Some argue that geothermal energy is a dilute, low-grade energy resource.

Some argue that geothermal energy is a dilute, low-grade energy resource. Estimate the minimum mass of hot rock needed to produce 1,000 MWe-yr of electricity assuming that the rock mass is solid granite with a density of 2,500 kg/cubic meter and a heat capacity of 1,000 J/kg K at an initial temperature of 250°C. An ambient temperature of 25°C can be assumed