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Tdworld 7073 Pumped Storage Words Stefano Senise Hemera

P.S. (Pumped Storage), I Love You

Feb. 27, 2017
Now with utilities closing down fossil and nuclear facilities, the time is right to invest in this technology.

Some technologies just seem to make sense. But everything has to line up correctly for a technology to move forward.

When I was in Switzerland five or six years ago, the Swiss were considering putting in pumped storage so that low-cost wind from the north and low-cost solar from the south could be stored and then delivered to the rest of the continent at peak times. In 2016, the 1000-MW Linthal pumped storage hydro power plant was successfully synchronized to the Swiss grid bringing this vision to pass.

Pumped storage is not new. When I was at Georgia Power, the company put the Wallace Dam Project into operation in 1979 with a maximum generating capacity of 312 MW. Water generation at Wallace comes from the generating station at Lake Oconee with Lake Sinclair serving as the lower reservoir. One of the best projects I was assigned to when working at the Georgia Power Research Center (now NEETRAC) was to provide line temperature data back to the control center. Ray Allen, the engineering manager at the control center, wanted to use this information to coax extra capacity from the pumped storage facility when conditions were right. We really wanted to know the line temperature as that can be directly related to line sag, which is the condition that limited the output from the dam.

I came up with the idea to cut a groove in the fiberglass rod of an Ohio Brass insulator, then install a fiber-optic temperature sensor through the groove in the insulator rod, slip on the polymer skirts and attach the insulator to the overhead conductor. We tested the set up in the lab and hung the instrumented insulator on the line. Voila! We were in the dynamic line rating business. When weather conditions (ambient temperature and wind speed) allowed, we could extract more capacity from the generating station.

At the same time, the utility to the north, Tennessee Valley Authority, was also building its Raccoon Mountain pumped storage facility, which was unique in that TVA built a reservoir by digging out the top of the mountain. The lake holds 107 billion gallons of water covering 528 acres of water surface. It has four generating units with an output on the order of 1600 MW. I had a chance to tour the facility and can recall seeing some of the first Core 10 steel poles being used for the transmission lines exiting the plant. This plant was first connected to the grid in 1978 and, with the exception of a few years’ loss of output from cracked rotors, has been quite reliable.

It seems like the heyday of pumped storage in the United States was in the 1960s, 1970s and early 1980s. But now with utilities closing down fossil and nuclear facilities, the time is right to invest in this technology.

I decided to take a look around and see how much pumped storage actually has been installed. Over the years, the Federal Energy Regulatory Commission (FERC) has authorized a total of 24 pumped storage projects that are constructed and now in operation, with a total installed capacity of approximately 16,500 MW; most of these projects were authorized more than 30 years ago.

FERC has seen a recent increase in the number of permit and license applications for pumped storage projects. In 2014, the commission issued licenses for two proposed pumped storage projects. And more recently, FERC has issued the Gordon Butte Pumped Storage Hydro Project, located in Montana, a 50-year license. It is expected that the final design will be completed in 2017 with construction starting in 2018. Absaroka Energy is developing this 400-MW pumped storage project. And the American Public Power Association just contacted me with news that the San Diego County Water Authority and the city of San Diego are considering building pumped storage capacity into an existing reservoir. The potential project would create a new source of renewable energy (up to 500 MW) that increases grid stability to the region while having additional capacity to deliver to customers during peak demand. They could also deliver electric power on days when other renewable energy supplies are scarce.

How does pumped storage compare to other forms of grid-connected storage? The International Energy Agency reports that from 2005 to 2014, global deployment of large-scale batteries rose from 120 MW to 690 MW, while thermal energy storage capacity surged from 250 MW to 2420 MW. But total grid-connected energy in 2014 was 145 GW, with 97% of that capacity in the form of pumped hydroelectric storage.

Of course, there are social and financial barriers for pumped storage, just as there are for all other forms of storage, or for all forms of energy for that matter. But in an era where we are losing our firm sources of coal and nuclear generation, it is key that we have access to bulk storage so that we can make better use of intermittent wind and solar energy.

In the energy world, love is conditional. Pumped storage, I love and need you more than ever.

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