Ground source heat pump air conditioning system introduction

First, the concept

Ground source heat pump is a use of underground shallow geothermal resources (also known as energy, including groundwater, soil or surface water, etc.) can be both heating and cooling of energy efficient air-conditioning system. Ground source heat pump by entering a small amount of high-grade energy (such as electricity), to achieve low-temperature heat transfer to high temperature. In winter, respectively, as a heat pump heat source and the summer air-conditioning cold source, that is, in winter, the heat to "take out" to increase the temperature, the supply of indoor heating; Summer, the indoor heat removed, release Go down to the ground. Usually source heat pump consumes 1kW of energy, users can get more than 4kW of heat or cold. Compared with the boiler (electricity, fuel) heating system, the boiler heating only 90% of the energy or 70 ~ 90% of the fuel can be heat for the user, so the ground source heat pump than the electric boiler heating save More than two-thirds of the energy, compared with the fuel boiler to save about one-half of the energy; due to ground source heat pump heat source temperature is relatively stable throughout the year, usually 10 ~ 25 ℃, the cooling, heating coefficient of up to 4.0 ~ 4.4 , Compared with the traditional air source heat pump, to about 40% higher, the operating costs for the ordinary central air-conditioning 50 to 60%. Therefore, over the past decade or so, especially in the past five years, ground-source heat pump air-conditioning systems have enjoyed rapid development in North America such as the United States, Canada, Central and Northern Europe such as Switzerland and Sweden, and the geothermal market in China has also become increasingly active It can be predicted that this technology will be the most effective heating and cooling air-conditioning technology in the 21st century.

Second, the development of ground source heat pump at home and abroad

Ground-source heat pump history can be traced back to a patent in Switzerland in 1912, and the true significance of commercial applications of ground-source heat pump only 10 years of history. 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 the total air-conditioning capacity in 1998, of which 30% were new buildings. The United States ground-source heat pump industry has set up by the United States Department of Energy, Environmental Protection Agency, Edison Institute of Power and many ground-source heat pump manufacturers, the United States ground source heat pump Association, the Association in recent years will invest 100 million US dollars in development, research And promotion work. The United States plans to achieve the goal of installing 400,000 ground-source heat pumps per year by 2001, reducing greenhouse gas emissions by 1 million tons, which is equivalent to reducing pollutant emissions by 500,000 vehicles or planting 1 million acres of trees annually to save energy costs Reaching 420 million U.S. dollars. Since then, the annual cost of energy conservation has been increased by 170 million U.S. dollars. 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. The United States is particularly optimistic about the Chinese 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 launched in Beijing, China , Hangzhou and Guangzhou to build a commercial building using ground source heat pump heating and air conditioning to promote the use of this "green technology" to ease China's reliance on coal and oil so as to achieve the diversification of energy resources. At the same time, the Chinese enterprise commissioned by the Ministry of Science and Technology will introduce ground source heat pump technology and equipment from the United States to the Chinese market, which will promote the market-oriented and industrialized development of ground-source heat pumps in China and will make the research and development of ground-source heat pumps in China as soon as possible Keep up with the international trend. In recent years, the ground-source heat pump industry in our country has started to take off and its momentum of development is promising. Tianjin University, Tsinghua University, respectively, with the formation of industry-academia-industry research consortium to develop a Chinese brand of ground-source heat pump system, has built a number of demonstration projects, more and more Chinese users are familiar with ground-source heat pump, and its application A strong interest can be expected in China's ground-source heat pump market prospects.

Third, the characteristics of ground source heat pump

1, is a renewable energy technology

Ground source heat pump is the use of the Earth's surface shallow geothermal resources (usually less than 400 meters deep) as a cold source of heat for energy conversion heating and air conditioning system. Surface shallow geothermal resources can be called geothermal energy, refers to the surface soil, groundwater or rivers, lakes absorb solar energy, geothermal energy and low-lying latent heat. The superficial surface of the earth is a giant solar collector that collects 47% of the sun's energy, more than 500 times the amount of energy a person uses annually. It is not subject to geographical, resource constraints, the real amount is widespread, ubiquitous. This near-infinite renewable energy stored in the shallow superficial earth makes geotech a clean, renewable form of energy.

2, is a cost-effective energy-saving technology

The geothermal energy of geothermal energy or shallow ground surface is relatively stable all year round, the temperature in winter is higher than the ambient air temperature, and the temperature in summer is lower than the ambient air temperature. It is a good source of heat pump and air conditioner. This temperature characteristic makes the geothermal heat pump ratio Traditional air-conditioning system to run 40% higher efficiency, so to save energy and save about 40% of operating costs. In addition, the relatively constant temperature to the nature of the characteristics of the heat pump makes the operation more reliable and stable, but also to ensure system efficiency and economy. Design and installation of a good ground source heat pump, on average, users can save 30 to 40% of the heating and cooling air conditioning operating costs.

3, significant environmental benefits

The system operates without any pollution and can be built in residential areas. There is no burning, no smoke emission and no waste. There is no need to store fuel waste and do not need to transport heat over long distances.

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

Ground 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 conditioning two sets of devices or systems; can be applied to hotels, shopping malls, office buildings, schools and other buildings , More suitable for heating residential villa, air conditioning. In addition, the long life of the unit, are more than 15 years; unit compact, space-saving; low maintenance costs; a high degree of automatic control, unattended.

Fourth, heat pump classification

Heat pump is the need for the heat of the condenser, the evaporator heat from the environment, this time from the environment to heat the object is called the heat; the opposite is the need to cool the evaporator, the condenser heat to the environment, this time The object of environmental heat release is called cold source. Evaporator condenser according to the circulating refrigerant and the environment of the heat transfer medium is divided into two main forms of air heat exchange and water heat exchange. This heat pump or refrigerator according to the environment and the heat transfer medium can be divided into water - water, water - air, air - water, and air - air four categories. The use of air as a heat source heat pump, called the air source heat pump. Air source heat pump has a long history, and its installation and use are very convenient, widely used. However, due to the difference of regional air temperature, the typical application in our country is south of the Yangtze River. In North China, the mean temperature in winter is below zero degrees Celsius. Air source heat pumps are not only run in poor conditions and have poor stability, but also are inefficient because of frost formation. The use of water as a heat source heat pump, called water source heat pump. Water is an excellent heat source. Its heat capacity is large and its heat transfer performance is good. Generally, the efficiency and capacity of cooling and heating of water source heat pump are higher than that of air source heat pump. However, the application of water source heat pump is much less than that of air source heat pump due to the limitation of water source.

Fifth, ground source heat pump working principle

Ground source heat pump is a form of water source heat pump, it is the use of water and ground energy (groundwater, soil or surface water) for cold and heat exchange as a source of heat and cold water source heat pump in winter to heat "Come out to supply indoor heating, at this time can be a" heat source "; summer to remove indoor heat, released into the groundwater, soil or surface water, at this time can be" cold source. "

Ground source heat pump heating air conditioning system is divided into three parts: outdoor heat exchange system, water source heat pump units and indoor heating air conditioning terminal system. Water source heat pump which there are two main forms: water - water or water - air type. Between the three systems by water or air heat transfer medium for heat transfer, water source heat pump and ground heat exchanger medium is water, and building heating and air conditioning at the end of the heat transfer medium can be water or air.

Ground Source Heat Pump Compared with air source heat pump, there are many advantages:

(1) Small temperature fluctuations throughout the year. Winter temperature is higher than the air temperature, summer air temperature is lower than the ground, so the ground source heat pump heating, cooling factor is higher than the air source heat pump, generally higher than 40%, so energy saving and cost savings of about 40%.

(2) Winter operation does not require defrosting, reducing frost and defrosting losses.

(3) ground source has a better energy storage effect.

Sixth, the source classification

Ground source in accordance with the different ways of outdoor heat exchange can be divided into three categories: 1. Soil buried coil system, 2. Groundwater system, 3. Surface water system.

According to whether the circulating water is a closed system, the ground can be divided into closed-loop and open-loop system.

Closed-loop systems such as buried coil (vertical or horizontal buried pipe), surface water to place the heat exchanger. Open-loop systems such as pumping groundwater or surface water.

Seven, ground source heat pump application

Ground source heat pump applications from the application of building objects can be divided into two major categories of domestic and commercial, from the transport of cold and heat can be divided into centralized systems, decentralized systems and hybrid systems.

1, home system

Users use their own heat pump, ground and water or duct delivery system for hot and cold supply, and more for small houses, villas and other household air-conditioning.

2, centralized system

Heat pump is arranged in the engine room, hot and cold concentrated through the air duct or water distribution system to each room.

3, decentralized system

Users use their own heat pump unit to regulate air alone. Generally used in office buildings, schools, commercial buildings, etc., this system can be fully used in the user's cold and heat on the electricity, easy to measure, suitable for the current independent heat measurement requirements.

4, mixed system:

A system that uses a combination of ground sources and cooling towers or boilers as a source of heat and cooling, the hybrid system is very similar to a decentralized system except that cooling towers or boilers are added to the cold or hot source system.

In the south, the cooling load is large and the heat load is low. It is suitable for the combined use of ground source and cooling tower in summer and only the ground source in winter. In the north, the heat load is large and the cooling load is low. In winter, it is suitable for the combined use of ground sources and boilers. In summer, only the ground source is used. This will reduce the capacity and size of the ground source and save on investment. Dispersing systems or hybrid systems are essentially water ring heat pump air conditioning systems.

Frequently Asked Questions

1. Why the ground source heat pump in the United States, Europe and China, especially in recent years for more and more users recognize that the market is increasingly active?

On the one hand, the issue of energy, environment and sustainable development is paying more attention to than ever before in the world. For China, because coal-based energy structure has caused extremely serious air pollution, therefore, to achieve economic sustainability Development, we must make full use of clean renewable energy, we must increase the intensity of energy conservation, and both in winter heating, but also in the ground air-conditioning heat pump system in summer is a good choice; the other is Ground-source heat pump system after years of research, technically very mature, and after years of demonstration and practice, confirmed the many advantages of ground source heat pump system: save energy, comfort, safety, stable performance, clean, flexible use.

2. Comments on Several Ground Source Heat Pump Systems in Engineering Applications

1) Ground source heat pump system that directly utilizes underground well water: its biggest advantage is that it is very economical and covers a small area. However, it must be noted that the following conditions must be met: good water quality, abundant water content, and compliance with standards.

2) Ground-source heat pump system buried underground: For the vertical buried pipe system, its advantages are: smaller land occupation, pipeline and pump power less, the disadvantage is the higher drilling costs; for horizontal buried pipe system The advantages are: installation costs lower than the vertical buried pipe system, widely used, the user easy to grasp, the disadvantages are: large area, affected by the ground temperature, the pump power consumption.

3) Surface water heat pump: Direct cooling of 10 ° C is provided in a lake of 10 meters or deeper, which is less investment than underground buried pipe systems, low energy consumption of pumps, high reliability, low maintenance requirements and low operating costs In warm areas, the lake can be used as heat source.

3. Ground source heat pump operating costs how? How economical?

This is the user's most concerned about, but also the most likely to raise a question, however, is also the most difficult to answer a question. This is because there are many factors that affect the economy of ground source heat pumps, such as electricity rates, user or resident behavior, climatic conditions, and other factors such as unusual hot or cold seasons. Especially in China, the application time is not long, the actual operation of the economy to conclude the work yet to be completed, at present, it is difficult to give more accurate answers. As the developed countries such as the United States have at least a dozen years of history in the engineering application of ground source heat pumps, they may wish to learn from their experience first. According to EPA's EPA report on the future of air conditioning, ground-source heat pump technology, while providing comfort, reliability and energy efficiency to households, will be a major source of energy consumption and environmental pollution reductions in the country power. According to EPA estimates, designing and installing a good ground-source heat pump can, on average, save 30-40% of the operating costs of heating and cooling air-conditioners.