Solar PV powered hot water immersion heater?

[afd]

Hi,

I am in London (UK) and went through the whole process of getting a "green grant" for Solar Thermal HW tubes on my roof. However, it became clear that the 1200kWh produced would save only 2-5% of my gas consumption (£30 per year) and would cost me £2500 and the taxpayer another £2500 plus £6000 in feed in tariffs. I decided this is a huge waste of taxpayer money for a neglible carbon footprint reduction and that the only person benefiting was the installer who makes a shed load of money on the installation (clever installer got an exclusive contract with the local council!).

So, rant over with, I looked further into alternatives and saw a very simple idea - hooking a PV panel to an immersion heater.

I know that an immersion heater needs about 2.5kwh to operate at full whack and this would require a lot of panels. I am not going to buy a lot of panels. I thought I could buy 1 or 2 and feed maybe 0.3-0.4 kwh to the immersion heater to gently heat the water up.

Has anyone looked at this?

My question is really about how well an immersion heater can perform with low kwh inputs?

PS - I am not an electrician or plumber and am crap at DIY, so please be gentle with me!

Kind regards

Andrew

 

[TGor]

Assuming 100% efficiency (which its not) .35 kWh is = to about 300 KCal so it will raise 300 litres of water by 1 degree celcius in one hour or a 130 litre "normal" cylinder by about 2 degrees in one hour .. you will probably lose more than through the cylinder even if it's insulated .. plus would need an inverter as panels are DC & immersions are AC. Not such a good idea really and wiring it up is a professional job so would probly be negative geared for yonks.

"Its good to be green"
Kermit the Frog 1976

 

[afd]

Thanks for the well informed reply.

I think I saw somewhere an immersion that worked from DC current, but even so your figures make is pretty clear this is a poor idea.

It seems such a shame that the green payback is so limited. Sure, you can throw a lot of cash (mine and taxpayers) at the problem and get a small green saving (2-5%) but that is a drop in the ocean for what needs to be done.

I guess the real problem is that Solar PV panels are less than 20% efficient. When they get to 50%-75%, then we will solve the worlds problems. Until then, we're kidding ourselves with all this green stuff......

Thanks again

 

[migoplumber]

look at alternatives such as heat pump boiler air or ground. any pv's installed correctly will save you a little in the long time. dosnt mean the green costs are recuperated tho.

 

[TGor]

I guess the real problem is that Solar PV panels are less than 20% efficient. When they get to 50%-75%, then we will solve the worlds problems. Until then, we're kidding ourselves with all this green stuff......

Thanks again

I saw some solar PV "paint" at the Taiwan Institute of technology in Hinschu ... now that has got some potential.