Solar photovoltaic system refers to a facility that uses the photovoltaic effect of photovoltaic semiconductor materials to convert solar energy into DC electricity, working with inverters like 2000w pure sine wave inverter or 3000 watt solar inverter. Based on its universal, harmless and long-lasting advantages, solar energy has become the most promising new energy source.
However, the home solar power system also has the problem that due to insufficient heat dissipation, the operating temperature of the surface of the photovoltaic panels is too high, which has a negative impact on the conversion efficiency of the system.
This article will introduce to you the current solar panel cooling methods, compare these technologies based on multiple factors such as cooling effect, feasibility, energy consumption, economy and structure, and analyze the advantages and disadvantages of the current technologies.
Main content:
1. The importance of solar panel cooling
The main materials of solar panels include monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film LFP battery, among which monocrystalline silicon and polycrystalline silicon batteries are used the most. The power generation efficiency of crystalline silicon solar cells depends on their operating temperature. Every 1℃ increase in temperature will cause the output power to decrease by 0.4%~0.5%.
Since more than 80% of the energy reaching the battery surface is converted into heat, the operating temperature of solar cells is usually above 50℃, and even reaches 80℃ when heat dissipation is poor. Excessive temperature of solar photovoltaic panels will seriously affect the photoelectric conversion efficiency of solar cells. Therefore, research on solar panel cooling technology to reduce the temperature is of great significance for improving the power generation efficiency of solar photovoltaic systems.
When a photovoltaic system is operating, solar panel cooling is a key factor to make it high efficiency solar panels. Proper cooling improves electrical efficiency and reduces the rate at which cells degrade over time, maximizing the life of PV modules.
2. Current solar panel cooling technologies
- Natural circulation cooling technology: Natural circulation cooling technology refers to adding fins, channels and other structures on the back of the solar panel to cool the panel. It mainly uses air or water as the working medium to absorb heat to achieve the purpose of solar panel cooling. Since the thermal conductivity of water is greater than that of air, the water cooling effect is better than air cooling under ventilation conditions.
- Forced circulation cooling technology: Forced circulation cooling technology mainly adopts a forced flow circulation system by adding fins, channels and other structures, which requires additional driving power. The working medium mainly uses air or liquid with high transmittance. But adding extra power will undoubtedly increase costs.
- Combination of natural circulation cooling and forced circulation cooling: Solar photovoltaic thermal (PV/T) cooling technology combines photovoltaic cells with solar collectors, which is a combination of natural circulation cooling and forced circulation cooling. The conversion efficiency of PV/T solar panel cooling technology is about 40% to 80%, which is higher than that of simple solar photovoltaic cells and solar water heaters.
3. Comparison of solar panel cooling technologies
Solar panel cooling technology is very important to improve the power generation efficiency of solar panels. It must not only reduce the battery temperature and ensure the uniformity of the panel surface temperature, but also consider the reliability and cost of the solar panel cooling technology.
Natural circulation cooling technology has low initial investment and is easy to install. It is suitable for ordinary photovoltaic power generation systems or low-magnification concentrated photovoltaic systems. The cooling effect of forced circulation cooling technology is better than that of natural circulation cooling technology, but it requires increased driving force and higher initial investment.
A comparison of the conventional parameters of the three different cooling technologies is as below:
|
Natural cooling technology |
Forced cooling technology |
PV/T system |
|
|
Temperature reduce range |
<15℃ |
15-50℃ |
15-30℃ |
|
Cooling cycle drive |
No |
Yes |
Yes |
|
Photoelectric conversion efficiency |
10%-15% |
11%-27% |
6%-27% |
|
Photothermal conversion efficiency |
0 |
0 |
30%-64% |
|
Total solar energy conversion efficiency |
10%-15% |
11%-27% |
40%-80% |
|
Advantages |
No additional investment is required in the initial stage, the structure is relatively simple and easy to maintain. |
The cooling effect is better, the investment is less than the PV/T system, and the maintenance is easier. |
It can significantly improve solar energy utilization efficiency. |
|
Disadvantages |
The cooling effect is limited, and the heat is lost to the environment and is not utilized. |
Additional input power is required, and the heat is lost to the environment and is not utilized. |
It is difficult to increase electrical efficiency and thermal efficiency at the same time, and the technology is imperfect. |
|
Initial investment |
Small |
Relatively large |
Large |
We can see from the table that the existing commonly used cooling methods have their own advantages and disadvantages. Judging from the current conditions, the natural cooling system has a high commercial investment value.
In the long run, the PV/T system will be better, but it is difficult to increase the power efficiency and thermal efficiency of the current technology at the same time. With the development of various technologies, this system will have a wider market when the investment cost decreases.
4. Solar panel cooling technology development direction
The current solar panel cooling technologies have certain limitations. Although traditional solar panel cooling technology improves the conversion efficiency and power of photovoltaic panels, the improvement is not significant enough and the heat transfer resistance is still large.
In addition, external cooling sources are provided. When the temperature is high, uneven temperature distribution on the surface of photovoltaic panels is prone to occur.
The future direction of technology development should be that no matter what technology is chosen to cool photovoltaic panels, it should keep the working surface temperature low and stable, be simple and reliable, and be able to use the extracted heat energy to improve the overall conversion efficiency, so as to achieve the development goals of saving fuel and protecting the environment, and better promote solar energy as a new energy source into practical applications.
Traditional solar panel cooling technologies include natural convection cycle cooling, forced convection cycle cooling, and liquid cooling. New cooling methods include FTTC, PV/T, PV/TE and PV-PCMs. Based on the advantages and limitations of respective technologies, future improvements to traditional technologies and the development direction of new technologies are proposed:
① Natural/forced cooling:
The natural/forced circulation convection cooling technology through air cooling is gradually getting mature, easy to operate, and the system is simple, but it should be adapted to local conditions and choose the appropriate method according to the geographical environment; it can increase the surface convection heat transfer coefficient while increasing the heat exchange area.
Establish a complete monitoring and automatic control system to avoid uneven temperature distribution on the surface of photovoltaic panels, and adjust the working power of external cold sources at any time according to changes in external conditions, ensuring better economic benefits while ensuring conversion efficiency.
In the development direction of liquid cooling, what needs to be solved is the problem of evaporating water after water cooling, using this part of the heat to collect more solar radiation, and solving the operational stability of the system, combining liquid cooling and solar heat collection to reduce operating costs and improve overall efficiency.
② New technologies:
- The development of new technologies must be more in line with economic indicators, and fully consider the possibility of promotion to practical applications.
- Strive to improve the cycle stability of the system.
- Focus on solving the problems that still exist with current new technologies, and integrate PCMs, heat management and energy storage technology to form a complete heat cycle.
- At the same time, composite phase change materials are developed, by adding nucleating agents, thickeners, using ultrasonic technology, etc. to improve the cycle stability of PCMs and rationally design phase change storage.
- The structure of the inner tank and coil assembly of the thermal device can avoid problems such as uneven heat transfer of the heat exchange elements and inability to fully utilize the phase change material.
③ Future research:
Future research must focus on efficiently collecting heat from the surface of photovoltaic modules and cooling them in a more controllable and stable manner. Solar panel cooling technology can be better developed from three aspects:
- Reducing thermal resistance
- Lowering temperature
- Improving photovoltaic panel performance.
At the same time, based on comprehensive considerations such as material use, capital cost and performance, it can be better adapted to application and promotion.
Conclusion
Due to the temperature effect of solar panels, it is very necessary for solar photovoltaic power generation systems to take solar panel cooling measures during operation. Several commonly used solar panel cooling technologies have their own advantages and disadvantages. From an economic and technical perspective, natural cooling technology is more preferred.
Since the initial investment is small, it is conducive to large-scale promotion and can easily form a commercial model. The initial investment of forced circulation cooling technology is high and maintenance is difficult. The PV/T system can have higher solar energy conversion efficiency than the other two types, but it is difficult to increase the electrical efficiency and thermal efficiency at the same time, and further research is still needed.
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