We take it for granted that we have a fridge in the kitchen that keeps food fresh. The fridges that we use need to be plugged in to the electricity supply before they start working. But in some countries, there isn’t an electricity supply. A lot of these countries are also very hot, so having somewhere cool to keep food is very important.
These countries don’t have a lot available to them, but they do have a lot of sun (or they wouldn’t be as hot and need as much cooling to keep food fresh). So if we can find something that uses the sun’s energy to make something cold, then the people in these countries will be able to store food for longer. (These people also usually rely on farming crops for their food, and in the heat the harvested crops go off very quickly).
So although it doesn’t really make sense using something hot to keep something else cold, it can be very useful.
In countries where there is already a good electricity supply, using the sun to keep things cold reduces the amount of electricity used which makes it cheaper and stops pollution.