Firming Things Up

One of the big issues with renewables is the need for firming – production is intermittent while needs are more or less on a curve matching the human activity curve. Solar is a good match for air conditioning and heating in areas that are cold and sunny, hydro at large scale is good for dispatchable generation and can also serve as a baseload source in the right situation. But wind is famously finicky. So this article on compressed air storage is pretty exciting.

Hydro systems are often paired with pumped storage, where reservoirs are filled when power is available and used for peak generation, now Hydrostor is combining air and water for storage. The combination of wind, water, and suitable heights for pumped storage aren’t all that common, but places that have wind, water, and places where underground chambers can be built are much more available. This sounds really promising

According to Spector, “The Terra solution is highly customizable and allows customers to pick the power-to-energy ratio. For systems of 200 megawatts or more, VanWalleghem said, Hydrostor can deliver 6 to 8 hours of duration on a turnkey installed basis of $150 per kilowatt-hour.”

So $30 million gets a peaker plant that can store night generated wind in Texas, where capacity is such that sometimes operators have to pay the grid to haul excess power away, and it can be turned into $0.20/kwh peak electricity. Recover cost in 3,000 hours, if there are a hundred days of six hour peak heat in summers, that’s five years, and lifetimes on utility scale systems are measured in decades.

A 200 megawatt plant will support a western city of a hundred thousand, but it would be a much bigger deal here – Capetown, South Africa, with a population roughly five times that size.



Wind is a big deal in South Africa, almost no capacity in 2012, two gigawatts now, and another three gigawatts coming. I’m not sure what fifty five million there need in terms of power, life is very different than California. Our 2kw/house metric is much higher than their requirements, perhaps by a factor of ten.

Hydrostor’s work thus far has been with fresh water. When they do their first saltwater system I’ll get really interested. If there is a deep cavern into which salt water enters, that means there is natural pressure – which can be used for osmotic desalination or maybe a graphene system. South Africa could really use more fresh water.

South African Climate

South African Climate


Hopefully we’ve managed to avoid War With North Korea, at least for this weekend, but I’m still thinking about Functional Triage. I like South Africa’s industrialization and their isolation from the problems in the northern hemisphere. They need to focus on renewable investments, but with the added calculus that things up north might go irreparably sideways, as we came so near to doing this weekend.



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