Thermal Energy Storage is the Answer The question – How Do We Solve the Demand on the Grid?

Posted on April 13th, 2012 by

The future of energy and the Smart Grid is dependent on smarter buildings that use disruptive technologies such as energy storage and building automation to be more efficient. 

Demand on our power grid continues to rise. Last summer, the East Coast experienced a massive heat wave that set record high temperatures in multiple states and caused over thirty heat-related deaths. Record high temperatures naturally led to increased use of air-conditioning, and a major strain on utilities up and down the Atlantic Coast. The strain became apparent when New York City had power outages and buildings were dimming lights and turning off unnecessary equipment in order to avoid overloading the grid. The problem of rising energy consumption has increased the importance of utilizing efficient energy storage. Many commercial buildings, one of the largest consumers of energy in the United States, are using over-sized inefficient “just in time” cooling systems. During the summer, most of a building’s energy costs are due to air-conditioning, typically during daytime hours, when demand is high. Although these over-sized systems have become more efficient, they do not provide a viable long term solution to reducing demand on the grid. They are a short-term solution for immediate cooling needs during warmer months.



An alternative to large cooling systems is the use of thermal energy storage. Thermal energy storage (TES) is proven, reliable and the cheapest form of energy storage, yet it is rarely mentioned as part of the energy storage solution. TES tanks store energy in the form of ice, chilled water, hot water or a chemical and water mix. This stored energy can then be used later when the air-conditioning system experiences high demand. For example, ice thermal energy storage systems will use electricity during the low demand hours to produce ice, which is stored in tanks. The next day, the stored ice is used to cool the facility when building temperatures rise due to high outdoor temperatures, direct sunlight, occupant body heat and the use of machinery and electronics. The comfort of building occupants is never compromised and relative humidity within the building is actually lowered. Meaning the temperature in the building can be higher without the occupants feeling the heat.

We can compare TES to something everyone is familiar with – hybrid cars. Standard cars have oversized engines for when there is a larger load or a burst of speed is needed for merging and passing on highways. Hybrid cars have smaller engines, which provide greater efficiency and an adequate amount of power. When more power is needed, the stored energy is used to provide the necessary burst of power or the stored energy can be used when traffic is creeping along or at idle for even better efficiency. Commercial cooling with TES is similar. Engineers design cooling systems for peak design days and unanticipated cooling loads. This results in large cooling systems with large supporting infrastructure. Adding storage into these designs allows smaller “cooling system engines” to be used that are more efficient over a wider operating range. When prices are high, or the load is great and a boost is needed, the storage provides capacity. Similarly, when loads are small (at idle or creeping along) the entire cooling load can be supported with low cost stored energy. The connected load is smaller, which is good for everyone, while the safety capacity is provided by storage.  The capital for storage comes from installing a smaller electric chiller and support equipment.

TES is beneficial to the environment too. Utilizing TES reduces the amount of source energy and emissions being released into the atmosphere. TES uses night-time energy.  A larger component of nighttime electricity is renewable wind generation. This night-time energy is also more efficiently produced by base-load generation plants. Discharging stored cooling during peak demand hours means utilities don’t have to turn on the peaking plants which are usually the oldest and dirtiest utility assets. These peaking plants only come on to meet peak demand mainly caused by air-conditioning.

Not only is TES beneficial to the environment, it saves users money. Grid operators, more and more rely heavily on variable pricing to change consumption to reduce peak demand. As such, demand response revenue opportunities are increasing for users that can shift or change consumption. The price of electricity during daytime hours, when the power grid is reaching maximum capacity, is increased in order to discourage use and relieve stress on the grid. On the other hand, the price of electricity is lower during the nighttime hours when demand on the power grid is at its lowest and supply the greatest. The Edison Electric Institute has said that the only form of energy that has not increased in cost in the last 40 years, when converted to today’s dollars, is off-peak electricity. The next logical step for commercial buildings to hedge against price increases and energy pricing volatility is to shift as much energy consumption to off-peak hours when utility demand is lower and rates are less expensive. Shifting cooling off peak can result in a savings of up to 40 percent in cooling costs.

TES does not diminish the importance of grid energy storage technology, but complements it for greater energy efficiency. The HVAC industry as a whole needs to design technology that is able to be better integrated into the Smart Grid. Changes need to be made now in order to help manage our future energy consumption. Afterall, you can’t have a smart grid with dumb buildings.

In closing, I’ll leave you with a quote from CALMAC CEO Mark MacCracken, said at last year’s Danfoss EnVisioneering Symposium, “The Grid, Systems & Buildings: A Glimpse Over the Horizon” – a roundtable discussion that examines standards, smart buildings, existing and emerging technologies, energy storage and policy:

“Even though a true smart grid may be on the horizon, action by manufacturers, contractors, utilities, and policy makers is needed today. As an industry, we need to encourage the designers to specify the available technology and equipment that is able to be integrated into the smart grid. If it is not being installed now, we’re setting ourselves back by not getting the equipment into place for the future.”


The opinions expressed in this article are solely those of the author Paul Valenta, is Vice President of Sales and Marketing for CALMAC. For more information, visit

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