Is a distributed system based on a micro gas turbine integrated with renewable energy sources suitable for effective desalination? Sensitivity and exergy analysis

To satisfy the increasing demand for energy and potable water while ensuring sustainable development, renewable energy sources have to be integrated in energy systems for central and remote communities. Distributed Micro-Generation (DMG) systems are gaining interest to supply electricity to remote locations and to be integrated in large electricity grids. Several synergies are possible between renewables and DMG systems, however the feasibility of such systems is still uncertain. To demonstrate this feasibility, a typical micro Gas Turbine (mGT) is extended with a solar tube receiver and a solar-powered compressor. By combining this novel mGT cycle with a desalination unit, waste heat from the outlet can be recovered, resulting in a dual purpose plant producing electricity and water. This paper covers the modelling of the novel mGT cycle, based on the Turbec T100 mGT, and the design of the desalination plant, including sensitivity and exergy analysis. Including renewable energy in the mGT reduces the fuel consumption significantly, resulting in an increase in electrical efficiency by 3.2 % absolute. For the desalination plant, the Multi Effect Distillation with Thermal Vapour Compression (MED-TVC) process is found to be the most suitable technology. The sensitivity analysis indicates that varying the feed water mass flow rate allows to regulate the brine salinity and the thermal driving force, while the entrained steam mass flow rate and motive steam pressure are the significant parameters to maximize the exergy efficiency. Based on these findings, three designs are extracted for the MED-TVC, each of them making a trade-off between lower plant size and higher performance. These designs demonstrate the viability of this dual purpose plant as a renewable DMG system, being able to meet the demand of energy and potable water. © 2018 University of Minho. All rights reserved.