Coyote Blog

I had to laugh at the stories the other day on the battery backup system Elon Musk and Tesla made for the Australian Power grid:

Tesla has completed its 100 megawatt Powerpack battery backup system in South Australia within 100 days (easily), as Elon Musk had promised. That means the company essentially won the "bet," and won't be on the hook for the entire cost of the project, estimated at $50 million. More importantly, it means that some 30,000 homes in South Australia will have a power backup in case there's no breeze at the Hornsdale Wind Farm located about two hours from Adelaide.

A megawatt is a measure of energy production or transmission rate.  As such, it is a perfectly appropriate way to size the capacity of a power plant that is assumed to have a continuous supply of fuel.  However, it is an extremely odd way to size a battery.  A battery has a fixed energy storage capacity, which is generally measured in watt-hours (or some conversion thereof). For example a 10 Wh battery would provide 10 watts for an hour before running out, or 5 watts for 2 hours, etc.  It is not clear if this is just a typo, that they really mean 100MWh, or if 100 megawatts is the peak discharge rate and they are being silent on exactly how long this lasts (ie how long can those 30,000 homes be powered?)  I checked the first 10 sources in a Google search and not a single media outlet that routinely chastises climate skeptics for being anti-science seems to have questioned the oddball and nearly meaningless 100MW figure.

I was going to compare the number on energy storage here and show that you could actually generate electricity from gas, not just store it, for well less than this.  But it is sort of hard to make the calculation when they don't get the units right.

By the way, if this is required to make wind power work, will we start seeing wind advocates building in $50 million batteries when they present their economics?  Any bets?