diy solar

diy solar

Compete noob post - where do i start?

Man, I have a ten-metre hose to the shower. On the ground. In July and August, I bury more than 80% of it or it gets unbearably hot.

The feasibility of this will highly depend on your location/local climate. OP is in the UK, so this won't really be an option except for maybe a week a year or so.
 
As to the hot water heater, there are the factors of cost involved.

You said your daily consumption was about 500w, so you splurge and get a 1000w inverter, just to make sure you've got enough. Now you need your 50/mm2 (1/0 AWG)wire to connect it up to the 12v battery system in your van. Then you need a 120a breaker and all the solar you can physically fit on the roof. Not horrible

OK, so now you buy the shiny on-demand electric hot water heater and it only draws 1200w of power, but you still need the 500w for everything else that's running, so now you have to spend the money for a 2500w or 3000w inverter. Ouch, but you can swallow that if you have to. Now you have to sell a kidney for the 300a fuse and the 250/mm2 (500kcmill) copper wire and lugs to feed it! That's a 20-ish mm diameter wire to run! OUCH!!!

You would be MUCH better off getting one of the propane on-demand heaters and just worry about powering a water pump rather than trying to wire a 3000w inverter into a 12v system.

As to the panel figuring, with your area you're only going to get half the rated power on average at best. Add in that you'll only get about 3-4 hours of good sun and you'll lose about 20% by not being able to aim them toward the sun and calculate with that. The math should go something like (Panel Watts X 1/2 usable X 80% sun angle X 4 hours = Watts produced per day) so go from there. You're biggest limit to how much panel you can use is the physics of how many panels you can physically bolt to the roof. You really can't generate too much power so go hog wild.

Since you're starting from scratch, jump straight to Lithium if you can. You'll get the best usable watt/hours per kilogram with those over any other type.

You'll need the correct type of DC-DC charger to get your alternator to talk to a Lithium battery so you can get the proper voltages to it.

I'm sure there's more but that gets you started. First thing: Power Audit! Second thing: Measuring tape and panel dimensions to figure out how much you can stick up there. 3rd thing: rough plan your system. 4th thing: Come let us take a look to figure out what you missed (because we've ALL missed something our first couple go-rounds. :)
 
I have to say you now have me thinking again about diesel water heaters ( I would rather avoid having gas in the van) but from what I gather these are noisy, big and chunky. A solar shower might be an option but it just means another place to top up with water (and on the roof?) and I was also still considering a recirculating shower system.
Have you considered an on-demand, indoor, propane water heater?
 
I have to say you now have me thinking again about diesel water heaters ( I would rather avoid having gas in the van) but from what I gather these are noisy, big and chunky.

Oh, as for those, they're just a diesel parking heater (you can google that) with a heat exchanger strapped onto the exhaust. I use 2 of those diesel heaters at my camp and they have their pro's and cons.

Pro's: Run on 12v DC and only draw about 1a/12w when up and running
Use very little diesel (my first one in deep winter used 48l running full blast for a week straight)
Will heat up even a halfway insulated space to HOT right quick!
Cheap! Best $120usd I ever spent on that place!

Con's: Require diesel
The fuel pump has an annoying ticking sound
Need to be opened up and cleaned out after running prolonged periods of low loads (not difficult, just a little messy and I'd be happy to email you a step-by-step with pictures)
Use about 10a/120w for the first 5-10 minutes while it gets fired up
Have to run 3 pipes (Intake, Exhaust, and heat-to-you)

If you decide to look into those, hit Youtube for "diesel parking heaters" and see how people have mounted them. It may just solve both your heating AND hot water problems, and you can always mount the diesel tank outside and just run the fuel pipe in.
 
I generally disapprove of using electricity for heating water in a limited capacity system, but if you are really only going to use a 1200 watt heater for 5 minutes, that is no big deal.

You would need a 1500 watt inverter, which is not that big.

1200 watts times 1/12 of an hour is only 100 watts. Round up to 150 watts to be conservative. That only represents less than 15% of a single 100 amp hour battery.

I don't see a problem with these numbers. I do wonder how effective this 1200 watt heater will be. How much water will you waste running it waiting for it to get warm? (I'm guessing that you might waste as much as you actually use.) How warm will the water get? (1200 watts is very low for an on demand water heater, so I would expect its ability to heat water is marginal.)

Another alternative is to use something like the Big Kahuna and either fill it with water heated on the stove, or use a sous vide to bring the water to the temperature that you want. The big advantage is that you will not waste water and you will use less electricity (provided you insulate the water container).
 
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