Update on my solar air panels

[Dave B]

  Just an update on my solar air panels here at http://www.fieldlines.com/story/2009/2/24/24929/4256  It's May and still in the 40's at night so I am in no hurry to cover these over and shut them down. The amount of heat from them is amazing and it's all automatic with the snap disk thermostat. I chuckle every time they kick on and off (on at 110 and off at 90F)

 It is most certainly a very cost effective way to supplement your heating source. They normally run about 50F higher temp differntial from the inside air intake. It's bright but overcast right now at noon and they are running. The output temp is approx. 120F. Fill up the house with heat during the day and my log home acts as a big heat sink, no fuel burned again tonight. A great project well worth the time and effort.  Dave B.

[dlenox]

Dave,

Sounds like a great project for me in the future.  Picking up my solar pv panels tonight and in short term will have tracker completed, installed and working.  Then I can get back to modifying my turbine (already down).

I looked through the original posting and I did not see the size (L x W X D) of those solar heat panels you made.  Can you post it?

thanks,

Dan Lenox

[tmcmurran]

I would really be interested to have a peek at your materials list as well as any photo's or plans you might have done during the builds.  Your idea is just what the doctor ordered if I can source the materials here.

[Dave B]

Hey Dan,

  The dual pane glass came from 8' sliding patio doors. I aquired 3 of these from 2 sets of doors (the 4th one was hazed over with the seal broken). I know the back panel I used for each frame was a true 4' wide and cut to length from a 4 x 8 sheet of plywood.

  If I remember correctly I think the glass is 76 or 78" long and must be no less than 46" wide. These are very heavy, I needed to go 3/4" deep with the routered inset for a flush glass to frame fit before installing the aluminum frame, this included the glazing installation seal set under the glass.

 The total exterior depth of the panels less the aluminum frame is 4". The sides are 2 x 4's on edge secured to the back panel with gavanized deck screws and construction adhesive. The flat plate absorber is sheet steel painted with flat black stove paint. This is secured to 1/2" rigid foam insulation (the good stuff with high temp ratings) with pure silicone caulk. The vent holes are 4" diameter.

 As is normal with a first time project I did not work off of plans and have not drawn this yet, I plan to in the near future so as to be able to duplicate it. Thank you both for your interest in these solar hot air panels, they are not as exciting as the wind generator but they are extremely effective even way up here in NY.  Dave B.

[willib]

Thats great news on their heating properties , very impressive!

[CmeBREW]

Thats Good news Dave.

I am impressed to.  I can certainly believe the way your cabin acts like a thermal heat capacitor to keep the warmth going all night.  Mine does the same thing-- but I am not certain if the 'thermal capacitor' warmth is coming from my cement slab or if its mostly coming from all the accumulated drywall on the walls and ceiling??

Would be nice to know.  If it WAS mostly the drywall, then It might be better to put extra 5/8" drywall (or whatever)on/in the walls and have somekind of pipe/hose air circulators in the walls to heat it from the back side first?? (just thinking out loud) I don't really know.

I was concerned it could get TOO hot in the rooms in the middle of the day.

Good work.

[scottsAI]

CmeBREW,

Heat is stored in Mass: Drywall, concrete, wood etc. Wood is not very good, has the mass yet an insulator too. Insulation acts as a resistor to absorbing the heat.

Tanks of water work great, people use columns of water to store heat. My preference is to make a large tank and store it there... take it out when needed to control temperature.

Slab concrete; could store heat, if on soil directly no insulation under it will loose as much as it stores, depend on ground temperature. Heat goes up, only the cooler air is on the slab.

Search on thermal mass heat storage, find all the hot ways people store heat!

Have fun,

Scott.

[Dave B]

 "Heat is stored in Mass: Drywall, concrete, wood etc. Wood is not very good, has the mass yet an insulator too. Insulation acts as a resistor to absorbing the heat."

  Just have to add a bit of a plug here. http://users.netsync.net/~bruggelog

 Log homes properly built have a huge amount of thermal mass and act as a good insulator besides. Fill it up with hot or cool air and allow the temp to stabilize and you have tremendous storage capacity. Unless you live in one it can be hard to appreciate this concept. Thanks for all the comments.  Dave B.

[willib]

I wonder what they used to use for a roof, before plywood ?

Your log homes are cool looking

Bill

.

[dlenox]

Dave,

Thanks for the dimensions, making a metal note on this...

Dan

[Jon Miller]

'Log homes properly built have a huge amount of thermal mass and act as a good insulator besides. Fill it up with hot or cool air and allow the temp to stabilize and you have tremendous storage capacity.'

Log homes are not prone to having 'huge' amounts of thermal mass.  The reason the temperature stabilises is the properties of the wood are stopping heat leaving or entering, acting as a good insulator.

Concrete, stone or water are very good mediums for retaining heat within this context.

The concept in hand here is passively heated retro fitting technologies.  Full blown passively heated homes have tonnes of thermal mass and can achieve average temperatures of 20 deg C all year round.  But require a larger degree of forethought on the planning side.

To any one reading this, build a solar thermal panel, a well built one will save you thousands of kWh's a year in heating!

Regards

[Dave B]

Log walls are "massive" and are very energy efficient when properly built. I use the term mass as in the Log Home Industry the term "Thermal Mass" is used to set apart Log Homes from standard stick built in regards to their energy efficiency. Either way it certainly works as soon as you understand there is the lag time of heating up slowly until the temp stabilizes and cooling down slowly in the same manner.

  I agree Jon about building solar. I still cannot believe how well these solar panels work, I chuckle every time they kick on and off and the heat they provide. Thanks for your comments.  Dave B.

[carlb23]

We also have two hot air panels on our home for a total of about 160 square feet. Our home is 2650 sq feet and these panels provide about 1/3 of the heat need to heat the house.  The other 2/3 thirds of our heat comes from an air source heat pump that runs totally from the electric we produce with our 10kw solar array and 1.8kw wind turbine(grid tied net metered). We can heat, cool and supply all of the electricity for our home from renewable energy. Next to the PV array the hot air panel's have had the largest impact on our energy usage.

[Dave B]

Yes,

  Thank you for posting about your system and hot air panels. I knew they would work but just as my wind generator made me so aware of the power in the wind so has my solar panels. With a good 12 MPH wind and the sun shining I am generating an equivelant of 3500 watts direct as heat. Kick the wind up to 20 MPH and this total jumps up to 5000 watts.  When I think of this in terms easier to relate to such as 35-50  100 watt light bulbs burning bright from the grid it really makes me chuckle.

  It is mid May and this evening they are calling for frost. So far I can see the hot air panels to be useful for 9-10 months of the year. They have only been up and auto running a couple of months now but man would I miss not having them already.  Dave B.

[Dave B]

 Another observation in regards to the sun angle and vertical mounting. As noted these face near due South and as you can see are mounted vertical.

 Here in Western NY I'm at 42 degrees N Latitude. In February on a sunny day these were turning on at around 9:30 AM and now here later May that is about 11:30 AM. Obviously the angle of the sun is reflecting more off the dual pane glass (just as this glass was designed) which is helpful as the weather warms up. We had frost for several nights still and mid 40's for May evening temps is still frequent.

 I am not in a big hurry to cover these as the heat collected during the day is still useful at night, I can always open the windows. The usefulness of these panels has far exceeded my expectations, what a great project.  Dave B.

[HenryVG]

Dave:

I'm looking at the construction again. Are the interiors of your panels just one big area or are there baffles in there to make some kind of serpentine air flow?

[Dave B]

Henry,

  Yes, there are 3 baffles made from bent sheet steel and pop riveted to the steel absorber plate. The photo here shows it before the glazing and flat black stove paint. This was a smart move as the air seems to wash off the heat from all areas of the inside of the panel. Without this sepentine air moving I would miss much of the heat as most of the air movement would be vertical only straight between the vents. Opposite diagonal corners for the vents would have been more ideal but my installation prompted this arrangement. Thanks for asking, these are a great addition.  Dave B