Three designs for a power plant using the geothermal energy are proposed by a company. Use the Carnot principles to determine which design is possible.

Carnot Principles

Power plant receives heat from a heat source (the hot spring), output net work, and rejects heat to a heat sink (the ambient air). Hence, it is a heat engine. All heat engines in practice are irreversible.

The Carnot principles state that the efficiency of an irreversible heat engine is always less than the efficiency of a reversible one operating between the same two reservoirs. The thermal efficiency of a Carnot heat engine working between 140 ^oC and 30 ^oC is 26.6%.