Energy storage at the State of Michigan Secondary Complex

October 1, 2015

One of the most well-known applications of energy storage is the ability to shift energy demand from an on-peak time to an off-peak time. The ability to shift energy demand is important because electricity is less costly after sundown. Buildings capable of taking advantage of those lower nighttime electricity costs are rewarded with a more cost-effective facility. But what if the building relies on on-site generation? How does energy storage ensure reduction of grid based energy purchases and provide redundancy during building expansions or increases in cooling load?

An ice approach to thermal energy storage
When the cooling load requirement at the State of Michigan Secondary Complex grew and expansion of the chiller plant deemed prudent, the Complex sought out a seamless solution that would minimize operating costs and adhere to the State's Public Act 295. Part of this Act dictated that the Complex maintain a 25% reduction of grid-based energy purchases. The Complex had already incorporated a co-generation system to generate steam for heating and cooling, thus reducing the grid reliance, however the addition of new buildings, technology and equipment meant additional cooling equipment was needed to meet the growing building requirements.

The State of Michigan Secondary Complex decided to take advantage of thermal energy storage technology that uses ice as a storage medium, said Business Energy. Ice storage works especially well in conjunction with standard air-conditioning chillers as part of a money-saving HVAC system. Chillers run at night to take advantage of low electricity costs, creating ice instead of only cooling the buildings or campus directly during the day. The chillers shut down partially or completely once the sun comes up, allowing some or all of the cooling to be done by ice created and stored the night before in storage tanks. During the day, coolant cooled by ice flows throughout each building on campus to keep occupants cool.

Shifting peak loads at the Secondary Complex
The technologies that allows the Secondary Complex to store low cost off-peak power electricity was provided courtesy of air-conditioning experts at Nelson Trane and their energy storage partner CALMAC. Nelson Trane provided three 900-ton centrifugal chillers, while 1 MW worth of energy storage capacity was furnished by CALMAC in the form of the company's signature IceBank® energy storage tanks. Capable of installation in versatile environments, CALMAC's energy storage tanks eventually found a home in one of the abandoned storage areas that had once been an incinerator room.

While the Nelson Trane and CALMAC solution offers more than enough capacity to serve the cooling load of the entire Secondary Complex, the equipment was instead designed to backup the facility's cogeneration plant. Primarily using CALMAC's IceBank® energy storage technology in this peripheral way allows the State of Michigan Secondary Complex to enjoy some extra insurance against increases to cooling demand that may occur in the future. That added flexibility has benefits beyond worst case scenario  peak load situations too.

Ice tanks deliver noticeable results
The chilling impact of thermal energy storage installed at the Secondary Complex has been nothing to sneeze at. Based on previous utility costs, the facility's new storage upgrades will contribute up to $12,000 in monthly savings. Another benefit is it's flexibility in performance. Operators at the Secondary Complex can switch between ice, free cooling heat exchangers, centrifugal chillers and absorption chillers in any combination, depending on the energy need of the facilities and the price of energy commodities. In addition, ice storage supplements the cooling provided by the steam driven chillers when the load on the building's campus grows overly burdensome. This technology ensures that the State of Michigan Secondary Complex has access to a highly cost-effective method of cooling and reduces reliance on the electric grid while adhering to the State's Public Act 295.