New design for Solar Air Heater (reposted)

I recently finished building and initial testing on a Solar air heater, and the results are promising. Being from Colorado solar heat makes a lot of sense.  The collector is based on a design that can be found many places online as well as one that is manufactured in Canada by Cansolair.  From there I made some changes that I believe will increase efficiency.



Like most, it is approximately 4' by 8 foot.

The main heat collector core is made from recycled soda and beer cans.


Here is where the difference lies. My design uses 192 cans instead of the normal 240.

 

Most collectors have the can columns right together with no space between them. My feeling is, with the sun directly in front of the collector each column has 50% surface showing, and 240 cans.
 
The sun is only directly in front for a short time. The rest of the time the sun is hitting at an angle and each column is partially hiding the one next to it.
 
In my design I have spread the columns apart to eliminate the shading up until almost 45 degree sun angle, which was my target. I then put a reflectorized, insulated panel behind the Columns to reflect light, and thus enegrgy to the back side of each column. This way even though I have 20 percent fewer cans, I get 50% coverage at 45 degrees and far greater at lesser angles. pretty much 100% at times.  This spacing is seen often in Solar water heaters.

The above photo shows that at about 9:30 in the morning, with about 68 to 70 degree ambient temp. I was producing 150 CFM of 100 degree air.

I also increased my blower size by 50%  (to 150 cfm)  and use a blower instead of an axial blade fan. A blower is more efficient with higher volumes and handles static pressure better.

At these settings the fan runs constantly but I am getting a virtually 100 percent heat exchange. With the panel laying on it's back to mimic mid winter sun angles, during constant operation and 100 to 110 degree output, the Polycarbonate cover stays about the same temperature as the ambient air.  This tells me that there is no heat being generated in the cabinet and being lost through the front.

If I shut the fan off for a few minutes the temperature rapidly climbs as high as 140 degrees.  To decrease the electrical requirements I could cycle the fan as there is a 20 degree differential fan switch installed (above).  In this scenario I would be outputting less air, but it would be hotter.  The down side would be there would be some heat loss through the cabinet front.  I have not yet figured out how to calculate the best operating methods.

In the next few weeks I plan on getting the collector installed and running, and will also post a link to a website I am creating with better instructions, should you want to build your own. I estimate the cost of this system at about $350.00

There is a fair amount of labor involved but is not that hard for someone that is a little handy.
 

Update,

The collector has been installed for a couple of weeks. Performance is everything I had hoped for. Currently it runs about 5 to 6 hours oer day. Total electricity draw is 75 watts.  Although the cold weather is just hitting here, two examples:

The collector runs from about 9:30 am to between 3:30 and 4:30 PM. On a recent 52 degree day, the temp in the house at 4:00 was 71.

After leaving for a long weekend, the high temps were in the low 50's and the lows in the low 30's. The thermostat was set a 55 degrees.
At 7:30 PM the temp in the house was 61. Monthly electric use was 363 KWH,  32% below the same month last year. Nat gas showed a 40% savings. (there are some other new programs in place as well).
Website with more info soon!

Well Russ, here it is. I still have a little editing to do, but it is 99% there.

http://homesolar.webs.com

Bill

Interesting, it works for me. Maybe someone else can chime in on whether it works for them. Try copy and paste into your browser.

Follow up report.

I have been very pleased with the performance of this project. It is impossible to tell what my actual savings are because I installed an efficient Fireplace this summer as well.
My november gas bill, excluding fac charges taxes, etc was $10.91  (22.486 CCF)
40% of last year. Electrical use is down 35%.

The collector is set to supply hot air at about 112 and above, it usually runs about 112 to 118. It runs for 6 to 7 hours on sunny days, partly cloudy days it will cycle on and off.
This morning it started up @ 9:00 a.m. The outside temperature was  -7 degees F.
It cycled for about 30 minutes, then ran steady.
The electrical use based on 6 hours of operation is 4 cents per day. (75 watt draw)

We keep our setback thermostat set @ 69. The furnace might run in the early morning for a while but never in the daytime or most nights.
Average room temperature is 72 to 74.

Well, I just thought I would bump this and give an update. It has been over two years since we have installed this heater. The performance has been great. We also installed a Efficient Fireplace, (EPA certified) and over the last two years, our Gas consumption for heating has been almost Zero. Only if we are away do we turn the furnace on.  The solar heater greatly reduces the amount of wood we need as it maintains the home temp all day on sunny days (2800 sq ft home) On a nice day it will run a little over 6 hours per day, because of sun angle.

A typical winetr day like today in Colorado, 1 degree at sunrise, warming to 40 during the day, our home will be about 72-73 inside.

 

I do love the $20 per month Gas bills.

 

The photos are a little funny due to website reformatting but feel free to visit my website above for more info.  I have nothing to gain by sharing this information, I just want my planet to last a little longer.