online 100%-90% of the time. Coal plants can only be online 75% of the time and nuclear plants can only be online 65% of the time. Geothermal plants do not require a lot of land, 400m 2 can produce a gigawatt of energy over 30 years. Extracting large amounts of water can cause land subsidence, and this can lead to an increase in seismic activity. To prevented this the cooled water must be injected back into the reserve in order to keep the water pressure constant underground. The project in Basel, Switzerland was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection

19 Geothermal -- Emissions

20 Solar We can turn this raw power into useful power in five ways: 1. Solar thermal: using the sunshine for direct heating of buildings or water. 2. Solar cooling: provide thermal energy to drive thermally-driven chillers 3. Solar photovoltaic: generating electricity. 4. Solar biomass: using trees, bacteria, algae, corn, soy beans, or oilseed to make energy fuels, chemicals, or building materials. 5. Food: the same as solar biomass, except we shovel the plants into humans or other animals.

21 Solar In a typical UK location the sun shines during just 34% of daylight hours.

22 Solar Thermal Assuming a roof area of 10m 2 of panels per person and 50%-efficient at turning the sunlight s 110W/m 2 into hot water 50% 10m 2 110W/m 2 We find solar heating could deliver 13 kwh per day per person.

23 Solar PV The average power delivered by south-facing 20%-efficient photovoltaic panels in Britain would be 20% 110W/m2 = 22W/m2. If every person has 10m 2 of expensive (20%-efficient) solar panels and cover all south-facing roofs. These will deliver 5 kwh per day per person.

24 Solar Farming If a breakthrough of solar technology occurs and the cost of PV came down enough that we could deploy panels all over the countryside, what is the maximum conceivable production? If we covered 5% of the UK with 10%-efficient panels, we d have 10% 100W/m2 200m2 per person 50 kwh/day/person. assuming only 10%-efficient panels. The power density (the power per unit area) of such a solar farm would be 10% 100W/m 2 = 10W/m 2.

25 Photovoltaics in US How much PV area do we need for US electricity consumption of 3,600 billion kw-hr/year? Assume 10% efficiency for W/m 2 Per m 2 of PV, we get 0.1 * 5 * 300 days/year * 1000 W/m 2 = 150 kw-hr/year so we need 2.4 x m 2 or ~200 km x 120 km of solar panels As a U.S. crop, this would rank near soybeans (10th)

26 The Desertec Plan An organization called DESERTEC is promoting the use of concentrating solar power in Mediterranean countries, and high-voltage direct-current (HVDC) transmission lines to deliver the power to cloudier northern parts. HVDC technology is already used to transmit electricity over 1000-km distances in South Africa, China, America, Canada, Brazil, and Congo. A typical 500 kv line can transmit a power of 2GW. A pair of HVDC lines in Brazil transmits 6.3GW. The power losses on a 3500 km-long HVDC line, including conversion from AC to DC and back, would be about 15%. The power needed to give 125 kwh/day to 1 billion people is TWh/y (5 200GW) TWh/y (650GW) is 16 kwh/day per person for 1 billion.

27 Desert Power

28 The Solar Scale and Building Integration

29 Green Ambitions meet Social Reality

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31 Living off other countries Renewables Most of the resources for living sustainably are related to land area. When looking for help, we want to work with countries with low population density, large land area, and a renewable power supply with high power density.

32 A plan for Britain

33 A plan for Britain

34 Gadget Consumption