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http://www.ieee-pes.org/images/pdf/open-access-milligan.pdfDoes Wind Need Storage?
The fact that “the wind doesn’t always blow” is often used to suggest the need for dedicated energy storage to handle fluctuations in the generation of wind power. Such viewpoints, however, ignore the realities of both grid operation and the performance of a large, spatially diverse wind-generation resource. Historically, all other variation (for example, that due to system loads, generation-commitment and dispatch changes, and network topology changes) has been handled systemically. This is because the diversity of need leads to much lower costs when variability is aggregated before being balanced.
Storage is almost never “coupled” with any single energy source—it is most economic when operated to maximize the economic benefit to an entire system. Storage is nearly always beneficial to the grid, but this benefit must be weighed against its cost. With more than 26 GW of wind power currently operating in the United States and more than 65 GW of wind energy operating in Europe (as of the date of this writing), no additional storage has been added to the systems to balance wind. Storage has value in a system without wind, which is the reason why about 20 GW of pumped hydro storage was built in the United States and 100 GW was built worldwide, decades before wind and solar energy were considered as viable electricity generation technologies. Additional wind could increase the value of energy storage in the grid as a whole, but storage would continue to provide its services to the grid—storing energy from a mix of sources and responding to variations in the net demand, not just wind.
As an example, consider Figure 7 below, which is based on a simplified example of a dispatch model that approximates the western United States. All numerical values are illustrative only, and the storage analysis is based on a hypothetical storage facility that is limited to 10% of the peak load and 168 hours of energy. The ability of the system to integrate large penetrations of wind depends heavily on the mix of other generation resources. Storage is an example of a flexible resource, and storage has economic value to the system even without any wind energy. As wind is added to the system in increasing amounts, the value of storage will increase. With no wind, storage has a value of more than US$1,000/kW, indicating that a storage device that costs less would provide economic value to the system. As wind penetration increases, so does the value of storage, eventually reaching approximately US$1,600/kW. In this example system, the generation mix is similar to what is found today in many parts of the United States. In such a system with high wind penetration, the value of storage is somewhat greater because the economic dispatch will result in putting low-variable-cost units (e.g., coal or nuclear) on the margin (and setting the market-clearing price) much more often than it would have without the wind. More frequent periods with lower prices offers a bigger price spread and more opportunities for arbitrage, increasing the value of storage.
In a system with less base load and more flexible generation, the value of storage is relatively insensitive to the wind penetration. Figure 8 shows that storage still has value with no wind on the system, but there is a very slight increase in the value of storage even at a wind-penetration rate of 40% (energy). An across-the-board decrease in market prices reduces the incentives for a unit with high fi xed costs and low variable costs (e.g., coal or nuclear) to be built in the first place. This means that in a high-wind future, fewer low-variable-cost units will be built. This reduces the amount of time that low-variable-cost units are on the margin and also reduces the value of storage relative to the “near-term” value with the same amount of wind.
The question of whether wind needs storage ultimately comes down to economic costs and benefits. ...
You can download the full document FOR FREE by clicking the pdf link below and you'll be able to see figure 7.
Wind Power Myths Debunked
november/december 2009 IEEE power & energy magazine
Digital Object Identifier 10.1109/MPE.2009.934268
1540-7977/09/$26.00©2009 IEEE
By Michael Milligan, Kevin Porter, Edgar DeMeo, Paul Denholm, Hannele Holttinen, Brendan Kirby, Nicholas Miller, Andrew Mills, Mark O’Malley, Matthew Schuerger, and Lennart Soder
http://www.ieee-pes.org/images/pdf/open-access-milligan.pdf
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