Pumped Hydro: Part of the Solution to Our Energy Storage Needs

With all the talk about lithium ion batteries, and the unprecedented investment occurring in this area, it is easy to forget the most prevalent utility-scale energy storage technology, pumped hydro. Pumped hydro is the most mature and largest storage technology available. Worldwide, there are over 150 pumped hydro facilities with a total capacity of over 100 GW. In the United States, there are 38 pumped hydro facilities and a total capacity of approximately 19 GW. Battery deployments are just beginning and are typically measured in tens of megawatts rather than hundreds.

Pumped hydro is based on conventional hydroelectric technology. Facilities pump water from one reservoir into another at a higher elevation, typically using lower-priced off-peak electricity. When energy is required, the water in the higher elevation reservoir is released and runs through hydraulic turbines that generate electricity. One key advantage of this system is that the gravitational energy stored in the upper reservoir can be stored for long periods of time with virtually no energy loss. For pumped hydro to make economic sense, it must be constructed on a large scale, which involves a high initial facility construction cost and be able to leverage favorable geographic assets.

In 1985, a 2,100 MW pumped hydro facility in the United States cost $1.7 billion, or approximately $800 per kW. Today, a new pumped hydro facility costs approximately $1,500 per kW, give or take. Once built, the cost per kWh of storage is relatively economical, approximately $125 per kWh. While there are a myriad of citing and permitting issues, there are 40 pumped hydro facilities, totaling approximately 31 GW, planned in the United States alone. The question is: how much more growth will we see of this technology?

Pike Research believes it could reach upwards of 4.5 gigawatts per year, once the reality of large-scale renewables integration starts to happen in 2015 and beyond. This forecast may seem lofty, but really it comes down to building 20 – 40 facilities worldwide that average between 500 megawatts and 1 gigawatt. Is the forecast aggressive? Arguably yes. Is it feasible? Yes. Most close to the energy storage market acknowledge that a range of technologies are part of the solution. Only time will tell how much of the mix is comprised of pumped hydro, and perhaps more importantly when.

Article by David Link, appearing courtesy Matter Network.

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2 comments on “Pumped Hydro: Part of the Solution to Our Energy Storage Needs

Sherret E. Chase

David, You omit any concession to the unavoidable laws of thermodynamics in your incomplete simplification that “One key advantage of this system is that the gravitational energy stored in the upper reservoir can be stored for long periods of time with virtually no energy loss.”

In fact it takes about three units of electrical energy to pump the water to the upper basin in order to recover only two units of electrical energy later on when the upper reservoir is operated. There is no free lunch with energy conversion… you never win, you never get ahead, you always loose. Hydro pumped storage always depends on the inefficiencies of the original energy resource used to pump the water uphill and suffers again when the water is released. It can not be avoided that scarcely half the energy comes out at the end compared to the amount of energy that began the process. Hydro-pumped-storage has its place but it is not free, it is not a “source” of energy, and it requires at least twice the amount of original source energy to put into the system compared to how much can be extracted as electricity. The only financial incentive for H-P-S is when the electricity energy consumed to pump the water uphill is priced at less than half of the value of the electricity that is sold later on when the stored energy is later released.

Again H-P-S has its place in the energy mix and is a viable storage medium, but it comes at a high cost of efficiency and of the environmental considerations for its location.

Matthew Shapiro

Sherret: A couple of corrections for you. First, pumped storage is not 50% efficient, as your comment suggests. It is 80% efficient for most new projects. Second, its value is in far more than simply peak/off-peak differential. It has the ability to flexibly and quickly respond to changes in wind and solar output and help turn them into firm resources, and create significant savings on new transmission lines as well. It also can provide the full range of “ancillary services” that the grid needs. So when valuing pumped storage, you need to take a look at all of these potential benefits. And on the environmental impacts side, if you take a look at just about every one of the dozens of new pumped storage projects being proposed today, nearly all are “closed loop” projects that don’t involve natural waterways and are sited for far less impact than some of the mega-projects of the past or those in China.

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