Actually, solar ovens will work under just about any lighting conditions in open country, the issue being simply a matter of scale. How big of a collector can you make? Did you know you can cook a turkey by the light of a full moon?

As with all such physical phenomena, success depends on the prudence of the application. Sometimes it's a solar cooker, sometimes it is seal blubber.

I'm still holding out for that portable geo-thermal steam oven...hey, it's just a matter of how deep a hole you can dig.