Reducing electric energy consumption in linear Fresnel collector solar fields coupled to thermal desalination plants by optimal mirror defocusing

Mohamed Alhaj,Sami G Al-Ghamdi

doi:10.1016/j.heliyon.2018.e00813

Abstract

In many parts of the world, desalination is the only viable and economic solution to the problem of fresh water shortage. The current commercial desalination technologies rely on fossil fuels and are thus associated with high greenhouse gas emissions that are a major cause of climatic changes. Solar thermal-driven multi-effect distillation with thermal vapor compression is a clean alternative to conventional desalination technologies. To comprehend this process, as well as its features and limitations, extensive modeling is required. In this work, we proposed a plant design based on a solar field with a linear Fresnel collector that supplies heat to a multi-effect distillation plant with thermal vapor compression. The solar desalination plant model is implemented in the Engineering Equation Solver (EES). The system performance is investigated and a control strategy for reducing electric pumping is proposed. Results showed that 1 m2 of the solar field produces 8.5 m3 of distillate per year. The proposed control strategy resulted in a 40% reduction in electric pumping energy. Our results highlight the versatility of the linear Fresnel collector when coupled with thermal desalination.

Highlights

IntroductionIn many parts of the world, desalination is the only viable and economic solution to the problem of fresh water shortage
Providing drinking water is one of the greatest challenges of our times
This study investigated the effect of partial defocusing of the solar field on the solar share

Summary

Introduction

In many parts of the world, desalination is the only viable and economic solution to the problem of fresh water shortage This is applicable to the Gulf Cooperation Council (GCC) region, which has the largest installed capacity of desalination plants in the world, amounting to 38% of the global capacity [1, 2] Most desalination plants in the GCC region operate using multistage flash (MSF) and multi-effect distillation (MED) with thermal vapor compression (TVC). At a global scale, owing to the population increase and increased demand for food, the demand for fresh water will continue to rise This will impose stringent operational requirements on current desalination plants, and will require more plants to be built, which will in turn escalate the demand for energy and fuel. The utilization of the generated vapor in each effect that acts as a heating source for the effect is an energy recovery method that distinguishes the MED and MSF processes. The PR is the amount of desalted water produced by condensing steam at an average temperature corresponding to a latent heat of 2330 kJ/kg

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