Solar panels: wattage, brand, applications..? need help :)

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z's picture
z
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Solar panels: wattage, brand, applications..? need help :)

 Hi,

I've tried looking at former threads but haven't quite found what I need, so here goes.

I want to set up a small solar system (200-300w panel) that will power an off-grid battery. This battery will power my 2 laptops (~3 hours/day), AA battery charger, TV/DVD (~2 hours/day), and maybe some lights. Also, I really want to try and take my fridge off-grid (it uses about 700Wh/day). We live at the edge of the desert, so sunshine is not a problem... but I do have some questions for the experts:

1. Is powering all this really feasible with a 300w panel, even working 8-10 hours a day at full capacity? 

2. How much power do I really need to generate?

3. What are the best brands of solar panels to buy?

4. What else do I need (inverters, etc.)? 

2. If not, I really wanted to switch to a chest freezer. Does anyone have any experience with these? 

Thanks a lot for any comments,

Z.

 

   

GiraffeOK's picture
GiraffeOK
Status: Bronze Member (Offline)
Joined: Apr 14 2009
Posts: 36
Call the experts

The best resource I found for solar advice is at www.voodoosolar.com. They sell products but are not pushy. They are willing and able to answer questions. Read the relevant information on their website, then make a phone call with your specific questions.

treemagnet's picture
treemagnet
Status: Gold Member (Offline)
Joined: Feb 13 2011
Posts: 344
got ya covered

go to altestore.com

 

These guys are awesome.  The first thing the put me onto was the kill-a-watt.  Its this cool device you plug into whatever and it'll tell you how much watts, amps, volts, kwh the device is drawing.  I too want to have off grid battery backup for three or four devices, but now they have hybrid systems so you can use solar/generator/grid to combine the best of both worlds.....for now.  Anyway, I got into this a few months ago and am just getting back to this but look forward to any interest on your part or others.  Travlin is sipping tree bark tea, so he's unavailable - so its just you and me, for now. 

The short of what I've learned is energy storage..batteries, is the issue.  Three types, with advantages/disadvantages - I need two/three like right now, so I am giving this topic my undivided attention, until you know....squirrel!.....anyway, look forward to your comments. 

TNdancer's picture
TNdancer
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Posts: 127
z wrote:  Hi, I've tried
z wrote:

 Hi,

I've tried looking at former threads but haven't quite found what I need, so here goes.

I want to set up a small solar system (200-300w panel) that will power an off-grid battery. This battery will power my 2 laptops (~3 hours/day), AA battery charger, TV/DVD (~2 hours/day), and maybe some lights. Also, I really want to try and take my fridge off-grid (it uses about 700Wh/day). We live at the edge of the desert, so sunshine is not a problem... but I do have some questions for the experts:

1. Is powering all this really feasible with a 300w panel, even working 8-10 hours a day at full capacity? 

2. How much power do I really need to generate?

3. What are the best brands of solar panels to buy?

4. What else do I need (inverters, etc.)? 

2. If not, I really wanted to switch to a chest freezer. Does anyone have any experience with these? 

Thanks a lot for any comments,

Z.

 

   

 

1.  Hard to say, since there is no power use listed for anything but the fridge, but if you throw in the fridge, then, no, definitely not enough panel. Don't figure 10 hrs/day at 300w.....more like 6 hrs at full 300, and a bit more early/late.....but you will not get 300w first thing in the morning....actually you'll only see 300w on cold, clear days AROUND NOON for fixed mount panels

2. Probably 2-4kw/hrs/day....meaning you'll need probably 500-800w of panels.  You have to consider system losses, and such.....not everything you generate do you get to use.

3.  That's hard to say, LOT of good panels out there....only ones I'd avoid are low end Chinese panels.

4. You need, at a minimum, a charge controller, some disconnecting means, fusing between the battery bank and inverter(s), and a GOOD inverter.....not a 300 buck model.

 

 

Chest freezer:  Do you mean convert a chest freezer to use as a fridge using an external thermostat ?  Yes....done it.....works good, a 7-9cuft chest freezer will stay at fridge temps (36-38) using an external thermostat, and use about 200w/hrs/day...... less than a conventional fridge ( but quite a bit smaller also )

 

guysmilely's picture
guysmilely
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Posts: 9
I used power4patroits.com

I used power4patroits.com it's a guide to energy independence it's more than just solar. 

rhare's picture
rhare
Status: Diamond Member (Offline)
Joined: Mar 30 2009
Posts: 1326
Thoughts on solar....

First thing you need to do is get a "kill-a-watt" ($25 at Radio Shack, less on-line) and figure out how much power all that stuff uses.  Don't just plug it in and take a reading.  Leave things (one at a time) plugged in to it for a day or so, then divide the power used by the time to get a good average power use estimate (kill-a-watt has both time and power consumption).  You will also want to get a "max current draw" reading as well. A system will have to produce enough power to run things and be able to supply peak current.  For example, our fridge uses an average of 200W, but when the compressors running it shoots up to 500W.

Affordable Solar has an off-grid estimator to help figure out what you need as well as kits for sale so you can get an idea of pricing/things you will need.

You will want to look at the PV Watts site as well.  You can enter your location, system size, de-rates, tracker use, etc. and get a fairly good estimate on what you can expect from the system.  It will vary a lot by month.

I have heard horror stories about the cheap Chinese panels and inverters - so like others have said, I would stick with good name brands (SMA, Outback, Xantrex, Sunpower, Schott, Sharp,...)

I put together an article "Installing a Solar Energy System" for the "What Should I Do" series.  While our system is much larger than what you are looking to build, much of the content will still apply.  The biggest difference is you will probably be looking at a traditional DC-coupled off-grid type system versus the AC-coupled system we built - Outback has a paper describing the differences.

 

 

earthwise's picture
earthwise
Status: Platinum Member (Offline)
Joined: Aug 10 2009
Posts: 848
TNdancer: how'd you do that?
TNdancer wrote:

 

Chest freezer:  Do you mean convert a chest freezer to use as a fridge using an external thermostat ?  Yes....done it.....works good, a 7-9cuft chest freezer will stay at fridge temps (36-38) using an external thermostat, and use about 200w/hrs/day...... less than a conventional fridge ( but quite a bit smaller also )

 

TNdancer,

I've been looking at different options for a large refrigerator for a variety of uses like root cellaring, hanging meat etc.  I think I recall seeing one of your previous posts where you had tried a Coolbot with a room air conditioner. I've been strongly leaning in that direction but maybe the 'fridge with external thermostat might be sufficient. Could I trouble you to elaborate on both options?

Thanks in advance.

TNdancer's picture
TNdancer
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Joined: Aug 20 2008
Posts: 127
earthwise,   Yes, I use a

earthwise,

 

Yes, I use a Coolbot with a 10,000BTU Samsung window AC unit to run a walk-in cooler.  It will hold a 7'x7' homebuilt cooler right at 34 degrees using 2kw/hrs/day.  I normally only use it to chill meat we slaughter on the farm prior to cutting.

 

The external thermostat on a chest freezer is on I obtained from Kegman.com, that beer brewers use to cold brew.  A 7cuft regular chest freezer will use about 200watt/hrs/day, making it a very efficient fridge.  IF the SHTF, this would be a good option for some refrigeration using a fairly small amount of power....a few hours of good sun on a 250w solar panel would run this fridge for a couple days.

MrEnergyCzar's picture
MrEnergyCzar
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Joined: Oct 14 2010
Posts: 54
portable battery power...

You want this thing then....  have a couple and you can weather a long storm outage.....  

http://www.northerntool.com/shop/tools/product_200485226_200485226

 

MrEnergyCzar

 

earthwise's picture
earthwise
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Joined: Aug 10 2009
Posts: 848
TNdancer
TNdancer wrote:

earthwise,

 

Yes, I use a Coolbot with a 10,000BTU Samsung window AC unit to run a walk-in cooler.  It will hold a 7'x7' homebuilt cooler right at 34 degrees using 2kw/hrs/day.  I normally only use it to chill meat we slaughter on the farm prior to cutting.

 

The external thermostat on a chest freezer is on I obtained from Kegman.com, that beer brewers use to cold brew.  A 7cuft regular chest freezer will use about 200watt/hrs/day, making it a very efficient fridge.  IF the SHTF, this would be a good option for some refrigeration using a fairly small amount of power....a few hours of good sun on a 250w solar panel would run this fridge for a couple days.

Wow! Awesome! That's exactly the purpose  I had in mind, too. Where did you get that door? I figured that I would have to rig up something that would function but would be a little less........um..... what's the word...........stylish?

So, with five sides of meat hangin' there one question remains: When's the BBQ?

TNdancer's picture
TNdancer
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Posts: 127
You can't see one hanging

You can't see one hanging behind another, but there are 6 sides in there......product of three pigs we raised last year.  One for a neighbor, who helps me on cut/wrap/freeze day, and two for us.

I built the room on the back of the existing house garage.......sawed a big hole in the wall ( closed in later with pair of doors.....I can drive my tractor in the garage door, and right into the meat room, lift the halves/quarters off the front loader forks and into the cooler ).

Also built a flue for a wood cook stove in the room at the same time.

 

 

 

Hole back there between the ladders is the opening for the window AC where the cooler will be:

 

Tying the roof into the existing garage roof.  Oh, yeah, all the lumber came off my Woodmizer sawmill from logs off our place.

 

Internal partion wall, cooler door set in the studs.  Space to the right is for a walk in pantry room.  Stuck a little 60amp subpanel in the wall to power the whole room. ( left wall ).....that was was the exterior wall of the garage before.

 

Finished look....cooler door, pantry door, wood cook stove.

 

 

The door I found from a guy that had a complete walk-in cooler and freezer unit.  He offered me the whole deal for just hauling it off, but I couldn't use the wall/ceiling panels, as they ( along with the door ) are 46" wide.....two of the wall panels would have been too wide for the space I wanted to alot, so I simply bought 2" foam board, cut it to fit, and used two thicknesses, held to the studs with LONG screws. ( Log cabin screws ).....so the door was the only commercially made part I used....which works really NICE.   The inside walls, I finished with white fiberglass board I bought at Lowe's.  Was planing to tile the whole thing, but decided the FB board was simply cheaper and easier at the time. Did tile the floor and put a floor drain in.....also a floor drain in the main room floor.  I have a hot water rated hose plumbed into a 30gal eletric water heater under the sink counter that will reach to the back of the cooler so I can hose the whole room down with hot water.  You can see it in the next photo.

 

Found a deep two compartment commercial sink....had legs, I removed them and set it down in the counter top....counter top is Corian (knockoff) from a building surplus store (cheap)....I used the expoxy to make it up, and then routed the edges.....stuff is REALLY easy to work with, but REALLY dust when you sand it.....do it outside if you ever work with the stuff.  We use the room for meat cutting, canning, and so on.....got the doors/drawer fronts done now, and a cabinet built for a dual propane burner ( you can barely see it in the left edge ).  Really handy room when you need it .....plus canning out there in the summer doesn't heat up the house. We actually used the kitchen as our main kitchen for about 6 months while I gutted the house kitchen and rebuilt it.  Here's a peek at it:

(If you look out the window over the sink, the canning kitchen is to the left.  The window in the canning kitchen used to be in this kitchen, wife wanted a taller version, so I simply moved it to the new room, and installed a taller one so she can see the woods better )

ajdinos's picture
ajdinos
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Joined: Jan 8 2013
Posts: 1
efficiency

You read reviews on suppliances here:

http://www.minifridge24.com/

Every appliance is also graded on how energy efficient it is.

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