Monday, March 05, 2012

Very Interesting Article About Storing Off-Peak Electricity For Peak Demand Periods

The current issue of The Economist has a great page 15 story called Packing some power:
On paper at least, ERCOT ought to have had plenty of power. In 2010 it reported 84,400 megawatts (MW) of total generation capacity, well over last summer’s peak demand of 68,294MW. In theory, this is enough to produce some 740 billion kilowatt hours (kWh) of electricity a year—more than double the 319 billion kWh that ERCOT’s customers actually demanded during 2010. In electricity generation, however, aggregates and averages carry little weight. One problem is that wind energy accounted for 9,500MW of ERCOT’s total capacity, and the wind does not blow all the time. It tends to be strongest at night, when demand is low. Moreover, power firms are required by regulators to maintain a safety margin over total estimated demand—of 13.75%, in ERCOT’s case—in order to ensure reliable supply.

If only it were easier for ERCOT and other utilities to store excess energy, such as that produced by wind turbines at night, for later use at peak times. Such “time shifting” would compensate for the intermittent nature of wind and solar power, making them more attractive and easier to integrate into the grid. Energy storage also allows “peak shaving”. By tapping stored energy rather than firing up standby generators, utilities can save money by avoiding expensive spot-market purchases.
The article then goes on for 4 more columns, discussing very creative improvements in pumped-storage hydropower (pumping water to a higher reservoir at night, when power demand is low, and letting it flow down to generate power during the day, when it's needed); compressed-air energy storage; advanced rail energy storage; and pumped heat electricity storage, among others. Some have efficiencies in the 80% range, which isn't bad--it's certainly cheaper than having to buy electricity on the spot market to avoid rolling blackouts, and paying 30x the normal price for doing so!

I hope something good comes from at least one of these technologies.


allen (in Michigan) said...

The assumption being that an energy storage system results in lower end user costs then peaking capacity. Problem is, the most widely used, pumped storage, is dependent on certain necessary geological features and, oh by the way, how are the greenie-weenies going to react to scooping out the top of a mountain to make a lake?

Most of the rest of them have fairly self-evident problems.

That rail system would be limited to areas where the requisite topography was available and I'm just wondering how much power a system like that could store?

The Gravity Power system has, I think, a similar issue in that the cost of the storage well, the big one, will become astronomical before it can store much power.

They sound good but in practice they're costs are high enough have prevented widespread deployment.

Anonymous said...

"Problem is, the most widely used, pumped storage, is dependent on certain necessary geological features..."

Fortunately, we know how to move electricity long distances. Not without loss, but we don't need these geological features to be near the power generation.

"They sound good but in practice they're costs are high enough have prevented widespread deployment."

Sure, but it is nice to be exploring new approaches on the off chance that traditional power generation gets more expensive.

-Mark Roulo

allen (in Michigan) said...

No cherry-picking Mark. The claimed advantages for energy storage have been the technology's advantages for a long time. There really isn't anything new in any of these approaches that yields notable savings and there isn't anything new in any of these approaches.

Energy storage results in more expensive electricity since the difference between peak and off-peak generating costs don't make up for the costs of storage.

Even the cost of energy transmission only make sense when the source of the power, say a water fall, is distant from the customer, like New York City.

It's clearly more economically advantageous to build generating capacity but that view runs up against the widely-touted imminence of energy penury due to the approach of Peak Oil and the dangers of anthropogenic global warming, both of which are crap. If we're not smart enough to cut our energy usage due to the end of petroleum and global warming then we'll just have to have that option taken out of our irresponsible hands by the self-appointed intellectual titans who are fully aware of those approaching dangers.

But like I wrote above, it's a bunch of crap. We're not running out of petroleum and climate science is too immature to provide worthwhile predictions. Without those two catastrophes the case for the supposed advantages of energy storage schemes falls apart and the reasons to go with the cheapest source of power predominates.