Central air conditioning energy-saving

With the implementation of urban energy-saving transformation and green buildings, achieving building energy conservation and emission reduction has become an urgent task. As the main equipment for energy consumption in public buildings, air conditioning accounts for about 60% of building energy consumption, exceeding the total energy consumption of lighting, elevators, and office equipment. Therefore, the focus of energy conservation and emission reduction in buildings is on the air conditioning system.

Development Background and Benefit Analysis

Background Introduction

With the implementation of urban energy-saving transformation and green buildings, achieving building energy conservation and emission reduction has become an urgent task. As the main equipment for energy consumption in public buildings, air conditioning accounts for about 60% of building energy consumption, exceeding the total energy consumption of lighting, elevators, and office equipment. Therefore, the focus of energy conservation and emission reduction in buildings is on the air conditioning system.

The long-term operation of air conditioning under heavy load will not only increase the failure rate of air conditioning, but also greatly shorten its service life. Reasonable setting of air conditioning temperature and scientific management of air conditioning operation can provide a relatively healthy and comfortable indoor environment, meet normal work and living needs, save energy, and protect the ecological environment, which is a good thing for the country and the people. According to calculations, with the correct use of air conditioning, an increase of 1 ℃ in the temperature of the refrigeration air conditioning can save 8% of electricity; For every 2 ℃ decrease in temperature of the hot air conditioner, it can save 10% of electricity. It can be seen that the energy waste caused by setting the cooling temperature too low or the heating temperature too high is astonishing. For building managers, the inability to manage, monitor, and control all air conditioning operation status in real time results in significant energy waste.

Current situation of air conditioning system

1. Air conditioners cannot conduct unified big data analysis on energy consumption, usage habits, air conditioning efficiency, etc., making it impossible to measure the working conditions of each air conditioner, and some complex optimization control strategies cannot be implemented.

2. Distributed control makes it impossible to carry out centralized energy-saving management (including room temperature control), which can easily lead to energy waste where users leave while the air conditioning is still running as usual.

3. After entering the room, people always set the air conditioning settings very low or very high in order to cool or heat quickly. However, when the temperature reaches too low or too high, they do not restore the settings to the normal values, resulting in a large amount of energy consumption. If personnel have a weak awareness of energy conservation and open windows to dissipate heat when it is too cold or too hot, the energy consumption will be even more astonishing.

4. During seasons when air conditioning is not needed, as well as special periods such as after work, weekends, holidays, etc., the air conditioning can be set to a mode where it is not turned on.

5. Some individuals excessively pursue comfort, operating the air conditioning at 16 ℃ for cooling in summer and 30 ℃ for heating in winter, resulting in high energy consumption and loss of comfort.

6. Quantification of energy-saving issues by responsible parties. No measurement, no quantitative indicators, unclear responsible parties, and lack of energy-saving measures.

7. Due to excessive use of air conditioners, their lifespan is reduced.

economic benefits

1) Time period control can solve the problem of forgetting to turn off the air conditioning after work by setting allowed and prohibited time periods. It can also solve the problem of not being allowed to turn on the air conditioning directly during certain seasons (spring and autumn) and special weekend periods.

2) Control of temperature limits; When people use air conditioning, they often set the temperature to 16 ℃ for cooling and up to 30 ℃ for heating in order to quickly reach the desired comfortable temperature. However, due to negligence, the air conditioning operates under high load for a long time. The purpose of temperature control is to set a temperature limit for cooling and heating, such as setting the cooling temperature to 24 ℃ and the maximum heating temperature to 20 ℃, in order to achieve energy conservation.

Management efficiency

1) Real time remote transmission and monitoring of system operation data, comprehensive monitoring of air conditioning system operation, and timely handling of abnormal opening and faulty air conditioning.

2) Implement statistics, analysis, and management of energy data and energy consumption indicators to achieve energy consumption curves.

3) Set automatic start stop schedule tasks and startup modes to achieve timed automatic start stop.

social benefits

1) Actively respond to the national call for energy conservation and emission reduction, achieve the national energy conservation and emission reduction goals, and establish a conservation oriented society.

2) Reduce energy consumption per unit area of buildings, decrease CO2 emissions, and improve the climate and environment.

3) Through air conditioning control, in response to the national regulation that the air conditioning temperature in public buildings should not be lower than 26 ℃, the national policy is implemented in practice.

control scheme

Using centralized management as a means and energy conservation and emission reduction as the direction, a central air conditioning multi split control scheme is adopted to remotely control and collect data from 35 external units and 466 internal units in a certain building through RS485 communication and Ethernet. The real-time operation status of each air conditioning equipment is viewed, and remote mode switching functions such as on/off, temperature rise/fall, and cooling/heating are achieved to solve the problems of difficult centralized control of central air conditioning and human energy waste. This further improves the intelligent management level of air conditioning, realizes energy-saving management of air conditioning equipment, and creates benefits for management.

Control Theory

The intelligent collector sends the collected air conditioning data to the intelligent host, which uploads the data information to the cloud. The intelligent host can also issue air conditioning control commands from the top layer of the cloud, which first pass through the intelligent host and then be sent to the corresponding collector module. Finally, the collector connected to the air conditioner realizes intelligent control of the indoor unit.

Intelligent control of multi split air conditioning systems can be achieved through local area network servers or computers. Based on monitored indoor temperature, air conditioning operation status, and other information, remote intelligent energy-saving control and management of the air conditioning in the monitored room can be carried out. The indoor air conditioning temperature can be reasonably controlled to provide good indoor air quality, making traditional air conditioning more energy-efficient, intelligent, and comfortable.

Based on a distributed architecture, administrators can log in to the control system through a browser and set the indoor units of any one or multiple units based on user needs, including startup, temperature, mode, and other settings.

The air conditioning operation data collected by the intelligent collector and the energy consumption and electricity collected by the electricity meter are transmitted to the system management platform through the intelligent host. The control commands issued by the platform are sent to the intelligent collector through the intelligent host to control the air conditioning status, responsible for data aggregation, storage, and control instruction issuance.

System functions

real-time monitoring

Real time remote monitoring of the status of each air conditioner can be achieved through a software platform, allowing for remote viewing of the air conditioner's status, operating speed, mode, timing, set temperature, and current temperature.

Local control and remote control

This system can remotely control various air conditioners through the platform, achieving remote settings such as wind speed, temperature, mode, and timing. At the end of work, management personnel can use this function to turn off the air conditioning that office staff forgot to turn off, achieving the goal of energy-saving management. During work hours, management personnel can remotely check whether each office has adjusted the air conditioning to the appropriate temperature according to regulations. If it does not comply with relevant national regulations, it can be remotely adjusted to achieve energy-saving goals.

Temperature management

1) Energy saving temperature during startup: When timed/manually turned on, the default preset temperature value is set, and remote setting of energy-saving temperature value is supported.

2) Limited operating temperature adjustment range: The temperature in cooling/heating mode is only adjusted within the preset temperature range, and the temperature adjustment range value can be remotely modified; If there is any user violation, the temperature will be automatically corrected.

time management

1) Scheduled automatic shutdown, multiple shutdown time points can be set daily.

2) Remote power on/off.

3) In special circumstances, support remote control of air conditioning on/off status in the background.

4) Schedule management, view historical on/off records.

Permission settings

1) Grouping can be used to set permissions for specific groups.

2) Lock the air conditioning panel/remote control, i.e. disable the remote control.

3) There are two modes for setting the air conditioner to automatically turn on or manually turn on when it is powered on.

Main hardware of the system

Intelligent communication network shutdown

QT290G is a standard LoRaWAN ™ Indoor gateway of the protocol. It can connect to standard LoRaWAN terminals for bidirectional communication, and connect to the company's NS (network server) through a standard Ethernet interface. It can be extended to support 4G/LTE for data upload, and locally supports IP/WiFi AP web configuration of the gateway's working frequency and related parameters such as the network server it points to.

Based on industrial grade hardware platform design, all metal shell, supporting PoE/DC12V power supply, with the characteristics of long coverage distance, low power consumption, and simple operation and maintenance. Allow access to various LoRa application nodes.

Air conditioning panel thermostat

An intelligent LCD digital constant temperature controller based on LoRaWAN, suitable for temperature control of fan coil units, electric valves, electric air vents, underfloor heating, wall mounted boilers, water heaters, and heating equipment. Adopting a large screen LCD display, the air intake of the heating and cooling system is automatically adjusted, and the pipeline electric valve is opened or closed to maintain a constant temperature indoors. The air conditioning panel can be directly connected to the indoor unit without the need for external power supply or any adapter devices. It can replace the original line controller or be used in conjunction with it, and the control will synchronize with each other.

Energy saving control of air conditioning units

Air conditioning system regulation

The central air conditioning system mainly consists of a cold and heat source host system (also known as a "refrigerant circulation system"), a chilled water circulation system, a cooling water circulation system, and multiple air conditioning systems (also known as "terminal air conditioning box systems").

The main control components include five parts: (1) refrigeration host (2) chilled water pump (3) cooling water pump (4) cooling tower (5) terminal air conditioning unit

Air conditioning host access: Each chiller unit corresponds to a communication control board with standardized demand response communication function, and each communication control board is uniformly installed in the chiller unit operation panel box. According to the space inside the operation panel box of the chiller unit, install the communication control board reasonably, and flexibly install it according to the size and fixing method of the box and communication board. If there is no remaining space inside the original control panel box, a customized communication control board installation cabinet is required for the installation of the communication control board.

Monitoring and control of chilled water system: Install temperature sensors in the chilled water outlet and return pipelines to collect the temperature difference between the chilled water outlet and return. Install an edge controller cabinet in the chilled water system to collect data such as water temperature from sensors, as well as operating status parameters of the chilled water pump and chilled water host. Optimize and control the host and chilled water pump through the built-in local strategy in the control cabinet to achieve automatic variable frequency operation of the chilled water pump tracking the temperature difference between the chilled water outlet and return. Regulation method: Based on the temperature difference between the supply and return water of the chilled water system, match the required cooling capacity of the system and adjust the frequency of the chilled water pump; Match the optimal operating efficiency curve of the chiller unit and adjust the number of chiller units in operation.

Monitoring and control of cooling water system: Install temperature sensors in the cooling water outlet and return pipes to collect the temperature difference between the cooling water outlet and return water; Select a suitable location, install outdoor temperature and humidity sensors, and achieve outdoor temperature and humidity collection; Install an edge controller cabinet in the cooling water system to collect operational status information of the cooling water pump and cooling tower fan, and finely control the cooling tower fan through a logic control program to achieve intelligent grouping control of the cooling water pump start stop and cooling tower cooling fan. Regulation method: Based on changes in parameters such as the supply temperature, return temperature, and outdoor temperature and humidity of the cooling water system, the required cooling capacity of the system is matched, and the number of cooling tower fans is adjusted to reduce the energy consumption of the cooling system.

Monitoring and control of the end air conditioning unit system: A temperature sensor is installed on the return air duct of the end air conditioning unit to achieve real-time collection of the ambient temperature in the area and calculate the required cooling capacity at the end. Install an edge controller cabinet for the terminal air conditioning unit, and regulate the opening degree of the electromagnetic valve of the terminal air conditioning unit through a logic control program to achieve matching adjustment of the terminal cooling capacity and reduce energy consumption. Regulation method: Based on the temperature of the air outlet in the corresponding area of the end air conditioning unit, identify the end cooling demand, and adjust the cooling capacity of different areas by controlling the opening of the solenoid valve to achieve matching of cooling capacity in different areas, thereby reducing unnecessary waste of cooling capacity.

Sub item measurement of electricity information

A certain number of measuring instruments need to be installed on the central air conditioning side to obtain information on the power consumption and load of relevant electrical systems and equipment. The required data mainly includes: total electricity consumption and load of users, total electricity consumption and load of central air conditioning system, and power distribution and load of central air conditioning system equipment. In order to ensure the collection requirements for measuring the total electricity consumption of users, the total electricity consumption of the central air conditioning system, the total electricity consumption of the lighting system, and the power consumption of the central air conditioning system equipment, the collection of electricity information is carried out according to a three-level measurement method.

First level measurement. The primary measurement is mainly used to obtain the total electricity consumption information of users, including the total electricity consumption and total electricity load of users. If the user's building control system has covered all its transformers, the data of primary measurement can be directly obtained through system integration.

Secondary measurement. The secondary metering mainly obtains the total electricity consumption information of the user's central air conditioning system. The total electricity and load of the central air conditioning system are mainly obtained by the sum of the electricity consumption information of the air conditioning host, chilled water pump, cooling water pump, cooling tower, and end equipment. If the user's building control system has covered all equipment of the central air conditioning system, relevant data can be obtained directly through system docking. If not covered, complete the equipment sub item measurement and sum it up.

Third level measurement. The three-level measurement mainly obtains equipment level electricity consumption information under the user's central air conditioning system, and the measurement implementation content is shown in the table below.

System Interface