Thermal Storage Tanks
Underground Thermal Water Storage Tanks
THERMAL ENERGY STORAGE – Darco underground fiberglass tanks are used for storing energy in the form of cold or hot water. Cold water created by evaporative coolers or mechanical compressors may be efficiently stored in an uninsulated underground cistern due to the constant cool soil temperature 10 feet below grade. Hot water is collected from solar panels or another heat source and stored in insulated fiberglass tanks either below or above ground. Heat pump systems can use stored water to extract heating or cooling energy as needed depending on the seasonal daily temperatures.
Thermal storage tanks commonly use diffuser manifolds and transfer water directly into and out of the storage tank. Chiller systems can use a single naturally stratified tank, a 2-tank warm / cool storage system, or a multiple tank cascade design as illustrated. Compressors run during off peak evening hours when electricity costs are lower. Cold water is then circulated to provide cooling during the following day while the compressors are at rest. Cold water can be applied directly to the building by fan coils or used to reduce the temperature of return water entering a mechanical chiller. In certain parts of the country, evaporative cooling can assist or even replace mechanical compressors during the shoulder seasons. Darco also offers an ice slurry system that greatly reduces the water volume per ton of storage due to the phase change gain of melting ice. The beauty of cold-water storage is its simplicity and freedom from maintenance.
Insulated hot water storage tanks hold water up to 150º F. The key to efficiency is maintaining the highest practical water temperature and volume, while using natural stratification to provide the highest discharge water temperature. Darco underground and above ground Solar Storage Tanks are insulated and are available with various styles of exchangers or diffusers.