Thermal Storage Systems - Remarkable Resilience from a Sustainable Footprint

thermal energy storage, commercial hvac

One of the biggest challenges building owners face is contingency planning. Hurricanes, floods, tornadoes, and acts of terror are just some of the disasters that make lasting physical, financial and emotional impacts on buildings and their occupants. As we are seeing in real-time, from Texas to Puerto Rico, the long, painful process of replacing power, water and cooling commands headlines after the storms have passed. Inability to restore comfortable building climates extends the suffering of those affected and hampers any return to normalcy. Buildings owners and operators should spend time now   reviewing systems and creating or improving their contingency plans while striving to increase sustainability.

We spend roughly 90% of our time inside structures, and these structures require cooling to offset heat generated by us, our computers, lighting, and the ambient temperatures outside. Most cooling systems demand electricity during peak-demand periods. These demands are usually > 50% of the entire energy demand of the building. Cooling structures is the main driver for emergency power sizing, peak-demand utility charges, power blackouts and brownouts. With populations rising, ambient temps warming, and the utilities slow to build new power plants, we need to move quickly to create more resiliency in our electrical grid and adopt systems which can recover quickly from natural disasters and put us on a path to de-carbonizing the U.S. energy system.

The world of energy is going through a transformation, creating new opportunities and challenges for both the building owners and the utility providers across the country. The broad adaption of different energy storage technologies are redefining how the electricity supply and demand are managed. Thermal storage systems can:

•           Reduce costs– by shifting building electrical load to reduce peak demand charges, so building performance is fully optimized and monetized without an undue sacrifice on tenant comfort.

•           Improve resilience– by coupling renewable, distributed energy resources (DER) technologies and energy storage solutions allow buildings to minimize dependence on the grid in case of a disruptive event. Many subsidies are paid to buildings, communities, etc. who have the ability to “island” for a defined period of time in the event of a disaster or disruption.

•           Reach higher sustainability goals – by optimizing efficiency and managing energy sources as well as minimizing environmental impact associated with carbon intensive peaker plants.

Thermal energy storage is one solution to many different problems, and its cost is very attractive and stacks well with other emerging technologies. Although thermal storage systems have been used for decades, their story has never been more important. Last November, UC Davis presented research that addressed the accurate valuation of thermal energy storage devices at the ESA Studio event in my hometown of Cleveland, Ohio. Click to learn more about the research and the event.  

Types of thermal storage systems

Thermal storage systems make tanks of ice or chilled water by running the HVAC chillers at night when energy prices are lower, cooling loads are lower, and ambient temperatures are lower. Air-cooled chillers are ideal for making ice, because they experience a bigger efficiency improvement at night, and they typically use a compressor designed for more difficult duty. Water-cooled centrifugal chillers specifically designed for ice-making duty are used for larger projects and for chilled-water storage.

These three combine to make the cost per ton-hour of cooling lower at night than during the day. During the day, melted ice or chilled water cools the building, leading to significant savings on utility bills and reduced demand for “dirty” peaker plant operations.

Many system designers recommend excess capacity or oversized chillers, which leads to higher initial and maintenance costs. By moving some of the system redundancy into thermal storage rather than excess or oversized chillers, systems using air-cooled chillers with ice storage have increased emergency cooling capacity, with competitive or lower first cost, and lower maintenance and water costs. Combining thermal storage with micro-grid style building batteries could allow a buildings’ cooling and lighting to operate hours after a catastrophe driven blackout.

Benefits even when something bad doesn’t happen

Most solutions to a contingency problem don’t offer payback unless something bad happens. That’s not true of thermal storage systems. Shifting the hours of chiller operation lowers energy, water and maintenance costs. For additional benefits of thermal storage sustainability click here. Building owners with thermal storage enjoy up to 30 percent operating cost savings. Buildings that have predictable peak power help the utility company manage resources, and monetary incentives encourage systems that provide that energy use pattern.

Sustainable footprint

It is widely accepted that any holistic attempt to tackle climate change must confront building-sector energy use. Additionally, current market trends show environmentally focused owners use thermal storage to support sustainability goals and attract tenants. Shifting energy demands to off-peak hours reduces the burden on the power infrastructure and allows power companies to use the most efficient power plants to provide that power. The marginal, peak power generated on a hot summer day is the dirtiest and least efficient.1 As society pushes for healthier, highly efficient and cost-saving green buildings, thermal energy storage stands out as a path to reduce the carbon footprint of our structures and earn LEED® innovation-in-design and energy cost saving points, and higher Green Globes ratings.  

Purchasing considerations

Thermal energy storage systems are cost- and energy-efficient ways to reduce power demands, and provide reliable cooling to tenants and processes. The LEED certified building at our corporate campus in Davidson, NC has a thermal energy storage system in the front yard. We are proud to highlight not only thermal storage, but an innovative and proprietary packaged “completion” module which allows the chiller to talk to the Calmac ICE tanks and the building in a plug-and-play fashion. Inside, user-friendly controls display the system operation via a large flat screen in the lobby. This combination of thermal energy storage, controls, and packaged pump module mitigates risk, adds to resiliency and earned us LEED Gold Certification after a deep retrofit of the existing structure was completed with the local Trane office working with Mechanical Contractors Inc. in 2016. Visit trane.com/energystorage to learn more.

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