A solar furnace is an optical system to provide concentrated solar radiation. The concentrated energy of sunlight can be used to:
- Simple heating of a material.
- Plastic or paint aging experiments
- Endothermic chemical reactions
- Charging experiments with mechanical or electrical components.
The solar furnace system is widely used in solar thermal power plants.
The difference between the solar furnace system and a solar panel is that the solar panel captures and converts the solar energy directly, while the solar furnace only reflects it and concentrates it at one point.
How Does a Solar Furnace Work?
The concentration component of a solar furnace works in principle as a lit glass. For technical reasons, however, a hollow or parabolic mirror is used, which concentrates the incident light from the sun at one focal point.
The reflective surface of this hub can be from one square meter to several 100 square meters. If larger areas are required, a heliostat field is generally used, in which several flat mirrors assign light to a single point.
To ensure optimal concentrator illumination, it is necessary to continuously follow the heliostat in the sun. This is done by software that constantly calculates the current position of the sun. Another option is to use a sensor to determine the position of the sun.
For a solar furnace with a concentrator, there are three types:
- Direct tracking hub.
- Stationary on the hub with tracked heliostat.
- Stationary off-axis hub with tracked heliostat.
For larger hubs these are made up of individual flat mirrors. They can also be presented in a Fresnel arrangement of individual focus mirrors.
Reflective components must meet certain qualitative criteria. Therefore, it is important that the reflectivity is as high as possible, or exactly known, as well as the dispersion of the reflective surface. The wavelengths to reflect are also an important criterion, if, for example, you want to make use of the UV components (A, B) of sunlight.
The precondition for effective concentration is direct sunlight. Therefore, weather conditions at the location of a solar furnace play an important role.
What Are the Uses of a Solar Furnace?
The rays are focused on a pot-sized area and can reach a temperature of 4,000 ° C, depending on the installed process, for example:
- Approximately 1000 ° C for metal receivers producing hot air for the next generation of solar towers.
- Approximately 1400 ° C to produce hydrogen by breaking down methane molecules.
- Up to 2500 ° C to test materials that will be used in extreme environments such as nuclear reactors or space vehicles for atmospheric reentry.
- Up to 3500 ° C to produce nanomaterials by solar induced sublimation and controlled cooling, such as carbon nanotubes or zinc nanoparticles.
It has been suggested that solar furnaces could be used in space to provide energy for industrial uses.
Its dependence on sunny weather is a limiting factor as a renewable energy source on Earth, but it could be combined with thermal energy storage systems for the production of energy during cloudy days or at night.
There are also small-scale solar furnaces, in these cases the temperature at the point of concentration is not so high. They are used, for example, to power small Stirling engines or solar cookers.