Experimental Verification of Thermally Activated Power and Cooling System Using Hybrid Thermoelectric, Organic Rankine Cycle and Vapor Compression Cycle

A waste heat recovery system consisting of a hybrid power and cooling cycle is described in this paper. It couples a thermoelectric generator (TEG) and an organic Rankine cycle (ORC) driving a vapor compression cycle to implement heat activated power and cooling. The system was designed, developed and tested under laboratory conditions using a hot air source simulating a heavy-vehicle exhaust stream. The hybrid or so-called co-functional power and cooling system was designed to approach the size of a fieldable unit for testing with mobile diesel generators or heavy-vehicle exhaust streams, which have strict requirements for size, weight and efficiency. As a result, microchannel heat exchangers were used extensively throughout the system design. High temperature bismuth telluride (Bi2Te3) thermoelectric (TE) modules were used and the TEG section contained 20 modules in two distinct electrical strings sandwiched between microchannel cold-side and hot-side heat exchangers. The co-functional system has shown stable operation during tests conducted at various incoming hot air temperatures up to 388 °C, simulating common heavy-vehicle exhaust stream conditions. Although the TEG power output was significantly lower than the design value because of reduced heat transfer into the TE modules due to contact area mismatch and significant heat loss, many system performance parameters reached or even exceeded the target values at design conditions. Design modifications are being implemented to incorporate custom designed TE modules into the system and to reduce the TE cold side temperature to improve the TEG output.