What are some permie gadgets you wished you had heard about sooner?

I am building a solar dehydrator and solar oven this spring and I am really amazed at how simple and perfect some solutions can be. What gadgets or ideas do you think I should not miss out on?

While I don't have these gadgets and can't make them, they could easily be on my wish list:

Haybox Cooker

Walker Cook Stove

Rocket Mass Heater

Solar can heater

I've been saving soda cans and planning to build a couple solar can heaters over the next couple of weeks.  Pretty straightforward and inexpensive to build.

Nicolas Keeton wrote:Solar can heater

I've been saving soda cans and planning to build a couple solar can heaters over the next couple of weeks.  Pretty straightforward and inexpensive to build.

I've seen this before as part of a dehydrator.. but now that you remind me, I DO have a bathroom with no heating that gets mouldy in the winter. Would this work in the winter to heat a room of maybe 2-3 square metres if put up on a south facing roof?

Oh, I should add, I live in Germany, so in the winter we get up to minus 10 in January/February and veery seldomly -20. But the sun is shining when it freezes!

A Rocket Stove Oven

Tomke Roolfs wrote:

Nicolas Keeton wrote:Solar can heater

I've been saving soda cans and planning to build a couple solar can heaters over the next couple of weeks.  Pretty straightforward and inexpensive to build.

I've seen this before as part of a dehydrator.. but now that you remind me, I DO have a bathroom with no heating that gets mouldy in the winter. Would this work in the winter to heat a room of maybe 2-3 square metres if put up on a south facing roof?

Oh, I should add, I live in Germany, so in the winter we get up to minus 10 in January/February and veery seldomly -20. But the sun is shining when it freezes!

Multiple factors plays in the the heating and heat retention of the room, such as  insulation, windows in room, window placement and wind draft. From the videos, that I've seen online I believe that a room that is 2-3 sq meters would not be an a problem, since there's proven video that smaller scale heaters are outputting 50C+ (120F+) heat while the intake air is -8C (20F) with snow on the ground.

Both video links below have similar environment to that in Germany.

This guy is claiming that his is outputting 126C (260F) heat from -10C (14F)
https://www.youtube.com/watch?v=PQjogCyvwgk

This one is a smaller scale that is -8C (20F) to 37C (100F):
https://www.youtube.com/watch?v=CXy-B-ip5-s