It eliminates dependence on external energy and generates minimum waste. It is also hidden from view as it is placed underground, making it more aesthetically pleasing and easier to incorporate in a design. Wind turbines are a useful application for areas without immediate conventional power sources, e.g., rural areas with schools and hospitals that need more power. Wind turbines can provide up to 30% of the energy consumed by a household but they are subject to regulations and technical specifications, such as the maximum distance at which the facility is located from the place of consumption and the power required and permitted for each property. Water recycling systems such as rainwater tanks that harvest water for multiple purposes. Reusing grey water generated by households are a useful way of not wasting drinking water. Hydropower, also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. Hydropower is an attractive alternative to fossil fuels as it does not directly produce carbon dioxide or other atmospheric pollutants and it provides a relatively consistent source of power. Passive systems Buildings that integrate passive energy systems (bioclimatic buildings) are heated using non-mechanical methods, thereby optimizing natural resources. Passive daylighting involves the positioning and location of a building to allow for and make use of sunlight throughout the whole year. By using the sun's rays, thermal mass is stored in the building materials such as concrete and can generate enough heat for a room. Green roofs are roofs that are partially or completely covered with plants or other vegetation. Green roofs are passive systems in that they create insulation that helps regulate the building's temperature. They also retain water, providing a water recycling system, and can provide soundproofing. History 1971 Ian McHarg, in his book "Design with Nature", popularized a system of analyzing the layers of a site in order to compile a complete understanding of the qualitative attributes of a place. McHarg gave every qualitative aspect of the site a layer, such as the history, hydrology, topography, vegetation, etc. This system became the foundation of today's Geographic Information Systems (GIS), a ubiquitous tool used in the practice of ecological landscape design. 1978 Permaculture. Bill Mollison and David Holmgren coin the phrase for a system of designing regenerative human ecosystems. (Founded in the work of Fukuoka, Yeoman, Smith, etc.. 1994 David Orr, in his book "Earth