Solar air heat?
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Fair enough. In what I was thinking about, there would be no long ducts. Just directly thru the wall. So the fan power and noise would be much less, if convection wouldn't do enough.
SpaceBus
Minister of Fire
I did remove the registers from the bedroom ducts and put my hand against the panel during our first winter and it was almost too hot to touch on a clear day. How much of that heat made it into the bedroom is questionable. Whatever heat gain we had in the house was offset by how hideous the solar air heater was.
The attached photo is from right before we closed on the house. In full disclosure I did make the small hole you can see towards the bottom right corner.
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I'm not sure if it will pan out, but this branch of research is intriguing in its potential for solar heating.
www.lancaster.ac.uk
Study shows promising material can store solar energy for months or years - Lancaster University
As we move away from fossil fuels and shift to renewable energy to tackle climate change, the need for new ways to capture and store energy becomes increasingly important.
I'm not sure if it will pan out, but this branch of research is intriguing in its potential for solar heating.
Study shows promising material can store solar energy for months or years - Lancaster University
As we move away from fossil fuels and shift to renewable energy to tackle climate change, the need for new ways to capture and store energy becomes increasingly important.
Meh. Azobenzenes get used in all kinds of 'magic trick' experiments with light, but they are not very efficient or durable. And the energy stored per mass of the material is likely rather low.
Dieselhead
Minister of Fire
Anyone ever go ahead with solar heaters? I have an unfinished daylight basement I keep at 57 or so with a heat pump. It’s about 1600sqft. Any load that can be taken off the HP would be beneficial. Where it exits to daylight I get sun from about 10-dusk. Was thinking of a setup on the patio right outside the doors that would be removed and stored in the summer. Thoughts?
EbS-P
Minister of Fire
No.. I did the Math per btu. Paying for electricity was by far cheaper in the short term.
200$ buys me 2Mw. Rough math here and Check.
it is something like 1/2 ton heating capacity for like 5 hours a day 5 months a year at a cop of 3. That is running a a 1 ton mini split at 50% 5 hours a day every day for 5 months.
It’s not that it’s a bad investment. It’s just bulky take time unless done well will leak cold air into the house. Better investment (time and money is air sealing).
I got a quote from Solar Fire (some company from I believe native folks in Minnesota), for an 8 ft panel with all that's needed (small fan, through the wall). But at $2500 or so (before pandemic inflation hit) I did not think it was useful given that I'd have needed to rent a scaffold to mount it on my home as well.
Don't have the time to make one myself.
Don't have the time to make one myself.
EbS-P
Minister of Fire
For that cost you could have a balcony solar system making power all year longI got a quote from Solar Fire (some company from I believe native folks in Minnesota), for an 8 ft panel with all that's needed (small fan, through the wall). But at $2500 or so (before pandemic inflation hit) I did not think it was useful given that I'd have needed to rent a scaffold to mount it on my home as well.
Don't have the time to make one myself.
I'm not convinced that that would be more environmentally friendly; the amount of resources going into PV is much larger and the efficiency is much lower, at least for resistive heat. COP 3 heat pump I'm not sure, but 20% PV is not hard to beat by taking out energy conversions...
Precaud posted about his setup many years back. It worked pretty well and even better in subsequent years as he improved the system. He had the benefit of being in New Mexico with a lot of winter sunshine.
Dieselhead
Minister of Fire
I was looking at a diy type thing, I saw one setup said he produces 240 degree air in Minnesota in the winter. His videos are on YouTube.
Dieselhead
Minister of Fire
In the northeast electricity is $$$. Well, the ridiculous fees they keep piling on is the expensive part. About .10kwh for the electricity itself. A solar heater with an inline solar fan seems intriguing. I don’t want regular solar, so that’s out.
It's not hard.
Black, seal very well,.insulated, and a 20 W fan can produce 1-2.5 kW...
But to make one that lasts will involve material choices that have to be right.
Black, seal very well,.insulated, and a 20 W fan can produce 1-2.5 kW...
But to make one that lasts will involve material choices that have to be right.
Hmmm. I was very enamored by these Solar thermal air panels (commercial or DIY) many years ago. I crunched a lot of numbers and decided that in the NorthEast it was pretty hopeless. This is mostly due to the nature of the solar resource in our region.... lots of cloudy winter days, and lots of 'sunny' days with high or scattered clouds. The parasitic losses are quite high on these systems (esp DIY single glazed ones), and your output drops a lot unless you have FULL unfiltered sun. They also kill you more when you are off angle (morning and afternoon).
At the time I looked at maps of solar THERMAL resource (versus solar PV resource) it was quite plain... the output would be quite small as a fraction of my overall seasonal heating needs (and similar to that I was getting passively through my windows), something less that 10%.
In the Rockies, Colorado or Minnesota, I suspect its a good bit better... they get tons of clear sunny days in winter.
The only solar thermal that made sense was evacuated tube hydronic (bc of the lower parasitic losses, the array working of angle, etc)... that would get a much better harvest per area, but was ofc more expensive.
Solar PV, a grid-tie 'battery' and a minisplit was a way better investment on heat yield.
At the time I looked at maps of solar THERMAL resource (versus solar PV resource) it was quite plain... the output would be quite small as a fraction of my overall seasonal heating needs (and similar to that I was getting passively through my windows), something less that 10%.
In the Rockies, Colorado or Minnesota, I suspect its a good bit better... they get tons of clear sunny days in winter.
The only solar thermal that made sense was evacuated tube hydronic (bc of the lower parasitic losses, the array working of angle, etc)... that would get a much better harvest per area, but was ofc more expensive.
Solar PV, a grid-tie 'battery' and a minisplit was a way better investment on heat yield.
7 years ago my electric usage cost was about $55/mo an avg. Nothing has change on my end since then but the increases in cost from electric suppler have slid that up to $90/mo avg. Most annoying. Being in he northern tier of states Solar is helpful mostly in the warm months, an array that would be beneficial all year is cost prohibitive at present apx $30-40k Oct - April has a pretty good cloud cover, but one can still take advantage of UV radiation as far as a hot air collection system is concerned weather passive or with a small fan. Made couple passive units back in the day ( 70's) which worked ok for what they were.
There are versions with curved (lensing) "glass" fronts to take in more radiation when incidence is not normal.
And while it drops off with clouds, my pv does the same. A LOT.
My car though, warms up nicely when there is a little sun or only bright light through thin clouds.
6000 BTU/hr for 8 hrs a day (they say up to 10,000 BTU/hr for no clouds perpendicular incidence) is nice though, for a much lower investment (a 2-3k$ and running cost of a 20 W fan) than PV+minisplit .
Of course it doesn't heat sufficiently, but it's like running a wood stove and having other heating modulate with a thermostat on top of that.
In the end it's at least comparable photon efficiency; with PV one looses 4/5ths of the energy right from the start. One gains with a COP of 3 again, but that still makes one operate at 60% of what comes in.
I vaguely remember the cansolair had double wall curved lenses, reducing the losses there. Having that piped 6" through the wall means the surface lossess are the biggest of all losses.
Anyway, best ROI is always making it yourself - if one doesn't count ones own time. Problem is that something with strong exposure to sun, that needs to be tight (air and thermal), and parts should remain transparent, it's not all that easy to design one with the right materials for longevity.
And buying is surely to make a dent in the economics.
I do think things like this are very nice for off-grid stuff, or even shops. Get help with a base heating to keep things above freezing, based on a tiny solar panel + battery for the 20 W fan as the only moving part. Low tech robust.
And while it drops off with clouds, my pv does the same. A LOT.
My car though, warms up nicely when there is a little sun or only bright light through thin clouds.
6000 BTU/hr for 8 hrs a day (they say up to 10,000 BTU/hr for no clouds perpendicular incidence) is nice though, for a much lower investment (a 2-3k$ and running cost of a 20 W fan) than PV+minisplit .
Of course it doesn't heat sufficiently, but it's like running a wood stove and having other heating modulate with a thermostat on top of that.
In the end it's at least comparable photon efficiency; with PV one looses 4/5ths of the energy right from the start. One gains with a COP of 3 again, but that still makes one operate at 60% of what comes in.
I vaguely remember the cansolair had double wall curved lenses, reducing the losses there. Having that piped 6" through the wall means the surface lossess are the biggest of all losses.
Anyway, best ROI is always making it yourself - if one doesn't count ones own time. Problem is that something with strong exposure to sun, that needs to be tight (air and thermal), and parts should remain transparent, it's not all that easy to design one with the right materials for longevity.
And buying is surely to make a dent in the economics.
I do think things like this are very nice for off-grid stuff, or even shops. Get help with a base heating to keep things above freezing, based on a tiny solar panel + battery for the 20 W fan as the only moving part. Low tech robust.
Did this same study myself nearly 10 years ago as I was designing the heating system for this house. I had really hoped that some passive solar thermal panels could be used in conjunction with my geothermal heat-pump based radiant floor heating system hydronic tank to make a big impact on the overall usage. But November through mid-January is really mostly cloudy here even if it is cold (thank you prevailing lake effect breezes) and there is nearly no solar gain worth measuring with those types of panels.
Yes - same as I found. Potentially this could have worked but really high cost and dubious durability. What did work best and cheaper? Another couple of kW on the PV array (with net metering) and just forgetting about adding more complications that were likely to fail early.
Wisconsinites are overall quite a bit luckier with overall winter solar radiation (sunshine). You are west of the great lakes and don't get the cloud cover like those of us just east or south of a great lake. I think you are a bit northwest of Milwaukee so I am guessing that the lake effect cloud and snowfall patterns mostly miss you deep into the winter.
EbS-P
Minister of Fire
Evacuated tube collectors with glycol heat exchangers have significant maintenance costs vs PV.
My estimate is at least $ 50 per sq meter for a hot air system
My estimate is at least $ 50 per sq meter for a hot air system
Agreed - if I was off-grid and not net-metered (or utility-tied), I'd be looking at the ROI for some extra solar thermal panels quite a bit differently.
As I tell friends, areas around the Great Lakes are the only places I know where it can be - 10 degrees and cloudy.
