Can soil aquifer treatment be used in parallel for solar energy generation?

Soil aquifer treatment (SAT) is a nature-based technology that typically uses the soil profile for tertiary treatment of wastewater and the aquifer for storage before reuse. SAT facilities, such as that of the SHAFDAN in Israel, are often located near urban regions where land is expensive and scarce. The large surface area and urban proximity make SAT attractive for solar energy generation. This talk explores the potential pros and cons of using SAT system infiltration basins as solar fields. While dual use of agricultural fields and energy harvesting in agriculture is already significantly explored, to the best of our knowledge, this is the first study that explores such dual use in the context of SAT.

Conventional operation of SAT facility includes intermittent flooding of infiltration ponds and periodic plowing of the ponds' soil surface. These are performed primarily to enhance the oxygen content in the upper soil layers and to break the crust formed at the soil surface. Drying periods have their role in degrading that biological crust, and plowing also increases the hydraulic permeability of the upper soil layer. Energy harvesting using solar panels primarily means shifting an SAT pond, which can be considered a biochemical mesocosm, out of its relatively stable ecological state. This may affect the efficiency of SAT in several ways: (1) reduction of the solar radiation (and possibly also temperature) means less algae-based oxygen generation at the pond, which is significant in the SAT oxygen balance and affect C and N specie degradation; (2) it could reduce the natural crust degradation, leading to the need for more frequent plowing; (3) the solar field infrastructure could make the plowing practice somewhat more cumbersome, effectively reducing the plowing efficiency. Altogether, these create a risk of less efficient biodegradation and a reduced infiltration rate. On the positive side, of course, is energy generation near large urban centers. Since the adverse effects mainly depend on the net radiation that reaches the pond surface, an optimum range of solar coverage is to be further investigated.