Designs of cooling systems that operate entirely on solar energy are disclosed. Such cooling systems may be used in refrigeration and air conditioning. According to one aspect of the designs, a solar energy collecting device is disposed outdoor to collect solar energy. A first heat-to-electricity pump operating on heated liquid is provided to produce electricity. A storage tank is used to store heated water. A second heat-to-electricity pump is disposed in the storage and operates on the heated water to generate electricity. A cooling system operates on at least three types of working fluids to achieve low temperature evaporation and high temperature condensation to derive cooling effects. A working unit powered by at least one of the first generator and the second generator is provided to utilize the cooling effects from the cooling system.