2019年10月29日星期二

Application of water source heat pump in building energy conservation

A groundwater heat pump

Heat pump (refrigerator) is through the work of the heat from the low temperature medium to a medium of high temperature medium. Building air-conditioning system should generally meet the winter heating and summer cooling two opposite requirements. Traditional air-conditioning systems usually require separate sets of cold sources (chillers) and heat sources (boilers). Because of the need to have a cold source (chiller) in a building air conditioning system, boiler and boiler rooms can be eliminated if it is run in heat pump mode in winter, saving not only initial investment, but also the use of clean energy such as electricity throughout the year, Greatly reduce the air pollution caused by heating problems.

The figure below is a typical water (groundwater) heat pump process diagram

Figure 1: water (groundwater) heat pump process diagram

Figure 1 water (groundwater) heat pump process diagram

Schematic diagram of water source (groundwater) heat pump Due to ground source heat pump 70% of the energy from the soil, less energy consumption, the higher thermal efficiency, COP value is generally 3-5, that is, for each consumption of electricity it can release heat 3-5KW

Take the existing project in Beijing as an example:

Heating Air Conditioning Area: 70,000sqm

System water: 10.6t / min

System type


System Type Expense Soil Ground Source Heat Pump Traditional Central Air Conditioning plus Gas Boiler System Unit Price (RMB / sqm) Total Price (RMB'0000) Unit Price (RMB / sqm) Total Price (RMB'0000)
Total Investment Equipment Costs 1533
Project cost 1029
Total 2562
Operating expenses (one year) Heating 12.9 150.1 26.23 266.2
Refrigeration 6.5 11.81
Land cost 2500 31.5 2500 31.5

(Reference Project: China-US Government Renewable Energy Cooperation Project - Beijing Earth-Gas Geogenic Heat Pump Demonstration Project)

Second, the coupling tube system

Figure two: to the coupling tube system

Figure two: to the coupling tube system

The underground coupled heat pump system is a ground-source heat pump system that utilizes the closed circuit of heat in the underground rock. Often referred to as "closed-circuit ground source heat pump" to distinguish it from groundwater heat pump systems or directly as "ground source heat pumps." It is through the circulation of liquid (water or water as the main component of the antifreeze) in the closed underground pipe flow, the system and the ground to achieve heat transfer. The underground coupling heat pump system is structurally characterized by a geothermal heat exchanger (geothermalheatexchanger, or groundheatexchanger) consisting of buried underground pipes. Geothermal heat exchangers are mainly installed in the form of horizontal buried pipe and vertical buried pipe two. Horizontal pipe buried in the form of open 1 to 2 meters deep trench, buried in each groove 2, 4 or 6 plastic pipe. Vertical buried pipe is drilled in the formation of a diameter of 0.1 ~ 0.15m drill hole set in a group (2) or 2 (4) U-shaped pipe filled with filling material. Drilling depth is usually 40 ~ 200m. The available surface area on site is a decisive factor in the choice of the form of the geothermal heat exchanger. Vertical buried geothermal heat exchanger can save a lot of land area than the horizontal buried pipe, so it is more suitable for China's less people and more national conditions.

(Reference project: four-storey building, a total construction area of ​​2070.8m2. Air-conditioning use an area of ​​about 1600m2)

Sea water source heat pump

Sea water source heat pump air conditioning system is gaining more and more attention in many coastal cities in recent years because of its ability to utilize the huge thermal energy resources contained in seawater. Sea water source heat pump air conditioning system is the use of sea water as a heat source or heat sink, and through the heat pump unit, heat medium or cooling refrigerant, and ultimately provide heat or cooling system. The heat energy contained in seawater is a typical renewable energy source. Therefore, the seawater source heat pump air conditioning system is also a kind of utilization mode of renewable energy, which is a green heating air conditioning system with energy conservation and environmental protection.

Advantages of seawater heat pump air conditioning system

Compared with the commonly used methods of setting electric refrigeration units and boiler room hot water heating separately in each building, there are mainly the following advantages:

(1) It can take full advantage of the diversity of user load distribution (ie, not all users reach the peak load at the same time), reducing the total installed capacity of the equipment and reducing their initial investment.

(2) The COP value of a large heat pump unit is higher than that of a small unit, improving the energy utilization efficiency.

(3) Although heat pump units usually still require electricity for cooling / heating, they still have the energy saving advantage because they operate at higher COP values ​​for most of the year.

Figure three sea water source heat pump diagram

Figure 3: Sea water source heat pump diagram

Comprehensive analysis

Groundwater heat pump and ground-coupled system

Ground source heat pump technology is integrated HVAC technology and drilling technology, both indispensable, which requires the project organizer and engineering and technical personnel to be able to reasonably coordinate and do a full technical and economic analysis.
Impact on the Environment: At present, groundwater recharge technology is imperfect, to a certain extent, will affect the further promotion of ground source heat pump with low heat source. In addition, the influence of ground source heat pump air conditioning system drilling on soil heat, humidity and salt migration Research needs to be further deepened, how to minimize the negative factors must be considered.

Initial investment issue: Not all ground-source heat pump systems are cost-effective and some investors may return to traditional forms of air-conditioning as drilling costs may account for more than 50% of initial system-wide investment.

Installation and maintenance: At present, the installation cost of ground source heat pump system is high, compared with 500-800 yuan / ton of electric cooling and natural gas heating system, 600-1000 yuan / ton (1 ton = 1.01605t) of ground source heat pump is obviously High, its payback period is 5 to 8 years; and ground source heat pump system maintenance is more difficult, which to a certain extent, will affect its use.

Sea water source heat pump

Long coastline, abundant water, moderate water temperature, good water quality, and less prone to winter icing problems.

Discuss new forms

Far from the coastline can use water source heat pump (groundwater heat pump and ground-coupled system) to ease the difficult to get larger water constraints caused by the combination of heat pump + solar energy.

Figure four: (heat pump + solar combination)

Figure four: (heat pump + solar combination)


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