pt. I: Solar energy. A brief history of solar power -- Sunlight and geometry -- Photovoltaics -- Heat engines and solar power -- Two other important solar technologies -- Economic and environmental consequences of solar power -- Government policies and solar energy -- pt. II: Geothermal energy. A brief history of geothermal energy -- Geology and heat -- The generating station -- Two other geothermal technologies -- The economics and environmental impacts of electricity from geothermal sources -- Government policies and geothermal energy -- Chronology -- List of acronyms -- Glossary.