Instant water heating using solar

SamD

I want to understand how I can use solar panel for instant heating of 1 gallon water. The 1 gallon water should be hot in say 30 mins. 

How should I set up the system preferably without a battery? 

Advice from the experts will be highly appreciated. 

dennis461

I figure you need minimum 665 watts, at 100% efficiency for entire process.
So, maybe double that number to allow for losses in panels, energy conversion, heat losses of water container, etc.
You did not mention actual temperature rise you are looking for, are you starting with ice water ?

Let me know if I guessed closest to your Final Answer :-)

Photowhit

SamD said:

I want to understand how I can use solar panel for instant heating of 1 gallon water. The 1 gallon water should be hot in say 30 mins. 

How should I set up the system preferably without a battery? 

Advice from the experts will be highly appreciated. 

As Dennis has eluded to there are a LOT of variables!


So the basic info you need to figure out are;

2.42 watt required to raise 1 gallon water 1 degree

Starting temperature of the water.

Desired temperature of the water, boiling 212, hot shower 110-120, temperature water will burn your hands 140-150.

Solar panels in direct sunlight angled at 90 degrees to the incoming sun produce about 75% of their panel rating (a 100 watt panel can be expected to produce 75 watt in normal conditions, more in very cold, less in very hot)

How much heat will be lost in your container, an insulated water heater loses heat very slowly, an aluminum open container will lose much of the heat as you are heating it.

If you have more info we can give you more info. Solar doesn't do instant and heat very well, suspect you would be happier with gas... but I don't know enough about what you want to do to say that definitively.

BB.

2.42 watt*hours per gallon per 1 degree F.

Note, that can be 145 watts for 1 minute or 2.42 watts for 1 hour.

If you do it with solar thermal. High noon sun is 1,000 watts (roughly 3-5+ hours of sun per day, depending on location, seasons, weather).

Heating water can be around 50% to 80% efficient with solar thermal.

Solar electric panels are around 15% or so efficient. You need more square feet or meters with solar electric.

-Bill

jonr

I agree, about 800 to 250 watts, depending on how hot.    There are some interesting controllers that use fast PWM to directly connect a PV panel to a heating element - while roughly maintaining MPP.

Estragon

As Bill points out, using solar directly to heat water is much more efficient than using PV. I used a simple camp shower for years. It heated ~3gals in a couple of hours with just basically a bag laid out in the sun. It could be done faster with a pretty simple system. On my to-do list is an outdoor shower using a coil of back poly pipe as a collector.

If you need to get to boiling, there are concentrator setups to do it that will be simpler, cheaper, and more portable than a PV system to do the same thing.

jonr

On the other hand, if you have to deal with freezing, a pump, controller, etc, then PV might be the simpler and cheaper.

oil pan 4

Use fire.