Effect of load following strategies, hardware, and thermal load distribution on stand-alone hybrid CCHP systems

Abstract

This study investigates the effects of two types supplementary prime movers (internal combustion engines and micro gas turbines) when integrated with photovoltaic modules into hybrid energy systems (PV/Batt/ICE, PV/Batt/MGT). All systems analysed meet highly dynamic electric, heating, and cooling demands to a specified reliability (Loss of Power Supply Probability). The effects of adding absorption chiller, thereby fundamentally transforming the systems from Combined Heat and Power to Combined Cooling, Heating, and Power (CCHP) is studied. This is done in the context of two different load following strategies (Following Electric to Thermal Load–FEL/FTL vs Following Electric Load–FEL). The Multi-objective Genetic Algorithm (GA) is implemented to optimise these systems based on both Cost of Energy and overall efficiency, the consequential outcomes of the simulations are also reported in terms of several key operational indicators.Results indicate that if operating under an FEL/FTL type PMS, both PV/Batt/ICE and PV/Batt/MGT–based CHP systems have marginal differences in terms of Cost of Energy (0.25 $/kWh, 0.28 $/kWh, respectively) compared to the CCHP systems (0.28 $/kWh, 0.31 $/kWh, respectively). However, the overall efficiency in CCHP systems is higher with FEL/FTL (65% for PV/Batt/ICE, 43% for PV/Batt/MGT) compared to FEL (57% for PV/Batt/ICE, 37% for PV/Batt/MGT). In terms of load following strategies, the FEL leads to higher environmental benefits compared to the FEL/FTL for both PV/Batt/ICE and PV/Batt/MGT–based CCHP systems. The results also indicate that relative magnitude of heating (Pther,h) and cooling (Pther,c) has insignificant effects on the Cost of Energy for the PV/Batt/ICE–based CCHP systems; however, this significantly increases with Pther,h:Pther,c for the PV/Batt/MGT.