Progress 09/01/18 to 10/31/19

Outputs
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? The agricultural sector is the largest freshwater consumer, withdrawing 70-75% of available freshwater. Along with dramatic population growth and improved living standards, existing freshwater supplies are deteriorating. The freshwater needed for irrigation is therefore frequently replaced by marginal quality water, such as brackish groundwater, waste or drainage water, which may degrade the farmland if improperly used. In the long run, irrigation by brackish water may alter soil characteristics, thereby reducing productivity. In this SBIR Phase I, Advanced Cooling Technologies, Inc. (ACT) developed a low-cost, high-efficiency condensation irrigation system to desalinate brackish water and provide affordable freshwater for agricultural applications. In this technology, solar thermal energy or low-grade heat is used to vaporize water from brackish water and humidify air; the hot humid air is sent to the buried perforated condensation pipes and condensed in the pipes to supply fresh water directly to the roots of the crops. To further improve the thermal efficiency and uniformity of the condensation irrigation, a concentric pipe design is used to exchange and recover heat from hot humid air to cold brackish water. The recovered latent heat of condensation pre-heats the cold brackish water and reduces required solar energy for desalination, saving the agricultural land area needed for solar collection. This thermally enhanced condensation irrigation (TECI) maintains the following technical and commercialization features: Enables the use of brackish water for irrigation in areas that lack fresh water resources for high value crop yield; High solar energy utilization efficiency due to heat recovery during condensation; Reduced solar area required, leading to competitive pricing for brackish water irrigation. In the Phase I project period, the design requirements were established and a 1-D simulation of the condensation-preheating process in the buried concentric pipes with a variety of fluid flow rates was studied. The simulation study demonstrated that the freshwater production in the pipes is sufficient for irrigation applications with the specified flow rate of humid air and cool brackish water. The uniformity of water production along the pipe is better than conventional SCI system. In addition, the water productivity increases significantly with increased pipe thermal conductivity, indicating that pipe material needs to be selected to balance the requirement of low cost and high freshwater productivity. The condensation irrigation experimental prototype developed at ACT performed exceptionally. Water generation for the TECI system was consistently greater than predicted by the model. This experimental success requires further investigation in Phase II to develop a viable product for market penetration. Producing freshwater from brackish water and supplied as the water source for farmland irrigation is an obvious solution for the lack of irrigation water, and may potentially increase the availability of irrigated farmland area using unconventional water resources with higher salinity. By adopting the proposed TECI system with the use of low-cost solar thermal resources, it will make fresh water from the brackish water available for irrigation at a reasonable cost, while avoiding the degradation of farmland by brackish water.

Publications