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Cheap Solar Cooling Solution?
"I realize that the photovoltaic array will have to be of sufficient size to offer more power than will be consumed by peak load, causing excess power, that will need to be dealt with. Also, there will need to be some monitor so that if the available energy doesn't meet the minimum threshold, then the appliance is shut off (or the juice to the circuit is cut), and vice versa. As temperatures approach 120F and more this summer, I'm putting more aside for this project and at this point am not concerned with any but simple methods of using up 'excess' energy. Though thoughts have rattled around about a Linux controlled shading system to adjust the raw juice coming off the panels through selective shading."
If the concern is cooling, then one way of burning off any "excess" power might be creative use of fans (either single fans or a bank of them; small or large, depending on the amount of excess power available). What other ways might such "excess" power be used?
Flywheels are a really cool idea. I've never heard of one in practice, but they have been touted as a solution to peak hour power shortages. Just spin a heavy disk up with extra electricity in a low friction environment, and then siphon it off during peak hours. As a resident or a power company you could save money. It's not an option available right now, however.
If someone drops a fort on Will, he makes a reflex save.
Use excess power to pump water 300 ft uphill, then use the water to drive a turbine to power the A/C. From what I know of air conditioners, it would take a LOT of photovoltaics to drive one... I'd guess at least $20,000 worth.
"Freedom means freedom for everybody" -- Dick Cheney
As temperatures approach 120F and more this summer, I'm putting more aside for this project and at this point am not concerned with any but simple methods of using up 'excess' energy.
Don't most state regulatory bodies require that electrical utilities purchase any power that a customer generates?
Just feed your excess into the power grid, and let it offset the power you buy from the utility. Pay the difference on your lower utility bill.
Opinions on the Twiddler2 hand-held keyboard?
IANAEE (I am not an Electrical Engineer), so feel free to correct me where I stray from reality.. but here's some ideas:
1. Sell it back to the grid. Use the electrical power grid as a battery, drawing from it when you need and selling your power back when you don't. You can actually make some money this way, offsetting the cost of the solar panels.
2. Break the circuit when you don't need the cooling. (Any EEs want to comment on if this can damage the solar cells?) I believe this will just create a DC potential difference across the cells, and since the circuit is broken, there's no current flowing around to worry about storing.
Good luck.
Using your sig line to advertise for friends is lame.
What the world really needs is a cheap, non-bulky rechargable battery. It's the only thing that keeps solar power, wind power, electric cars, and a lot of other cool sustainable tech from happening. Conspiracy theories, anyone?
Rather than generating and then trying to store the power, have you considered selling it to your local utility? This would offset the cost of having to buy energy to run the air conditioner when it is required. Most of the time it won't be because, presumably, you'll need your air conditioner most when the sun is out. Perhaps I don't fully understand the question as it seems to me that you're over-engineering the problem.
Traditional air conditioning assumes cheap electricity, and plenty of peak capacity. (Ever try to start a compressor motor?)
You want to reduce you air conditioning need. Think awnings that reduce solar gain. Think reducing heat generation. Think insulation. Think how to be a bit more clever. There is a lot of work available on this aspect.
Once you do do some air conditioning, consider finding a cooler hot side for your heat pump. Something my wife wants us to look at for both heating and cooling is "geothermal", that is using the earth for the both hot side (in winter) and cold side (summer) of the heat pump. Also, if you are in a dry climate, consider if a little evaporative cooling might boost efficiency.
-kb
Solar panels will produce DC power. Your air conditioner will use AC power. You are going to need a DC to AC converter. You will also need a large bank of capacitors to maintain even voltages before you convert. It would be far easier to just get a premade solar setup and feed that directly onto your power grid.
Maybe instead of using solar energy to make electricity, then converting that electricity to mechanical compression, you could use an ammonia type refrigeration unit -- like the type you see in RV's that are powered by propane.
They use heat to separate ammonia+water, condense the ammonia, then use the evaporating ammonia for cooling as it is absorbed back into the water solution:
http://home.howstuffworks.com/refrigerator5.htm
Not sure if this would be any more efficient than solar cells + batteries, plus you'd either need a large quantity of ammonia to give you long periods of cooling even after the sun goes down, or you'd need a large thermal mass to store heat (or rather to remove heat and store "cool").
Cheap Solar Cooling Solution?
What the hell would you want to cool the sun for?
(... had to be said... *ducks*)
No sig
I don't think you're going to be able to get enough energy out of solar panels to run a compressor type air conditioner.
I'm sure you could just run a nice DC fan, maybe even with a temperature controller. There are many a model of solar Attic fans that can significantly cool a house in the summer.
I know they're inefficient, but how about a peltier device?
Use of foul language!
Why not just setup a Wind turbine and a 2way grid connection? A good (but large) wind turbine can generate up to 1MW of power.
With it, when its windy, you generate and use your own electricity, and sell off excess to the grid. Its quite exciting watching an electrical meter run backwards.
Of course, when its calm, the grid sells off electricity to you.
Either way, its a guaranteed supply of power for your house (AC included), and can really reduce your electrical bills.
Call your local electrical company about setting up a reverse grid hookup. Some will be more than pleased to set one up (likely for a cost), while others may advise otherwise. Be also sure that the hookup is done properly and legally. Elsewise, the electrical company will be extremely pissed off, and may resort to legal action.
Frink: Nice try floyd, but you were designed for scrubbing, and scrubbing is what you shall do.
So, you want to convert solar into low voltage electricity, and then convert the electricity into chemical or mechanical, and then convert that back into low voltage electrical, then convert that into 120 volt electrical, and then into a mechanical to run a heat pump to cool your house.
Maybe you should look for a DC air conditioner, or different cooling technologies. Or, maybe you should type "solar power air conditioner" into google.
Slashdot is jumping the shark. I'm just driving the boat.
In theory, you could find out what sort of material is used in the batteries' storage plates (such as nickel/cadmium or Nickel Metal Hydride), buy some of the elements, put it in an insulator, and charge it up with current. You'd have to find the exact right amounts. -- I don't know how to work out the details.
Center for Student Developed Education Policy
In other words, take the total square footage of the area you want to cool and divide it by 3. That's a rough estimate of the square footage of solar panel you'll need. (Of course, the math WILL change depending on your installation: more efficient panels, better sunlight, more efficient AC unit, etc). This estimate is a worst-case scenario, and I can easily see getting a factor of 5 or better.
As for excess energy... if you anticipate needing a LOT of cooling, one option may be to "store" some of that cool. Use the extra juice to run refrigeration units to chill tanks filled with brine or antifreeze solution. Help cool off/dehumidify your house by running this chilled solution through some radiator coils. (Add small fans for better results!) The pump and fans can also be powered from the "extra juice" if there is any.
The added benefit here is that you can use energy collected in early morning/late evening hours to help reduce cooling load during the really hot parts of the day, allowing you to get away with smaller AC units and less solar panels.
=Smidge=
Solar power is very expensive, and there are other things you can do to lower your cooling expenses.
Consider where I grew up in southern Alberta. In the winter temperatures dip frequently to -40. In the summer highs of 100oF are not uncommon. The same insulation that keeps the house warm in the winter keeps it cool in the summer. In fact very few people that I know of have air conditioning. Even in a hot climate, good insulation can knock your cooling bills way down.
Another thing to consider is geothermal heating and cooling. The idea is to pump heat into the ground in the summer, and then pump it back out in the winter (well, it's actually based on temperature exchanges). You can get an amazing amount of cooling in hot summer this way. You will be required to do some digging, though.
Either way, running a standard A/C unit off of solar power seems to be very expensive by itself. These other things I've mentioned could make it approach practicality.
RT-superconductors are the breakthrough technology that you're looking for. It's not happened yet (and may never).
Closed loops (circles) of superconducting wire are the best, almost 100% ideal electrical storage mechanism. More info here. There are already a few commercial products that make use of this technique - but they tend to be huge because of the liquid nitrogen cooling that's required.
The theory is as follows: Electromagnetically induce an electrical current to flow around a loop (circle). Because the electrical resistance is effectively zero, it will flow almost forever (estimates for some cryogenic superconductors are that the charge half-life is about 1000 years). The more magnetic induction you use on the system, the higher the system will be charged. It's an electric flywheel with no moving parts except electrons. To remove charge, use the electromagnet as a generator - in the exact same way you reverse an electric motor to remove charge from a flywheel.
If room-temperature superconducting ever becomes a reality, tiny, portable applications of this technology suddenly become possible. It will trigger another technological revolution. Anything that needs to store energy - transportation, electronics, space exploration - will suddenly find themselves with vastly more capable energy storage devices. Unfortunately it will also enable more dangerous weapons - amazingly powerful gauss guns will be possible.
You wont be on the producer side of the equation, but your net savings will be much MUCH higher by installing a geothermal system. They're cheaper to install, are pollutionless (well as compared to oil/gas burners), and provide central air and heat. Also... look at evaporative roof cooling systems if you have a flat roof. Are you well insulated? how about planting a tree or two on the south side of the house to provide some shade? Point being is that there are far more effective ways of lowering your energy bills than installing solar, though I do see the draw to producing your own power. Still, saving 1kw*hr of energy per day is better than producing 500w*hr each day.
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One myth about solar in most systems- you will NOT be the only one on your block w/ lights during an outage. The power grid is a two way street, and your power will flow right back out to the grid in most setups. You will have to install special equipment to disconnect you from the grid in these cases.
There are programs out there where you can finance geothermal heat pumps so you dont feel the pain upon installation of the system. most of the time, youre cost savings in your energy bill is greater than the loan, so youll actually have more money in your pocket (and a brand new heat system- increased resale value).
for more info:
http://www.nrel.gov/clean_energy/geoheatpu
For example, filtering out porn will reduce heat generation a lot.
Search for Solar Powered Ceiling Fans.
They're not (that) expensive, they run when the sun's out, when you need it most.
I've spent time in Africa and India, and everyone has really good ceiling fans, and it makes a heckuva difference. Some places, like banks and airports, are augmented by these neato wall-mounted oscillating fans.
There's a fellow in CA who has solar cells on his house. The power co buys back his excess power during the day, at the peak rate, and at night he uses power off the grid. His night usage is paid for by the difference between peak and evening rates. Check out homepower.com -> Home power magazine. There are lots of people out there who want to power their stuff in a safe way.
You might be lucky, and have access to lots of ground water. If so, you might be able to pump it through the system with much less power than a regular cooling system needs.
If you have a big enough installation and live in a place that is cold enough in winter, you can make your own Taylor slush pond/tank. For one of those, you spray brine in the air in winter and collect the runoff into a deep pond or tank, circulating it until spring or until it's almost frozen solid, and then circulate cold water from it all summer.
Does the power generated by the solar panels even balance against the power used to produce them ? Its probably still more enviroment friendly to just plug the fan into a wall socket.
People have known for thousands of years how to build buildings that stay pleasantly cool on hot days. So, if you want to do something environmentally friendly, design and build your house accordingly. A good architect and landscaper should be able to advise you.
There are also some things you can do after the building has been built, like planting trees, improving insulation, and putting reflective coatings on your windows. If you have lots of space in your yard, you can also use a bed of rocks together with some kind of ventilation system as heat storage, cooling your house during the day and warming it at night.
If that isn't enough and you just can't cope with the remaining heat, then you might as well do what everybody else is doing: install air conditioning and pay the power company. It seems doubtful that any kind of solar-energy drive air conditioner would, on balance, be more environmentally friendly than that anyway.
why not sell the extra power you're not using back to the grid?
Not really clear what you need/want the battery bank for. Unless you are completely off grid, just use the solar generated electricity when it is availiable to augment the grid power needed for cooling the home. There isn't really a good reason for trying to oversize the solar or buy batteries unless you expect to go off-grid.
If you ARE going off grid, (actually even if you are on grid) you will probably be much better off first reducing the cooling load in the home. External shading and/or low Solar Heat Gain (SHGC) window, automatic blinds, some more attic insulation, shade trees, and radiant barriers in the attic, will probably all be more cost-effective than solar electricity for cooling. Next buy the best possible air conditioner you can. 18 and 19 SEER aircooled units are availiable today, ground source heat pumps will also be efficient. If you are in a relatively dry climate, there are some single and two stage evaporative cooling options that are even more efficient.
Another option would be to implement some evaporative cooling on the condenser side of the air conditioner. A desuperheater on the air-conditioner can really help alot with the EER if the outside temperature is as high as you are thinking, and you can get hot water out of the system too if you want.
Once you have exhausted the above options, you might think about using solar power. Hopefully you will have cut the amount needed in half or better.
Don't store electricity, but rather chilled water. This can be stored quite inexpensively. There are quite cheap heat exchangers available surplus.
How humid is your environment? If it's a relatively low-humidity environment, why not use an evoporative cooling system? Basically, blow air through a box into which you spray a fine mist of water. As the water evaporates, it absorbs energy from the air, cooling it.
Your PV system then only has to run a fan.
Real Goods sells renewable energy sources, books on design and installation, and planning and installation services.
You could build a device that would supply your house with all the power the solars panels could provide. The panels wouldn't be able to supply your hole house so you will need that device to supply the rest from the normal grid.
Since your goal is to reduce your power consumption (this means eletrical bill) it will work even better than the solution with the batteries, since the panels will be supplying energy ALWAYS and not just only the batteries are charging. It doesn't matter if you are using the energy for the A/C or for your computer, you will save the same amount of money.
Good heavens, solar technology is mature and installers are standing by to set up a system for you. Photovoltaic panels today are completely capable of running from no load to full load without any special care, and you can purchase inverters that do not need batteries. Since you mentioned you are only interested in running an air conditioner during the day, go get a Sunny Boy(tm) 2.5KW inverter and panels to drive it. The panels will cost you about $15,000 to deliver that much power (and most house air conditioners run at around 2KW. If you have the system hooked up to the grid, in many states you will qualify for a rebate ranging from 30% to 50% of the cost of the system.
A less expensive alternative is to spend your money upgrading the insulation in your house, adding verandas to the south and west exposures.
If you're trying to store cold, do what they did 200 years ago: put ice inside something insulated. Back then they used barns with walls full of sawdust, but we can do a lot better today.
Time is Nature's way of keeping everything from happening at once... the bitch.
There are many ways to design a solar system, depending on application.
Yours is an ideal application: the load is directly proportional to the solar gain. So there is no need for storage because your cooling needs track the solar gain. Less sun, less cooling needed. There can be some lag time, depending insulation and thermal mass in the house but these things are best solved with insulation and thermal mass as your "storage".
For an air conditioner, use an evaporative cooler (many times more efficient than a conventional air-con, very little solar to run). If you live somewhere humid use an desiccant adsorption cycle evaporative cooler (search google -lots of work done on these for solar powered cooling).
And finally, the best "solar cooling" is no active cooling. Build or modify your house with appropriate insulation, thermal mass, shading, and architectural passive solar heating and cooling elements - and your house will stay cozy all year around with little active cooling required.
-TAH
This is a theoritical issue that isn't a problem in the real world for several reasons.
First: If you supply power, your neighbors are going to use it. Your equipment cannot supply the whole neighborhood, even the biggest will trip the mail breaker in your house (all your neighbors drawing from you is more power than your house can deal with), more likely you will trip a breaker on your equipment and not have power yourself.
Second, if you have equipment connected to the grid it cannot work without synchronizing frequencies with the grid. No grid = nothing to sync to. This shuts down a lot of systems.
Third, some equipment is built to detect this situation and shutdown anyway.
I'm not saying this isn't something to deal with. The risk is very low, but if I was a lineman I would be mad if someone relied only on the above, and not a positive lockout. (the third is good enough, the rest I wouldn't trust)
For a typical panel you will not have any trouble if you just leave it out in the sun open-circuited. However, if you parallel several of them and don't use anti-backflow diodes, you can dump the power of one or more back through the one with the lowest voltage (typically the hottest). This can lead to thermal runaway (voltage drops with temperature) and fire. Ergo, anti-backflow diodes are one of the most basic elements of a properly designed solar system using parallel panels.
Read Home Power and you'll know this too.
Time is Nature's way of keeping everything from happening at once... the bitch.
I have seen a number of articles on systems which used ammonia refrigerant, calcium chloride (ice melter - CHEAP!) as the absorbent, and the rest of the pressure system was standard sizes of steel pipe and fittings. The concentrator was a parabolic cylinder, which works very well for putting energy onto a target which is a ten foot long pipe. You might have some hassles getting the ammonia (you need anhydrous, not the weak solutions sold for cleannig) to charge the thing - too many people make methamphetamine from it.
Time is Nature's way of keeping everything from happening at once... the bitch.
Grid-intertie inverters are required to have anti-islanding systems which shut them off within a specified time if they lose the connection to the grid. If you have such an inverter, you won't have power during the grid outage but you won't fry linemen either (and the mfgr has a much bigger insurance policy than you do).
Time is Nature's way of keeping everything from happening at once... the bitch.
In terms of batteries... you only ever use batteries if you are off-grid or if the grid is really unreliable. If you are tied to the grid you do not usually use batteries... the Solar system goes through an inverter and powers the house, and any excess is fed back to the grid (running your meter backwards). The grid acts as the 'battery' in this case. If you are not producing enough to power your house, the remainder is fed to you from the grid. Grid-tie systems without batteries are the *simplest* and *cheapest* type of PV system you can buy, but you are still talking about $15-$20K for the system you see above. Systems with batteries cost a lot more (add another $5-$10K at least) plus you have maintainance requirements (Batteries wear out), and you need an ATS (Automatic Transfer Switch) which itself is expensive. On the otherhand, systems without batteries are nearly 100% maintinance free. Without batteries means that if the grid goes down, you go down too. Most people live in areas where the grid is reliable enough that there's no point doing battery storage. Also keep in mind that battery systems have much higher losses then grid-tie systems because you have a loss charging the battery and another one pulling energy out of the battery on top of the inverter losses.
Typical home AC systems eat 3kW while larger home systems eat 5kW (for homes, not apartments). Lets say you had an AC unit that eats 3kW while operating. A 2.5KW grid-tie system producing 16KwH/day would be able to run such a unit for 5 hours. As you can see, the PV system itself would not be able to power the AC unit alone, it would definitely need help from the grid, but if you only ran the AC for 5 hours the PV system would run your meter backwards the rest of the time and make up for it.
Five hours is not usually enough running time to really be able to cool a house unless you live in dessert conditions where it gets cold at night, in which case you really need to cool the house down at night so it stays cool enough so you don't have to turn on the AC until the afternoon (12-5p.m.)
So, generally speaking, trying to run an AC system with a PV (solar power) system is a bad investment. You could try running a smaller AC system but the sun generates something like a kilowatt of heat per square meter and it will easily overpower a small AC system if you do not have good insulation. Note, in particular, that if you do not have good wall insulation the sun is likely to overpower your AC during the afternoon when the sun is hitting the side of the house instead of the roof.
You would be far wiser to invest in passive technologies such as improved insulation and infra-red reflective shading. If water is cheap (or even if it isn't), a swamp cooler (rooftop evaporator) is often a great investment... it's cheap and it provides some cooling at a far lower cost then AC in electricity use. I've heard people mention GeoThermal, and it does work, but if GeoThermal is not put in when the house is actually built it can't take advantage of an under-the-house installation. Getting enough suds out o
Ammonia is widely used in industrial-scale compression refrigeration systems. It's a heck of a lot cheaper than fluorine/carbon compounds.
Time is Nature's way of keeping everything from happening at once... the bitch.
If you only need to keep something small below 80 F or so (like, a computer?), you can get really dumb-ass simple. Fit the comp for liquid cooling, use one small solar panel and a DC pump to push ground water through the cooling system. Your total power needs for this might be merely tens of watts unless your ground water lies a long way down or is really hot (don't try this in Yellowstone or Iceland).
If you're trying to keep people cool, you can still be elegant yet cheap. Lithium bromide is one such system; it doesn't cool much, but it has such a powerful love for water that it makes a superb dessicant. What you do is to evaporate water into the space to be cooled, then remove humidity by running the air past the LiBr solution. You regenerate the diluted LiBr solution by heating it to boil off some of the water and bring it back to full strength (solar heat works well here). Lather, rinse, repeat.
If you live in an area which is hot and dry rather than hot and humid, you can dispense with the LiBr and just evaporate water. This is called a "swamp cooler"; many places in the south-west are lousy with them.
Time is Nature's way of keeping everything from happening at once... the bitch.
...I will answer your questions.
handle the voltages of this setup WITHOUT the use of a battery bank?" What about the voltages makes it necessary to use a battery bank? Don't want one? Don't use one. Simple.
"I realize that the photovoltaic array will have to be of sufficient size to offer more power than will be consumed by peak load, causing excess power, that will need to be dealt with. Also, there will need to be some monitor so that if the available energy doesn't meet the minimum threshold, then the appliance is shut off (or the juice to the circuit is cut), and vice versa.
Excess power that needs to be dealt with? If you do not consume energy from a solar cell it does not 'build up' or 'force itself on your family pet'. You will need a voltage converter/regulator AND THAT'S ALL. This is not simple nor clever, it's obvious. The energy coming out of your solar cells is not compatible with the energy your air conditioner requires. The voltage will rise and fall, and depending on the load the current will also rise and fall.
A converter/regulator will take all that in stride and give you your 220 or 110VAC that the air conditioner requires. If the solar cells are capable of producing more than you need then the converter will simply not consume it. This is basic electricity.
If you don't believe me, try this simple experiment: Buy a solar cell from radio shack that's rated for, say, 5 watts. Hook a 1/4 watt resister across it that consumes only 1/4 watt at the cell's peak voltage. Place panel in sun. The panel is capable of generating 5 watts, but you are only consuming 1/4 watt. Notice how it doesn't explode? Resistor burning up? No? Good. When a solar cell has more energy to offer it raises its voltage. However there is a peak voltage which the cell cannot raise past. That voltage will not become greater and greater just because you aren't eating the energy.
The converter/regulator will change that energy, regardless of the voltage, into whatever format it's designed to output. In this case it needs to be 110 or 220 VAC.
I would recommend you set aside one small solar cell to determing how much light there is. Use it to switch a relay, for instance, that connects the air conditioner to the converter/regulator. If you buy a fancy converter/regulator then it may have features to detect energy output and turn the air conditioner on itself.
Lastly, be aware that in most cases buying a solar cell system is going to cost more than buying the energy from the power company. You can expect the cells to last for a good 5 years, then a poor 15 years, and in that time it's very unlikely that you would have spent more than a few thousand on electricity for the air conditioner. In this particular case it's a bad choice because the cells age whether you use them or not, and if you choose not to bank the energy then you are simply throwing away what is already shaping up to be a poor investment. At least get a converter/regulator that feeds power back to the electric company - use them as your battery bank.
-Adam
Try this. Direct refrigeration from the sun - and it doesn't even use salt water and ammonia.
If you just want cooling (er, you can also get heating with this) and you have the property, it's even easier. Dig a buncha ditches and lay some pipe. You combine these inlets with a decent solar chimney and you have a completely "passive" (ie no machine moving parts, no electricity needed) means of circulating 60 degree air throughout the house.
Oh, and here's a DIY solar ice maker - just for the heck of it.
Feel free to message me about this. Solar energy is something of an avocation of mine.
The way the locals deal with this is to live underground. The houses are basically carved out of the limestone with jack hammers. The temperature is cool throughout the summer and warm in the winter. So they say ...
Sumps work via evaporative efforts rather than refridgerants. here is 4 seconds of google "work"
Oh, and limiting areas of heat ingress - shades and canopies over windows that let the sun in.
You need way more power than is feasible with a solar array of any practical size. Use solar for powering your notebook computer and / or electronics, nice clean and easy.
If you want A/C, you need kilowatts of power. Ac is pretty dismal power wise.. it's inefficient to pump heat in the wrong direction. No way around that one. A medium sized windmill can easily supply 2-3kW of power you'd need for a nice A/C unit. You need to be in a location that lends itself to windmills, and you're probably going to need a battery bank too.
I've got a plan to move off grid, and AC isn't on it. Also, selling power back to the power company is more trouble than it's worth unless you have a lot of money. They don't pay much, and you need specialized equipment that costs many thousands of dollars. It's far more effective to dump the output of a windmill unrectified into a resistive heater for warming water for example if you want house heat.
What may work is an evaporative cooler using water.. I haven't played extensively with these systems but it might be an idea. Basically you'd have a radiator. Spray water on the outside of the radiator, that evaporates, taking energy out of the radiator - cooling the liquid inside. You can then pump this back into the area you want to cool. More efficient, but needs water.
..don't panic
In point of fact, Exxon actually spent a lot of money, back in the 80s, trying to develop a cheap rechargable battery. They figured that when the gas ran out, people would switch to electric cars, and they'd go to an Exxon station whenver they needed to swap out their batteries. Alas, the gas never ran out...
Someone connected a standard $500 panel to a car battery, power inverter, and wall mount air conditioner.
It took an entire day of charging to provide enough power to run the AC for 2 hours.
There was photos but I can't find the site anymore.
When I used to live near lake anna (middle-of-nowhere, yes fredericksburg IS nowhere except to civil war buffs), I took a tour once of VA power's site (nuclear plant).
They had there a large field of solar panels, that was _only_ enough to power a single operations building (not a mission critical one, I in fact believe it was essentially only used for tours, PR, etc), so to power an AC unit, I suspect you may well need an unmanageably large number of solar cells, since AC alone accounts for at least 20-40% of my usual electric bill (in the summer)...
Just my experience, ymmv, ianl, ioaaa (insert other acronym as appropriate)
-- (appended to the end of comments you post, 120 chars)
I saw something like a solar refrigerator on German TV a year or so ago. Here a link:
m
http://www.eg-solar.de/english/solar_cooling.ht
Cheers
Walt Dismal suggests:
One solution is to not use electricity.
OK so far.
Build a solar-powered steam engine and use it to run a Carnot cycle in reverse (heat pump) during the day. All mechanical, no electricity. Cheaper than solar cells plus batteries plus charger/inverter.
While we're at it, we can make the air conditioner even more efficient by making it out of point masses and assuming no friction.
[Hint: The Carnot cycle is a theoretical model from the thermodynamics unit in physics class, it's not a real heat pump to cool anything. It makes some assumptions (eg. a fully reversable process, no entropy increase) that we don't know how to engineer. It's the oversimplified ideal heat pump, not a real one.]
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Open mind, insert foot.
As many others have already said, your best bang for the buck is to reduce the amount of cooling you need - solar film on the windows, awnings, trees to block the sun.
Next, get the cool when you can - you did not indicate if you are in a dry or wet climate, but if it is desert like, then open the house up at night and get a whole-house attic fan. Pull in the cold at night, cold-soak the house, and the button up in the morning.
If you are in a desert climate, get a swamp cooler (evaporative cooler). This takes a LOT LESS power than a compressor based aircon unit, and in a dry climate will produce VERY COLD air (IIRC in a 20% humidity environment a swamp cooler will take 110 degree air down to 70 degrees F).
OK, but that is not geeky enough - you want something that will get your personal web site slashdotted. OK, how about this: build an old-style ammonia cooling unit and drive it with a solar concentrator. The ammonia cycle system uses heat to pump heat (it is what is used in refridgerators in RVs). However, the payback period will be measured in decades, so do the other things first to really save money.
www.eFax.com are spammers
For active, use fans to circulate cooler air. Use an underground thermal sink to reduce the load on the A/C unit. (Can also be used to heat in winter).
Look at smaller, room-based A/C units designed for mobile homes (not the LPG powered ones).
I'm not that conservationally-minded, do some Googleing. In 30 seconds I found this page.
My brother cooled part of his house in N. Florida by burying a length of about 500' of small PVC pipe in his back yard about 18"-24" down and pumping water through it. That water then went through a radiator in the house with a fan behind it. Not dramatic cooling, but signficant. The pump and the fan are well within solar power capabilities.
I think you are running in the wrong direction. As someone else already posted, running an air conditioner is horrifically energy inefficient. Consider the alternative that is commonly using in Lousiana or other places, a swamp cooler.
A swamp cooler is typically a large tank on the roof of a house with a fan sucking air out of the house, across the tank, cooling it, and then forcing the chilled air back into the house.
Low power usage, coolish air.
I've been looking for good confirmation on these statistics, too. I have been reading recently that we're well past break-even on the energy used for production, but I don't have any numbers from a source I'd believe 100%.
Anybody got any good numbers from a reputable, independent (ie, not a solar panel company or an oil company...) source?
As a starter, here's a page with a number of stats, but being from a site called "ecotopia" makes the engineer-cynic in me want to take it with a grain of salt. They are, however, citing other studies. The more facts, the merrier, so if you've got any links, post.
The short version is that amorphous (thin-film) panels yield a 400%-2000% payoff on energy investment. That range is worst-case to best-case lifetime for the panels. Thin-film is the way to go anyway, as it's around $15/sq. foot instead of the $60/sq. foot for the crystalline panels. Sure, crystalline is twice as efficient, but thin-film is cheap enough to use as siding on your house, and you'll make up the difference in area. Now, as to convincing your significant other that shiny purple-blue panels are the way to clad your house is the tough part.
Look at it this way-- based on the energy costs, even if the return was only 110%, it would be worth doing. Is there any other way to turn a barrel of oil into 1.1 barrels of oil?
It's odd that you're worried about the cost of batteries but not of the panels. As a point of reference a recent issue of home power, HomePower.com shows 3 100W panels for $1680 while a 105AH battery is only $400.
The solar panels are going to be easily thousands of dollars. By spending some money on batteries you'll be able to do away with a bunch of extra panels which is going to save more in the long run and will allow you to cool in the evening or on a cloudy day to boot. Still the cheapest is going to be all the tricks you can use to reduce the need for AC like shade, swamp coolers and such.
Build a sufficiently large photo panel, so that your house fits within it's shadow to reduce heat. No need to include costly batteries, then. Maybe you can plug an impressive tesla coil on top of panel to route an excessive power away.
There you are, staring at me again.
Forget trying to run a regular AC unit, unless you want to spend BIG BUCKS on the batteries and solar panels - and you will spend a lot of money on them (though prices have come down a lot). If you ever want to go solar electric, and you can't outright pay for the panels, you might consider rolling them into your home loan (if you get one), or as part of the purchase of your house (think of it as buying the electricity for you homes needs for 20 years up front - then the cost is VERY cheap).
Really, though, you need to work with nature, not against it. So, design, plan, and build your house accordingly.
Choose the right type of house - for most enviroments, a dome-style house is going to be the absolutely most efficient kind of house around. Use 40 foot lengths of rebar set and wired/welded into a 20 or 30 foot diameter concrete "foundation" ring - rebar around that, to make a dome of rebar, cover with wire mesh - dip burlap sacks in concrete and cover the outside and inside - or use shotcrete. Spray with foam insulation, or cover with dirt? Build walls a few feet thick, and you had EXCELLENT insulation (earthen mass).
I like the idea of burying PVC pipe in the ground - great idea. Also, look into the idea of a "solar cooling tower". This is basically two tall towers - one painted black, the other painted white. The black one absorbs heat, and the air inside rises, while the white one stays cooler. Inside the white one, you water mist or evap cool air, so it falls - place on opposite sides of your house, and let the cycle flow the air through! Heck, there has even been a cpu cooler or two built using this principle (shower cooling)!!!
Or, look into how the Romans use to cool their places: Dig a large, deep trench (several hundred feet long, 15-20 feet deep), put a pipe at the bottom, and run air through that - or, bury your house! I have also heard of a "heat pump" whereby in the summertime, hot air in the house was heat-exchanged (just like an AC unit) to a large hole in the ground filled with rock or steel, to store the excess heat in the house in the rock and steel during the summer - when winter came, the reverse was done, to pull the summer heat back out of the rocks/steel. Just keep in mind that you don't have to dig very far down until the earth temperature stabilizes - that is how you do it.
Another thing: in northern New Mexico, there is an old pueblo built by the Acoma indian tribe, where the apartments are passed down the maternal side - anyhow, they are built of adobe, with walls several feet thick. I was there in August, 100 degree temps outside, felt A/C'd on the inside - but there was NO A/C UP THERE - they had to truck in propane and water. Keep in mind "earth mass".
There are other things to keep in mind - with proper orientation, you can line your house up (or the windows), so that maximum sun shines in the wintertime into a greenhouse (south exposure), but with the right angling of the windows, less in the summer (due to the angle of the earth and sun), to help keep the house cool.
Another thing to think about is keeping the coolness in during the day, and letting it in at night - think insulation over all of the windows (there is a system that uses styrofoam beads to fill/evacuavate a dual pane window system with a powerful vacuum system to insulate a solar house).
Also, remember that there are propane powered refrigerators, which use heat to remove heat (sounds counterintuitive, but once you understand refrigeration systems, it isn't) - so, replace the propane flame with a solar concentrator! There are solar refrigerators that do this (or a similar system using solar water heated panels) - so it should be possible to do the same with an A/C unit of sorts.
It takes a lot of creativity to live off-the-grid, and more so to cool a home. But with proper building techniques, coupled with a knowledge of both past and current cooling systems - you can do so very comfortably...
Reason is the Path to God - Anon
Hello,
I used to be on a Solar Car team back back at University. I'm a mech. eng so bear with my limited understanding.
You need what is called a (or several) power point tracker. This creates a "dummy" load of your solar panel to bring the voltage down (and the intensity up) so that you get the maximum power. We used AERL power point trackers. We decided to have 6 sections on our panel because of the shape of the car. It's probably not an issue for you.
Now, you still need a battery pack to regulate your voltage (should be about 120V). The rule of thumb however is to use the power from the sun right away as you will lose almost half of it in the charging/draining process (depending on your batteries of course).
Since you need the power when the sun shines, I would spend the money on the solar pannels and get cheapy batteries whose purpose is being a reference voltage (and not a reserve).
My Karma is so low that even my own postings are beyond my current threshold
First, obtain a solar array the size of the state of Rhode Island. Then, wire it up to an industrial power inverter. Plug in your air conditioner, and you're ready for a lifetime of free climate control.
Re: Your sig
I don't believe the point of moderating is the determination of truth.
Moderation has to do with encouraging civilized discourse.
The discussion itself determines truth, insofar as the participants are able to comprehend it.
My sig, on the other hand, is strictly offensive.
Any preoccupation with ideas of what is right or wrong in conduct shows an arrested intellectual development. (Wilde)
You just run the people thru a juicer and feed them to the bacteria.
Any preoccupation with ideas of what is right or wrong in conduct shows an arrested intellectual development. (Wilde)
I did mention dessicant systems, nearly two days before your post.
Time is Nature's way of keeping everything from happening at once... the bitch.
Drape the object to be cooled in hessian. Set up a water drip system to keep the hessian damp. Evaporation (powered by the sun's energy) will cool things down. Solar power does not have to be electrical!
Wow...you need an advanced solar array system set up just for cooling your CPU? What do you run? AMD or something?
There are a huge number of yeast infections in this county. Probably because we're downriver from the bread factory.
I remember doing some calculation back in school - if you can manage to set up a hybrid system (wind and solar together), it's much more efficient. Go off of solar in the day time, and wind in the night time. It's as close to constant generation from natural sources as you're going to get.
There are a huge number of yeast infections in this county. Probably because we're downriver from the bread factory.
Some people believe we're at Peak Oil now, and the crash will hit us in the next 3-8 years.
If we are at the peak, then the price of oil will continue to rise, as will food prices, the prices of anything made with the use of electricity. Life as we know it will dramatically change.
In my worst case scenario, I foresee a global conflict with no holds barred, including the use of WMDs (Nuclear and Biological) by every country in attempts to seize the remaining valuable oil supplies. World War III.
Of course, it won't be enough, and after further damaging our already fragile planet, we'll be at a tech level roughly equivalent to the mid 1700's, but worse off, as we've largely forgotten how to do things for ourselve to ensure survival. Do you know how to grow enough food to last a year? Make clothes from raw cotton or wool? Build a shelter? Make a fire? I know I don't have much of a clue about these things, and they are just the basics to survive. Food, shelter, warmth. I think we'll come to appreciate them..
Further problems: diseases running rampant, no emergency services of any kind available. Looting, riots, fires raging through cities. Billions dead or dying (it's estimated the die-off will reduce the global population to around 500 million). Anarchy. People killing each other to get their hands on food.
*sigh* I hope things turn out better than this, but with people like Bush in charge of the US (let's hope he is defeated and the new president of the USA is better), I see no hope for humanity.
Important info:
http://www.lifeaftertheoilcrash.net
http://dieoff.org/synopsis.htm
http://www.peakoil.net