Shrinking the size and pace requirements for industrial thermal solar installations while assuring an adequate supply of industrial process heat are the goals of a new approach combining solar collectors and heat pumps.

According to researchers from the University of Guanajuato (Mexico) and Texas A&M University, a solar heat pump can be coupled with a low temperature solar collector field to produce medium to high temperature heat. This configuration can reduce costs in addition to the required volume capacity for the storage tank.

The proposed system consists of a solar collector network, a storage system and two heat pumps assisted by the solar collectors themselves. The process was simulated for a sugar mill that also produces bioethanol and electricity from sugarcane bagasse. For power production, a system was modeled that uses thermal energy and a heat pump evaporator to heat water. Using R600a as the heat pump working fluid, the heat is utilized for an organic Rankine cycle to create electricity. Thermal energy harnessed by the heat pump evaporator is used in the production process of second-generation bioethanol.

Analysis revealed that the heat pumps helped reduce the area needed for solar thermal installations by 85%, and the simulated system was demonstrated to produce power at a levelized cost of energy of $0.3435/kWh compared with that of fossil fuels estimated at $0.761/kWh. As for heat, the system described in the journal Energy was able to achieve a cost of $0.1257/kWh compared to $0.124/kWh for fossil fuels.