High-Efficiency Flat Plate Solar Collectors: Technology, Manufacturing, and Future Outlook by BTE Solar

Flat Plate Solar Collector Operating Principle

The basic operating principle of a flat-plate solar collector is very simple. In short, sunlight shines through a transparent cover onto a heat absorber coated with an absorbent layer. Most of the solar radiation is absorbed by the absorber, converted into heat, and transferred to the working fluid in the fluid channels. Thus, the cold working fluid entering the collector's bottom inlet is heated by the solar energy in the fluid channels, gradually increasing in temperature. The heated working fluid, carrying useful heat energy, exits the collector's top end and is stored in a water tank for future use, representing useful energy gain. Meanwhile, as the temperature of the heat absorber rises, heat is dissipated to the environment through the transparent cover and outer shell, resulting in various heat losses in the flat-plate solar collector. This is the operating principle of a flat-plate solar collector.

Fabrication Method

The flat-plate solar collector panel core and its manufacturing method consist of two metal sheets stacked together, joined together using a seam-seaming process to form a flat metal heat absorber. The bottom is padded with galvanized sheet metal and thermal insulation, and the top is covered with a glass sheet, sealed with rubber strips. The bottom of the groove on the light-receiving panel is stamped and connected to the back panel, forming a fluid flow channel that interconnects horizontally and vertically. After fabrication, the following must be ensured: Air-dried solar panels should exhibit no deformation, cracking, or other damage; Sunk-dried solar panels should exhibit no leakage or noticeable deformation; Internal water-induced thermal shock should exhibit no leakage, deformation, cracking, or other damage; External water-induced thermal shock should exhibit no noticeable deformation or other damage; and Water ingress into the collector should not significantly impair thermal performance.

Fabrication and Construction

General Specifications:

1. Villa Panels: 2000*1000*80, 2000*1000*95; 

2. Balcony Panels: 2500*800*80, 2000*800*80, 2000*1250*80; 

3. Standard Interface: Φ22, capable of processing DN20 or DN15 female or male threaded connectors.

Construction and Installation

The system's construction and installation must ensure safety and functionality, while also considering integration with the building. 

1. Pre-installed embedded parts or fixing bolts should be installed on the structure where the collector (water heater) will be installed. When the collector is installed on a masonry wall, additional structural columns should be added at the location of the embedded parts. Collectors should not be installed on non-structural load-bearing components, such as lightweight infill walls. 

2. The waterproofing layer must not be damaged in areas requiring waterproofing. 

3. When using brackets for installation, the strength, durability, and fixing method to the building must be checked in accordance with the design drawings. 

4. Reliable lightning protection measures must be implemented. 

5. The water storage tank base must be located on the building's load-bearing wall (beam), and pre-installed embedded parts must be reserved for fixing. The gap between the embedded components and the base should be compacted with fine stone concrete.

6. The water tank should be securely connected to the foundation with anchor bolts.

7. When installing pipes, do not pass them through structural beams, columns, hidden columns in seismic walls, or end columns. Pipes should be pre-buried when passing through roofs and walls to avoid drilling holes in waterproofed and insulated roofs.

Development and Outlook

The key to the development of flat-plate solar energy lies in technological innovation and the development of products that meet consumer needs. Improving technology and reducing costs are key to the development of flat-plate solar energy. Flat-plate solar energy products that meet consumer needs require addressing four key technical issues: cover technology; high-efficiency absorber technology; improved insulation and sealing; heat loss reduction technology; and the development of process equipment to achieve industrialized production, improve efficiency, and reduce costs. 

Careful research on market trends and consumer needs is necessary, and the following measures should be implemented to improve the performance and quality of flat-plate collectors: 

1. Research and develop selective coatings suitable for flat-plate solar collectors. These coatings should have high absorptivity, low infrared emissivity, excellent heat, humidity, and weather resistance, and reasonable processing costs. 

2. Widespread adoption of low-iron, high-transmittance cover glass. Currently, several glass manufacturers have begun producing low-iron glass suitable for solar collectors, and the gap in glass quality between domestic and foreign manufacturers is narrowing.

3. Emphasize optimized collector design, improve manufacturing processes, ensure structural integrity, and reduce heat loss from the collector.

4. Select tempered glass for the collector cover to improve the quality of collector components. Optimize the structural design to ensure the collector can withstand performance tests such as hail, rain, exposure to sunlight, pressure resistance, and thermal shock, thereby extending collector life and reducing system maintenance costs.

5. To meet the special requirements of cold regions, solar heating and air conditioning, and industrial heating, high-efficiency flat-plate collectors should be developed. Technologies such as double-layer covers and transparent honeycombs should be industrialized as quickly as possible, and their cost-effectiveness should be improved to ensure that high-efficiency flat-plate collectors have strong market competitiveness.

6. Track advanced technologies and processes for flat-plate collectors abroad to develop new flat-plate collector solar systems and increase the market share of flat-plate collectors. Flat-plate collectors can not only be used as water heaters, but new collector products can also be developed based on their technology. For example, high-efficiency air collectors can be developed using their efficient selective coatings, optimized fin structures, and air flow channels. Air collectors can be used for active and passive heating and industrial and agricultural drying, and have broad application prospects. Based on flat-plate collectors, laser welding and integral lamination processes can also be used to develop photovoltaic and solar thermal integrated utilization products, such as photovoltaic water heaters, photovoltaic heat pumps, and solar direct evaporation heat pumps. Solar water heating is only the most basic mode of solar energy application. Solar heating, drying, power generation, lighting, cooling, and other industrial applications will become increasingly widespread. As the country continues to deepen its measures on renewable energy applications, green building promotion, and renewable energy demonstration cities, flat-plate collectors will surely develop rapidly due to their unique advantages.

Company Profile:

Dezhou BTE Solar Co., Ltd. is founded in 2009, located in Shandong Province,China, which is an innovative company focused on the field of solar thermal applications and has a number of independently intellectual property rights in core technology. Relying on high advanced technical strength, we have independently developed the full automatic production lines, and production efficiency has reached the international level. Based on the idea of industrial 4.0, it has built a global professional solar thermal system in High , med Ium and low temperature like flat plate collector, U pipe collector, heat pipe collector and solar water heaters. Now BTE is not only a manufacture, also supply different energy saving solutions to global partners.

Now BTE products have pass Solar Key Mark and CE certificate. We have developed various solar collectors for different working temperature and circumstance. The solar thermal products include flat plate collectors, U pipe collectors, Heat pipe collectors, manifold collectors, compact pressurized and non-pressure solar water heater. We have cooperated with many home and abroad enterprises for long-term in solar system. We have been devoting ourselves to research, development and innovation of solar energy core technology. With the aim of creating professional flat plate collector producing base in the world, we will work to make the world more energy saving and beautiful with the cleaning circumstance.