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Largest Sodium Sulfur Battery Powers a Texas Town
separsons writes "The largest sodium sulfur battery in America, nicknamed 'BOB,' can provide enough electricity to power all of Presidio, Texas. Until now, the small town relied on a single 60-year-old transmission line to connect it to the grid, so the community frequently experienced power outages. BOB, which stands for 'Big-Old Battery,' began charging earlier this week. The house-sized battery can deliver four megawatts of power for up to eight hours. Utilities are looking into similar batteries to store power from solar and wind so that renewables can come online before the country implements a smart grid system."
the battery would cost 25M, while a second transmission line would cost 60M. o_O
Yes, I'm left. You have a problem with that?
A watt is a unit of power not energy, that'd be 115 gigajoules (or 32 MWh if you're lazy)
It's amazing the game of telephone that happens when blogs steal news stories from blogs that steal news stories from blogs.
Inhabitat: "Electric Transmission Texas ponied up $25 million to build the battery, and will add $60 million to build a second transmission line by 2012."
PopSci: "Electric Transmission Texas helped put the battery project together for around $25 million. But the utility has also agreed to build a second 60-mile transmission line to Presidio for about $44 million by 2012."
NPR: "The other solution for this town would be to build a second line, and that line would cost somewhere in the range of $40 to $50 million. And so a battery project in the $25 million range looks pretty attractive."
They all agree the battery costs $25mill, 2/3 agree that the 2nd transmission line will be built in 2012, and none of them agree on the price of the 2nd line.
so it holds 32MW
No - it can hold 32MWh (=115.2GJ). Batteries hold energy not power. Since power is energy per unit time you have to multiply it by a time to get energy.
"The house-sized battery can hold four megawatts of power for up to eight hours."
"Power" is not "held." Power is delivered. Energy is held. The unit of energy is joule.
This story originally came from an NPR interview. Here is a link.
They can last about 2,500 complete cycles or 4,800 80% discharge cycles. (From the wikipedia article linked elsewhere). Presuming a power outage once a week requiring 80% discharge, it would last about 90 years, if the number of cycles is the only thing determining its longevity.
No, Sodium-sulphur batteries scale down horribly. They need to run hot enough for the sulphur to be molten*, and keeping large things hot is easier than keeping small things hot, as the thermal energy scale with the cube of the size, but the escaped heat scales with the square. I don't know how small they can get, though.
*According to wikipedia, they need to run even hotter, 300-350 degree celsius
It runs on molten sodium. Cool is the one thing you don't ever want the battery to get.
I found an online calculator and apparently the energy squares with either the diameter OR the speed. The only linear input is mass.
So let's try this: A 100-meter wide flywheel, weighing 10 metric tons, spinning at 1hz, gets you 68 kWh, or double that if you move the mass to the outside (which I presume you would for something that big). Now that's probably light for something so big, so at 100 metric tons you could get up to 1.36 MWh.
This battery has 32 MWh.
You would need to spin it 5 times faster (300rpm) to get that kind of energy. That's frighteningly fast for a ferris wheel. Also it would need some serious electromagnets and one hell of a support structure that's also frictionless.
No matter how you slice it, flywheels are all about linear momentum. They're either big or they're fast and it's hard to both.
As you can see, the estimates vary widely, there's a lot of guesswork involved in making these estimates. Overall the renewables don't fare that badly, especially wind and hydroelectricity.
In case you were wondering, here's the CO2 emissions:
So yes, even with all the intensive energy requirements for renewables, they still are better than fossil fuels. The problems with widespread use of renewables are political (i.e. Republicans and conservatives don't like them), require intensive upfront capital costs, and infrastructural (the power grid is not designed to carry power where likely wind generation sites are).
Gentlemen! You can't fight in here, this is the war room!
One word: IGBT
http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transistor
It's a lump of silicon about as big as a car battery, easily handles 5MW, and has revolutionised the connection of solar/wind/wave energy to grid.
Equipment costing hundreds OR thousands dollars now replaces what used to cost hundreds OF thousands, so connecting the battery to the grid is probably one of the easiest and cheapest problems to solve.