Category SOLAR CELLS – RESEARCH AND APPLICATION PERSPECTIVES
In the above two cases, there is always some energy loss during the power generating system operation. To obtain both wind and solar energy at the same time, a microprocessor and two batteries as shown in Fig. 5 are employed to control the charging operation from both energy sources. Figure 11 displays the circuit in detail, in which controller IC1 and comparator IC2 control the system operation. Depending on the weather condition, wind energy can charge the wind battery Ebw directly or the solar battery Ebp indirectly through Qws. Both wind and solar energy are sensed by two comparators of IC2. One senses the sunlight to control the load while the other monitors the charging condition of the wind battery...Read More
In order to acquire both wind and solar energy at the same time, the system is configured as in Fig. 4. As seen in Fig. 10(a)-(c), the wind to solar charging duty cycle ratio is changed to examine the charging behavior at three wind speeds. Owing to fluctuations in wind speed at 3 m/s, the system sometimes stops outputting the wind charging current, as seen in Fig. 10(a), while the charging of battery by solar energy remains very stable. When wind speed increases to 4 m/s, as shown in Fig. 10(b), the wind charging current continues to charge the battery during its duty cycle, but the current decreases during charging. When the solar charging duration is increased to 3.2 seconds, the wind charging current drops to 2 A, as seen in Fig. 10(c) prior to solar charging...Read More
In this study, a 250-W permanent magnet alternator driven by wind turbine and a 12- V/75-W solar cell panel were used as the wind and solar energy source, respectively. Both energy sources were output to 12-V/75-AH lead batteries, which were kept in undercharged condition before test. In the experiment, a 100- MHz scope was employed to measure the charging current and battery voltage. A current probe set at 100 mV/A was utilized to sense the charging current. The alternator outputs were converted into DC output by a rectifier module to charge the batteries. As shown in Fig. 8, there was a large variation in current and voltage because of the unstable wind speed. The fluctuations in amplitude of the charging current were attributed to the conventional AC-DC rectification effect...Read More
3.1.Source resistance measurements
To measure battery source resistance, as shown in Fig. 6(a), a 12-V/75-AH battery supplied the load through a switch. We adjusted theload resisdancrdkL to change the battery discharging current Ib. From the voltage difference Eb – Vo and Ib, the source resistance rb can be determined.
Because the solar energs is much smellier than tinea battery energy and the solsr cell internal resistance rp is much la rgecthan thebattery source resistance rb, as shown in Fig. 6(b), the output terminal of the solar panel is directly grounded to measure the solar charging current Ip. A 75- W solar cell panel was used rit tine experiment performed oufooois. From the tolar voltage £p andthe current Ip, the rolartntemel resistance oar be determined.
Owing to the large variation in the wind and solar energy, the converter is employed to provide the stable power for normal application. When only one energy source supplies the load, as shown in Fig.1(a), the voltage and frequency of the converter output is adjusted to meet the load specification. In Fig. 1(b), both wind and solar energy supply the same load simultaneously. In addition to the load requirement, the voltage and frequency of both converter outputs are adjusted such as the two energy sources can supply the load at the same time. In case of the DC-DC converter, only the output voltage of both converters should be adjusted to charge the same load.
In a small hybrid power system, a battery is usually utilized to store the renewable energy to improve the reliability...Read More
Mu-Kuen Chen and Chao-Yuan Cheng
Additional information is available at the end of the chapter http://dx. doi. org/10.5772/54495
Large wind turbines use mechanical systems, such as geared or gearless devices to increase the speed of the generator. In addition, an inverter is employed to adjust the output voltage to exceed the grid value. With its phase leading the bus phase, wind power can be integrated into the grid bus. The integration can be easily realized owing to negligible impedance of the utility bus. The main issues for wind-power generating systems include fluctuations in output voltage and quality of power supplied to the utility power system...Read More
There are many tasks, which have to be done, such that energy management can be conducted accurately. The following, we list the mandatory tasks required in energy management for solar cell system. First of all is current monitoring flow-in to and flow-out from the battery bank. The second one is measuring electrical energy content inside batteray bank by using algorithm of stored energy vs Rs. The third one is an evaluation of the internal energy condition and based on the sustanainability criteria, conducting decission process to do integration with external system (grid). The fourth one, when integration is decided, then synchronization of frequency, phase and voltage must be conducted soon...Read More
Discharging process can approximated by using a Constant Voltage Source Circuit Model as illustrated on Fig 19 below. The reason we use Constant Voltage Source circuit model, because there is a fact that at condition of near to empty, the battery (without load) still has voltage that close to peak voltage when battery at the full condition. Based on this fact, it is difficult to use capacitance model for discharging process. At Constant Voltage Source Circuit Model, VDC models Constant Voltage Source of the battery, while Resistance Rs models and represents the battery energy content. Gp represents the battery leak, which is quitely equal to G(V, T,i) function on battery charging model.
By assumption that VDC is constant, then the battery energy Ebatt can be represent...Read More