Storage – An Essential Part of the Grid Equation

Posted on May 14th, 2012 by


Storage is an essential part of the grid equation. Smartgridnews states that energy storage is generally considered a critical tool for integrating intermittent renewables into the electric grid and maximizing their value. The Economist points out that time-shifting would compensate for the intermittent nature of wind and solar power. Everyone agrees that the Smart Grid will require storage as a large piece of the generation mix moves away from fossil fuels in order reduce demand and to capture intermittent renewable energy when it is available for use when it is needed.

The debate is around how exactly that storage will be implemented and utilized on the grid side. One area where the discussion is most active is in California because of the proposed mandate, Assembly Bill 2514, which, if passed, could mandate the use of energy storage technologies throughout the state. (For more about California’s energy storage discussion, take a look at the California Energy Commission’s report, “2020 Strategic Analysis of Energy Storage in California.”)

Also worth noting are the potential incentives for energy storage, some of which have been proposed by the federal government. According to a recent article about the future of energy storage, it was noted that “the Electricity Storage Association is advocating for tax and financial incentives like the investment or production tax credits given to wind and solar, which may not get renewed after this year. It also wants to see energy storage included in the Obama administration’s clean energy standards as well as renewable portfolio standards that are now set at the state level.
“The next five years will be critical and provide enormous opportunity to move storage technologies to full commercialization,” says Brad Roberts, executive director of the storage group.


Ok, but what about THERMAL energy storage?

While there is a broad discussion about energy storage taking place in the local and federal governments, thermal energy storage (TES) seems to be largely left out of the conversations. According to a recent Pike Research report, $122 billion will be invested in energy storage projects between 2011 and 2021, with a bulk of the spending going toward new forms of compressed-air energy storage (CAES). Prominent websites report that large-scale energy storage is making renewables even more cost effective. While other news claims that grid-scale energy storage is still cost prohibitive and large amounts of research money is going into developing new forms of energy storage.

Thermal energy storage (TES) is hardly mentioned in the same breath as chemical storage or pumped hydro or CAES. While TES is distributed energy storage, according to KEMA, TES accounts for almost one GW of current storage capacity. That’s more than twice the capacity of pumped hydro, and more than pumped hydro plus all other technologies combined. TES is proven, reliable, dispatchable, made to last, and the least expensive of all energy storage systems.  Many systems last for over thirty years. In fact, one system available is 99 percent reusable or recyclable at the end of its service life.

TES used in buildings creates a hybrid cooling system similar to today’s hybrid cars. A standard midsized car has a relatively large engine to provide enough power for all situations, even though the car is lightly loaded most of the time. Hybrid cars use smaller, more fuel-efficient engines. When the boost is needed to merge, for example, or the load is heavy, or when traffic is at a crawl, the stored energy is used to optimize performance and efficiency.

On the other hand, conventional HVAC systems have a “big engine” to handle highly variable cooling needs. All support equipment is sized for this big engine even though cooling systems rarely operate at peak capacity. Hybrid cooling systems with energy storage use a smaller “engine” and smaller support equipment. The capital saved is used to purchase and install TES. The stored energy is used when cooling loads are high, electric demand is high, or when prices are high. Typically less source energy is consumed which produces lower GHG emissions, and cooling costs can be cut 20-40 percent.


Thermal energy storage should be part of the solution

To combat limited investment capital, siting issues, demand growth, the switch to renewable energy, and the smart grid, more utility companies are relying on demand-side management such as variable time of day or real time pricing. The price of electricity is set based upon market prices and the laws of supply and demand.  During daytime hours, when the power grid is reaching maximum capacity, prices are higher. On the other hand, the price of electricity is lower during the nighttime hours when demand on the power grid is at its lowest. Furthermore, the Edison Electric Institute (EEI) has said that the only form of energy not to increase in cost, when converted to today’s dollars, is off-peak electricity. The next logical step for commercial buildings is to shift energy usage to off-peak hours when utility demand is lower and rates are less expensive.

Summertime demand is almost completely caused by air conditioning, a load that can easily be shifted with thermal energy storage. According to the New York Times Green Blog prices peak when the sun is high in the sky, because that is when the demand for power, mostly for air-conditioning, is highest. TES is not on the grid side of the meter, but its combined impact can add up to significant capacity in the summer months. Energy is stored at the building in the form of ice over night so that TES can essentially act as a battery for wind power closer to the point of use for better round trip efficiency.

Think of the infrastructure that is saved by the residential use of water heaters that store hot water! Yet many in the commercial building industry and HVAC designers still follow traditional rules of thumb and choose to provide over-sized, just-in-time cooling systems. Work is being done to simplify implementation of TES. Recently, a manufacturer began offering a pre-engineered ice storage enhanced air cooled cooling system than includes controls to simplify design, installation and operation while lowering implementation costs.  Subsidies are not needed unless the utility industry wants quick adoption. The subsidy helps overcome market barriers of unfamiliarity and experience. The TES industry is surviving with only a small percentage of cooling systems using storage today.  ASHRAE 90.1, LEED, and Demand Response revenue opportunities are causing TES applications to increase.


A large part of the Demand Response conversation, too

Commercial buildings use a large portion of the current generation capacity. One-third of the power grid load is consumed by commercial buildings.  Even as our economy has slowed, demand remains high and grid traffic can be congested, especially during high demand hours. Reducing demand as much as possible during peak consumption periods is the premise for demand response (DR) technology. Demand response is a voluntary change in electricity use by a participant at specific times of the day. Peak demand hours are most commonly between 12:00 am and 7:00 pm. Using demand response technology can reduce the stress on power grids, while providing benefits to the building, the power grid and the environment.

If most buildings, such as 1500 Walnut, were equipped with Demand Response technology like thermal energy storage, power consumption could be evenly distributed throughout all hours of the day, creating better load factors while reducing demand and the need for more investment in generation, transmission and distribution.  Reducing demand can also minimize the use of older peaking power plants.  These older peaking power plants create greenhouse gas emissions that are released into the atmosphere and result in poor local and regional air quality.


Thermal energy storage – let’s talk about it!

Thermal energy storage systems are reliable, affordable, and a viable solution to this country’s energy needs. It’s time to rethink energy storage and bring TES more fully into the energy storage conversation.


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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One Person has left comments on this post

» wd said: { May 24, 2013 - 10:05:27 }

Hmmmm. “Peak demand hours are most commonly between 12am and 7pm”. Now, why would that be? Maybe if we inquire as to the cause of those peaks we could open up other alternatives for reducing the peaks. If we could do that economically, maybe when we rethink energy storage we’d find we didn’t need as much as we first thought or maybe the design of it or the placement of it would be different. If we could eliminate the usage of electricity causing the peaks we would save $ in two ways: 1)we avoid the premium cost of supplying the old peaks and 2)we buy fewer kwh overall. And, fewer kwh overall sounds environmentally friendly.

Rethinking seems like a good idea.

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