Water source heat pump system introduction

Abstract: This paper first introduces the concept and working principle of water source heat pump technology, compares it with that of boiler and air source heat pump, and draws a conclusion that water source heat pump technology is a technology that makes use of renewable energy. Subsequently, the characteristics of water source heat pump are described in detail and the basic situation of application of ground source at home and abroad and the prospects of development and application of water source heat pump in China are introduced. Finally, the technical characteristics of Tsinghua Tongfang water source heat pump and the popularization and application of water source heat pump in China Some of the problems.

First, the concept of water source heat pump technology and working principle

Water source heat pump technology is the use of shallow surface water on the surface of the earth such as groundwater, rivers and lakes in the absorption of solar and geothermal energy to form low-temperature low heat resources and the use of heat pump principle, through a small amount of high energy input, low heat to high energy transfer A kind of technology.

The shallow surface of the Earth's surface water, such as groundwater, surface rivers and lakes and oceans at depths of less than 1,000 meters, absorbs considerable solar radiation into the Earth's radiant energy, and the water temperature is generally very stable. The principle of water source heat pump unit is to transfer the heat in the building to the water source in the summer. Because of the low temperature of the water source, the heat can be efficiently taken away, and in winter, the energy is extracted from the water source by the heat pump principle by air or water Refrigerant to the building after raising the temperature. Usually water source heat pump consumes 1kW of energy, users can get more than 4kW of heat or cold.

Water source heat pump according to the different ways of using water can be divided into two kinds of closed system and open system. Closed system refers to the water side of a group of closed loop heat transfer casing, the casing is generally buried horizontally or vertically in the sea water or seawater, through the heat transfer with the soil or seawater to achieve energy transfer. (Which buried in the soil system, also known as ground-source heat pump, buried in the sea water system, also known as seawater source heat pump). Open system refers to the system that discharges directly from the underground pumping water or surface water through the heat exchanger.

Water-source heat pumps have significant advantages over heating systems for boilers (electricity, fuel) and air-source heat pumps. Boiler heating can only 90% ~ 98% of the electric energy or 70 ~ 90% of the fuel can be converted into heat for the user, so ground-source heat pump than electric boiler heating to save more than two-thirds of the energy than fuel The boiler saves more than one-half of the energy. Since the heat source temperature of the water source heat pump is relatively stable throughout the year, the temperature of the heat source of the water source heat pump is generally 10-25 ° C, and the cooling and heating coefficient can reach 3.5-4.4. Compared with the conventional air source heat pump Higher than about 40%, its operating costs for the ordinary central air-conditioning 50 to 60%. Therefore, over the past decade or so, especially in the past five years, water source heat pump air conditioning systems have achieved rapid development in North America such as the United States, Canada, Central and Northern Europe such as Switzerland and Sweden, and the water source heat pump market in China has also become increasingly active. The technology is expected to be the most effective heating and cooling air-conditioning technology in the 21st century.

In China's traditional concept of air-conditioning systems, due to the country's economic development and policies, the north generally solves winter heating problems with coal-fired boilers for a long period of time and water cooling units in the south address summer cooling issues. After 1980s, the way of refrigeration units began to diversify. At this moment, lithium bromide units and air-cooled units appeared. The capacities of units also changed from large and medium-sized units to large, medium and large units, Since the 1990s, new attempts and discussions have been made on heating methods. In particular, with the promotion of sustainable development and public awareness of environmental protection, the structure of energy use in both the world and China is changing. From the existing coal and oil Heating transition to natural gas and electricity and other clean energy. As one of the cities with the most serious air pollution, Beijing's policy on the control of air pollution includes the adjustment of the energy structure. From coal to natural gas and electricity to alternative sources of energy. However, although alternative energy sources can partially solve the problem of air pollution, natural gas and petroleum are non-renewable energy sources. From a sustainable development point of view, it is necessary to improve energy efficiency or find renewable energy sources. However, water-source heat pump units are An ideal device.

Second, the characteristics of water source heat pump

As the water source heat pump technology uses surface water as the air conditioning unit cooling and heating source, so it has the following advantages:

1, is a renewable energy technology

Water source heat pump is the use of the Earth's water storage of solar energy resources as a source of cold and heat, energy conversion heating and air conditioning system. Among the available water bodies are groundwater or rivers, rivers and lakes that are part of the surface, and oceans. Surface soil and water bodies are not only huge solar collectors that collect 47% of the solar radiation energy, more than 500 times the amount of energy used annually by human beings (underground water bodies receive indirect solar radiation energy through the soil) and are A huge dynamic energy balance system, the soil and water on the surface naturally maintain the relative balance of energy acceptance and divergence. This makes it possible to utilize almost infinite solar energy or earth stored therein. So, a water source heat pump uses a technology that is clean and renewable.

2, high efficiency and energy saving

Water source heat pump units available water temperature in winter is 12 ~ 22 ℃, the water temperature is higher than the ambient air temperature, so the heat pump cycle evaporation temperature increases, the energy efficiency ratio also increased. The summer water body is 18-35 ° C, and the temperature of the water body is lower than the ambient air temperature. Therefore, the condensation temperature of the cooling decreases, making the cooling effect better than that of the air-cooling and cooling towers, and the unit efficiency is improved. According to the EPA of the United States Environmental Protection Agency, the design and installation of a good water source heat pump can save 30-40% of the heating and cooling air-conditioners on average.

3, stable and reliable operation

The temperature of water body is relatively stable throughout the year, the range of its fluctuation is far less than the change of air. Is a very good heat pump heat source and air conditioning cold source, water temperature is more constant characteristics, making the heat pump operation more reliable and stable, but also to ensure the system's efficiency and economy. There is no air source heat pump in winter defrost and other difficult issues.

4, significant environmental benefits

Water source heat pumps use electricity, which itself is a clean source of energy, but consumes primary energy and generates emissions of greenhouse gases such as pollutants and carbon dioxide when generating electricity. Therefore, the pollution of energy-saving equipment itself is small. The power consumption of well-designed water-source heat pump units is equivalent to a reduction of more than 30% compared to air-source heat pumps, which is equivalent to a reduction of more than 70% when compared to electric heating.

Water source heat pump technology used by the refrigerant, can be R22 or R134A, R407C and R410A alternatives such as co-quality.

Water source heat pump units operate without any pollution and can be built in residential areas without burning, without fumes or with waste, without the need to stack fuel waste and without the heat from long distances.

5, a multi-purpose machine, wide range of applications

Water source heat pump system can be heating, air conditioning, but also for domestic hot water, a multi-purpose machine, a system that can replace the original boiler plus air-conditioned two sets of devices or systems. Especially for buildings with both heating and cooling requirements, water-source heat pumps have obvious advantages. Not only saves a lot of energy, but also with a set of equipment to meet both heating and cooling requirements, reducing the initial investment of equipment. Water source heat pump can be applied to hotels, shopping malls, office buildings, schools and other buildings, small water source heat pump is more suitable for residential heating, air conditioning.

6, automatic operation

Water source heat pump unit because of stable conditions, so you can design a simple system, fewer components, simple and reliable unit operation, low maintenance costs; a high degree of automatic control, the service life of up to 15 years.

Of course, like any thing, water source heat pump is not perfect, its application will be constrained.

â‘´, available water conditions

Water source heat pump theory can make use of all the water resources, in fact, in actual projects, the cost difference of different water resources utilization is quite large. So in different regions whether there is a suitable water source heat pump applications become a key. The current water source heat pump use, the closed system is generally higher cost. The open system, can find the right water to become a source of heat pump restrictions. On the open system, water requirements must meet a certain temperature, water and cleanliness.
⑵, the geographical limitations of the water layer

For the use of underground pumping backwaters, the geologic structure of the site to be used must be taken into account to ensure that wells can be drilled economically to find a suitable source of water, taking into account local geological and soil conditions and ensuring that the tail water after use Recharge can be achieved.

⑶, investment economy

Due to different regions, different users and the country's energy policy, the impact of fuel prices, the basic conditions of water is different; one-time investment and operating costs will vary with the user. Although, on the whole, water-source heat pumps operate at a higher cost and with lower costs, However, compared with the traditional air-conditioning and cooling heating methods, the water-source heat pump investment economy will be different under different requirements of different regions.

Third, domestic and international water source heat pump development and characteristics

Abroad, the study on water source heat pump belongs to two kinds of heat pump system: one is ground source heat pump, one is seawater heat pump. One of the real significance of commercial applications of ground source heat pump only a few years history, but the development is quite rapid. For example, in the United States, there were 14,000 ground-source heat pumps in the country as of 1985, up from 45,000 in 1997 and 400,000 already so far, with steady growth of 10% annually. Ground-source heat pump systems in commercial buildings in the United States accounted for 19% of total air-conditioning capacity in 1998, of which 30% were new construction. The ground-source heat pump industry in the United States has been created by the Energy & Environmental Research Center, the National Ground Water Association, the Edison Electric Institute and numerous ground-source heat pump designs Sales companies and government agencies and builders of 146 members of the United States ground source heat pump Association, which in recent years will invest 100 million US dollars in development, research and promotion work. The United States plans to reach the target of installing 400,000 ground-source heat pumps per year by 2001, of which 15% will be water-source heat pumps, which will reduce greenhouse gas emissions by 1 million tons, equivalent to a reduction of 500,000 vehicle pollutants or planting trees1 One million acres, the annual energy savings of 420 million US dollars, thereafter, the annual cost of energy savings increased by 170 million US dollars.

Well-known American manufacturers of water source heat pumps are Addison Products Company, Advanced Geothermal Technology, Carrier Corporation, ClimateMaster Inc., Econar Energy Systems Corporation, FHP Manufacturing, Mammoth Inc., The Trane Company, Water Furnace International and others. US water source heat pump research and application of more focused on residential and commercial small systems (20RT below), the use of water-air systems, such as the well-known TRANE and other products. In large buildings, the United States to promote WLHP system, the water ring heat pump system.

Unlike the development of ground-source heat pumps in the United States, the ground-source heat pumps in Central and Northern Europe such as Sweden, Switzerland, Austria, Germany and other countries mainly make use of shallow geothermal resources, buried underground soil coils (buried depths <400 m deep) In the indoor radiant floor heating and provide hot water. According to the statistics of 1999, the proportion of GSHPs in domestic heating installations is 96% in Switzerland, 38% in Austria and 27% in Denmark. At the same time, the Central and Northern Europe sea water source heat pump research and application are more.

As early as the 1950s, China tried to extract groundwater by means of summer-winter irrigation in Shanghai and Tianjin. Prof. Lucan Can of Tianjin University conducted the earliest research on heat pumps in China. In 1965, it successfully developed the first water-cooled Heat pump air conditioner. At present, many domestic universities and research institutes such as Tsinghua University, Tianjin University, Chongqing University of Architecture, Tianjin Business School and Guangzhou Institute of Energy, Chinese Academy of Sciences are studying water source heat pumps. Among them, Tsinghua University has made achievements in industrialization after many years of research on water pumps with multiple working conditions and has built a number of demonstration projects.

Domestic water source heat pump manufacturers in Tsinghua Tongfang artificial environment equipment company, Shandong Haiyang Fulda is a relatively early water source heat pump manufacturers, but there are quite a number of refrigeration and air conditioning manufacturers to transform their ordinary water-cooled units into water source heat pump. China's water source heat pump research and application has just started, compared with foreign countries, there is a big gap in the optimal design of heat pump units and engineering applications.

At present, the world is particularly optimistic about China's market. The U.S. Department of Energy and Ministry of Science and Technology of China signed the Protocol on Cooperation on Energy Efficiency and Renewable Energy between China and the United States in November 1997. One of the major contents is the "Ground Source Heat Pump", which is planned to be implemented in Beijing, Hangzhou and Guangzhou in China The city built a ground-source heat pump heating and air conditioning commercial buildings to promote the use of this "green technology" to ease China's reliance on coal and oil, so as to achieve the purpose of diversifying energy resources. Allegedly "Huating Jiayuan" is the application of this project. June 2000 June 19 to 23 in Beijing by the National Science and Technology High-tech Development and Industrialization Division held a Sino-US geothermal pump technology conference, the theme of the meeting is "to provide the use of geothermal pump technology for residential quarters or public buildings, heating and cooling , Energy-saving solutions that significantly reduce operating costs ".

In the coming years, China faces enormous energy pressure. On the one hand, China's economy needs to maintain its rapid growth. On the other hand, it must also consider environmental protection and sustainable development. Therefore, it is required to improve the efficiency of energy utilization and require the adjustment of energy structure. The improvement of energy efficiency will encourage the popularization of various energy-saving equipment and technologies. The direction of energy structure adjustment will shift from coal-based gas to gas-based electricity. In China's energy consumption, the proportion of building energy consumption is quite high. In order to meet market requirements and participate in international competition, we must accelerate the industrialization of water-heat pump research and development in China.

Fourth, Tsinghua Tongfang water source heat pump technical characteristics

Tsinghua Tongfang developed water source heat pump unit is designed for large and medium-sized buildings can be achieved modular combination of water - water heat pump units. Groundwater and rivers and lakes, as well as geothermal tailings, can be utilized. For different water sources, whether through the installation of intermediate heat exchanger to form a closed or open system. The hot and cold switching of the unit at work can be achieved by switching the piping of the water system, and the fluorine system remains stable.

According to the research on refrigeration compressors and market forecast, the planned water source heat pump includes 4 kinds of specifications: GHP300, GHP500, GHP600 and GHP1000. Among them, GHP300 and GHP500 are basic modules, which are independent system of 2 compressors and independent system of 3 compressors respectively. GHP600 and GHP100 are combinations of GHP300 and GHP500. GHP300 heat in the standard groundwater heating conditions for the 309KW, in the standard groundwater cooling capacity of 265KW.

Tsinghua Tongfang water source in the product design, the use of the technology route is: use R22 as a refrigerant, the use of sophisticated heat pump technology, taking into account China's actual national conditions, with emphasis on high water temperature and the use of wide temperature, the choice and Determine the compressor operating point and the scope of work, in line with the idea of ​​saving water and energy, the design of large temperature difference of the segmented water heat exchanger. The design of the fluorine system adopts the completely independent modular idea of ​​the subsystem, and the quantity of the system components is small and the quality is excellent. The control system fully takes into account the coordinated and coordinated control of multiple systems and sets up a variety of safety protection while taking into account the pump control and remote operation of the water system.

Tsinghua Tongfang water source heat pump unit in addition to all the features of the traditional water source heat pump, as a system designed for China's national conditions, its notable features are:

1, hot water temperature is high

We provide the water source heat pump in the standard conditions, to ensure that the water temperature is stable at 52 ℃, in the test and the actual use of the user, had done 56 ℃ running experiments. Providing high outlet temperature can increase efficiency, reduce the selection capacity of indoor equipment, and ensure indoor thermal comfort.

2, the water side of the water temperature difference, save water resources

When working in the unit, the water inlet and outlet water temperature difference in winter is 7 ℃, while that in summer is 10 ℃. Different from the traditional 5 ℃ temperature difference design, it can save 20% -50% water, and accordingly reduce the cost of water intake (such as drilling well and pump operation). The idea of ​​Mr. Yan Qi Sen had in 1997, "China's refrigeration and air conditioning industry technology development status and prospects" demonstrated.

3, the system optimization is concise, the parts are excellent and reliable

Through the combination of optimized design and independent modules, the final unit system is quite simple and reliable, but the selection of refrigeration components are well-qualified brands in the industry, ensuring reliable operation of the unit.

4, large unit capacity, wide range of applications

Unit designed for the smallest single capacity of 150KW of heat, you can use the open system or closed system, you can use drilling wells recharge groundwater can also increase the use of intermediate heat exchanger water and sea water. Even the geothermal tail water can be used.

5, simple operation, quiet

Owing to the intelligent automatic control, the operation of the unit is rather simple. Due to the highly effective protection and silencing measures, the operation noise of the unit is no longer unacceptable.

Fifth, the current problems in popularization and application of water source heat pump in China

Water source heat pump as a new type of refrigeration heating mode, from a technical point of view, especially heat pump unit point of view should be quite mature, no problem. However, taking into account China's national conditions, as well as water source heat pump refrigeration and heating as a whole system to promote the application, there are still some problems:

1, the use of water policy

At present, in order to protect the limited water resources, China has formulated the "Water Law of the People's Republic of China," and all cities have formulated their own "urban water management regulations." These policies emphasize water approval and water charges. The approval criteria for similar water source heat pump technology does not require, so water source heat pump can easily be limited by the water index. Even though water approval has been adopted, as the water extraction and emission are doubled in some places and the standards of the charges are not harmonized in the whole country, the result may be that the water fee is too high, resulting in insufficient water conservation cost for the operation of the water source heat pump , Water source heat pump economic change investigation.

Therefore, the promotion of water source heat pump requires that the government, from the perspective of sustainable development, take into account all aspects of energy, environment and resources and adjust the policies on the use of water sources and heat pumps to redefine the management and charging of water sources in order to promote its large-scale development.

2, water exploration and mining technology and costs

In China, exploration and mining technologies for water sources, especially urban water sources, should be improved. One of the preconditions for the application of water source heat pumps is that local water sources must be known. In the early stage of using water source heat pumps, the status of water sources must be carried out on the ground Investigate whether there is enough water in the groundwater, whether the amount of water will be sufficient and whether the site is suitable for well drilling and recharge. The exploration and mining technology to improve and reduce costs, will promote the better application of water source heat pump units.

3, groundwater recharge technology

Water source heat pump if the use of groundwater, we must consider the water recharge, for irrigation technology, must be combined with local geological conditions to consider, to re-irrigation technology. We do not know much about the geological structure in different regions, which restricts the popularization and application of water source heat pump units.

4, the overall system design

Water source heat pump system, energy-saving as a system, must consider from all aspects, if the water source heat pump units can do to use more water to provide more energy, but the system design of pumps and other energy-saving equipment improper selection or control, Will also reduce the energy-saving effect of the system. Similarly, if the unit provides high water temperatures, the end of the air-conditioning system being designed has not been properly accounted for and may either degrade the overall system or increase the initial investment in the overall system. Therefore, the popularization and application of water source heat pump needs more professionals in all fields to work together to work together, from government policies, host design and manufacture, system design and operation and management to participate in all aspects.

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