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Advantages and disadvantages of water source heat pump and ground source heat pump


1. Introduction to deep well technology of water source heat pump

1. Principle of water source heat pump

Groundwater is a huge natural resource with great thermal inertia and little temperature fluctuations throughout the year. Generally speaking, the shallow groundwater buried below 20M above the ground can be maintained at about the annual average temperature of the area throughout the year. It is an ideal natural resource. Source of cold and heat. The water source heat pump system is a new type of energy-saving air conditioner that uses the characteristics of groundwater to work. In the water source heat pump water well system, the water source heat pump generally has a well depth of 50 meters to 300 meters. Because this part of the groundwater is mainly supplied by surface water and is not suitable for drinking, it is an excellent choice for water source heat pump central air conditioning systems. It is composed of three parts: the terminal (indoor air treatment terminal, etc.) system, the water source central air conditioning main unit (also known as the water source heat pump) system and the water source water system. When supplying heat to users, the water-source central air-conditioning system extracts low-grade heat energy from the water source and "pumps" it to a high-temperature heat source through the electric-powered water-source central air-conditioning main unit (heat pump) to meet the user's heating needs. When cooling users, the water-source central air conditioner transfers the waste heat in the user's room to the water source through the water-source central air-conditioning host (refrigeration) to meet the user's cooling needs.

1.1 System principle diagram: Take heating mode as an example (refrigeration mode can be realized by switching the valve, even if the water source water enters the condenser, the refrigerating cycle water of the evaporator is connected to the user system).

Water source heat pumps can be divided into closed systems and open systems according to different ways of using water sources.

Closed system refers to a set of closed-loop heat exchange sleeves on the water side. The set of sleeves are generally buried horizontally or vertically in the ground or in lake water and seawater to achieve energy transfer by exchanging heat with soil or seawater.

The open system is also known as the deep well recharge water source heat pump system. Groundwater is pumped out through the construction of pumping wells, and then sent to the water source heat pump unit through secondary heat exchange or directly. After the heat is extracted or released, it is returned to the ground from the recharge wells.

Advantages of water source heat pump

2.1 High efficiency and energy saving

The water source heat pump is currently the cooling and heating method with the highest energy efficiency ratio (COP value) in the air conditioning system. The theoretical calculation can reach 7 and the actual operation is 4-6.

The usable water temperature of the water source heat pump unit is 12~22℃ in winter, and the water temperature is higher than the ambient air temperature. Therefore, the evaporation temperature of the heat pump cycle is increased, and the energy efficiency ratio is also improved. In summer, the water temperature is 18~35℃, and the water temperature is lower than the ambient air temperature, so the condensing temperature of refrigeration is lowered, which makes the cooling effect better than air-cooled and cooling towers, thereby improving the operating efficiency of the unit. The water source heat pump consumes 1kW.h of electricity, and users can get 4.3~5.0kW.h of heat or 5.4~6.2kW.h of cooling. Compared with air source heat pump, its operating efficiency is 20° higher

60%, the operating cost is only 40~60% of the ordinary central air conditioner.

2.2 Renewable energy utilization technology

The water source heat pump is a heating and air conditioning system that uses the solar energy stored in the earth's water body as a cold and heat source for energy conversion. The water bodies that can be used include groundwater or rivers, rivers and lakes on the surface, and the ocean. The surface soil and water body is not only a huge solar collector, collecting 47% of solar radiation energy, which is more than 500 times the energy used by humans every year (the underground water body receives solar radiation energy indirectly through the soil), but also A huge dynamic energy balance system, the soil and water on the surface naturally maintain a relative balance of energy reception and emission. This makes it possible to use the nearly unlimited solar or ground energy stored in it. Therefore, the water source heat pump uses a technology of clean renewable energy.

2.3 Water and land saving

Using surface water as a source of cold and heat, it releases or absorbs heat, does not consume water resources, and does not cause pollution; it eliminates the need for boiler rooms and auxiliary coal yards, oil storage rooms, cooling towers and other facilities, and the area of the computer room is large It is smaller than a conventional air-conditioning system, which saves building space and is also conducive to the beauty of the building.

2.4 Significant environmental benefits

The water source heat pump unit eliminates the need for coal, gas, oil and other boiler room systems for heating, no combustion process, and avoids pollution such as smoke and sewage; when cooling, it eliminates the cooling water tower and avoids the noise of the cooling tower. Mold contamination and water consumption. Therefore, the water source heat pump unit has no pollution, no combustion, no smoke, no waste residue, waste water, exhaust gas and soot, and no urban heat island effect. It is very environmentally friendly and is an ideal green product.

2.5 One machine with multiple functions, wide application range

The water source heat pump system can be used for heating, air-conditioning, and domestic hot water. One machine has multiple functions. One system can replace the original two sets of boilers and air-conditioning devices or systems. Especially for buildings that have both heating and cooling requirements, water source heat pumps have obvious advantages. It not only saves a lot of energy, but also can meet the requirements of heating and cooling at the same time with a set of equipment, reducing the initial investment of equipment. Its total investment is only 60% of the traditional air-conditioning system, and it is easy to install, the installation workload is less than that of the traditional air-conditioning system, the installation period is short, and it is easy to change the installation.

Water source heat pumps can be used in hotels, shopping malls, office buildings, schools and other buildings. Small water source heat pumps are more suitable for heating and cooling in villas and residential quarters.

2.6 Stable and reliable operation, convenient maintenance

The temperature of the water body is relatively stable throughout the year, and the range of its fluctuation is much smaller than that of the air. The constant temperature of the water body makes the operation of the heat pump unit more reliable and stable, and also ensures the efficiency and economy of the system; it adopts a full computer Control and high degree of automation. Due to the simple system, few parts of the unit and stable operation, the maintenance cost is low and the service life is long.

2.7 Comply with national policies and obtain policy support. The country attaches great importance to the development and utilization of renewable energy. The "Renewable Energy Law of the People's Republic of China" has been implemented on January 1, 2006; In the "Planning Outline", vigorous development and large-scale application of new energy and renewable energy are also the priority development themes in the energy field. From the height of national legislation and development strategy, the development and application of renewable energy should be strongly promoted.

A few days ago, the Ministry of Finance and the Ministry of Construction issued a document "Implementation Opinions on Promoting the Application of Renewable Energy in Buildings" and "Interim Measures for the Management of Special Funds for the Application of Renewable Energy in Buildings." The area accounts for more than 25% of the newly built building area. By 2020, the renewable energy application area will account for more than 50% of the newly built building area. This provides a good environment and strong motivation for the development of water source heat pumps in my country.

3. Application restrictions of water source heat pump:

3.1 Restrictions on available water source conditions

In theory, water source heat pumps can use all water resources, but in actual projects, the cost of using different water resources varies greatly. Therefore, whether there are suitable water sources in different areas has become a key to the application of water source heat pumps. Among the current water source heat pump utilization methods, the closed system generally has a higher cost. In the open system, whether a suitable water source can be found has become a limiting condition for the use of water source heat pumps. For the split system, the water source requirements must meet a certain temperature, water volume and cleanliness.

3.2 Limitations of the geographical structure of the water layer

For the use of pumping water back and forth from the ground, the geological structure of the place of use must be taken into consideration to ensure that a suitable water source can be found by drilling wells under economic conditions. At the same time, the local geology should also be considered.

And the conditions of the soil ensure that the recharge of the tail water after use can be realized.

3.3 Economics of investment

Due to the impact of different regions, different users, national energy policies, and fuel prices, the basic conditions of water sources are different; one-time investment and operating costs will vary from user to user. Although in general, water source heat pumps have higher operating efficiency and lower costs. However, compared with traditional air-conditioning, cooling and heating methods, the investment economy of water source heat pumps will be different under the conditions of different needs in different regions.