What are the hotel’s cost-saving measures?

As my country’s national economy continues to develop rapidly, it has driven long-term rapid growth in energy consumption. At present, my country's energy supply has shown a tense situation. Vigorously promoting conservation and consumption reduction, easing resource bottleneck constraints, and achieving sustainable development of the energy environment and economy and society are the core of my country's energy use work.

Energy is the basic power to ensure the operation of various electromechanical equipment in the hotel. With the rapid development of modern hotels in our country, although the energy management level of hotels has been greatly improved and the energy consumption of hotels has been declining year by year, compared with developed countries, my country's hotel industry still has problems in terms of energy utilization efficiency. Large gap. Based on the characteristics of hotel electromechanical equipment, this article will briefly introduce the energy-saving technologies that are currently commonly used and proven to be relatively mature in practice. Conduct basic theoretical analysis on specific energy-saving projects and obtain technical support from basic theories. A physical engineering case is used for analysis, and energy-saving methods and key points to note in their practical application are summarized. It is intended to be a reference for everyone when carrying out energy conservation work.

1. Basic situation of hotel energy consumption

At present, the energy consumption cost of my country's hotel industry accounts for about 13% of hotel revenue on average.

The average energy consumption ratio of hotels is about:

Air conditioning 51%

Lighting 21%

Mechanical and electrical 17%

The other 10%

From the general proportion of hotel energy consumption, air conditioning energy consumption accounts for more than half of the hotel's energy consumption, and has the greatest energy saving potential. Let’s start with the basic theory of freezing. Analyze ways to save energy in air conditioners and demonstrate corresponding energy-saving methods and practices.

2. Hotel air conditioning energy-saving technology and methods

(1) Brief description of basic refrigeration theory

1. Analysis of actual refrigeration cycle:

Text description of the refrigeration cycle process:

The gas refrigerant that comes out of the evaporator (4) is in state 1 (T1, P1); after adiabatic compression by the compressor, it becomes state 2 (T2, P2) . The compressed gas refrigerant is isobarically cooled and condensed in the condenser (2), and changes to the liquid refrigerant in state 4 (T3, P2) through state 3 (T3, P2), and then passes through the throttle valve (3) It expands to low pressure (P1) and becomes a gas-liquid mixture in state 5 (T1, P1). The liquid refrigerant at low temperature (T1) and low pressure (P1) absorbs the heat of the cooled material in the evaporator (4), vaporizes under P1, and becomes the gaseous refrigerant in state 1 (T1, P1). The gaseous refrigerant re-enters the compressor through the pipeline and starts a new cycle. These are the four processes of the freezing cycle.

2. Refrigeration theory analysis of air conditioning energy saving approaches (1)

(1) Refrigeration coefficient ∑=Q1∕-W=Q1∕(-Q2)-Q1

< p>In the formula, Q1 - the heat absorbed by the refrigerant from the environment (cold object T1), is a positive value;

Q2 - the heat released by the refrigerant to the environment (hot object T2), is a negative value.

W——The work done by the compressor on the material system (refrigerant) is negative.

Text description: ∑ Indicates the energy that the refrigerant can

absorb from a cold object with the addition of 1 unit of work. It is an important indicator of the efficiency of the refrigeration cycle.

3. Refrigeration theory analysis of air conditioning energy saving approaches (2)

(2) Ideal refrigeration cycle (reversible cycle)

Numerical expression: ∑ can=Q1 ∕(-Q2)-Q1＝T1 ∕T2-T1

●In the formula: T1—the absolute temperature of the cold object (evaporation temperature)

T2—the absolute temperature of the hot object ( Condensation temperature)

● Text description: For an ideal refrigeration cycle, because each part is reversible, the efficiency of the ideal refrigeration cycle can be maximized. And it is related to T1 and T2, not to the refrigerant.

●Analysis: When the evaporation temperature T1 increases, the freezing coefficient increases; when T1 decreases, the opposite is true.

When the condensation temperature T2 decreases, the freezing coefficient increases; when T2 increases, the opposite is true.

4. Refrigeration theory analysis of air conditioning energy saving approaches (3)

(1) Calculate the refrigeration capacity on the T-S diagram

Based on the refrigeration cycle T-S diagram analysis can be obtained:

● The standard refrigeration working condition is (1-2-3-4-5-1) and its cooling capacity integrated area Q1;

● When the condensation temperature When it is reduced to T2', the refrigeration working condition is (1-2-3-4'-5'-1), and the integrated area of ??refrigeration capacity is Q1+Q1';

● When the evaporation temperature rises When it reaches T1', its refrigeration working conditions are (1-2-3-4-5''-1), and its cooling capacity integrated area is Q1+Q1''.

(2) Case study of changing operating conditions to analyze changes in freezing capacity

(a) The freezer uses ammonia as the refrigerant. Standard operating conditions:

Evaporation temperature T1=-15℃

Condensation temperature T2=30℃

Subcooling temperature T2'=25℃

△Refrigerating capacity 100000KCal∕h

(b) After changing the operating conditions:

Evaporation temperature T1＝-10℃

Condensation temperature T2 =25 ℃

Subcooling temperature T2'=20 ℃

△Refrigerating capacity 135000KCal∕h

(5) Refrigeration theory analysis of air conditioning energy saving approaches (4)

☆ Refrigeration theory and practice prove

Under certain conditions of evaporation temperature:

When the condensation temperature T2 increases by 1℃, the efficiency of the air conditioning chiller decreases by about 4.2% about.

When the condensation temperature T2 decreases by 1°C, the efficiency of the air conditioning chiller increases by about 4.0%.

Under certain condensation temperature conditions:

If the evaporation temperature T1 decreases by 1°C, the efficiency of the air conditioning chiller will decrease by about 4.2%.

When the evaporation temperature T1 increases by 1°C, the efficiency of the air conditioning chiller increases by about 4.0%.

(6) Refrigeration theory analyzes air-conditioning energy-saving approaches (5)

☆ Refrigeration theory supports the direction of energy-saving approaches

A. The lower the condensation temperature, the lower the refrigeration coefficient The larger the value, the lower the power consumption of the compressor.

B. The higher the evaporation temperature, the greater the refrigeration coefficient, which can reduce the power consumption of the compressor.

C. The heat absorbed by the cold object during the evaporation process and the heat generated by the compressor can be recycled.

According to the air-conditioning energy saving methods supported by refrigeration theory, corresponding energy-saving equipment, automated control systems, process pipelines, etc. can be designed in a targeted manner to achieve the optimization of energy-saving transformation.

(2) Basic conditions and requirements for comprehensive energy-saving renovation of hotels

1) Adapt measures to local conditions and rationally adopt energy-saving technologies and methods that suit the hotel’s circumstances.

2) Be familiar with the operating conditions of the system and equipment.

3) The economic benefits of energy saving are obvious.

4) It does not affect the normal operation of facility systems and equipment, nor does it affect the quality of customer service.

5) Energy-saving facilities are required to be simple to operate, easy to control, and have no safety hazards.

6) Basically does not affect the surrounding environment.

7) After investigation and research and scientific demonstration, the energy-saving renovation project will be decided.

(3) Introduction to hotel air-conditioning energy-saving technologies and methods and their applications

1. Central air-conditioning waste heat recovery technology and its applications

Make full use of the principle of heat exchange, The waste heat (condensation heat) of the air conditioner is recovered to produce 50-60°C hot water for use in hotel rooms, saunas, employee bathrooms, etc. Because the recycled air conditioner is condensation heat waste heat. Therefore, the amount of hot water produced consumes zero energy. At the same time, due to the recovery and utilization of part of the waste heat, the condensation temperature is reduced. It also increases the efficiency of central air conditioning units by 5 to 10%. Since the host load is reduced after the technical transformation, it not only saves the power consumption of the host, but also reduces the failure rate of the host and extends the service life of the host. It is an excellent energy-saving technology that serves multiple purposes.

(1) Schematic flow diagram of central air conditioning waste heat recovery technology

(2) Schematic flow diagram of air conditioning waste heat recovery process of Shenzhen Donghua Holiday Hotel (case analysis)

Air conditioning Features of the waste heat recovery system:

●It realizes the pipeline process flow of two hosts as backup for each other and a set of waste heat recovery system, thus further improving the waste heat recovery rate.

●The waste heat recovery hot water system is interconnected with the original hot water system to ensure the reliability of hot water supply.

(3) Application scope of central air conditioning waste heat recovery technology

Widely used in piston and screw chillers.

The hot water tank volume is recommended to be set at about 30% of the total water consumption.

Equipped with a complete hot water boiler backup system.

Equipped with an automatic adjustment system for constant hot water outlet temperature.

(4) Calculation of the area of ??waste heat recovery device of key equipment

Heat transfer equation: Q=KF△tm

Physical meaning: Under a certain heat transfer state , the heat transferred per unit area and per degree of temperature rise.

In the formula: K - heat transfer coefficient Kcal/m2.h. ℃

F - heat transfer area m2

△tm - logarithmic average temperature difference ℃

Heat transfer coefficient K: describes the state of a certain heat transfer process, that is, the size of the heat transfer capacity. The source of the K value has three aspects: selection of production practice data; experimental measurement; theoretical calculation.

Recommended here: The heat transfer coefficient K value for calculating the air-conditioning waste heat recovery area is 580~720Kcal/m2.h.℃

2. Frequency conversion energy-saving technology of central air-conditioning circulating water system< /p>

(1) Frequency conversion energy-saving technology of central air-conditioning circulating water system

Analysis of cooling load in air-conditioning operation:

Currently, most hotels’ central air-conditioning circulating water systems use refrigeration pumps and The cooling pump speed is not adjustable. As long as the air conditioner is running, regardless of the load or season, the refrigeration pump and cooling pump will run at the rated speed, so energy waste is serious.

(2) Technical feasibility of energy-saving transformation

Using AC inverter to control water pump operation is one of the effective ways to save energy in central air-conditioning systems. Figures 1 and 2 show the pressure-flow (H--Q) relationship and power-flow (P--Q) relationship of the two operating states of valve regulation and frequency converter control.

Curve (1) in Figure 1 is the water pump. Curve 1 in Figure 1 is the H-Q curve of the water pump at rated speed. Curve 2 is the H-Q curve of the water pump at a lower speed. Curve 3 is the valve. The H-Q curve of the pipeline at maximum opening, curve 4 is the H-Q curve of the pipeline at a smaller valve opening. When the valve opening is adjusted under the condition of constant speed operation, the operating point will move from A to B along curve 1; when the valve opening is maximized and the frequency converter is used to adjust the water pump speed, the operating point will move from A along curve 3. C. Obviously, the flow rates at point B and point C are the same, but the pressure at point B is much higher than the pressure at point C. That is to say, the energy saving effect is significant when the variable frequency control water pump operates at a variable speed.

Curve 5 in Figure 2 is the P-Q curve under the frequency converter control water pump speed regulation operation mode, and curve 6 is the P-Q curve under the valve adjustment mode. It can be seen that under the same flow rate, the frequency conversion control method is better than the P-Q curve under the valve adjustment mode. The energy consumption of the valve adjustment method is small, and the relationship between the two can be expressed by the following formula:

△P＝0.4+0.6Q/Qc-(Q/Qc)3Pc

Among them, Q is Actual load flow, Qc is the rated flow, Pc is the rated load power, and △P is the power saving value. It is not difficult to calculate that when the load flow drops to 70% of its rated flow, the power saving rate will reach 48%.

(3) In addition to saving electric energy, the application of frequency converter will also bring the following advantages to the operation of the chiller:

1) Adjust the water flow to connect the water inlet and return to the chiller. The water temperature is controlled within an appropriate range to ensure the heat exchange rate of the host and save the energy consumption of the host.

2) The pipeline valve is opened to the maximum, eliminating the local loss of throttling on the valve and saving electric energy.

3) Realize soft start of the motor (the maximum starting current is less than the rated current), and have protection measures such as undervoltage, overcurrent, phase loss, and leakage, which improves the operating conditions of the motor and increases the reliability of the operation. .

4) Smooth start-up, no impact load, greatly reduces equipment loss, extends equipment service life, and reduces maintenance costs.

(4) Frequency conversion energy-saving control of central air-conditioning circulating water system

(5) Basic conditions for the practical application of frequency conversion energy-saving technology of central air-conditioning circulating water system:

1 ) is widely used in chilled water pumps, cooling water pumps, and cooling towers. Larger refrigerated hoods (air handlers) and other places with variable loads. Generally, the energy saving space is about 20-50%.

2) Use a variable frequency closed-loop control motor to set the temperature as needed, so that the heat capacity reserved by the equipment system and the heat load that changes with time and seasons are automatically adjusted through the speed. Under the conditions of meeting the normal use of the heat load, Achieve maximum energy saving.

3) A comprehensive hydraulic calculation of the circulating water system is required

Find the total resistance of the pipeline

△ P = ∑hf=ho＋hc＋hj

< p>n

＝ho＋（λ·L/d＋∑C）w2/2g [mH2O]

i=1

●In the formula: ho― ―Hydrostatic head [mH2O]

hc――Resistance head of pipeline [mH2O]

hj――Dynamic head of fluid [mH2O]

< p>What is the margin for calculating the pump head of this system? Thereby confirming the energy saving space.

4) Select the appropriate location, set up minimum pressure difference protection, and strengthen pipeline resistance reduction management.

(5) Case analysis of frequency conversion energy-saving renovation of central air-conditioning circulating water system

1) Case analysis of Shenzhen Danfeng Bailu Hotel

Circulation system power loop control function:

1. The three pumps can operate automatically and save energy under variable frequency regulation.

2. The frequency converter directly controls two pumps and indirectly controls one pump.

3. After the frequency conversion part fails, it can operate under the condition of power frequency AC380V/50Hz.

4. The closed-loop collection of refrigeration pump and cooling pump water cooling tower parameters is sent to the intelligent control substation for processing, and instructions are issued to adjust the water pump motor speed.

Since the energy-saving system was put into operation, the power-saving effect has been obvious, with an average annual power-saving rate of more than 38%.

In one of the introductions and case studies of hotel comprehensive energy-saving technologies in the previous issue, the refrigeration theory was used to analyze the ways of air-conditioning energy-saving, and the ways and directions of air-conditioning energy-saving were pointed out; hotel air-conditioning energy-saving technologies and methods were introduced and their Application: Technology and application of central air-conditioning waste heat recovery; central air-conditioning water circulation system frequency conversion energy-saving technology. This chapter continues to introduce the relevant air-conditioning energy-saving technologies, methods and applications:

1. VRV variable frequency direct cooling air-conditioning energy-saving technology and its application cases

At present, most air conditioners in hotel rooms are classic water cycle Secondary cooling system central air conditioning. This air conditioning system is mature and reliable, has a long history, and is widely used in various occasions. As people's awareness of energy conservation has further increased, many new generation air conditioning systems that are energy-saving, environmentally friendly, and practical have been developed. VRV variable frequency direct cooling air conditioners are one of the more typical energy-saving products. The following is a theoretical analysis and comparison of water cycle cooling system air conditioners and new VRV variable frequency direct cooling air conditioners.

1. Schematic diagram of water cycle cooling air conditioning system:

Refrigeration process flow diagram

2. Schematic diagram of VRV variable frequency direct cooling air conditioning system

Refrigeration process flow diagram

3. Comparison between water cycle refrigeration air conditioning system and VRV variable frequency direct cooling air conditioning system

According to the analysis of the above two refrigeration process flow charts, it is not difficult to see that the water cycle The refrigeration air conditioning system is equipped with a chilled water circulation system and a cooling water circulation system. The main equipment includes chilled water pumps, cooling water pumps, cooling towers, power distribution cabinets, water circulation water pipelines, valves and fittings, etc. The system is complex and takes up a large space in the hotel room and consumes a lot of resources; the VRV variable frequency direct cooling air conditioning system has no water circulation load. In the cooling system, the refrigerant directly evaporates and absorbs heat in the fan coil for cooling. The condensation heat is cooled by air. The system is simple and the heat exchange efficiency is high. The heat exchange efficiency of direct refrigeration and heat exchange is about 8% to 15% higher than that of indirect refrigeration and heat exchange. In other words, the cooling efficiency is increased by about 8% to 15%.

4. Case study of 999 Danfeng Bailu Hotel’s rooms using VRV variable frequency direct cooling air conditioners:

(1) The total cooling load of the guest rooms is about 2330kW/h

(2) Energy consumption cost of using VRV variable frequency direct cooling air conditioner

Analysis conditions: The power consumption of the air conditioner compressor is not considered for the time being. Only the energy consumption and operation and maintenance costs of the condensing fan are considered.

The actual data after operation are as follows:

The annual power consumption of the condensing fan is about 360,000 KWH (0.9 yuan/KWH)

The maintenance cost is about 25,000 yuan/ Annual

The total operating cost is 349,000 yuan/year

(3) Energy consumption and cost of the water circulation cooling central air-conditioning system.

Analysis conditions: The power consumption of the air conditioning compressor is not considered for the time being, and only the energy consumption and operation and maintenance costs of the water circulation equipment are considered.

The design selection and operating cost calculation data based on the total cooling load of the guest room are as follows:

The annual power consumption of water circulation equipment is approximately 878,000 KWH (0.9 yuan/KWH)

< p>Water consumption 4600M3/year (4.5 yuan/M3)

Water treatment cost 20,000 yuan/year

Maintenance cost 25,000 yuan/year

Total operating costs 855,900 yuan/year

(4) Comparison of energy savings between plans

Temporarily consider that the compressed electric power of the two air conditioners is equal (the thermal efficiency of direct cooling and heat exchange is 8%~15% higher than that of indirect cooling and heat exchange) , ignored for the moment in this comparison).

Annual power saving: 518000KWH

Annual cost saving: 506,900 yuan

(5) Investment recovery period

Select VRV direct cooling type The air conditioning system equipment and installation costs are 1.9 million yuan more than the equipment and installation costs of the classic water circulation cooling central air conditioning system.

The recycling life is about 3.7 years.

(6) Analysis results

Advantages: VRV direct cooling air conditioner not only has obvious power saving effect, but also does not require water circulation to carry cooling water, saving water resources. At the same time, it fundamentally solves the environmental pollution problems caused by the noise and water vapor of the water cooling tower and the chemical water pollution problems caused by water treatment. It has many advantages such as low operating cost and high degree of self-control.

Disadvantages: VRV direct cooling air conditioners require several groups of subsystems (outdoor hosts) for use in hotel rooms, and require a large outdoor installation area. Since there are many refrigerant pipe connections, it is difficult to find and repair a leak once it occurs. At present, the length of refrigerant pipeline is limited to 90~120m.

2. Air source heat pump triple generation technology and its application

Currently, the common product manuals or technical introductions about various types of heat pumps are relatively mysterious. Making an originally simple problem very complicated may be because the more mysterious and complex it is, the more scientific and technological content it contains. Here is a general introduction to various types of heat pumps.

Ground source heat pumps, water source heat pumps, and air source heat pumps are usually collectively referred to as active heat pumps. No matter which type of heat pump, the working principle is the same. The difference lies in the different names of the heat sources.

Ground source heat pump technology uses shallow underground geothermal resources (including soil, groundwater, and surface water) to use the geothermal source as a cooling heat source for heat pump cooling in summer and a low-temperature heat source for heating in winter; the same applies to water sources. Heat pumps use rivers, rivers, lakes, seas, reservoirs, etc. near the building as heat sources; currently, both practical technologies realize the triple supply of building air conditioning, heating and domestic water; while air source heat pumps absorb heat from the air. As a heat source, practical technology realizes the dual supply of heating and domestic water to buildings. No matter what kind of heat pump, a large amount of heat energy is obtained by inputting a small amount of electrical energy, generally up to 1:3.5 or more.

In summary, the advantages of ground source heat pumps and water source heat pumps are very prominent, but they are often not suitable for application in many places due to the limitations of the objective conditions of the building, the geological conditions and the natural environment where the building is located. Especially in high-density building clusters like Shenzhen, it is more difficult to implement. Therefore, it is necessary to adapt to local conditions and adopt a product that is suitable for southern my country (subtropical climate) and is not affected by urban buildings and geological conditions. The new air source heat pump adds a set of evaporators on the basis of the original air source heat pump.

It is still possible to achieve: triple supply of air conditioning and refrigeration, heating and domestic hot water.

1. Air source heat pump triple supply technology.

Mainly use the annual average temperature of more than 20℃ in southern my country (Shenzhen, Hainan, and southern Guangdong). The average winter climate is 9~16℃, with the extreme temperature not lower than 3℃. Superior climate conditions have opened up good prospects for air source heat pumps.

2. Process flow diagram of air source heat pump triple generation technology

It can be seen from the process flow diagram that in the spring, summer and autumn air-conditioning seasons, the heat source of the heat pump comes from the air-conditioning load, and in the non-air conditioning season in winter, the heat source From the outdoor air, the compressor performs work to compress the gaseous heat-absorbing refrigerant after absorbing heat and evaporating into a high-temperature and high-pressure gaseous refrigerant, which releases heat in the condenser to heat hot water for domestic use (or hot water for heating). The gaseous refrigerant is cooled and condensed into liquid refrigerant, which expands through throttling until the evaporator evaporates and absorbs heat, thereby completing a thermal cycle.

3. Features of the equipment:

It is equipped with two sets of evaporator systems, one (i.e. refrigeration terminal equipment) is used in the spring, summer and autumn air conditioning seasons, and the other is used in the winter. When used in non-air conditioning seasons, the operation is divided into two working conditions.

4. Technical indicators of air source heat pump

The average air source temperature is 9~26℃

Refrigerating temperature: 7~9℃

Heating temperature: 55℃ (hot water)

Refrigerant medium: 134a

Cooling and heating efficiency: >3.2~3.5

5. Technical characteristics

Air source heat pump technology is especially suitable for areas in southern my country where the extreme winter temperature is ≥3°C. It can save energy costs by more than 40% throughout the year.

Using air as the heat source of the heat pump is inexhaustible. The heat source cost is zero. There is no need to dig wells or bury pipes. The one-time investment cost is low and it is not affected by geological conditions and buildings. .

It is easy to maintain and has lower operating costs than ground source water source heat pumps.

The specifications of air source heat pumps currently produced in my country are relatively small, and there are currently no large-scale equipment. It has yet to be developed for heating in large hotels. At present, air source heat pumps are mainly used to produce hot water for domestic use and are widely used as a by-product of air conditioning and refrigeration.

6. Application of air source heat pump in hotels

It is recommended to configure the air conditioner host + air source heat pump. The heat pump selection can be based on the total consumption of domestic hot water in the hotel.

Some hotels still use air source heat pump cooling in winter (non-air conditioning season) to dehumidify the hotel air, and have achieved good results.

3. Introduction to the new technology of using CO2 concentration to control fresh air volume

Public areas such as hotel banquet halls, multi-function halls, and restaurants have a heavy air conditioning load. When not dining, or when no banquets, celebrations, meetings and activities are held, the indoor air conditioning load is very low. But once it is started, the number of people often increases greatly, the hall is full of guests, the seats are packed, and sometimes it is even overcrowded by more than 20%. Therefore, when designing and calculating the cooling load of air conditioners in banquet halls, multi-function halls and restaurants, the cooling load margin for full and over-occupancy must be fully considered, so the designed cooling loads are all very large.

This air conditioning method mostly uses new air, low wind speed combined large air volume air conditioning units for cooling. There are two commonly used air supply and return methods:

a) Only air supply and no return air method are provided;

b) There are air supply and return methods; no matter which method , the fresh air percentage of this system is very large. The cooling capacity of air conditioners is generally more than double that of circulating cooling.

How to reasonably adjust the fresh air volume according to the actual load changes of the air conditioner to achieve energy saving is the central content of this technical introduction. Use CO2 concentration to adjust the fresh air volume energy-saving plan, as shown in the figure:

Schematic diagram of the fresh air energy-saving plan for banquet halls and public places

Hotel banquet halls, multi-functional halls, restaurants and other public places The *** area uses CO2 concentration to adjust the air conditioning fresh air volume energy-saving technology. It mainly uses CO2 probes to collect the CO2 concentration in the space, and sends instructions to the intelligent analysis controller through the sensor to control the electric differential adjustment damper. In order to adjust and control the fresh air volume, it is always in the best energy-saving operation state. This technology is suitable for occasions with air supply and return air conditioning methods. The average energy saving value can reach more than 20~35%.