Why almost no one doing Solar Thermal?

[1201]

In some parts of the world, up to 90% of homes have solar thermal systems. It wont work for all of the U.S but there are many areas that could support a simple solar thermal system yet I don't see a lot of places selling solar thermal equipment or a lot of people installing them.
Also, just looking at rough number it appears that thermal could actually be cheaper than PV, so,
Why have you decided to heat water with Solar PV instead of Solar thermal

 

[timselectric]

Solar PV panels are so cheap, now. The thermal panels are no longer cost effective.

 

[JJJJ]

Have seen for swimming pools. Could also depend on geography.

 

[1201]

Solar PV panels are so cheap, now. The thermal panels are no longer cost effective.

But that's because the few companies selling them are charging very high prices for the panels. On Alibaba the solar thermal panels are very inexpensive but shipping only one or two would not be affordable.

 

[timselectric]

With a few cheap panels, a cheap water heater , and a DC relay. You can have hot water for under $1k.
And almost zero maintenance.

 

[Rusty959]

I've been mentally assembling a system for awhile that would include a ~10k gallon insulated tank to store some heat for winter. My big issue to pull the trigger is while a solar electric system is easy to pass on to the next owner of my house whenever that may be, a 10k gallon tank with ~150°+ water is hard to explain and I'm probably not going to take it with me.

Plus solar is relatively maintenance free. Once you get pumps and water and buildup involved things get a bit more hairy.

 

[1201]

With a few cheap panels, a cheap water heater , and a DC relay. You can have hot water for under $1k.
And almost zero maintenance.

you mean pv panels? I use 10kwh for water heater daily. I would need 2.5kw of panels, an inverter, and batteries . thats not an under $1k system.

 

[1201]

I've been mentally assembling a system for awhile that would include a ~10k gallon insulated tank to store some heat for winter. My big issue to pull the trigger is while a solar electric system is easy to pass on to the next owner of my house whenever that may be, a 10k gallon tank with ~150°+ water is hard to explain and I'm probably not going to take it with me.

Plus solar is relatively maintenance free. Once you get pumps and water and buildup involved things get a bit more hairy.

10k gallons of hot water- interesting.
looking at all the threads here pv and battery are not that maintenance free. they also have a fairly short lifespan

 

[timselectric]

you mean pv panels? I use 10kwh for water heater daily. I would need 2.5kw of panels, an inverter, and batteries . thats not an under $1k system.

The PV panels can be connected directly to the water heater elements. No inverter required.
Everything needed is available used and cheap.

 

[upnorthandpersonal]

Because I need power, not hot water, especially in summer. I can get all my hot water needs just by PV in summer and indeed with solar thermal if I had it. However, I can also get my cold water in summer using PV. Reason I need it: underfloor radiant cooling, with a heat pump. This same heat pump helps out in spring/autumn when I need hot water, but when I really need it (winter) solar thermal would be just as useless as PV.

 

[Supervstech]

you mean pv panels? I use 10kwh for water heater daily. I would need 2.5kw of panels, an inverter, and batteries . thats not an under $1k system.

Actually… no…

A PV water heater doesn’t need inverter or batteries… just a few panels, a water heater, and a dc relay… no pumps, no storage pipes, no plumbing… no maintenance, just hot water…

 

[timselectric]

10k gallons of hot water- interesting.
looking at all the threads here pv and battery are not that maintenance free. they also have a fairly short lifespan

I haven't touched the panels or batteries, since they were installed.
I haven't touched the inverters either. But I'm not expecting them to last 20 years. Like everything else.

 

[dougbert]

I had solar thermal, worked great in the summer, but in the cold of winter not so well. After 10 years my $500 copper heat exchanger developed leaks.SOOOO I looked at that roof space taken up by the collector and took it down.

I used that space to located PV panels. For my case, a much better solution

when my batteries are full, my water heaters (2 in cascading heating circuit) of 100 gallons, are heated by the excess solar power. I do NOT do netmetering so I harvest that energy into tanks that feed to my tankless water heater that tops off the heat rise if needed

so for me, PV is more versatile

 

[BentleyJ]

IMO, Solar thermal only makes sense if it is integrated into PV. I'm referring to combined heat and electricity panels. For example, PV where the cells are smaller and a Fresnel lens is used to concentrate sunlight which makes both heat and DC. If a liquid coolant loop was attached to the back of the PV panel it would mount and install similarly to a normal panel mechanically and electrically speaking but would have an additional connection for a liquid cooling loop.
The amount of potential extra maintenance would limit adoption by the general public.
I'd be willing to give it a try as would many of the DIY'ers here but I'm not aware of any commercial product availability.

 

[1201]

Actually… no…

A PV water heater doesn’t need inverter or batteries… just a few panels, a water heater, and a dc relay… no pumps, no storage pipes, no plumbing… no maintenance, just hot water…

Oh ok, I missed that part. That would save quite a lot on the cost.

 

[timselectric]

IMO, Solar thermal only makes sense if it is integrated into PV. I'm referring to combined heat and electricity panels. For example, PV where the cells are smaller and a Fresnel lens is used to concentrate sunlight which makes both heat and DC. If a liquid coolant loop was attached to the back of the PV panel it would mount and install similarly to a normal panel mechanically and electrically speaking but would have an additional connection for a liquid cooling loop.
The amount of potential extra maintenance would limit adoption by the general public.
I'd be willing to give it a try as would many of the DIY'ers here but I'm not aware of any commercial product availability.

I actually thought about adding pex tubing loops under my panels for this reason. Pulling the heat away from the panels would also make them more efficient. Plus it could be used to melt snow in the winter.

 

[JJJJ]

One of the challenges of thermal is the insulation factor. For instance, this has been proposed to pull heat from composting piles. It does work, however in this case the heat exchange occurs in a narrow area which when cooled prevents the rest of the pile from feeding the water line. In essence it is insulated from the source.

On the other hand, if the water had a more direct contact, e.g. radiant heating fins used in warming a room, one might be able to bypass this limitation. For many this might not be of much help in the colder climates since the panel wouldn't likely heat up during the winter.

In lower states this could potentially be quite useful to a point since the sun can get quite warm.

One of the challenges with a large tank is where to put it. I can only imagine the conversation with a neighbor during an installation.

Whatcha doing?

and my imagination takes over...

On the other hand, if one has a large plot of land....

 

[Crowz]

The reason I didn't go with a dedicated water heater solution is it was easier and cheaper to let the inverter handle it directly after I weighed the options on the newer of my homes.

The older house which I had when I started doing solar etc I had tried dc heating elements in the electric water heater and that sucked. None of the ones I could get at the time were powerful enough to do much.

Then I tried ac and dc elements. Again not happy with it since I couldn't tell it really helped any.

Then I tried the black box with tubing circulating the hot water heater water thru that. Had problems managing the heat levels like I wanted. Overheated way to much mostly.

Then I tried the storage tank method which was fun. Didn't work out that great for hot water and my house heating attempts from it were moderately successful at best but it did work great as a pool heater

Year round swimming.

So when I bought the new house I just decided to let the inverter handle it at some point when I expand the solar setup that large. With the hybrid method I use it will handle the hot water heater when the suns up and grid power it at night like normal. Problem checked off with zero effort

 

[1201]

The reason I didn't go with a dedicated water heater solution is it was easier and cheaper to let the inverter handle it directly after I weighed the options on the newer of my homes.

The older house which I had when I started doing solar etc I had tried dc heating elements in the electric water heater and that sucked. None of the ones I could get at the time were powerful enough to do much.

Then I tried ac and dc elements. Again not happy with it since I couldn't tell it really helped any.

Then I tried the black box with tubing circulating the hot water heater water thru that. Had problems managing the heat levels like I wanted. Overheated way to much mostly.

Then I tried the storage tank method which was fun. Didn't work out that great for hot water and my house heating attempts from it were moderately successful at best but it did work great as a pool heater

Year round swimming.

So when I bought the new house I just decided to let the inverter handle it at some point when I expand the solar setup that large. With the hybrid method I use it will handle the hot water heater when the suns up and grid power it at night like normal. Problem checked off with zero effort

Great info! Thanks. I guess that kills the direct DC option lol.

Which black box did you use and how many? I could size smaller to prevent overheating

 

[Crowz]

Great info! Thanks. I guess that kills the direct DC option lol.

Which black box did you use and how many? I could size smaller to prevent overheating

8x4 box for the collector with a 30 gallon hot water heater I was trying to heat.