Building electrical energy saving technology

date: 2018-08-22
Times of browsing: 39

Building electric energy conservation design should first follow the three principles.

(1) meet the functions of the building

It meets illumination, color temperature and color index of lighting;Meet the temperature and fresh air volume of comfort air conditioning, that is, comfort and hygiene;To satisfy the upper and lower, left-right transport channels unimpeded;Meet the special technical requirements, such as some electrical facilities in entertainment, technical lighting in exhibition hall and electric power.

(2) consider the actual economic benefits

Energy conservation should take into account national conditions and economic benefits, and should not consume too much investment and increase operating costs due to energy conservation.Instead, the increased investment should be recycled in a few years or less with energy-saving benefits.

(3) save energy spent unnecessarily

The focus of energy conservation should be to save unnecessary energy.Find out where the energy consumption has nothing to do with the function of the building, and then consider what measures should be taken to save energy.For example, power loss of transformer and active power loss of transmission power line are useless energy loss.Such as large and wide lighting capacity, to use advanced technology to reduce its energy consumption.Therefore, energy-saving measures should also implement the principles of practicality, economic rationality and advanced technology.

Then, the energy-saving technology of building electricity is analyzed from several aspects.

I. load calculation

Load calculation is the basic work of electrical design. If the load calculation is not accurate, it will not only cause unreasonable equipment selection, but also the power supply and distribution system operation will have security risks.In actual projects, too much load calculation is often found, which directly leads to too large primary investment and high operation cost.

The density method is generally used in the load calculation in the planning stage.The unit index method is generally used in the load calculation at the design stage.The demand coefficient method is generally used in the load calculation of construction drawing design stage.

The load index of the planned unit construction land is shown in table 1.

Table 1 load index of construction land of planning unit

1. The JPG

The load index of planned unit building area is shown in table 2.

Table 2 load index of planning unit building area

2. JPG

The electricity consumption indexes of various buildings are shown in table 3.

Table 3 power consumption indicators of various buildings

3. The JPG

The demand coefficient and power factor of electrical equipment are shown in table 4.

Table 4 demand coefficient and power factor of electrical equipment

4. JPG

Improve the power factor of the system

Increasing the power factor can bring considerable benefits to energy saving. The smaller the power factor, the smaller the actual active power output of the transformer.

The actual output power of transformer is in linear decreasing relation with power factor.When the power factor is 0.9, the actual output of the transformer is reduced by 10%.When the power factor is 0.8, the actual output of the transformer is reduced by 20%.When the power factor is equal to 1, the output power of the transformer can reach the rated capacity.

Therefore, the transformer capacity, cable and laying method should be reasonably selected to reduce the line inductance to improve the user's natural power factor.Reactive compensation should be carried out when the natural power factor improvement measures still fail to meet the requirements.The reactive power compensation of 10kV and below should be concentrated on the low-voltage side of the distribution transformer, and the power factor should not be lower than 0.9. the power factor index of the high-voltage side should conform to the regulations of local power supply department.

Capacitors can be installed at the following capacity:

1) 35kV substation can be calculated as 10%-30% of transformer capacity.

2) 10kV and 20kV substations can be calculated as 20% ~ 30% of transformer capacity.

Reduce transformer loss

Amorphous alloy iron core transformer is characterized by low noise, low loss and so on. Its no-load loss is only one fifth of that of conventional products, complete sealing is free of maintenance and operation cost is extremely low.Select energy saving type transformer, replace or transform high energy consumption transformer.SL7, S9, SC(B)9, SGB10, sgb11-r and other types of energy-saving transformers should be used in new or reconstruction projects.Compared with the traditional product, SL7 without excitation voltage regulating transformer, the no-load loss and short circuit loss of 10kV series are reduced by 41.5% and 13.9% respectively.Compared with SL7 series transformers, the no-load loss and short circuit loss of S9 series transformers were reduced by 5.9% and 23.3% respectively.Compared with SC(B)9 series transformer, sgb11-r series coil core dry transformer has a 40% reduction in no-load loss and a 70% ~ 85% reduction in no-load current.Compared with SGB10 series transformer, no-load loss is reduced by 24% and load loss is reduced by 11.7%.The S11 series are low loss transformers widely used at present. The no-load loss is about 75% lower than the S9 series, and the load loss is equal to the S9 series transformers.

When the load rate of transformer is low, the loss of transformer takes a large proportion and the efficiency of transformer is low.The load rate of transformer is between 40% and 70%, its efficiency is the highest and its loss is the least.When the load rate is too high, the loss increases obviously.

Energy saving design of power distribution lines

Reducing line loss of power supply and distribution line is an important index of economic operation of power supply and distribution line.In specific projects, the current on the line is generally constant, so to reduce line loss, can only reduce the line resistance.

1) select wire with low resistivity as far as possible, such as copper conductor wire is better, followed by aluminum wire.

2) reduce the length of the wire as much as possible. In the design, the line should take straight lines and less detours. In addition, in the low-voltage power distribution, it should not take or go back.The substation should be as close to the load center as possible to reduce the power supply radius.

3) increase the cross section area of the conductor. For longer lines, increase the first-level line section when the line section is selected, on the premise of meeting the requirements of load flow, thermal stability, protection coordination and voltage drop.This increase in line costs, due to the savings in energy consumption and reduce the annual operating costs, a comprehensive consideration of the economy is cost-effective.

Energy saving of electric lighting

Halogen tungsten lamp and incandescent lamp have low light effect, short life and low comprehensive energy efficiency.High - pressure sodium lamp, three - color fluorescent lamp and high - frequency anode lamp have higher comprehensive energy efficiency and should be popularized.

Compared with the crude tube fluorescent lamp, the fine tube fluorescent lamp has incomparable advantages in terms of luminous efficiency and mercury consumption.The light efficiency of long tube fluorescent lamp is about 17% higher than that of short tube fluorescent lamp.

Because open type lamps and lanterns does not have block, the light energy that lamps and lanterns gives is more, its efficiency ought to be highest.If the dazzle, beautiful, and safe can meet the requirements, as far as possible, open lighting.

For high intensity gas discharge lamps for sports lighting, metal halide lamps are usually used, and the luminaire efficiency is recommended not less than 70%.

Using the intelligent lighting energy saving control system to control the lamps can achieve remarkable energy saving effect.Intelligent lighting control system is a standard local area network of bus type.It is composed of system unit, input unit and output unit.All the unit devices (except power supply) have built-in microprocessors and storage units. The control devices are connected by a five-class data communication line (or optical fiber) to form a "hand holding" network.In addition to power equipment, each unit is provided with a unique address and its function is set by software.The advantages of intelligent lighting energy-saving control system are as follows:

1) the lighting facility control system can be reasonably managed, and the intelligent clock manager can be used to set the lighting level in advance according to the operating conditions of various functional areas at different dates and times. When lighting is not required, the lamp should be turned off;In most cases, many areas do not actually need to turn on all the lights or on to the brightest. The lighting control system can provide the most comfortable lighting with the most economical energy consumption.In some public areas, such as meeting rooms, restrooms, etc., use the dynamic and static detection function to turn on the lights or switch to some preset scene when someone enters.

2) the intelligent lighting control system can automatically adjust the illumination by making full use of the outdoor natural light. Only when necessary, the lamp can be lit to achieve the required brightness. The energy-saving effect is very obvious.

3) the intelligent lighting control system can successfully suppress the impact voltage and surge voltage of the power grid, and artificially determine the voltage limit through the system to improve the lamp life.Soft start and soft turn off technology is adopted to avoid the thermal shock of lamp filament caused by current when the lamp is opened.

Energy saving of fans and pumps

In civil buildings, fans and pumps are one of the most used power equipment, and their energy saving is of great significance.

The shaft power of the fan and pump is directly proportional to the third square of the rotating speed.If the rotating speed remains unchanged, the shaft power of the fan and pump is directly proportional to the wind pressure and pump head.Therefore, from the perspective of energy saving, when the flow rate of the fan or pump needs to be changed, the conventional method of changing the opening of the damper or valve should not be adopted for regulation, but the method of changing the motor speed should be adopted to adjust the flow rate to achieve the purpose of energy saving.When the speed is reduced to half of the rated speed, the actual power is only 12.5% of the rated power. The energy-saving effect is considerable.

The speed regulation method of ac asynchronous motor is as follows:

1) change the stator frequency of the ac motor.

2) change the log of motor magnetic poles.

3) adjust the slip rate of the induction motor.

The specific methods of speed regulation include variable pressure, electromagnetic slip clutch, doubly-fed motor speed regulation, logarithm of changing pole, variable frequency and variable pressure, etc.

The adjustment method of water pump and fan system depends on the change law of working flow;The proportion of static head of pipeline performance curve to total head;The size of the pump or fan capacity;Price, reliability, efficiency and power factor characteristics of the regulating device.Select the most appropriate adjustment method after comprehensive measurement, and make comprehensive economic and technological analysis and comparison when necessary.

Elevator energy saving technology

Energy saving technology of elevator power system can be realized through elevator regeneration energy feedback, and the mechanical energy of the load in motion can be transformed into electric energy through frequency converter and sent back to the ac grid, or to other power equipment nearby, so that the motor drive system can consume electric energy of the grid in unit time.Most ordinary frequency converters use diode rectifier bridge to convert alternating current into dc, and then use IGBT inverter technology to convert direct current into voltage and frequency adjustable ac.The converter can only work in the electric state, so called a two-quadrant converter.Because the two-quadrant converter USES a diode rectifier bridge, it cannot realize the two-way flow of energy, and there is no way to send the energy of the motor feedback system back to the grid.In some applications, such as elevator, lifting equipment and centrifuge system, only the resistance brake unit can be added to the frequency converter in the second quadrant to consume the energy feedback of the motor.

IGBT power module can realize two-way flow of energy. If IGBT is adopted as the rectifier bridge, SPWM control pulse is generated by DSP with high speed and high calculation capacity.On the one hand, it can adjust the input power factor, eliminate the harmonic pollution to the power grid, and make the frequency converter truly green.On the other hand, the energy generated by the motor feedback can be sent back to the power grid for energy saving.

Energy saving control scheme is as follows:

1) the electric energy generated by the motor is not generated by resistance thermal energy, but distributed to other electric elevators reasonably through the parallel control system of the electric energy on the dc side, so as to realize the purpose of energy saving.

2) when the power generation energy is excessive, the electric energy generated by the motor is not through the resistance heat consumption, but through the rectifier inverter to feed back to the grid.

3) when the total power consumption of the elevator is greater than the total power generation at a certain time, the direct current energy parallel control scheme is adopted, and only when the energy surplus is controlled in parallel at the dc side, the feedback control is adopted.

4) when one elevator is in the energy feedback state, the rectification function of all other elevators stops, that is, the rectification and feedback cannot be carried out at the same time to avoid circulation.

5) when the control system fails or an emergency occurs, the controller can be cut off so that one or several elevators can operate independently. At this time, the dc side of the elevator frequency converter is no longer parallel, and the electric energy generated by the elevator braking is directly feedback to the grid.

Of course, the electric power generated by the elevator braking must meet the requirements of state grid before it can be connected.

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