There are solar fridges, if you've got a grand or two to spare, but they've not caught on here due to the weather, plus you have to leave them outside, so your beer, bacon and steak gets stolen. And long nights are a problem.
One of our team does actually have a solar powered fridge, using a compressor (expensive/efficient) camping fridge, a car battery and about 100 watts of solar panels, the idea being that during the day, the sun runs the fridge and charges the battery, which then runs the fridge all night (there's only about 5 hours of dark at Le Mans). If its a bit of a dull day, then the generator goes on. I'll stick to gas.