St. Lucie District Uses Energy Storage to Save Millions in Utility Costs

CALMAC today releases the results of St. Lucie School District’s (SLCSD) energy cost reduction strategy using ice enhanced cooling. Over the past seven years, the district of 40,000 students and 5,000 employees has installed CALMAC’s IceBank® energy storage tanks in 15 schools to cool students and employees. SLCSD energy management program has created a 30-40 percent reduction in annual energy costs, totaling about 5 million dollars in savings, or the equivalent to 100 annual teacher salaries.

“The CALMAC IceBankenergy storage tanks are a main ingredient in our energy program,” said Marty Sanders, P.E, executive director of facilities.

Before implementing CALMAC’s thermal energy storage solution and other energy efficiency upgrades, SLCSD was ranked 60th of the 67 county school districts in terms of energy costs per square foot within the state. Now, the district ranks among the top 20.

“We did our homework and looked at a variety of technologies,” said Sean Murray, energy manger of the St. Lucie School District. “We chose CALMAC’s tank based on a superior design and operation of those tanks. Our board is thrilled with the energy cost savings, and now, we have other school districts, county governments, and colleges wanting to understand what we did here.”

Two different utilities, with different rates structures, currently supply SLCSD with energy. This led to the use of partial and full energy storage systems among the different schools in the district. Centennial High School installed a full energy storage system to take advantage of incentives that cover most of the cost of installation. Enough cooling is stored in the form of ice during the night, when demand is low and prices are at their lowest, to cool the campus from noon to 9:00 p.m., without assistance from the chiller. As a result, the school has seen a 50 percent reduction in cooling costs, saving $300,000 per year.

Partial energy storage systems are used in the district for schools that do not have incentives, but instead have a differential between day-time and night-time electrical costs due to a $10 per kW demand charge. Partial storage is the most common type of thermal energy storage installation, providing a fit for buildings that do not have incentives to cover the cost of adding enough energy storage to offset the entire cooling capacity and for buildings that pay demand charges, which are essentially a form of time of use rate. Facilities with partial storage have smaller, more efficient chiller equipment, that work in tandem with the ice-based thermal energy storage, to cool occupants during peak periods throughout the day, thus reducing demand charges. Using this strategy, Lincoln Park Academy, for example, was able to lower energy costs by $334,000 within the first year of installation, a 32 percent reduction in cooling costs.

“Ice-based energy storage technology works similar to hybrid cars,” said Mark MacCracken, chief executive officer of CALMAC. “Full storage acts like a fully electric car that relies solely on stored energy. A partial storage system works like a hybrid car. The chiller acts like the smaller engine in the hybrid car and switches on and off as needed to assist the storage in meeting the entire load. Use of partial and full energy storage allows schools the flexibility to take control of utility costs and use the savings in important areas, such as teacher salaries.”