Thermal Energy Storage

Ice-based thermal energy storage (TES) is a system that stores thermal energy. This stored energy can be used for cooling and/or heating in a variety of commercial and industrial applications. Thermal energy storage helps shift energy consumption from peak to off-peak hours, reducing energy costs and alleviating stress on the electrical grid.

Thermal energy storage works to provide cooling in a three-step process:

1. Ice Production: During off-peak hours (usually at night), electricity is used to freeze water in a thermal energy storage tank, creating ice using chillers.;
2. Energy Storage: The ice acts as a thermal battery, storing the cold energy until it is needed.
3. Cooling Application: During peak hours (typically during the day), the stored ice is melted to provide cooling. The cold water or air produced from the melting ice is circulated through the building's HVAC system to cool the indoor environment. 

Thermal energy storage works to provide heating through the process of heat recovery.

Cold water contains a lot of heat. Water becomes ice when that heat is removed. Buildings, even in the winter, have lots of waste heat, which can be recovered and saved by melting ice in the thermal energy storage tanks.

Heat pump chillers remove the heat from the cold water, lift the heat to a high temperature level, and use it to heat the building. Advanced thermal management systems integrate ice-based TES with heat pump chillers, to maximize heat recovery, reducing electrical demand, carbon and energy costs.

Today, electricity mainly comes from coal and gas, which are forms of stored energy. Renewable energy is variable; the sun doesn’t always shine and the wind doesn’t always blow. As more wind and solar are generated, we will need to move toward technologies that can store and dispatch renewable energy for later use. Thermal energy storage is one such technology. According to ASHRAE Research Paper 1607, thermal energy storage can increase the usage of renewable energy by up to 50%. The move toward sustainability and renewable resources will completely change the potential value of thermal energy storage in buildings.

(Plumbing Systems & Design. Making Buildings More Efficient with Hybrid Cooling. September 2010).

Electrification of heat is coming, so a building that can shift its electric consumption to leverage the supply will be very important. The advantage of an electrified building is, that as the grid gets cleaner, the building’s carbon emissions will go down proportionally. If the building burns fossil fuels, the associated emission stays the same. Understanding heat pumps, and thermal energy storage’s relationship to them, will be critical. (ASHRAE Journal. Electrification, Heat Pumps and Thermal Energy Storage. July 2020).

With the increasing demand for warm thermal energy storage, scientists at Lawrence Berkeley National Laboratory are looking at developing next-generation materials and systems to be used as heating or cooling mediums. They are also creating a framework to analyze costs as well as a tool to compare cost savings.

(Berkeley Lab. Turning Up the Heat: Thermal Energy Storage Could Play Major Role in Decarbonizing Building. November 18, 2021).

Advances in intelligent services enable building operators to see how their system is operating and trends that may impact future performance as conditions on the grid change. Connected chillers and building automation systems have made thermal energy storage systems smarter and easier to monitor and control. Built-in control algorithms allow building operators to helping to achievecost savings, reduce emissions, or both. Design aid tools provide a repeatable approach with simple schematics and sequences to help reduce time and risk.