Using 12V DC Source for Heating, Without Inverter

No!

You'd be better off just trying to cook your food in the direct sun.

500 watts at 12v won't even heat water very well.

To get a decent rate of heat up, you would need at least 1,000 Watts of heat, obtained by passing the electric current through a suitable resistance wire. With only 12 Volts available this means a current of about 83 Amps - a pretty hefty current. A well insulated container would still get there with only 500 Watts. I would suggest that if you are patient, and design you cooking vessels wisely, you could manage some cooking on 500 watts.

Technically this is possible but not at all practical. The portion size I expect that you'd be limited to will be comparable to the cup cake size portions of the Easy-Bake Oven. This toy originally used two 100 Watt incandescent lamps to cook tiny low temperature cake recipes. You will certainly get better results directly cooking with the sun.

You can buy 12 volt appliances, like grills, from various places. Here's a link to amazon for 12 volt grills. You might want to use your solar panel to keep some auto batteries charged, and use them for your cooking.

http://www.amazon.com/s/ref=nb_sb_ss_i_0_13?url=search-alias%3Daps&field-keywords=12+volt+grill&sprefix=12+volt+grill%2Caps%2C259

I stand corrected.

I did a little further digging and the small grill takes 540W to operate. That's just a little more than the solar panel can produce directly but I guess it can be done if a battery provides the extra current during cooking. One must still be very frugal with the available power though.

I think the only way this can be viable is with battery assist, and a small family.

Hi

Yes, it is possible.

The thing is you will need the panel to match the appliance, that is with enough AMPS, so you really need to use a larger panel than the watt rating would suggest.

Despite what just about everyone on the internet says, 12 volt cooking appliances work well (there are limits but for many people they may well be the way to go).

Some 12 volt appliances work off as little as 65 watts (12 volt sandwich makers) but they would take too long...something like 15 minutes for one toasted sandwich.

12 volt stoves are much more practical but still may be a bit slow for a lot of people.

I have actually used a 12 volt stove to cook a meal directly from a single solar panel.

Mine uses 10 amps at 12 volts, to get a panel with enough amps I had to get a 12 volt 11 amp 200 watt panel (actually 18 volts) but since these are simple resistive loads the over voltage seems to not matter (also I use a 15 meter power lead so voltage drop may be a factor). In any event, it works for things like thin slices of meat for sandwiches, I even think I can get it to cook a (very) small loaf of bread. (used too much water when I tried recently). 12 volt stoves are slower than normal power but it may actually be BETTER with solar than from the normal cigarette lighter socket as they take a while to warm up but then should cook fairly well and can be just left on in sunny locations.

I have a lot more experimenting to do, a 200 watt panel was a lot cheaper than a 240 watt one but I suspect a 240 watt panel would have been a lot better for me.

I also have a couple of 12 volt frypans, from batteries these work very well and quickly (small though...will cook a small meal for one or two at a pinch).

One of these fry pans needs about 170 watts so is not anywhere near hot enough from my 200 watt panel (again for MY purposes it is about a 130 watt panel max). The other is about 150 watts ....it MAY be just ok but so far does not quite get hot enough. I believe it WILL work with a larger (240 watt??) panel but that has to wait till I can afford one.

Having a 12 volt fry pan work is my goal as it will meet just about all MY cooking needs and during the day, will mean I do not need anywhere near as big a battery PLUS can use a small battery at night charged from the panel when not cooking.

Hope this helps.

Neil

Real, practical reply to my comment. Thanks Neil.

You know, it is far cheaper to produce electricity from Solar through PVs, than to store it. The storage batteries also have a finite life when compared to solar PV panels, which work for 20 years or more, with just need to wipe off the dust.

I thought, that without storage, atleast, we should be able to cook while the sun shines (Make hay while the sun shines is an adage perhaps similar to what I have in mind).

If some of the friends in the forum say that resistance heating is not the best, if there is a better way, then it would be more economical to use it - provided it is not very much more costly than the resistance heater.

Hi

As to 12 volts cooking generally,

A lot of people will tell you you can not do it and the like. Most will have never used a 12 volt cooking appliance and many of those who have have only used them from a car cigarette lighter socket. They use too much power really for a car 12 volt system. Truckers are more likely to be happier with them.

Because 12 volt cooking appliances got a bad reputation years ago (before solar and maintenance free batteries), people still think that and the myth gets spread to the point thats what most believe.

And of course, for things that take hours to cook, 12 volt probably IS still a waste from a battery for most but for things that cook quickly (like fry pans), 12 volt is great from batteries now.

12 volt frypans (and some other 12 volt cooking appliances) only use about 20 watt hours to 50 watt hours to cook a meal and do so in not much longer time than a normal frypan....the limitation is the power and size...not if it works or not.

As to size they are very efficient really and more so if you use the lid and will still fit something like a decent size steak. Now regards power, these days with AGM and LiFePo4 batteries, a small battery will easily do 3 smallish meals a day for a person and be recharged from something like a 50 watt solar panel...a 20 amp hour battery should be fine for a person (I use a 7.2 AH AGM battery for part time use...I am killing the battery but still works well and the battery was cheap). I suspect LiFePo4 batteries around 10AH and up would be great for use with a 12 volt fry pan and a small solar panel.

As for using a 12 volt appliance directly from a solar panel, I expect this to be common in a few years time but right now, I may be the only one on the planet dumb enough to do it. A panel big enough to cook in real time (200 watt and up) is still pretty big though easily manageable. Once more efficient solar panels become available (and half the size), this may be the end of cooking bills for many.

In the end, I will be using...

a 12 volt solar panel to cook directly for things that take their time in the likes of a 12 volt stove.

Same for things that cook quickly in the day time with a fry pan.

Use the fry pan from small batteries at night and cloudy/wet days.

You are definitely not dumb. On the other hand you are a pioneer. Keep it up.

In India, where I am from, PV panels (Good ones not from China, but made very much in India) cost around INR 60 per watt. That means a 200 watt panel, that occupies approximately half a square metre, would cost INR 12000/- A Lead acid battery of say 100 Ah, would cost INR.8,500/-. A charge controller to connect the PV panel to the battery would cost another INR 1200/-. The wiring, which should atleast be 1.5 mm sq. would cost another INR.1500/- making a total of INR.23,200/- As you said, we could use the power stored to cook in the night time also.

Again, as you rightly said, in a few years to come, solar cooking would become a norm, rather than an aberration.

Good luck. I will, in the meantime try to acquire 12 V DC heating devices, which are just not available off the shelf. With great difficulty, I was able to get a 400 mm sweep pedestal fan working on 12 V D.C., and I have been enjoying it during day light hours, say from 9 AM to 5 PM,(All without any battery back up) and a cause of envy of my neighbours during power outage regularly from 12 Noon to 1330 Hours. I hope I can grasduate to cooking with Sun, with help of friends like you.