A solar concentrator is a device designed to focus and concentrate solar radiation, and its application can be both in the generation of solar thermal energy and in the generation of solar photovoltaic energy.
Its operation is based on the use of reflective surfaces, typically formed by a series of mirrors arranged in an aligned arrangement. The main purpose of these solar concentrators is to capture the greatest amount of solar radiation possible and direct it towards a small receiver.
In the context of larger-scale solar thermal energy, this concentrated solar radiation is used to heat a thermal fluid, such as water or oil, to generate steam. The resulting steam drives steam turbines, thus transforming solar radiation into mechanical energy to power an electrical generator or perform physical work.
On the other hand, solar concentrators also find applications in the field of photovoltaic solar energy. In this case, instead of generating heat, concentrated solar radiation directly affects high-efficiency photovoltaic cells.
Solar concentrators are based on the principle of concentrating sunlight at a point or along a line to increase the intensity of solar radiation incident at that point. This is achieved by reflecting the sun's rays using mirrors or lenses. Once sunlight is concentrated at the focal point or along a line, it can be used to generate heat or electricity, depending on the type of concentrator.
In the case of solar thermal concentrators, such as parabolic dish concentrators, concentrated sunlight is used to heat a thermal fluid. This fluid can be water, oil or another medium, and is used to generate steam that drives a turbine connected to an electrical generator.
Instead, photovoltaic solar concentrators concentrate sunlight into photovoltaic cells, which convert solar radiation into electricity directly.
Types of Solar Concentrators
There are several types of solar concentrators, each designed to optimize the capture of sunlight in a different way.
The main types of concentrators include:
Parabolic Dish Solar Concentrator
This type of concentrator uses a series of parabolic mirrors that concentrate sunlight into a focal point. At this point, a pipe is placed containing a thermal fluid, such as oil, which is heated and used to generate steam, driving a turbine that produces electricity.
Parabolic dish solar concentrators are ideal for large-scale power generation applications and are commonly used in solar thermal power plants.
Linear Fresnel Solar Concentrator
These concentrators use a series of flat mirrors to reflect sunlight into a receiving tube. As the sun moves throughout the day, the mirrors adjust to keep the sunlight focused on the tube.
The main advantage of linear Fresnel concentrators is their ability to be used in low and high temperature applications, making them versatile.
Composite Channel Parabolic Solar Concentrator
This design is similar to the parabolic dish concentrator, but uses a channel instead of a focal point to collect sunlight. This allows it to be used for solar cooling applications in addition to power generation.
Solar Trough Solar Concentrator
A Solar Trough solar concentrator is a variant of the parabolic dish concentrator, designed to be more affordable and easier to install. It is especially suitable for power generation in decentralized applications, such as industrial and commercial facilities.
Active Sun Tracking System
One of the fundamental challenges of these systems lies in ensuring that solar radiation falls parallel to the axis of the concentrator throughout the course of the day. To achieve this, once the solar concentrator is built, the implementation of a tracking system that follows the apparent movement of the sun is required. This tracking system is guided by a control system that constantly adjusts the orientation of the concentrator.
In the case of smaller scale solar concentrators, effective tracking of the sun can be ensured by directly applying a tracking system to the concentrator. However, as the size of solar concentrators increases, deformations can arise in the parabolic surface that affect their operation.
To address this challenge, one or more intermediate flat mirrors known as heliostats are used. These heliostats help maintain solar reflection at the focal point of the concentrator, even when deformations occur on the surface, thus guaranteeing optimal operation of the system.
Applications of Solar Concentrators
The most common use is the generation of electricity. However, there are also other techniques to harness thermal energy directly.
1. Electricity Generation
Electricity generation is the most used application of solar concentrators. This can be achieved in two ways:
Generate steam and drive steam turbines.
Using a Stirling engine connected to an electric generator.
Sometimes this technique is also used to power photovoltaic cells. So they are photovoltaic solar energy installations.
2. Solar Cookers
With small 3D concentrators, solar cookers can be made. The concentrator can be between 80 cm and 2 meters. In the focal area, a “stove” is placed where the container with the contents to be prepared rests.
3. Industrial Applications
Solar concentrators make it possible to harness solar energy in multiple industrial applications, such as, for example, in the metallurgical industry, metal smelting, steam production for the chemical industry and process heating.
4. Water Desalination
Solar concentrators can be used to heat seawater and generate steam, which is then condensed into fresh water. This is especially useful in water-scarce regions.
5. Residential and Commercial Heating
Solar concentrator systems are also used to provide heating and hot water in residential and commercial buildings, reducing dependence on fossil fuels.
Solar concentrators offer several significant advantages compared to conventional solar systems that do not use concentration:
Greater efficiency: By concentrating sunlight, concentrators increase the efficiency of converting solar energy into electricity or heat. This allows for more efficient power generation, especially in areas with high levels of solar radiation.
Less materials used: Since fewer solar panels or photovoltaic cells are required to generate the same amount of energy, solar concentrators can help reduce the amount of materials needed in the installation.
Thermal storage: Solar thermal concentrators allow heat storage, facilitating the generation of electricity at night or on cloudy days. This solves one of the main challenges of intermittent solar energy.
Multiple Applications: Solar concentrators can be used for both electricity generation and solar heating and cooling applications, increasing their versatility.