Other Solar Technologies

Solar Space Heating

In a solar heating system, energy from the sun is captured to heat up air or water to provide space heating. Solar space heating systems can be classified into either active or passive types.

Active Solar Space Heating

Active solar space heating systems consist of solar collectors and auxiliary pumps, to absorb solar radiation for heat up air or water and to distribute the heat. Energy storage facilities may be included into the systems to store up the heat so as to continue supplying heat in the hours of the day when there is no sunlight.

Active solar heating systems can be divided into two major groups based on the type of fluid used in the solar collectors:

1. Liquid-based systems use water or an antifreeze solution as the heat-transfer medium in the solar collectors. Liquid systems are more often used when energy storage facilities are included.
2. Air-based systems use air as the heat-transfer medium in the solar collectors.

Passive Solar Space Heating

Passive solar space heating use the heat from the sunlight directly through design features. These including the application of south-facing windows to introduce more sunlight to the interior space, and the application of building materials that increase heat absorption to the interior space but reduce heat loss to the environment.

Heat from the sun can be introduced to the interior space passively mainly by one of three designs: direct gain, indirect gain and isolated gain.

• Direct gain design - the building materials (such as tiles and concrete) store and slowly release the heat energy collected from the solar radiation shining into the building.
• Indirect gain design - uses materials that hold, store, and release heat; the material is located between the sun and living space (typically the wall).
• Isolated gain design - collects solar energy remote from the location of the primary living area. For example, a sunroom attached to a house collects warmer air that flows naturally to the rest of the house.

An example of a passive solar space heating system is the This link will open in a new windowThis web page has hyperlinks which may transfer you to third-party website.SolarWall system (The system is described here as an illustration of a passive solar space heating, even though it has not been installed in Hong Kong.) The SolarWall system is a metal-wall system that uses solar energy to heat and ventilate indoor spaces. It consists of perforated collector panels, ventilation fans and is connected to a HVAC intake. The collector panels are installed several inches from a south facing wall, creating an air cavity. The metal cladding is heated by the solar radiation from the sun, and ventilation fans located at the top of the wall create negative pressure in the air cavity, drawing in the solar heated air through the panel perforations. A connection to an HVAC intake allows air to be preheated before entering the air handler, reducing the load on the conventional heater. This heated fresh air is then distributed into the building through the existing HVAC system or with separate air makeup fans and perforated ducting.