Bit of info please.

[Kimba]

Hi all, can someone please tell me will two x 80 watts solar panels and four x 75 AH batts with a 2000 watt inverter run 1500 watt electric hotplate for about 2 hours a day.

[Sunking]

This is easy, NO WAY. Depends a bit on your location but try a 1500 watt solar panel, and 1875 Amp Hour batteriy at 12 volts, or about 24 of those 75 AH batteries.

[Kimba]

Ok so that gives me a scale of things, I think maybe if I mention my need and that is to be-able to boil water in a pan, is there a dc type method other than a tiny kettle to boil water.

I have looked around and most AC electric hotplate seem to be in the 1000/1500 watt area.

[Sunking]

How much water and what time of day?

[russ]

Hi Kimba - Welcome to the forum!

First, Sunkings question about quantity and time of day are most important and then -

1) Where are you located? That shows how much sun is available.
2) Solar thermal panels can get you close - my hot water tank is in the 90's (C) during the summer.
3) A solar concentrator like a solar cooker might fit your needs better and that would be maybe a few % of the cost.
4) Is your requirement everyday?

Russ

[Kimba]

Hi and thank you.

I am located in the United Kingdom, England.

The amount of water will equal about 10 litres a day which must reach rolling boil, the time of day can be any time.

Solar concentrator/solar cooker no good here, I should have stated my location soz.

My requirement would like everyday but can do every other day.

So far I have half of that system in my first post built.

[russ]

Like Sunking pointed out - you are in deep doo doo!

Better keep your mains supply as anything else will be horribly costly.

[Sunking]

The amount of water will equal about 10 litres a day which must reach rolling boil, the time of day can be any time.

You are SOL, keep the electric company connected or use LP or NG. It is your only real options.

[russ]

You could use solar thermal panels to heat the water as much as possible and finish toe job with another heat source such as Sunking mentioned.

My solar thermal panels generally maintain the tank top at 90+ degrees C all summer with the bottom half at 70 to 80 degrees. I am somewhat to the South of you.

Vacuum tube type panels will heat the water better than the flat plate type that I have.

[Mike90250]

If you are just trying to pasteurize water, ther are charts for different temps and times. Say 3 hours at 150F, 2 hours at 170F, 30 min at 195F - but look up water pasteurization and be sure.

You can use a flat plate collector to pre-warm the water, and evacuated tube to really get it toasty, even on a cloudy day.

[Kimba]

Alot to think about this has been quite helpful thread for me and yes my needs are to make water safe and also to cook rice/pasta so on.

Back to heaters I came across this hotplate it is 400watt I'm sure I would get a few hours a day from this yes?

Here is pic

[Sunking]

Back to heaters I came across this hotplate it is 400watt I'm sure I would get a few hours a day from this yes?

Not with a 160 watt solar panel system in the UK. Maybe 1 hour in summer, a few minutes in winters. However I do not know how much water you intend to bring to a boil, but like say 2 liters, it will take quite a long time to bring the water to a boil, and with your battery it would be dead before th ewater comes to a boil.

It is all about watt hours used, and your location.

Watt Hours = watts x Hours. So if you ran that 400 watt hot plate it would consume 400 watts x 2 hours = 800 watt hours. Ok for a battery system, due to the inefficiency, you have to generate twice the amount of energy than what you use. So for this 400 watt hot plate to run 2 hours, you need to generate 1600 watt hours

Once you know what the total watt hours a solar panel wattage must generate in a day, it is easy to find the solar panel wattage need by factoring out the Sun Hours for your area in winter. For you in the UK the range is between .9 and !.2 Sun Hours.. So the solar panel wattage needed to generate 1600 wh = 1600 wh / 1.2 h = 1333 watts.

As for the battery you would need a 500 AH at 12 volts. One huge battery.

The moral to the story is you cannot use solar electric for things like hot plates, cook tops, electric hot water heater, air conditioning, ovens, dryers, coffee pots, etc. The reason is because you cannot afford or justify it. To buy 800 wh from the electric utility cost is about 10-cents USD per day, $3 per month, $36 per year, and $180 for 5 years.

To do this with solar PV to generate 800 usable watt hours for you would cost about $4500 USD. After 5 years you have to replace the battery at a cost of $850.

So unless you intend to spends thousand of dollars to generate 10 cents of electricity per day, you need to do something else like be happy electricity is extremely cheap and stay connected. Or use Liquid Petroleum Gas or Natural Gas. None of those will send you to the Poor House.

[Kimba]

Thanks Sunking I think then I shall have to settle with my 100 watt 12v kettle that takes 30 mins to boil but at least it is able to create a rolling boil and so far has never taken cell on regulator into the red.

[Mike90250]

You want something that has the heating element directly in the water. Not a pan on a hot plate, but an electric kettle. A rice cooker is good, they don't use 1,000s of watts, just a few hundred watts, to keep the rice cooking, not boiling.

There is also a way to use plain sunlight shining on water bottles, and the UV is enough to sterilize the water.

[Kimba]

Hi, the 400watt hotplate arrived today I can report that it rolling boiled water within 10 mins and I left it running 20 mins in all, there was no drain showing on both inverter or regulator, the system was 1x80watt solar panel and 2x 75 amp batts.

The other solar panel arrived few days ago as well but my brother is welding me up some brackets so I can mount and flip the panel to face morning sun and then afternoon sun.

I'll test it some more when I find the time.