Views:4 Author:Site Editor Publish Time: 2018-04-02 Origin:Site
The solar collector technology includes plate type, vacuum tube type, trough type,
heliostat type, fresnel type, and other types of heat collecting technology, in which theflat type is generally adopted by a low temperature heat collecting system. At present, more than 95% of solar collectors in the world use plate-type heat collection systems.The relevant issues of the flat panel solar collector technology are described as
1. Characteristics of flat plate collector
· Efficient. At present, the flat plate collector developed internationally has a light
efficiency of 78 to 82%, and the heat loss is only ≤ 3W/m2°C. The light efficiency of the current flat plate collector in China is also about 72%, and individual reaches 75%,and the heat loss is ≤ 6W/m2°C.
· Safe and reliable long life. Plate collector frame and heat absorbing plate are basically made of metal materials, and the cover plate is made of tempered glass or glass fibermaterial. The material is building materials, which is reliable and durable, and the service life can be more than 20 years.
· Can withstand pressure operation. Generally can withstand more than 0.6MPa.
· Easy to install. Modular installation, convenient and quick.
· Combined with architecture. The building provides the installation platform and
structural elements for the collectors.
· Flat plate collectors have poor frost resistance, but the use of emptying techniques
andantifreeze media can effectively solve winter problems.
2. Status and gaps in the development of plate collectors at home
· The representative of the thermal performance level of the plate collector is the instantaneous efficiency curve and equation , where
the intercept of the optical efficiency curve. At present, the international reachable 0.78 ~ 0.82, our country is only 0.72 ~ 0.75, as a design factor, generally 0.9 ~ 1.0, and the collector tube spacing, the thickness of theheat absorption plate, the diameter of the collecting pipe and so on; for the
transparent cover through, the rate is about 0.92 in the world, and China's current rate is 0.85, which can reach 0.90 individually. The absorption rate of solar radiation for
heat absorbing plates is generally 0.94 to 0.96 in the world and 0.90 to 0.92 in China. The above-mentioned light efficiency difference between domestic and international
is 6 to 10%.
· is heat loss coefficient.
The heat loss requirement of plate collectors in China is ≤6W/㎡℃, and the international level is≤4W/㎡℃. The reason for the large heat loss in China's products is the low level of manufacturing process, poor sealing, and large heat transfer losses. Therefore, the heat loss
is 2～3 W/㎡℃.
· China's flat-plate collectors are basically hand-crafted. Internationally, they are basically industrialized and informatized. They have advanced equipment, high-level
technology, stable product performance, and high product quality. For example, the
continuous sputtering coating technology of the heat absorbing plate can achieve an absorption rate of 0.94 to 0.96, an emissivity of 0.04 to 0.07, a processing speed of 2 m/sec, and a 100 m unevenness of 0.02%.
· The fittings used in foreign flat-plate collector systems, such as pipes, valves, and watches, are well-supported, making the system level much higher than the current
level in China.
3. Development direction and key technologies to be broken
vigorously developed and promoted, and should be actively promoted and applied
especially in solar hot water system projects.
·To increase the light efficiency of the plate collector. Among them, we must increase the transmittance of the cover plate, develop and promote the use of low-iron glass
and other high-transmittance cover plates, strengthen the research and development ofanti-reflective coatings, reduce their costs, and improve the absorption rate of
heat-absorbing plates. Selective coating development and mass production to reach
the level of 0.94 to 0.95.
·To reduce heat loss. There are two ways. First, reduce the infrared emissivity of the
heat-absorbing coating to reach the international level of 0.04 to 0.07. The second is
to improve the heat-preserving tightness, and use new materials, new technologies, etc.to reduce convection losses and conduction losses.
· Vigorously develop mechanized and automated processing equipment. Such as
continuous sputtering coating machine, collector plate, automatic welding machine,
automatic frame, automatic molding machine, insulation material molding machine ... ... to reduce costs.
·The use of an efficient, safe, long-life flat-plate collector to develop pressure-bearing, multi-assisted, energy-saving, all-weather intelligent solar control hot water systems
for widespread use.
4. Solutions and measures to be taken
·Learn from foreign advanced technology, take the road of introduction,
improvement and self-innovation. Develop international cooperation, domestic
alliances, joint introduction, and joint development.
· The Ministry of Science and Technology provides support in the “Twelfth Five-Year Plan” scientific and technological research projects, especially in the development of continuous plate coating technology and equipment for flat-plate collector
heat-absorbing plates, which should be given scientific and technological approvals
and support; the National Development and Reform Commission Energy Bureau
should make major equipment changes. China can also give support.
· Inspirational companies that develop flat-plate solar collectors should increase their
investment in capital, personnel, organization and management, increase their efforts
in development and improvement, and actively apply for major national and local
projects and organizations.
· Companies should strengthen the pilot demonstration of the development and
application of flat panel solar collector heating systems.
· In order to focus on joint development and key breakthroughs, based on the
principle of voluntariness, mutual benefit, and alliance, the Solar Thermal Industry
Alliance (Association) will establish a panel-type solar water heater professional
committee to organize, coordinate, and promote the development of flat-panel solar
collector technology and industrialization.