Is Pumped Storsage Practical with Renewables?

Sometime ago, I undertook a limited review of energy storage technology. Since my choice of batteries as a viable energy storage technology to be used to in connection with wind projects has been challenged, I have decided to do another review of alternative storage technologies. Pump storage is by far the most viable alternative to batteries, since pump storage facilities have been built around the world. The primary objective of this study is to determine current pump storage costs. In order to do that I have looked at a number of pump storage facilities and tried to produce an estimate of costs if they were built today. For example the Northfield Mountain pump storage facility which is rated at 1080 MWe. It can produce electricity for 10 hours at a stretch. The Northfield Mountain facility was completed in 1972 at a cost of $685 Million.

In 2008 dollars the Northfield project would have cost about $3.7 billion, probably about 25% less than the cost of a nuclear plant with similar rated capacity. The nuclear plant at $5 Billion in 2008 would be a far better buy, for while the Northfield Mountain pump storage facility. The Northfield facility produces electricity for 1o hours a day, while the reactor could produce power for 24 hours a day over long streaches of time. The reactor produce power over 90% of the time, thus its power would be lower cost. But a head to head comparison of the pump storage facility and the reactor would not demonstrate true cost.

In order to produce electricity for the pump storage facility, a wind generating array would have to be built. The cost of that array would be paid for when electricity from the pump storage facility was sold. Pump storage operates at 75% efficiency. That is 25% of the energy input is lost before electrical output. Thus assuming a capacity factor of .40 for the wind array with a rated output of 1400 MWs operating 24 hours a day would be required to fill the pump storage facility. Lets assume costs at the low end of the 2008 range for windmills, say $2250 per KW. Thus the wind array required to fill the pump storage facility full would cost $3.150 billion. That would give us a figure of close to $7 Billion to be financed by the sale of peak electricity from the pumped storage facility. Seven billion dollars is a lot of money to spend for electricity that would be only available for 10 hours a day.

Pumped storage is a better match to wind generated electricity, than to solar generation systems. Solar power tends to be generated at periods of peak electrical demand. Thus pumped storage would only be desirable as a match to solar if solar power with storage were to be a candidate for base load electricity. It is clear that the economics of solar base with pumped storage would not be good. Solar in California produces about 20% of rated power. To produce base power for the rest of the day. a pump storage facility would have to be able to store twice the water that the Northfield facility holds or alternatively have a much higher head.

Matching pumped storage to wind would seem a much better deal. Wind costs less than solar per KW of rated capacity, and it is not impossible to find locations at which wind capacity would be double the natural limits of solar capacity. With wind it makes sense to use the pumped storage facility to produce peak electricity. Wind generated electricity is more likely generated in of peak night time hours, and thus sold at a relatively low price. Do the benefits of putting wind generated electricity to work pumping water uphill at night, and then using the water to power generators during peak day time electrical demand hours? Peak electricity can be sold at a higher price than of peak electricity, but the cost of storage has to be included in the cost benefits equation.

The California LEAPS project was conceived of as a matching of pumped storage with renewable electrical sources. In practice this might not have been the case. Although the LEASP project was described as having a 500 MW generating capacity, and providing 18 hours of storage. The LEAPS scheme proposed to used the existing Lake Elsinore as a lower reservoir, and to build an upper reservoir on a hill above the lake. The total project was estimated to cost $1.1 Billion. Serious objections have been raised to the project. First the input electricity would not come from existing renewable, but rather from fossil fuels power generators. Secondly, the inefficiency of pumped storage was over estimated by project backers. They estimated 13% energy loss in the pumping process, but failed to note that energy from pumping would be lost when water in the upper lake evaporated in the hot dry California air. Finally project economics did not work. The project promised to return only seventy five cents for every dollar it cost to build and operate. A plan to combine the pumped storage project with a money making power line would yield a project that might break even. Critics pointed to other defects in the project's design. The LEAPS upper reservoir is designed to contain 16 to 17 hours’ worth of water for hydroelectric generation under normal operations. But LEAPS cannot generate electricity for such a long period, while refilling itself with off-peak electricity. The LEAPS project also will draw on fossil fuel fired power plants, rather than renewables for electricity. Critics have calculated that when constraints are added to the output equation, the LEAPS facility was only capable of generating about 333 MW during peak electrical demand periods not the 500 MW capacity expected.

The LEAPS project then raises serious questions about the financial viability of pumped storage. It should be noted that many pumped storage facilities involve the construction of both upper and lower reservoirs. Because the LEAPS project involved the construction of only an upper reservoir, it would cost less than two reservoir projects like Northfield Mountain. Yet cost benefits studies have shown that the pumped storage part of LEAPS project will loose money.

In addition significant environmental issues have been raised about the LEAPS project which would be located in an environmentally sensitive national forest area, the Cleveland National Forest. Retired Cleveland National Forest supervisor, Anne S, Fege wrote in 2007, that the project would desecrate two pristine canyons, create a serious risk of fire in a fire prone national forest cause by high voltage transmission lines, would be built in an earthquake area, necessitating more expensive construction standards, would cause daily fluctuations to the water level of Lake Elsinor, and would decrease recreational opportunities available in the national forest. Advocates of pimped storage, although often flashing their "Green" credentials seldom pay attention to the environmental impact of the energy projects they support. Greens seem to believe that simply calling something green is enough to prove how pristine it is, without the need of further evaluation. Green who look no further than the word "Green" are no more friends of the environment than advocates of clear cutting are.

I must conclude then, that a substantial case can be made against the use of pumped storage as an electrical backup for renewables generation. The case against the use of pumped storage with solar is considerably stronger than the case against its use with wind, and the combination of wind and pumped storage appears to be more expensive than the cost of nuclear generating facilities. In addition, a wind pumped storage system, while more flexible than wind alone, would be neither as flexible nor as reliable as a nuclear generating system.

Thus the case that pumped storage would be an acceptable low cost alternative to batteries seems implausible at best.