Megawatt Storage Farms

Even if California “only” ends up with 25% renewable electricity within the next decade or two, there is going to be a staggering amount of investment pouring into wind and solar power, and with intermittant sources of energy, massive storage infrastructure is just as necessary as the generating infrastructure. In our analysis of Prop. 7, California’s Proposition 7, the initiative that calls for 50% renewable energy by 2025, we estimated compliance would require about 500 gigawatt-hours of renewable electricity generating capacity per day. For wind power, based on installation costs of $2.5 million per megawatt ($2.5 billion per gigawatt), and yields of 17.5%, this would require a total investment of nearly $300 billion. The estimated total cost for solar, at today’s prices, was considerably higher than this (bear in mind the cost for solar energy is going to drop faster and further than the cost for wind energy in the coming years). But what about the cost for storage infrastructure?

California’s wind-rich areas

In a perfect world, parked electric cars will harvest intermittant energy – wind at night, solar during mid-day, and release that energy during the demand peak.

In a perfect world, 2nd and 3rd generation smart metering systems at homes will allow everyone’s car to act as a micro utility, an automated fiduciary, purchasing power when the spot price is low and selling power when the spot price is high.

In a perfect world, cars that store 10-50 kilowatt-hours of electricity will buffer intermittant sources, and storage infrastructure requirements will be reduced. Will electric cars proliferate as fast as intermittant generators? Will they always be parked and collecting power at the right times? Apart from electric cars performing this function, how much storage capacity are we going to need?

In California the demand peak is around 50 gigawatts, and the off-peak minimum can get as low as 20 gigawatts. The time of peak demand is between 5 p.m. and 10 p.m., when appliances are operating along with flat screen TVs and PCs. During this period, when the sun is down and the wind yields aren’t yet at maximum output, at least 25% of California’s daily electricity draw is consumed, about 250 gigawatt-hours. It is reasonable to assume most of the renewable energy used to fulfill this demand will have to come from stored wind, and stored solar. So what would it cost to store 100 gigawatt-hours of energy?

The sodium-sulphur battery

Yesterday we had the opportunity to speak briefly with David MacMillan, CEO of Megawatt Storage Farms, Inc., a company that is developing large scale electricity storage using NAS (sodium-sulphur) batteries. He claims that “not including site acquisition and preparation,” storage technology using NAS batteries would come to about $350,000 per megawatt-hour. This means the cost to load balance California’s grid, should 50% of her energy come from solar or wind sources, would probably run about $35 billion dollars. This figure doesn’t include transmission upgrades, nor does it include site acquisition and preparation, but it also doesn’t take into account the potential of electric vehicles (or other private decentralized storage solutions) to absorb some of the required storage capacity. Objections to renewable energy in general, and proposition 7 in particular, probably cannot rest on the storage and load balancing challenges, insofar as they only represent about 10% of the required investment.

For more information about utility scale electricity storage technologies, reference our posts Utility Electricity Storage, General Compression, Solar Thermal Storage, and Gridpoint’s Storage+, to name a few. For more information about sodium sulphur batteries, visit the technical specifications page for NAS Batteries on the website of NGK Insulators, Ltd., a major manufacturer of these batteries. For more information on how these batteries work, and where they are being deployed, read About Sodium-Sulfur (NaS) Batteries, on the excellent Fraser Domain Energy Blog (where have you gone?), or the USA Today report < href=""a title="New battery packs powerful punch">New battery packs powerful punch.

8 Responses to “Megawatt Storage Farms”
  1. Tom Konrad says:

    Why no mention of Vanadium Redox Batteries? They scale up better than NaS because they’re flow batteries.

  2. Kelly Rivas says:

    In a perfect world, we as citizens wouldn’t have to challenge and force our energy providers to produce sustainable electricity. We’re not a perfect world. Our energy providers produce electricity for profit, not for us. We want clean sustainable energy NOW. They want more of our money, FOREVER. I say we pass prop. 7 and force the necessary shift in business to provide sustainable consumer options. Climate change isn’t waiting for us to take action and we certainly aren’t invited to take action in much decision making. Prop. 7 provides the invite and ability. Let’s do this now. This is the most urgent issue facing us which all other issues stem from.

  3. Kevin Cullen says:

    For storage of wind generated power applications, there is an important distinction between the VRB’s vanadium based flow batteries and NaS’s sodium sulfur batteries.

    The key difference lies within the battery’s respective ability to accurately determine its state of charge.

    A “gusty” wind environment is characterized by its constant charge/discharge/charge/discharge cycles — often many hundreds of times per day.

    Sodium sulfur battery technology is not able to accurately determine its state of charge which leads to this battery type being potentially overcharged, which is damaging to the membranes in the cells.

    The vanadium based technology, on the other hand, can easily measure this state of charge so no danger of overcharging exists.

    The bottom line, given the gusting nature of what blows, is that wind is just not part of NaS’s game.

  4. Chris says:

    Interesting that there is no mention of using reservoirs to save energy for times of peak demand. North of NYC there are basically two giant lakes. The first is on the top of a mountain and the other is at the base of the mountain. At night, when electricity is cheap, they pump water to the top. During times of peak demand, they let the water flow back down past turbines that generate electricity.

    The facility that I visited was fairly old and was still capable of greater than 80% efficiency. I would like to think that number would be higher today and also offers a large scale alternative to meet peak demand. That one system that I just mentioned was capable of generating as much electricity as a large nuclear power plant when necessary.


  5. John Galt says:

    There was a pumped storage system at Tam Sauk mountain (the highest point in Missouri). The dam broke a few years ago, creating quite a disaster.

  6. Obviously there will be a continuing technological advancement to be factored in somewhere too. NaS batteries are only one side of the story as a couple of commenters have already mentioned.

  1. [...] a recent editorial, presents some staggering figures for the cost of California’s Proposition 7 (Prop.7) which, [...]

  2. [...] like wind and solar, less predictable than mainstream sources, load balancing becomes trickier. According to EcoWorld: In California the demand peak is around 50 gigawatts, and the off-peak minimum can get as low as [...]

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