Mini Solar Greenhouse Sketch

Here is a sketch of a mini-greenhouse. It is not exactly to scale, it’s more of an idea of how one would work (Click for full size):

How it works…

Uses water filled, black painted milk jugs for thermal mass for nights and cloudy days. The milk jugs either need to be the non-biodegradable kind or will have to be changed out regularly.

The jugs and soil receive direct gain from the triple glazed window (hopefully salvaged.) If the greenhouse gets too warm it could be vented via a 12 vdc solar/battery powered mini fan (think computer cooling fan–another easy salvage) hooked to a thermal switch (salvaged home mercury thermostat.)

For nights and cloudy days a thermal shutter could be employed. The shutter could have a lower reflective surface and be able to be tilted to reflect the most sunlight into the space.

Some problems…

Air infiltration/heat loss around the shutter when closed would be a problem.

Ideally, the number of milk jugs should be 2 per sq ft of south facing glass in colder climates. Ideally the milk jugs should get direct sunlight. A 3′ x 4′ window area would mean 24 milk jugs. In a 5′ wide interior space you are looking at having a rear wall of water jugs 4-5 high. That might be a bit cumbersome.

I looked into other types of storage (water bed mattress for instance), but to get enough solar gain on sunny days there wasn’t a good way to expose enough of the surface to direct sunlight.

I think a design where you have a 3′ x 4′ glass coupled with 8-12 milk jugs should provide good heat retention for most days.

If I were building this I would probably want the growing area to be a slide out tray rather than making the window operable. That way you can seal the window well and prevent heat loss and create a tight seal on the side wall where the planting area pulls out.

This is not one of my best designs, and if one didn’t use salvaged materials the cost would be prohibitive for the minimal return.

An idea I did have while designing this would be a tiny greenhouse built from a scrapped refrigerator.

Tags: Eco-Friendly Apartment, Greenhouse, Greenhouse Plan, Passive Solar, Passive Solar Apartment, Passive Solar Greenhouse, Solar Greenhouse