Solar heating chat

[Bossrox]

Solar air & water heating, got something going?

Before I dove into solar power, I built 2 solar heaters that've been up & running successfully for a couple years, An air & water heater. I'll go into more detail as I get settled in setting up this forum with some youtube video's of them coming soon but for now here's some pics. I lose the use of the solar water for winter but gain the solar furnace so it kinda balances out on the energy savings.


My solar air furnace with channeling baffles, 25 ft x 3 1/2 ft. It pumps out up to 120 degree heat in full sun exposure. When the fan isn't running, I've seen the box temp hitting 160 degrees. It's thermostatically controlled, comes on automatically when the box temp reaches it's set level & back off the same way.

Air is sucked out of a floor vent in house & forced into the solar box's lower channel with a high velocity bullet fan where it zig zags thru the center then into the top feeding the house. The intent of the channels is to reduce any potential stagnant pockets of btu's that may not get swept up efficiently vs what an otherwise indiscriminate air flow might cause.

Simply made from 6" 5/4 board for the frame & channeling baffles, plywood backing, interior painted black then siliconed any cracks that could leak. Had to use a 1 ton 3 gang pulley to get it up on the wall & that was before the glass was put in.

Here's my 2nd solar water heater amounting to about 40 feet of 1/2" copper pipe looped in a couple dozen rows under the glass & about 3x3 ft in size. My 1st test version was about half the size & had a pretty inadequate output.The water heater was turned down to 110 degrees but the thermostatically controlled circulating pump for the array keeps it just about scalding hot in the summer. Of course it has to be disconnected & drained in the winter so the roof pipes don't rupture from freezing & the tank thermostats get kicked back up.

Just made with 2x2's, durarock backing & painted black inside. Glass isn't sealed on the frame, just held in place with hanging iron on the corners so it can easily be serviced if any pipes spring some leaks.

[Bossrox]

In my new place now.

Well now that I've moved & my new mini house is built, a new solar furnace has to be built for it, the solar water heater is already up but in this spring weather, isn't quite hot enough yet to make piping hot water without some other assistance but as soon as it starts getting in the 90's, it'll do just fine. I've added a propane tankless water heater to my arsenal for backup in case I have neither solar or utility power.

The solar furnace will get put together in the fall & I'll have a real in depth video of all it's aspects after it's done.

The new solar water heater has weather stripping on the perimeter to seal the glass & keep the heat from escaping.

Technical detail of how it works, is a temperature sensor attached to the output side of of the solar collector coil waits for the temp to reach a desired temp, in the summer I have it at about 130 degrees. When it hits that, a water solenoid opens & a low volume pump draws water from the cold side of the water heater, sends it to the solar collector & back to the hot side of the tank heater.

Since all water heaters have a tube going to the bottom on the cold side, when the cooler water from the bottom hits the temp sensor, it shuts down at 120 degrees & waits for another cycle which could be around every 15 minutes during peak sun in the summer. Not all that complicated & I get pretty near scalding hot water from it during summer but only mediocre results in spring & fall so look out for another bigger unit to get built.

Update: In this pic, it's set up as stationary but later I hinged it & hooked it to a winch to swing it in a direct angle to the sun. This gave me substantially more hot water.

[Bossrox]

2 new bigger solar water heaters getting built

My current heater is about 43x40 which makes scalding hot water in summer but doesn't do very good in between so I'm getting started on a new 1 that'll be around 76x36, almost double the size of the other to replace the original & hinged just like the other for tracking the sun, using the same winch & hoist from the original heater.

Instead of copper pipe, this time I'm going to use pex. Pex is the best water pipe that's in use today however this will also be a test to see how long it can hold up under UV radiation but it may not be much of an issue 'cuz the pipe will be painted black which may possibly protect the pipe from the UV, but only time will tell on that.

This new version will have quick dump valves to drain it if freezing temps are forecast then easily refilled after it's above freezing. The backing like the other is cement board, waterproof & a good heat sink but to keep cold from the backside bleeding thru to the inside, a double layer of reflective foam boards shielding the backside should take care of that.

I have no idea yet how well it'll perform with outside temps down in the 40's but from my experience with the solar furnace I built, I saw cabinet temps in the 170's. If this does the same, I should be able to make some decent hot water even in the depths of winter.

Since my original heater was adequate for summer, this 1 will certainly be overkill & make a tank of hot water in no time but since it'll be hinged, once I get the tank heated up to temp, all I'll have to do is swing it away from direct sunlight.

The coil of 1/2" pipe is about 100ft, heating about a gallon of water each cycle with the projected cost @ about $200 not counting the glass cover, winch & other hardware I already have.

Anyways, some pics will be forthcoming soon & test results when there's good sun with temps down in the 40's, so stay tuned.

Big unexpected bummer. The bulk glass I already have & was expecting to get cut to size, turns out to be tempered that can't be cut so I looked into a getting a 1/4" glass pane cut for about $150, whew that's steep but then find out this, & a WARNING! If you endevour to build something like this, use only tempered glass. Glass sellers advised me that regular glass would not be able to handle the heat stress in solar applications.

So I shopped around to see what that'll cost & got some quotes for over $300 but found 1 place that would make a piece for about $175. Still not cheap & pushes the project cost way higher than expected but has to be done, tho it's holding me up from finishing it til I can come up with the $$$ for the glass. Hope it does as good as the worth of the cost. Will let you know.

A good sized piece of tempered glass ain't cheap. If you want to take a stab at building something like this, look on craiglist for some used sliding glass doors. That'll give you 2 huge chunks of tempered glass you'll likely get for next to nothing, then once you have that glass, build your container box around it's size rather than building a box 1st & having to get a piece of glass made for it.

A great idea came to me today.... As you'll find further in this thread, I built a solar furnace for my cabin that far exceeded my performance expectations so I decided to make another 1 for my shed but then got the idea of incorporating a solar water heater in the same space.

You're probably thinking, but I'm already making a new solar water heater & yeah, but here's the problem with it. Even tho it's bigger & should make more hot water than the 1st 1, with the angle of the sun during winter & the position the heater is angled at, a good bit of the suns energy is lost reflected off the glass.

That heater will work best in late spring to early fall but the new shed furnace with the water heater coil inside of it, will be facing the sun almost directly, all day without having to pivot it this time of year & if it also produces heat in the 190's like my cabin furnace is doing, that's enough heat to do both water & air heating at the same time & should out perform the other heater I hope. So I'll have 2 solar water heaters I can use, each better suited for different times of the year. Will update ya'll with the stats results & comparisons of each when they're done.

This is my 2nd water heater build & as mentioned, a 3rd is in progress too at the same time but this heater is waiting on some glass that was ordered to complete it. Will have a another pic of it & test results when it's done tho I'm not expecting as exciting results as I believe the next heater will do. I'll go into the other Winter furnace/water heater combo in the next thread.



Finished & connected to the winch to pivot it.

[Bossrox]

2 new solar furnaces getting built & 1 will be a combo to heat water as well.

I was going to put off building a solar furnace til I added an addition next year but couldn't stand the wait & pissing away all the free heat I could make use of, so it's going up now & besides, I already have most of the materials to get it built except the lumber & paint so this project won't cost me very much & the gas I'll save for heating this season will pay for a good chunk of it if not most.

Here's the beginnings to finished pics of it taking shape, blower motor is under the cabin, ducts have been connected & the intake comes from up under my bed to keep the suction noise muffled down, just have to finish the frame, glass it & wire it up. Will be a pretty quickly done project. A video covering this is planned sometime soon.

You can see the forced air duct that'll feed the box coming from underneath. The output duct will be on top of the box at the other end, with it entering the house just below the ceiling. Finished size will be 10ft x 45" for my 12 x 12 cabin.

As you'll see further down, this furnace has way exceeded my expectations for heat output & since that turned out so spectacular, the shed is getting 1 made for it too but also with a coil of pipe inside the box to heat water at the same time. How that performs should be an intresting topic I'll get to when it done & tested.



Blower motor under the house.



Frame done, black paint & glass next, wire it up & it'll be ready to go.



I finished it this morning with a full sunny day ahead to test it. Fired it up for the 1st time @ 10 this morning & 35 degrees outside & it's cranking out a rock solid 115 degree heat. This is way better than I ever imagined & in short order has gotten very warm inside, so now I have figure out a scheme to attenuate it if it gets too hot in here, but for now I'm having to open a window & crack open the door. I'm finding out this size furnace is way more potent than I needed for this 12 x 12 cabin & would likely heat a cabin 4 times the size nicely.



115 was the temp 1st thing after it was fired up, I had to leave at noon & shut off the blower but before I left, the box temp rose to 150 degrees. When I returned at 3pm, the outside temp was 51 & the box temp was 175. The blower wasn't on but the convection of the heat rising out of the box thru the duct into the cabin was all it took to keep the cabin really toasty. It's apparent I'll need to find a scheme to vent the excess heat outside when needed. Just have no plan yet how to do it on it's own without manual intervention.

Got a probable solution to attenuate the heat. Found a electrical-mechanical butterfly valve I'm going to T into the suction side of the duct where I can draw colder air from outside thru the furnace plus drilled another hole in the top of the box to bleed off more excess if needed & can be capped off if not. Will see how those works out.

The heat output has far exceeded my expectations to where I'm starting a 2nd furnace to heat the shed which is sparsely insulated & takes more gas to heat it than the cabin, needed to keep it from freezing inside & it's already in the works & you'll hear more about it as it progresses.

Day 2 of testing & the sky's are getting a thick dose of chemtrails today obscuring the sun pretty good but the furnace is still kicking out decent heat @ 110 degrees so it appears the box size isn't overkill after all for days like this & or partly cloudy.



This blew me away. It was about 65 degrees outside & full sun & caught this reading around noon, 195 degrees, WOW!



Here's the new shed solar furnace/water heater taking shape & have most of the materials already, including the glass, for an out of pocket expense of just a couple hundred bux for the lumber & plumbing.



Plumbing roughed in, wood strips under the pipes are to keep them from drooping so it'll drain fully without standing pockets of water that would freeze. Will have about 110 ft of 1/2" pipe when done.



Paint job done. Blower motor for the furnace not in yet but ready for the glass to go on for the water heater testing for now & tomorrow will be sunny, test details to come.



Here's the finished heater but compared to the other furnace, this isn't even coming close to the heat output. At the same time I'm getting box temps in the 190's from the 1st furnace, the new 1 stays mostly @ 110 degrees til after 1pm then struggles up to 120 for a few hours. & forget my hope of it making hot water & air at the same time. Not gonna happen in it's present state.

If I run the blower to send hot air into the shed, with it drawing in upper 40's air from inside the shed, the box temp never gets hot enough to heat water, much less any decent hot air from it & if I don't run the blower, it will make hot water but only at around 115 degrees. Not at all impressive results!

I'm miffed why there's such a difference. The only thought that comes to mind is the 1st furnace is on an insulated wall where the 2nd is just 1/2 inch plywood with the back exposed to the outside cold air & that may be why it can't build up more heat than it does, so I guess I'm gonna try to sandwich a sheet of reflective foam between another sheet of thinner plywood behind it to see if that helps any.

It's apparent it's not big enough to get the job done tho, so I have another piece of glass the same size & it appears likely I'll end up having to use it & double the size of the box.

Update: It was in the 60's today & the heater made a substantial amount of hot water in the 130 degree range so that's telling me, I am losing a good bit of heat from the backing when it's exposed to frigid temps. Will see if sandwiching in some reflective foam behind it solves the issue & get back to y'all.



The doubling of the shed heater combo, total size, 13 ft x 4 ft with a loop of about a 200 ft of pipe. Testing results to follow. Testing results: Doubling the size made a big difference but with issues running both the furnace & water heater together. It's complicated so I'm doing a separate post on this issue further down.

[Bossrox]

Another thought comes to mind for combining the 2 water heaters if needed

Without yet testing both heaters, I was thinking if the newer Winter heater doesn't do the job adequately then combining both heaters would certainly beef up the heating capacity, but it can't be done by hooking them in series. It would require separate pumps working independently of each other. So this could turn into another project & upgrade & likely will, not 'cuz 1 heater might not make enough hot water but how fast it can get the water good 'n' hot will be a big factor.

During summer, a tank of hot water doesn't lose a lot of heat overnite & the sun is up pretty early so it didn't take long with my old heater to get it hot enough before I was ready to jump in the shower.

But during winter, the shed where it's at is just heated enough to keep it from freezing inside & the tank looses most of it's heat overnite, then the sun intensity isn't very strong til about 10am so it appears unlikely with just a single solar heater to get the water hot, fast enough to get an early shower without having to fire some electric to it unless it can produce a tank of scalding hot water by the days end, but it seems more likely the 2nd heater will need to be employed to pitch in at least for the early part of day.

If this happens or turns out to be unnecessary, there'll be some further details to come.

Testing update: I had a day off to play with the 2 heaters & found by alternating them when they got up to temp, they did a good job making a tank of hot water pretty fast but wasn't quite scalding as I'd like so a new pump was ordered so they can run independently & the furnace/water heater combo is getting doubled in size, doubling the heater coil size for heating water.

I'm pretty confident when it's all done, I'll have all the hot water I'll need for winter on sunny days & should be hot enough by the end of the day to keep enough hot water in the tank overnite to still have decent heat in the morning to get a shower without having to wait for it reheat back up. Will let y'all know how it comes out when it's finished.

The new pump is in & here's the results

[Bossrox]

Solar furnace/water heater issues to deal with

Well here's what came of the test. Without the blower running for the furnace, it made loads of hot water fast but with the blower on, the water heater thermostat would not register a high enough temp needed to engage the circulating pump.

Here's where I'm stumped tho. Even tho the thermostat couldn't reach the proper temp with the blower running & kicking out heat somewhere between 105 & 110 degrees, I found out the pipe loop was getting significantly hotter, enough to send a good batch of hot water to the tank but for some reason the thermostat pickup which is mounted on a pipe at the top of the box & wrapped to shield it from the blowing lower air temp & should be the hottest part of the box, but it won't register it.

While the box temp was around 110 & the water heater sensor the same. I kicked in the pump to see if there was any difference in the pipe loop temp & it jumped into the 140's, plenty hot to send to the tank for storage so the furnace & water heater can do both chores at the same time but a thermostat for the water heater isn't going to work & I'm going to have to come up with another method of activating the pump when there's hot water ready to transfer.

Right now I'm stumped on how I'll do that so I'll be testing various methods & see what I can come up with & get back to this hopefully with an answer.

A little more testing & this is the way it'll have to work. It's not what I was hoping for but an acceptable compromise. The priority is more hot water than heating the shed & since running the blower while trying to heat water doesn't allow the water heater coil to get hot enough, what I decided to do is set the blower to only come on at about 140 degrees & shut down at 130. This will allow enough heat to build up to heat water & produce some heat for the shed tho not like I was wishing for, so It didn't meet my expectations totally but wasn't a flop or a waste of money. With both water heaters running now, I'm getting plenty of hot water for winter.

[Bossrox]

got a video up now covering my solar furnace.

[Bossrox]

Got a video up going into detail of my solar water heating system. Let me know what ya think.