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Author Topic: Is solar thermal heating out of date ?  (Read 872 times)

etienne

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Is solar thermal heating out of date ?
« on: June 01, 2017, 05:30:42 PM »
Hello,

I see always more systems using directly solar electricity to heat sanitary water, I even heard of a system from Solacal using DC current in order to save the inverter costs and losts.

I had an idea to use solar heat without having to change too much my heating system, send it to a supplier and didn't got any answer. See attachment.
Pumps and anti backflow systems are not drawn.

Does anybody has experience with such configurations ? Does it make sense ? Is thermal solar really more expensive than PV solar ?

My feeling was that thermal solar was seen as not so good because panels' surface was most of the time oversized, so ROI (and EROEI - energy return on energy investment) was too low, but looks like things are worse than what I thought.

Thanks for your comments,

Etienne

oren

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Re: Is solar thermal heating out of date ?
« Reply #1 on: June 01, 2017, 05:50:08 PM »
In Israel I believe a solar water heater is mandated by building codes for new buildings.
From Wikipedia "Solar Water Heating":
Israel, Cyprus and Greece are the per capita leaders in the use of solar water heating systems supporting 30%–40% of homes.

I'm not sure if this is what you were refering to. I can't say whether it's cheaper than PV and other stuff, but it is very convenient in a sunny climate.

rboyd

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Re: Is solar thermal heating out of date ?
« Reply #2 on: June 01, 2017, 06:00:08 PM »
One of the easiest policy fixes to out in place, mandate solar water heathers for all new buildings and subsidize retrofits. Good climate policy and good working class jobs!

TerryM

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Re: Is solar thermal heating out of date ?
« Reply #3 on: June 01, 2017, 07:18:54 PM »
The systems I've seen were all pre-heaters, in other words your present water heater is left in place, but the feed in is through a solar heater.
Your water temperature is still regulated by the water heater's thermostat, but especially during high usage periods, almost all heat is supplied by the solar heater. A large, well insulated water heater provides the best results.
Terry

etienne

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Re: Is solar thermal heating out of date ?
« Reply #4 on: June 01, 2017, 07:54:03 PM »
The systems I've seen were all pre-heaters, in other words your present water heater is left in place, but the feed in is through a solar heater.
Your water temperature is still regulated by the water heater's thermostat, but especially during high usage periods, almost all heat is supplied by the solar heater. A large, well insulated water heater provides the best results.
Terry

Well, this is really a good idea for retrofit. Do you know if this also works for the house heating part of the system ? The only issue is space in the heating room (in Luxembourg, the heater has to be in a separate room that has fire doors).

Thanks,

Etienne

etienne

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Re: Is solar thermal heating out of date ?
« Reply #5 on: June 01, 2017, 09:10:30 PM »
To continue the previous reply, since there is no fire related to a pre-heater were the feed is a solar heater, I could place it outside of the heating room, so space would not be an issue anymore.

Really a good idea.

Etienne

ghoti

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Re: Is solar thermal heating out of date ?
« Reply #6 on: June 02, 2017, 01:38:17 AM »
In locations where freezing is an annual issue solar domestic hot water  systems are expensive and mechanically much more complicated that PV. I have both in Ottawa, Canada. The solar domestic hot water is not economically efficient despite it being more solar efficient than PV.

I have it to reduce the natural gas I'd otherwise burn to heat hot water. PV installation prices dropped by half since I installed the solar hot water. It might well be economically better to heat water with the electricity from PV at this stage.

sidd

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Re: Is solar thermal heating out of date ?
« Reply #7 on: June 02, 2017, 06:52:34 AM »
" It might well be economically better to heat water with the electricity from PV at this stage."

this was actually true for the last commercial project i ran costs for. But i got to say, for a quick do it yourself project when resources are limited, solar hot water preheat is a no brainer. And incredibly easy to install. Freezeup can be beaten with thermosiphon or antifreeze with heat exchanger isolation.

sidd

etienne

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Re: Is solar thermal heating out of date ?
« Reply #8 on: June 02, 2017, 12:27:00 PM »
Well, about economics, my parents have thermal solar since something around 1996 and still very happy with it. They never talked of any specific issue with that part of the heating system, and they live in the Swiss Alps in a Ski station. The nice thing when you're up in the mountains is that you have much more sun than down in the valley.
Of course costs can be lower when you buy the systems with PV panels because of the huge cost drop of all the electronical systems. This is also valid for LED lights, also electronics.
But with the life span issue, I still wonder what's the best in a non business context. Business needs shorter ROI.

Thanks for the ideas and comments.

Etienne

numerobis

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Re: Is solar thermal heating out of date ?
« Reply #9 on: June 05, 2017, 01:54:19 AM »
Solar thermal is definitely still a thing.

If you're doing a solar PV system, it might be cheaper to just add a few more panels on it, than to have two types of panels and get permits both for plumbing work and for electrical work.

I'm used to these systems having glycol in them, so there's no freezing problem.

ghoti

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Re: Is solar thermal heating out of date ?
« Reply #10 on: June 05, 2017, 04:50:11 AM »
No freezing problem but more complicated and more maintenance. Glycol loop, expansion tanks, relief valves, pump, control electronics, glycol replacement every few years....

numerobis

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Re: Is solar thermal heating out of date ?
« Reply #11 on: June 06, 2017, 12:44:51 AM »
Heating systems in Canada are often glycol already. That way if they fail you don't have to condemn the whole house.