Active solar energy classifies technologies related to the use of solar energy that use mechanical or electrical equipment to improve performance or to process the energy obtained by converting it into electrical or mechanical energy. These equipments can be fans, water pumps, etc.
By contrast, solar systems that do not use these devices are classified as passive solar energy systems.
Passive solar systems do not require additional energy to operate and therefore have zero operating costs, do not emit operating greenhouse gases, and can have low maintenance costs, passive solar technology must be fully treated.
Types of active solar energy
The applications of active solar energy can be classified into two types:
- Thermal solar energy
- Photovoltaic Solar Energy
Thermal solar energy
Thermal solar energy takes advantage of the properties of thermodynamics to increase the temperature of a fluid by increasing its heat energy and, therefore, its entropy. In this form of use of solar energy, electricity is not generated except in thermoelectric solar plants.
The systems of hot water that are not based on the system used thermosyphon water pumps and fans to circulate the water within their circuits. For this reason, these systems would be classified as active solar energy. In contrast, solar water systems that use thermosiphon, the circulation of the water is carried out by means of the difference in densities between hot and cold water, they do not need external mechanisms and, therefore, they are classified as passive solar energy systems.
The majority of solar collectors are placed on fixed supports with a calculated orientation so that they can capture as much solar radiation during the day and throughout the year. But these collectors would be more efficient if they could modify their orientation towards the Sun depending on the day of the year and the time of day.
There are systems to be able to modify the orientation of the solar collectors. In case these systems are mechanical, they would be active solar energy systems.
In the case of concentrated thermal solar energy, it is necessary to install solar monitoring systems. This type of installation needs to focus the solar radiation received at a point, therefore the mirrors have to adapt their function in relation to the position of the Sun.
Generally, the function of this type of system is used in thermoelectric solar plants with the aim of generating electricity.
Photovoltaic Solar Energy
Photovoltaic solar energy is clearly an active solar energy system. Thanks to the photovoltaic effect, photovoltaic panels can generate electricity that will later go through transformers and other external elements.
Comparison between passive and active solar energy
An interesting hybrid method is to use a solar panel to operate pumps or fans. A data analysis, using thermodynamic and heat transfer software, can be used to compare the results of various active and passive solar thermal strategies.