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Solar heating ideas to utilize the excess heat that builds up in shipping containers  RSS feed

 
Dale Hodgins
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Problems of overheating with dark colored shipping containers has given me some ideas concerning solar water heating.

 The roof and south-facing walls seem like the perfect spot to place flattish collectors. Not only would this supply hot water, it would tend to reduce the interior temperature.

I have used the big bucket of an excavator as a solar collector. My shower bag was laid in a slot, near where the bucket connects to the arm of the machine. Metal is great at conducting heat. The entire bucket got quite hot in the midday sun. Much of this heat was conducted to the area being cooled by my shower bag. This resulted in very fast heat up , since the bucket had a large collection area. The same would be true for collectors laying on the roof of a container. The hot metal from all around will conduct heat toward the coolest spot.

I have laid my shower bag on several other hot surfaces, including asphalt , metal roofing and the hood of a car. In all cases, heat was transferred from the base material toward my collector. Metal surfaces  work better than others, because metal is great at conducting heat.

The water must be emptied to storage or used before it gets a chance to cool down in the evening, when the container cools down. The same metal that was quite hot during the day, will work like a radiator and quickly release stored heat to the sky.

Imagine using a dark shipping container as the north wall of a pool enclosure. Flat plate collectors could sit against the roof and South wall. If only a quarter of the area were covered , those collectors would gather more heat than a similar array of collectors attached to a specially made base.

Containers are very strong, but that strength is not evenly distributed. They are meant to take huge amount of weight at certain points along the walls. The roof is meant to withstand a heavy snow load. If very heavy containers of water are to be placed on the roof, they must be placed in the right locations.
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When looking for used containers , I found that lighter colors were harder to come by. Upon questioning the sales people, it turns out that most people are looking for something that won't get too hot. This means that there is more competition for good quality , light colored containers.

A dark container could be used for solar water  heating for about eight months of the year in my climate. During the winter, the darker container would still warm up sometimes on sunny days. This would be the perfect time to ventilate, in order to reduce condensation.
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A container could also be used as a means of producing plenty of hot air. This could be useful for space heating of adjacent buildings.

For those looking to kiln dry lumber, it could be as simple as loading it all into a container and controlling the ventilation, so as not to dry the wood too fast.

 A dark container would be the perfect place to keep firewood. Fast drying is not a problem, in fact it leads to greater cracking which in turn leads to even faster drying. Even in the dead of winter, we get some days when the sun would dry out the wood a little.

Probably the simplest way to control condensation, would be to store some firewood along with other items to be stored in a container. Firewood will lose moisture during hot days and it will rapidly absorb moisture from the air, if it gets anywhere near the dew point. The average humidity can be kept quite low, by ventilating, on hot days when the firewood is giving off moisture to the air.

If we desire more heat than the container supplies, it can become a more efficient collector if the wall facing away from the sun, is insulated.

Does anyone else have thoughts on how to utilize heat that is gathered by shipping containers?
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Dillon Nichols
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Interesting; I've long intended to use cans for similar purposes, but I'm thinking white to reflect rather than black to absorb.

My interest is mostly in growing things against the southish facing side of a container, and I think the reflected light will be more useful than absorbed heat due to the (relatively, compared to say a stone wall, or terrace with soil behind it) low mass of the container; no matter how hot you get that few thousand pounds of steel, it's going to be damned cold long before morning.


The possibilities get even more interesting if you have a pond or reservoir to play with... Solar heating devices benefiting from both the reflection of a pond and absorbtion/reflection of a container ought to be extremely effective. Plus a lighter container could also reflect light onto the pond, further increasing the temperature of that thermal mass...

(Also, how is absorbtion not a word? Bullshit.)


If one is using multiple containers, maybe the southernmost could be white, and the others dark, so that you still have some dark rooftop space and end-wall space, but less extreme heat-cycles inside the containers... Or, if you are planning to roof over the container/s, a bit of end or side wall could be left with less overhang to maximize sun exposure for this.



Containers are very strong, but that strength is not evenly distributed. They are meant to take huge amount of weight at certain points along the walls. The roof is meant to withstand a heavy snow load. If very heavy containers of water are to be placed on the roof, they must be placed in the right locations.


Very important to keep this in mind! However, I'd expect support of a modest reservoir at the right spot to be pretty straightforward; a hundred gallons of highly insulated water storage on top of the container could be heated via thermosiphon by collectors along the side/end of the can; valving to close off flow at night would allow preservation of the heat collected.
 
Dale Hodgins
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I'm looking at getting at least two containers , since they arrive one inside the other. I will probably seek one dark and one light.

Shallow ponds made from rubber pond liner with a wooden frame are something that could be put together easily. Make them the size of a standard patio door glass. Fill in the morning. Empty at night. They would have to be kept  full or covered up on hot days, in order to prevent overheating damage to the rubber liner. It's good to 300 degrees Fahrenheit.

For the side of a container, a water trickle system could be used. These allow a constant flow of water to run over the hot metal. This would work nicely for a swimming area that is immediately beneath the container. A small solar panel , connected to a pump , would move more water when the sun shines brighter. This coincides with periods of maximum heat on the container wall. No need to store the electricity and no need to have any sort of thermostatic control of when the pump works.

I've come up with a fairly short list of items that don't mind being hot during storage.

1. Firewood

2. Lumber that is being kiln-dried.

3. Almost anything metal that does not contain oil or rubber parts.

When solar water heating is not happening, it will be important to ventilate.
 
Rebecca Norman
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I don't know if this would be related, but we have used this.
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William Bronson
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Normally used with greenhouses subterranean heating and cooling systems (shcs)
offer a relatively lowtech way to store heat and "cooleth". There are no pumps, rather it uses fans, and it takes advantage of the thermal storage density of water by inducing phase change(condensation).
 
Rebecca Norman
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Location: Ladakh, Indian Himalayas at 10,500 feet, zone 5
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food preservation greening the desert solar trees
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Yes, the wood shavings are insulation under the bed of the simple solar water heater.
 
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