The 21st Resolutions of the recent United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties (COP) outlined, promotion of sustainable energy, sustainable management of natural resources, and maintaining environmental integrity through mitigation of greenhouse gas emissions; towards sustainable development. Renewable energy is sustainable and natural resource is the source of clean energy. Solar energy is the most abundant and inexhaustible renewable energy resource; the sun’s daily irradiation to the earth reaches approximately 10,000 times more energy than the average daily energy consumption of Earth. However, harnessing the sun’s energy efficiently at a reasonable cost comes as a challenge. Building-integrated, building-attached and standalone active systems that convert solar energy into useable forms of heat and electricity as well as wind power and geothermal systems are reliant on solar energy as identified and discussed in this chapter. General planning and methods of integration of various active systems are described in this section.