According to a press release issued by MHI, there will be a total of three cargo containers involved in the project: two of the containers will house roughly 2,000 units of lithium-ion batteries each, and a third will house the power conditioning system responsible for converting direct current (DC) to alternating current (AC).
The storage system is set to be installed at the Kirkwall Power Station in the UK’s Orkney Islands. Power will be transmitted to and from the mainland via a submarine cable anytime there’s a shortage or surplus of power. In theory, the storage system will store surplus power in the lithium-ion batteries whenever the supply exceeds demand, offering an increased level of reliability for later power delivery.
The issue of energy storage gets to the heart of one of the greatest perceived weaknesses of renewable energy technology: what happens when the wind’s not blowing, when the tide’s not turning, and when the sun’s not shining? According to Michael Goggin, Manager of Transmission Policy with the American Wind Energy Association (AWEA), energy storage systems like that being developed by MHI and the SSE may work well in certain situations, but in others it may actually be less cost-effective than alternative methods.
“On the mainland integrated power system, there are many existing sources of flexibility, so new energy storage resources are not needed to accommodate the very small amount of variability and uncertainty,” Goggin said. “Storage is one option for increasing the flexibility of a power system, and using it makes sense when it is cost-effective. However, other options, particularly making greater use of existing resources or building more transmission, are typically more cost-effective on large integrated power systems.”
According to the AWEA’s “Wind Power and Energy Storage” factsheet, flexibilities built into the existing power system enable operators to increase and decrease the output of generators. This makes it possible to easily and more cost-effectively accommodate for certain variabilities.
Goggin went on to say that he believes island power systems can benefit far better from energy storage systems. “They have no ties to the outside world and often have weak transmission systems and inflexible power plants,” he said, “so there tend to be more cases where storage can be economic.”
The joint MHI/SSE storage system is set to go online in early 2013.