Rebound effect Suppose you get two 4 W LED lamps as a
birthday present with which you replace two 40 W incandescent lamps each
burning 1,000 hours per year. The money you save will be spent on candy bars
that you otherwise would not buy. Each bar weighs 50 grams and costs €0.70.
The production of 1 kg of candy bars requires 14.5 kWh of
electricity and 18.5 MJ of fuel oil. Electricity production: 40 per cent in
natural-gas-fired power plants (efficiency: 55 per cent), 60 per cent in
coal-fired power plants (efficiency: 42 per cent). Efficiency of electricity
transport and distribution: 95 per cent. Electricity price: €0.21 / kWh
a. Calculate the annual electricity savings (in
kWh/year), electricity cost savings (in €/year) and the number of candy bars
per year that can be bought with the electricity cost savings (do not round to
a whole number of bars).
b. Calculate the primary energy savings by using the LED
lamps in MJ/ year. Use a second order approach.
c. Calculate the primary energy use of producing a candy
bar. Use a second order approach.
d. Calculate the rebound effect: how much of the primary
energy savings by using LED lamps disappears by spending the energy cost
savings on candy bars?