Solar panel heating Help!

[Solar_Stu]

Hi there,

First things first, I’d like to say this looks to be a great forum. There are some very interesting topics on here, and some very clued up people giving out priceless advice. Hopefully I’ve come to the write place.

I am currently in my final year at Manchester Metropolitan University studying for a degree in mechanical engineering. For my final year project, I have been given the task of coming up with some kind of back up system for a household immersion heater. This system must “green” powered using an array of solar powered photovoltaics (PV).

In the aim of getting a good mark, I’ve decided to look into installing a small DIY system to my home for testing purposes. But have come across a major stumbling block as I can’t seem to find a heating element or device that can be powered using such a low wattage give off from a small solar panel. I’ve searched high and low but have had no luck. I was wondering if any of the geniuses on here could point me in the direction.

Any help would be very helpful and much appreciated,

Thank you,
Stuart

 

[numpty with a crowbar]

bog standard domestic solar panels will only produce something around 12-24 volts. So unless you are prepared to use a 3-4000 watt inverter and a couple of massive deep cycle batteries and wire it up to that then you'll not get enough voltage or current to get a standard imersion element doing it's job....

You could try one of those little things that plugs into a car lighter socket that keeps yer cup of tea warm? put the wholoe unit in yer tank and plug the plug onto a solar panel

Or you could try wiring 10 24 volt panels in series and see what melts / sparks.

Then once you've tried that, maybe paint a radiator black, mount it in a frame, out a layer of glass in front of it, screw the lot to your roof and connect the in/oout pipes to yer hot water tank - it's the only way you'll get even lukewarm water....

 

[Taylortwocities]

Well, I dont have a degree but I think you are taking the wrong approach.

You'd need a very large array of photovoltaics to generate 3KW of power -which is what an immersion needs.

Just an idea but how about you take the water route.

Black board on roof with polypipe zig zagging across the black backing. Then u need to plumb it into the hot water tank, maybe with some sort of valve, pump and sensor. Fill it all with water so that hot water from the roof pipe goes into the hot water tank when the temp of water in the tank is cooler than water from the roof.

I feel a BsC coming on.

Edit: Numpty, I hate your quick fingers..

Edit 2: I thought you clever students knew all about Google - llok waht i found in .000000000001 of a second http://www.howtogogreen.com/2005/07/hot-water-from-sun.html

 

[Solar_Stu]

i only want to do this n a very small scale so something like a "car lighter socket thing that keeps yer cup of tea warm" is worth looking into. cheers "numpty"

 

[Solar_Stu]

i've checked out the water heater but its over 200watt. im looking for something under 100watt 12v
Thanks for your quick responce.

 

[plugwash]

heating water using PV cells is idiotic, if there is any way you can get out of this f*cked up project and get something more sane do so.

 

[breezer]

i've checked out the water heater but its over 200watt. im looking for something under 100watt 12v
Thanks for your quick responce.

average 12v solar panel output 1 watt cost around £10 if you are lucky

you want 100w

100 x 10 = 1000

give up now its not going to happen. sorry

 

[Cremeegg]

More for the plumbing forum this comment but evacuated glass tubes for solar hot water are good and getting better the more the cost of electricity goes up. One customer reckons to save a good 50% off their previous immersion heater only use for HW. As others have said PV for water heating is a complete waste of effort even thinking about it.

 

[breezer]

More for the plumbing forum this comment but evacuated glass tubes for solar hot water are good and getting better the more the cost of electricity goes up.

trouble is the op said

............... For my final year project, I have been given the task of coming up with some kind of back up system for a household immersion heater. This system must “green” powered using an array of solar powered photovoltaics (PV). .................

 

[viewer]

Couple of thoughts; the requirement is for a back up system, i.e. not a replacement or continual support system. Best check the wording with the tutor - badly worded assignments are not unusual. This should mean it can be used when the system fails and so is either a huge array of cells or an accumulator system. You can use batteries (look at new pumped liquid systems or capacitors). If you want a good mark, look for the frontiers of science/technology in your literature review and discussion. Nothing says you do it full size or use the ultimate technology so try to make a model. At the low voltages you can use a wire in the water to simulate an immersion heater. The maths should be easy.
HTH
V

 

[Chris.J]

I guess his Tutor knows that converting the suns energy into electricity to heat the water is less efficient than the "water solar panel" method (for a given physical size of panel), and also much more expensive.
But that does'nt prevent him investigating what is, in effect, putting a suitable resistor in the tank, measuring what it produces, and therefore calculating the area of PV panel required to substitute for an immersion heater. He will also have to measure/calculate tank losses as part of this, quite interesting.

 

[sturharv]

Why are you focusing on PV, whats wrong with having 'green' solar thermal collectors for the production of hot water??

 

[TicklyT]

Constrained to using photovoltaics to 'power' your collector, how about using the photovoltaics to power a solar tracker controlling a thermal collector array?

Or using the photovoltaics to power a heat pump?
I'm thinking along the lines of turning a small domestic fridge 'inside out'....

Or one of them little fridges that hold about four tinnies, run on 12V DC and are capable of heating or cooling according to how they are connected....

 

[bernardgreen]

Or one of them little fridges that hold about four tinnies, run on 12V DC and are capable of heating or cooling according to how they are connected....

Ignoring the cost of the equipment this is the basis for an "efficient" way.

Peltier effect heat pumps fitted to the hot water tank with a source of low grade heat fed to them.

Peltier devices are solid state devices which are similar to heat pumps on a small scale with no moving parts. They have two plates and when a DC current is applied they move heat from one plate to the other.