Inexpensive solar heat panels

[dogman]

Re posting this because it's cold time again, and the original thread is buried from years ago, before the alternative energy section was made. This might not work so great in the far north, but here on the Mexico border we get lots of great sun even in winter. About 6 hours a day of noticeable heat is produced. On bitter cold cloudy days, though it may be useless to open the vents, it still keeps a part of the wall warmer, lessening the heat loss on the cold day.

The idea is similar to a trombe wall, but set up more like a heat exchanger instead of a heat storage. Here is my south southeast facing front wall of the house.

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Off to a good start already with a 4'x8' window that gathers sun nicely. On either side are 3'x6'8" used sliding glass door panels. Freebie of course, but they can be bought at most flea markets. Inside each panel is a sheet of steel roof painted black. Here is the wood framework, screwed to the wall and caulked, to make a space for the metal panel behind the glass.

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The tree in the reflection is perfectly placed to shade the window in summer, but the sun shines under the branches all winter.

Inside the window is some more steel roof, with the top still open to see outside. Great view of the nearby Organ mts I want to still see. The black metal definitely gets hotter than other surfaces the sun might otherwise hit, and the hot metal radiates the heat back into the room nice. Still get plenty of light since the window is big.

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Where the panels are attached to the wall on either side of the window, there are vents cut through the wall that allow air to circulate by convection all day. At night, they have to be covered to prevent them from convecting cold air all night. So I use magnetic covers made from cardboard and flexy magnetic strip. All day when the sun shines, heat pours out the upper vent, and cold floor air sucks into the lower vent.

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Any day it reaches 50F, and the sun shines, It will warm the living room and kitchen to 70F. The window by itself would only heat the room to about 60.

I also modified the front porch. The iorn barred door was removed and replaced with a storm door, then the remaining iron was covered with easy to cut panels intended to be light fixture diffusers.

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Inside, I keep a bit of summer going in there all winter. On a warm day I can gather some heat here too, but mostly it just keeps a bit of my exterior wall warmer than normal. Eliminates freezing drafts through the front door weather strips. I'll get a few tomatoes for another month or so, till it starts just reaching 32 in there at night. The panzies will keep blooming all winter, and stink up the place with spring smells in January. By february, hell, it's spring here and I can start next years tomatoes in the porch.

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[captain387]

Looks like a pretty good setup, the sun is a nice "free" source (except taxes go up due to increased value of house with solar installations)
I have solar hot water on my house, unfortunately at an angle of 20 degrees due to slope of roof (45 degrees is ideal in Ontario, Canada). The solar hot water panel at the shop was at 45 degrees and I have seen the temperature reach 70 celsius(158 f) on a -15 celsius (5 f) day. My panel has reached 50 c on a -15 c due to the low angle.

Just a note : The metal which is on the inside of the window does absorb the suns energy but the amount absorbed would practically be the same as what would be absorbed by the floor, walls, and furniture.

Here is a great site which has loads of information of alternate energy and lifestyle choices. They even have some experiments determining which sort of materials are best suited for an air heater. I think layers of window screen created the best results.

http://www.builditsolar.com/

Jeremy

[dogman]

True, you don't get more photons. Therefore the heat is the same. But there is a very noticeable difference. The metal does a much much better job of transfering that heat into the air in the room. The hotter surface creates some air that is hotter than would otherwise be the case, and sets up better convection in the air. The end result is the room gets comfortable faster in the morning, and the back of the room gets more heat. Without the metal in the window, I could enjoy the difference between cold floor, and really cold floor, while also enjoying how nippy it is further back in the room where I'm at the computer. Nahh.

It's a tradeoff, between storing heat multiday or just being warmer this morning right now. This way works good in my climate and because the wall is facing just a bit east, gets the air warmed nice and fast in the am when I want it most. If I had a lot more glass on that wall, then I might prefer a true trombe wall type setup. I just don't get enough heat from this to make trying to store it in thermal mass worthwhile. I'd rather just have the heat spread through the house faster. One nice thing, no need to rum cieling fans with the nice convection flow going. I'd love to add more to this, increase the glass at a better angle, include a buried rock storage, thermostated fans etc. But that sure didn't all fit into this projects budget of less than $100.

A back bedroom has a west facing window. The dilemma there is if you open the drapes to warm the room the sun shines in your eyes while you try to nap or watch TV. A similar metal plate on half the window solved the problem beautifully. Again, convection keeps the room evenly heated, but not drafty. And the metal blocks the sun from your face, while still allowing the toes to toast in the sumbeam while you nap.

[captain387]

Well its always nice to see solar being incorporated to offset other types of fuels while making a comfortable living space.
It boggles my mind as I see all of these new houses being constructed with the garage on the south side without windows and on the north side
a whole wall constructed of glass.

[dogman]

No kidding. When I built houses, it used to really bother me to build houses that had the floor plan plopped on the lot with no regard to which way the windows faced. In this climate, you almost need as much north window as south, but need to keep any south window tightly covered all summer.


One of the reasons I bought my house was it had at least a few windows pointing the right direction for winter solar gain. They work oppositely in summer of course heating up the house too much in a hot climate. The south window already had a tree placed in the right spot to shade it in summer. It shaded all winter too, so over the first two years in the house I pruned the canopy up enough to start having the lower angle winter sun shine under the pine tree's branches. Now the shade is perfect, on the window in summer, on the wall above the window in winter.

The back west facing window was a real problem in summer. Two red oak trees were planted, which now shade the window all summer. In winter the sun sets further south, and shines on the window in the cold months. It took carefull watching of the sunset position for an entire year to properly place those trees. Other trees on the lot had to go the day we moved in.

Though the house is not too badly set up now, it still remains built on the lot backwards. They should have built the mirror image of the plan used, and put my garage on the right side instead of the left. As built, the back porch is blazing hot all summer and unusable. Within 7 days of moving in, I'd cut a new door into the living room wall on the opposite side of the house giving acess to the part of the yard where there is shade in summertime. The back porch is slowly improving as those trees mature, but it's still always nicer on the east side on a summer afternoon.

[jmygann]

My man cave under construction .... black felt air collectors

[dogman]

The diagram is too small for me to read. So the cabinet is solar collecting area, and themal mass storage, maybe water?

You need more overhang on the roof, so the sun is blocked in summer, but shines under the roof edge in winter. A quick and dirty substitute could be solar screen or agricultural shade cloth.

[TylerDurden]

I think it says "55gal drums".

[spinningmagnets]

I spent about a year of my spare time perusing the builditsolar.com website...so mant great ideas! For myself I came to the conclusion that the best solar heat store is a hybrid with the upper layer being 55-gal drums of water, and the lower half being dry-stack masonry blocks (cinder blocks?). An affordable masonry alternative was round stones about the size of a roasted chicken.

Masonry absorbs the available heat that being applied to it must faster than water drums, so you can capture and harvest the more of the energy in the winter when the sun may be intermittent. However water drums can hold MUCH more BTUs per volume, so...at night (or during a couple hours of cloudiness) when there is no more heat gathering, the heat that was quickly grabbed by the masonry will slowly rise into the water drum bank.

The amount of heat transfer from the warm air to the masonry is affected by the temperature differential. If you expose the storage to an hour of warm air, warm blocks would not absorb as much as cool blocks. Overnight, most of the heat that had been grabbed by the blocks has migrated up into the drums.

IF...my theoretical heat storage was all drums, it would not absorb as much of the available harvest that is available (slow absorbtion) . but, if it was all masonry, it would become quickly saturated because it couldn't hold as much per volume (it would need to be 3 times bigger to hold as many BTUs as the hybrid storage).

I seem to remember the designer was a guy named DeLancey? The heat store was elevated above the panels so gathering was completely passive, and it worked without fans or electricity whenever the sun came out. However, in order to focus the design to maximize grabbing the maximum heat possible from intermittent winter sun, the distribution to the house required ducts and fans.

I preferred the closed system distribution, which was a large aluminum intercooler (air-to-air radiator) from a turbocharged 18-wheeler (insurance companies replace them rather than repair a small crack, so they are cheap at repair shops and frequently just recycled). It was set in the top of the heavily insulated heat storage enclosure. This ensured that any smells that might develop in the storage would not affect the living space. Heres the link to the index of dozens of solar air heating ideas:
http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

[El_Steak]

Being in Canada, I don't have as many options for solar heating, but in the summer its great for the pool.

I installed those a few years ago with a fully automated sensor/valve system. It allows me to maintain my pool above 90F almost all summer long. Thats 192sq/ft of panel heating a small 6000gal in ground pool. My neighboors pools are all between 75-80F so needless to say we have a lot of people over during the summer. I'm all for it, as long as they bring beer and steak

[wineboyrider]

Dogman is right about the way a house faces. I have a manufactured home and purposely set my porch on the south side so i get good sun blockage in the summer, but a good amount of light in the winter. All the rooms of my house on the south facing side have windows. The one small computer room gets pretty toasty warm in winter with just the shades up. I might try building a removable collector on the south side of the house.. Until then I heat with about 95% scrap wood from the winery.

Is that a beer can solar collector in the first picture Dogman?

[dogman]

My heat exchanger uses a corrugated roof panel, painted black. Simpler and easier than assembling the cans. More surface area than flat metal.

Re the other stuff. That's what I thought I was seeing, some kind of water thermal mass on a trombe wall. Wish I had the budget to go big on this stuff, but what I have supplements the house furnace pretty good, given the climate. We really live in solar energy heaven here. Pretty rare to get more than 3 days without good solar gain. We got actual snow the other day, and 10F for a low. So I just fired up the wood heater for a few days. 80 trees to prune in winter at work keeps the woodpile big.

I would love to build a huge rock thermal storage device, not for winter but for summer. I saw one once connected to a swamp cooler. The swamp cooler was set by a timer to cool the rocks at night. Pretty neat, the AC electric load on the grid was transfered to night, the cooler put out much colder temps at night, and the blower and thermostat system kept the house cool, and dry, all day. So you got cheap swamp cooling, but without the swamp effect on the house humidity. Would work good with a refrigerated air cooler too of course. Much cheaper to cool air from 90F than from 115, grid power used at night, etc. Oughta be a law to have in every new house built really. $$$ will keep me from ever doing it.

[jmygann]

The diagram is too small for me to read. So the cabinet is solar collecting area, and themal mass storage, maybe water?

You need more overhang on the roof, so the sun is blocked in summer, but shines under the roof edge in winter. A quick and dirty substitute could be solar screen or agricultural shade cloth.

I have a 3' overhang in the summer. Isolated air collector to water storage in an insulated cabinet is the best IMHO

http://www.ece.vill.edu/~nick/solar/solar.html




http://www.ibiblio.org/london/renewable ... 00026.html

[dogman]

That design looks really good.

In your pic, it looked like a lot less than three feet of overhang over the panel wall. How you shade it doesn't matter, just that you do. Or maybe in your design the heat gain can be just shut off from heating the house. I have the tree that shades the front wall most of the day in summer.

[jmygann]

The 3' roof extension is removed for winter and only shades the top half(windows) in the summer. the bottom half(hot air collectors) are shaded by the 4x8' winter reflectors tipped up to cover the hot air collectors ... Working on a night cooling system

[dogman]

There you go, summer shade you remove. Another way to get the same results. Agricultural shade cloth or phoenix style sun screens can also work for summer.


In the santa fe style solar house, they have an even longer overhang, that points slightly up. In summer it shades the glass wall, in winter the sun just peeks under the eaves to shine on the big window. I got lucky and the previous owner planted a tree to shade the window. I only needed to prune the lower branches to get winter sun, and keep the summer shade.

[Evoforce]

These are some good ideas guys!

[Jay64]

There you go, summer shade you remove. Another way to get the same results. Agricultural shade cloth or phoenix style sun screens can also work for summer.

I've got a ton of shade cloth. I picked up a whole new role on clearance for $8. I think there is something like 150'. I was thinking of trying to figure out a way to stretch it across the roof with about 1-2' gap between the roof and the cloth. I was figuring this would shade the roof and give a little airflow under it to help keep it a lot cooler. I want to devise a way to pull it back during the winter time to allow the sun to heat up the roof as much as possible. I was thinking that a series of cables pulled tight above the roof would allow me to string the shad cloth along it through grommets. Then during the winter time I could just pull it back along the cables.

[amberwolf]

What I had planned for doing something similar was to put a pipe frame over the roof, with rings mounted on teh edges of teh cloth at the end corners. Several rolls end to end along the underside of the roof edge, with a roller on the edge of the roof itself for the cloth to pass against. Cable running thru the pipe on a pulley at the top end, so I can pull the cloth up the roof when needed. To roll back up I just loosen the cable tied down at the bottom end, and hand-roll them back up (could use a motor, too, but no real need).

The rolls stay under the roof edge when rolled up so they are shaded from the destructive AZ sun, to help lengthen their life.

If the latter didnt' matter, I could put the rolls on the center of the roof instead, but rolling htem back up would require a motor instead, unless I got up on the roof, too.

[TylerDurden]

Louvers?

[jmygann]

Couple of good groups ....

http://tech.groups.yahoo.com/group/SimplySolar/

http://tech.groups.yahoo.com/group/SolarHeat/