April 2014 Issue (files are in PDF format)
Grid energy Storage (15 Mb DOE report) A December, 2013 report from the US Department of Energy provides an extensive review of that agency's opinions on the technology and economics of energy storage. Under the topic of "thermal storage" its only listing is for thermochemical energy storage systems, which it dismisses as being uneconomic. There is no mention of exergy storage or of sensible heat storage. Their near term target for the cost of storage is $250/kWh. At that valuation the cost of the Thomsen house installation should have been $10,000,000!!
Such reports need to be challenged. This DOE report paints a grossly misleading picture of the available energy storage options. Unfortunately such US government reports have a big influence on the policies of other countries (like Canada). If the DOE says that batteries should be used for grid energy storage and Sustainability-Journal says that exergy storage would do the same job at at price that is 1000 times cheaper then which choice is a politician likely to make?
Saucer shaped temperature profiles The performance of exergy stores depends to a considerable extent on a design feature under which the three rings of boreholes are all designed to operate with shallow saucer-shaped temperature profiles. By careful attention to the creation and maintenance of those profiles the systems can deliver stable, predictable outputs and achieve high heat delivery capacities.