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Old 12-27-2014, 08:08 PM
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Default Details for Solar Power for Us Dummies?

Every article on solar power that I've ever read just deals with vague generalizations or too many options to be useful to those of us whose knowledge of things electrical is somewhat challenged.

Can one of you experts out there give us a detailed plan of the simplest, cheapest way to provide enough solar power to run [a] a full size freezer and/or [b] a well pump, say 1hp?

We would need to know exactly how big an array of cells is needed, how many and what type of batteries would be required and how big an inverter is required.

Let's say we do not live in the sun belt.
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Old 12-28-2014, 07:09 AM
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Chest freezer should be marked as to its power draw. Well pump however is probably 240VAC & would require a separate inverter.
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Old 12-28-2014, 11:17 AM
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The 2 items you list I think are one of the biggest challenges with a solar setup - refrigeration and water pumping. Both have such a draw that it is impractical. It can be done of course but the amount of panels, battery storage, and large inverters make it cost prohibitive.

When we were off grid - while I didn't have a solar system (was working on the planning stages) we used alternate power for things like that. First was a propane refrigerator - even thought they are small it was plenty for us - and quite efficient use of propane. Since we did need a freezer also since we raised our own beef and pork we opted to put a freezer in town and a friends service garage. It was in a back room of his business which always allowed us access during business hours. Paid him $10 per month. Since we had a routine of going to town once a week (one horse town 16 miles away) we would grab what we needed for the week and put it in the freezer section of our refrigerator.

Water pumping - as much as I hated it I used a generator to pump water. I installed a couple 30gal plastic water tanks above the rafters and gravity feed the house (only 2 faucets plus the hot water tank on our wood fired cook stove. Would have to run the pump/generator every other day to fill the tanks - took about 5-10 minutes. It was a 240v 1/2hp submersible pump. We also had a hand pump on the well head for filling 5 gallon buckets for other needs.

So all that was left for power needs were lighting and the occasional use of a small TV and radio. A small solar setup would have easily met those needs. Until I could afford the solar setup I used 2 huge marine deep cycle batteries - then had 12V fluorescent lights in the house (this was before the LED's were available). A small inverter then for the TV and other small stuff. I would use the generator once a week to charge the batteries - again hated using the generator but was working toward a solar setup.

So my point is it would be much more cost effective to look at other means to power those really power hungry appliances. There are propane freezers made but are small - would just have to adjust your storage needs.
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Old 12-28-2014, 11:50 AM
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Take a look at this site. It tells the amount of useful sunlight per month that you have to work with. (Average) In your state, you have 1.5 hrs. of daylight to work with. Your specific town/area may vary but not by much..

http://www.gaisma.com/en/

Design for December and things will work year round.

You need to be very specific on the amount of power that you need to produce for a 24 hr. period. (Pump wattage/Length of runtime per cycle.. Same for the freezer) Add ~20% on top of that to allow for weather/living habit changes..

If you're going to use the system as a total 120/240 A.C. system, design with either a 24 or 48 volt battery..

We need some wattage/voltage numbers and length of run time(s) and how many times things turn on /off in a 24 hr. period. We can figure the pump @ 740 watts/240 volts but we don't know how many cycles it does in a day. (24 hr. period) Same for the freezer..
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Old 12-28-2014, 01:11 PM
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I operate a 5cuft chest freezer with a 520watt solar system but I'm in Florida.
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Old 12-28-2014, 03:57 PM
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Quote:
Originally Posted by 12vman View Post
Take a look at this site. It tells the amount of useful sunlight per month that you have to work with. (Average) In your state, you have 1.5 hrs. of daylight to work with. Your specific town/area may vary but not by much..

http://www.gaisma.com/en/

Design for December and things will work year round.

You need to be very specific on the amount of power that you need to produce for a 24 hr. period. (Pump wattage/Length of runtime per cycle.. Same for the freezer) Add ~20% on top of that to allow for weather/living habit changes..

If you're going to use the system as a total 120/240 A.C. system, design with either a 24 or 48 volt battery..

We need some wattage/voltage numbers and length of run time(s) and how many times things turn on /off in a 24 hr. period. We can figure the pump @ 740 watts/240 volts but we don't know how many cycles it does in a day. (24 hr. period) Same for the freezer..
I'll be in WI, ~44*N. I've seen sites that claim we have ~4-5 hrs of good sunlight/d, but that's highly variable with many overcast days balancing with a few cloudless days.

The specs on the freezer claims it uses ~450 kW-hr/yr (ie- average ~1,25 kW-hr/d). Can you use that for an educated guess on equipment?

I have grid power there @$0.20/kW-hr. It's a no-brainer to just use that.....unless the S ever really HTF. It would be nice to be able to keep on using the 350 ft deep well and to eat the fresh frozen meat I raise.

A solar system seems more sustainable, given the lubrication needs of an ICE/generator set-up, even with wood gas as fuel.

If that's not feasible, then I guess I'll just have to get used to eating pemmican and boiled spring water
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Old 12-28-2014, 05:06 PM
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One thing to note about hours of sunlight - I don't know if WI has mountains or not. Here in the NW mountains of PA I am in the shadows of the mountains. If sunrise is at 7am I don't see the actual sun until 9:30 - same thing goes in the evening. So the amount of sunlight can be very sight specific.
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Old 12-28-2014, 08:22 PM
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We use a Shurflo DC submersible pump in the drilled well. It can be run on either 12volt or 24volt dc power. It is inexpensive, very light weight (you can install it yourself), and reliable. Mine is wired directly to my battery bank. The pump slowly fills a cistern inside of the house. They also draw very little electricity, and the pump is not harmed if run dry.
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Old 12-29-2014, 02:01 AM
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1250watts divided by 120volts is 10amps per hour. I find that hard to believe. You really need to look at the ID tag. 10amps at 120VAC would be minimum 100amps from the batteries.

Now, my small chest freezers have an initial draw amperage but quickly goes to a much lower run amperage. Over 6amp initial draw then stabilize at 1.67amps.
There is also consideration of how often you will be getting into the chest freezer.
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Old 12-29-2014, 09:43 AM
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"The specs on the freezer claims it uses ~450 kW-hr/yr (ie- average ~1,25 kW-hr/d). Can you use that for an educated guess on equipment?"

According to the chart at Gaisma, your general area receives an average of ~1.4 hrs. of sun that's good enough to use in December..

You have slightly over an hour to collect enough energy for 24 hrs. usage. I'd figure around the same amount of panel (1250 watts) with the extra 40 min. of charge time to cover any losses. (The 20% loss in the battery and weather conditions)
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Old 12-29-2014, 01:00 PM
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Quote:
Originally Posted by 12vman View Post
"

You have slightly over an hour to collect enough energy for 24 hrs. usage. I'd figure around the same amount of panel (1250 watts) with the extra 40 min. of charge time to cover any losses. (The 20% loss in the battery and weather conditions)
Thanks.

Now for batteries: if I need 10amps/hr each 24 hrs = 240 amps/d, so a single "car battery"[~400amps] should be enough to run the freezer?
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Old 12-29-2014, 01:26 PM
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Quote:
Originally Posted by HuntingHawk View Post
I operate a 5cuft chest freezer with a 520watt solar system but I'm in Florida.
My freezer is 20cu ft, so allowing for improved efficiency with the larger size & cooler weather here, the 1250 W number is probably in the right ballpark.

I'm trying to get a feel for the feasibility of solar power for this application. I won't mind paying more for each kW-hr if the overall cost of the system is small enough. It's kinda like the price of gas vs gas mileage: if you don;t drive much, then you don't really have to worry about cost/mile.
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Old 12-29-2014, 04:16 PM
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Car batteries and deep cycle batteries are 2 different animals. Car batteries give up stored energy in a quick surge but deep cycle batteries give up their energy at a lower current rate for a longer period of time..

You don't want to discharge a battery any lower than 25% of its total capacity. This means that you would need a deep cycle battery with 4 times the needed (usable) amount of aHr.s..

The amount of aHr.s is figured on the battery voltage. The higher the storage battery voltage, the lower aHr.s is needed BUT you would need more batteries connected in series to achieve the voltage..

Figuring a 24 volt battery voltage, for 1250 watts of usage, you would need ~52 aHr. of battery. Multiply that by 4 (The 25% total discharge thing) and you would need a 24 volt battery with ~200 aHr. of total reserve. I would suggest something like these, 4 connected in series..

http://thesolarstore.com/trojan-105-...8e4b1800dd410c
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Old 12-29-2014, 06:49 PM
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Check out engineer775 on utube. he is doing/has done several of the things you are asking about.
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Old 12-30-2014, 12:38 PM
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So it looks like I'd need ~1300 W-worth of solar panels @ ~ $1/W and 4 batteries @$150 ea. Throw in a few 100 for inverter, wiring and odds & ends to run my large freezer without worrying about the availability of grid power. Total roughly $2200 and "free" electricity for 20+ yrs.

If grid power remains $0.20 / kW-hr, I could run that freezer for ~$1800 for 20 yrs. (I'm 65y/o now. Let the nursing home folks worry about it after the next 20yrs have passed.)

So it would only cost me ~$20 extra per yr, not counting "lost investment potential" [as if I'd really be investing that 2Gs] to have energy security for this application.

Sounds do-able. I'll cogitate on it for awhile. Thanks for the input everybody.
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Old 12-30-2014, 07:03 PM
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That's where I run into a snag thinking about a solar system vs. just staying on grid and being as effectient as possible. My cost of electricity is quite different however at .623 per kW-hr.
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Old 12-30-2014, 08:28 PM
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Wow! I've always figured solar costs ~3x grid power, and then you have to replace it at just about the time it finally pays for itself. But you're already paying 3x the "normal" price, so you outta go for it.

I figure the cost so high because, in order to supply the typical 900kW-hr/month, we're talkin' $30Gs up front and you lose quite a bit of investment potential by tying up that dough for 20+yrs, or, you're borrowing the money and paying interest.

I don't have 30Gs to use like that, but I can afford to shell out 2.5Gs for this limited application and gain a certain amount of "energy security" by doing so. Maybe that's the wisest way to go: not either-or, but both in efficiently calculated applications.
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Old 12-30-2014, 08:36 PM
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That's why my first suggestion was to try to find an alternate for your freezer and well pump. Just for lighting and small appliances - especially with the great LED's now - a nice small system is plenty.
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Old 12-30-2014, 08:47 PM
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We're thinking in opposite lines. To me, doing without the freezer (raising beef & pork) and well (350ft deep; can't manual pump it) would require major life style changes. I could easily live without electric lighting or TV-- and if TSHTF, there won't be any TV or internet anyways.
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Old 12-30-2014, 09:23 PM
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Quote:
Originally Posted by doc View Post
So it looks like I'd need ~1300 W-worth of solar panels @ ~ $1/W and 4 batteries @$150 ea. Throw in a few 100 for inverter, wiring and odds & ends to run my large freezer without worrying about the availability of grid power. Total roughly $2200 and "free" electricity for 20+ yrs.

If grid power remains $0.20 / kW-hr, I could run that freezer for ~$1800 for 20 yrs.
Sounds do-able. I'll cogitate on it for awhile. Thanks for the input everybody.
Not quite...
Battery replacement evey 3 years or so. Depending on the batteries and on how well you took care of them.

Last edited by DavidOH; 12-31-2014 at 09:15 PM.
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