In small wind power equipment, the battery is one of the important auxiliary equipment. The battery plays an important role in storing the power and stabilizing the voltage in the DC power supply system.
First, determine the battery capacity
Whether or not the battery capacity is configured properly affects the technical and economic indicators of wind power generation. The capacity of the election is small, and the excess power generated when windy is not fully stored. The capacity selection is too large, one increases investment; two batteries may be in a state of unsatisfactory charging for a long time, which will affect the efficiency and service life of the battery. Table 1 shows the investment of batteries in wind power generation equipment.
The general conventional charging is "two-phase constant-current charging". This method does not waste power and the charging time is short, which is beneficial to prolonging the service life of the battery. It is also much easier to calculate the battery capacity. In the case of wind power, it is different from conventional charging.
Because the wind speed often changes, the output current of the motor is large or small, sometimes it is not, so that the battery charging current and the required charging time are difficult to determine. For this practical situation, we use the following two calculation methods to determine the battery capacity configuration. The
1. Battery balance calculation method.
The calculation steps are as follows:
a. According to the wind speed data provided by the local meteorological department, the wind speed from the initial working wind speed of the wind turbine to the different wind speeds within the shutting wind wind range is counted from ten days to one hour.
b. According to the P=f(V) characteristic curve and wind speed data of the selected wind turbine, the amount of electricity that can be emitted by the Taiwan-based machine can be calculated, and its annual power production curve is plotted. Figure - Based on the wind speed data of Neimengqian Rear Banner, the annual power generation process line of the Shangdu Animal Husbandry Plant ED1.5~100 is drawn. It is calculated that the machine generates 276 degrees of electricity annually under local wind conditions. From the process line, it can be seen that the electricity production varies greatly from ten to ten days at the end of April, and it is only 0.95 degrees at the end of February and the difference is nearly 20 times. This shows that it is necessary to configure storage batteries for energy storage adjustment.
C. Based on the telecommunication conditions, calculate the ten-year electricity consumption and give the annual electricity consumption process line. The dashed line in the drawing shows.
d. Comparing the power generation amount and the power consumption process line, the required battery capacity is determined by the amount of power that generates less than the maximum power consumption difference period (the oblique part in the figure). The largest difference in the figure is 2.3 degrees. Need to configure 2300 volt-hour battery, the actual choice of 12 volt 48 Ah battery 4 pieces. The total capacity is 2304 VA.
2. Empirical calculation
Based on our pilot experience, under the wind conditions in Chayouhouqi and Shangdu areas, the following formula can also be used to easily estimate the required battery capacity. In the formula:
Q - required configuration of battery capacity (Ah);
p - load power (watts);
t - the number of daily electricity hours;
U - standard battery voltage (usually 12 volts);
n - the battery reserve cycle coefficient; (determined according to the wind conditions, generally take 3 to 8 days)
K——discharge control coefficient (take 0.75-0.8)
The formula above considers: (1) the rated power of the electrical equipment, (2) the local meteorological conditions, that is, the average time of the wind-free period. (8) To prevent the battery from being over-discharged, the discharge should be controlled to a certain extent.
Still taking Chayouhou Banner as an example, a 100 watt machine is installed to supply electricity to 3 households. Each household is equipped with 12 volt 15 watt bulbs. The average 2 lamps are lighted for 5 hours per day to calculate the required battery capacity. (Reserve coefficient takes 6 and discharge control coefficient takes 0.8) Substitute into the formula:
Choose 6 l 2 volt 48 Ah batteries, the total capacity of 288 Ah. The
When determining the standard battery, it must be noted that the capacity of the storage oil unit should be able to safely accept the maximum current intensity Imax output by the wind turbine.
Second, the operating mode of the battery
1. Full charge system. That is, the fan is installed centrally, centralized charging, the battery is dispersed to the household, and two batteries of each household are used interchangeably.
Wind power is constrained by the wind, especially for small wind turbines. Small winds in the village, fans must be installed outside the village, difficult to build rural areas, Hote, suitable for this approach. The wind turbine can be installed on a site with better wind energy to make full use of wind energy. The use of battery rotation ensures that it is fully charged. weakness is:
1 More batteries are needed to increase investment and electricity costs.
2 Battery use efficiency is low (about 40%).
3 The charge and discharge of the battery is changed frequently and the service life is short. The
4 The battery is frequently transported back and forth to the user, and it is easy to damage the battery. Inadvertent handling and leakage of the electrolyte can cause the battery to become liquid or burn out.
2. Half-float charge operation. It is the working mode of fan (DC power generation) and battery parallel power supply. When electricity is not used (in the daytime), the wind turbine generates electricity to charge the storage battery; when there is no wind, the battery supplies power to the load; when there is wind, the fan generates electricity and charges the battery. This method is mostly used for single-unit 1 to 3 households, and the configuration of the battery has less capacity and the investment is reduced accordingly. The use of semi-float rechargeable battery life is generally more fully discharged this full charge, the use of battery efficiency is about 50%.
3. Full floating system. The battery is centrally installed in the charging room, and the battery pack and the wind generator are connected to the load circuit, so that the battery is constantly charged in a small current. When the fan is supplying power to the load, the voltage fluctuation caused by the wind speed fluctuations stabilizes the battery pack and ensures normal power supply. This operating mode battery life is longer than the above two modes, and the required battery capacity is greatly reduced, the power efficiency is improved, the battery maintenance is simplified, and the efficiency of the entire power supply equipment can reach 60-70%. The Hanbala wind power station at Chayouhouqi is working in this way.
Third, the battery type selection
There are many types of batteries. At present, wind power is commonly used in lead-acid batteries. After the battery is filled with the liquid, after 30 minutes, the liquid temperature can be used when the temperature is 15°C, and no initial charging is required. For remote places where wind turbines have just been installed and which do not have initial charging conditions, electricity can be used immediately, which is very advantageous. The disadvantage of this type of battery is its large size and weight and its inconvenient handling. The aluminum-acid batteries marketed are mostly batteries for motor vehicle start-up. Their pole plate structure and manufacturing characteristics are not suitable for use under the conditions of charging and discharging of wind power generation. Their life span is generally only about 2 to 3 years. In a large-capacity wind power station, it is best to use fixed-type acid-proof and flame-proof lead-acid batteries, which have large capacity and low electro-hydraulic specific gravity (about 1.21 at 15°C), reducing the number of poles. Corrosion of plates and separators can prolong the evaporation time, and prevent leakage measures, reducing the discharge to the ground.
Alkaline batteries are small. It is light in weight and has a service life of about 15 years. It is also used in small quantities in our district. Alkaline battery life is 5-7 times longer than acid battery, but its price is 10 times higher than that of acid battery. From an economic point of view, we think it is more advantageous to use lead-acid batteries in small wind power generation.
Fourth, the impact of battery life
1. In the charging process, as the charging time increases, the battery electromotive force E increases accordingly. To the end of charge, if the terminal voltage V is constant and the battery electromotive force E is equal to V, ie, the battery internal resistance Y pool is also reduced to a small value, the I charge should also be small. This is the correct method of charging the battery itself.
In wind power generation, there is no steady continuous charging current for a long time. It cannot be charged according to a certain charging rate. Instead, the wind voltage will dominate the charging voltage, and even at the end of charging, the current will flow. Large, not only more loss generator power, but also because of strong electro-hydraulic boiling, excessive gas, electro-hydraulic temperature is too high, the battery plate active material will be impact and accelerate off, thereby reducing the battery life.
2. Because the user lacks relevant knowledge, the correct use and maintenance of the battery is poor, and the degree of charge and discharge is not well mastered. Overcharging and overdischarging often occur, and the filling of distilled water is not timely, resulting in partial plate vulcanization. Or do not pay attention to the liquid temperature (inject new battery) when adding liquid, so that the battery liquid temperature rises very high, resulting in excessive bubbling boiling, the speed of the movement is accelerated, the kinetic energy increases, the sealing glue will be cracked, resulting in plate active material Premature shedding, these are the main reasons for life expectancy.
3. The battery manufacturing quality is poor, and its structural and electrical properties are not suitable for the requirements of wind power generation conditions, but also to reduce the service life.
Fifth, the correct use of battery maintenance
In small-scale wind power generation, the battery cost accounts for 24% to 46% of the total cost, and the annual depreciation expense accounts for more than 50% of the total cost. This is due to the high battery price and short service life. Therefore, it is a very important issue to strengthen the use and maintenance of the battery and prolong its life. Calculation and analysis show that the battery life is extended by one year and the cost per kWh can be reduced by more than 0.13 yuan.
In order to improve the efficiency of use of the battery and prolong its life, the following points must be used in use:
1. To understand the characteristics of lead-acid batteries, in strict accordance with the provisions of the product specification for use and maintenance
2. The electro-hydraulic must be prepared with chemically pure sulfuric acid and qualified distilled water. In cold places, the specific gravity should be 1.285 at 15°C. The
3. The battery level should be 10-15 mm above the plate. When using it, it is necessary to add distilled water in time if it is found that the liquid level is too low.
4. Before wiring, check whether the battery positive and negative signs are correct and whether the single-cell battery has reverse polarity.
5. Before using the battery for the first time, it is better to charge it for 3 to 4 hours before it is used for the first time. It will be more advantageous to use the battery. Non-dry-charged batteries must be used before they can be charged.
6. The electro-hydraulic temperature should be maintained at approximately 20 °C, and the electro-hydraulic temperature must not exceed 35 °C even during charging. Especially in the winter to pay attention to antifreeze. According to the data, when the temperature of electro-hydraulic is in the range of 10-35°C, the battery capacity increases or decreases by 0.8% of the rated capacity for each increase or decrease of 1°C.
7. After being filled with liquid, it is not used within 12 hours, or is left unused for a long time after use, and must be recharged after being used as required.
8. The rubber plug for the injection port is often screwed on, but the vent hole must be open so that the vapor can escape. Keep the battery dry and clean to avoid self-discharge of the battery.
9. When the electro-hydraulic specific gravity drops to 1.175, it should be immediately stopped and charged.
10. Wire clamps of the same material as the battery pole should be used. If copper clamps are used, thin layers of petrolatum or butter should be applied to prevent corrosion.
11. It is forbidden to place metal objects and tools on the battery to prevent short circuit between electrodes.
12. There must be no open fire in the charging room and electrical equipment that can generate sparks to prevent fires.