|
|
re: nuclear / heat pump efficiency
16 mar 2000
dirk mittler wrote:
>...if a nuclear power station is its 38% efficient at generating electrical
>output, and a heat pump has a heat factor of 2.5, is it still more efficient
>to burn greenhouse-gas producing fossil fuels, that waste heat through
>exhaust gas, to heat directly at 70% efficiency?
suppose we ignore nukes, since they represent such a concentration of money
and power, and their pollution is spread over hundreds of thousands of years,
and the difference between the energy used to gather and refine their fuels
and their energy output is small.
one might ask, "is it more efficient to a) heat a house with electricity
from a 38%-efficient natural gas utility, using a heat pump with a cop of
2.5, and also buy electricity from the utility, or b) use the gas to heat
the house with a small cogen system (like intelligen's diesel) that's 97%
efficient (dividing the electrical plus heat energy produced by the heating
value of the gas used to produce that combined energy.)
in case a), we might burn 1 kwh of gas at the utility to deliver (?)
each 0.38 kwh of electrical energy, wasting 62% of the gas heat up a
cooling tower, and then turn the 0.38 kwh back into 0.38x2.5= 0.95 kwh
of heat, and also purchase 0.37 kwh of electricity, which requires the
utility to burn an additional 0.37/0.38 = 0.96 kwh of gas, using a
total of 1.96 kwh of gas heat.
in case b) we might burn 0.95/0.7 = 1.36 kwh of gas to produce the same
0.95 kwh of useful heat and 1.36x0.27 = 0.37 kwh of electricity, so
b) is more efficient.
nick
|
|
