  We analyze a heat engine based on a hot cavity connected via quantum wells to
electronic reservoirs. We discuss the output power as well as the efficiency
both in the linear and nonlinear regime. We find that the device delivers a
large power of about 0.18 W/cm^2 for a temperature difference of 1 K nearly
doubling the power than can be extracted from a similar heat engine based on
quantum dots. At the same time, the heat engine also has a good efficiency
although reduced from the quantum dot case. Due to the large level spacings
that can be achieved in quantum wells, our proposal opens the route towards
room-temperature applications of nanoscale heat engines.
