Design Procedure and Application of Solar-Assisted Series Heat Pump Systems

A general design procedure is presented for solar-assisted series heat pump systems used for space and process water heating. The procedure accounts for the variable efficiency and rate of energy delivery by the heat pump. The fraction of the required energy supplied by solar and the fractions supplied by work and auxiliary are determined. The performance results from this design procedure are compared against detailed computer simulations on a monthly and seasonal basis. For low temperature space heating applications, the maximum difference between the design procedure and computer simulations is three percent on a seasonal basis and 12 percent on a monthly basis. For high temperature process water heating systems, the maximum differences are three to six percent on a seasonal basis and six to 12 percent on a monthly basis, with the accuracy dependent upon the control strategy used. This design procedure is used to investigate high temperature series heat pump systems for providing hot water for industrial processes. Various system parameters are evaluated in terms of the overall effect that each has on system performance and design. Recommendations are given for high temperature series heat pump system design.