EcoRenovator - View Single Post - Dump the plumbing and use PV to heat water?

Xringer · 12-29-09, 01:48 PM

This simple technology (DC heating of water using PV panels)
has been tested for a few years by the government.
BFRL: Solar Photovoltaic Hot Water System

And now that PV panels are available for under one dollar a watt,

http://ecorenovator.org/forum/solar-....html#post5341

it just might be cheaper to skip all the plumbing hardware and just wire some PV to a heating element in your HW tank.?.

I'm trying to get some of those cheap panels to try my hand at making some hot water.
I'm going to start with 4 panels, into a 75 ohm resistor, making about 240 watts of heat for my 76 gallon hot water storage.

240 watts per hour = 819 BTUh. Five hours of good sun, could mean 1.2 kWh or 4094 BTUh dumped into the tank daily.

I'm not sure how much that would help keep the oil burner from coming on,
but if the heat-loss is close to 819 BTUh, it could keep the tank coasting during the sunny part of the day at least.

I like the idea of cutting out the middle-man inverter (and/or battery) losses.

And the idea of just using a 75 ohm resistor and some PV panels is very attractive to the purist in me.

Years ago, I had a good working solar hot water system working. 3 big Novan collectors on the roof, made lots of hot water!
But, after about 10 years, the plumbing starting going. The city water supply eats copper. And loves tanks and heat exchangers.
The system worked well for about 15 years and was removed after a few years of collecting dust. A new tank and exchanger
was too costly and I knew we would be needing roof shingles again before too long.

If my guess is right, a PV driven hot water system, could last 30 years and still be working. Plus, it's going to be very low maintenance, if the parts count is kept low.
Less things to go wrong, the longer they last.

12-29-09, 01:48 PM	#1
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Dump the plumbing and use PV to heat water? This simple technology (DC heating of water using PV panels) has been tested for a few years by the government. BFRL: Solar Photovoltaic Hot Water System And now that PV panels are available for under one dollar a watt, http://ecorenovator.org/forum/solar-....html#post5341 it just might be cheaper to skip all the plumbing hardware and just wire some PV to a heating element in your HW tank.?. I'm trying to get some of those cheap panels to try my hand at making some hot water. I'm going to start with 4 panels, into a 75 ohm resistor, making about 240 watts of heat for my 76 gallon hot water storage. 240 watts per hour = 819 BTUh. Five hours of good sun, could mean 1.2 kWh or 4094 BTUh dumped into the tank daily. I'm not sure how much that would help keep the oil burner from coming on, but if the heat-loss is close to 819 BTUh, it could keep the tank coasting during the sunny part of the day at least. I like the idea of cutting out the middle-man inverter (and/or battery) losses. And the idea of just using a 75 ohm resistor and some PV panels is very attractive to the purist in me. Years ago, I had a good working solar hot water system working. 3 big Novan collectors on the roof, made lots of hot water! But, after about 10 years, the plumbing starting going. The city water supply eats copper. And loves tanks and heat exchangers. The system worked well for about 15 years and was removed after a few years of collecting dust. A new tank and exchanger was too costly and I knew we would be needing roof shingles again before too long. If my guess is right, a PV driven hot water system, could last 30 years and still be working. Plus, it's going to be very low maintenance, if the parts count is kept low. Less things to go wrong, the longer they last.