Optimizing cogeneration and desalination plants by incorporating solar energy

Abstract

Typically, desalination facilities are integrated with thermal power plants that include steam turbines, simple-cycle gas turbines, and combined-cycle gas turbines. Desalination is accomplished using the following technologies: thermal (multistage flash desalination and multiple-effect evaporation) and membrane (reverse osmosis). Because of the significant economic and environmental impacts of power generation and desalination, there is a critical need to optimize costs and to reduce emissions, especially the carbon footprint. Solar energy is a promising approach to reducing CO2 emissions. The goal of this study is to minimize the total annual cost for desalination facilities powered by thermal power plants, photovoltaic arrays, and battery storage. A single-objective nonlinear optimization approach addresses economic and environmental factors. A multi-period strategy accounts for seasonal variations in energy consumption, water consumption, solar energy supply, fuel prices, and fuel availability. The model is applied to a case study on the water-energy nexus for desalination-power plants in Kuwait. The optimization scheme selects from among various types of fossil fuels: natural gas, gas oil, heavy fuel oil, and crude oil. The study includes optimization with implementation of a carbon tax and constraints on CO2 emission. Over a tax range of $20–120/t CO2, the optimal solutions have a constant capacity of the photovoltaic array. Above $120/t CO2, a sharp increase occurred in the array capacity, and all power was generated by the array.