Is the electricity from wind farms, nuclear plants, hydroelectric plants, etc. ever stored up in some fashion? Are there giant batteries where this energy is stored, to be used as needed? Or does it directly enter the grid and make its way to people’s homes without being stored in some fashion along the way?
This. Batteries to store the amount of energy produced by wind farms are cost prohibitive.
The price paid to the wind farm varies throughout the time of day depending upon demand from the grid.
Most of it is not stored. The “grid” does not contain any large battery banks anywhere.
In some areas, electricity is used to pump large amounts of water up into a higher level reservoir. Later, when the electricity is needed, the water is released and flows through hydroelectric generators. There are some losses due to evaporation and the mechanical conversion losses, etc. but it’s a heck of a lot cheaper to use gravity and the potential energy of water at a higher elevation than to use batteries.
On a smaller scale, folks sometimes store energy as heat for use later.
Large-scale energy storage is one of the great technological challenges of our time. Batteries just aren’t that good. One method is stored hydro power as mentioned above, but that’s limited by geography. Another method is to use electricity to extract hydrogen from water, then burn the hydrogen later. Nobody’s doing that on a large scale, though. The vast majority of generated electricity has to be used immediately.
Last story I read was about converting excess energy to hot water and using the hot water to create power when needed.
[News story in the last couple of weeks or so. Being tested in the California desert somewhere.]
How timely. This recent article published by The Verge discusses.
Why Tesla’s battery for your home should terrify utilities by Josh Dzieza, Feb. 13, 2015.
TL;DR: Tesla and its sister company SolarCity are working on developing efficient and cost-effective storage batteries for exactly this purpose. If these are successful and widely adopted, it will essentially be the end of power and utility companies as we now know them. They will have to develop completely new business models to function in a Brave New World where roof-top solar panels are commonplace. The utility companies will have to become service-providers in the business of buying all the excess power that everybody develops when the sun shines, and storing it (the thing that specifically isn’t done much now), and then re-distributing it when and where it is needed.
I’ve also read about solar based systems that store the energy in molten salt and highly thermal insulated tanks. When they need to recover the energy, the heat from the molten salt is used to flash water into steam, which then powers a traditional steam turbine generator.
Most of these heat storage type systems are experimental or aren’t being used on a very large scale yet.
Thread on the topic. Anybody using rechargeable batteries is storing electricity at home.
Excess electricity can be stored in reservoirs. Basically the excess electricity is used to pump water uphill. That water is then released on demand to recreate the electricity via turbines.
It’s an unusual situation to be sure, but it’ll become more common as more alternative energy sources come online.
A new alternative to pumped hydro is using trains and large masses carried up a mountain. Electric trains carry the masses uphill to store energy, and then run as generators going downhill. Not clear yet how practical it is, but it certainly avoids the main problem with pumped hydro, which is that there are very few locations where it’s suitable (need a mountain of a particular shape and lots of water available).
Flywheel storage has been tried, too.
What technology is best depends on how long you need to store it. At the shortest time scales, there’s some storage in the rotational kinetic energy of the turbine that drives the generator. Then there are large inductors or capacitors at some power power plants that help even out fluctuations on the range of seconds to minutes. Some places are experimenting with flywheels for this purpose, too.
Another thing is that you can achieve effective storage through varying use.
For instance, one aluminum smelting plant can adjust their smelter power consumption by +/- 25%. By doing so they can buy more power when it’s cheap and less when it’s expensive.
This doesn’t really seem like storage since they never actually resell electricity back to the grid (the article implies that they do, but I believe this is incorrect). But it behaves exactly like a fixed-load smelter combined with a battery that handles some fraction of the total load. The energy is stored in hot aluminum. It doesn’t have to be converted back to electricity since the smelter was going to heat the aluminum anyway, sooner or later. Therefore it’s an efficient process.
There are limits to this type of technique, but it will reduce the need for actual storage (battery, flywheel, etc.).
Four megawatts for 8 hours! :eek:
Ok, I’m impressed.
I hadn’t seen that before. Thanks.
All the rotating electrical machinery connected to the grid stores energy short term by this flywheel mechanism. Heck, you can improve your home’s ability to start motors by having other motors already rotating. People who connect three phase motors to single phase power to create a rotary phase converter know that the more you have rotating now, the bigger a motor you can suddenly add.
This same effect is used by utilities during service restoration when bringing additional load and generators online. After a blackout starting the first increment in the most challenging. Once they get something up & running, each incremental addition of load & source gets easier.
If your on the grid you energy provider might not allow it, mine certainly doesn’t.
Don’t allow what? We’re talking about rechargeable batteries, the utility companies have no say in the matter. If you want to put the stored energy back on the grid they’ll try to stop that but you can store and use all the energy you want.
About 15 years ago, I heard about some company converting excess energy into compressed air (in a cave or cavern) and then using the compressed air as an energy source during high demand periods.
googling…
Of course Wiki has an article on it.
(Rumor has it that the New England Patriots have done some compressed air experiments in footballs)
Don’t the generating plants vary their output to meet the demand? In other words, if they only need 1 mw in the middle of the night, they only spin the turbines at one rate,
I mean, there aren’t huge banks of resistors at the powerplants just converting excess power into heat, or anything absurd like that, right?
For example, if the Fayette power plant SE of Austin sees a demand of 900 MW, wouldn’t they only feed coal / meter pressure /spin the turbines only fast enough to generate 900 MW across their 3 units? They don’t run all 3 units at 615/615/460 MW full power all the time and just blow away the remaining 790 MW as heat somehow?