In recent years, ground source heat pumps have been widely used and rapidly developed, exposing many serious and even irreversible problems. Some systems use surface water but freeze, reducing energy efficiency or shutting down completely. In response to these problems, the industry has proposed the concept of system integration innovation. The principle is very simple, that is, the use of new technologies, new systems to transform traditional ground source heat pump systems, or the integration of new technologies, new systems and traditional technical elements, can be called integrated heat pump air conditioning systems, composite ground source heat pump systems or hybrid systems. The diversity of heat sources is a fundamental issue in this process. Heat pumps have a variety of heat sources with different characteristics. How to integrate these heat sources, give full play to their advantages, and combine them into new heat sources to improve the operating characteristics and accuracy of heat pumps is the current direction of the industry. The author believes that the following models are worth learning:
Ground source heat pump multi-energy integrated system, new direction of industry development.
First, a buried ground surface water composite ground source heat pump system. Surface water is more optimistic in some areas, especially in southern cities, but low water temperatures in winter are also a common problem, often below 4°C in hot summer and cold winters. The series buried pipe and the surface water integrated system (dual heat source system) are adopted. When the water temperature is low in winter, the buried pipe is cooled down in the interior of the unit, then enters the buried pipe, and then returns to the unit after heat exchange, so that the surface of the unit Both water and soil have heat, which reduces the surface temperature of the unit. It should be noted that when the local surface water temperature is high, the buried pipeline should be closed to make it a single surface water source heat pump system. However, the local surface water temperature is normal but the water volume is not much, and corresponding countermeasures are needed.
Ground source heat pump
Second, the buried tube solar composite ground source heat pump system. As we all know, solar energy is an inexhaustible, inefficient and clean energy source. It is the most promising energy source after the 21st century. But solar energy is also an “unstable” category. At present, two-thirds of China’s annual sunshine hours exceed 2000 hours, taking into account unsafe and unreliable factors, such as cloudy and cloudy nights, making it possible to form a composite system of buried pipelines and solar energy. From the point of view of heating safety, buried pipelines must be designed at full load to meet the most unfavorable conditions. At the same time, considering that solar energy is entirely economic, we must prioritize the use of solar energy and make full use of solar energy in integrated systems. For safety and economy, we need to consider and solve problems from the operating model.
Third, the composite system of groundwater and seawater source heat pump. Some ports and islands in China are rich in sea water resources. The summer water temperature is usually between 20 °C and 30 °C, which is an ideal source of cooling water. In winter, the water temperature in some waters drops to 0, 13 ° C, even on the surface. In this case, Kolding uses the joint operation mode of groundwater and seawater source heat pump to make full use of seawater resources to ensure the stability and safety of the system. Fourth, indoor residual heat can be used as a resource, that is, water ring heat pump energy-saving equipment. The project should combine solar energy, water, air and soil into the energy source. If this energy is low, the corresponding heat pump system can be introduced to replace the auxiliary heating boiler, the solar water energy equipment or the well water source heat pump water link. Compound operation mode of equipment, soil source heat pump water ring heat pump energy-saving equipment, air source water loop heat pump energy-saving equipment.
The fourth is a buried tube heat pump ice storage heat pump system. In a heat exchanger project in Beijing, according to the winter heating load, because the heating load of the air conditioner is greater than the load, it is difficult to meet the operational demand in summer. This difference is only solved by the ice storage system, not only for the grid resources. By the positive role of cutting peaks and filling valleys, users also enjoy the preferential price of electricity and reduce operating costs. The sixth is the soil cold storage cold soil heat pump coupling integrated system. The idea combines the cold storage device with the heat pump underground heat sink, and realizes the integrated system function of heat pump, cold storage and air conditioner through the chiller. Although this composite model is the original innovation of cold storage air conditioners, it faces many problems, including simulation links, cold storage thermal characteristics, soil overflow processes and cooling loss, which need to be studied carefully. In addition, there are innovative composite modes, such as natural cooling buried tube heat pump systems and split air conditioning hot water supply energy saving equipment. In particular, the latter has been commercialized, but many details still need to be discussed, and failure to fully resolve will affect its development.
Multi-energy integrated system
In short, scientific and rational development is the key to the healthy development of the ground source heat pump industry. The rise of the ground source heat pump market is a “double-edged sword”. We should have four points to know about this: First, the form of composite heat pump energy-saving equipment is diverse, and different system forms should be proposed according to different integration innovation goals. Second, institutional innovation to promote the development of ground source heat pumps must be organically combined, rather than mechanically piece together. At present, there are quite a few projects that have been “combined”, and we should pay close attention to them, especially low-quality projects for the purpose of certain policy subsidies. Secondly, innovation should start with the project and save energy and save money as the basic principle. It is impossible to save energy without saving money, and it is impossible to save energy without saving money. Finally, the simulation and predictive analysis of the hybrid system should be strengthened, and the development of the automatic control system should be strengthened to promote the maturity of the hybrid system.
Post time: Aug-06-2019