Part of http://www.sunoven.com/ website shows larger ones attached to a trailers. I think it would be easy to make your oven with cheaper or free parts. I want to do some more research to make a easy design that can reach very high temp. fast and easy. One that could possible make electricity when not cooking food or a thermal electric generator attached to it. More to come Later.
This current design costs 300$.
Why is the GLOBAL SUN OVEN® the world's most widely used solar oven?
People have used the sun to cook for centuries, yet solar cooking has never gained widespread acceptance. Sun Ovens International has taken a concept that has been around for generations, combined it with the most effective materials available, a design with features that take the hassles out of solar cooking, to create the Ultimate Solar Appliance.Innovative Features
One piece collapsible reflectors
The GLOBAL SUN OVEN® can be set up for use or taken down for storage in a matter of seconds. The reflectors literally fall into place at an angle that allows you to maximize the power of the sun.The reflectors are made of highly polished, mirror-like anodized aluminum that can be cleaned quickly and easily with glass cleaner, and they will never oxidize or rust.