Solar Desalination Technology for Mid-Sized Applications

Secure sources of clean freshwater are essential to the welfare of communities throughout the world. Unfortunately, both in this country and abroad, freshwater supplies are increasingly being contested. Faced with threats to growth, economic development, and the health of their citizens, governments are battling over the rights to freshwater supplies. Desalination, particularly if it is powered by a sustainable source of energy, can alleviate this critical shortage. This project will develop technology to dramatically reduce the cost of water from a desalination plant that runs on renewable energy. The novel desalination cycle operates similarly to a conventional multi-stage flash evaporation plant, except that all stages operate at atmospheric pressure. This change allows the expensive metallic heat exchangers and vacuum vessel used in conventional plants to be replaced with inexpensive plastic heat exchangers. A novel configuration for the solar collectors, based on low-cost evacuated-tube collectors, provides most of the thermal energy for producing water. In Phase I, performance data from a proof-of-concept experiment confirmed that the proposed technology could achieve a very high thermal efficiency. The experimental data was used to calibrate a computer model, which predicted that the efficiency of the process would be about twice that of a conventional thermal desalination plant. The cost of water was projected to be less than half of cost of water from competing desalination concepts powered primarily by renewable energy, and competitive with the cost of water from conventional desalination plants. Phase II will build and test a larger model of the desalination concept and operate the model in the field with thermal energy provided by solar collectors. The installed cost for a commercial desalination plant will be developed from a detailed manufacturing cost analysis of the plastic heat exchangers that form the core of the plant. Commercial Applications and Other Benefits as described by the awardee: The technology should allow economic growth in parts of the country that do not (or will not in the future) have secure water supplies. The technology also would improve agricultural and industrial productivity, including the enhanced recovery of oil and natural gas, by greatly reducing the volume of wastewater, which often can have high disposal costs and adverse environmental impacts.