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Driving down the costs of solar-powered electrodialysis desalination, drip irrigation, and the combination of the two
 
 
 
 

Driving down the costs of solar-powered electrodialysis desalination, drip irrigation, and the combination of the two

 
Amos Winter
 
Global Engineering and Research (GEAR) Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Technology ,USA
 
 

This talk will present innovations from the MIT Global Engineering and Research (GEAR) Lab to aggressively reduce the costs of solar-powered desalination and drip irrigation, with the aim of making the technologies affordable for resource- constrained, off-grid markets throughout the world. Community-scale electrodialysis (ED) desalination systems for brackish groundwater require half the specific energy, and produce one-third the water wastage, as reverse osmosis (RO) systems. GEAR Lab has created PV-ED control and system optimization strategies, whereby the pumping flow rate and electrochemical power are actively controlled to match available solar irradiance. We have demonstrated that these PV-ED systems can directly utilize 76% of captured solar energy, need minimal to no battery capacity, can produce water 54% faster than an equivalently-sized PV-ED system that runs on constant power, and can meet near price-parity with on-grid RO (inclusive of the cost of the PV power system) in terms of levelized cost of water. In a parallel research effort, GEAR Lab has created ultra-low pressure, pressure- compensated drip irrigation (DI) emitters to reduce required pumping power and facilitate solar-powered irrigation. These devices were realized by creating predictive, parametric design theory to describe the fluid-structure mechanics within the emitter that control water flow, to minimize activation pressure. During two years of field pilots in Jordan and Morocco, GEAR Lab’s emitters have demonstrated >50% pumping power reduction while maintaining required water distribution uniformity compared to standard products. They can reduce the cost of a solar-powered DI system by 40% compared to current industry design practice. Our team is currently embarking on co-optimized desalination-drip systems, which show promise for economic viability because of the combined energy and water savings achieved through the PV-ED and PV-DI subsystems.