Thermal energy storage systems capture low-cost energy from the power grid during the night ("off-peak") and then use this captured low-cost energy to replace high-cost cooling energy during the following day ("on-peak").
Thermal energy is normally stored at the point of use and committed to a specific purpose, for example, hybrid cooling systems for buildings. Essentially the more plentiful off-peak nighttime electricity is committed to cooling and freezing a solid block of ice which stores cooling energy. The cooling energy is released for later use by reversing the proceedure ( melting the ice).
During the "off-peak" charge cycle the chiller circulates a cold glycol/water solution through the thermal storage tanks. The solution flows through the tank's heat exchanger tubes (immersed in water), forming ice around each tube. When the thermal energy storage system is fully charged a solid block of ice is formed and the chiller shuts off until the next cycle.
During the "on-peak" discharge cycle, the warm glycol/water solution is pumped through the thermal energy storage system where it is cooled by the melting ice. The cooled solution is then circulated to the building load through a plate-and-frame heat exchanger to provide cool air capacity during the time of the discharge cycle without the need to operate the chiller at all, or at reduced operational cycles thus saving considerable energy.
Energy savings can be achieved
As much as half of the energy consumed in a commercial building is used for cooling and heating and by using properly designed Thermal Energy Storage Solutions often up to 30 - 40% of this energy use can be saved and reductions in use of high-cost peak demand electricity can be achieved.
The ROI is also very reasonable, especially when combined with other energy efficiency measures to create a cost competitive, environmentally friendly HVAC solution.