Euell Gibbons describes methods for drying herbs and ohter foods in his books on gathering wild foods. Unfortuantely I can't point you to exact page references -- but reading the series is great fun.

The website at this URL has plans for a solar powered dehydrator. One of the pictures is below.

http://permapak.net/solarfooddryers.htm

I've run across plans, or ideas, for food drying in many books on camping. Hit the library and browse through the shelves.

Basics are a box to keep out dirt, and a screen to put the food on. If you can get some clean fiberglass-reinforced window screening and the aluminum stock and corner locks used for making window screens (generally available at hardware stores and home centers) you can make screens in almost any size. Make a box from 3/4 inch plywood and cut grooves (dadoes) in it to hold your screens several inches apart If you aren't into cutting dadoes, use strips of wood nailed onto the plywood sides to hold your screens. Put a heat source inside if you like, and use a small vent fan, like that used on a computer, to suck the moist air out of the box. If you get a recycled computer fan you'll probably need a 12 volt transformer.

hope this helps

PGJ