Building cooling heating power (BCHP) systems as a kind of distributed energy resource have shown a great potential in improving energy efficiency and meeting multiple energy demands in buildings. In this paper, we present a BCHP system driven by solar energy with flat-plate solar collectors. A modified system efficiency is introduced to evaluate the whole day performance of the system more accurately. Based on the mathematical models and simulation platform established, we have investigated the influences of some key thermodynamic parameters, namely condensation temperature, turbine inlet temperature and turbine inlet pressure on the system performance. In order to find the optimum combination of these parameters that leads to the best performance, we have performed parametric optimization by means of the genetic algorithm. Results indicate that the best performance and the highest efficiency of the system are achieved when the working fluid reaches its saturated state and the corresponding efficiencies of the system operating in the combined heating power mode, the combined cooling power mode and the power production mode turn out to be 19.10%, 27.24% and 10.47%, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

The utilization of renewable energy for desalination can solve the problems of energy crisis and fresh water shortage. In this study, a reverse osmosis (RO) desalination system driven by solar-powered organic Rankine cycle (ORC) and wind energy is proposed, which is different from the current desalination system driven by single energy source. In order to ensure the continuous production, energy storage units are employed. A mathematical model is established to simulate the overall system which mainly consists of a solar collector subsystem, an ORC subsystem, a wind power subsystem and a RO desalination subsystem. The sensitive analysis of some key parameters, namely turbine inlet pressure, condenser temperature of ORC, feed water pressure and the water salinity, is conducted to determine the relationship between parameters and fresh water output. The result shows daily fresh water output increases with the increase in the turbine inlet pressure under the given conditions. The condenser temperature has a significant effect on daily fresh water output. With the increase in feed water pressure, the fresh water output and the required membrane area both decreases. The fresh water output is also sensitive to the water salinity, while the required membrane area is less sensitive to it.

In this paper, a novel combined heat and power (CHP) system is proposed in which the waste heat from a supercritical CO₂ recompression Brayton cycle (sCO₂) is recovered by a LiBr-H₂O absorption heat pump (AHP). Thermodynamic and exergoeconomic models are established on the basis of the mass, energy, and cost balance equations. The proposed sCO₂/LiBr-H₂O AHP system is examined and compared with a stand-alone sCO₂ system, a sCO₂/DH system (sCO₂/direct heating system), and a sCO₂/ammonia-water AHP system from the viewpoints of energy, exergy, and exergoeconomics. Parametric studies are performed to reveal the influences of decision variables on the performances of these systems, and the particle swarm optimization (PSO) algorithm is utilized to optimize the system performances. Results show that the sCO₂/LiBr-H₂O AHP system can obtain an improvement of 13.39% in exergy efficiency and a reduction of 8.66% in total product unit cost compared with the stand-alone sCO₂ system. In addition, the sCO₂/LiBr-H₂O AHP system performs better than sCO₂/DH system and sCO₂/ammonia-water AHP system do, indicating that the LiBr-H₂O AHP is a preferable bottoming cycle for heat production. The detailed parametric analysis, optimization, and comparison results may provide some references in the design and operation of sCO₂/AHP system to save energy consumption and provide considerable economic benefits.