Solar thermal wastewater evaporation for brine management and low pressure steam using the XCPC

In this manuscript, the performance of a commercial thermal evaporator powered using solar energy is described. The solar collector, known as the external compound parabolic concentrator (XCPC), is an emerging technology which combines nonimaging optics and metal-glass vacuum tube technology to provide high operating temperatures from a stationary collector. Paired with a commercial thermal evaporator, it provides a renewable heat alternative to fossil fuels for wastewater volume reductions. To assess performance, the team at UC Merced installed a 10 gallon-per-hour (0.037 m3/hr) thermal evaporator and connected it to a 30 kW solar thermal collector field. The solar array operates between 130 and 150 °C, providing thermal energy to drive evaporation for 8 h each day. The single-stage thermal evaporator has a specific energy consumption of 776 kWh/m3. Performance of the array was then used to develop an annual performance model to extrapolate performance for different locations and thermal loads (e.g. other commercial and emerging water treatment and desalination technologies). Extrapolating performance yields an annual thermal generation of ~500 kWhth useable heat delivered to the process load at 150 °C per square meter of solar field, although the team estimates a commercial installation can generate closer to 625 kWh/m2/year. Thus a commercial installation could process 2.5–3 m3 of product water per square meter each year. At these temperatures the thermal energy can also be used to decarbonize a number of other industrial processes such as evaporation, desalination, drying, and more.