Question:
I have a 12′x24′ shed which I use to house my AE system. The shed is also used as a workshop. Last year I completely insulated the shed and would like to begin working on either a passive solar heating source or use the AE to heat the shed. I would like to avoid using the AE. During the summer I have more than enough energy to power the house, but during the winter the system provides just enough. I have 24′ of southern exposed roof on the shed with two angles to choose. Its a gabel style of roof, one angle is about 60 deg and the other is 30 deg. I am considering four 2×2 skylights on the 60 deg angle roof, and installing ceramic tile flooring to absorb the heat during the winter months. Someone else recommended installing a few more solar panels and using the extra energy to power a standard electric heater. There is no means of shading the skylights during the summer months. In order to prevent to much heat to build-up in the summer I installed several ventilators. For the skylights I am planning on installing an inner door which will have a light difusing panel which I hope to block most of the heat and still allow the light to pass. Looking for any suggestions on heating and cooling the shed. Brian Colorado
Response:
> roof on the shed with two angles to choose. Its a gabel style of roof, one > angle is about 60 deg and the other is 30 deg. I am considering four 2×2 > skylights on the 60 deg angle roof, and installing ceramic tile flooring to > absorb the heat during the winter months.
Not the greatest plan, if you want heat. If you want skylights, fine. But you’re putting large poorly insulated holes in your roof, and going for 1970’s passive solar, which really never worked outside of Arizona/New Mexico. If you want heat, wander off to google and look into the archives for a number of good thermal solar collector designs – particularly the fan driven "furnace filter" collectors (the furnace filter is used as the adsorber) and Nick Pine’s "sunspace" concept (put a leanto "greenhouse" with no plants, as it gets cold at night, alongside your shed for daytime heat collection). > Someone else recommended > installing a few more solar panels and using the extra energy to power a > standard electric heater.
That would be an incredibly stupid approach. Much more money, much less heat (PVs toss 88-90% of the incoming energy).
Response:
>I have a 12′x24′ shed which I use to house my AE system. >The shed is also used as a workshop…
So you are a tinkerer 
>Last year I completely insulated the shed…
R20 insulation with a very good vapor barrier (say 30 cfm of air leakage) and 2 3′x4′ R2 windows might make a thermal conductance of 24ft^2/R2 = 12 Btu/h-F for the windows plus about 288/20 = 14.4 for the ceiling plus 27.6 for the walls plus about 30 for air leaks, a total of 84 Btu/h-F. NREL data indicate that January is the worst-case month for solar house heating in Boulder, with 1370 Btu/ft^2 of sun that falls on a south wall and 750 Btu/ft^2 on a horizontal (level surface on an average 29.7 F day. Your shed might need 24h(65F-29.7F)84Btu/h-F = 71.2K Btu of heat on that day, or less, if it’s only heated for a few hours a day. Battery charging and inverter losses might contribute some of that heat, or the heat loss from a small generator. >and would like to begin working on… a passive solar heating source… >I have 24′ of southern exposed roof on the shed with two angles to choose. >Its a gabel style of roof, one angle is about 60 deg and the other is 30…
I have a 12′x16′ shed with a gambrel roof like that. The lower part of the roof is 3′x16′, and the upper part is 4.7′x16′, with a 17 degree slope… I’ve been thinking about how to solar heat it for a couple of years >I am considering four 2×2 skylights on the 60 deg angle roof…
A square foot of skylight with 80% solar transmittance would collect about 0.8×1370 = 1096 Btu of sun on an average January day. With R2 (U0.5) thermal resistance, it would lose about 24h(65-29.7)1ft^2/R2 = 424 Btu, for a net gain of 672 Btu, so 16 ft^2 of skylights would gain 10.8K Btu/day, making the indoor temp 29.7+10.8K/24h/84Btu/h-F = 35 F on an average January day. >and installing ceramic tile flooring to absorb the heat during the winter >months.
Ceramic tiles are kind of thin, without much heat capacity, and storing the heat near the floor means it keeps the shed warm all day, whether you want that or not. Thermal mass above the ceiling might store more heat, with a higher temperature swing and upper temperature limit… >Someone else recommended installing a few more solar panels and using >the extra energy to power a standard electric heater.
Would that be Steven ("I am in love with photovoltaics") Strong? >There is no means of shading the skylights during the summer months.
You might devise one… >In order to prevent to much heat to build-up in the summer I installed >several ventilators.
With enough thermal mass and surface (battery electrolyte comes to mind) and airflow, you might open the vents at night and close them during the day. This might happen automatically, with some passive plastic film one-way dampers (dry cleaner bags hanging over chicken-wire-covered holes in the wall.) >For the skylights I am planning on installing an inner door which will >have a light difusing panel which I hope to block most of the heat and >still allow the light to pass.
Full sun is about 10K footcandles, vs 50 for a well-lit room. You might put 2 layers of 80% greenhouse shadecloth under the skylights, and vent the warm air above outdoors in summertime and indoors in wintertime. >Looking for any suggestions on heating and cooling the shed.
It looks like you need more solar heat, ie more solar glazing, about 100 square feet or more. And those skylights lose heat at night. And what do you do on a cloudy day? You might remove the shingles from the whole south roof and cover it with 2 layers of greenhouse poly film inflated with air during the day and tiny (1/16" or so) soap bubbles at night. Not passive, but low-power, and not too hard to arrange: put a 24′ x 2" PVC pipe full of holes in a trough formed from the the lower fold of the poly films and fill the trough with a 10% sodium laurel sulfate (detergent) solution, and maybe some sort of antifreeze. Inflate the films with air from a small blower above the water level during the day, as greenhouses do, or just leave the films collapsed together. At night, turn on a shop vac to make bubbles with about 1000X the soap solution volume. Put a return air path near the ridge with a 2" hole covered with insect screen. As the film cavity fills with bubbles from the bottom, air moves freely through the screen at the top. When the bubbles hit the screen, they deform it, and a microswitch turns off the shop vac. With a 1 hour bubble lifetime (Plateau kept bubbles alive for years in bell jars) the shop vac might turn on for 10 seconds a dozen times per night to replenish the foam. With a 4′x24′ south aperture and 80% solar transmission, you’d collect about 0.8×4′x24′x1370 = 105.2K Btu of south wall sun plus 0.8×6′x24′x750 = 86.4K of horizontal sun, a total of 191.6K Btu on an average day. If 71K of that goes to warming the lower part of the shed, the rest (120K) could keep the part under the roof warmer. If 120K = 6h(T-29.7)6′x24′/R1 + 18h(T-29.7)6′x24′/R20, T = 150 F, theoretically-speaking. Bubbles are better insulators at low temps (about R3 with 1/16" diameter and mean 50 F temp), and poly film is 80% transparent to longwave IR… To store heat, we might put some water above the rafters in a tray painted black, with a layer of clear flat polycarbonate above that, and allow room air to fill the space above the polycarbonate. We might use an angled 4′x24′ layer of foil-faced foamboard to divide the attic lengthwise into a solar south half and a storage north half. A person under the water tray would receive radiant heat. We might warm the room air with a slow ceiling fan. The shed needs about 350K Btu for 5 cloudy days in a row. That might come from 350K/(130-80) = 7K pounds of water cooling from 130 to 80 F in a 4′x20′x16" plywood box lined with a single piece of EPDM rubber, or a shallower box filled with a 50% 2:1 CaCl2/LiCl solution, as we distill water out on average days and add it back on cloudy days. Nick
Response:
– Hide quoted text — Show quoted text ->I have a 12′x24′ shed which I use to house my AE system. The shed is also >used as a workshop. Last year I completely insulated the shed and would >like to begin working on either a passive solar heating source or use the >AE to heat the shed. I would like to avoid using the AE. During the >summer I have more than enough energy to power the house, but during the >winter the system provides just enough. I have 24′ of southern exposed >roof on the shed with two angles to choose. Its a gabel style of roof, one >angle is about 60 deg and the other is 30 deg. I am considering four 2×2 >skylights on the 60 deg angle roof, and installing ceramic tile flooring to >absorb the heat during the winter months. Someone else recommended >installing a few more solar panels and using the extra energy to power a >standard electric heater. There is no means of shading the skylights >during the summer months. In order to prevent to much heat to build-up in >the summer I installed several ventilators. For the skylights I am >planning on installing an inner door which will have a light difusing panel >which I hope to block most of the heat and still allow the light to pass. >Looking for any suggestions on heating and cooling the shed. >Brian >Colorado
I would also suggest using a solar air heater. The design is very simple and the return is one of the highest in solar heater applainces. A simple 4×6 or 4×8 enclosure with insulated back and sides, a "filament" matrix absorber which is really polyester or fiberglass furnace filter media 1" thick with air blown through it. It needs to be black in color and "tilted" in the enclosure so air is brought in above it at one end, and passes through the media and out behind it at the other end . Mine are all cased in aluminum with polycarbonate glazing over the heaters. I put 4 panels on my south facing wall and have had no failures as of yet. I use (2) 495 cfm fans, 1 fan for each set of panels, and i use a motor speed control to set them exactly where i like them. I also used 110f snap discs to start the fans automatically when they reach proper temps. Summer stagnation is not a problem since the suns declination changes so much that by summer time, they are almost shaded all day. I chose wall mounting for that reason. I couldn’t stand the thought of frying my panels all summer. Please email me if you want details as to how i made the panels and with what materials. I would be happy to donate my limited knowledge. M Russon
Response:
Hello all, Please let me know if you have any questions about any of the following information. You can email me for an illustration of the collector construction. Bill Kreamer, President Sol-Air Company 129 Miller St. Belfast, ME 04915 tel 207-338-9513 fax 603-853-9339 —-
– Hide quoted text — Show quoted text ->I have a 12′x24′ shed which I use to house my AE system. The shed is also >used as a workshop. Last year I completely insulated the shed and would >like to begin working on either a passive solar heating source or use the >AE to heat the shed. I would like to avoid using the AE. During the >summer I have more than enough energy to power the house, but during the >winter the system provides just enough. I have 24′ of southern exposed >roof on the shed with two angles to choose. Its a gabel style of roof, one >angle is about 60 deg and the other is 30 deg. I am considering four 2×2 >skylights on the 60 deg angle roof, and installing ceramic tile flooring to >absorb the heat during the winter months. Someone else recommended >installing a few more solar panels and using the extra energy to power a >standard electric heater. There is no means of shading the skylights >during the summer months. In order to prevent to much heat to build-up in >the summer I installed several ventilators. For the skylights I am >planning on installing an inner door which will have a light difusing panel >which I hope to block most of the heat and still allow the light to pass. >Looking for any suggestions on heating and cooling the shed. >Brian >Colorado > I would also suggest using a solar air heater. The design is very > simple and the return is one of the highest in solar heater > applainces. A simple 4×6 or 4×8 enclosure with insulated back and > sides, a "filament" matrix absorber which is really polyester or > fiberglass furnace filter media 1" thick with air blown through it. It > needs to be black in color and "tilted" in the enclosure so air is > brought in above it at one end, and passes through the media and out > behind it at the other end . Mine are all cased in aluminum with > polycarbonate glazing over the heaters. I put 4 panels on my south > facing wall and have had no failures as of yet. I use (2) 495 cfm > fans, 1 fan for each set of panels, and i use a motor speed control to > set them exactly where i like them. I also used 110f snap discs to > start the fans automatically when they reach proper temps. Summer > stagnation is not a problem since the suns declination changes so much > that by summer time, they are almost shaded all day. I chose wall > mounting for that reason. I couldn’t stand the thought of frying my > panels all summer. Please email me if you want details as to how i > made the panels and with what materials. I would be happy to donate my > limited knowledge. > M Russon
ADVANCED HOMEBUILT AIR-BASED SOLAR COLLECTOR INSTRUCTIONS OVERVIEW INTRODUCTION These instructions are for a homebuilt version of Sol-Air Company’s air-based SHVC system (Solar Heating / Ventilation Cooling; please see the description at the end). An accompanying illustration is available from homebuilt unit in its patented internal air-handler, automatic four-season mode-switching, and proprietary high-surface-area filament-matrix absorber. Homebuilt Solar Collector Output Like its commercial cousin, this homebuilt unit produces more energy for the money by far than other forms of solar utilization, including PV and solar DHW systems. The output for a 20 square foot unit is approximately 5,000,000 Btu per year, equal to approx. 50 gallons of heating oil (or 50 Therms of natural gas). This output is produced primarily in the spring and fall, with a decided dead spot in the middle of a cold winter. Mounting The collector is mounted vertically on the outside wall (the rule that tilt = latitude is for another type
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