SBIR-STTR Award

Secure sources of clean fresh water are essential to the welfare of communities throughout the world. To meet the growing demand for fresh water, communities are increasingly relying on large-scale desalination plants. Unfortunately, the source of energy to run these plants has almost always been fossil fuels. This project will develop a desalination technology that runs primarily on solar energy and can be economically competitive with fossil-fuel based systems. All thermal desalination processes first evaporate seawater and then condense the water vapor to produce freshwater. The new approach will employ a novel configuration for the evaporator and condenser, which will: (1) eliminate the need for large, costly vacuum shells; (2) convert the shells from expensive metallic heat exchangers to low-cost, corrosion-resistant plastic heat exchangers; and (3) retain high efficiency when a solar thermal energy source. In addition, a solar collector, designed specfically for desalination applications and much less expensive than conventional collectors, will be developed. Phase I will include: small scale bench-top experiments to both optimize and prove the performance of the novel evaporator/condenser; a proof-of-concept demonstration of a low-cost solar thermal collector, which is integrated into the desalination plant; a conceptual design for a full-scale plant; and an estimate for the cost of producing water from this plant.

Commercial Applications and Other Benefits as described by the awardee:
In addition to desalination, the technology also should be applicable to the purification of brackish water - which would be extremely important in the Southwest, where economic growth is straining water supplies and brackish water is frequently available. By efficiently producing mineral-free water, the novel desalination technology also could increase the use of high-efficiency evaporative coolers for HVAC 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.