Connection of collectors and integrated design of solar water heating system
Connection of collector
Since solar heating generally requires a collector of tens of square meters, and each collector module generally only has a few square meters, each solar collector system must be installed as a solar collector array. Different arrangements have an impact on the flow rate and heat exchange of each collector, and have a great impact on the overall performance of the system. Therefore, how to arrange the collectors in the array is an important issue.
There are three ways of connecting collectors into collector groups: series, parallel and series-parallel. For natural circulation systems, collectors cannot be connected in series. Otherwise, the system is difficult to circulate due to the large circulation flow resistance. It can only be connected in parallel, and the number of collectors in each collector group should not exceed 16 or the total area should not exceed 32m².
For non-natural circulation systems, the collectors can be connected in series or in parallel. Generally, parallel connection is used. When series connection is used, the number of collectors should not exceed three.
For flat-plate collectors, the parallel connection is to connect the top and bottom of one end of the collector to the top and bottom of another collector, as shown in Figure 1. After the parallel connection, the first collector and the last collector each have one port, one port is reserved on one side, and the other side is reserved to form a diagonal passage.
When connecting in series, connect the top of one end of the collector to the bottom of the other collector, as shown in Figure 2. After the series connection, one port is reserved for the first collector and the last collector, one port is left on one side, and the other side is left to form a diagonal passage.
3. Series-parallel system
For the forced circulation hot water system, due to the large heat collection area and the water pump as the circulating power, the connection of the collectors mostly adopts series-parallel or parallel-series hybrid connection, as shown in Figure 3.
4. Parallel series system
It connects the collectors connected in parallel to form a single unit and then connects in series to form a single array, as shown in Figure 4.
Integrated design of solar water heating system
Since 2002, the National Housing and Residential Environment Engineering Technology Center has carried out research on the subject of “Technology Development of Solar Energy in the Hot Water Supply of Residential Buildings”, a special fund project for technology development and research of national scientific research institutes for 3 years. Based on the actual survey of residential buildings and hot water systems, the research group carried out research on key technologies such as the integration of solar water heating systems and buildings, system design, installation and construction, proposed integrated design methods and design points for residential solar water heating systems, established an integrated design of technical and economic evaluation index system, and filled the gap in China. At the same time, the design direction of the modification of the combination of solar water heaters and buildings is clarified, which is conducive to the engineering and industrialization of solar energy products. These scientific research results are of practical significance for guiding the design of residential solar water heating systems in China and promoting engineering promotion.
Integrated design refers to the design of a residential building that uses solar energy (or combined with other energy sources) to provide a domestic hot water system as a heat source, including the entire process from planning and positioning to completing the construction drawing design. The integrated design should comprehensively consider factors such as regional resource conditions, residential building types, economic affordability, building layout, building appearance, hot water consumption and usage conditions, collector form and performance, system configuration, operation mode, installation method, interface form and size, safety, maintenance, and economic and technical indicators, and professional participation in construction, structure, water supply and drainage, electrical, and gas, so that the solar water heating system meets the design requirements of residential projects . The research group also proposed the principles to be followed in the integrated design of solar water heating systems:
First, give priority to and make full use of solar energy; second, provide a stable hot water supply; third, the installation location and connection form of equipment and components should be considered in coordination with the design of related professions such as construction; fourth, the installation of the system should ensure safety, reliability and easy maintenance. These principles respectively reflect the energy-saving, use function, adaptability and safety of the residential solar water heating system. On the basis of a large number of investigations and tests, the research group introduced in detail the integrated design process of residential building solar water heating system engineering, including: the feasibility study of solar energy as a hot water source; architectural integration design of solar water heating system, water system integration design, structural integration design and construction technology, technical and economic evaluation and water heater retrofit design, etc.