The technique is thousands of years old. The Australian version is the Coolgardie safe:
It’s a wire mesh cage with damp cloth on its outside. As long as you keep the cloth damp, and the air is not 100% humid, the contents keep as cool as in an electric fridge.
Other versions use the same principle with unglazed clay pots, kept damp. Ilana Strauss describes a version that will work for a considerable time without needing attention: a large pot holds a smaller pot, with sand in between. You wet the sand, and fill the inner pot with food.
Given that 15% of electricity use is for refrigeration in the typical home, this is a good trick to keep in mind. And when the grid fails, it still keeps working.