The outside coils of a certain electric heat pump operate at 10 °C below the ambient temperature, and those on the inside operate at 10 °C above the ambient temperature. Otherwise, there are no losses at all. Suppose that the outside temperature is freezing and the indoor temperature is kept at 17 °C.
(a) How many joules of work are required for your heat pump to deposit one joule of heat energy inside?
(b) Now suppose that the combined power plant and transmission line efficiency is 30%. That is, of the energy of the original primary fuels, 30% reaches your heat pump as electrical energy. How many joules of energy in the primary fuels are required per joule of energy delivered to your house?
(c) Is it a more efficient use of primary fuels to run your electric heat pump or to burn the primary fuels in your space heater?