Energy is conserved. What is put onto the grid is used. Part of varying load leads to voltage variations. However, as long as there is capacity to do it, the electric companies vary what is put out to hold a narrow voltage range. Changing the strength of the field, or turning it on and off, varies the output of a generator. Older automotive voltage regulators turned the field on and off rapidly. I am not sure how the newer ones work.
I can’t verify that 2% storage figure, but it sounds reasonable to me. Mostly we cope with varying loads with varying output. The pumped storage only adds to available capacity. It stores energy, not electricity. I have seen speculation about connecting electric car batteries to the grid to store electricity. The flaw I see there is that the afternoon peak usage may not come long enough before the evening commute to recharge all the batteries.
When my power fails, I drag out a 6250 watt generator and start it up and plug the house into it*. Its controls hold the voltage close to 116 volts no matter how little or how much power we draw as long as we are careful to stay below the maximum. When the refrigerator or other large load kicks on or off, we can hear the generator motor respond.
*Yes, we do have an approved interlock to avoid an illegal backfeeding to the grid.
Eh, it amounts to the same thing. Neglecting inefficiencies, there’s no difference between a hydroelectric plant that’s running water out of the reservoir to run the generators and simultaneously pumping water up to store energy, and one that’s just sitting idle and letting the water stay where it is.
We’re back to the issue that no one in the industry would call “not running the generators” storage. Storage allows the electric system to serve a higher load at a later time than the generation available at that time would otherwise allow. Conservation reduces load without increasing the ability to serve future load.
No one can stop you from creating your definitions. You can call anything energy storage. You can call driving to the multiplex rather than using your television to watch Toy Story 3 storage of electricity. The obstacle you run into is getting other people to accept your idiosyncratic definitions. Your scenario is not a definition used by anyone, even beside the obvious point that running the generators to produce electricity and pumping for later use is never done simultaneously. (I’m pretty sure you lose some energy in the process as well, but you’re the physicist.) We need a technical definition so that we all can agree what we’re talking about. Yours doesn’t quality.
To get back to the fundamental question of the OP, yes, cutting back on electrical usage does do some good. Even if a power plant continues to operate, when you reduce the electrical load on the plant, the plant consumes less fuel.
Not at the same plant, of course (that would be pointless), but you could have one power plant running and powering a pump at another plant. And yes, you would lose energy, which is why I said “neglecting inefficiencies”.
To each generator a large grid looks like a load that can absorb all the power the generator produces without significant change in voltage or frequency. If the generator is diesel driven (just as an example) then feeding more fuel to engine increases the torque, and the power out of the generator increases, but there is no increase in rpm. (other than momentary, as the phasing between the generator and the grid shifts, power angle it is called)
Increased load lowers the voltage and frequency on the whole grid. This is sensed, and more generating capacity is brought on line. Conversely, lighter load causes increasing voltage, and frequency, and capacity is shut down. Fortunately, most loads respond to increasing voltage and frequency by consuming more power, and less power if the voltage and frequency drop. This results in a fairly stable system that is controllable most of the time, voltage is stable within a few percent, and frequency to within a fraction of a percent.
On a big grid the voltage changes happen slow enough that in the old days, there was time to make phone calls to bring plants on line. Occasionally a big event would occur and the response was too slow, and the whole grid would collapse. Computer controls now respond in fractions of a second, so massive outages are not as common as they used to be. Huge customers like aluminum smelters might agree to give advance notice when they go on and off line, so the the utility can have the generators spinning and ready to pick up the load.
To keep clocks from drifting, utility grids typically run the frequency a tiny fraction of a Hz high at night, to make up for the lower frequency that happened during the day. They actually count cycles, and while they may not hit the target one day, they will make it up the next.
Generators that are spinning but not at full output can typically pick up additional load quite quickly. Usually only requiring that throttling valves to turbines are opened farther. There is quite a bit of stored energy in the boilers that can be tapped on short notice, and this can smooth the load over timescales of a few minutes, giving time for the heat input to the boiler to be increased.
Actual storage is rare, but pumped storage has been used for many decades, and there are some new battery technologies that are seeing limited use. In general though, electrical power must be generated as it is consumed.
My late uncle actually worked at a pumped storage plant in Colorado. In addition to load leveling, it allowed the the utility to run the feedwater pumps at one of the coal plants and bootstrap their grid if the whole thing went down, which it did once a decade or so.
At the Kinzua dam boondoggle in Pennsylvania, they didn’t bother to put in turbines to generate electricity. The power company did build a reservoir up on the plateau and installed pumps and turbines to pump water using power generated elsewhere for pumped storage.
Not to rain on parades, but turning off lights doesn’t really mean more is going to be stored in a pumped storage reservoir. The pumping schedule is largely pre-determined the day or even week before, so the decision at the customer end-point does not affect the utility’s pumping strategy.
The main benefit of pumped storage is lower operating expenses. Power is cheap to produce/buy at night and expensive during the day. At night nukes and efficient coal plants run extra (beyond explicit demand) to fill the reservoirs, which are emptied during peak hours to avoid having to bring more expensive plants online or purchase power at market prices which can be exhorbitant if there are unplanned outages. If a utility doesn’t have its own plant capacity to fill a reservoir, it will still buy cheap power off the market at night to fill it. Stored energy in a reservoir isn’t 1-for-1 input/output. There’s a rather large mechanical/thermal inefficiency factor, but the pricing differences between peak/off-peak still make it worthwhile.
Additionally as others have mentioned, there are efficiency benefits to using pump storage to avoid cycling of other plants, reducing the overall wear and tear on them.
Unfortunately, there’s unlikely to be any more pumped storage coming online in meaningful amounts. Blowing holes in mountains and creating new reservoirs by flooding valleys doesn’t go over as smoothly as it used to.
One of the ways in which electricity is stored is water reservoirs. Those artificial dams have two uses: to store water and to produce electricity, and some of them change the amount of water being released (and bring turbines on/offline) in response to power demand peaks.
The most extreme case is Scottish Power’s Ben Cruachan Power Station. An artificial reservoir built on top of a mountain, rather than on a river’s path; water is pumped up during low-demand times, released (producing electricity) on peak times. Probably the most expensive electrons in the world, as inefficiencies mean that pumping the water up actually needs more energy than what’s produced back when it falls down.
The amount of money and ingenuity being invested in getting fast responses and making sure that what’s being produced is as close to what’s being demanded as possible is enormous (yes, I’ve worked for a power company: the diversity of industries is what I love about being a consultant).
70% of home heating in Quebec is electric and turning off the lights in winter doesn’t do a thing. My home is heated by electricity except when the temperature is below -12 C, when it switches to oil (we get a 20% reduction in electricity rates for agreeing to this). They don’t use pumped storage but they readily adjust the amount of water flowing over the dams.
It costs roughly $0.0025 per hour to light a 100 watt compact fluorescent bulb. That means that if you turn it off instead of leaving it on for 10 hours every night, you save 2.5 cents of electricity a day, or 75 cents a month.
Small appliances cost virtually nothing to run, such as your alarm clock, or your computer, or your TV. Even an electric dryer only uses about $0.35 per load. The biggest consumers are heat and air conditioning. Depending on the size of your unit (that’s what she said), the cost to run central air could be as much as $15 a day. Electric hot water heaters can consume about $60 a month.
I’d wager that 90% of everyone’s electric bill is heating/air conditioning/and hot water heater.
[QUOTE=anson2995;13542646I’d wager that 90% of everyone’s electric bill is heating/air conditioning/and hot water heater.[/QUOTE]
The other big items are refrigerators & freezers. These are cooling, just like air conditioners, and they also run constantly, year-round.
For an average refrigerator, I think the total electricity cost to run it over it’s lifetime is about 3 or 4 times the purchase price. (So it’s worthwhile to look for an efficient model.)
