Solar water heating system (heater) is recognized as a relatively mature energy-saving product, and residents are happy to use it. However, it is actually difficult to promote in cities. The proportion of residential solar water heaters is still very low. The main problems are as follows:

1. The vast majority of solar water heating systems used in China are simple compact solar water heaters, which have many problems with their performance:

① Due to the lack of performance of the solar water heater or the inability to obtain sufficient solar radiation after installation, the operating efficiency of the system is low, and the all-weather hot water supply cannot be guaranteed.

②Solar water heaters cannot be operated under pressure. The water pressure is limited by the installation height of the water heater. The pressure of cold and hot water at the water point is not balanced, which makes it very inconvenient for users to adjust the cold and hot water.

③The cold weather in winter can easily cause the pipeline to freeze and crack, and the vacuum tube “empties” in summer, causing the tube to explode.

2. In the absence of a unified installation, the spontaneous installation of solar water heaters by urban residents has also caused a lot of problems:

① Install solar water heaters on the built roofs, and the pipelines arbitrarily penetrate the walls, which may damage the waterproof structure of the original structure and cause water leakage on the roof and wall.

②Due to the irregular installation, the solar water heater may fall down and bring safety hazards.

③At the beginning of the architectural design, the installation location of solar water heaters was not considered, and the self-installation caused the roof of the building to be disordered and damaged the urban landscape (see Figure 1).

3. When the solar water heating system is applied in high-rise residential buildings, due to the characteristics of the high-rise residential buildings themselves, there are special problems and difficulties in the combination:

① Install solar collectors on the roof. The roof area of high-rise residential buildings is limited, and it is difficult to meet the needs of all users at the same time.

②Install solar collectors on the facade. Due to the uneven distribution of solar energy resources on the elevation of high-rise residential buildings, it is difficult for the residents at the bottom to obtain sufficient solar radiation.

(Read more: How to combine solar collectors with high-rise residential buildings?)

③Excessively long pipelines not only increase the heat loss on the pipelines, but also there is a lot of “ineffective cold water”, which makes the bottom-level residents unable to get hot water immediately during use, resulting in a waste of water resources.

④ If a solar water heater that cannot bear the pressure is used, the pressure of the hot and cold water at the water point is seriously unbalanced.

4. In addition to the problems of the solar water heating system (heater) itself, the government, developers, architects, construction units and users have not paid enough attention to the application of solar water heating systems in the entire application process:

① Although the government has formulated some incentive policies for the development and production of solar water heating systems, there are still few specific incentive policies and subsidies for the application.

②The increased investment in the solar water heating system is borne by the real estate developer, but the benefits brought by energy conservation are enjoyed by the consumers, which cannot bring direct benefits to the developer. It will also cause certain troubles to developers in architectural design, construction, and operation and maintenance. Therefore, real estate developers lack enthusiasm for this new technology.

③Architects and construction units have insufficient understanding of solar water heating systems, and have not considered the installation of solar water heaters in the design and construction of buildings.

④ Ordinary residents’ understanding of solar water heating systems is only limited to ordinary compact vacuum tube solar water heaters, and they lack understanding of the concept and use effects of solar water heating systems. Moreover, house purchases are currently dominated by housing prices, and whether the house is equipped with solar water heating systems will not affect the purchaser’s choice of house purchase. Most people, such as home buyers and users, only regard solar water heating systems as free or cheap domestic hot water facilities, and do not realize its energy saving and environmental protection benefits.

Due to the above-mentioned problems, although the domestic solar water heating system has a relatively high penetration rate in low-rise and multi-storey houses in rural and urban areas, it has not fully achieved a comfortable and stable water supply effect in actual use. Very few high-rise residential buildings use solar water heating systems, and there are still many problems and difficulties in the combination of buildings and systems. However, with the rapid increase in the number of high-rise residential buildings, the combination of solar water heating systems and high-rise residential buildings has become the key to whether solar water heating systems can be widely promoted in cities in the future. Based on the purpose of realizing the large-scale promotion and application of solar water heating system in urban residences, especially to solve the difficult problem of combining with high-rise residential buildings, summarize the appropriate technology and measures for the combination of solar water heating system and high-rise residential buildings to realize the large-scale promotion and application of solar water heating system.