Thermal Regulation with Salt Hydrates for Biodigester Isothermality

Advanced Cooling Technologies Inc. (ACT) proposes the development of an advanced lowcost insulation solution for small scale anaerobic digesters (AD) that relies on a salt hydratephase change material (PCM) to improve passive digestate temperature control and thereforesignificantly boost methane production while using the inherent thermal storage capability ofPCM to enable the use of unsteady thermal energy sources for digestate heating. The proposedimprovements will increase the biogas and high-quality fertilizer production rates of ADs whilereducing the levelized cost of produced biogas in most scenarios. ACT has developed severalPCMs for a variety of applications and intends to use the salt hydrate calcium chloridetetrahydrate (CaCl2·4H2O) in the proposed solution due to this material's low cost ease of usehigh energy density and relatively high thermal conductivity.Furthermore life tests conductedat ACT on this material demonstrated excellent stability for extended life cycles.This feature isimportant for reducing material and maintenance costs over the life of the AD.The proposedresearch will apply this technology to digesters specifically designed for small farms andcommunities as these groups stand to benefit the most from a lower cost anaerobic digestionsystem. ACT is partnering with SolarCITIES a non-profit charity that focuses on deliveringbiogas solutions to test the proposed thermal solution on a homestead farm scale AD.