Application of natural gas generators in communication base stations

At present, the backup power supply of communication base stations mainly relies on small air-cooled diesel generators, whose main fuel is diesel. There are many inconveniences in the use of diesel, such as heavy weight, loud noise, and difficulty in starting. The noise is mainly low-frequency noise with strong penetration. When the engine runs for a long time, the temperature and pressure are high, and more soot and carbon deposits will be produced in the cylinder. The engine oil is also easily oxidized to produce colloid, which requires a lot of maintenance work and frequent maintenance. The exhaust gas contains a large amount of CO, soot and nitrogen oxides, and the particles of the emissions are large, so it is easy to produce "black smoke".

Compared with diesel generators, natural gas generators can overcome many shortcomings of diesel generators, such as good noise reduction, clean combustion of gas, less impurities; uniform and gentle power, longer service life of parts, and exhaust gas will not form oil accumulation in equipment and machine rooms. It is a recognized green energy. The fuel itself is gas, which does not need to be vaporized before combustion, will not adhere to the combustion chamber and spark plug, has no carbon deposits, and will not pollute lubricating oil, reducing daily maintenance and maintenance costs. Therefore, natural gas generators have broad application prospects in communication base stations.

1 Working principle of natural gas generator

The natural gas generator system is based on the gasoline generator system, with gas input into the engine cylinders through a dedicated gas channel, so that the engine works to drive the generator to generate electricity.

The natural gas power generation system is fixedly installed in the mobile communication base station, using gas to generate electricity, and automatically supplies three-phase power to the base station equipment based on intelligent judgment of whether the city power is available or not. The entire system forms a relatively closed self-circulating system through the air inlet and exhaust outlet, which has no effect on the air and temperature in the base station.

2 System composition of natural gas generator

The system is mainly composed of a gas generator host, an automatic control system, a silent vibration reduction system and a gas system.

2.1 Gas-fired power generation unit

The working principle of the gas generator is the same as that of the gasoline generator. After the reliability and performance improvement, the fuel is changed from gasoline to natural gas, which uses the mature and stable internal combustion engine technology. The generator outputs stable and reliable AC power, and the steady-state regulation rate and fluctuation rate of voltage (frequency), line voltage deviation under asymmetric load, line voltage waveform sine distortion rate, transient voltage (frequency) regulation rate and stabilization time all meet the national standard requirements.

2.2 Automatic control system

It is equipped with an automatic control system that can monitor the working status of the unit in real time, truly realizing unattended operation of the machine room.

In addition to cooperating with the combustible gas sensor in the box, the automatic monitoring system can also cooperate with the combustible gas sensor installed indoors to transmit alarms to the automatic control box, and then cut off the gas pipeline, lock the unit operation, and ensure the overall safety of the machine room; at the same time, the automatic monitoring system cooperates with the temperature sensor and oil level sensor in the box to closely detect the operation status of the unit; when the temperature exceeds the safety setting value, the unit operation is directly stopped, locked, and the gas pipeline is cut off. It can be managed by the mobile operation and maintenance management center through the RS222 interface, and the operation status of each base station unit can be centrally monitored, including: voltage, current, frequency, temperature, gas, oil level and other signals and alarm information, and the center can directly remotely control the start and stop of the unit as needed.

The automatic control system can realize the following safety protection functions: overvoltage protection, undervoltage protection, overload protection, frequency protection, gas leakage protection, chassis temperature protection, low oil level protection and cooling water temperature protection.

2.3 Silent vibration reduction system

The silent vibration reduction system includes a silent vibration reduction chassis and inlet and outlet silencers. The silent system greatly reduces the mechanical noise of the engine, and combined with the silent vibration reduction chassis and large air duct silencer, it meets high quietness requirements.

When using the enhanced configuration, the noise can be as low as 45db, meeting the requirements of various environments.

2.4 Gas system

The gas system is mainly composed of gas storage tanks and gas control components. In recent years, the mature gas cylinder storage technology has created basic conditions for the promotion of natural gas generators. At present, the use of gas cylinders should comply with national safety standards.

2.5 Usage Model of Natural Gas Generator

The natural gas generator is used in a fixed installation mode at the communication base station. The generator outputs AC power and is connected to the existing base station AC input distribution box. In the event of a power outage, the battery is used first. When the battery is discharged to a certain level (through voltage detection), the natural gas generator automatically starts to generate electricity. After starting, the generator can carry all the electrical equipment in the base station.

The automatic control system of the natural gas generator itself has an RS222 intelligent output interface, which can be directly connected to a complete and mature monitoring network. The monitoring center can read various operating data and status of the natural gas generator, such as voltage, current, frequency, temperature, gas, oil level and other signals and alarm information.

The natural gas generator is fixedly installed in the base station and can be considered for application in the following occasions:

a. Portable diesel generators cannot enter areas where power is generated.

b. Areas that are sensitive to noise from portable diesel generators.

c. Base stations that are far away from the power generation support center.

d. Base stations with a high number of power outages per year and a long single power outage duration.

e. Base stations with important geographical locations where roads are often closed due to major events.

3. Cost Analysis of Natural Gas Generator Sets

Taking a 10kw generator as an example, the use cost of a natural gas generator and an ordinary diesel generator is analyzed. The purchase cost of a 10kw ordinary diesel generator is 24,000 yuan. The initial cost is low, but the subsequent maintenance cost and use cost are high. Every power outage requires manual on-site power generation. The cost of power generation is the sum of the labor cost and the power generation cost. Even if the power is only generated for 10 minutes, labor costs need to be paid. For natural gas generators, only when the gas is exhausted, the gas tank is replaced manually. Due to the long ventilation interval, the labor cost can be greatly reduced. Table 1 and Table 2 compare the two power generation methods under Class III and Class IV mains.

With a total of 29 days of power generation per year, the investment can be recovered within 5 years.

The above power outage times and durations are calculated under a fixed model. If the number of power outages per month is greater than the assumed number in the above table, and the power outage duration remains unchanged, the cost recovery period will be greatly shortened.

Natural gas generators are environmentally friendly generators. The above cost recovery is the actual expenditure cost of the user unit. However, as the concept of energy conservation and emission reduction becomes more popular, the social value of natural gas in reducing atmospheric pollution is immeasurable. Table 3 shows the comparison of pollutant emissions.

Since the social cost of waste gas treatment cannot be calculated, the pollutant emission part is used as a reference.

4 Conclusion

The use of natural gas generators is only one aspect of the cost analysis. Since the power generation is unattended, unattended power generation is particularly necessary in certain specific situations, such as when landslides occur and personnel cannot enter; when a large-scale power outage in an area requires a large number of generators, but there are not enough personnel. Therefore, in some important base stations, such as tourist routes, national trunk transmission base station nodes, and noise-sensitive areas, installing natural gas generators should be an alternative.

With the promotion of natural gas generators, their prices will inevitably drop further and the cost recovery period will be greatly shortened.