Solar Heating and Cooling
The most common form of solar thermal technology is the Solar Hot Water Collector.
Why Solar Heating and Cooling Matters to Local Governments
Solar hot water collectors are ideal for urban applications because they can easily utilize the empty space of urban rooftops, requiring no additional land. Hot water collectors are effective most places on the earth, although there are seasonal differences in output. This type of technology can be applied to singular buildings or incorporated into a district solar heating scheme, which gives local governments quite a lot of flexibility.
- Rooftop solar hot water heating systems in Betim, Brazil.
The Technology
Solar collectors focus the heat of the sun to heat water that can be used for space heating and/or hot water uses. These can be either direct or indirect systems. In a direct system the water that is heated is used directly. In an indirect system a heat transfer fluid is used to transfer the heat gathered by the collectors to the water that will be used in the building.
There are a number of different solar collector technologies, such as Evacuated Tube Collectors, Flat Plate Collectors, Concentrating Collectors and Integral Collector Storage (ICS). Of these, the Flat Plate collector is the most widely used, at least in climates that have seasonal snow since this type easily sheds snow.
In all of these systems, a heat transfer fluid is used to collect the heat of the sun and exchange the heat from the fluid to the water via a heat exchanger. When the heat transfer fluid (often water, propylene glycol-water, or anti-freeze) is heated it rises, moves to the exchanger to pass the heat to water, and then moves towards the storage tank, where it is stored until needed.
Flat Plate collectors are often made of an aluminum case, absorber plates, a tempered (to reduce reflection) glass cover, and other components. The absorber plates sit inside the frame and are made of copper (for conductivity) and coated black for best solar absorption.
Solar thermal collectors have long life spans, up to 30 - 40 years, making these systems quite affordable from a life cycle cost perspective.
Air conditioning in urban areas around the world is a major source of energy consumption that leads to the expensive summer demand peaks that strain the electrical grid, raising prices and pollution levels. The utilization of the sun’s free and clean energy for cooling is an ideal solution.
With solar cooling, it is the heat of the sun hitting buildings that is utilized.
