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Basic Principle of MaxSaver Energy Saving System |
This ES system is an intelligent system which applies many technologies, such as the intelligent data gathering technology, microprocessor technology, PLC control technology, motor parameters auto-measurement technology and variable frequency technology. Based on the gathered data, such as operation temperature, pressure and water discharge of central air-condition, and reference parameters, such as height, direction, material and heat load of the buildings and user habit, the optimal operation mode of energy is established by using special ES intelligent control program. It can track the variable load automatically, forecast the dynamic state, adjust the parameters in advance and optimize the system in real-time. The output power curve is close to the power curve needed by the real load to the most extend at the instance of meeting the need of system |
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Operation Power Curves under Different Control Modes
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Energy Saving Theory of Water System (Chilling Pump, Cooling Pump, Cooling Fan)
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Due to the phenomenon of “big stream, small temperature difference” in cold water system of central air-condition, the energy saving is feasible. The reasons which cause the phenomenon are:
Margin of the chiller plant design: value of cooling is decided by the product of maximal cooling load and coefficient of 1.1-1.5. The coefficient varies with the types of building.
Water discharge is designed by the maximal cooling load (maximal load in one year) and the temperature difference of 5 degree C between entering water and return water. Actually, the time in which the system operates in the maximum load is no more than 10-20 days in one year. In most time, the system operates in partial load.
Pump routing is based on the product of farthest route, most resistance and some safety coefficient. According to the designed water discharge, the type of water pump is selected by the rated parameters labeled on the nameplate and is not selected by the power curve. So, when the water pump works, the operation point is at the right side of the real operation point and the real water discharge is 20%-50% times larger than the designed water discharge. In water pump, the relationships between the water discharge Q, pressure P, rotation speed n and output power N of motor are:
The water discharge Q is changed by the change of rotation speed n of motor, so the output power N of the motor is changed. If 40% energy is saved, rotation speed of water pump is decreased to 84% rated rotation speed and water discharge is 84% rated rotation speed. Water discharge is still in the scope of the designed water discharge and the cooling effect is not affected. |
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Energy Saving Theory of Main Air-condition System |
When the ambient temperature is constant and the terminal load of air-conditioning is variable, the load of central air-conditioning must vary with the terminal load. In the normal operation conditions, the energy of main air-conditioning could adjust by itself (realized by adjusting the cold/hot water discharge) because the chilling water discharge, cooling water discharge and cooling air flow rate are constant. But the optimal operation point could not be obtained, much energy is wasted. It is important to control the water discharge rate and flow rate capacity.
Energy of main air-condition is transferred and transported by chilling water. The output energy control of main air-conditioning is realized by controlling the water discharge, temperature and temperature difference of chilling water. Because the load and temperature of cooling water would affect the operation efficiency of central air-conditioning, adjusting the water discharge of cooling water and air flow capacity of cooling tower reasonably will make the operation temperature of heat converter optimal and the main air-conditioning save energy. |
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Flow Chart of MaxSaver |
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MaxSaver–Well-designed, Safe and Environmentally friendly |
Imports of special frequency conversion devices and accessories are adopted in the system which meets the need of safety standard of Hong Kong and the system life extends to 15 years.
Special data processing mode, perfect program mode and auto-optimized energy consumed combination cause the optimal energy saving effect. Many protection functions, such as the soft startup protection, are included in the system. |
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Energy Saving Effect of MaxSaver
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Major Idea: safe and refrigeration are not affected
More than 40% energy saving for water pump, fans
Operation states of main air-condition are optimized, which will decrease the consumed energy up to 10%. Total consumed energy of central air-conditioning system is decreased to 15%-30% |
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Key Strengths of MaxSaver |
1、Design Plan of Electric Device
Operation frequency and energy saving circuit are locked each other.
Energy saving (ES) devices is connected to the normal system in parallel.
One ES device could be alternatively switched between two water pumps.
One set of ES devices could do the energy control to many host computers.
Measure correctly the load of water system.
Intelligent system could monitor the ES devices.
ES devices are installed with the optimal economic operation scheme.
2、Introduction to ES function of MaxSaver
One set of ES devices could do the energy control to many host computers.
ES devices of cooling pump could be alternatively switched among many cooling pumps.
ES devices of chilling pump could be alternatively switched among many chilling pumps.
Selection switches “OS/ES” exist in the control panel of ES devices. When the switch “OS” is selected, ES circuit is locked, whereas the OS circuit is locked.
Water pumps “1#/2#” could be selected in the control panel of ES devices. When the ES mode is selected, if the 1# water pump is selected, the control plant of ES control is 1# pump; If the 2# water pump is selected, the control plant is 2# water pump.
Selection switches “Auto/Manual” exist in the control panel. When the switch “Manual” is selected, ES devices are started/stopped by operation the button on the panel. When the switch “Auto” is selected, ES devices are started/stopped by the remote BAS signal.
The button “Load Adjust” is used in the control panel. When “Load Adjust Ratio” is set, if the load is heavy, the mode of ES devices can be changed from “ES” to “OS” mode automatically and if the load is light, the mode will be changed to “ES” again.
Fault output point of ES devices is connected to that of OS devices in parallel. If the ES devices have a screw loose, the fault information could be obtained in long/near distance.
Operation state signals for running and stopping of ES devices are connected to that of OS devices in parallel. The operation state signals for running and stopping of the ES devices could be obtained in long/near distance.
ES devices have protection functions as over-voltage protection, over-current protection and fault to ground protection.
ES devices have protection functions as chilling water with low water discharge and low temperature, cooling water with high temperature.
3、Monitor Function
Operation, stop, fault and maintenance signal of chilling pump and cooling pump.
Temperature signal of water system in main air-cooling system.
Operation current, frequency, rotating speed and power factor of motors.
Accumulative total operation time and electricity used of ES devices
4、Monitor Function of Main system
Operation, stop, fault and maintenance signal of host computer, chilling pump, cooling pump and fan
Temperature, pressure and discharge of water system
Operation current, frequency, rotate speed and power factor of motor
Accumulative total operation time and electricity usage of ES devices
Load-power curve of ES devices
Dynamic plot of main devices
5、How to choose the control parameters of MaxSaver Two circular water systems, chilling circular water and cooling circular water, take charge the external heat exchange of the central air-condition system. The optimal ES effect and refrigeration effect could be obtained, if only the control parameters of these two water systems are selected logically. |
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Entering water temperature of condenser of main air-condition is adopted as the control parameter in cooling water system. |
nReturn water temperature could response the heat of chilling air-conditioning machine and cooling effect. Define the temperature difference between return water and supply water is △t. If △t is higher, the heat caused by main air-conditioning is more. The rotation speed of condersing pump must be increased, which will increase the circulation speed of water system. Whereas the circulation speed of water system would be decreased by decreasing the rotation speed. The real experiment results make sure that △t is defined in the scope of 3～5℃ is reasonable.
nBecause the entering water temperature varies with the ambient temperature, the constant value is fixed to difference temperature △t is not feasible. When the variable frequency adjusting speed system is adopted, not only the cooling effect, but also the ES effect is concerned. That means △t defines lowly, the average rotation speed of water pump is increased, which will affect the ES effect. If △t defines highly, the cooling effect will be affected in the higher input water temperature. So, the value of △t is real-time adjusted by supply water temperature is advisable.
nThe temperature difference △t is controlled by measuring the supply water temperature, which will make the ES effect and cooling effect optimal.
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Return water temperature of evaporator of main air-conditioning is adopted as control parameter in chill water system. |
The reasons are:
Supply water temperature of chilling water which is the effect of chill water pumps is constant. So, return water temperature could response the ambient temperature. Return water temperature is high which means the ambient temperature is high. The rotation speed of Chilling pump is increased in order to increase the circulation speed of Chill water. Whereas the circulation speeds of Chill water is decreased in order to save energy.
If the pressure difference between return water pressure and supply water pressure is adopted as the control parameter, two problems exist:
The change of ambient temperature is not considered
If the pressure difference is constant, the Supply power P of circulating water is in proportion to flow rate and the rotational speed. |
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