450w 12v system or 380w 24v?

[Naptown]

For 12V the marine ones are probably the only option available.

Could also be done with a small pressure pump, accumulator tank to keep the pump from cycling all the time and a household RO system. but will likely use much more power than the true marine one and provide less water.

[Mike90250]

Hi

OK I do agree for grid type cooking aplliances with an inverter but 12 volt cooking appliances can be great from PV and batteries.

Maybe not if you want to cook for hours but for simple cooking needs 12 volt and PV may be the thing many are looking for.

A 12 volt slow cooker uses around 10 amps so even that will only use around 30Ah for 3 hours ...that would be a bit much for many but might be ok for others.

Other 12 volt appliances use FAR less, as little as 10-20 watt hours and can even be used from a small battery as samll as 7 to 10 Ah with a small solar panel.
Yes I will kill a 7 Ah battery doing this but it is not as quick as many would think and will probably still be very economical.

I have also been experimenting with directly cooking form PV without a battery and it works very well so far (a bit more to do but i think it will be good pretty soon).

Armour on now!

Armour on indeed.

First, let's settle on 1 measurement unit. Watt Hours. a 50 watt bulb, for 2 hours, is 100 watt hours Apply the same formula for every appliance, and then to the solar array.


If you have volt & amps, just multlply to get the watts (it's going to be close enough, lets not delve into Voltamps now)

Your crook pot (slow cooker) is 12V , 10A for 3 hours. That's 120 watts for 3 hours or 360 watt hours.

Your region gets (for this example I'l use 3 hours) _3_ hours of solar exposure. 200watts of panels.

The very most you can hope to harvest is 600 watt hours. Since you are using and recharging batteries, your efficency factor all in all , will be 50% of your panel x sun = useable energy. Harsh, but true. One good 3 hours sunny day, you can cook one pot. Or have lights for several hours, or a laptop.

Use PV Watts, or some other solar insolation tool to get the solar hours for your area:

http://www.nrel.gov/rredc/pvwatts/

[Khoogyra]

Wait wait wait... By marine ones you mean Desalinators? Cuz from what I remember seeing, they're like $4000+. I will look further into it however...

As for running the inverter. You say the voltage (not wattage? (probably and?)) should be higher for AC loads, correct? So in other words, I should go with the 190w 24v panels with MPPT. Which gives me the ability to 'grow' later on. I realise I can't grow the battery bank, but a few extra panels later on will help when this battery bank dies. The only thing I don't like about these 190's is that they're 6x12 cells vs the 4x9's that I have now. That's a substantially larger panel.

I HAVE looked a bit more into Solartown, but they won't let me create an account to see the shipping costs. It keeps saying 'Billing/Shipping state required.' I guess because I live in Canada, I don't have a State, but a Province, and it errors on me. I don't know... and at this point, unless they have a warehouse in Vancouver, or nearby, it seems unlikely that the cost of these other panels is going to be any better than I currently have. Sure, they say $1.56/w, but then you have shipping and if it comes from the states, you have to add HUGE tariffs for Chinese made products.

Case and point. Last year I ordered a whittling knife from the states. It's a real beauty of a Carbon Steel knife, but it was ~$150. It was also MADE in the states. However, it gets to my door and Canada Post says, 'Oh hey, that'll be $35 in tariffs from crossing the border.' I reply that I thought the point of free trade was that if I ordered goods made in the states, that I wasn't charged any tariffs. and finally... he says, 'Well, we recently changed the rules, and you get tariffs on anything above a certain price and it's based on a % of that cost which you paid. If you like, I can send it back.' Of course I just took it and paid the $35.

So on a $150 knife, I get $35 in tariffs. Let's see about making that a $1500-$2000 order... Well then we're talking potentially 300-700 in tariffs if I order from the states. And since this stuff would be made in China, I have no doubt that there would be brutal tariffs added. Perhaps I'm wrong.. and if I can find a way to get a quote from Solartown, maybe I'll still change my mind.

I'm still about 2 weeks away from purchasing this system. Though... if I order from a site, I'd have to order now I guess, because I want to leave in 3 weeks. In all, I'm probably best at $3/w without online hassle and tariffs, etc. In truth, that's $2.73/w + tax and I order it from a local dealer that I pick it up and know what I'm getting. ST is $1.56 + tax + tariffs and unknowns on the other end. I'm still interested, and maybe if there's a representative I can write to, I'll ask what they think of the situation. However, at this point I'm leaning back towards my local dealer. He was a nice guy to talk to and was just as 'real' as Sunker in letting me know what I'd need to do the things I want.


So... All that said, another question. Which may be best answered elsewhere. I have a pump that was given to me by a fish guy back when I was running a 150g with Arowanas, Tigers, and Charming Phoenix (google sygoomei if you'd like to see some vids) it's like a 1.5a load on... I think DC (or at least it doesn't have a 'plug.' I'd have to take a look for it. But in the best of conditions, it pumps 24.3 gallons per minute or something like that. It will also pump 'up' 15' So I wonder if i can take an RO filter and affix it to a hose somehow, to have this pump do the work of the RO unit. It's just a thought. It's coming with me regardless of which, so that we can run it occasionally for irrigation purposes (2 15,000g ponds downhill from fields). So if it had another purpose, that'd be nice.

Oi, so in all... Even $3000 doesn't seem like enough to really do much. I will end it all with the question I still haven't received an answer to:

Is it easier, and safer on the batteries to run A/C loads during the day, when the sun is shining and the panels are producing electricity? Would the power come from the panels, and be topped up by the batteries, or would it be a continuous drain from the battery, with the panels trying to keep the charge up?

Tonight I will sit down to another study session and try to figure some of this stuff out on my own. For now, I'm off to work and to play my pocket sax with the new 'slide technique' I just learned!

[Khoogyra]

Thanks for more input Mike.

Although it was probably knowledge already in my head, no one has stated it so simply in their PV guides. A question that comes up then is this... Am I better off with a modest solar array (2 x 190w 24v) with 3 or 4 110ah batteries, or a larger array (3 x 190w 24v) with just 3 110ah batteries? Less load capability at night, but more ability to run AC loads in the day. Maybe I'm way off target here. But I'd be willing to rethink fridge for a while and possibly add a 3rd or 4th 190w panel to make things more viable in the long run.

Also, what's 'usable' light? I mean, the panels will go on an open field. Likely they'll go on top of an RV or trailer or something, where trees won't block the sun. I'll also be looking at designing a way of angling/turning the panels for added output. Though that comes later on I'd think. But apparently there's LOTS of sun where I'm headed. The clouds roll overhead and because there aren't any mountains, continue on to Vancouver. In terms of 'plants' there's full sun. 9+ hours of sun is my guess. Though, that's obviously at various angles, etc. Now, that said, the fellow who sold me my panels was running an array of 6 85w panels and was receiving 0.7a on a DARK cloudy day. His system and mine are similar in wattage output, but I'd think I'd lose less power, thanks to 24v and less wiring.

Oi, my head is starting to swim again with desire to research... Why oh why do I have to have so many interests in life?

On a final note, I may scrap the RO system altogether and simply design my own sand filtration system with the pump mentioned above. This was all brought up because everyone on the farm drinks rain water exclusively and I'm worried about the quality of water they're drinking because rain in temperate climates tends to be quite acidic and can fall as low as 3.2 anywhere in the world (lower in many cases) and at that ph, lead, mercury, and other heavy metals become water soluble. Not only that, but if indeed the water is that low, Aluminum becomes water soluble below 3.5... Bad news.

So sand filter + crushed coral to raise the ph may be my best option.

Any thoughts are most welcome.

[Mike90250]

I'm using a slow sand filter, with a flushable gravel bed filter ahead of it. Using a precision flowmeter to control the rate, as excess water just drains away.

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

Granger # 5P350 Meter, Water, 2-25 Gph

http://www.grainger.com/Grainger/KEY-INSTRUMENTS-Water-Meter-5P350?cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1

<http://www.grainger.com/Grainger/KEY-INSTRUMENTS-Water-Meter-5P350?cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1>

Mfg KEY INSTRUMENTS # FR 4L48

http://www.keyinstruments.com/standard-products/variable-area-flow-meters/flo-rite-series-fr-acrylic-body-flowmeters/fr4000

I can always add oyster shell, if the finished PH is too low. (sold as chicken feed supplment)

My filter (2, 80 gall tanks) 1st, bottom feed gravel, top spills over to 2nd: slow sand

http://www.facebook.com/media/set/?set=a.161025670637561.41240.120212794718849&type=1#!/photo.php?fbid=160879627318832&set=a.161025670637561.41240.120212794718849&type=3&theater

album http://www.facebook.com/media/set/?s...4718849&type=3

[russ]

1) Approximately where is this farm - allows us to look up projected insolation - it is not 9 hours

2) The sand filter will do nothing for much of what you seem to be worried about in the water. RO efficiency depends upon pressure drop across the membrane - cheap household types are horribly inefficient (as in useless) and waste most of the water. More expensive and more efficient units use multiple membranes, more water pressure, water filtering to remove fine particles, often pH adjustment and a descalant.

[noone]

Armour on indeed.

First, let's settle on 1 measurement unit. Watt Hours. a 50 watt bulb, for 2 hours, is 100 watt hours Apply the same formula for every appliance, and then to the solar array.


If you have volt & amps, just multlply to get the watts (it's going to be close enough, lets not delve into Voltamps now)

Your crook pot (slow cooker) is 12V , 10A for 3 hours. That's 120 watts for 3 hours or 360 watt hours.

Your region gets (for this example I'l use 3 hours) _3_ hours of solar exposure. 200watts of panels.

The very most you can hope to harvest is 600 watt hours. Since you are using and recharging batteries, your efficency factor all in all , will be 50% of your panel x sun = useable energy. Harsh, but true. One good 3 hours sunny day, you can cook one pot. Or have lights for several hours, or a laptop.

Use PV Watts, or some other solar insolation tool to get the solar hours for your area:
http://www.nrel.gov/rredc/pvwatts/

Hi

As I said a 12 volt slow cooker may well be too much for many (others with enough battery it will be ok)..

Other 12 volt cooking appliances use FAR less.

I live in town amongst shops so get very little sun even in summer but I can STILL get enough to use a 7.2 AH AGM battery from a 50 watt panel to cook 3-5 meals in two good days of light stuff like meat for sandwiches and bacon and eggs.

I am limited by the size of my battery and lack of sun. Outside my place though and it is fine.

it is coming into winter here though so I will only get about one meal a day at home but it will still be great out of here..

I started experimenting for camping and later going off grid but like it enough I use it fairly regularly.

If I had average sun and a bigger (but still small) battery, even a decent size steak would still use less than 90 watt hours or around 7Ah. Small LiFePo4 batteries would be great for this (and will try them soonish).


I would bet that you could just hook up a 12 volt slow cooker to a 200 watt panel and leave it and it would be fine.......unless there is any voltage sensitive electonics in the cooker....something else for me to try later.

For a large family it may not be so good.

I would never use 50 watt light now off grid or on unless for a specific purpose. (yeah I know that was only an example).

I would use other ways of doing things first in may cases too....my washing machine is a camping type hand powered pressure washer.

To the OP instead of the reverse osmosis would something like this be useable?

http://www.rpc.com.au/catalog/water-desalination-distiller-purifier-solar-panel-p-3467.html