Space and water heating and cooling consume 48% of all energy used in an average U.S. residence, and usually that energy is supplied by natural gas or fossil-fuel derived electricity. Geothermal heat pumps can reduce energy requirements for heating and cooling by up to 75%. However, traditional geothermal heat pumps are expensive and their performance is difficult to predict before installation.
Sustainable energy production is a major challenge facing our society. Solar energy is renewable and is a viable and attractive option. However, there are obstacles to widespread use. Current technology is expensive, making it difficult for businesses and homeowners to implement, and solar cells are commonly made using toxic and rare elements or using processes that require large amounts of energy. To become commonplace, solar cells must be inexpensive and robust, and they must be made of abundant, cheap, nontoxic materials.