Last updated: 14 January 2015
In-the-ground solar cooker designs substitute digging a hole in the ground to replace the box container of a typical solar box cooker, or to provide support for the reflectors of a solar panel cooker. This simplifies construction, but the approach has some limitations. If trying to replicate a box cooker, some form of insulation will be required to line the sides and bottom of the hole.
California researcher Said Shakerin researched an early design that used only a black insulating mat at the bottom of the hole with a glazing cover and reflector on top. Said has written up his findings here: Earthen Solar Cooker
John Barker has done considerable research with the Solar Nest. He has experimented using netted bags of coconut husks to mimic digging into insulating ground cover. Others, such as Kristen Rahn, have used newspaper for insulating the cooking chamber. Unless a design dug into the ground uses a circular or oversized glazing cover, it is not possible to reorient the reflector while cooking.The Solar puddle is a water pasteurization technique based upon the research of Dale Andreatta for large amounts of water. It is essentially a puddle of water in a greenhouse being heated to at least 70 °C (158 °F)
Most of the in-the-ground designs have used the box cooker approach. However, a panel cooker may have possibilities. Staff at Solar Cookers International have considered lining a hole with a mylar reflective 'space' blanket. The material dug from the hole could be built up to create a circular reflector around the hole. Then, typical of a panel cooker, a black pot in a plastic bag on a slightly raised platform, is placed at the center. While it would not be possible to redirect the reflectors, it is conceivable that two holes might be dug side by side, with one cooker directed to morning sun and the other at afternoon sun. This approach would be particularly useful for locations near the equator. More research should be done with space blankets used as reflectors. They are available commercially for approximately $5 USD.
Soil consistency will also be a factor, as soil too sandy may not support the reflector blanket. Soil type is also a factor for the box style cooker, as unless the walls are supported, the soil may cave-in on the sides.
- August 2012: Pete Schwartz discusses fixed reflectors in his paper, Concentrating sunlight with an immobile primary mirror and immobile receiver: Ray-tracing results
Hole in the ground using an emergency blanket
Paul van den Hurk dug a round hole in the ground about 30 inches diameter and about 1 foot deep. He made the sides about 60° and covered them and the bottom with old newspapers. Then he covered the newspapers with some old aluminum foil. He placed a black-painted cooking pot with rice inside and covered it all with a piece of glass. It took about 2 hours to cook the rice. See images below:
Dig a hole.
Cover with newspaper.
Cover with foil.
Cover with a glass.