Not an engine, but some friends of mine got a mylar sheet that's black on one side and reflective on the other. We tried it out in the desert tied onto trees/vehicles. You put the shiny side down, so the hot IR radiation of the earth is reflected away, and the black side sees the extremely cold (in IR) desert sky. If you put a little hole in the middle and put a bucket under it, you get a fair bit of water, because the mylar sheet gets about 20 degrees C below ambient and a lot of water condenses on it. (even in the desert)
I was going to look into this once, but instead I opted to go into Tosche station to pick up some power converters and unfortunately never quite got around to it.
I didn't do the measurment and it's been a while so it's possible I misremembered the temperature delta, or maybe it was degrees F. It was about a 2-3 square meter sheet and it made about a liter of water overnight.
