A SUBOPTIMALLY CONTROLLED SOLAR HEATING SYSTEM UTILIZING A DUAL SOURCE HEAT PUMP

This work describes the mathematical modeling and the optimal control of a residential solar space heating system utilizing a dual source heat pump. The primary source for the heat pump is a solar thermal storage tank, with well water serving as the auxiliary heat input. Three separate modes are included in the heating system and switching among these modes is a function of the relative energy storage levels within the system.; The model incorporates a novel method for the on-line generation of the heat pump coefficient of performance (COP) which avoids resorting to the nonlinear equations of the heat pump components. This is accomplished by a simulation package which contains the equations describing the thermodynamic properties of the heat pump refrigerant. The COP is determined by inputing to the program the on-line measurements of four heat pump state variables (two temperatures and two pressures) and calculating the refrigerant enthalpies at key locations in the vapor compression cycle.; The system is governed utilizing optimal control techniques. The application of these techniques produces a suboptimal controller which is a linear regulator. As such, the system is driven from a given initial state (a set of temperature measurements) to a desired final state (a second set of temperatures) while minimizing a quadratic performance index. The performance index is made to be sensitive to the price of electricity and it directs the controller to minimize the cost of collecting and distributing energy while maintaining a comfortable living area.; Results indicate that the suboptimal controller has successfully achieved the design goals. The temperature of the living space has been shown to remain at a comfortable level (within 2(DEGREES)F of the set value of 70(DEGREES)F) over varying conditions of both insolation and ambient temperature. This has been accomplished by a controller which is responsive to the energy demand on the electrical utility, thereby using less electricity when the cost of producing it is higher. Moreover, the heating system has exhibited stable operating characteristics during conditions of system controller feedback signal loss.