Combined desalination and power generation using solar energy

Integrated desalination and power generation using solar energy is a prospective way to help solve the twin challenges of energy and fresh water shortage, while helping save farm land degradation in salt-affected areas. As part of the design of a combined desalination and power supply system, this paper presents the performance analysis of a two-phase nozzle using a homogenous equilibrium model. It also presents the designing and testing of a prototype system using three different types of nozzle under static and rotary conditions. Initially the performance analysis of a spray nozzle is presented along estimation of both the fresh water production and power generation. The performance analysis of a convergent-divergent (C-D) nozzle is then presented. The experimental results for freshwater production are consistent with the theoretical calculation using the Homogenous Equilibrium Expansion Model (HEM). However, there is a large difference between experimental and theoretical values for power generation. Based on the experimental analysis, reasons for the low power generation are found and a new design for the reaction turbine is proposed using a curve length C-D nozzle to overcome the problems encountered with the previous prototype. The preliminary results show a 30% improvement in the experimentally observed reaction force caused by the flow of water in the static test of the new nozzle design; while the rotary CDP system using new disc nozzle has not been tested thoroughly according to different parameters, the rotation without load and the maximum power output can reach 6000rpm, 1000Watts respectively. In addition, the author has done some work on using ejector to create vacuum to save the energy consumed by vacuum pump. After analyzing the efficiency of the cycle by T-S diagram and comparing with the experimental results obtained with reference to different pressures and temperatures, it is suggested that an evacuated tube solar collector connected in series with salinity gradient solar ponds can be used to boost the temperature of the salt water and to improve the efficiency of the system.