?? about types of solar water heaters

woodswellDecember 26, 2006

OK, I'm getting down to the final choices for building our ICF house. We decidede that photovoltaic systems are just not cost effective enough right now to invest in with our tight budget so we're putting that money into the tightest, most solid structure possible.

But I do think that here in Florida solar water heaters are definitely cost effective. I've seen three different types of systems: building integrates, passive systems that directly heat the water use standard tank water heaters for backup and passive systems with integrated tanks that use glycol to heat the water.

The dealer does not recommend the intergrated building system type - with that system, the piping for the collection loops is installed under a metal roof. If there is any leakage, not only does it come right through the roof sheathing, you've got to tear out your roof to repair it.

I'm sort of drawn to the type with the integrated tank - that seems as though it would limit the plumbing connections and therefore limit the possibilities of leakage. Plus since it is one system, there could be no finger-pointing in the case of problems.

Also, I was concerned about where the water heater tank would be located in the houseand this takes it completely OUTSIDE!

Here are the two systems I am comparing:

Thermosiphon Passive Solar Water Heater

40 Gallon Passive Solar Water Heater

Any advice on either of the two types of solar water heater? Any advice on other brands I should consider. A note on this - my BIL is a dealer for Eco-$mart, so I will get a discount of these systems. ;-) But I want to buy a good system, not just get whatever I can get for cheap!



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Let's see FPL is 10.5c/kwh and natural gas (if available) is 50c/therm. You have a couple of options here based upon what you need hot water for: Laundry (perhaps) showers. A tank is a waste of money (similar to leaving your car idling in a parking lot all day) so you have tankless gas fired, and tankless electrically fired. Bosch and other manufacturers make both. There are solar panels for hot water (not PV) panels which are roof mounted, and the standing tanks like in Dominica. There are new PV panels coming out soon so don't discount this idea.

    Bookmark   December 26, 2006 at 10:46PM
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What is IFC I missed that, sorry.

    Bookmark   December 26, 2006 at 10:48PM
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We're all electric - I'm phobic about fire and will not have any gas in my house. Electric tankless water heaters are not very practical from what I see. And with irregular schedules if we have solar water heat we will need a tank to maintain the water temperature.

Right now, we have our two electric water heaters on timers. One runs one hour per day; the other runs two hours per day. Unless we're taking back to back showers or washing clothes all day, that maintains plenty of hot water for our use all day long.

The cost of tankless water heaters does not seem reasonable to me. There is no practical savings for us given the way we've been using our electric water heaters for the last twenty years. It would take a very, very long time for tankless to repay the high inital investment and most importantly, it would NOT save energy.

Photovoltaic will eventually be cost effective - but the industry has been saying that since I first looked at PV in the late 1970s. I'm not writing PV off completely, but right now the most cost effective thing I can do with that money is to invest in the building envelope.

A PV system for our house would cost between $10,000 and $30,000 installed. For that money, I can make a lot of improvements to the building envelope that will decrease my reliance on powered systems for the life of the building - estimated to be a hundred years or more at minimum. Granted, a system that would have provided the same amount of energy would have cost hundreds of thousands in the early 1980s - but would need to be replaced by now. When PV costs come down I will consider installing a system, but it is NOT practical RIGHT NOW.

ICF = insulated concrete forms - foam insulation forms with rebar reinforced concrete poured inside. The forms stay and provide the insulation. Insulation quality is excellent and ICF construction is the most cost effective hurricane resistant building method around.


    Bookmark   December 27, 2006 at 2:52PM
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The thermosiphon system from Eco-$sense is Solahart - so that is a good brand?

I'm looking at the rating and do find some Solahart systems in there, but understanding what the figures mean will take some time. Guess I need to call BIL and find out the brand of the other system, too. They don't say on their pages - I only found Solahart mentioned in the installation guide. 8-/

Unfortunately right now when I have to make these major decisions I am not very sharp. I'm going in for knee surgery in a few weeks and am taking loads of pain meds to tide me over. Zoned does not even describe it. %~?

I'll come back when I've more info and questions.

    Bookmark   December 27, 2006 at 3:00PM
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"The thermosiphon system from Eco-$sense is Solahart - so that is a good brand?"

I would say they have a good reputation -- I've not heard anything bad about them.


    Bookmark   December 27, 2006 at 7:30PM
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Hi again,

You are probably already aware of this, but just in case you are not -- you have a great solar resource in Florida -- the Florida Solar Energy Center (FSEC):

They provide a lot of useful information including system ratings, and they have done quite a bit of high quality orginal research over the years. And, they answer emails.


    Bookmark   December 28, 2006 at 6:52PM
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I've been to the Florida Solar Energy Center. Problem is, every time I bookmark something there and come back, they've changed the pages around and the link is dead. In fact, I think one link you have on your page to them is dead, FYI.

They do have good info, but I'm reaching information overload or something. I read the info and zone completely out. I'd prefer to just go to a solar company and have them install a system, but the only local one is owned by a jerk and I don't want to do business with him.

While looking for a contractor, I did talk to one home owner who was installing solar water heat - I need to contact him and see if he installed it himself or has someone he can recommend.

Thanks - I still need to read more of the info you listed above, but I am being really slow about it.


    Bookmark   December 28, 2006 at 10:44PM
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Anne where all are you building your new house? Actually I got the (IFC) acronym from another page however did you know that a meteorologist from Boston invented the system? In the Northeast, we have an eight foot wall (mostly below grade), you do it above. That's huge. I suppose heating hot water isn't a big deal since you only need to heat it +30 degrees or so for shower temp. Te tankless is the way to go since the prices have dropped, there's an IRS tax credit (Bush Energy Bill) and $300 back from most utilities. Just a thought as FPL is doing quite well, and your electric rate will double in ten years. Your quote for PV is high, what kind of system were you quoted so much money for?

Have a great New Years!

    Bookmark   December 30, 2006 at 7:21PM
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I'm North Florida, with a small rural cooperative power company that does not do any kind of incentives to save money. They resent anyone who even asks about having solar electric capacity and will NOT buy excess power generated from solar panels. That's the other reason that the cost of a PV system would not be recovered any time quickly.

Solar water heating here in the summer could be as easy as painting a 55 gallon drum black and leaving it in the sun, LOL! But it is more difficult up here in the winter since we do get cold weather in the winter and can have several days in a row without sun. So a system that can supplement the solar heating is required.

With most of the solar water heating systems I have seen, a tank is a necessary part of the system to store the heated water until needed at night. So as long as I've got to have a tank for the solar water heating, having a heating element to maintain the temperature is reasonable.

Sorry, you are not going to convince me that tankless water heaters make more sense than a solar with a supplemental tank system.

I have not gotten a quote for a PV system. The prices I mentioned were from talking to local people who have installde PV, looking at the web site for the one local installer (who is such a creep I'd never allow him on my property) and reading information in various places on the internet. The prices are probably higher than the lowest possible available, but they are likely what I'ld pay locally.

Until there is a different supplier/installer locally, our power coop will buy excess PV production, battery storage systems are more efficient and longer lasting, and PV systems come down more in price, I don't consider PV to be practical for me here and now.


    Bookmark   December 30, 2006 at 11:58PM
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I've had two Cornell Energy solar passive "batch" water heaters in operation since 1995 in central California, growing zone 7. I've been very happy with their performance. They were chosen on the basis of simplicity of design and installation, and low cost. They consist of a black 40 gallon tank with inlet and outlet pipes and a 180 degree temp-pressure relief valve (standard $7 plumbing part) parabolic reflectors, foam insulation behind the reflectors, all enclosed in a fibreglass shell with low iron glass, plumbed in series with a tempering valve. They don't have any freeze protection because the large volume of water resists freezing. They typically start boiling water in February triggering the temp relief valve. They do cool substantially overnight, although water that was hot enough for a hot shower the night before is still hot enough for a warm shower the next morning. We try to plan some hot water usage for 11am-2pm to cool the collectors- laundry,timer on dishwasher etc. We have an electric backup heater.

    Bookmark   January 27, 2007 at 1:49PM
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Actually they don't paint them black. Here is a house in the Carribean that I'm looking at.

    Bookmark   January 27, 2007 at 5:24PM
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woodswell, sorry I'm little help with the solar hot water question. Ours uses a standard electric tank for backup, but we can run the system just using the electric unit as a holding tank, which is how it's set up now. We expect the rooftop system to be fine for just the two of us. With several overnight guests, or prolonged cold and cloudy weather, we might turn on the backup heater.

In other words, the hot water comes off the roof into the hot water heater tank. It's drawn from there into our household plumbing. But the hot water heater is not using any power, it just holds the water. It's well insulated, so keeps the water plenty hot.

Electric tankless hot water heaters are downright expensive to run! It's true that gas tankless units are very cost effective.

We looked into electric tankless briefly. Among other things, the amount of power we would have needed to have available to the house would have gone up, triggering an expensive surcharge to have more power made available. If I remember right, the power company requires that you have enough power coming to your house to run all appliances, lights, etc. at the same time. They only provide as much power to each transformer as they expect the number of houses connected to it to use. If your house is going to be the one that goes over, than you're the one who needs to pay for an additional transformer.

bushleague, love that house in the Caribbean! We'll all come visit on vacation! ;-)

    Bookmark   January 31, 2007 at 12:01AM
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A friend of mine got the Stiebel Eltron System (panels, pump and tank)at houseneeds and says it works like a charm..and at a reasonable price...
Hope this helps

    Bookmark   March 24, 2008 at 5:41PM
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Hi Bushleague. New to the forum. Lots of great information. I am Greek, but now live in Southern California, and the picture of the house in the Carribean with the roof-mounted water tank and solar panel is a set-up you will find in every house in the entire country of Greece. It is the standard procedure. You would in fact have to pay extra to get an in-house gas-or electric-powered tank. Anyway, my contractor is very interested in putting something like this in his home. In fact, he wants to make his house something of a walk-through demonstration of different eco-friendly techniques to show clientes. All of my web-searching has not revealed a distributor/retailer of these kind of self-contained, roof-mounted units in the U.S or specifically California. It seems you know a lot about this stuff. Any suggestions or places you can point me to? Thanks so much

    Bookmark   January 3, 2009 at 1:39PM
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Hi Ioakim,
You might try the SolaHart North America contact at the attached link and see if they can find you a dealer.

It looks like Rheem and SolaHart are partenering now -- the SolaHart collectors have been around a long time and are sold around the world.


Here is a link that might be useful: SolaHart

    Bookmark   January 4, 2009 at 12:56PM
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Hi Gary..Excellent and spot on. That's exactly what I was looking for. In Greece, the predominant manufacturer of these self-contained roof mounted units is Bosch, although sometimes sold under different names. But the SolaHart units are very nice and there were several dealers listed in California. Thanks so much!


    Bookmark   January 4, 2009 at 1:50PM
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