I understand your goals. Those boys can answer the question on how hot the PVs get, from time to time I see discussion about heat control and effects of temps on the panels. If it turns out that the panels run cooler than the water will get, a simple diverter valve in the setup that will measure incoming water temps then cut water flow away from the panels, and that will allow drainback into a storage system to get the water in the system off the panels, would do the trick. Ideally you’d do this as two separate loops, one to the PVs and one to dedicated hot water panels. This would let you use the whole system to bulk charge the water, then the dedicatated water heating lines to finish the job.
I can also see this as having another advantage, you’d be able to pump hot water under the panels when they are covered with snow in order to get power production up right after a snow. Might be worth it for just this, if nothing else, would save a trip to the roof.
How is the efficiency of the grid tie panels vs 12/24v panels?
I don’t know how the efficiency compares directly, but some of the stuff I’ve been reading says that there is more power produced by the grid tie systems. I don’t know if that is because the panels in a grid-tie system are better, or if it is because the electronics needed to produce the appropriate clean 60 cycle AC is more efficient - I suspect it’s more the latter, as you avoid the entire mess dealing with the battery bank. I haven’t actually heard that there is an actual difference in the panels themselves.
For the on-grid user, everything I’ve heard seems to suggest that it is better to go grid tie, the only thing that bothers me is that the current designs don’t work if the grid goes out. IMHO unless you have a very unreliable grid connect, I don’t think the power-failure issue is enough to justify going to the expense and hassle of putting in and maintaining a battery bank, but it is something that would really annoy me if we had a long outage with a bunch of unusable juice sitting on the roof… I’d want to see if there was some way to have a small setup that could “kick-start” the grid-tie system so that it would function like a generator - something like either a UPS or a small (say ~1kW) gas generator - It would only work during daylight obviously, but might be a way to keep the critical stuff going - i.e. keep the freezer cold and run the furnace long enough to keep the house warm…
The current benchmark seems to be $4/watt. I have found new panels for slightly less than this, but not much. Nanosolar is claiming $1/watt, but it’s going to be a while till we see these available to the common man.
I had a solar guy come to my house and do an assessment.He claimed that while the printed type (nanosolar) does have a bright future, that type of solar requires much greater roof space. There fore it will be a decade before its good for most residential apps. . Could be a sales pitch. However I am still considering pv for my home.
I haven’t compared the efficiency of the Nanosolar cells as they are really still in development. I have been thinking of putting up a couple of the currently available panels to play with. I would be happy to get something like the refrigerator off the grid. I figure at $1/watt, I’ll eventually cover the house, garage, deck, half the back yard, part of the driveway.......
I haven’t compared the efficiency of the Nanosolar cells as they are really still in development. I have been thinking of putting up a couple of the currently available panels to play with. I would be happy to get something like the refrigerator off the grid. I figure at $1/watt, I’ll eventually cover the house, garage, deck, half the back yard, part of the driveway.......
Chris
Good point ,although all of that would need to be unshaded and facing south. I suppose if it was dirt cheap ,east and west also. Maybe the Chinese will take the tech, and have it at 50 cents, Still here in CT most of our problems are transmisson related.18 cents a KW and probably going up in july, The state currently pays have of the cost of PV systems.
Half? Wow! I think the last time I checked, the state of MD will pay 20% up to $3000 and that’s it. It also has to be prequalified, approved, permitted and inspected. I’m not even sure it’s worth it for all the red tape I would have to go through…
BGE is charging us about 14 cents for production and transmission and also about to go up. TOU is a joke; only drops to 10 cents. I thought deregulation was supposed to be good for the consumer?
I have been also thinking about the combined water/electric PV. I am off grid and have 24 panels that get pretty hot and am trying to come up with a way to remove that heat using an exchanger on the back.
I have been also thinking about the combined water/electric PV. I am off grid and have 24 panels that get pretty hot and am trying to come up with a way to remove that heat using an exchanger on the back.
Here is another one: http://zomeworks.com/ I use this company’s passive tracker for my panels and they have worked great over the past 7 years. Another product they have is called the “Architectural Cool Cell” and it is under the R&D;link. I have been in the hot 100 degree heat in the summer and stepped into their Arch. Cool Cell test building and was cold. It was pretty amazing.
I didnt get a chance to look through all the posts but do know a few firms actively working on that very topic. Combined PV and water heater, or think of it as a water cooled PV panel.
I saw a system at the Solar store in Waitsfield, Vermont last week. It’s pex tubing run through metal brackets directly under standard metal roofing, with flexible PV panels optionally glued to the metal roofing. Presumably nowhere near the efficiency of a glazed panel, but it looks just like a normal metal roof.
