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Solar Thermal Heating, Cooling and Ventilation System For Shipping Containers

A guiding principle for us is that the technologies and processes we create should allow for the production of food year-round. With indoor production facilities, such as our re-purposed shipping containers, keeping the indoor temperature at a level ideal for plant growth can be a challenge, especially in winter months.

In central Ohio, where the hapi project was created, we have 4 distinct seasons. Our winters last from December through February, during which outside air temperatures average around 20°F with a record low of -28°F. Sub-zero colds snaps are not uncommon. Some season extension techniques, such as hoop houses and cold frames, can allow for growing cold-weather crops late into the winter. Similarly these technologies can effectively move spring a few weeks sooner. However, a cold snap can quickly stunt winter growing activities for all except heated greenhouses.

A key goal for all of our products is to evolve urban agriculture technologies along multiple, separate but interrelated axis'. First and foremost of these is energy. While it is certainly feasible to burn fossil fuels to heat a grow container, it goes against our commitment to make food production carbon neutral. Solar thermal is not a new technology. It is often employed to heat water (solar water heaters) and, less commonly/commercially, air. In either case, the units function as follows (example is with air).

A heat absorber is placed in a box with a transparent top/face. The box has an inlet at its lower end and an outlet at its upper end. When sunlight strikes the absorber, the air that is in contact with it warms. This warm air rises and exits through the outlet. This upward air movement creates a convection current. Cooler air moves into the unit from the inlet. This air is in turn warmed and the process continues while sunlight remains.

Our needs and constraints are a bit different from most of what we found online. We needed to mount the unit on the end of a corrugated box made of thick steel, with insulation on the inside. The unit is mounted completely vertical and must help us exceed our daily operational needs during the winter, in order to make up for the short days of January.

To learn more about this and other projects, visit us at hapihq.com.

Step 1: The Box Frame

We started with a sheet of 11/32" plywood, standard size 4' x 8'. Then we made a box frame out of three 1" x 6" x 8' planks. The outer edges of the box frame fits exactly to the outer edges of the plywood. We set the plywood on the frame, aligned the edges and screwed it to the frame with 1 1/4” wood screws. The total cost for this step was about $38.

I could be wrong but I believe the uv resistant material might affect your efficiency by blocking the uv light.
Agreed
<p>Ultraviolet resistant materials are treated to resist degradation by UV light; UV resistance does not interfere with the passage of the infrared portion of the spectrum responsible for the transmission of heat energy. </p>
<p>uv is not delivering heat. infrared is. so there is no problem.</p>
<p>That's good news. Thanks for your input!</p>
<p>Just a note on rabbit manure. It is a fertilizer, however it should be used cautiously. It is very high in nitrogen and phosphorous. Over application will cause more harm than good. When added to composter, placed in your grow area, you will get the benefits of the nutrients, as well as the heat generated by the composting action.</p><p> the com</p>
<p>I remember reading somewhere that traditionally in Europe, lop-eared rabbits were used in greenhouses to help keep them warm in winter. The large ears would radiate heat, the large bodies weren't capable to jump up to the grow beds and made for a source of meat, the poo was a good fertilizer, and they cleaned up weeds growing on the floor. This may all be conjecture by someone who wrote it on the internet somewhere, so take it with a grain of salt.</p><p>This is a neat idea that is easily repeatable with common materials. Well done.</p>
<p>I'm convinced. Gotta go find me some lop-eared rabbits!</p>
This is really cool, I just want to know how warm does it get?
<p>Great question! It's completely dependent upon available sunlight. Two days ago was clear and sunny but the outside air temp was about 12F here in central Ohio. The temperature inside the hot air duct was 128F. We use a small fan to help push air through the system when it's sunny. The air coming out of the unit, about 8&quot; from the hot air duct was just over 90F.</p><p>On a 100% overcast day we get essentially no temperature lift from the unit.</p>
this is my Instructable. <br><br>https://www.instructables.com/id/Beer-Can-Solar-Space-Heater
congratulations on a really nice ible. I built something similar using beer cans as the absorber/chimneys. for fans I used 4&quot; pc case fans connected to a 15W solar panel. this resulted in a self regulating system, i.e. the sunnier a day was the more power the solar panel produced, this ran the fans faster and as a result pushed more air through reducing the time the air had to heat.

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