Most Efficient Way to Save Energy

"I am thinking of saving electrical energy"

I think you are thinking of storing energy.

Saving it lets everyone else use it. Storing it "saves" it for you.

What's the goal?

Regards

A GA for good reply.

I like to point out that this is only possible where you have also redundant Power to pump up. &

If the space for storage is available you better to Up-rise the water-torage area.

How about an hydrogen generator?

BTW:

In many states, you can sell power back to the power company at the same price you pay for it. This arrangement is by far the best for "storage" (although you are not really storing it) and of course it means that you remain connected to the grid. In some places you could sell your energy at high daytime prices and (if you have an electric car) buy it at cheap prices to charge up overnight (or perhaps heat a day's worth of domestic hot water overnight in a very well-insulated tank, so that your water heating expense goes down.)

Personally, I think that (remaining connected) is a good thing, because it can improve the overall efficiency of the grid, and helps to implement "alternative" energy sources. (I am none to keen on the word "alternative" because it suggests that there is a single "normal" source and other, ostensibly better "alternative" sources. The wording over-simplifies an extraordinarily complex problem... and leads to bad legislation in which, for example, any "alternative" energy source is given a 6:1 advantage over other fuels in CAFE standards -- it does not matter if the alternative causes a net increase in energy consumption . That alternative could be whale oil... or ground up and gasified spotted owls)

If you sell power back to the utility, then they can deal with storing the energy, by, for example, pumping water up to a reservoir -- something which can make sense for them but not for a consumer... unless the consumers name is Bill Gates.

If the drive for "storing" energy is economic, and to enable you to use wind and solar economically, then in net metering states, this can be much more effective than the hassles of dealing with batteries, etc. If the drive is to disconnect from the grid, this does not work at all, of course.

Actually the method used by many to discourage use of H2 is but one way of production and incidentally the least efficient at that.

Yes H2 generation can be about 92% efficient overall if we consider use of wind as the driver of the electrolysis or if indeed H2 is the driver then we have only a one time expense to begin the operation. After which the efficiency is over 90%.

May it be fur will fly

I heard A rubber coated fabric was good see U V"s avatar

Read the low down on hydrogen

Why not leave it in the water until ready to use?

I think you're doing the right things the wrong way.

If I leave the H₂ in the water until I require fuel, then using a residual energy from the last evolution to start electrolysis and produce more H2 the water is the storage unit.

Yes; you are correct, it should have been store, not save.

The idea is to store some cheap(er) energy, (e.g wind)
and use it in replacement of the mains during the expensive
daytime rate period. (night time it's cheaper.)

The hydrogen is interesting, - to run a motor/gen?

Before embarking on what may be a very expensive outing,
I would seek advice on the most efficient (cost effective)
means of storing it.

jt.

Microgeneration, using wind or solar photovoltaic systems, is becoming common, even popular, these days.

When a local power source is available, the electronics attached to the energy source "pushes it back into the grid", effectively making the meter run backwards, as it were, lowering power bills for the installation. Effectively, the grid itself becomes the energy store.

The economics of it need to be discussed with the equipment supplier and a decision made upon the likely rate-of-return on the investment.

The practicalities of it need to be discussed with the power supplier. There may need to be a change in the supply tariff for buildings that have microgeneration attached to them.

The installation may need to be discussed with the local authority's Planning office, as some installations might tend to inflame local sensitivities, particularly if they are on a prominent part of the building.

Slap me if I'm wrong, but I think you get an additional meter to monitor electricicy generated. Somewhat bizarrely, it doesn't matter where that electricity goes !

There are two main ways to go about exporting your renewable electricity – via flat-rate generating payments or net metering arrangements.

If your micro-generation system is fairly small and largely intended to help supplement your own energy needs rather than expected to produce a significant surplus, the flat-rate payment option – which pays a small sum for each unit generated – is probably the best way to go. Source.

Although the unit price is quite low, the advantage of this system is that you get paid for generating the power – it doesn't matter if you use it yourself or it ends up entering the grid as surplus to your own requirements.

that can be transported with a lot better efficiency than wires carrying electricity.

In a system like the OP contemplates, wires carrying electricity are unbeatable, and if properly sized are better than 99% efficient. He does not need to transfer the energy over hundreds of miles but only a few feet. Pressurizing a gas as an energy storage means is very low efficiency, as you can prove to yourself by feeling the cylinder head of a running compressor. In ordinary industrial usage, compressed air systems are often only about 15% efficient.

To be fair the description is not a view of general industrial usage but one of attention to conservation of energy devoid of the greed of industry.

Using energy derived of wind to pump water above a turbine to generate a more useful form of energy is not less efficient.

One could argue of what form is our most efficient commercial energy source in use today? And what was the initial cost of creating all that pressure?

Very informative, however we of CR4 often overlook the reality that many times a small foot print system can be exceptionally efficient for individuals or small communities.

bwire -- You're absolutely right on this. In general the smaller the energy conversion system the more important the human part becomes. Especially when people are directly involved in managing, building or maintaining equipment that some or all depend on.

Take me as an example........I just don't want to know what electricity out of my Honda generator costs me per KWH. But it's there when Pacific Graft and Extortion (44 cents/kwh) turns the power off to twiddle around with some problem caused by a tree their arborist contractors should have dealt with long ago. (but not this week; the generator is in the shop at $95/hour; GROAN!!)

Ed Weldon

I've a neighbor with a homemade archaic wind powered electric generator. I don't suppose many engineers would waste time on determining it's efficiency rating. It's a VAWT using barrel staves to harvest wind and a old pickup truck rear axle assembly including brakes and differential. Surprisingly though it may appear crude it does faithfully provide the electricity they require.

Sounds pretty slick, bwire. How is it set up? I'm guessing the axle centerline is vertical with the VAWT bolted on the upper end of the axle like a wheel. Then the pinion drive shaft coupling is connected to a generator mounted horizontal. Is it direct coupled or some gear/belt/chain hookup? In other words do you know what the speed ratio is? I wonder whether the differential is locked or the lower brake drum or axle is locked. (the latter would half the speed ratio). Lastly, what grade of oil does he use in it and how does he keep it from leaking out the end of the bottom axle? The original 90w gear oil or something lighter? Also does he know what kind of vehicle the axle came out of. The type of gear in the ringand pinion would have a bearing on whether a light weight oil could be used given the low level of power being put through it.

Some years ago I took some pictures out at the Bodie Ghost Town (CA State Park in the Eastern Sierras) of a homemade water well drilling rig set up the same way on an old truck chassis by some long forgotten clever mechanic.

Ed Weldon

I believe is a Dana axle from 1950 1-ton Chevy truck. There an expansion plug like that for engine block in place of the bearing race which prohibits the gear lube leaking out, the other wheel bearing is replaced with Nylon impregnated with graphite, setup has been in use about thirty years. It is direct out to a gearbox; the torque is great from the antiquated setup, all gear lubes are synthetic and sealed appropriately.

bwire -- Thanks for the info on the axle setup. Sounds like a good framework for a "how to". I like the idea of the axle because of the brake setup. It would be pretty straightforward to rig a flyball governor that would actuate the brake if the wind got to blowing too hard. This can be a problem for wind turbines. The other nice thing about rear axle housings is that you can weld structural mounts to them without having to worry about messing up the machinery alignment. Then, of course there is the ease of finding and low cost of parts to repair. .........Ed Weldon

Ubetcha!

Can you say thanks Enron

When the market was deregulated here, I saw a Enron official saying how the rate was going to be more like 75cents/kwh & how they couldn't possibly make any money at 11cents.

PG&E signed a bunch of bad long term contracts @ what seemed like a better price, the whole state was crawling up their ass over the blackouts.

somebody tell me again why regulation is bad?

Should municipal energy be a publicly traded commodity?

You mean like this?

PG&E actually got stuck in the middle of a bad law & the state & consumers & Greedy operators of peak plants

Forget local storage unless you are going to generate your own electricity using wind or solar power. Both of those do not make economic sense for most people!

Just switch off energy consuming devices that you are not actually using, including standby mode on computers and televisions.

Live reality not the dream if you want to avoid wasting money!

Best wishes

Adrian

I agree 20% efficiency is very poor. However, you may want to recheck your efficiency estimates for rechargeable batteries.

http://en.wikipedia.org/wiki/Rechargeable_battery

I regularly get 80% from my lead acid batteries and usually above 95% for my Lithium Ion packs.

Battery technology has improved over the last 20 years, but the REAL improvement has been with efficient chargers and how they are optimized for a specific battery chemistry.

If you used the older style linear chargers, line to load efficiency would be low (<40%) and battery life poor.

I'm currently using switching "smart" chargers which run in the 95%+ efficiency range. They are now fairly common and quite reasonably priced. Under-charging, over-charging, and improper maintenance charging are all eliminated. Real time "energy in" measurements are displayed continuously until charge termination. No tedious measurement or guesswork required. Test modes also allow you to use the smart charger to automatically discharge a battery, record its "energy out" capacity, and determine its condition.

These new chargers are a MUST HAVE if you intend to get the maximum life from your batteries. Considering that a battery bank may be >75% of the storage system cost, a few extra bucks for a smart charger is a bargain.

GA...Thank you for quantifying the elephant in the room...

Just to give you an idea... My father and I placed solar panels on his roof to generate power to store for nighttime use. One of the problems we had to deal with on our original plan using batteries to store the energy were the many maintenance and procautionary measures required. Like hydrogen gas, power vs. temperature, water and acid monitoring & replenishment and etc. We finaly decided to cut the batteries out of the picture all together and let the power go straight out to the power company and use power when we needed it. Most of the day, our power meter ran backwards. Given as someone said before, conservation practices should be preliminary. I hope this helps.

Is there a compressor that is driven by a windmill without a generator and motor?

This could be the way to go. Use the compressor for the heating and cooling and use another windmill for producing electricity for the rest of the household uses. Or, maybe have a windmill that does both. Don't worry about the efficiency of the power conversion since the wind is "free". Design for the end result, i.e., cooling and heating and electrical power for lighting, refrigerators, and other household use. I think you may be on to something.

PAPADOC

THERE'S ONLY TWO THINGS IN LIFE THAT 'S FREE AND THAT'S LOVE AND HATE AND EITHER CAN HARM OR KILL YOU—PAPADOC

There is a project underway to this extent and we should hear from them again shortly. You may review recent (within last six months posts pertaining to.

Consider this: A windmill that operates a compressor. The compressor sends air to a storage tank. The air from the storage tank runs an air motor that turns a generator.

The advantages of this system is the generator can be operated at a constant speed; therefore, providing constant AC 110v and 220v power. Naturally, controls would be required to keep the speed constant with changing loads. The energy storage would be the air tanks. If the air motor ran at, say, 35 psig, then have the tanks at 100 psig. When the tanks got below 35 psig, the air motor would have to shut down. The tanks would have to be sized to have a reserve of air to keep the air motor running for a specified time or energy equivalent.

I don't know the formulas or relative values to calculate the sizes for this system, but somewhere out there someone does. This system could be a "stand alone" or connected to a grid system. The down side is, of course, the size of the tanks. I used 35 psig because that's the vapor pressure of propane (+ -) and there's lots of those tanks already fabricated. I used 100 psig for max. because that's about the max. for a conventional air compressor tank and there's lot's of them being fabricated everyday.

So, what do ya think?

PAPADOC

RMFR

I'd have more fun if I had more money—PAPADOC

Scale and heat loss are important factors. May work for a utility, but doesn't seem like a workable system for the smaller scale end user. Start here for basic info...

http://en.wikipedia.org/wiki/Compressed-air_energy_storage

My calculations (if correct) indicate you would need at least 480 cubic meters of compressed air at ~300 psi to store 40 kW-hours of energy (OP's goal) not including heat and mechanical losses.

The cost of a pressure tank the size of my house (and where to put it!) would make this system impractical.

Compressed air to push water rather than pump it maybe, five PSI would be enough.

Changing the state of energy is a very lossy method. This would work fine if all you wanted to do was provide some supplemental heat or cooling. Since most of the energy used in the summer goes to keeping buildings cool, this would be a darned good use for it.

My compressor head (in my shop) gets so hot that you can boil water on it. The whole tank just radiates heat when we use it a lot. In the summer time, I need to keep it outside. The hand sanders however ice up, and my employees have to wear gloves to avoid frost bite. When they are in there sweating, the cool air is nice to have....people joke about the air conditioned blacksmith shop I run. In the winter, I bring the compressor inside, and turn off the furnace.

I found that I can't run the shop for very long with the circuit breaker turned off...compressed air is really nice but it really doesn't store all that much energy...I once compared the drilling power of my compressed air tank against the hand held battery drills...just because it interested me. (I had a line on a bunch of cheap air tanks....) I had a quantity of drilling to do, and so I flipped my circuit breaker off, and drilled every second hole in the job lot. When the drill would not work any more, I then turned to my Makita battery powered hand held drill, and filled in the holes. My admittedly unscientific method showed me that that big five foot high tank only held as much energy as three or four hand held Makita batteries. (actually two new batteries and two clapped out old batteries)

Now there was still plenty of pressure left in the tank, however the pressure drops off pretty quickly and becomes unuseable in a surprisingly short time.

Of course, the important thing was that the Makita drill batteries took some 12 hours to recharge (three hours per battery), and the compressor was back up to pressure in about two minutes. And the air drills were twelve dollars each, and the Makita drills were seventy five dollars each. And the air drills are not designed for effieciency like the Makita drills are. They are way NOT efficient! A different drill might well have gone twice as far...who knows.

Now this was just an experiment for my own thoughts on how to power a shop, and I throw it out there just to give folks some of my limited experience. My original idea was to purchase some cheap broken down compressor tanks from the auction (five bucks each!!!!), and was wondering if the loss of shop space would be worth the gain in reliability if I added a couple of extra tanks. There was none that I could determine.

I was debating on whether this experiment would be relevant to the original question, and I have to conclude that yes...it is. I "might" be able to charge up a half dozen tanks at night and get a day's use out of them. But I don't think the savings on electricity would justify the trouble. I dunno. What do YOU think?

Along the same lines:

If I run my air sander or an air drill constantly, my compressor runs constantly. The compressor is several horsepower, with a 10 gallon tank. (I think is has an inflated rating of may 4 or 5 hp, but it runs at about 12 amps on 120V, so it is actually about a kilowatt and a half, or about 2 hp. The sander and air drill are each on the order of 1/6 hp. (I'd guess that when using an air sander the pressure is about half of peak pressure, so the hp may be half -- maybe one hp continuous) Overall efficiency of about 15% or so. Electric motors are generally around 90% efficient, but the ones in small hand tools are probably really only 50-60% efficient in actual use. Plug-to-battery can be 70% or better -- so battery powered tools are not wonderfully efficient -- maybe 35% - 40% -- but that's a lot better than compressed air.

Typical efficiency for industrial air systems in manufacturing is 15% or so, but better if you are careful about leaks, compressor sizing, pipe sizing, etc.

A central difficulty in storing energy via compressed air is the physics that you alluded to: you heat air when you compress it. If it cools before you use it, then you've lost the energy of that heat. (In addition there is the heat generated from the friction of the compressor mechanism -- pistons sliding on cylinder walls, etc.)

Yeah....I am really intrigued by the idea of using compressed air for its heating and cooling properties rather than its ability to store energy. Its not very efficient at storing energy, I'm the first to admit. Its a pretty lossy system. On the other hand, tools driven by compressed air are lighter, simpler, use less resources to manufacture, are more powerful per kilogram, and don't ignite gasoline fumes with commutator sparks. Quite simply, air powered tools are superior. Thats why they are used. So if you have a prime mover, (say, a windmill,) driving a compressor directly, it would be lots more efficient than what I have now, which is hydro electricity driving a generator which would be driving a motor which would be driving a compressor.

grin!

Would not be without my air tools though.....just burned up another electric side grinder. Over heated, melted the brush holders, destroyed a lot of highly polished and engineered electrical components. Its all trash now.... Wonder if I can find an air powered side grinder. hmmmm.

air powered side grinder

Liquid sodium has a much greater specific heat than water, about 600:1 as I recall. This can make it a superlative heat-exchange fluid, but it requires special materials of construction to avoid corrosion.

Sodium has a huge specific latent heat of fusion (@ about 98°C), but its the specific heat capacity of liquid sodium is only about one third that of water.

Ammonia beats water on specific heat capacity per unit mass but not (at low temperatures) per unit volume.

Specific heat of fluids.

Helium and especially Hydrogen fall into the same category as ammonia in this respect.

Specific heat capacities.

................J/(g·K)...............J/(cm³·K)

....Water ~ 4.2 ..................... 4.2

Ammonia ~ 4.7..................... 3.3 (increases with temperature)

..Sodium ~ 1.3

...Helium ~ 5.2

Hydrogen ~ 14.3 !!!

Randall,

Thank you for the correction (GA, by the way). I was recalling the wrong column from the table, as it were (heat of fusion vs. specific heat).

Nonetheless, there may be some application to the original question. I haven't researched it much, but I was thinking along the lines of a solar concentrator that would melt sodium, and then extracting the heat for various uses. Thus far, the idea is quite primitive, but....

(By the way, I am an ammonia refrigeration engineer in a seafood freezing plant, and the points you mentioned on that are right down home.)

Focus light energy from collector upon a Fresnel lense...

That much sell it to the utility company and buy it back as needed.

That sounds good but....

the above mentioned PG&E will only pay you around 1/3 of what they charge you for electricity.

The ingoing & outgoing rate for electricity is rarely the same & needs to be figured into the total ROI [return on investment]

Somewhere in NY state between NYC and Albany is a reservoir created by pumping water from the Hudson River up to a ridge and then electricity is generated when allowed to flow back down with turbines inline.

Many municipalities use water towers, these towers do require some pumping though the greater effort to keep water at the top is available by siphon.

A lot depends, First of all what is the source of energy ( wind, solar, etc )

second, how much is weight a factor. cost wise, right now the cheapest is lead acid batteries (available in any auto store ) but in the long run LiFe batteries might be the best. LiIon and LiPoly batteries have the highest power to weight ratio, but the LiFe batteries are safer, and have a longer cycle life ( charge/discharge/charge etc ). Currently LiFe batteries are available in 3.2V cells w/ 10 to 1000 AmpHr current capabilities ( Probably best to buy 3.2V/100 AH and gang them to get the voltage and Amperage you need since the more cells you buy, the lower cost/cell. In theory Capacitors could be used, but they would have to be very large and right now are expensive. Pumping water up requires you have a place to store the water, either a holding pond or a water tower. I feel batteries, wether lead acid or the newer more efficient ( but right now more expensive ) LiFe batteries are the best choice.

In theory Capacitors could be used, but they would have to be very large and right now are expensive.

Just to amplify your thought: they would need to be monstrous and would be so expensive that naming a dollar figure could cause a heart attack. Capacitors have good power capability, but very poor energy storage capability. I'd considered using super capacitors for storing energy from regenerative braking is a small vehicle, but even for storing that small amount of energy, the cost is prohibitive.

I see that the EU is going to demand that Lithium Ion batteries will need to be recycled. Currently, they are rarely recycled, and they will be clogging the landfills any year now. This will no doubt add a huge amount to the cost of Lithium Ion batteries. Lead acid batteries of course, are almost always completely recycled. Seems that L-A batteries are big blocks of valuable metal, and it is easy to get somebody to take them. Not so with the L-I batteries.

Another consideration when planning a system...how expensive will it be to dispose of the batteries when they die?

http://www.computerworld.com/s/article/9001626/EU_approves_battery_recycling_law

You have to figure these expenses in! The up front cost, the disposal cost, the cost of charging systems, etc. etc. etc. Its too easy to overlook the little stuff...but as an engineer buddy of mine once said "90% of any job is the little stuff".

But to get back to the original question....

They just installed a "smart meter" on my house. Presumably it will penalize me for daytime electricity use. I have not had much experience with this system as yet. However my gut feeling is that I don't think one could buy "cheap" electricity at night, store it in a battery, and use it during the expensive day time and come out money ahead.

Really depends on the different rates and how you personally use electricity. If it's $0.04/kW-hr night-time and $0.40/kW-hr day-time, you might be able to justify an off-peak storage system.

A much cheaper solution would be to change your usage patterns and use simple timers to shift some of your electric loads to off-peak hours. A timer on an electric water heater is pretty common in some areas. Washer and dryer usage shifted to off-peak hours would help also. I prefer to use my electric oven for overnight low&slow ribs and roasts. This would tend to save me money if I had the dual rate metering.

Watch your electric bill and try to do you own calculations to see if ANY changes are worth the effort. Your total electric bill might not change at all.

That is a darned good point....and one I have made on this forum time and time again....so of course I totally agree with you! Conservation of limited resources will eventually be forced upon us whether we like it or not.

The original post simply asked what would be the most efficient way to store energy for about eight hours. If there was a reasonable, cost effective way to do it, then such a system would be useful for storing energy obtained during off peak periods, as well as being useful for other forms of energy capture. The idea of wind systems or solar systems or whatever is really not relevant.

I just don't like electricity generated from wind. Its too expensive. It may be useful in the event of a grid failure (blackout), expensive peak use times, or in places where it is difficult or expensive to get connected.

Personally,I feel that it would take a VERY high KW/hr rate to economically justify a wind turbine. This feeling is quantified by smarter people than me...

http://www.ecohuddle.com/wiki/how-to-buy-a-wind-electric-system

http://www.linkroll.com/DIY-Home-Improvement--146135-Wind-EnergyMore-Than-Affordable-for-the-Home.html

Bob Vila suggests that electricity costs should exceed 10 to 15 cents per Kw/hr before you can even think about breaking even, though there are many variables. He goes into those variables here... Clearly this is an economic decision.

http://electrical.bobvila.com/Article/769.html

and the best article I found about how to prepare for your new wind system was found here...

http://www.wikihow.com/Make-Your-Own-Electricity

High tech is rarely economic, though the exception may well prove the rule. That should not prevent us from trying though.

I heartily agree though many energy companies do not offer off-peak services.

Hi there. Thank you all for your input. (I have been following, if quietly)
Thank you to bwire, blink, ed, Rakesh, PW, Kris, Delmar, .... all of you.

Car axle; good idea, but I'm not of an age to struggle with axles.
The thought of using sodium, or such chemicals, eeeek!
Lead batteries (what I have now) are costly and don't last long.
I don't have any faith in compressed air. (no energy)
Pumping water? seems a sledge hammer for a nut; unsuitable location.
The power companies: Increasing the income of shareholders by supplying
or paying for what is (almost) an essential for life today; not my choice!
All essential services, IMO, should be state supplied in the most efficient
way possible. (as necessary for everyone. e.g. water. (avoid a soap box!)

Positives;
The 2 c.m. water heat storage, heated by wind generator, plus a heat pump.
Requires less regulation and maintenance. (the more auto.for me now the better)
This is something well worth considering to set up, I think. (long term solution)
I'm told the UK (govt.) is considering some form of subsidy for generation; likely
next year, as part of the self sufficiency drive. Interesting to see.

I really do appreciate some of the most practical minds (you lot) helping me to
consider the many different answers to a problem which really affects us all.
Many thanks, and my best regards to you all.

jt.

May I recommend the dvd/video "Life is beautiful" by Roberto Benigni.
(no financial interest.) Enjoy life while you can. jt.