Lynne Kiesling
This ars technica article on energy storage provides a concise summary of the challenge of energy storage and the current technology options. Focusing on the power needs of datacenters, the article describes the intermittency problem associated with renewable sources (in normal language, the sun doesn’t necessarily shine and the wind doesn’t necessarily blow at times that coordinate naturally with electricity demand).
Energy storage is the Holy Grail of the electricity system. Even if we did have dynamic pricing to enable decentralized coordination between supply and demand, it would be highly unlikely to match up perfectly all the time. Storage bridges that gap. Storage also changes the market power dynamic; if I have a storage option I can buy more when it’s cheaper and use it when it’s pricier. That alternative creates a substitute for generated on-demand peak power.
I agree that storage is the “Holy Grail” when it comes to successfully integrating intermittent generation sources into the electric grid, as capacity replacement rather than energy replacement. This is particularly true with wind, which tends to be more available during off-peak periods.
However, in designing the generation/storage system, it is crucial to remember that wind is not always 35% available, nor does it always have a 25% capacity factor. Both California and Texas have experienced periods of very low wind availability. California’s experience was long enough to have created serious issues, had wind been a larger percentage of total generation capacity, particularly if it was employed as capacity replacement.
One gigawatt of wind as “capacity replacement” at 90% reliability requires eight gigawatts of distributed wind generator capacity without storage; or, five gigawatts of wind generator capacity plus four gigawatts of storage capacity. That represents a significant difference between the investment in and cost of wind as energy replacement (“source of opportunity” power) and wind as capacity replacement (reliable power).
Also, hydroelectric generation consists of both reliable and “source of opportunity” components, as BPA demonstrated dramatically in both 1996 and 2000.
Ed wrote: This is particularly true with wind, which tends to be more available during off-peak periods.
Offshore east coast wind during a Bermuda high, a very prevalent high pressure scenario affecting the east coast during the summer, create southwestly thermals from Cape Hatteras northward beyond Cape Cod. The wind is pretty constant extending along the entire region. These days are generally the more hotter days of summer experienced on land in the big cities, which feel little more than a 5-10mph breeze. These winds shut-down after sunset, and pick up again soon after sunrise. With an advancing low frontal system, the wind has the potential to blow a gale all afternoon, and even last 24 hours @ the 15-25 kts range.
bookmark http://vortex.plymouth.edu/