Automated Louvers for a Passive Solar Heater

Nice topic.
I'd have thought natural convection would stop it working in reverse?
But if you need something a small latching solenoid driven from a timer or temperature sensor should do it.

Del

We have a 2x6 house with heavy insulation. I think the air in the solar box would get very cold at night and the convection would begin again but in reverse.

I will look into the latching solenoid.

Thanks,

Bill

http://en.wikipedia.org/wiki/Trombe_wall

wikipedia's getting better

note the mylar damper at the bottom which acts as a one-way valve, I also liked the exhaust port modification just watch out for proton torpedoes if you incorporate one.

I wonder if the convection or convecting air flow will be strong enough to open the mylar door enough to allow maximum flow? I envisioned this same arrangment but with an actuator to open and close it.

Thanks,

Bill

Del is right -- convection will stop automatically when heated air ceases to be produced.

Do you intend to heat outside air, or recirculate inside air?

I think the box will get colder than the house at night, then the air will move down and a cold draft will come out the bottom. It will basically act like a big window and the R value will be reduced to that of a window instead of a 2x6 insulated wall.

I intend to recirculate inside air.

Thanks,

Bill

you may want to check put solarwindowheaters.com for your controller. I built a six panel array and their new 1500 series looks very interesting.

I checked them out and it looks like that may work out well. I am hoping to do it for close to free but may have to break down and spend a little.

Thanks,

Bill

How about a photo cell used to turn lights on at dark. 24 volt transformer used in the controls on a thermostat of a furnace. Small 24v actuator to pull a damper closed.

As others have said if the solar box is well constructed there will be little heat loss. The back and sides should be well insulated. If an IGU(Insulated Glass Unit) is used there would be less conduction of heat thru the glass. Well sealed. All these increase the efficiency of your solar heater.

This may work also. Did some looking but have not found the actuators yet.

I plan on using some sort of dual pane window for the glazing. We have dual pane windows in our home and you can still feel a slight bit of coolness near them compared to the 2x6 walls. I know I am being nit picky about this but I am trying to build a box that is the most efficient and uses little or no energy.

I do appreciate your comments. This site is awesome!

Bill

Google search Greenhouse Automatic Vent Operator -

"This addition automatically controls and stabilizes the air quality in your gardenhouse by expanding or closing the vents as needed. They are located on the roof and base of the structure and operate using paraffin (wax) that adjusts the vents according..."

Just one of many examples. Costs range from $30 for small ones up to $200 for units to handle heavy windows. This is an old technology that has been around for at least 25 years.

Ed Weldon, Los Gatos, CA

Hey Ed,

The greenhouse vent opener is exactly the type of item I am thinking of. Thank you! And I've been to Los Gatos when I was a teenager.

Hello Billdad,

Check what this dude did for his green house vents is quite details with video support too I need that.

Yep! He accomplished the goal! It is very cool but too large a scale for my application. Also, I don't want to run a computer and all that hardware.

Thanks for the link.

Bill

Okay go to the hardware store and buy that round thermostat from Honeywell or find an old one open it up and see how it works. Use it as the switch for in place of the other dudes computer

Try this

Excellent suggestion! Thanks, I feel I am closer to completing my idea than ever!

Bill

OK everyone. If you all aren't tired of this subject, I have some other ideas to brainstorm.

One of my ideas uses some sort of (how do I put this). Expanding metal such as a bi-metal coil that winds and unwinds as temps change. Just like in a thermostat or auto choke in a car (I think those are bi-metal). If I can aquire or build a register that requires very little pressure to open, or even a flap like the mylar one or a doggie door, maybe this coil would exert enough pressure.

Or: a flat bar of bi-metal a few feet long. As the two warm up one expands more than the other and viola! The bar bends at the un-anchored end and opens the louver.

Another idea: try to find an air cylinder actuator that uses very little pressure. The supply air could be in a tank painted black. When the sun heats the tank the air expands and the increased pressure pushes the cylinder open.

If you think any of these are possible please feel free to comment. If you feel any of these are not possible please feel free to shoot them down. I can take it, I think.

Thanks all,

Bill

Hey dude...I love your expanding air from the black cylinder idea....

All the hallmarks of a great idea... simple, few moving parts..no operator effort.

I'd love to see it tried
Kudos

Del

You could reduce the torque needed to operate the flap by counterbalancing it -

Might also want a damper to stop it rattling about when room doors are opened/closed etc.

Nice...

This is so simple but very useable! With the right balance the convection will probably do the trick!

Thanks,

Bill

This one is the best choice in my oppinion, because the flap itself operates as a check valve for the air, and that's all. No computer, no switches, no wiring. Want more flow? Add one or two more openings.

Passive Louvers for a Passive Solar Heater

Here is a simple one-way air valve design:

Staple some coarse screen across an opening of the solar collector. (Keep the mesh aligned vertical and horizontal.) Starting at the bottom of the screen, add horizontal strips of flexible film across the screen, attached to the screen only at the top edge of each strip. Overlap the strips. Now with the slightest air pressure, the strips open. When the direction of air reverses, the strips seal the opening.

Add another one-way valve at the other end of the solar collector, but facing the other way. Now they are connected in series, and block both openings at night.

P.S. The ventilation holes on the solar panel should be as large in cross section as the cross section of the panel itself. Rectangular openings nearly as wide as the collector interior are optimal.

I like the air cylinder idea. Just make your vent balanced by pivoting it near the middle. You won't need much force to move it.

Very good advice! It sounds like you have it figured out. I will consider "pushing" the air with a fan.

köszönet

Bill

www.makingthings.com/teleo/teleo/cookbook/autofan/index.htm

This is a cool site!

Thanks,

Bill

Warm air near the ceiling can be a real pain. I used a garden shed (brick built, single skin) as a workshop for several years. It was heated by an electric convector on the wall. In winter there could be 10°C difference between air at the ceiling & near the floor.

I installed a section of 4" waste pipe from ceiling to floor level, with a small fan at the top to recirculate the air - problem solved - feet nice & toasty . Noise was a bit of a nuisance, as the pipe tended to act like an organ pipe, but it was quite a mellow tone, and not too intrusive.

Wouldn't want it in a domestic setup, though, and you'd probably have to juggle the fan speed & maybe incorporate some baffles to kill resonances.

Noise was a bit of a nuisance, as the pipe tended to act like an organ pipe, but it was quite a mellow tone, and not too intrusive.

Great thanks we'll get Zalman or Vantec fan and paint the black heavy drain tubing

This is something I will have to consider after installation.

Thanks,

Bill

Your idea sounds great but still it'll have its flaws. People used to have stoves built from heat retaining bricks which were enamel coated on the surface that gave then a shinny look. These stoves had to be heated up first, in <2hours (depended on your preference) and kept giving off heat all day and well into the night.

Your wall will give off heat in an inefficient way but if you use its heat for floor heating (like in many places they do with water) then you could have an almost free heating of the room/s on sunny days with maybe a little bit of boosting.

Try the Smart Vent, made to ventilate foundations.It consumes no power, is operated by a bi-metal spring.It is 8inches by 16 inches,the same size as a standard foundation vent,or cinder block.The spring looks like it would be easy to adjust the opening point, although it is not designed to do so.Anyway, it opens when hot, closes when cold.Relatively cheap,simple, and trouble free.

HTRN

I did check these out and they are perfect! Some are also called "Temp Vents". They use no power and work automatically. Here is a link if anyone is interested.

http://www.tempvent.com/TV210.pdf

Thank you,

Bill

Cansolair has a very nice product. It even looks good! That is what I plan to make almost exactly.

Thanks,

Bill

Yes dear,

You surely can make passive solar heater ( the correct technical name is Solar Air Heater) on your south facing wall. But there are few points to be taken care of.

The heater that u wish to build, need a specific design. In the sense that what is the size of the room/house that u wish to heat with ur solar air heater. A solar air heater of the size 3X6 feet can give u roughly the heat that u can compare with 1500-1800 watt. electrical heater. But that is for instant use. As you seem to use the air heater for storing heat for night/ cloudy hours use, it need some design additions/ modifications. The correct name for this type Solar Air heater is - ROCK BED SOLAR AIR HEATER CUM STORAGE SYSTEM.

Essentially the said ROCK BED SOLAR AIR HEATER CUM STORAGE SYSTEM consists of A- Outer shell made up of insulating material like wood/ board of thickness 1 inch.

B- A GI sheet box of the size appro 3X6 feet. housed in the outer shell.

C- Solid rock/ bricks layer attached to the inner side of the GI sheet box. The rock/bricks need to painted matt finished black paint.

D- Two layrs of toughned/ normal window glass on top

Rest of the arrangement as you have mentioned is OK.

The solar energy that will fall on the rock/bricks painted black will be absorbed by the rocks/bricks during sun shine hours and it will release the energy durinf offsun shine hours for heating your room/house. for better capturing of Solar energy you need to tilt the collector so that maximum energy falls on it.

I am Dr N P Singh, after having done my Ph.D from IIT-New Delhi I am working with Govt of India for last 23 yrs,

I am available at npsdhillon@gmail.com

Dr Singh,

I had not planned on storing heat for nighttime. I only wanted to produce heat during sunshine. But you raise an interesting point. If I do as you mention I can store heat for later in the evening and may not have to worry about the opening and closing of the vents.

The first room to be fitted with the heater is a garage/workshop. It is 1430 square feet. It is 2x6 wall and finished with sheetrock inside and stucco outside, and heavy insulation in walls and attic. I just want to warm it a bit so as not to need any other heaters for the times I work on projects.

Thank you for your input,

Bill

Are these rocks indoors or outdoors. Just being a Joe Schmo I am inclined to think that rocks outdoors would be too cold to heat up in time, if outside in a box, or perhaps what you are saying is that the rocks warm up later, and hence provide that stored heat later. The thermal mass in your house is essentially that "rock", although storing rocks in your house does increase thermal mass. With that said the key to this technology, like that in http://cansolair.com/ (then watch video), is you take the heat from your house and pump it through this panel outside which then is heated by a few more degrees then a second fan pumps that back into your house. Now if warm air from your house is passing over these cold rocks outside in the heater box, then you are not as well-off than if you were to design like the Cansolair guy.

Perhaps you could send us directions/plans/links so we can see how this technology is employed.

Yes dear,

Your question is very relevant.

As I tried to explain to Bill that outer shell is made up of insulating material. Then the inner metal box made up of GI/ MS sheets. The rock will be placed in the metal box. And for reducing the top heat losses two layers of glass need to be fitted on top of metal box. As the air heater need to be kept in tilted position so the rocks/ bricks need to be tied to the metal box so that they remain uniformly distributed on the floor of metal box. As the rocks/ bricks are painted matt black, it will absorb heat during sun shine hours and will start radiating heat during off sun shine/ cloudy hours. Air in the Tilted air heater will surely move up and enter the space that need to heated.

Dr N P Singh

Sounds like you need the Nuaire Sunwarm product. http://www.nuaire.co.uk/Product/Renewables

Wow, another excellent answer! I love this site!

Thank you,

Bill

man oh man,

this is a tuffy.There's so many different ways of doin this that it just makes me foam at the mouth thinkin about it.

1) go see a heating and ac guy about indoor and outdoor thermostats and actuator motors.(damper motors)

2)find an electrician that tinkers in this stuff and stand back while he shows off.bet he'll do some of it for free just to show how much he knows. (those electricians have large egos)

3) find someone with PLC experience and wiring control experience to design a wiring package.write a small program for the motors with timeing and temp built into it.

one thing to think about,the same horsepower motor uses the same amount of power (watts) whether it's twelve volt dc or one hundred twenty ac.(ohms law)

a remote stat with a probe in the collector with a few contactors for fan,actuator,(duct motor),with a box to put it all in should do ya.

good luck

I've been foaming for years thinking and planning this. The shop is finished now I am in the final thinking/planning stages for the heater. You have several great ideas. I work at a mining/milling plant and have electricians and plc guys available. Never thought of enlisting them.

Thank you,

Bill

Ease Billad:

Do it with a Std wall thermocontrol, that goes on-off when temperature riches the set one -with any air conditioner-.

Better dont keep partialy closed the lovers -down the wall- but keep them open to get the most of convection phenomena.

Except, when confortable room temperature riches, then control signal must activates an electromagnetic actuator that closes the lovers -they have a rage plus/ minus-. You can buy one spare that opens your station wagon back door (with the handcontrol)- then adapt a cam action to interconected lovers.

Cotrol`s card and activator use a 3Volts or so and very low wattage plug in adapter.

I assume you live in cold weather. But, We dont need it in Mexico

Congratulations!!!!! please do it, since it is the only way we can revert climate change, and your energy bill will be lower, not bad.

Ease Chema,

Please tell me what does "Ease" mean. You have many good ideas. I will keep them in mind. I live in the Southern California desert. It gets cold in the winter but not too bad.

Thank you,

Bill

hi again

try this number

a remote stat with a probe in the collector,set at...oh let's say 75 degrees,(closes on the rise),a twenty four volt step down transformer wired to the stat (one wire) from there to an twenty four volt (coil voltage) contactor.

the one contactor would operate the fan.(110 volt ac)

another contactor would actuate the duct motor opening the duct work,more than likely a 24 volt actuator.

the transformer would be 110 volt to 24 volt step down transformer connected to common house power. one wire going to the stat,the other going to the common connection on the contactors. make sure you have all the electrical in a good UL approved box.

any more questions,just ask.I'm one of those electricians with an inflated ego.(not really)

This sounds good. If I decide to go with the powered type unit I will certainly contact you.

Thanks,

Bill

Hi! Check out this site: http://www.freeweb.hu/napenergia/gyak/szp/sztgyi_en.htm or this: http://www.sorkollektor.hu/eng/ regards, father-52 from Hungary

Hello father-52,

I looked at the site but it was all in Hungarian (I think). Thanks though.

Bill

When did you look at it?
This is the English version with pictures.

father-52

This panel appears to be good to heat any room in the house regardless of its orientation as long as the solar panel is facing the Sun.

I tried again and got it in english. The panel and the presentation are very well done. He mentions the electrical device to stop the cold air from coming in when no sun is shining. I hope to build almost the identical panel with a heat activated louver or valve to stop the cold backdraft. My aim is to use no electric what so ever.

Thanks for the referal!

Bill

Hi, Billdad, There aren't electric check valves but these are "butterfly-wing" type valves. These are opened by the blown air. These close automatically when the ventilator doesn't work. (The check valves enlarge the flow resistance of the panel of course.) regards, father-52 from Hungary

Oh, I understand. My design won't have a ventilator. I am hoping to employ just convection to draft the cool room air from the bottom vent up through the collector and out of the top vent back into the room. I may modify it to run a 12 volt fan that is recharged by a solar panel later. But the first model I hope will be totally passive.

I am half Hungarian and my sisters and brother go to Hungry for visits often.