PDA

View Full Version : OT:Solar power system questions



wierdscience
09-08-2007, 12:35 AM
I'm planning a new shop building for my woodworking hobby/business and one of the things I am paying out is the electrical system.

Down south we have not much wind,but lots of sun so I am thinking about solar to at least run my lights.What I have in mind is a split electrical system.Basicaly two circuit breaker panels,one main for all the heavy current loads and one sub panel for all the lighting loads.The main will feed off the grid as normal and the sub panel can be fed either off the grid or off the solar system as need be.

I figure I can use one of the power monitor outputs on the inverter to switch between grid or solar as need be all that is fairly simple.

What I am having a time with is finding reliable information on designing the solar componet.What I have found on the net so far is conflicting information about how much panel is needed to provide x amount of power y amount of the time.

Do I match the panel wattage total to the total wattage of the draw and size the storage capacity for a quick recovery.Or do I reduce the panel wattage total by a factor and increase the storage capacity?

I am assuming there is a point where the cost/benifit equation comes into play at some form of balance.Do I spend more on panels or more on storage,that's the part that is confusning me.

Evan
09-08-2007, 12:54 AM
The answer of course is "That depends". It depends on the average hours of sunshine you have in the poorest month you want to use solar. It depends on how much you are willing to depend on grid power. Your cost per watt for solar must be factored against the projected cost per watt of the grid.

Another thing to consider is if you intend to use compact fluorescent bulbs you need to determine what the power factor will be on the inverter you intend to use. If it isn't a pure sine wave inverter the power factor will differ and may require you to size up on the inverter. Even if it is sine wave you will have to pay close attention to the power factor of the lighting load. You can't just add up the label watts on non-resistive loads.

It also depends on what type of batteries you use and don't forget to factor in a disposal fee even if it doesn't exist now. It probably will when they need to be replaced. 5 to 10% of the capital cost would be a start. I bought a lead acid battery the other day for $26. Problem is that after taxes and the eco fee it cost $40.

It also depends on what type of panels you use. Not all panels are the same. They fall into three main types: Amorphous silicon, polycrystalline silicon and mono crystalline silicon with the cost and efficiency going up in that order. They have a life of about 20 years since putting a solar panel in the sun slowly destroys it. :rolleyes:

Consider the hail resistance of the panels. I am pretty sure you get hail down there. One good hailstorm could take out the entire lot.

That's just a few things for now. There are more.

NAMPeters
09-08-2007, 01:05 AM
Why not just use sky lights?

dp
09-08-2007, 01:10 AM
Why not just use sky lights?

They work only during daylight hours.

tattoomike68
09-08-2007, 01:29 AM
This is the future, sterling engines that make good clean power.

http://www.stirlingenergy.com/solar_overview.htm

http://www.stirlingenergy.com/photos/photo/SES1784x1788.jpg?type=allsolar&imageID=11

wierdscience
09-08-2007, 01:31 AM
They work only during daylight hours.

Skylights would be an option during the day,but we see three to four months of 90+heat and 90+ humidity.Skylights make for an instant greenhouse,great for tomatos,not so good to work in.

Some people here put them in the tops of the side walls which works for heat,but it makes the building vulnerable to hurricanes.My intention is to build a shop that will handle 170mph winds to avoid buying wind insurance which is something only Bill Gates can afford now.

tattoomike68
09-08-2007, 01:34 AM
here is a good video.

http://www.youtube.com/watch?v=kYKOjnCwmG8&NR=1

wierdscience
09-08-2007, 01:53 AM
The answer of course is "That depends". It depends on the average hours of sunshine you have in the poorest month you want to use solar. It depends on how much you are willing to depend on grid power. Your cost per watt for solar must be factored against the projected cost per watt of the grid.

Another thing to consider is if you intend to use compact fluorescent bulbs you need to determine what the power factor will be on the inverter you intend to use. If it isn't a pure sine wave inverter the power factor will differ and may require you to size up on the inverter. Even if it is sine wave you will have to pay close attention to the power factor of the lighting load. You can't just add up the label watts on non-resistive loads.

It also depends on what type of batteries you use and don't forget to factor in a disposal fee even if it doesn't exist now. It probably will when they need to be replaced. 5 to 10% of the capital cost would be a start. I bought a lead acid battery the other day for $26. Problem is that after taxes and the eco fee it cost $40.

It also depends on what type of panels you use. Not all panels are the same. They fall into three main types: Amorphous silicon, polycrystalline silicon and mono crystalline silicon with the cost and efficiency going up in that order. They have a life of about 20 years since putting a solar panel in the sun slowly destroys it. :rolleyes:

Consider the hail resistance of the panels. I am pretty sure you get hail down there. One good hailstorm could take out the entire lot.

That's just a few things for now. There are more.

Yup there is a lot to it,a lot of things to consider.The battery situation looks to remain stable here for many years yet,the core programs work too good to scrap and the state has said so.Old batteries are still worth money $5-10 each so they don't end up in landfills or the local creek.Plus I get a %50 discount on Exide brand so that's working in my favor.

Hail,we do get it,but it's very rare and very small,I remember 2 times in the past 10 years,but used commercial plate glass is easy enough to get and would easily handle the hail we get.

Powerfactor,that's where it gets nebulous to say the least.I don't plan on using CF bulbs,MH low bay fixtures for primary and incandecent for task are whats in the plan.The humidity just kills CF here,you can figure on ballasts and bulb holders every few years.

My main goal if it is feasible for the long run is to offset some of my grid demand so maybe I can afford some AC to at least knock the humidity down in the summer if not some actual cooling,the older I get the less I can stand in the way of heat.I plan the insulate the hell out of the building and reflect as much heat as possible.

The lighting level I want should require around 1800watts to run full bore.There is a good possiblity that I will have 3~ 220vac service,but that will mean either a demand meter or a higher rate take my pick.1400 watts @ 110v continous draw isn't insignificant.

dp
09-08-2007, 02:00 AM
Skylights would be an option during the day,but we see three to four months of 90+heat and 90+ humidity.Skylights make for an instant greenhouse,great for tomatos,not so good to work in.

Some people here put them in the tops of the side walls which works for heat,but it makes the building vulnerable to hurricanes.My intention is to build a shop that will handle 170mph winds to avoid buying wind insurance which is something only Bill Gates can afford now.

Heat traps (storage) would be much more valuable than skylights at least in this part of the world. In fact here in the Pacific Northwest where we have 25 hours of night time per day and maybe two minutes of daylight between rain squalls, it is common to have a cistern under the main building that is solar heated. Thousands of gallons of water is a good energy sink. This collected heat is used to warm the house and pre-heat water coming into the water heater, as an example. Other people might call them a swimming pool but we really know they're cisterns, eh. The savings can be used to run a lathe or a video game - your call :)

In the near eastern, almost central part of the state it is very windy and wind mills are especially useful for creating augmented energy sources for such purposes as charging batteries for electrified fences to keep your bbq stock from wandering, and for providing outdoor lighting power to confuse mosquitos. We have enough excess power from wind that we could restore the ozone layer if everyone would install a compact wind-powered ozone generator. If we exported our excess ozone to China it could even create a balance in trade. Sure beats hustling carbon credits so you can use that Lear jet on the weekends.

But Puget Sound is an energy parasite because of the endless drizzle and year round fall-like weather. Not enough sunlight and wind to light a candle, here. Most machinists here have to use treadle powered shapers, mills, and lathes, in fact, and that assumes any two pieces of metal in these machines are not rusted tight to one another.

wierdscience
09-08-2007, 02:09 AM
Heat traps (storage) would be much more valuable than skylights at least in this part of the world. In fact here in the Pacific Northwest where we have 25 hours of night time per day and maybe two minutes of daylight between rain squalls, it is common to have a cistern under the main building that is solar heated. Thousands of gallons of water is a good energy sink. This collected heat is used to warm the house and pre-heat water coming into the water heater, as an example. Other people might call them a swimming pool but we really know they're cisterns, eh. The savings can be used to run a lathe or a video game - your call :)

In the near eastern, almost central part of the state it is very windy and wind mills are especially useful for creating augmented energy sources for such purposes as charging batteries for electrified fences to keep your bbq stock from wandering, and for providing outdoor lighting power to confuse mosquitos. We have enough excess power from wind that we could restore the ozone layer if everyone would install a compact wind-powered ozone generator. If we exported our excess ozone to China it could even create a balance in trade. Sure beats hustling carbon credits so you can use that Lear jet on the weekends.

But Puget Sound is an energy parasite because of the endless drizzle and year round fall-like weather. Not enough sunlight and wind to light a candle, here. Most machinists here have to use treadle powered shapers, mills, and lathes, in fact, and that assumes any two pieces of metal in these machines are not rusted tight to one another.

Hmmm..I can see that a treddle powered 36x8" wood planer:D

Seriously though,hot water is a snap here,cool water is what's in demand right now.Roundtoit #24,125 is to do as my nieghbor did on his swimming pool heater.He had his driveway blacktopped,but before he did he laid in a 500' coil of poly tubing under it.It works even on a 30* day so long as there is sunlight.The hot water heater in my house could just disappear.

Not that I want to save the planet,I just want to save some of my money from the nutty granola crowd aka "Insane AL"

Joel
09-08-2007, 02:44 AM
The hot water heater in my house could just disappear.

Heck, I don't even have a hot water heater. The cold water heater, I would miss. :D

Evan
09-08-2007, 03:34 AM
Darin,

Instead of skylights look into sun tunnels. They cost a bit more but the payback is fast and they don't transmit the heat efficiently, just the light. They can even act as task lighting. They will pay back a heck of a lot faster than solar electric and are zero maintenance. They also don't compromise the structural integrity.

Here are some links:

http://www.ecotun.com/en/

http://www.solatube.com/

http://www.veluxusa.com/products/sunTunnels/

Your Old Dog
09-08-2007, 09:36 AM
I'm facing this issue with my travel trailer right now.

In my research I've found much debate on the old or new technology panels. I hear the old panels have more to offer this kind of service.

They produce better on cloudy days. Will even produce under street lights.
They are cheaper.
Don't have to be aimed at the sun constantly for rated output.
More durable.
Can be officiant mounted flat on the trailer roof.The new style will produce more power but only when pointed directly at the sun. The old style degrade faster when new but if you check, you'll find out the fudge factor has been built into them. When they degrade, they will be left at specs. My trailer won't draw as much as your shop so I'll be able to watch a Sony 26" HDTV on Satellite! (this is the boomer new style of camping and not the old style younger kids do?) I'll have a charge controller to save my dual deep cycle batteries and an inverter to power the 130 watt TV.

If you do this, do it to stop the carnage that is being heaped on Mother Earth by evil mankind and not to realize any savings. :D (Bear in mind that one good belch from a volcano can ruin all your efforts!) By the time you are done with hardware you'll be lucky to break even. Completely built home made windmills are cheaper to accomplish but of course require wind that you don't have!

I have a kitchen porch that will one day be windowed in for Fall, Winter and Spring. The plan is to put slate tile floor to hold some of the heat in collected by the sun when the trees have shed their leaves in autumn. Should make it a comfortable place to sit and grow old.

J Tiers
09-08-2007, 10:58 AM
There are a number of considerations.

The first thing is to characterize the load. How many watt-hours per day will you be using? A 100W load for 5 hours is a 500 watt-hour load.

You can then grossly size the battery pack to provide that power for the number of days without sun that you want. For instance you might select 3 days backup. Set that thought aside for the moment.

Figure the battery pack at 10 volts for a 12V system and losses will be roughly compensated. Then your 100W load will pull about 10 A from a 12V battery. (5A from a 24V battery)

So 500 watt-hours is 50 ampere-hours at the assumed 10V.

To keep up the system, you have to provide about 1.2 times that power (allowing for battery inefficiency). Therefore you need to provide about 60 ampere hours per day to avoid a steady discharge.

Providing that will require about a 10A charge rate for 6 hours per day, which just avoids a battery drain. That 10A charge rate will take a bit over 1 square meter of cells of the usual type.

if you cannot get 6 hours of sun per day, hang it up, and stay on-grid.

Since we figured that you might need a battery to provide 3 days backup, you would need to provide a battery that can supply 150 ampere hours without being drained lower than about 25% charge remaining. Therefore you need a battery of about 200 ampere hours. Common T105s are 220 ampere hours approx.

Now, to do a good job of CHARGING, you must supply the daily usage PLUS a reasonable net re-charge rate. Leaving the battery "down" too long allows "sulphation", which reduces capacity.

A minimum rate of recharge is probably a "C/20 rate" (not at all a fast recharge, it would take about 24 hours, or 4 days sun) . Since "C" is 200 ampere hours, a "C/20" rate is 200/20, or an ADDITIONAL 10 A OVER the daily recharge rate.

At about 10A per square meter of cells, you need about 2 square meters of cells, and a 200 AH battery, with suitable charge controller.

Batteries should be "real" deep cycle, such as Trojan T105 "mileage master" golf cart batteries at 6V per battery. "Marine deep cycle" are not very good, and will cost almost as much but fail much faster. "starting" type batteries are pretty hopeless if you drain the battery as much as 50% more than a couple times.

My T-105 setup is more than 12 years old and still going. Same with others I know.


The comments by YOD are correct.

OLD PV cells will produce MORE in bad conditions, but less in perfect conditions. I had a set of old cells originally from the Carrizo plant, about 48" x 48" of cells. They produced 5A in the sun, and 2.5A on cloudy days, and were a solid brown color. A tree smashed them last year, after about 30 years total service.

The NEW setup is about 15" x 48", and produces nearly 5A in bright sun. On a cloudy day it drops to 1 A. It is merely a matter of area. the old cells were less efficient, and needed more area. But they collected more energy due to that, and cloudy days still produced alright. The difference in area is about the difference in current with the new ones vs the old ones.

AZSORT
09-08-2007, 06:29 PM
The only time to even consider using a battery tied solar system is if you are in an off-grid situation. The batteries are still the biggest problem - being expensive maintanence headache, safety and reliability issue, and significantly hurt the system efficiency. The way to go anymore (as long as you are on the grid) is a grid-tie inverter that can track the max power point of your panels and extract every precious watt out of them. You won't need a 2nd service panel, in fact most of the new inverters have integrated in the junction boxes etc. They use the solar panels strung together in series to produce several hundred volts which minimizes the wire losses and cost. Many states and/or utilities now have incentive programs that rebate you a big chunk of the total installed cost. Here in Arizona, it is $3 per watt of panels which is a 3rd to 1/2 the system cost. The new inverters are all designed to be grid friendly and the utilities usually only require an in-plain-sight disconnect box and some red tape to tie in. This still doesn't make the payback of a system much better than 10 years, but over the 25 year expected life of a system, the payback is generally 2 to 3 times its up front cost. The biggest factor is what your utility rates are. 12 cents/kWHr or less makes it real tough to justify solar. Places like California where they have graduated rates and sizable users get up above 30 cents/kWHr they make lots of sense. Grid-tie systems are virtually maintanence free, no hassle, the most efficient and cost effective way to go. Invest the money on panels, not spend it on batteries.
Email me if your interested in a quote, I became a dealer last year just to get myself better prices.

Greg C.

chief
09-08-2007, 07:43 PM
Are you worried about return on investment? If you can't get the system for a buck a watt you'll never get a reasonable payback. Evan is correct about the load etc. A much cheaper alternative would be to install CFLs and Super T8 light fixtures and high efficiency motors on your equipment. You have to decide on what you want save money or self-sufficency. Remember a battery rack isn't maintenance free and should ideally be contained in a seperate dedicated building.
I recently did a cost analysis for a 5kw system, my numbers were in the 70-80 range, the contractor can back with a 100k quote.

J Tiers
09-08-2007, 10:55 PM
The only time to even consider using a battery tied solar system is if you are in an off-grid situation. The batteries are still the biggest problem - being expensive maintanence headache, safety and reliability issue, and significantly hurt the system efficiency. The way to go anymore (as long as you are on the grid) is a grid-tie inverter that can track the max power point of your panels and extract every precious watt out of them.


Most ANY decent charge controller these days will do max power point tracking, that is NOT reserved for grid tie.

Batteries are hardly an expensive maintenance item, and they DO provide backup power thru the inverter, which you cannot get from a grid-tie-only. Most grid tie units shut down if the grid goes out, that is an IEEE requirement to prevent "islanding". That type will not provide local power unless you can manually over-ride, and naturally would require batteries to provide power off-solar-peak or at night. I'd never consider such a system for a moment.

I have had the same T105 batteries in the system for over 12 years, and they still have sufficient capacity to be quite usable, somewhere around 80 to 90 percent of original capacity, maybe more. I just feed them some distilled water as needed.

Properly located and fused, they are not a safety hazard either.

The most expensive maintenance item in my system has been the panels. They had to be replaced after the tree fell on them (from the North), and naturally were not insured.

wierdscience
09-09-2007, 12:23 AM
I've looked into light tubes before,they look good for daytime light,but most of my shop time will be at night.

If I go with a two panel system all it will cost extra is the cost of a 6 circut panel and an extra ground rod since I do my own wiring.Even if I don't go with solar now it will be ready to plug and play if something happens later like super cheap panels.

Even though I will be on the grid,things like hurricanes happen and it would be nice to have a backup for my refrigerator and maybe a fan or two.Plenty of sunlight after a hurricane,but little fuel for generators.

What intriques me is a setup a friend has at his fishing camp.It's off grid and generators make noise so he bought 2-45 watt Chinese solar panels,a 3500 watt inverter and a 1,000amp tractor battery.With that setup he can run all the lights he wants,and a small portable cooler all weekend.He has been doing this once or twice a month for three years and has yet to need a new battery.
Now I realise that isn't going to happen that easy for me since he has a long recovery time availible between fishing trips,but it still looks promising with a bit more infrastructure.

Besides HF has the panels on sale right now:D

Too_Many_Tools
09-09-2007, 12:35 AM
How good are the HF panels?

TMT

wierdscience
09-09-2007, 01:22 AM
How good are the HF panels?

TMT

Dunno,they are similar to the ones Buddy bought,same type cells as I recall.His are just sitting on the south slope of the camp roof with a 3/16" plexiglass shield over top.Absolutly nothing fancy.

There on sale $199 including the controller not counting a 15% one item coupon they have running.

Your Old Dog
09-09-2007, 09:52 AM
Got Rhode Island Red cartoon character in my head.......

"I say I say come on men, answer the booooys question! I say I say the sale ain't gonna last forever you know!"

My trailer has a round vaulted roof and these particular units (3seperate one to a panel) would lay nice on the roof.

Evan
09-09-2007, 11:50 AM
Ok. Simple answer is that solar electric still can't compete with grid prices. For the times the grid is down you are better off to have a diesel backup. Diesel fuel keeps well so availability shouldn't be a problem if you plan ahead.

J Tiers
09-09-2007, 11:55 AM
When the grid is down, and you run out of fuel, the cost per kilowatt hour is just not very important........

Evan
09-09-2007, 12:11 PM
That's where the planning part comes in.

J Tiers
09-09-2007, 12:34 PM
That's where the planning part comes in.

Plan for a week, power will be out 9 days..... Plan for two weeks, power will be out 3.

Plan for 6 months...... Naw, forget it.............

How long has power been out in parts of New Orleans now? How long was it out in Mississippi?

Power was out in St Louis for 10 days a year ago July, and out for 6 last December. It would be very reasonable here to plan for 3 or 4 days....... (at least it WAS reasonable)

Also, there are a lot more things to go wrong with a diesel plant, or gasoline plant, than there are with cells and batteries, 12V lamps, Peltier coolers, etc. Those things are the fallback if the inverters croak.

The fallback with a diesel genset only is the Red Cross shelter..... or doing without.

jdunmyer
09-10-2007, 09:18 PM
Here's a link to an article I wrote several years ago on the subject of solar power for RVs: http://www.fiberglassrv.com/solar.html

Since the article was written, we've changed trailers and now use an MPPT controller and 2 golf cart batteries. Most of the rest still applies.

As others have said, if your object is to save money by using solar power, you should lay down until the temptation passes: it ain't gonna happen. If you want backup, get a generator, fueled either by Diesel or propane; Diesel fuel keeps pretty well, and propane will keep forever. You should be able to store enough fuel for at least several days, and by then you should be able to get to some place to get more. Be sure to exercise your generator regularly, or it won't work when you need it. My genset is shown here:
http://www.oldengine.org/members/jdunmyer/genset/

Rigid conservation measures will save much more $$$ than any solar system.

My comments do not apply if you're off-grid.

wierdscience
09-10-2007, 10:58 PM
Got Rhode Island Red cartoon character in my head.......

"I say I say come on men, answer the booooys question! I say I say the sale ain't gonna last forever you know!"

My trailer has a round vaulted roof and these particular units (3seperate one to a panel) would lay nice on the roof.

He was a HSM you know,Foghorn Leghorn,ever see the one where he is chasing the dog around the barnyard when he stops and chops down a tree drags it into the shop and spins a ball bat out of it to whack the dog?:D

wierdscience
09-10-2007, 11:19 PM
I'm not looking for free electricity,pay me now pay me later is still in effect.If I could shave a few dollars off my monthly bill it would be nice.Using the system after a storm for running a few lights or fans or for that matter just saving a freezer of food would be nicer.In that case the cost of a small home built system might payback in a couple weeks.

I rode out Katrina,power was off two weeks here,1-1/2 in town and then on again off again for about 4 months later.A 5,000 watt Briggs generator drank 7 gallons of gas in about 8-9hrs run time,gas when you could find it was $5+.All that generator did was run lights a couple hours after dark and a couple fans so we could sleep,it sat idle during the day.$35/day especially when gas is scarce and you have basicaly no income because work has shutdown is difficult to manage.In two weeks of run time $500 goes down the toilet not counting the cost of the generator in the first place.From what I see a small home system could be assembled for less than $2,000.Diffrence is the solar system is quiet and won't be running out of fuel anytime soon.

I know the flaw in my thinking is possible damage to the panels in a storm,simple answer is bring them inside until the storm is past,average storms can be handled by plexi covers.After a storm like Katrina payback could be in a matter of a couple weeks.

We haven't even considered the age of our grid system and the possibility of terrorism.IMHO our grid system is one of the weakest areas we have and I believe the crazies realise this too unfortunately.

J Tiers
09-10-2007, 11:35 PM
The panels the tree smashed were "folded over", the top 1/3 of the panel was at a 60 deg angle to the rest.

But, they were actually still putting out about 40% of the power they had before being squashed.

Arrays are not necessarily that fragile. And new ones have very substantial frames. The frames of the individual Carrizo panels were minimal, almost an "edging" only.

The overall frame was bent by the tree, or the panels might have been un-damaged. The tree fell about 40 feet and the panel setup was hit by two forks in the branch. The first one the panels actually split off the tree, likely without damage, but the second and larger one bent them.

I assembled my system for less than $1000, including a 2500W inverter, but you can't do that now. Panels have gone up a lot, and no more used ones are out there. Apparently some countries have tax credits, and they are buying every panel that can be made... no discounts.

wierdscience
09-10-2007, 11:46 PM
The panels the tree smashed were "folded over", the top 1/3 of the panel was at a 60 deg angle to the rest.

But, they were actually still putting out about 40% of the power they had before being squashed.

Arrays are not necessarily that fragile. And new ones have very substantial frames. The frames of the individual Carrizo panels were minimal, almost an "edging" only.

The overall frame was bent by the tree, or the panels might have been un-damaged. The tree fell about 40 feet and the panel setup was hit by two forks in the branch. The first one the panels actually split off the tree, likely without damage, but the second and larger one bent them.

I assembled my system for less than $1000, including a 2500W inverter, but you can't do that now. Panels have gone up a lot, and no more used ones are out there. Apparently some countries have tax credits, and they are buying every panel that can be made... no discounts.

I'm not as concerned with tree damage as I am them turning in to frisbies and ending up with Dorthy and Toto,but it is incouraging that they can take some abuse and still function.

There are some panels out there that aren't too bad price wise,the Chinese models for one.

How much wattage in panels did you have for what capacity system?

J Tiers
09-11-2007, 01:06 AM
I had/have about 100W in panels, with 400 AH of batteries. This system is primarily for lights in the building (all 12V) including a motion detector light outside. Other 12V loads include a pond pump.

It is also used for incidental 120V loads, such as a drill press and other power tools including an air compressor (Craftsman roll-around). They don't get a lot of use, but they are really handy when needed.

If I used those heavier loads much I would have to put up more panels per the general guidelines I mentioned in a prior post. As it is, it provides power where there wasn't any, serves as back-up power for the house, and allows me to check out various related products and devices. The irregular heavy usage and short-term nature of the lighting usage allow the small panel setup to work out OK.

jdunmyer
09-11-2007, 08:56 AM
At retail prices, my 2, 75-watt panels, controller, and eMeter would cost about $1500.00. Because of a "hot deal" on some seconds, my panels cost only $225.00/each instead of about $450.00/each, so I came in at "only" $1000.00. Plus about $150.00 for the batteries. Output? Nearly 1/2 Kwhr/day! At our price here, that's about $.05/day or $1.50/month. If it's sunny every day.

As far as ruggedness, most solar panels have tempered glass in front, they're very sturdy. I doubt that most hail storms would damage them.

A solar system that will do what you want will run closer to $10,000.00, that'll buy a lot of gas every few years. Figure 8% on your money, and that's $800.00/year, which will buy all the power you need for lights, etc.

I hate to be a wet blanket, but them's the facts. I liken what you're proposing to the fella who drops in here and insists that he's going to buy a Harbor Freight 7X10 Mini-Lathe to make big parts, to .0001" tolerances. We'd all advise him against it, as he'd be wasting his money and getting frustrated in the process.

<<Jim>>

J Tiers
09-11-2007, 10:18 AM
Naw, it's not that bad....

And I know folks who are in places as much as 2 miles and $15,000+ from the grid, who have put in LARGE systems for around $5000. Enough to run their houses.

Point being that if you are all about the Benjamins, it may not make sense. But if you expect situations in which all those Benjamins may not make a lot of difference, then it makes sense.

It might make NO sense to put in a $10,000 backup generator either. You can always do without for a few days, or go to a shelter/displacement camp. And if, as is usually the case, it is a natural gas generator, then just when you really need it it may be down due to pump failure at the gas Co.

You pay a lot for insurance, have you got that much back from it? With interest? Would have made more sense to invest the $$.

It's all choices..........

jdunmyer
09-11-2007, 10:10 PM
Well, if W.S. is really interested, he should do the arithmetic before spending his first dollar. It's quite easy, and outlined in my article and at several of the solar sellers' sites.

Home Power Magazine wrote up several whole-house installations, and IIRC, they were talking something like 15-20 grand to give the owner something approaching grid power capabilities.

Again, it ain't rocket science, just simple math. If you don't do it first, you're likely to be disappointed. I'm agonizing at present over a new refrigerator for our trailer. The late models all require 12VDC for the electronics, even when running on gas. I'm told that about 500 Ma will do the job; that's 12 AH/day, nearly 1/3 of what my system is capable of. The pilot light that tells me the pump is 'on' draws 100 Ma, even that is 2.4 AH/day. It all adds up, and when you're off grid, you pay attention to those things.

wierdscience
09-12-2007, 12:54 AM
Well, if W.S. is really interested, he should do the arithmetic before spending his first dollar. It's quite easy, and outlined in my article and at several of the solar sellers' sites.

Home Power Magazine wrote up several whole-house installations, and IIRC, they were talking something like 15-20 grand to give the owner something approaching grid power capabilities.

Again, it ain't rocket science, just simple math. If you don't do it first, you're likely to be disappointed. I'm agonizing at present over a new refrigerator for our trailer. The late models all require 12VDC for the electronics, even when running on gas. I'm told that about 500 Ma will do the job; that's 12 AH/day, nearly 1/3 of what my system is capable of. The pilot light that tells me the pump is 'on' draws 100 Ma, even that is 2.4 AH/day. It all adds up, and when you're off grid, you pay attention to those things.

Maybe you mis-read,but I'm not thinking of anything even close to grid power,like I said all of my heavy current loads will be on the grid,that load could be in excess of 125amps@230vac,no way would I even consider doing that with solar.
The only thing I want to do is run the lighting in the shop,at night after the system has had 10-12 hrs in the sun during the day(I work during the day so the lights will be off then).3hrs at a 800watt max load in the evening ain't much.

Evan
09-12-2007, 06:02 AM
Darin,

If all you need is to run some lights and a freezer then why use a 5000 watt generator? That's inefficient as all get out. A 1000 watt inverter unit with idle back will do that and use a tenth of the fuel of the 5000 watt unit while it's doing it. I'm just finishing up building one right now. Total cost about $150 for the inverter and a battery to prevent power loss during refueling as well as act as a voltage regulator. The rest is a lawnmower engine and an alternator salvaged off an old vehicle plus a few odds and ends in my packrat stash. I'll put up some info as soon as I get the electronic throttle servo control finished, probably today sometime.

J Tiers
09-12-2007, 10:15 AM
Maybe you mis-read,but I'm not thinking of anything even close to grid power,like I said all of my heavy current loads will be on the grid,that load could be in excess of 125amps@230vac,no way would I even consider doing that with solar.
The only thing I want to do is run the lighting in the shop,at night after the system has had 10-12 hrs in the sun during the day(I work during the day so the lights will be off then).3hrs at a 800watt max load in the evening ain't much.

Eh... hate to be the one to break it to you, but that is 2400 watt-hours. Remember my example above? That was for 500 watt-hours.

Start multiplying by a factor of FIVE.

If you want to use solar, then you need to use more efficient lighting, or you will have to re-size the system upwards by a LOT.

jdunmyer
09-12-2007, 05:53 PM
WS,
An 800 watt load for 3 hours equates to 200 Amp-Hours from your batteries. The draw will be about 67 amps, so you'll need some very sizable batteries to supply that w/o ruining them in short order. Also, you don't want to run your battery bank much below 50% charge if it's to give you good live. Just off-hand, I'd say you'll have to use the equivilant of 8 golf cart batteries in a series-parallel configuration. That would keep the draw to about 17 amps on a given battery, and the AH usage would be very doable.

Now, to get 200 AH of charging, you'll need about a half-dozen 100-watt solar panels. Those run between $500.00 and $600.00/each.

All of the above assumes 100% efficiency, and no loss from the inverter. Figure 80% overall, and you'll be closer.

If you want to experiment, I'd recommend that you buy one or 2 panels of [whatever] size, a 12VDC flourescent light or 2, and a pair of golf cart batteries. Get some metering of some sort so you can tell what's going on (you wouldn't attempt machining w/o measuring tools, would you?) and have at it.

J Tiers
09-12-2007, 10:31 PM
More like 240 amp-hours, with losses. And I would figure closer to an 80 amp draw, for rough estimation purposes.

Golf cart batteries are about 200 AH, so you'd clearly need several strings of them as mentioned.

It would be SUBSTANTIALLY cheaper to get more efficient lighting and THEN size the system.

wierdscience
09-13-2007, 01:08 AM
I may have caught a break today,I'm on the trail of a local junk dealer who is reported to have a "stack" of used panels.I'll know more tomorrow,wish me luck.