Date:         Sun, 2 May 2010 15:23:00 -0700
Reply-To:     "Mike \"Rocket J Squirrel\"" <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Mike \"Rocket J Squirrel\"" <camping.elliott@GMAIL.COM>
Subject:      Re: Solar Panel Mount -Flexible Panels?
Comments: To: Pat Sloan <pmsloan@SHAW.CA>
In-Reply-To:  <C20E43CF763043088BAC70B1B2FC378C@OwnerPC>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Pat Sloan wrote:
> It's really early days, but I've
> begun looking into options like microwaves, small toaster/convection ovens,
> electric frying pans, electric kettles etc, all of which would run off the
> auxiliary battery which would be charged by the solar.

Electric heating requires a buttload of power.

Let's do the math!

Say you've got a 600 watt microwave oven and want to run it for 10
minutes. 600 watts @ 12 volts is 50 amps. So after 10 minutes, you've
drawn 8 ampere-hours out of the battery. And say you also use it a
couple times more during the day. You're probably looking at 16 to 24
amp hours sucked out of the battery.

Electric skillets clock in at around 600 to 1000 watts. So that's
somewhere between 8 to 13 amp-hours per 10 minutes of operation.

One fried chicken dinner, a pot of Mr Coffee coffee, a couple microwave
meals, and you could easily use 50 ampere-hours in a day. Since it's
really not a good idea to discharge a battery too much, you'll want some
big batteries. And a way to replenish 50 ampere-hours back into the
batteries, per day.

Don't forget that your refrigerator will be drawing power all day and
night. And you might want some lighting and tunes in the evening.

I'm just saying that for efficiency, stick with propane. Solar panels
don't provide nearly the power we wish they did, and current storage
technology (batteries) simply can't compete in terms of energy density.

I personally run everything I can on solar. I have a couple 45W panels,
a good MMPT controller, and a 130 amp-hour Trojan deep-cycle battery.
I'm here to tell you that with the evening lighting (mostly LED and oil
lamps), soft music after hours, and running a vitrifrigo electric
refrigerator 24 hours a day, I can get the battery topped off before
noon on a sunny day. I doubt I could keep up with the added load of a
bunch of electric heating appliances.

I know I can get a couple weeks of cooking and heating out of that
little propane tank. I also know that two or three days of no sun would
completely deplete my aux battery. I'd have no confidence at all for
even a weekend trip if I knew I had to rely on the battery alone for
everything including cooking.

But, YMMV.

Damn I wish the Vanagonwiki hadn't gotten forever and totally lost. I
put a lot of work into the solar power pages, along with resources for
calculating how much power someone will need based on the equipment they
are planning to run.

Oh well, nothing is permanent.

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Westrailia: (Ladybug Trailer company, San Juan Capistrano, Calif.)
Bend, OR
KG6RCR