97 The heat flow at the surface is 50mW/m2. Massachusetts Institute of Technology (2006) says 59 mW/ m2 average, with a range, in the USA, from 25 mW to 150 mW. Shepherd (2003) gives 63mW/m2.
98 "Generation of electrical power from hot dry rock was unlikely to be technically or commercially viable in the UK". Source: MacDonald et al. (1992). See also Richards et al. (1994).
- The biggest estimate of the hot dry rock resource in the UK... could conceivably contribute 1.1 kWh per day per person of electricity for about 800 years. Source: MacDonald et al. (1992).
- Other places in the world have more promisinghot dry rocks. There's a good study (Massachusetts Institute of Technology, 2006) describing the USA's hot dry rock resource. Another more speculative approach, researched by Sandia National Laboratories in the 1970s, is to drill all the way down to magma at temperatures of 600-1300 °C, perhaps 15 km deep, and get power there. The website www.magma-power.com reckons that the heat in pools of magma under the US would cover US energy consumption for 500 or 5000 years, and that it could be extracted economically.
- Southampton Geothermal District Heating Scheme. www. southampton. gov. uk.
Transporting stuff: 12 kWh/d
Food, farming, fertilizer: 15 kWh/d
Light: 4 kWh/d
Heating, cooling: 37 kWh/d
Jet flights: 30 kWh/d
Geothermal: 1 kWh/d
Tide: 11 kWh/d
Deep offshore wind: 32 kWh/d
Shallow offshore wind: 16 kWh/d
Biomass: food, biofuel, wood, waste incin'n, landfill gas: 24 kWh/d
Solar heating: 13 kWh/d
Wind: 20 kWh/d
Figure 16.6. Geothermal.
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