matt sexton

Al warned me in a pm, that I was not clear about something:

The sheet metal lens I spoke of is a light-goes-through lens. Concentric rings of metal are tilted so as to deflect the light towards a focus that is down-light from the lens. This is not a parabolic mirror.

Hi Al, thanks for the thoughts. Yes, heat rises, so it does seem like a good idea to shine the light in at the bottom. That puts the concentrator and/or mirrors next to the oven instead of above it. Which I might well do.

Have you made one of those 'high temperature' ovens? How hot do they get inside? How do you form the perlite insulation layer, is it a wet mix that dries into shape, or is it something you carve into shape?

My direction is completely away from burning any wood.

I'm working on this 'solar horno' idea, would love constructive feedback. Discussion is helpful, hopefully adds momentum and direction.

I live in Albuquerque, plenty of sun here. As Steve Baer says, "so much sun here you can do your passive solar project poorly and it will still work"

In the south west, we have these things called "horno"s, it's a 5' tall thermal mass with a chamber inside. In the morning you build a fire inside, around noon you scrape out the coals and put in the bread dough. This is the traditional bread baking method. It takes a lot of wood!

Solar Horno:

A thermal mass surrounded by insulation. With a shut-able hole in the top, and a tracking solar concentrator above the hole funnels photons down into the hole. Every day about 15 mega-joules heats up the mass inside, raising the mass temperature to 2000F, hence plenty of energy storage. Simple convective channels trickle the heat to a cooking chamber as needed.

I did the fun (for me) part, I figured out how to cut a piece of sheet metal up so as to form an arbitrarily large Fresnel lens for concentration. Haven't built one yet, that's the next step, but I'm bound and determined to build one an see how it works.

The parts I'm not sure about yet: passive tracking, kiln-like materials for solar mass and cooking chamber.

I want a solar cooking spot in the yard, be able to cook marshmallows, heat up a big pot of water for pasta, slow-cook meat, all by grace of the long-set sun.

Thoughts?