Why does water source heat pump save energy?

Energy saving of water source heat pump system

Take heating operation as an example. At present, the heating modes include centralized boiler room heating mode, thermal power plant heating mode and household gas heating mode, and the water source heat pump mode uses well water, river water, lake water and industrial waste heat. There are also ways to use tap water to assist heating in winter. See table 1 for its energy consumption.

1 energy consumption comparison table of existing residential buildings with heating methods

Energy consumption converted into standard coal.

Centralized boiler room is 25.08Kg/m2, 25.08Kg/m2, 12.4 1Kg/m2, 12.4 1Kg/m 2.

The thermal power plants are 13.96Kg/m2, 13.96Kg/m2, 9.03Kg/m2 and 9.03Kg/m 2.

Household gas heating 10.6Nm3/m2, 13.02Km3/m2, 6.86Nm3/m2, 8.43Kg/m2.

Water source heat pumps (well water, river water and lake water) are 22.46kwh/m2, 9. 16Kg/m2, 14.54kwh/m2 and 5.93Kg/m2.

Water source heat pump (with auxiliary heat source) is 22.46kwh/m2, 4.34Kg/m2, 13.5Kg/m2, 14.54kwh/m2, 2.8 1Kg/m2 and 8.74Kg/m2.

Table 1 calculation basis:

① The residential building is a multi-storey residential building in Beijing, with the existing building heat consumption index Q? H is 3 1.82W/m2, the design heat load index is 43.82W/m2, and the energy-saving building is Q? H is 20.6W/m2 and q is 28.37W/m2. Annual heating demand: 95.46kwh/m2 for existing buildings and 6 1.80kWh/m2 for energy-saving buildings.

② Centralized boiler room: What is the transmission and distribution efficiency of the existing heating system? 1 is 0.85, and the boiler efficiency eta? 2 is 0.55, energy-saving heating system η? 1 is 0.9, eta? 2 is 0.68,

③ The standard coal consumption for power supply and heating in thermal power plant is 0.408kg/kWh and 40.7kg /GJ respectively.

④ COP of water source heat pump heating is 4.25.

From the table 1, it can be seen that the annual energy consumption of water source heat pump heating mode is lower than that of centralized boiler room and thermal power plant, and the energy saving benefit is obvious.

The energy-saving effect of water source heat pump using well water, river water or industrial waste heat as heat source is very obvious. When the energy efficiency coefficient of water source heat pump is 4.0, compared with cogeneration heating mode, the energy saving rate of heating is about 40%. When the auxiliary heating heat source is used, the energy saving of water source heat pump is conditional, and the main influencing factors are: energy efficiency coefficient of water source heat pump; Heating capacity of auxiliary heat source.

① Influence of energy efficiency coefficient of water source heat pump (see Table 2)

Energy consumption when heating capacity is 4KW * Table 2/COP=4 COP=4.5 Energy saving rate

(%)

Auxiliary heat

Energy consumption (kg standard coal) 3× 860/7000× 0.9 = 0.409 3× 860/7000× 0.9 = 0.409/

Compressor energy consumption

(kg standard coal)1× 0.408 = 0.408 0.88× 0.408 = 0.363/

Total 0.8 17 0.77 1 5.6.

* Auxiliary heating capacity is 75% of total heating.

As can be seen from Table 2, after the COP is increased from 4 to 4.5, the energy saving rate is about 5.6%, which is equivalent to reducing the heating capacity by 0.3296KW and the heat load by 10%.

② Influence of heating capacity of auxiliary heater (see Table 3)

Energy consumption when heating capacity is 4KW * Table 3/ Auxiliary heating capacity/total heating 0.75 Auxiliary heating capacity/total heating 0.5 Energy saving rate (%)

Energy consumption of auxiliary heating (kg standard coal) 0.409 2× 860/7,000× 0.9 = 0.273/

Energy consumption of compressor (kg standard coal) 0.408 1×0.408=0.408/

Total 0.8 17

*COP=4

It can be seen from Table 3 that when the auxiliary heating capacity is reduced from 0.75 to 0.5, the energy saving rate is about 16.6%.

③ Energy saving conditions

The energy consumption of cogeneration with a heating capacity of 4KW is:

(4× 860)/(7,000× 0.83× 0.85) = 0.697 kg /4 kWh

Therefore:

When COP=4.0 and the auxiliary heating capacity is 0.5 of the total heating, compared with cogeneration heating mode, its energy saving rate is about 2%.

When COP=4.5 and auxiliary heating capacity is 0.5, compared with cogeneration heating mode, the energy saving rate of water source heat pump is about 8%.

However, when COP=4.0 and auxiliary heating capacity is 0.75, cogeneration will save energy than water source heat pump, and the energy saving efficiency is about 15%. When COP=4.5, its energy saving rate is about 10%.

The main factors of energy saving are as follows:

① The water source heat pump unit is directly placed indoors, and the transmission and distribution loss of the heating network can be ignored.

② The heating energy efficiency ratio COP of water source heat pump unit is greater than 4, and the COP value is still stable under partial load.

③ The water source heat pump system uses well water, rivers, lakes and industrial waste heat and low temperature heat as heat sources, and the heating consumption is only 1/4 of the annual demand.

(4) Water source heat pump system with tap water as heat source needs to add auxiliary heat source in winter. Considering the compressor calorific value, residential simultaneous utilization coefficient and night temperature regulation, the auxiliary heating capacity is about 1/2 ~ 1/3 of the heat load, and the heating capacity is about 1/2 ~ 1/3 of the annual heat demand.

Second, the economy of water source heat pump system

Economy refers to the initial investment, operating cost and hot price of various air-conditioning heating methods.

At present, the combined heating and air conditioning schemes adopted at home and abroad are:

① cogeneration of heat, electricity and cooling: in summer, the thermal power plant adopts extraction and steam absorption refrigeration.

In winter, heating is provided by extraction steam and steam-water heat exchanger in thermal power plant.

② cogeneration of heat, electricity and cooling: hot water+hot water absorption refrigeration in thermal power plant in summer.

In winter, hot water+steam water heat exchanger in thermal power plant provides heat.

③ Direct-fired cold and hot water units: In summer and winter, direct-fired cold and hot water units provide refrigeration and heating.

④ Gas-steam combined cycle is not available.

⑤ Electric refrigeration+gas (oil) boiler heating

⑥ Electric water source heat pump. This unit has stable operation performance and high coefficient of performance (COP), the theoretical calculation can reach 7, and the actual operation time is about 5. It can make full use of natural energy such as rivers, lakes and seawater, and consumes less energy for heating in winter. It is a kind of cold and heat source equipment with good energy saving.

⑦ Air source heat pump. Cold and heat sources are used at the same time, with good integrity and convenient installation. Can be installed in the open air, using air cooling, eliminating the cooling tower and cooling water system. The disadvantage is that when the outdoor temperature is low, it is necessary to increase the auxiliary heat source. The investment and expenses of various schemes are shown in Table 4 (excluding indoor systems).

Comparison of investment and cost of various schemes * Table 4 thermoelectric refrigeration project

(steam) thermoelectric refrigeration (hot water) direct-fired electric refrigeration boiler heating centralized electric water source heat pump split air source heat pump gas-steam combined cycle

Investment (ten thousand yuan /KW) 0. 197

/0.223

(including source network) 0.275

/0.302

(including source network) 0.207 0.206 0.335 0.199 0.436

Cost (Yuan/kWh) 0.1390.1510.2140.207 0.167 0.220 0 0.438+0.

* Provide data for the study of triple supply system in residential quarters, and the cost is annual operating cost.

Taking Xinjiang Coal Mine18th floor dormitory as an example, the economy of water source heat pump heating and air conditioning combined supply scheme is illustrated.

The 18th-floor single dormitory building is Y-shaped, with a total heating and air-conditioning building area of 9564m2, 2 ~18th floor as the standard floor, with a standard floor area of 562.6m2 and a design cooling and heating load of 573.84KW Table 5 shows the heating and air-conditioning combined supply scheme, Table 6 shows the initial investment ratio of each scheme, Table 7 shows the comparison of operating costs of each scheme, and Table 8 shows the comprehensive comparison of each scheme.

Heating and air conditioning scheme table 5 scheme heating and air conditioning mode matters needing attention

Scheme 1 water source heat pump (water-air) with water as cold and heat source in winter: hot air generated by heat pump is sent indoors in summer; cold air generated by heat pump is sent indoors, and each household is provided with a heat pump to send air to each room.

Scheme 2: water source heat pump (water-water) with the following water as cold and heat sources: in winter, the hot water generated by the heat pump is sent to the fan coil unit; In summer, the cold water generated by the heat pump is sent to the fan coil as the central heat (cold) source, and each household is equipped with a fan coil.

Scheme 3: Electric refrigeration in winter+heating in thermal power plant: steam+steam-water heat exchanger in thermal power plant in summer: central air conditioner sends cold water to the centralized heat (cold) source of fan coil, and each household is equipped with fan coil.

Comparison scheme split air conditioning+boiler room heating Winter: boiler room (thermal power plant) heating, indoor radiator summer: each household is equipped with split air conditioning with centralized heat source and decentralized cold source air conditioning with poor quality.

Table 6 Comparison of Initial Investment of Each Scheme

Scheme 1 (Import) Scheme 2 Scheme 3 Comparison Scheme

Imported and made in China.

Initial investment * (10,000 yuan) 237.4305.83082888886

Investment in unit construction area (RMB/m2) 248 36438+09.7 2438+0.20089.00100000006

* The calculation includes 15% installation fee, 5% operation and debugging fee, 5% tax and management fee, 2% design fee and 10% profit.

Comparison of operating costs of various schemes (RMB/m2) Table 7

Scheme 1 Scheme 2 Scheme 3 Comparison Scheme

Heating, air conditioning, air conditioning, air conditioning, air conditioning, air conditioning.

Regardless of the simultaneous use coefficient, the heat recovery coefficient is19.2519.25 9.56.29.57.2.

Total19.2519.2515.716.7.

Consider the correction factor10.7810.78 9.5 4.34 9.57.2.

Total10.7810.7813.8416.7.

[BG] f] Xinglong Coal Mine is located in Yanzhou City. According to the meteorological data of Yanzhou City, the heating period in winter in this area is 106 days, the delay hours are 2,544 hours, and the maximum load hours are 2,544 * (20-0.4)/[20-(17)] =/kloc. In summer, the air conditioning cycle is 90 days, and the delay hours are 2 160 hours. The actual test data are provided by Jinan and Zibo, and the maximum load hours in summer are 720 hours. Unit building area: 60w/m2 *1847 =110.5 kwh in heating period and 60w/m2 * 720 = 43.2kwh in cooling period. ..

Comprehensive comparison of various schemes Table 8 Energy consumption per unit heating (cooling) capacity (kg standard coal /kwh) System investment per unit heating (cooling) capacity (RMB 10,000 /KW) Annual operating cost per unit heating (cooling) equipment (RMB /kwh)

Scheme 1 0.057 0.4 14 (import) 0.07

Option 2 0.057 0.533 (imported) /0.4 15 (domestic) 0.07

Option 3 0.1330.4120.12

The comparison scheme is 0.148 0.465 0.11.

From the comparison of Table 6, Table 7 and Table 8, it can be seen that scheme 1 is the best scheme for heating and air conditioning in Xinglong Coal Mine.

The aforementioned scheme 1 water source heat pump (water-air) and scheme 2 water source heat pump (water-water) are both feasible in technology and economy. The large-scale water source heat pump in the second scheme is a centralized cold (heat) source mode. At present, there is no large-scale water source heat pump manufacturer in China, and the imported equipment is expensive. However, the domestic water source heat pump series is incomplete, and the single unit capacity is small. Only by placing multiple devices in the computer room can a centralized cold (heat) source form be formed, which has a large investment and is inconvenient to install, operate and maintain.

Judging from the energy consumption per unit heating (cooling) quantity, the scheme 1 has obvious advantages in investment and operation cost. Among them, the price of imported heat pump units is similar to that of domestic equipment in Scheme 2, but much lower than that of imported equipment in Scheme 2, and there is no need to build another computer room. 18 single dormitory implementation plan 1.

The main reasons for the low investment of water source heat pump heating and air conditioning combined supply scheme;

① There is no dedicated computer room. The area of central air-conditioning machine room (including air-conditioning equipment, electrical equipment and others) is about 5-8% of the air-conditioning building area, of which air-conditioning equipment accounts for about 4-5%. Take the 10 floor building as an example, in which the computer room occupies about one floor. Water source heat pump distributes air conditioning equipment to every household, which reduces the construction cost of computer room and increases the office area and business area.

(2) The closed water pipe should not be insulated, and there is no special requirement for the shaft. The shaft of central air conditioning system occupies more effective area of the building, and the shaft of all-air system occupies a larger area. Whether the shaft layout is suitable or not will affect the efficiency of air conditioning system and have a great impact on air conditioning investment.

(3) It does not occupy the effective area of the room, and the indoor fan coil of the central air conditioning system is placed under the window, which has a great influence on the residence.

Reasons for low operating cost of water source heat pump cogeneration scheme;

① When the water source heat pump is running, about 3/4 of the total heating comes from well water, low-temperature heat from rivers or industrial waste heat; When the air conditioner is running, the total cooling capacity is about 1.2 times of the total cooling capacity, and the total heat dissipation is shared by low-temperature heat or industrial waste heat, which greatly reduces the operating cost of the heating and air conditioning system.

② The water source heat pump unit is directly installed in the user's room, which reduces the transmission and distribution loss.

③ The water source heat pump unit has high energy efficiency coefficient and good stability of performance coefficient.

④ Water source heat pump system has heat recovery performance. When there are rooms in the same building that need heating and air conditioning, refrigeration and auxiliary heating are not needed.

Three. Reliability of water source heat pump system

The operation reliability of heating and air conditioning system means that the system has good stability and flexible adjustment. The so-called good stability means that the thermal comfort parameters such as temperature, humidity and airflow speed in the heating and air-conditioning room are not affected by the outside world and remain within the design range, that is, when an accident occurs in a certain part of the system or a user equipment fails, it has no or little impact on other rooms. The heat pump unit of water source heat pump system is set in each room. When a unit fails, the water supply and return valves connected to the equipment will be closed, which will not have any impact on adjacent users. It is said that the stability of water source heat pump is good.

In the combined heat pump unit with automatic temperature control device for water source heat pump, there is no need to set up another control center or control room, and users can flexibly control the temperature of the control room and the speed of the fan according to their own wishes. This method is suitable for public buildings, especially for houses of different ages, occupations and living requirements.

In addition, the water source heat pump system is convenient for heat metering, and users of property companies can charge for electricity, which is an important measure to solve the current difficulty in charging for heating and air conditioning.

Fourthly, design is one of the conditions to ensure the reliability, economy and energy saving of water source heat pump.

Water source heat pump units create key conditions for water source heat pump air conditioning heating system. Without such a unit, there would be no such system. The quality of unit operation is related to the combination mode of source, network and unit system. That is, it is closely related to system design.

See Table 9 for the design features of water source heat pump heating and air conditioning system.

Table 9 Design Features of Water Source Heat Pump Central Air Conditioning System Project

Water system water temperature (℃) 15℃/35℃ air conditioning 7℃/ 12℃ heating 60℃/50℃

Water quantity (m3/h) and flow rate (m3/s) are 0.191s0.684m3/HV ≯ 0.83m/SG ≮1gpm = 0.0631/.

Wind system) air volume (l/s) air supply temperature difference (△t) wind speed (m/s) 142 ~ 248L/s (high, medium and low) 5 1 1 ~ 893m3/h = about/kloc-0. Supervisor 3-4m/s, supervisor 2.5-3m/s.

The supplementary heating capacity (KW) is calculated according to the heat absorption capacity. Considering the simultaneous use coefficient or changing the design parameters at night, the supplementary heating capacity is about 1/2 ~ 1/3 of the design heat load.

The cooling tower is selected according to the total heat dissipation of 0.6 ~ 0.8, and the cooling tower is calculated according to the total heat dissipation.

Special control of self-controlled heat pump; Constant temperature regulator, automatic transfer switch, water temperature controller, unit safety control and wind speed control. Indoor: the fan-coil unit is controlled at three speeds, and the temperature, pressure and flow rate are controlled in the central control room.

Operating parameters * Table 10 Operating parameters of air conditioning and heating.

Minimum standard, maximum minimum standard and maximum standard.

Operating air inlet dry bulb temperature bulb 2114 2418 29 2613-20-21-

Inlet and outlet water 7 12 33 38 59 54 -4*2? -6*2 18 14 29 26

Extreme inlet dry bulb temperature bulb 18 12-35 26 5-27-

Inlet and outlet water 7 12-49 54-4 * 2? -6*2 ? - - 29*3? 26*3?

〔BG)F〕

Note: [WB]* 1 unit gas supply is 0. 16m3/s per cold ton, and water flow is 0. 16L /s to 0. 19L /s per cold ton.

* 2 is an ethylene glycol solution at this time.

* 3 can be 35/28℃ in a short time.

The following problems should be paid attention to when designing water source heat pump system.

① The capacity of water source heat pump unit should not be too large. When the cold and heat source equipment of central air conditioning is selected, the refrigeration (heat) capacity of the equipment is about 1.05 ~ 1. 10 of the designed cold (heat) load. When selecting a water source heat pump unit, it should be as close as possible to the design cooling (heating) load. If the unit is too large, the running time is short and the startup is frequent. The unit capacity is appropriate, and the operation time is long, which is beneficial to dehumidification.

(2) The selection of water temperature in closed water system requires lower water temperature in summer to improve energy efficiency and reduce power consumption. In winter, the water temperature should not be too high. When the water temperature is high, the cooling capacity is high, but the power consumption is also high, and the energy efficiency coefficient has little change.

③ The coefficient of simultaneous use of heating and air conditioning buildings should be considered in the design. At the same time, the value of the utilization coefficient is related to the type and number of buildings, which needs to be determined through theoretical calculation and actual measurement. The data listed in "Determination of Simultaneous Use Coefficient in Air Conditioning Load Calculation of Residential Buildings" are: when the number of households is less than 100, the coefficient is 0.7; 0.65 ~ 0.7 when the number of households is 100 ~ 150; 0.6 when the number of households is 150 ~ 200.

Verb (abbreviation of verb) conclusion

From the above analysis, it can be seen that the water source heat pump system is a reliable, economical and energy-saving heating mode. In this way, clean energy is used, and the energy saving effect is obvious. Energy saving is environmental protection. Under the condition that electricity enters the buyer's market and people's living conditions improve rapidly, water source heat pump will undoubtedly be a popular heating and air conditioning method.

(Reference) Beijing Huayang Water/Ground Source Heat Pump 0 10-8 1762900