Solar Air Heaters

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Old 11-15-08, 06:01 AM
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Solar Air Heaters

We took the leap and purchased and installed a solar air heater the beginning of November / 08.

It was easier to install than I had thought.

I was curious if anyone has been using these in their own home and what results they are seeing?

**********
What I am curious about is why more folks are not using these to help generate heat without consuming home heating oil or natural gas? It is because they don't want to install on the south facing area of their roofs? Or is it because it's so new? Or ...

Thanks for your thoughts,
Dan
 

Last edited by GregH; 11-16-08 at 04:45 AM. Reason: Remove link to personal blog.
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Old 11-18-08, 12:03 PM
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Got a link to the manufacturer? Pics of the install?
 
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Old 11-18-08, 12:13 PM
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Originally Posted by xiphias View Post
Got a link to the manufacturer? Pics of the install?
Hi xiphias,
I did have a link to articles on our home blog we are writing, yes with pictures, about our instllation, etc.. Howevever, I didn't know that was against the forum's rules and it was removed.

I did just add a did-it-myself project here ( http://www.doityourself.com/did-it-m...lar-air-heater ) per the advise of the Moderator with a couple of pic's.

Do you have any experience with these? No one has answered other than you which is confirming my suspiscions that most folks still don't know about these.

Dan
 

Last edited by Educator001; 11-18-08 at 12:42 PM.
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Old 11-18-08, 12:46 PM
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Educator...I went to the original link and saw the pics, but it looked much more like a sales page than a home blog, IIRC. Ad's and links all over the place and such. Thats prob why it was removed.

I'd like to see further pics and info as well. I live in AZ and even on cold winter days a little experimental solar heater thing I made was giving almost 10F rise over 2-3ft tubes.
Same with my garage, sun on the interior slab will rise to 90F or more on a 60F day and when the door is closed, will keep the garage in the 60's all night, even with outside temps in the low 40's. Don't plan on redoing the whole duct system or anything, but might consider some sort of DIY unit for my garage as a project.
 
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Old 11-18-08, 12:57 PM
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Originally Posted by Gunguy45 View Post
Educator...I went to the original link and saw the pics, but it looked much more like a sales page than a home blog, IIRC. Ad's and links all over the place and such. Thats prob why it was removed.

I'd like to see further pics and info as well. I live in AZ and even on cold winter days a little experimental solar heater thing I made was giving almost 10F rise over 2-3ft tubes.
Same with my garage, sun on the interior slab will rise to 90F or more on a 60F day and when the door is closed, will keep the garage in the 60's all night, even with outside temps in the low 40's. Don't plan on redoing the whole duct system or anything, but might consider some sort of DIY unit for my garage as a project.

'IIRC'? Sorry, I don't know that acronym. Quick definition please.

As for more pic's I don't know what to tell you. You can use google with all kinds of search terms for this topic to go to sites of actually manufacturers who will have all kinds of pic's of their particular product.

For a garage, you would want a different mgftr than the one from whom we purchased our unit as they have, as far as I know, just one size. There are other mftrs (again, just use your favourite internet search engine) who offer different sizes. The unit we purchased is to heat a 1,000 square foot area .... I can't remember the last time I was in a garage of that size.

Dan
 
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Old 11-18-08, 01:06 PM
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IIRC=If I Remember Correctly..........that happens a lot with the old folks on here...like moi...lol.

Ok, well, I've seen a DIY solar heater site or 2. I'll keep looking til I find what may work. Mines only about 400sf...but there are plenty out here much bigger than that.

Thx for the response.
 
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Old 11-18-08, 01:12 PM
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Originally Posted by Gunguy45 View Post
IIRC=If I Remember Correctly..........that happens a lot with the old folks on here...like moi...lol.

Ok, well, I've seen a DIY solar heater site or 2. I'll keep looking til I find what may work. Mines only about 400sf...but there are plenty out here much bigger than that.

Thx for the response.
Thx, Gunguy45, for the clarity.

Actually, it's not a sales page ... it is a blog that we write about our home reno / energy conservation experiences. You might have caught it on a day when we were writing about a contest.

You might look up 'SolarSheat'. They are one that has different sizes, including one if I remember correctly for a 500 sq. ft area.

Dan
 
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Old 11-19-08, 03:05 AM
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Easy to install

How easy to install the solar water heater? is it work efficiently? since need a lot of sun light...
***************
 

Last edited by GregH; 11-20-08 at 01:55 AM. Reason: Remove advertising link.
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Old 11-19-08, 03:34 AM
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Originally Posted by juanmraz View Post
How easy to install the solar water heater? is it work efficiently? since need a lot of sun light...
***********
Hi juanmraz,

I have no idea about solar water heaters. We are still waiting tyo received our in-home visit for the installation cost for one we have our eye on.

I was asking about solar air heaters / collectors, not solar water heaters.

Does anyone have any experience with solar air collectors? I can't be the only one .... then again, I am starting to feel lonely.

Dan
 

Last edited by GregH; 11-20-08 at 01:56 AM. Reason: Remove advertising link.
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Old 11-19-08, 05:06 PM
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Wow- where was this topic when I was desperately seeking info here last spring?

OK - I've calmed down ...

I did some searching (Mazria's Passive Solar Energy Book, websites, Mother Earth News, and others). Decided to build my solar air heater, as I couldn't justify the prices of manufactured units if I wanted to save money on heating costs (oil heat here in New England).

My kitchen south wall is about 8x8'. Good sun exposure - has a 2x3 double sash window in the wall. So I just built a "box" as a second layer of the south wall.

Box is 8x8', 8" deep. Basically just four 1x6 boards forming the shell, with 3.5 mil clear plastic stretched over it. Inside the box I tacked aluminum sheets (painted flat black) on the clapboards of the house.

Cut four 6" diameter "vents" in the wall near the floor. When the sun hits the box - from about 9:30am to about 3:30pm - I lower the top sash of the kitchen window. Air of about 120-130 degrees moves really fast into the kitchen. Cool air on the kitchen floor is pulled into those four floor vents, travels up past the hot metal sheets, and enters the kitchen through the window.

No moving parts other than "saran wrap" self-actuating vents that close themselves when the solar air is no longer warmer than the kitchen air.

Here's a link to the Mother Earth News article which gave me the basic idea:

Solar Wall Heater

And a picture of one very similar to mine:



Questions always appreciated!

Tom
 
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Old 11-19-08, 10:46 PM
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This could be a great idea, maybe i need to get more details on how to do it. Thanks for sharing.
 
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Old 11-20-08, 02:36 AM
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I've been asked why I built my own instead of just purchasing a commercial solar collector.

The SolarSheat mentioned in an earlier post starts at around $1000.00

ack!

Here's a link: SolarSheat

The one I built cost me $65 in materials. I realize the SolarSheat probably works at least as well as mine, if not better. But it would take me a *lot* of heating oil savings to equal the $1000 cost of that SolarSheat.

Be still my beating heart!

Tom
 

Last edited by NutmegCT; 11-20-08 at 03:02 AM.
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Old 11-21-08, 04:08 PM
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Lonely?

Dear Educator, don't feel lonely. I find talking about my solar air is received as bragging so I don't mention it, ever.
Why don't more people heat with solar? Most people don't live in Wisconsin and have propane dealers with 50% higher bills motivating (angering) them into action. I was being motivated every three months. Some solar extended motivations to every six months. Even more solar plus weatherization extended motivation intervals to 1.5 years.
I scratch built both solar air and water. Air heaters are simple and cheap to diy. Collectors are easy to custom build and mount. South wall mounting will get more heat in winter and none in summer. Water heating is difficult and expensive but used all year. No fuel is used nine months a year. When December and January is overcast the temperature is moderate. When it's really c-cold, it's sunny. For 1500 living space, I have 80 s.f. solar water and 120 s.f. solar air. No regrets http://www.builditsolar.com/
 

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Old 11-21-08, 04:40 PM
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Hey mcircus and NutmegCT,

I am personally very jealous of the both of you.

I know that I have more than 2 thumbs on my hands. I can do some renovations and home maintenance projects but I know my limitations. Plus for me there's the time factor.

However, I had a really great guy help (when I say help I really mean he did most of the work and I was his not-so-trusted assistant) to install our unit. I was amazed and the accuracy of his measurements for the mounting brackets on the outside of the south facing wall, the positioning of the holes cut in the wall for outflow of the cool air from the house and the inflow of the sun heated air back into the house vis-a-vis the openings of same in our unit. Everything was spot on.

For the both of you, how are you measuring your actual savings on your winter heating bill? That is the question I am being asked the most (in addition to certain installation tips).

I mean I did purchase one of those hand held laser temperature reading devices (on 50% sale at my local hard ware store) and it showed readings of between 115 F to 125+ F in the ceiling vent through which the sun heated air was entering the house via a 24 foot insullated flexible duct.

But, that doesn't address how to measure the savings, now does it?

Is there an easy way to measure the savings other than just compare this year's heading bills to last years, taking into account the degree (pun, intended ) of diffference in general outside temperature between this year and last?

Thanks!
Dan
 
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Old 11-22-08, 05:06 AM
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savings and payback

Originally Posted by Educator001 View Post

<snip>

Is there an easy way to measure the savings other than just compare this year's heading bills to last years, taking into account the degree (pun, intended ) of diffference in general outside temperature between this year and last?

Thanks!
Dan
Morning Dan!

Not exactly an easy way, but what I did was to find the BTU output of the box, and translate that into equivalent electricity costs for the BTU's I'd need to heat the space if I didn't use the solar.

I could do the same using heating oil costs, but that gets really tricky, as when I use my oil burner furnace, it heats the entire first floor - not just the kitchen I use the solar collector on.

So ... I used air temp rise (cool kitchen floor air temp at box input compared to warm air coming out of box's top vent). Rise at noon on a sunny day is about 60 degrees (floor air was 60, warm air output was 120). Remember, that's an average of sunny day noon-time temps over several days, but close enough for me.

The volume of warm air coming from the top vent is material, as you want to know how *much* warm air is coming out, not just the temp. For me, I took the square footage of the top vent (1.5 sqft). Then measured the velocity of the air coming out (110 ft/minute). This last was fun - used a light plastic garbage bag, and measured how long it took to "puff" it up. That's where the 110 ft/minute comes from.

I followed the formula at BuildItSolar:

Measureing solar collector performance

My numbers were very similar to the example, and I found I was getting about 9000 BTU/hr from the solar collector.

9000 BTU = about 3 KW in pure electrical heat.

Here in Connecticut, a KWH costs about 20˘. So I get 3 KWH, or 60˘ worth of heat an hour. Six hours daily of use, I get about $3.60 worth of heat - for free. But you have to take into account the *cost* of the collector unit, whether you buy it or build it yourself.

Once I've deducted the cost of my home-built collector ($65), the rest is pure savings.

Cost of collector - $65 - divided by $3.60/day savings = unit has paid for itself in 18 days.

So I guess I'd be reluctant to spend, for example, $1000 for the SolarSheat 1500 which, per the manufacturer, outputs 6000 BTU/day. Not sure why it says per day, and not per hour, but I'm going on what the manufacturer says. And that particular model 1500 actually retails for much more than $1000. The "6000 BTU/day" really doesn't sound like much heat at all.

For me at least, I couldn't justify spending over $1000 to obtain 6000 BTU/day. It would cost me 60˘ to get 6000 BTUs in a day. Divide the $1000 by 60˘ and you find it would take over 1600 days of use to recover the initial $1000 spent on the collector. And that $1000 is about the cheapest "large" size collector I've seen for sale.

One thing to keep in mind: it's not just the temp difference of the incoming warmer air that matters. It's the *amount* of incoming warmer air that matters.

Simple example - if the box were outputting 1000 degree air (ha ha), but you only got a dribble of it, you wouldn't be heating that living space up very much.

As a friend of mine used to say - there are simple answers. And there are correct answers. But there are very few simple, correct answers.

Hope this helps.
Tom
 
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Old 11-27-08, 05:57 AM
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Smile Window box unit

coffee: goodmorning and Happy thanksgiving,what you say is super nice as i been green all my life, as thay call it now, and i'm 52 and never,ever stop learning to live off mother earth, she is my mother and such we have to take care of her, so like your ideas, which is fine , if you own your own place's. however we need to think outside the box, i live in Des Moine's, Iowa. usa, and would like to start a group like this, to discuss solar and gen related items,at our libary, now why i say think outside the box, becuse most you own your own home, and most rent, that weres were i am and we cannot modify a house, so we need to think outside the box for the renters. i look'ed on the net, i'm brand new sorta to the coumpter world, 6 years,found a sloar heat unit ,and for to work the best be in south , i agree with that , i rent a room in the west , have big double widow, so i put my therometer on a box 3 feet from the window, yes i got out my compass and maps and longtude, mesured all that and i ran it up 89 np,so why cant i stick this on my widow ledge for free heat, and its only $259 with fan, i can build it,but not any cheaper, i am somewhat handyman too, Everett.
 
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Old 11-27-08, 09:56 AM
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Hi NutmegCT,

Someone who left a comment on another site said I should get an infra-red device from the hardware store (which I did ... it was on a 50% sale ) to measure the temperature of the heating vent through which the heated air enters the house from the solar air collector.

So, this I did. At around 7 am I measured an average temperature of around 70 degrees F on and in the ceiling vent. Then around 11:30 on a day when the sun was out I did the same thing and was consistently getting results from this infra-red hand held device of between 130 and 140 degrees F.

So, simple math of subtracting one set of readings from the other gives between 60 and 70 degree F temperature rise from the solar air collector.

Would this be an accurage guage of the temperature rise do you think?

However, this is in the basement. Warm air rises. The air inflow into the solar air collector is 1 foot above the basement floor, not the basement ceiling. I used that infra-red temperature device on the air intake device as well as on the wall around it and came up with temperature readings of between 50 and 55 degrees F. If I use that range of temperatures, then I get a temperature rise of around 80 to 90 degrees.

That seems too high to believed.

What do you think?

Thanks,
Dan
 
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Old 11-27-08, 02:42 PM
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Dan - looks like you're getting some great heat rise!

I think the "standard" way of measuring heat rise is to use the air temp at the cool air input vent (bottom), and the air temp at the warm air output vent (top). The difference between the two is the actual the temp difference made by the solar collector.

So in your case, you're getting a really good temp increase.

But don't forget the second step: how *much* air is moving through the collector?

Take a look at that site I linked to in my earlier post, on "measuring solar collector performance". You'll learn how to measure the *volume* of air coming through the system. You want to find out how many cubic feet per minute or per hour.

It's not just the temp increase that counts, it's how much of that warmed air is actually being moved through the system.

And personally I think it's also important to see if you're actually saving anything dollarwise. How much would it cost you to get that same temp increase using some other heat source, like electric, or gas, or oil, etc. that you'd have to pay for otherwise.

I suppose someone might say - well, I wouldn't even think of heating the basement because we don't use that space. In that case, you're not really saving much at all, as the price you paid for the unit isn't "saving" you costs that you were already paying.

If it takes someone only a few days, weeks, or even months to recover the initial cost of the unit, it's probably great. But if it takes many years, maybe not so great.

The post just before yours asks about using a "window unit" for around $259. Might be a good idea, if you actually save at least $259 by *not* paying for other fuels (electric, oil, gas, etc.). If you never recover your initial cost, you're not really saving anything.

(Unless you're just trying to feel better by using solar instead of another energy form; if that's the case, it's always a great idea!)

I think what I'm getting at is that I can't justify saving $100/year in fuel oil by spending $2500 for a solar collector (for example). It would take 25 years of savings to just get even.

Just my 2˘ worth!

Tom
 
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Old 11-29-08, 04:41 AM
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Sorry, collectors behind an existing window do nothing except darken the room. Save your money and open your blinds. It's a rip off.
Only credible way to determine fuel saved is to meter fuel used.
A outlet temperature of 130 is par but keep in mind that a cooler collector will lose less heat and deliver more Btu's. As for placement in the basement. Perfect, they knew what they were doing.
 
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Old 11-29-08, 05:28 AM
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Originally Posted by mcircus View Post
Sorry, collectors behind an existing window do nothing except darken the room. Save your money and open your blinds. It's a rip off.
Only credible way to determine fuel saved is to meter fuel used.
A outlet temperature of 130 is par but keep in mind that a cooler collector will lose less heat and deliver more Btu's. As for placement in the basement. Perfect, they knew what they were doing.
Hi mcircus,

Can you explain what you meant by your comment "...a cooler collector will loose less heat and deliver more Btu's."? I'm not sure I understand what you mean?

Thanks,
Dan
 
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Old 11-29-08, 05:46 AM
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Dan,

Just a quick comment about your temperature measurement.

An infrared thermometer is a very useful tool but may not be the best for what you are doing.
Infrared temperature measurement relies on reflected infrared light from whatever surface you are measuring but a problem arises with the gloss and texture of the surface.
Surfaces with different reflective qualities will give different temperature readings when they are at the same temperature.
Most IR thermometers have an emissivity setting to allow for this but there is a steep learning curve in becoming proficient at this.

A better way of monitoring your collectors performance is with a pair of inexpensive remote reading digital thermometers.

Click image:

Image courtesy of thesource.ca

If you were to put the sensors at the grills or drill a small hole in the supply and return duct and drop in the sensor of the thermometer you would have an accurate indication of the temperature rise.
 
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Old 11-29-08, 06:16 AM
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So I need to go out and buy yet another gadget that I don't have????? Just kidding.

I have seen various digital thermometers and what I don't like is how some will not give the reading of actual air temperature but of the casing surrounding the device itself. Different types of materials used in the outter casing of the device will cause different digital thermometers to give different readings. I've seen it many times in different models. So how is one to know which model will or will not give a reading impacted by this? Likely it's the more expensive variety ... and there we go again with cost issue.

As well, the cheaper the device the less accurate the measurements it displays.

I'm pretty happy with the readings we have from the I R device for a few reasons:
    • I have to think that since I have the reading from the same ceiling heat vent (A) at 7 am and (B) again around noon-ish once the unit has been on for a while, that any variations are elimiated because it's the same material composition since it is the same ceiling venet
    • While the material in the ceiling vent, the solar collector intake vent at the bottom of the wall and the wall itself may be different materails, I can't imagine that there would be a 20 degree F difference between them using the I F at 7 am.


    At least, that's my take.
     

    Last edited by GregH; 11-29-08 at 08:06 AM. Reason: Remove quote, not necessary
      #23  
    Old 11-29-08, 07:07 AM
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    Dan - how did you measure the *amount* of air circulating through the collector?

    Temp is only half the equation. What's the volume of air actually moving into the room?

    Tom
    PS - I agree with Greg about the IR thermometer. Not really measuring what you're looking for.
     
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    Old 11-29-08, 08:16 AM
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    It is true that a room type digital thermometer will be affected by the case but in many instances this can be a benefit.

    The mass will help by stabilizing the reading slightly giving you an average temperature but in most of them the average is only spans minute or so.
    If you have a remote reading thermometer like I showed you there has to be averaging in the display or the temps would swing too much.

    Instantaneous reading thermometers are very much used in the HVAC/R industry but are a specialized tool and could be more of a frustration as the readings would swing too much for most folks.

    Inexpensive digital thermometers can be just as accurate as the best.
    For what you are doing you would not be as concerned about the accuracy of the actual reading but more the difference between two readings.

    Uh, just so we are clear, the thermometer I showed you has a bulb attached to a wire that is placed in the air you want to measure.
     
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    Old 11-29-08, 08:17 AM
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    Originally Posted by NutmegCT View Post
    Dan - how did you measure the *amount* of air circulating through the collector?

    Temp is only half the equation. What's the volume of air actually moving into the room?

    Tom
    Hi NutmegCT,
    I haven't yet; ... too busy what with the holidays Beer 4U2, car breaking down and already working O/T at work.

    I haven't even checked out that web site you referred me to yet.

    I will get there.

    I'm not too worried about the actual calculation results because (A) I did not build it myself (B) the product is CSA approved and (C) the product is on the list of approved solar air collectors eligible for rebate from the CDN government for certain buildings, so I know the thing works.

    However, I will get there as I am curious to see if my calculations from our install are at least in the ballpark of the manufacturer's estimates.

    Dan
     
      #26  
    Old 11-29-08, 11:04 AM
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    Originally Posted by Educator001 View Post
    However, I will get there as I am curious to see if my calculations from our install are at least in the ballpark of the manufacturer's estimates.

    Dan
    Sounds good. As you said earlier, you're concerned about "how to measure the savings", and not just the heat output.

    Seems there are lots of people interested in the time it takes to recover the initial price of the unit.

    Thanks.
    Tom
     
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    Old 12-01-08, 03:47 AM
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    Possible pitfalls

    Possible pitfalls. Beware of drafts, materials and design of construction. Some examples. Daily heat gain means nothing if at night the collector is a drafty ice cube. Styrene insulation melts. Ducts need dampers (check valves) to prevent reverse convection. I've found many materials designed for green houses are perfect for solar hot air.
     
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    Old 12-05-08, 06:52 PM
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    Those of you that have installed systems, what do you plan on doing in the summer? I need a system that looks good, if I choose one. It seems like you would have to cover them in the summer. I would just think they would get too hot to just close the vents.

    I'm also interested in the thermal performance of the box at night. How much heat is lost through the vents, even if they have a flapper?
     
      #29  
    Old 12-06-08, 04:06 AM
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    Chris - good questions. In the summer I'd open the top of one of the plastic panels (a couple wood screws); it's screened and under the sloping "roof" so there's rain cover. One of my concerns on the $1000+ manufactured units is how you keep them from overheating in the summer. If the vents are closed, all that heat builds up inside the unit.

    As far as heat loss at night, I actually don't know how I'd measure that. But as the flappers only control air flow, I just put an insulated panel across the vents after the sun goes down. That way there's essentially no heat loss at all.

    Tom
     
      #30  
    Old 12-06-08, 04:11 AM
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    Originally Posted by chris8796 View Post
    Those of you that have installed systems, what do you plan on doing in the summer? I need a system that looks good, if I choose one. It seems like you would have to cover them in the summer. I would just think they would get too hot to just close the vents.

    I'm also interested in the thermal performance of the box at night. How much heat is lost through the vents, even if they have a flapper?
    Hi Chris,
    What I plan to do is to use left over solar shades which I use onr our south facing windows year round. I can simply use the adhesive clips on the sides of the solar air heater and then during the summer place this screen like material to cover the solar heating unit. I am not anticipating any problem at all.

    As for the amount of heat lost at night, as far as I can tell none. The air intake area has a flap that closes when not in use. I used an infra-red temperature reading device around 7 am one morning and noticed only 2 or 3 degree F difference between the temperature of the blower assembly (that's what the manufacturer of my unit calls the intake valve) and the adjacent wall.

    I hope that helps.
    Dan
     
      #31  
    Old 12-08-08, 12:14 PM
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    Kris Summer sun has a high angle hitting the collector so it doesn't heat. If the collector is under a overhang it's in the shade and might even cool just a smidgin.
     
      #32  
    Old 01-31-09, 07:19 AM
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    Originally Posted by mcircus View Post
    Kris Summer sun has a high angle hitting the collector so it doesn't heat. If the collector is under a overhang it's in the shade and might even cool just a smidgin.
    Hi MCircus,

    Wouldn't this depend on the location of the solar collector? I mean, if it is on the roof, then it will become heated as there's no way for the sun not to have direct access to it.

    I do agree that if a wall mount, the sun should not heat the unit as much but I still think it will still have a significant impact.

    The location of our wall mount I don't think will cause the shae from the roof overhang to create too much of a shadow on the unit.

    It will be interesting to see how this all works out for our unit and it's location this summer. I'll report back and let y'all know.

    Dan
     
      #33  
    Old 02-02-09, 08:57 AM
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    Smile My 2 cents

    DIY: Building a Solar Space Heater thx to Residential Solar Panels



    This type of solar space heater works by drawing the air to be heated into the bottom can of a column of cans. The air is then heated inside the cans by the sun’s energy and the hot air within them rises upwards (thanks to convection) to be fed into a pipe which re-enters the building to be heated.

    1° Building the Box - First of all make a box out of whatever scrap materials you have to hand. Set the dimensions to that the width of the interior of the box is exactly the same as the width of however many columns of cans you would like to use in your heater.

    For increased efficiency, you may choose to insulate the box to prevent heat escaping (by conduction) through the plywood. If so, size your box so that the cans and insulation will fit snuggly.

    2° Drilling the Cans - For the air to pass through a column of cans, holes must be drilled into them. Remember that there is already a hole at the top of each can out of which the drink is poured. That just leaves holes at the bottom of each can to be drilled.

    In the bottom can of each column a 1/2 to 1 inch hole is drilled in the side. (see image below) - Drill a hole in the side of the bottom can of each column - The rest of the cans in the column have a similiarly sized hole drilled into the bottom. See image below)

    3° Building the Can Columns and Painting - Then the cans of each column are glued together using caulk or silicon adhesive and painted using black paint to help them absorb the sun’s energy. Barbecue or fireplace/stove paint is excellent for this as it will not flake off, but any marine grade paint will do a similar job - just make sure it has a totally matt finish.

    The inside of the box must also be painted with the same paint before the columns of cans are glued into position using caulk or silicon adhesive. The outside of the box should be treated with preservative, varnish, or paint to help it survive the elements for many years.

    4° Sealing the Solar Heating Box - Ideally the whole unit will be sealed with a sheet of tempered glass - of the type used in car windscreens. This glass is very strong and resilient to heat. However, tempered glass (unless you can find and recycle a sheet) is also very expensive. Therefore plexi-glass (plastic) can be used, but it will degrade far more quickly and become opaque blocking out the sunlight.

    A hole at the top of the box acts as the hot air outlet and can be connected to the building/room to be heated using an insulated pipe.

    5° A PV Electric Solar Panel could be used to power a small fan (such as that used to cool the processor in a computer) to drive air through the snake. The final temperature achieved would be lower, but having a large quantity of 30 degree Celcius air entering a room is much better than a much smaller quantity of 50 degree Celcius air.
     
      #34  
    Old 02-04-09, 09:21 AM
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    solar air

    I have a two story with a wide, windowles S facing wall. Would it improve performance to take in the air from the bottom of the first floor and eject it into the top of the second floor? In other words, if the dimensional width of a wall-mounted solar air heater remains constant does increasing (in this case doubling) the height increase tempature output, velocity or both?
     
      #35  
    Old 02-05-09, 04:26 AM
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    Now what?

    height will increase temperature output, velocity or both. The snag is all the heat is at the ceiling upstairs.
     
      #36  
    Old 02-05-09, 05:42 AM
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    So I guess the ideal is to remove cold air from floor level of 1st floor and supply it at floor level of the 2nd floor - thanks.
     
      #37  
    Old 02-05-09, 07:59 AM
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    It would be better to discharge air at the floor level on the second floor but you would not be adding much height and therefore capacity to the collector.

    IMO when you install a collector like this you will achieve maximum benefit from heating a specific area.
    By installing the intake and exhaust in different areas of the house you will be adding heat to the entire structure but it will not allow you turn off or lower the heat in a specific room.
    Also, by making the airflow from the collector circulate from the second floor to the main, any closed doors and distance traveled would impede air flow.
     
      #38  
    Old 02-05-09, 03:30 PM
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    I'll second GregH's comment. The idea of a solar collector is to "move the btu's from outside the house to inside the house."

    Mine (see above) cycles cool air from the kitchen floor, heats it, then puts the heated air back into the kitchen. No power required; $65 in materials.

    Increasing the volume of air heated, or the speed at which the air moves through the system, won't change the btu's you're getting from the collector.

    The Cansolair RA 240 Solar Max is rated by the manufacturer at 9600btu maximum heat output. So at maximum solar energy (basically, direct sunlight with no clouds or other interference), the energy output is 9600btu, give or take. Move the air faster through the system, you're still getting 9600 btu from the collector into the house.

    And if you're budget conscious, don't forget to consider how much you're actually paying for that collector. The Cansolair RA 240 Solar Max sells for $2700. Even at maximum efficiency, if you're paying 10˘ per kwh for electricity (a very efficient heat source), it will take you quite a while to recover the initial cost, as 9600 btu = +/- 2700 watts. That's 2.7 kw, or 27˘ worth of heat per hour. Think about how many hours you'll actually use it each day, and how many days of full sun you'll actually have during the heating season.

    Hope this helps.
    Tom
     
      #39  
    Old 02-07-09, 02:18 PM
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    Originally Posted by mcircus View Post
    Kris Summer sun has a high angle hitting the collector so it doesn't heat. If the collector is under a overhang it's in the shade and might even cool just a smidgin.
    In Chicago, a collector at 90 degrees avgs 3.1 kwh/m^2 day in Jan., in July it collects 2.7. That is not a very big difference, I've heard plenty of reports of people melting their units while waiting to install them and not providing ventilation.

    look at the IL data or your own
     
      #40  
    Old 02-27-10, 07:36 AM
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    Air flow volume is important

    I agree with NutmegCT's comment that the purpose of a solar air heater is to transfer energy from outside to inside. However, I disagree with his next point about the volume of air being irrelevant. The amount of air you pass through your heater is very important because it is your heat transfer medium. If your air is moving slowly, the collector absorber will become hotter than necessary and this excess heat will radiate back outside before you can transfer it into your house. The efficiency of your collector is dependent on the speed at which you can transfer the heat from your absorber into your house. This requires fast moving air and is also enhanced by turbulence / absorber irregularities. I have seen many solar air heater designs use one or two small 6 in dc fans rated at 100cfm to drive their system. They achieve output temperatures of 40-50 C and think their panel is operating wonderfully. They could be getting a lot more out of their panel if they used more powerful fans. I have built a solar air heater for my house and used a 500cfm fan to keep the absorber operating efficiently at a low temperature. I have posted all of the details here:
    *******
    It's been a learning process so you might as well learn from my mistakes.
     

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