Solar air heating

[Frontier]

I havent read alt.energy.homepower in years but have been doing some
research regarding solar air heaters. We live 100% off grid solar PV and
small wind generator but have a custom wood shop that is on the grid. It has
a nice south facing wall that gets good sun in the winter months and has 3
large overhead doors (12x10) on that wall which we are planning to frame in
2 of the three as they are no longer needed and are huge heat loss openings.

I got to thinking and remembered hearing here years and years ago (perhaps
10) about building solar collectors out of things like aluminum cans and 2
liter bottles and so on. I was wondering if any who read the group had toyed
around with this or perhaps built one/some. I would like to try to keep it
passive (no fans) but fans are not out of the question. My initial thoughts
were to build a box to fit the opening with 2" foam on the back so it would
have an R15 at night with the collector being a simple box with perhaps
aluminum cans epoxy'd to the back wall and painted flat black. An inlet at
the bottom and outlet at the top.

The only thing I didn't like about the passive is the system wont really be
automated and we would likely have to close dampers/gates at night and open
them in the morning.

Just kicking it around and wondering what others may have done especially
with regards to glazing. This would be the hardest part I assume. Trying to
find a cost effective material for 120sq' could get pricey. Lexan and
similar products would be pretty costly for that size opening.

I am thinking however that a collector this size may heat our 4000sq' shop
any time the sun is out which would cut down on the gas bill.

Any input is appreciated,
Mark

 

[[email protected]]

I havent read alt.energy.homepower in years but have been doing some
research regarding solar air heaters. We live 100% off grid solar PV and
small wind generator but have a custom wood shop that is on the grid. It has
a nice south facing wall that gets good sun in the winter months and has 3
large overhead doors (12x10) on that wall which we are planning to frame in
2 of the three as they are no longer needed and are huge heat loss openings.

I got to thinking and remembered hearing here years and years ago (perhaps
10) about building solar collectors out of things like aluminum cans and 2
liter bottles and so on. I was wondering if any who read the group had toyed
around with this or perhaps built one/some. I would like to try to keep it
passive (no fans) but fans are not out of the question. My initial thoughts
were to build a box to fit the opening with 2" foam on the back so it would
have an R15 at night with the collector being a simple box with perhaps
aluminum cans epoxy'd to the back wall and painted flat black. An inlet at
the bottom and outlet at the top.

The only thing I didn't like about the passive is the system wont really be
automated and we would likely have to close dampers/gates at night and open
them in the morning.

Just kicking it around and wondering what others may have done especially
with regards to glazing. This would be the hardest part I assume. Trying to
find a cost effective material for 120sq' could get pricey. Lexan and
similar products would be pretty costly for that size opening.

I am thinking however that a collector this size may heat our 4000sq' shop
any time the sun is out which would cut down on the gas bill.

Any input is appreciated,
Mark

Go to your local window/door contractor and offer to take all his
take-out patio doors. Tempered glass panels for free if you strip off
the aluminum frames for him and allow him to scrap the aluminum.
Normally they need to pay their guys to strip them, and they shatter
the units and trash them.

 

[vaughn]

I am thinking however that a collector this size may heat our 4000sq' shop any
time the sun is out which would cut down on the gas bill.

You need to talk to Morris, a semi-regular here. His passive solar system:
http://www.iedu.com/DeSoto/solar.html

Vaughn

 

[Frontier]

Morris,
I have seen your site before I think via Sawmill Creek perhaps? I think you
may have sold a unit to a member there but not positive. I want to say he
was a custom counter top manufacturer.

Our shop is 4000 sq' metal sided structure which use to be the town fire
station. Its fairly poorly constructed with regards to insulation though we
are improving on that as much as possible. Concrete slab is no where near 6"
thick in the few places I have had to cut it to install dust collection.
Very poor ceiling insulation though we will be improving that once we get
all the bad wiring fixed up and can blow in 12" of cellulose or fiberglass.

The only reason I was talking 10x12 is that is the size of the overhead door
opening that is going to be framed in. It doesn't need to be that big and
being smaller would be much better with regards to the cost of glazing. I
have looked into patio door panels and often have them ourselves as we are
contractors however the double insulated panels often come apart over time
especially once removed from the frames. I had just quickly looked into
single panel polycarbonate from companies like US Plastics and the price on
a 4x8 is reasonable at 200+freight. I may be able to find it locally as
well. I know I can get polycarbonate greenhouse style panels as we use to
have a nursery business and have ready access to that material.

I guess I will have to re-think the metal can idea which was only because I
had seen it before and then of course they are virtually free. What other
material do you recommend inside the collector?

I seem to remember at the time I saw your site last you were not in
production or in limited production and were recommending people to build
their own collectors or something to that effect.

Anyway, thanks a lot for your time and reply. I use to be one
alt.energy.homepower almost daily when we were getting this off-grid
property underway and on line but havent been on in ages.

Thanks,

 

[Frontier]

Also forgot, we are in Central WV 38.34N approximately.

 

[Frontier]

Morris,
Thanks for all the information. I pretty much had gotten what you're saying
with regards to innovation and so on from your posts I read previously and
your reverse engineering page on your site now. I have to admit, my work in
construction and the wood shop are so overwhelmingly busy right now that I
was/am looking for a bit of a guide to doing something that would work
rather than trying to re-invent the wheel. I really enjoy building
prototypes and working out designs and so on when I have time but it is what
I am doing all day and I simply don't have many more hours (or ounces of
energy) to add something else to the mix.

I am really not motivated by saving gas or money on this deal either its
just that living off grid, seeing these two openings that are going to be
closed up looks to be a prime opportunity to do "something" with them other
than wall them in. Additionally our shop is right on the main street and
seeing these panels would likely cause some buzz but I hate to think of it
that way as someone will likely walk in wanting us to build them some and I
have enough things to build. It would however be nice exposure for solar
heating in general.

I will do some reading on the site you posted. At a quick glance you may
have also posted that information as it looks a little familiar.

Agreed with regards to closing up/sealing up however its not going to be a
quick process in this building as I don't have the time to re-wire the
entire place in one shot and I am not willing to bury much of the work the
old "firemen" did when they put up this building. It's a wonder the fire
station didn't burn down.

I will look to some sources for aluminum and see what I can come up with. At
present I am thinking of a box unit made of 1/2" MDO ply and now will have
to come up with something for the collector but it shouldn't be a major
issue. I will get to reading.

 

[Gordon]

I havent read alt.energy.homepower in years but have been doing some
research regarding solar air heaters. We live 100% off grid solar PV
and small wind generator but have a custom wood shop that is on the
grid. It has a nice south facing wall that gets good sun in the winter
months and has 3 large overhead doors (12x10) on that wall which we
are planning to frame in 2 of the three as they are no longer needed
and are huge heat loss openings.

I got to thinking and remembered hearing here years and years ago
(perhaps 10) about building solar collectors
Any input is appreciated,
Mark

OK,
If you were to glaze the door openings with a store front type
window system. The sun would shine in and directly heat the shop.
Very passive, very cheap. To prevent heat loss at night, you
could build a set of bi-fold insulated shutters or doors to
fold over the windows at night. The advantave of this system
is that it would also provide plenty of natural light for the
shop.

Other alternitives are to frame in the openings and leave a
opening at the top and bottom for air flow. Sheath the frameing
with plywood and paint it black. Then glaze with used sliding
patio door glass as someone else mentioned.

There is also a tromb (sp?) wall. Close the opening with a c
concrete block wall. Paint the outside black then glaze, as
above. The sun will heat up the wall, then the heat will
transfer through the block to the inside. If you use hollow
cinder block, you could force air through the interior of the
wall.

 

[Frontier]

I'm still amazed that someone would pour a less than 6" slab to support

fire trucks...

Well, this is a very country/rural area to say the least and what often
shocks me in places like this is things are either grossly over engineered
or horrendously under engineered. You see this all the time in old farm
buildings or homes where something was slapped together out of parts or junk
wood because the people either didn't have the money or were to cheap to buy
what they needed but then they put 52 nails in a joint where two 2x4s come
together so that its "nailed good". They go way over the top where it really
doesn't matter and fall far short where it does.

This floor is actually quite comical because we have had to cut it to form
trough's for ducting. They threw anything and everything in the slab to act
as rebar. Old telephone pole guy wires coiled around willie nilly, rod,
pieces of pipe, and so on. Then it looks that they put large rebar on top of
the pour and worked them down to the wet mix so now you have your mat in the
upper third of the slab rather than in the lower third where it should be.
This of course adds virtually no strength and then causes the thin layer of
concrete over top of the mat to break/flake off. So in many places the wear
layer of the slab has flaked away exposing a #6 bar an inch below the
surface.

How it held up as long as it did I don't know but we have heavy clay soils
here so they have extremely high compressive strength and that is likely
what saved them.

The rest of the building is better but similar. It was put together with
volunteer labor on donated land and I am sure on a shoe string budget so
they did the best they could with what they had.

Even with all that we have 4000sq' under roof for a very small fraction of
what it would cost to build a new building so I have to count my blessings.

Thanks again for the info and nice to talk,
Mark