Overview
The State of Michigan Secondary Complex, located in Dimondale, Michigan, is a 13 building campus comprised of the state’s police academy and police post, test and research labs, office space, warehouses, vehicle maintenance service garages, and more. The facility’s original energy center was constructed in 1975 and featured electric chillers and gas fired boilers. Since the original installation of the energy center, buildings within the complex have undergone renovations, additions and changes in functions, resulting in a major impact to the efficiency of heating and cooling operations. Energy consumption used for heating, ventilating, and air conditioning (HVAC) was identified as a significant part of the operating budget, which could yield large returns through strategic energy efficiency upgrades.
Challenge: Public Act (P.A.) 295
In October 2008, the State of Michigan made its commitment to energy efficiency well known through a series of bills, among which was Public Act (P.A.) 295. This act renewed and revised the state’s dedication to maximizing energy efficiency in state facilities. One of the goals set in the act was the reduction of state government grid-based energy purchases of 25 percent by 2015 compared to a 2002 baseline. Two strategies that were outlined to meet this goal included reductions in peak demand and on-site energy generation. The choice to implement cogeneration and energy storage technologies into the State of Michigan’s Secondary Complex would greatly reduce the facility’s operating costs and environmental impact therefore contributing to meeting the state’s energy goal.
Solution: The Integration of Cogeneration & Ice-Based Energy Storage
The Secondary Complex’s energy center underwent a major renovation in 2012 with the installation of two 1.2 megawatt natural gas fired turbine generators to produce steam and electricity for central heating and cooling operations at the Complex’s central facility, thus reducing the amount of power required from the state’s power grid. Steam generated from the turbines was dedicated to heating the over 2,000,000 sq.ft. complex and was also utilized by two absorption chillers to create chilled water for cooling operations. However, since the installation of cogeneration, the cooling load requirement within the campus has increased due to the addition of new buildings, technology and equipment. As a result, the complex identified the need for a capacity and efficiency solution that could seamlessly integrate into its existing energy center, reduce peak demand, and create redundancy within system.
Having thermal storage and CALMAC tanks at the Saginaw State Office Building, the state has experience with ice-based thermal energy storage’s reputation for creating savings and providing a durable, long-lasting solution. As an industry leader, CALMAC was chosen for providing the energy storage technology that would meet the complex’s growing cooling demands. In 2014, the Secondary Complex installed three 900-ton centrifugal, dual-mode, water-cooled chillers provided by Nelson Trane plus Trane Tracer™ chiller controls. The chillers operate using energy from the grid and were paired with CALMAC’s IceBank® energy storage tanks that can store 1MW of energy, equivalent to 8,748 ton-hours of cooling. Two levels of energy storage tanks were installed in a storage area that had previously been an incinerator room before being decommissioned.
Although there is enough energy storage to satisfy the cooling load for the entire complex if necessary, the system is designed to provide redundancy to the cogeneration plant. When steam is available for cooling it must be utilized since this form of energy cannot be stored effectively. If cooling demand exceeds the capacity of the steam driven chillers, CALMAC’s IceBank® tanks are called upon to provide the additional cooling requirements. With the extra storage capacity available, the State of Michigan is prepared to handle future increases in cooling demand.
“CALMAC’s energy storage technology has allowed us to make our system extremely flexible in order to meet changing heating and cooling needs,” said Scott Davis, Facility Supervisor Zone 6. “Utilizing cheaper nighttime energy has always been an attractive opportunity, especially for a large complex like ours. Now it’s a reality.”
Results
The incorporation of ice-based thermal energy storage has allowed the Secondary Complex to create cooling hours during nighttime off-peak hours, when only the most efficient power plants are online and the price of electricity is reduced by roughly 50 percent compared to daytime prices. By storing and using cooling as needed, the complex can avoid expensive peak demand hours and reduce stress on the power grid. Based on historical data, the addition of storage is expected to save an estimated $12,000 per month in energy costs. Ice-based energy storage also adds a significant amount of flexibility into the system.
The complex has the option of cooling the facility using just ice, the absorption chillers that are powered by steam, the three centrifugal chillers, free cooling heat exchangers or any combination of the listed solutions. However, the energy plant heavily relies on the cogeneration technology, which powers the absorption chillers, with the ice-based energy storage assisting as needed. The ability to use the cogeneration and natural gas to remove some of the complex’s load off the grid is helping to meet the state’s goal of reducing grid-based energy purchases. When the Secondary Complex does need energy from the grid, energy storage is allowing the facility to only use the most efficiently produced energy.
Summary
The combination of cogeneration and ice-based energy storage has provided the State of Michigan with technologies that perfectly align with their goals of reducing its reliance on the power grid, while optimizing operating costs. The proactive approach to creating a long term solution has also prepared the state for future changes in demand. The savings generated from the two technologies can be used on other facility related costs.
“Ice-based energy storage has allowed the State of Michigan to separate when energy is purchased from when it is consumed,” said Mark MacCracken, CEO of CALMAC. “This decoupling in combination with cogeneration has greatly reduced its energy usage during peak demand hours. Historically off-peak energy pricing rises much slower than any other form of energy. “
