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Old 03-23-2015, 06:57 AM   #21
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lion's are great battery's i plan on changing out when my fla's are dead. hope the price keeps droping it would cost over 2500.00 today. ouch
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Old 04-01-2015, 01:18 PM   #22
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30W 30 Watt Solar Panel 12V 12 Volt Battery Charger Off Grid RV Boat | eBay

I was looking at this solar panel ad on eBay thinking a few of those on the roof could supply all my electrical needs. Comments?
Is this a good set up?
http://www.costco.com/.product.10011...0_April-Mailer

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Old 04-01-2015, 02:27 PM   #23
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Actually, it's better than I expected it to be when I saw it was a kit. But like all things, you make sacrifices when you go for kits. A few comments:

* Solar panels are 100W each. They're fine... but you can get much larger sizes now for short money online. Larger panels don't just give you more juice - they also give you a lot more margin for cloudy / winter days.
* Charge controller is straight PWM rather than MPPT. It's actually a decent brand, just not the latest tech. Xantrex's C40 (next model up) is only a little more $ than the C35 and is MPPT which helps you get the most out of your batteries/system.
* Inverter is pure-sine (good) but has plugs rather than direct-wire support. It's going to be extra work to wire if you also want to be able to run your devices off shore power.
* Inverter is only 2000W. Maybe that's all you need but I'd personally go with 3000W, which again, bought separately, is only like $40 more on Amazon right now.
* If you want shore power you still need the AC->DC charging component. There are inverters that do this internally. This isn't one of them.
* It doesn't say how long those cables are... but they sure look short to me...

Your mileage may vary and only you know your requirements. But me, I'd pass. This will totally work, but you'll get more functionality and mileage out of slightly better versions of each of these components. I personally think this kit is best for somebody who just wants to switch their fridge completely to solar, and has no other plans.
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Old 04-01-2015, 04:24 PM   #24
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If you're set on electric water heating, it could help things immensely if you consider a high voltage battery bank -- to the point that the heater can be run directly from the batteries without any inverter, for example. This is very much into the realm of engineering it yourself..

As an example, consider a battery bank at 96+ V dc paired with the Eemax SP3512 point-of-use instant electric heater. It's not too far-fetched to think that heater could be modified relatively easily to run from a dc source. The Home Depot product page indicates it'll give 35F temperature rise at 0.7 gpm, which isn't much, but thought experiments have to start somewhere. Anyway, 3.5kW from 120 Vrms is 29 amps so it looks something like a 4.11 ohm resistor. Put that across a 96 V battery bank and you'll draw 23.4 amps or 2.2kW (note that already we're getting less temperature rise and/or water flow than advertised). But 23 amps from a battery bank is nothing. Losses in the batteries and wiring would be kept relatively low, and most of the power would be delivered to your (luke-warm) water. A 5 minute shower would consume 0.186 kWh, and if you add 15% for losses (probably too optimistic) that's 0.214 kWh. Rounding up a little more, that's about 1 of maybe 5 daily hours of useful sunlight falling onto a single 235 watt panel.

From my perspective that's a very meager supply of warm water, but maybe it's enough for your purposes. At this scale it seems doable.

One other note: if heating water or the interior space is a big thing for you, it might be time well spent to look at using the sun to heat the water directly. Storing energy via heated water isn't so different from storing electricity, and if ultimately heat is the energy form you want anyway, you can gain some efficiency by not converting to and from electricity.
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Old 04-01-2015, 05:26 PM   #25
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More than "some" efficiency. PV collectors are lucky to see 30% efficiency, while hot-water collectors run 60%-80%. They're also dirt cheap - you can DIY your own with some copper tubing and a plywood box, although I think it's worth the cash to buy a good collector. This doesn't count the efficiency losses from the inverters, wiring, batteries, charge controllers, etc.

Not saying solar electric doesn't have its place... But if you're serious about wanting to heat hot water from the sun, it's probably worth plumbing for that. A very simple system can be done for the same cost as a good PV panel and you're going to get more mileage out of it.

nat_ster, when are you going mass-market with your 35-heat-source stainless hot water tank beastie?
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Old 04-01-2015, 05:33 PM   #26
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More than "some" efficiency.
OK, sometimes I understate.

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nat_ster, when are you going mass-market with your 35-heat-source stainless hot water tank beastie?
Maybe we just need to set up a kickstarter campaign for him and then let him know about it after it has smashed its funding goal and the whole world is waiting to get their own? It needs a good name, but I'm terrible at names. If it had been all up to me my kids might have been named "hey you," "not you," "the other one," etc.
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Old 04-02-2015, 09:17 PM   #27
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Its interesting that we have so many opposing views each backed up by theoretical figures. We're all in the same boat. We all want the cheapest system but can't risk money on experimentation because we're all paupers.

I was just toying with the idea of a wind power system.
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Old 04-03-2015, 12:10 AM   #28
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There is no question to me that the cheaper way to heat water with solar power is directly though panels designed just for that. Let the PV panels make electricity and the hot water panels make....hot water!

I think these look interesting

http://www.amazon.com/Complete-Panel.../dp/B0041XXSJW

And probably cheaper and easier than designing your whole electric system around hot water!

Just my .02
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Old 04-03-2015, 06:47 AM   #29
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Problem is that while heating water directly from the sun works well during sunny afternoons, the water will be cold in winter and at night.
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Old 04-03-2015, 06:50 AM   #30
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i dont like the hookup to the w h. should enter the bottom and exit the hot water feed. also with s h w you need a good size storage tank 40 gal. min. and a place to put the tank.with a few changes it would do. i would use a heat exchanger so i could use year round. good find charles thanks for the link. i got a gas on demand from sportsmansguide and it works great. i put it in my bath and showered for over 3 months on a single grill tank. uses 2 d batteries to ignite.
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