It’s becoming more and more important to understand the different possibilities accessible as renewable energy gains popularity worldwide. Solar thermal energy is one of the less well-known but incredibly effective kinds of renewable energy. We will explore the definition of solar thermal energy, the operation of solar thermal panels, the kinds of systems that are available, and much more in this tutorial.
What Is Solar Thermal Energy?
In contrast to solar photovoltaic (PV) energy, solar thermal energy uses the sun’s energy to produce heat instead of electricity. After that, this heat is put to use in a variety of ways, including space heating, water heating, and in certain large-scale operations, electricity production. The equipment used to collect and use this energy is called solar thermal panels or collectors.
How Do Solar Thermal Panels Work?
The main components of solar thermal systems, solar thermal panels use the sun’s heat to heat your home or supply hot water for various uses. This is an explanation of how they transform sunlight into heat that is useful:
Flat-Plate Collectors
Solar PV panels are similar to flat-plate collectors. They are made up of a transparent cover, a heat-insulating backing, a dark absorbing surface, and a fluid that transfers heat from the absorber to a water tank. The absorber can be made of a variety of materials, including steel, copper, aluminum, or polymers. The most costly conductor is copper, which is also the most durable and effective.
Evacuated Tube Collectors
Flat-plate collectors and evacuated tube collectors are not the same. The transfer fluid passes through several glass tubes that make up this structure. Since these systems are vacuum-sealed, heat loss is prevented, making them especially effective in colder climates. But because they run the risk of overheating in warmer conditions, they can lose effectiveness.
Types of Solar Thermal Systems
Active Systems
Active systems move the fluid that transfers heat from the collectors to the storage tank using mechanical pumps and controllers. Although there is more control and efficiency with this system, there are higher installation and maintenance costs.
Passive Systems
In passive systems, the heat-transfer fluid is moved by natural convection. These systems might not be as effective as active systems, but they are easier to install and maintain at a lower cost.
Flat-plate collectors
These solar collector types are the most widely used ones. They are made out of a dark absorber plate that is glazed with either plastic or glass. The absorber plate becomes heated by sunlight that enters through the glass. After that, the heat is transmitted to a fluid that transfers heat through tubes that are fastened to the absorber plate’s rear.
Evacuated tube collectors
Although they cost more, these are more effective than flat-plate collectors. They are made up of metal absorber tubes inside evacuated glass tubes. Heat loss is reduced to some extent by the vacuum between the two tubes. For your house or place of business, solar thermal systems can be an affordable solution to heat the water or air. They can also help you save money on energy costs and lessen your dependency on fossil fuels.
Types of Thermal Energy Storage Systems
Systems for storing and utilizing thermal energy (TES) are essential for managing heat energy. By storing thermal energy for later use, they close the gap between supply and demand by capturing it while it is easily accessible. The three primary categories of TES systems are broken down as follows:
1. Sensible Heat Storage
This most basic type of thermal energy storage (TES) raises the temperature of a storage medium to store thermal energy.
- Materials: Frequently utilized storage media include water, rocks, molten salts, and even concrete because of their great heat capacity.
- Charging and Discharging: Heat is withdrawn to be used when discharging (e.g., for heating buildings) and added to the storage medium while charging (e.g., from solar thermal collectors).
- Applications: In both residential and commercial buildings, sensible heat storage is extensively utilized for hot water and space heating purposes. In industrial processes with variable heat demands, it is also employed.
2. Latent Heat Storage
This process makes use of the energy emitted or absorbed as a material changes phases (usually from solid to liquid or liquid to gas).
- Materials: Phase Change Materials (PCMs) are carefully selected materials that release heat when they solidify after absorbing a significant amount of heat during melting. Salt hydrates, chemical molecules, and paraffin waxes are among the options.
- Charging and Discharging: During charging, heat is applied to the PCM, making it melt and store the thermal energy. The PCM solidifies while discharging, releasing the heat that has been stored for usage.
- Applications: Applications needing a steady temperature output, such food processing or building heating systems, are ideal for latent heat storage.
3. Thermo-Chemical Heat Storage
This cutting-edge technique stores heat energy through chemical processes.
- Process: Heat is absorbed by a chemical process during charging, and released during discharging by the opposite reaction. Because of their capacity to go through these reversible processes, certain materials are selected.
- Challenges: The development of thermo-chemical storage is currently ongoing, and problems include reaction cycle management and the procurement of economical and effective materials.
- Potential Applications: High energy density storage is provided by this technology, which may be useful for long-term energy storage uses such as utility-scale power generation.
Components of a Solar Thermal System
- Collectors: Capture the sun’s heat.
- Heat Transfer Fluid: Transports heat from the collectors to the storage or usage point.
- Storage Tank: Stores the heated fluid for later use.
- Pumps and Controllers: Circulate the heat-transfer fluid (in active systems).
- Heat Exchanger: Transfers heat to the domestic water supply or heating system.
Benefits of Solar Thermal Panels
- Efficiency: Solar thermal panels are more efficient than PV panels because heat waves carry more energy than sunlight.
- Cost-Effective: They are cheaper and have a shorter payback period than PV panels.
- Versatile: Works in cold climates, overcast weather, and strong winds, and comes with an energy storage system.
- Long-Lasting: Most systems come with a 5-10-year warranty but can last up to 25 years with minimal maintenance.
- Environmental Impact: Help reduce carbon dioxide emissions by up to 600 kg per year.
- Incentives: Eligible for payments under schemes like the Renewable Heat Incentive (RHI).
Applications of Solar Thermal Energy
Solar thermal energy is a direct solar heat-harvesting technology that may be used for anything from large-scale electricity production to heating water in your home. These are a few uses for it:
- Domestic Hot Water: Solar water heaters are a popular application that stores heat in storage tanks and uses collectors to gather heat. These devices can drastically lessen the need for traditional water heating techniques.
- Space Heating and Cooling: Radiators and radiant flooring can be heated by hot water or air circulated through solar thermal systems. They can also be used with absorption chillers in some situations to provide solar-powered air conditioning.
- Swimming Pool Heating: Similar to solar water heaters, solar pool heaters use heat collection to increase swimming season duration while lowering the need for gas or electric heaters.
- Industrial Processes: Solar thermal energy can be used by industries for several things, including the production of steam, hot water, and drying applications in industries including brick-making, food processing, and textiles.
- Electricity Generation: Mirrors are used in concentrated solar power (CSP) facilities to direct sunlight onto a receiver, which raises the temperature of a fluid. After that, this heat is converted to steam, which powers turbines to create electricity.
- Other Applications: This process, solar cooking, and even high-temperature sun furnaces for industrial operations are among the many uses for solar thermal technologies.
Installation Process
The following actions are often involved in the installation of solar thermal panels:
- Site Assessment: Determine if your property is suitable for solar thermal panels.
- System Design: Choose the appropriate system and components.
- Permitting: Obtain the necessary permits and approvals.
- Installation: Install the panels, piping, and other components.
- Commissioning: Test the system to ensure it operates correctly.
What Is The Difference Between Solar Thermal and Solar PV?
| Feature | Solar Thermal | Solar PV |
| Energy Output | Heat | Electricity |
| Technology | Uses collectors to capture sunlight and heat a transfer fluid | Uses photovoltaic cells to convert sunlight directly into electricity |
| Efficiency | Up to 70% | Around 20-22% |
| Application | Primarily for heating water | Powers your entire home or business |
| Space Requirement | Less roof space needed | More roof space needed |
| Upfront Cost | Generally lower | Generally higher |
| Versatility | Less versatile (limited to heat) | More versatile (powers electronics) |
| Suitability for Cold Climates | Can still work with diffused sunlight | Less effective in low-sun conditions |
Challenges and Limitations of Solar Thermal
Although a promising renewable resource, solar thermal energy has drawbacks and restrictions of its own. Below is a summary of some important restrictions to think about:
- Land requirements: For concentrated solar power (CSP) and other large-scale solar thermal facilities to effectively catch sunlight, large areas of open land are necessary. In places with a high population density or where there is competition for land usage, this may be difficult.
- Water usage: For cooling, CSP facilities require a large volume of water. In dry areas where water scarcity is already an issue, this could be a significant disadvantage.
- Intermittency: Solar thermal systems are subject to the essential fluctuation of sunlight, much as solar photovoltaic (PV) systems. They are unable to produce electricity at night or when it is cloudy. Although storage solutions are developing, they become more expensive and sophisticated.
- High upfront cost: Installing a solar thermal system requires an important upfront financial outlay, particularly for large-scale CSP systems. Further adoption may be prevented by the high upfront cost despite the low operating costs.
- Limited applications: The main uses for solar thermal systems are in the production of electricity and heat for industrial processes. They might not be the best option for every heating requirement, especially in homes where solar power with battery storage can be more feasible.
- Environmental impact: Large solar thermal plants can affect the environment even though they produce clean energy. When utilized in CSP, mirrored surfaces have the potential to kill birds by confusing them.
Conclusion
One very effective and economical method of using the sun’s power for heating is through solar thermal energy. The use of solar thermal systems is becoming more and more appealing for both residential and commercial applications as a result of technological improvements.