Modeling and optimizing of a combined CHP system, compression chiller and reverse osmosis plant (CHP + C + W) in two strategies of connections with grid

Abstract

Energy and environment crises have led contemporary modern human to think about designing systems with high efficiency to meet the energy needs. A Combined Cooling, Heating and Power system with precise utilization of energy dissipation and considering the annual loads reduces fuel consumption and environmental pollution. On the other hand, fresh water is another need of contemporary societies which consume significant amounts of energy especially in hot regions. In this paper, the performance of a CHP system coupled to a Compression chiller, and a plant for fresh Water production, Reverse Osmosis desalination, for domestic uses is investigated. The performance of this system (CHP + C + W) is studied by triple-aspect function (energy, economy and environment) and it was conducted under two conditions of selling (sell, extra electricity generated can be sold to the grid,) and not selling (not sell, extra electricity generated cannot be sold to the grid) electricity for selecting one or two prime movers. The results showed that 70 and 45 kW capacities are required while selecting one prime mover and two prime movers in “sell” mode and “not sell” mode, respectively, to maximize objective function, leading to noticeably reduced system costs. Results showed that maximum annual profit happens in 45 kW (in one prime mover selection) capacity and 2 × 40 (in two prime mover selection) in “not sell” mode and 70 kW capacity and 2 × 30 kW in “sell” mode, respectively; when two prime movers are selected, maximum annual profit declines. Generally speaking, one gas engine selection can be considered as the most appropriate economic option for “sell” and “not sell” modes; however, system performance in two prime mover selection is better concerning load curve coverage and utilization.