Four of the proposed projects would be located in Carbon County, within easy range of several huge new transmission projects intended to ship Wyoming's lower-priced wind energy to Southwestern markets, including California. These include the Zephyr line, the TransWest Express, and the Overland transmission project. Rocky Mountain Power's Gateway West is another major new line that would move wind energy westward.
The fifth proposed pumped storage project is in Converse County, near the planned origination point of the High Plains Express, which is intended to help deliver renewable energy through Wyoming, Colorado, and New Mexico to Arizona.
The pumped storage projects range in size from 300 to 500 MW; the combined capacity of the projects, if all were developed, would be 1,900 megawatts. Energy storage potential would be more than 50 gigawatt-hours - equivalent to what 3,000 megawatts of wind turbines would put out for 17 hours at their maximum. Gridflex CEO Matthew Shapiro notes, however, that "not all projects would need to be developed in order to have a significant impact."
Gridflex suggests a number of benefits from the use of storage in Wyoming, including creating firm capacity out of variable wind energy, savings on transmission line capacity, and ancillary support services to the grid. Says Shapiro, "We are talking about being able to deliver a firm product-with a capacity factor in the intermediate-to-baseload range-with only an incremental amount of storage capacity versus wind capacity." On transmission savings, Shapiro notes:"The pumping capacity of just one of these projects could shift the top four hundred megawatts of wind output to lower wind periods, making significantly more efficient use of room on the new transmission lines."
Shapiro adds that "the most elegant approach would be to coordinate the operation of the storage projects, where, for example, one serves in the peak-shaving role to improve transmission utilization, while the others do the work of shaping and firming the resource for final delivery."
According to Shapiro, pumped storage represents an affordable incremental cost. "We are looking at firm wind power at $95 to $110 per MWh, while solar thermal-the next available firm renewable source-is upwards of $130." Shapiro believes that the wind-storage combination could even compete against combined cycle gas generation "if natural gas prices rise in the long term, and if environmental factors are taken into account."
The currently planned strategy for some Wyoming developers is to "firm" wind through the use of gas-fired combustion turbines. Shapiro argues that storage is a superior option, offering the following reasons:
The pumped storage projects will be able to peak-shave, while gas cannot do this.
Pumped storage would firm wind with wind, rather than with a fossil fuel. Pumped storage can respond much faster to fluctuations in the grid than even the next generation of "fast response" gas-fired combustion turbines. Another advantage for storage, says Shapiro, lies within the intended market: "California may well be interested in buying Wyoming wind, but they may not want to buy gas-fired generation that piggy-backs on that wind."
The storage projects could also benefit conventional generation in Wyoming by allowing it to operate at more efficient levels, which can reduce emissions and save on fuel cost. Shapiro says that Gridflex is pursuing partnerships with a number of wind and transmission developers. Gridflex Energy is currently pursuing more than 5,000 megawatts of large-scale energy storage projects across the United States. Most involve pumped storage hydro, while several involve Compressed Air Energy Storage, or "CAES."
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