Can I ask for a hotel energy-saving renovation plan?

Answer, 1. Project overview and energy-saving renovation content A hotel in Shanghai is a large luxury five-star hotel located in the center of Shanghai. It consists of a 43-story main building and a 5-story podium. The hotel's air-conditioning usage area is 40,000 m2. The centralized air-conditioning system is equipped with 4 air-conditioning units with a total cooling capacity of 1,900 RT, including 3 centrifugal refrigeration units with a cooling capacity of 500 RT and 1 screw refrigeration unit with a cooling capacity of 400 RT. . Chilled water circulation uses a secondary pump system, and both chilled water and cooling water circulation operate at constant flow rates. The detailed specifications and configuration of the main equipment of the centralized air conditioning system are shown in Table 1, and the system operating principle is shown in Figure 1. The average annual electricity consumption of this constant flow system is about 3.9GWh, and the annual operating cost of the air conditioning system is considerable. Since the hotel's air-conditioning cooling load fluctuates greatly due to the occupancy of the guest rooms, the full-load condition under the design conditions rarely occurs, so the use of a fixed-flow system will generate more cooling capacity and also increase the consumption of the air-conditioning system. The power level remains high, resulting in a waste of electrical energy and operating costs. In 2003, a company carried out a variable-flow energy-saving transformation of the hotel's centralized air-conditioning system. Among them, the primary chilled water pump, secondary pump, cooling water pump and cooling tower fan are all equipped with frequency converters. The original power frequency fixed speed operation is transformed into variable frequency variable speed operation. Therefore, during operation, the cooling capacity of the refrigeration machine is closely related to the air conditioner. Loads are more matched. 2 Detection and analysis of energy-saving benefits after transformation 2.1 Energy-saving monitoring plan and content The monitoring of frequency conversion energy-saving benefits of the centralized air-conditioning system is mainly divided into two aspects: First, test the actual air-conditioning load changes under variable flow conditions of the cooling system to verify and ensure the changes. The system loads during flow conditions and constant flow conditions are similar. In this way, the monitoring data of variable flow conditions and constant flow conditions are comparable, which provides a prerequisite for future comparisons of power consumption: The second is Test the changes in power consumption caused by variable flow operation and constant flow operation of the refrigeration host, chilled water pump, cooling water pump, cooling tower fan and other equipment in the air conditioning system, thereby calculating the power saving rate and analyzing its energy saving effect. According to the specific conditions of the centralized air-conditioning power distribution system, 3 sets of data are calculated every month on the controlled variable flow equipment. In this way, we can roughly obtain comparative data on the monthly power consumption and operating costs of the air conditioning system under constant flow and variable flow conditions, and obtain the monthly power saving rate, thereby further obtaining annual power saving benefits. 2.2 Energy-saving monitoring data analysis By comparing the hourly load rate of the refrigerator and the supply and return water temperature when the system is operating under variable flow and constant flow conditions, and comparing the hourly indoor temperature of the air-conditioned room under variable flow and constant flow conditions, we can make analogies Check the consistency of air conditioning cooling load. The hourly load rate of the system on two consecutive days under variable flow and constant flow conditions is shown in Figure 2. Figure 2 shows that during the two adjacent monitoring days selected during the test, when the air conditioning system was operated under variable flow and constant flow conditions, the hourly changes in the refrigerator load rate were basically similar, both ranging from 95% to 101 %, the fluctuation amplitude is less than 5.1%, which shows that the air-conditioning load is basically the same during the two consecutive days of operation under variable flow and constant flow conditions, thus ensuring the performance of the constant flow and variable flow conditions tested. Consumption data are comparable. Next, let’s compare the changes in the parameters of the system when the air conditioning system operates under constant flow and variable flow conditions, and analyze some system and economic benefits that can be generated under variable flow conditions. The hourly supply and return water temperatures of the host chilled water under variable flow and constant flow conditions are shown in Figure 3. Figure 3 Comparison of the chilled water supply and return temperatures of the main unit under variable flow and constant flow conditions. It can be seen from Figure 3 that during the monitoring period, on two consecutive days, when running under variable flow and constant flow conditions, the refrigeration main unit was frozen. The water supply temperature is constant below 7°C. When operating under variable flow conditions, the average chilled water return temperature is about 11.7°C. However, when operating at a constant flow rate, the chilled water return temperature is relatively low, with an average of 10.5°C. It can be seen that the return temperature of the chilled water under variable flow conditions is about 1.2°C higher on average than that under constant flow conditions. This also shows to some extent that due to the operation under variable flow conditions, the cooling capacity delivered by the chilled water is fully utilized. The utilization of the cooling capacity avoids the waste of cooling capacity caused by the reduction of terminal load when operating under constant flow conditions.

Figure 4 shows the hourly comparison of the inlet and outlet water temperatures of the main engine cooling water under variable flow and constant flow conditions. It can be seen from Figure 4 that when the cooling water supply temperature of the refrigeration host is basically guaranteed to be about 30°C under both working conditions, the cooling water outlet temperature of the refrigeration host under variable flow operation is about 36°C, which is lower than that under constant flow condition. Under normal conditions, the average temperature is about 1.6°C higher. It can be seen that the variable flow condition operation can make the condenser of the refrigeration host basically operate under the rated condition, and at the same time, it can also give full play to the cooling effect of the cooling tower. Let's compare the use effect of the centralized air conditioning system under the two flow conditions. The indoor temperature of the hotel lobby is selected for comparison. The specific comparison is shown in Figure 5. As can be seen from Figure 5, when the chilled water return temperature changes under variable flow and constant flow conditions, the indoor temperature in the hotel lobby basically remains at 25.1°C under constant flow conditions and 26°C under variable flow conditions, that is, concentrated After the air conditioning system is operated with variable flow rate, the indoor temperature increases by less than 3.7% relative to the constant flow rate operation. Therefore, it can be considered that the room temperature is basically unaffected. This proves that the centralized air conditioning system can meet indoor comfort requirements when operating under variable flow rate conditions. . 3. Analysis of operating energy consumption and power saving rate of the centralized air-conditioning system. During the monitoring period when the system operates under two different working conditions: variable flow rate and constant flow rate, by recording the power consumption of the centralized air-conditioning system hourly, the daily and monthly power consumption can be obtained. By comparing with the year-to-year power consumption data, we can get the changes in power consumption of the system after the system's variable flow energy-saving transformation, as shown in Figure 6. Figure 6 shows that after energy-saving transformation, the monthly power consumption of the refrigeration host has been reduced compared with the constant flow operation. On the monitoring days selected in the figure, it is calculated that the daily power consumption saving can reach more than 10%. With the hourly power consumption data and daily saved power consumption data on the monitoring day, and based on the cumulative readings of power consumption, we can further obtain the monthly changes in the monthly variable flow operating conditions compared to the constant flow operating conditions. Electricity-saving benefits and their changing trends. The monthly changes in the electricity-saving rate from 2004 to 2005 are shown in Figure 7. It can be seen from Figure 7 that the power saving rate in winter and transition seasons is greater than in summer. This is mainly because in summer, the cooling load of the air conditioner is larger, and its hourly fluctuations are smaller. Each device in the system basically operates at rated power and rated flow, and the system flow changes less, so there is less waste of cooling capacity. In this situation, the power consumption base is large and the power saving potential is small; in the transition season and winter, the load characteristics of the hotel building determine that there is a certain degree of intermittency and uncertainty in the areas and times that require cooling, and the cooling load fluctuates hour by hour. In this way, the variable flow system after energy-saving renovation can better match the changes and fluctuations in the load, and basically achieve a balance between supply and demand. In addition, the cooling hours in these seasons are much shorter than in summer, and the power consumption base is smaller. Therefore, the power saving rate is higher and the energy saving effect is more obvious. Therefore, under normal circumstances, the energy saving effect of this variable flow energy saving system is better in winter than in summer. It should be noted that the monthly power saving rate listed in Figure 7 is the arithmetic average of the power saving rates measured in the first, middle and last three test periods of each month. That is, the following is the result of annual monitoring. Comparison of the system power consumption obtained when the hotel centralized air-conditioning system operates under constant flow and variable flow conditions on a monthly basis. The entire monitoring period is from August 2005 to January 2006. The energy consumption is as shown in the figure As shown in 8. It can be seen from Figure 8 that after the system changes from the original fixed flow operation to the variable flow fuzzy operation, the energy consumption is significantly reduced. When the original fixed-flow operation was used, the annual operating energy consumption of the hotel's air-conditioning system was approximately 3.7GWh. After the variable-flow energy-saving transformation, the annual operating energy consumption of the system was basically maintained below 3GWh, and the overall energy saving rate reached 20%. above. According to statistics, during the one and a half year period from August 2004 to January 2006, the power saving rate was approximately 22.10. In actual operation, due to the influence of changing environmental conditions between variable flow rate and constant flow rate, the above monitoring and calculation data may change slightly. In short, it can be considered that after the variable flow energy-saving transformation, the annual comprehensive energy-saving rate of the centralized air-conditioning system is basically above 20, which has a significant energy-saving effect.

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