At a time when we talk more and more about the environment and rationalization of energy use, thermal energy storage represents a technical solution adapted to industrial cooling and air conditioning systems. Office building cooling loads often peak at a level two or more times higher than the daily 24-h average load. Some industrial processes also have load peaks or “spikes”; that rise much higher than the average load. In addition, many electric utilities impose demand charges based on the customer’s highest power demand during on-peak hours and/or during the entire billing cycle. The STL is an ideal and efficient solution for these applications.

Traditional refrigeration systems are designed to satisfy the peak cooling demand, which occurs only a few hours per year, and thus spend their operational life working at reduced capacity and low efficiency. The STL, which is suitable for any air-conditioning system or refrigeration plant, allows installed chiller capacity (and size of other components) to be significantly reduced – typically between 40 and 60%. The STL thermal energy storage system provides the shortfall of the energy when demand is higher than the chiller capacity. Thus chiller operation is continuous and its efficiency is at a maximum. This is the most effective way to reduce operating costs of process refrigeration and building air-conditioning and to take advantage of lower cost off-peak electricity and to reduce the demand charge by reducing the required electrical supply. The STL allows real management of the cooling energy according to the demand.

The reduction in the chiller size also reduces the quantity of refrigerant used, a point that is more and more important with the new restrictive laws on refrigerants. In addition, the STL allows the consumption of night-time electricity produced with a higher efficiency (2 300 kcal/kWh compared to 3500-4000 kcal/kWh at peak hours). The result is a reduction of CO2 emissions and a saving of energy.