Solar Hot Water system?

[bebster]

At today's fuel prices, I'm seriously considering using solar for domestic hot water heating. Does anyone have any experience with this and/or could refer me to any manufacturers of collectors? Thanks.

 

[PhilNH5]

Bebster,
No experience on my part. But Real Goods is one of the best sources for info on alternative energy.

Phil

 

[Jimbrown]

I do not have it but a couple of my neighbors do. They all swear by it and claim to almost never have to go to the aux heat mode. But this Arizona and we got sun. Not sure you have enough sun in Cape Cod to be effective. The ones with the reflective/ concentrative reflectors are by for the best and most costly. You also may have a freezing proplem in the winter.

 

[reb]

I built one that I used for 10 to 12 years. It was part of a project by a local university. There were a few hours of training and a couple of days of constructing the panels. Then we were turned loose to install them. As I recall, the wisdom then was that flat panels were the most practical way to go. Reflector type collectors can be more efficient, but some kind of tracking mechanism is required for optimum efficiency. There is also more likelihood of hard water sediment plugging the lines in a reflective collector. It is less expensive to use flat panels.

The tank was a standard electric, 80 gallon water heater tank with the lower heater element disconnected. The upper element was controlled by a wall switch for backup. We practically never had to use the backup.

Mine used an electronic control system to sense the temperatures on the collectors and the tank to determine when to operate the pump. Freeze sensors on the panels turned the pump on at night if temps got too low. My electronic controls failed and I found it easier to just use a timer to turn on the pump in the morning and off in the late afternoon. The major problem was freezing, even 20 miles north of Phoenix. After the second or third time of patching leaks, I didn't bother hooking the system back up.

In your area you would probably have to go with a heat exchanger system that uses some kind of antifreeze solution in the collectors, with a double-walled heat exchanger to heat the water in the tank.

 

[dmccarty]

bebster,

Check with your local universities and see if they have any information. The extension office might have info as well. In NC NCSU has a solar center that quite a bit of info on solar. They are house in a solar house on campus. The center has classes all through the year on non traditional energy sources. In NC you can get a tax right off for the use of solar to heat water. It was somewhat complicated on how much you could get but not a big deal.

We planned to put solar water heat generation in the house but even with the tax breaks I figured it was not worth the money.

I just got the power bill for our old house that we are selling. The temps have been such that the heat has not been on for the last month. The only thing using power in the house are some light the water heater,(which I just turned off) and the fridge. The bill was $38. I'm sure most of that was the water heater. In our new house we put in an 80 gallon water heater. I can' remember the exact cost to use but I think it was under $400 a year. I figured it was something like 10 years to recover the cost of the solar water heater. Figured it was not worth the hassle. YMMV.

Our new water heater has a LED light on each electrode. I have yet to see it light up the top one even after running mulitple showers and baths.

I'm waiting for the new house's April power bill. Due to the weather the heat pump has not been used much if at all so the bill should reflect our base power cost throughout the year minus heating and cooling... Can't believe I'm going to say this but I can't wait for the bill..... /forums/images/graemlins/grin.gif /forums/images/graemlins/blush.gif

Later,
Dan

 

[SLOBuds]

I am building a new house and will use solar for DHW, and for electricity.

I live in California, so I get plenty of sunshine. Even so, I am looking at This Evacuated Tube System for DHW collection.

These are highly efficient collectors. And ... quite a bit more expensive than a normal flat panel. But in any event I think you might be interested in the technology.

You have my vote 100% on the solar stuff. Every day that the gas price goes up pennies here and pennies there, I get more committed to my solar installation.

Martin

 

[bebster]

Thanks for the info. The system that Martin is referring to I think is this one made in China. Sunda Beijing . There is a company in Maryland that I just found that makes a similar technology: Thermomax

Plenty of research to do on this -- not many local plumbers or HVAC folks have any experience with this kind of technology.

 

[fenneran]

We had one on two different houses in Florida and were very pleased. It had a large holding tank and we never ran out of hot water. The one time we had a major freeze (late 80's) we had the system freeze up, but that was only because the power was off too and the system could not pump hot water up to the panels. Other times, the electric backup took over and pushed the hot water through the panels and kept them from freezing.

The best part was that we had one of those power company supplied cut offs. This is where you agree to let the power company turn off power to your water heater (and other select appliances) in return for a rebate on your bill every month. I was happy to let them give me a couple of bucks every month for turning off the electric strip in my solar hot water system. The agreement was they would only do it during peak times. Well, the water had been cooking all day, so when they turned it off from 5:00-7:00pm, there was plenty of hot water, and time to make more (in the summer at least) without ever affecting us.

 

[Stonefox]

bebster, I also am planning on installing a solar hot water system for domestic and radiant floor heat in a new home I'm planning to build next year. One source of products and information is from a company based in Lyndonville,Vermont called Radiantec. Check out their web site at Radiantec.com. I requested information to be sent to me and got quite a large packet of info.
Stonefox

 

[v8dave]

I put in a domestic hot water system in a house about 25 years ago. It was in California though. I'm thinking about doing another system at this house too.

The system I put in had two 4' x 10' flat roof panels. The panels were on an almost directly south facing roof. I didn't optimize the tilt angle of the panels, just followed the modest roof angle. At ground level, I put in a separate hot water tank ahead of the natural gas water heater tank (which I kept in use). This system directly heated the water used in the house (that is, no heat exchanger).

The system had a temp sensor on the roof panels that was supposed to drain down the system when it got below freezing. Well, in the late 80's we had a cold snap that froze and burst both the roof panels. I replaced only one panel and changed the system to a drain down every night. In your area of the country you need to be concerned about daytime freezing too. Make sure to cover this in your configuration.

When the two panel system was up, we never ran out of hot water. And, we had four of us using the system, two daughters, wife and I. In this system the solar heated water fed into the natural gas water heater. So, we had a 60 gallon solar system feeding a 40 gallon natural gas water heater. The natural gas heater never came on unless we had multiple days of cloud cover. The natural gas pilot light did stay on and keep the "solar" pre-heated water hot. I made the mistake of turning off the pilot light and found that the water in the 2nd tank did cool off more than we liked. So, it went back on. But, the main burners didn't come on except in the winter. The one panel system we could run the system out of hot water on some spring and autumn days but not in the summer.

Our natural gas bill went to a trivial level spring through autumn even though we had a gas clothes dryer. The gas consumption was mainly heating the house.

The system, even on one panel, would automatically shut down the collection recirculation pump in the summer because the water exceeded the high temp setting. It never did blow off on the roof valve, that I saw or heard, although I am sure it really got very hot. The water pressure raises the boiling point of the water. Enough so, that in my system that it didn't trigger the high temp/pressure valve.

Where I am now, still in California but in the Sierra mountains, we get some freezing days. If I can convince myself that the controllers or system is good enough to take care of the daytime freezing problem, I'll put in another domestic hot water system. We have propane heated water here, it's still cheaper than electric hot water heating. But, the price of propane keeps going up. I've looked into tankless hot water heaters and have convinced myself that a solar system has a better payoff.

Any specific questions? Ask away.