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What Is a Passive Solar System?

Mal Baxter
Mal Baxter

A passive solar system is a collection of various building elements designed for the collection and conversion of solar energy in order to power a building's energy needs. Such a system includes specially designed windows, walls, and floors, all working together. Depending on the environmental climate and the building's orientation during peak periods of sunlight, these elements work together in various ways to absorb and distribute solar energy. This might enhance climate control or limit the effect of environmental extremes. A passive solar system may also consist of thermal insulation, mass and shading properties of materials, treatments, and technologies.

Passive solar designs rely on architectural cooperation with nature instead of energy-hungry appliances. In order to efficiently manage solar energy in a house or commercial building, a passive solar system may be designed around one of six design configurations. These include direct, indirect, and isolated solar gains. Heat storage and thermal insulation both extend a property's energy capabilities. Passive cooling techniques round out the designs.

Man holding computer
Man holding computer

Direct solar gain may combine window and floor absorption properties to capture heat, or thermal energy to warm a space directly. Indirect solar gain may conduct that heat through a water tank or masonry wall. Isolated solar gain transmits thermal energy captured in a special site, like a sun space or solarium, and transfers it into main areas via ducts.

Using the heat storage technique, thermal energy can be captured by a specially designed floor, a water wall, or a roof pond. These may be designed to emit heat over periods when the sun may be absent. Thermal insulation and window glazing techniques help enhance or prohibit direct gain energy.

Passive cooling occurs with the use of reflective windows and ventilation, such as with a solar chimney. This is a structure that uses convection to create an updraft to remove warmer air and pull cool air into a room from the ground via heat-exchange tubes. It is sometimes called a thermal chimney. On a larger scale, it may be designed as a passive downdraft cool tower.

Essentially, a passive solar system is designed to heat or cool a building. It does this by using more efficient management of solar energy and relying on thermal properties of building materials. Photovoltaic (PV) films assist in converting solar power into electricity. Applied to panes of glass, these photovoltaic properties can also convert sunlight into storable electric or thermal energy.

Numerous types of windows are glazed or treated not only for thermal properties but also to protect interiors from harmful ultraviolet (UV) radiation. Additionally, a passive solar system might work with technology enhancements like automated blinds or drapes that activate during peak periods of sun. This type of operation can help preserve cooling by shading an interior from the hot midday sun.

Throughout the year, a building can undergo a wide range of light and temperature variations. Days and nights give way to seasons. Instead of working against these trends, a passive solar system attempts to work within them. It helps moderate energy use by working smarter and not harder.

A passive solar system can accommodate these changes on a daily or seasonal level. As such, it may be integrated into the building design itself. Elements such as window direction, room space, shading, and floor plans work together with materials and technologies to create an overall energy-efficient structure. This can create a more reliable environment for an energy-smart living and working space — and a better working relationship with Mother Nature.

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