Open thread: energy storage

2014-06-23

in Economics, Geek stuff, Politics, Science, The environment

One challenge with energy sources like solar and wind is that their output varies with local environmental conditions, and not necessarily in ways that correspond to energy demand.

Hence, having energy storage capacity makes them easier to integrate into the grid. There are many options: pumped hydroelectric storage, tidal storage, batteries, compressed air, molten salt, and potentially hydrogen.

It is also possible to balance output from different kinds of renewable stations, using biomass, solar, wind, tidal, and other forms of energy to cover one another’s fallow periods.

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{ 5 comments… read them below or add one }

. June 23, 2014 at 3:57 pm

Pumping heat

A reversible heat-pump promises a cheap way to store renewable energy on the grid

At the moment, grid managers match demand by generating just enough electricity at any given time. But power from renewable sources, particularly the wind and the sun, is intermittent. Nevertheless, as costs come down and efficiency increases, renewable energy is being used more widely. Solar power is already the cheapest form of electricity in most sunny climes, and in America the Department of Energy wants it to provide 27% of the country’s electricity by 2050, up from less than 1% today. But without efficient grid-scale storage, costly backup generation will be needed to keep the lights on. In many poor countries that means running a smoky diesel generator.

A number of technologies are being developed to store energy on the grid, such as flow batteries which can accumulate energy in liquids and discharge rapidly. Giant flywheels and supercapacitors are also being explored. But Mr Howes thinks his invention can beat them all.

His system is based on a heat pump—a device like an air-conditioner that transfers heat from one place to another. In his case, though, the device is reversible, and when the heat flows back it works like a heat engine, converting thermal energy to mechanical power like a car engine.

. June 23, 2014 at 3:58 pm
. July 26, 2014 at 11:32 am

And energy-densities in supercapacitors are improving rapidly, according to Franco Gonzalez, one of the authors of a newly published report from IDTechEx, a market-research firm in Cambridge, Britain. A new device, the hybrid supercapacitor, has recently reached 30-40% of a lithium-ion battery’s energy-density, and the use of electrode materials that have an even bigger ratio of surface area to volume than existing materials (carbon nanotubes and graphene, for example) is likely to increase energy-densities still further in the near future. On top of all this, new types of electrolyte (the liquid between the electrodes) will allow both higher energy- and power-densities. These ionic liquids, as they are known, have the further advantages of being neither toxic nor inflammable—which is not always true of what they are replacing.

Supercapacitors also last longer than batteries. Repeated cycles of charging and discharging degrade a battery’s chemical components. This means that after a few thousand such cycles most lithium-ion batteries are giving up the ghost. According to Mr Gonzalez, supercapacitors can keep going for 1m cycles. Lithium-ion batteries are improving too, of course—but not as fast. IDTechEx therefore expects supercapacitor sales, currently worth less than 3% of those of lithium-ion batteries, to grow to over 10% in the next decade, creating a $6 billion market.

. August 8, 2016 at 5:12 pm

Sisyphus’s train set
A novel idea for storing electricity

The prototype proved the principle, and now the company has bigger plans. In March it received approval from America’s Bureau of Land Management to lease land to build a track near Pahrump, Nevada. This would run larger trains than those at Tehachapi, and these would carry their rocks in concrete boxes, rather than loose. Once at the top of the track, the boxes would be raised by jacks built into the wagons carrying them, rotated and then lowered back down onto supports on either side of the track, so that they straddled the track above the height of a train, like bridges. Freed of their burdens, the trains would then run back downhill to fetch more loads. When the time came to generate power, the process would be reversed.

The hill ARES has chosen has a gradient of about 8%. The track itself is just under 9km (about 5½ miles) long. The company estimates that its proposed system will be able to store 12.5 MWh of energy, and deliver it back to the grid at a rate of up to 50MW. That is still small compared with pumped storage (the Dinorwig facility in Britain, for example, has a capacity of 10.8GWh and a maximum output of 1.8GW), but ARES’s engineers think it is enough to make commercial sense, at least in principle. And if principle turns to practice, it can be enlarged.

. December 22, 2016 at 8:02 pm

The one-year-old project is in Toronto, Canada—or, rather, just offshore, at the bottom of Lake Ontario. It was designed and built by Hydrostor, a company founded by Cameron Lewis, who developed the technology after working in the oil industry. The plant is operated by Toronto Hydro, a local power utility.

In this case the working fluid is air rather than water. The air is compressed on land and pumped through 2.5km of pipes to a station on the lake bed 55 metres below the surface, a head of water that generates a pressure five atmospheres above normal atmospheric pressure. Here, the air is stored in six spherical bags, known as accumulators, made of a proprietary material. Each accumulator has a capacity of 100 cubic metres.

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