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which is probably quite infeasible, hence I post it ehre instead of patenting it and making millions. The idea is to make a device that you can plug into the power wire coming into your house, before any appliances see the power. The device has three states: 'Off', does nothing. 'Gather', takes in some amount of power from the grid and stores it, in a battery of some description. (Not necessarily a chemical one, of course.) 'Provide'; when an appliance in your house is switched on, part or all of the power comes from the device.
The purpose, of course, is that you switch the device to 'Gather' when electricity is cheap, and to 'Provide' when it is dear.
The problem lies in the efficiency. Just how efficiently can we convert electric power to stored power and back again? Let's suppose that the net efficiency is x; that is, if I take in 100 Joule and store it, and later reconvert to electric current, I get x Joule. Then clearly, in order for the device to save me any money, price swings need to be 1/x. In other words, for those 100 Joules I pay y; when I tap the device to get back x Joules, the price needs to have risen to at least y/x. (If my efficiency is 50%, the 'dear' price needs to be twice the 'cheap' price. If my efficiency is 1%, we must have dear at 100 times cheap.)
So, how efficiently can we store power given that both input and output are voltage? What do you think, gentlemen? If we were to use, say, an electric motor to pump water up into a storage tank (and run in reverse as a generator to get the power back) we might get as high as 30% in each direction, for 9% total efficiency. Alas, I don't think electricity prices swing by any factor 11, and 30% is optimistic anyway. Anyone want to think of a better method?
Another point to consider is that in principle you could hook up an exercise bike to whatever storage you use. Of course, no human is going to generate significant amounts of electricity, but you can console yourself with the thought that each revolution of the pedals is saving you some minuscule amount of money.
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It's very inefficient to store power in batteries and then later use it. The thing you're describing is called an inverter. It's similar to a UPS. That's what a UPS does, and you see how long they last, how expensive they are, and how much power they can support. Mine at work can keep one computer running for about 20 minutes if the batteries are brand new and shorter if they're old.
There's no easily portable, cheap, and efficient way to store electricity, unfortunately. (I'm talking about power levels that run fridges, pumps, house- or office-sized lighting loads, etc. not small electronic devices which do fine with batteries.) That's why the power company actually has to generate, moment by moment, in their power plants, the exact amount of electricity customers are using at that moment on the grid. It means that we have to have enough power plants, transmission lines, substation capacity, etc. for the peak power demand (which here is in the summertime because of air conditioning) even though it doesn't get fully utilized for most of the year.
Generating enough electricity to keep the world working is actually pretty tricky business. I think in the future more of the generation will be localized, in that people and companies will buy their own generators more often, since they can't afford to have outages anymore, even short ones. However, this just transfers the infrastructure to fuel deliveries, since the generators have to get their power from somewhere.
Fossil fuels, gasoline, diesel, etc. are really the very best means we have right now of portably moving energy around. In the future when those are mostly mined out, we will have to use liquified hydrogen or ethanol instead, but these aren't *sources* of energy, since they take more energy to make than they deliver. They're just forms of transporting and storing energy. Does that make sense? The source will have to be solar (harvested in corn or other crops, or collected in space), nuclear fission (from uranium mines or reprocessed wastes), nuclear fusion (from hydrogen extracted from sea water) or some more exotic source.
The losses involved in storing power in batteries and using it later are far more than any possible difference in peak vs. off-peak electrical prices. So, yeah... that idea won't work.
Keep thinking, though. You might come up with something that does work next time.
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Another couple of ideas: As we both pointed out, it's not feasible as a money-saving device unless you either get much larger price fluctuations than we have now, or come up with an efficient (say, one-third energy loss) way of storing electricity. Besides, if it were installed on any large scale, then obviously the effect would be to flatten out price fluctuations in any case. But if you could store a large amount of energy - and as I said, the battery doesn't need to be chemical; for house installation, we aren't limited by size to any great extent - then it could work as a sort of house-wide UPS.
Another point is that it could work well together with a solar-cell roof; if at any time your roof was generating more power than you were using, just pump it into the storage. This gets rid of all the problems with trying to pump that power into the grid; just synchronising the phase of a large number of small AC generators would be hell. Sure, it's inefficient, but if you aren't using the power anyway, the alternative is to waste it as heat.
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Here's an idea I had. Well, it's not a complete idea but it's a line of inquiry. Turns out power plants convert about 1/3 of the energy they liberate into electricity, and the other 2/3rds is thrown away as waste heat. The amount of energy sufficient to power a couple of decent sized cities goes into the atmosphere in the form of heat out the top of our cooling towers all the time. Right now it's being used as an elevator for all the soaring birds of prey for five counties, and that's the only useful work it does. (It's awesome to see this huge column of hundreds of birds taking advantage of the elevator, though.)
Surely, surely, there's a way to recapture even a fraction of that energy in some useful form?
One idea is called Combined Heat and Power generation (CHP). Hotels, office buildings, malls, and other large structures can run a generator using natural gas or diesel fuel. Even though they don't have the efficiencies of scale that the utility company has, they have an actual use for the hot water. The hot water can be used for heating, laundry, baths (in the case of a hotel) and as a power source for absorption chillers which make cold water for air conditioning. The hotels are still hooked to the electric grid, they just use a lot less power. It's a major increase in efficiency and has the added benefit of being able to act as a backup power source during outages (with the right switchgear).
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But I still think there must be some device we could install in the cooling towers to turn some of that waste heat into more electricity or something. I just wish I could think of what it would be. Posts: 6246 | Registered: Aug 2004
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Synchronizing isn't that hard. It can be done automatically by the controller. It deliberately puts the generator ever so slightly slower than 60 Hz then waits until the two sides are very close to being in phase, and closes the breaker. Once the breaker is closed, the local generator WILL stay in phase, because it's not going to be powerful enough to drive the whole grid into a different frequency.
I mean it does take being able to measure both sides accurately, which means it's not cheap, but it's very doable. Also, the way you protect the grid from your own power you generate being sloppy or unacceptable in any way is with a relay that senses the power quality all the time and opens the breaker if you have any disturbances. It's also not cheap, but it's very common and doable.
The switchgear to automatically put these things online and offline is not cheap either. I guess that's why the scale of what's economically feasible right now is mall-sized or hotel-sized. House sized, as you pointed out, isn't currently worth doing.
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Hmm. This source gives the following numbers for hydrogen fuel cells:
30% losses for water make-up and electrolysis: factor 0.70
10% losses for compression of hydrogen: factor 0.90
10% losses for distribution of gaseous hydrogen: factor 0.90
3% losses for hydrogen transfer: factor 0.97
50% for conversion to electricity in fuel cells: factor 0.50
10% parasitic losses for the hydrogen fuel cell system: factor 0.90
10% electric losses in the drive-train between battery and wheels: factor 0.90
That's for cars; since we want to generate and use hydrogen at the same place, and aren't putting in any drive trains and whatnot, we can ignore the last factor and the transport losses, while putting in an extra 5% 'storage' loss since hydrogen is rather good at escaping from tanks. So, a total efficiency (both ways) of 26.9%. Now you only need a factor-four fluctuation in price. Conceivably that could happen in places like Norway, which relies mostly on hydropower. You should see the screams in Norway when the autumn and winter rains fail and the water level in the dams gets low; so the price of power tends to be quite seasonal.
Edit: Hang on, I think that 'distribution' accounts for what I was calling storage. So make that 28.35%.
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quote:Generating enough electricity to keep the world working is actually pretty tricky business. I think in the future more of the generation will be localized, in that people and companies will buy their own generators more often, since they can't afford to have outages anymore, even short ones. However, this just transfers the infrastructure to fuel deliveries, since the generators have to get their power from somewhere.
That's why the future will be RENEWABLE microgeneration. You can supply your own power, send excess back to the grid, and never have to worry about fuel.
KoM, the problem with what you're talking about, currently, is price. Well, the price of various things actually. Most of the country doesn't have a tiered pricing system for power, in that, energy costs the same at night when demand is low as it does during the day when demand is high. It's silly, and it's stupid, but that's generally how it is.
One of the big arguments against wind power is that the wind generally blows at night when people don't need power as much, and isn't around as much during peak demand. There's some truth to that, though recent studies show that wind power works as a base provider for power. Anywho, the solution being tested (with smashing success) right now is having that excess power compress air during the night and then let it out during the day to drive a generator. It's very efficient.
Ethanol btw, though I loathe it in its current form, does have some promise in giving us more energy than we put into it. Cellulosic ethanol, biobutanol, and a few other experimental fuels are efficient enough of a process to give us more power than we put it, and can actually be transferred by pipeline, unlike corn ethanol, to say nothing of the fact that we aren't using foodstock for fuel that way.
The other price problem I mentioned is the price of those batteries. Newer LION batteries are coming into play right now. A123 Systems, Johnson and Johnson, Continental and a few others are releasing the next generation, which are smaller, much more durable, last longer, hold a LOT more energy (maybe even substantially more if newer breakthroughs pan out in the next five years), and if electric cars really take off, the price will seriously come down for them. But right now home batteries are too expensive to make any sense. The price of the battery itself would take longer to earn back in savings than the battery itself would last. You need to wait maybe a decade for the tech and the price to catch up on that one, but it's not a bad idea. Some people still do it, mostly rich people with large solar arrays, but it's still there.
The future of electrical generation to me hinges on a couple things:
1. Microgeneration. It's being embraced by thousands. The idea is that instead of one powerplant producing a GW of power that has to be sent for hundreds of miles over poorly efficient power lines with transmission loss using fossil fuels, instead all those customers will power themselves, be it through small home sized wind turbines, solar power on their roofs, or even geothermal, as is being explored for home use at the moment. Businesses are already loving it. Offices, factories, and buildings of all sorts are having solar arrays built into their roofs and surrounding areas and are seeing instant savings from lower energy bills. It has a wide array of advantages over centralized power generation (and some disadvantages, but I think the pros outweigh the cons)
2. Revitalize the energy grid with a HVDC network, HVDC stands for High Voltage Direct Current line. They are vastly more efficient than ours is now, sending energy further, faster in greater amounts with less loss. Europe us currently mulling a massive grid that would span the continent and even cross over into Africa, where they hope to tap solar power from the Sahara.
3. Switch what mass generation we have left from fossil fuels to large scale renewables. They're feasible, they are cost effective, and we have the room for them. The arguments made against them in the last decade are moot points now.
4. New laws governing home construction similar to what Germany has just employed. Demand that new constructs be much more efficient over current standards to reduce future energy use as our nation grows.
5. I'm playing around with something at the moment (I was going to start a new thread on it similar to KoM's) whereby the state (not the federal leve, the state level) could act as a third party go between, between lenders, builders and home owners to get people to install solar panels on their homes for no cost. Such partnerships abound in the business world. What happens is, a lender will give money to the homeowner, who will hire a builder, they'll install the panels and then the lender will technically own them, for a fixed period of time. The homeowner then gets a deal on power, for maybe half the rate of what they were paying before, but never has to pay for the actual installation or maintenance, that is done by the lender. After 20-30 years, ownership reverts to the homeowner. It's happening a lot in California, but it'll require tax credits for renewable energy construction in other states if the same sort of thing is to be mirrored. The lenders are essentially making the bulk of their money from the tax credits, otherwise it'd sort of be revenue neutral. But it's win-win-win for everyone.
I have to go, I'll post more later.
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Water-powered generators have an efficiency up to 95%. Electric-powered water pumps have an efficiency up to 90%. So the combination with a reservoir as a supply&demand-matching system would have a battery efficiency of up to 85%.
quote:...long before I ever ran across the Galala proposal, using Norway's fjords was my first thought after that of multiplying US hydropower production to act as a windpower storage "battery" -- by using excess windpower electricity to pump the hydropower-released freshwater back up into the reservoirs -- led to thinking of damming across inlets on the US coast.
Consider low dams placed across the fjords to store energy -- using excess windpower electricity to pump seawater up into the reservoirs -- to allow hydropower production to fill in shortages when windpower production is less than the electricity demand. Norway could remain the wealthy"oil"exporting nation, ie power capitol of the EU long after its NorthSea oil&gas fields ran dry.
And 6 posts up in the same linked thread, a minor rewrite of what I had previously posted here sometime before April 2003, which was deleted from the archives due to one of the forum glitches:
Annual Wind Energy Potential in billions of kiloWatthours for wind class of 3 and higher, factoring in environmental and land use exclusions.
.North Dakota 1,210 ..Nebraska 868 ......Colorado 481 ......Illinois 61 ...........Texas 1,190 ..Wyoming 747 .New Mexico 435 ..California 59 .........Kansas 1,070 .Oklahoma 725 ...........Idaho. 73 .Wisconsin 58 South Dakota 1,030 .Minnesota 657 ......Michigan. 65 .......Maine 56 .......Montana 1,020 ..........Iowa 551 .....New York. 62 ....Missouri 52 - - - - - - - - - - - - - - - - - - - - - - - - - a minor revision of my writings elsewhere which was also posted here previously - - - - - - - - - - - - - - - - - - - - - - - - - First, I'm not sure whether the AWEA's "energy potential" means 1) total wind energy, or 2) the amount that could be realisticly extracted&converted into electricity, or 3) what could be delivered in a timely manner to satisfy the electricity market's usage demands, or something in between. And it's a BIG step between potential energy and usable electricity.
Assuming that it is 2), there is the problem of peaks and valleys in power production. Somewhat smoothed out through averaging across the national powergrid, but it is still a headache. A better storage system will have to be devised to even come close to making maximum utilization of the potential. After the initial production of electricity, there's a way to come up with a bit better than 80%efficiency thru the conversion to storage to reconversion for usage process (not counting transmission losses). However, I don't know whether or not there is sufficient potential storage* capacity by that means without really mucking up the environment.
Wind power machinery coexists quite well with farming and ranching operations. The AWEA figures probably included farms and grazing lands as the majority of their windpower production areas, though they don't seem to include offshore production. And most of the US is connected to the NorthAmerican powergrid. Present US electricity use is about 3800billion kWh, or 13000 kWh per capita (per person average).
Assume that Texas&Colorado has the same per capita usage as the US. Then that Colorado&Texas could provide for the electricity demands of their own ~26million people with ~338billion kWh of useable electricity converted from their 1671kWh windpower-potential. That would imply ~20% conversion efficiency from windpower potential to usable electricity using interpretation 2) of AWEA's numbers.
So, beginning with the assumption that the Texas&Colorado combination would use all that could be produced in those two states, there's no reason that the rest of the top twelve states (those with high windpower potential and relatively low populations) can't become major electrical power exporters. Using the same 20% potential-to-usable conversion efficiency, the other 10 states in the top 12 could provide ~1,680billion kWh to the NorthAmerican powergrid.
So the top twelve windpower states could produce about ~2018billion kWh, or ~53% of the ~3800billion kWh produced in the US. Add the 7.19% currently produced by hydroelectric generation and 19.84% produced by nuclear, and that's ~80%.
Considering that the older&prosperous members of the EuropeanUnion use ~5400kWh per capita or ~41% of the US per capita to maintain an equivalent lifestyle, there is obviously room left for improvements in efficiency of US utilization. So it's hard to believe that the US would suffer by using twice as much electricity per person as the more prosperous EU nations.
But even assuming that the US would want 100% of current production, reduction of fossil fuel generation from 70% to 20% of the total would create a substantial reduction in demand for fossil fuels. There would also be a more favorable US balance of trade due to lessened oil&gas importation, as well as from the lessened world oil&gas prices due to a decrease in US demand-pressure. And lower fuel cost would mean cheaper generation of electricity by the fossil-fuel plants that remain, as well as less strain on the environment.
Remember this is at 20% conversion efficiency in the top twelve windpower-potential states**. At ~38% efficiency those same twelve states could provide 100% of US electricity needs**.
And remember it does not include conversion of the 38 other states' windpower-potential. Nor the offshore windpower potentials of the states: which would be substantial, especially for the coastal states not counted amongst the top twelve. Then there is the VAST excess Canadian windpower potential: which I'm sure they would be happy to sell, in the same manner as OntarioHydro/etc currently exports surplus electricity into the US market.
100% windpower production of baseline electricity needs presents opportunity to reduce oil&gas importation in other ways. Which I'll return to.
* A schematic of the proposed Galala-RedSea power storage system which could be adapted for use -- including matching demand peaks&valleys to production peaks&vallleys -- with solar/wind electricity powerplants.
** Both statements do not include storage-conversion losses and transmission losses to&from storage sites.
quote: Right now it's being used as an elevator for all the soaring birds of prey for five counties, and that's the only useful work it does. (It's awesome to see this huge column of hundreds of birds taking advantage of the elevator, though.)
Picture? Or better still, link to video? That sounds cool.
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Sorry KoM. It's been around for a long time. Your suggestion of doing it at the customer level lacks the efficiency gained through economy of scale.
Also, I've heard of cogeneration schemes using cooling water from power plants to heat surrounding buildings. As I understand it most of these systems are in scandanavia.
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Well, of course it does; that's totally beside the point. The question you should be asking is whether, with modern technology, it can nonetheless be made a good investment for an individual.
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Enigmatic, I'll try to get some good footage when I'm at the plant next month. Right now I have one still in which you can barely see a few black specks of birds. Here it is. The birds are large birds of prey but they look basically like tiny black specks in this crappy cell phone snapshot. You have to realize the scale of the thing, and understand that the specks continue to get smaller all the way up to the limit of vision.
Here's a cool picture which was taken from the top of one of the towers. They're 550 feet high so you get a nice view.
quote:Originally posted by Glenn Arnold: Sorry KoM. It's been around for a long time. Your suggestion of doing it at the customer level lacks the efficiency gained through economy of scale.
Also, I've heard of cogeneration schemes using cooling water from power plants to heat surrounding buildings. As I understand it most of these systems are in scandanavia.
Not necessarily, I mean, someone has to build all those batteries for the homes. You build 200 million batteries, the price comes down, and storing energy in the home becomes a lot more feasible.
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quote:Originally posted by King of Men: ... Alas, I don't think electricity prices swing by any factor 11, and 30% is optimistic anyway.
I think you might be right, at least in my jurisdiction. In Ontario, the electricity mix is roughly 41% nuclear, 24% renewables (mostly dominated by hydroelectric), 15% gas and other, 19% coal. When I was working in the industry briefly, the SOP was that as Glenn Arnold linked to, since less power is used during the night, essentially what happens is that the hydroelectric is turned off and reservoirs filled. The expensive and polluting coal and non-renewables are shut off even before that. The nuclear power essentially runs all the time since it is very difficult to start and stop.
So (depending on the efficiency of your mini-storage of power) all you'd really manage to do is almost arbitrage the difference in electricity prices between hydro+nuclear and (hydro+nuclear)+gas+coal, that is if the government let you and set it up properly anyways.
Of course, the market would react, as more people do this, less gas and coal would run during the day anyways making the scheme less financially rewarding (although still more environmentally rewarding).
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quote:Not necessarily, I mean, someone has to build all those batteries for the homes. You build 200 million batteries, the price comes down, and storing energy in the home becomes a lot more feasible.
Economy of scale implies that each individual system be large in order to become economical. 200 million little batteries that each require their own inverter and maintentance infrastructure would be inherently inefficient compared to a huge bank of batteries with one big inverter and an industrial support infrastructure.
The only way I could see home systems being worth it is if their main purpose is not to dampen the high and low cost of power, but to provide an uninterruptable power supply for homeowners that are willing to pay a premium to avoid the inconvenience of blackouts. It would have to cycle daily to take advantage of cheap nightime power, which means that there would be a period each day where it would be largely discharged, so at that time of day, it wouldn't provide much backup.
I think the most effective power storage system at that scale would be a flywheel energy storage system.
quote:When I was working in the industry briefly, the SOP was that as Glenn Arnold linked to, since less power is used during the night, essentially what happens is that the hydroelectric is turned off and reservoirs filled. The expensive and polluting coal and non-renewables are shut off even before that.
Hydro plants do fill the reservoirs at night, but pumped storage actually uses power generated by other sources to pump water uphill. In some cases they actually keep the coal fired boilers running all night because they lose too much energy when the boilers cool down, and it takes too long to reheat the boilers to accomodate the surge in demand when everybody wakes up and turns on their coffee maker at 6:00 AM (or whatever).
Another bizarre scheme I know of is to shut off the boilers at night, and then when demand for power comes up suddenly, they'll burn hydrogen to produce high-quality steam, which allows them to bring turbines online instantly. In the meantime they heat up the coal boilers and switch off the H2 burners as the coal boilers come up to temperature.
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Does power really get cheaper during the night when we're talking about end users? I had the impression those prices only varied seasonally or even yearly. Perhaps it depends on the region as well as the nation?
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Thats what I meant for "if the government lets you." There are several municipalities in Ontario that are piloting so called "smart meters" which will give different prices for electricity at different times, e.g. cheaper at night. There are also some big industrial users which are (sometimes? not sure if it is a constant arrangement) charged low rates in exchange for running their equipment at night.
However, for the majority of users, the price is the same at all times and the government pays (or rather they set a corporation which pays) the difference between the "seasonal" end user rate and the "actual" rate which has to change at night anyways (or when we import power).
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I think that the current electricity regime could stand a significant liberalization, and that, using a fairly simple framework, a situation allowing for significantly improved service due to competition would arise.
Of course, the fake 'deregulation' schemes that have been tried in a few places have soured people on the idea, even when those schemes were far from deregulatory.
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