Flat-plate collectors are as simple as they come and they capture the energy from the sun. There are different designs, but for the most part they use heat transfer fluid. Once cold water has been collected in the storage tank, the flat-plate collector starts looping the fluid through the cold water and heats it up

Evacuated tube collector (ETC) consists of single tubes that are connected to a header pipe. To reduce heat losses of the water-bearing pipes to the ambient air, each single tube is evacuated.

Traffic lights, traffic signals, stoplights or robots are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic. The world's first traffic light was a manually operated gas-lit signal installed in London in December 1868.