When there isn't sun there is often wind, so it makes sense to use them both. Here is another version of a combined solar/wind powered streetlight, perhaps not as elegant as Justin's Canadian vertical axis unit
, this Chinese fixture has a 400 watt turbine, 200 watts of solar, batteries and controls with a six day reserve, powering a 200 bulb 30 watt LED array.
"intended for permanent installations and can be located in the remotest of sites since no mains services are required saving on installation costs, inconvenience and time. The whole system is virtually maintenance free and there are NO daily running costs- the power is completely free and clean." ::Duxlite
Here is a whole street of them.