Renewable Energy Technology - Assignment Example

Assignment 11- Maintenance The RAPS System Source: Adapted from Australian Government, Department of Water Resources, Australian Greenhouse Office,http://www.greenhouse.gov.au/renewable/power/raps.html Troubleshooting the cables and conduits should be initiated from the load because of the blowing up of the fuses could be caused by a short circuit in the cables, considering the inclement weather. If there is no fault found, procedure may proceed to the RAPS System itself. By first analysis, our attention is caught on the battery charger that is old. During the past week, the owner has been frequently using the generator. The battery is not charging. Possible reasons or causes for a low specific gravity of the batteries are: 1. The batteries are not properly charged or they don’t charge; 2. There are defects in the batteries, probably because of low maintenance. When the batteries do not charged, an isolation technique should be done on the battery bank. The parallel and series connections have to be checked. It was stated that the batteries were fully charged but now the SG is low. The back-up generator should do the charging in this particular case because the PV array may not be able to give the required electricity generation. The solar array should also be checked for possible defects. An inspection on the conduit and wiring associated with the array and the two regulators should be done, finding some possible breaks or deterioration on exposed conduit and wiring. If there are leaks or open wires, conduit and wiring should immediately be replaced or repaired if possible. Suppose however, that we can’t find fault in the PV array and the wiring and conduit are all in normal and good condition. What do we do? That fuses blow up is probably because of the overload, meaning it can not give the necessary power to its load, the appliances and lighting in the house. A point from the generator and the array towards the battery charger and the regulators should be checked. There must be some leak here that prevents the battery bank from charging. As we can see in our diagram, the energy generating phase goes to the energy storage phase or equipment composed of the batteries, their housing and any protection equipment. The systems should use batteries which are designed for deep cycling applications and which are better suited to the charging and discharging regime typical of RAPS systems. There are two regulators each fed by half of the PV array. Can we point to the regulator as the possible ‘culprit’? Or, possibly it can be one of the ‘culprits’, meaning we have here one or two faults or defects. A regulator is an electronic device which controls the voltage of the solar array’s energy output to charge the battery bank appropriately. An inspection is necessary on the functioning of the regulator to ensure that indicators or meters are correctly operating for the various regulator modes. When the batteries are fully charged, the regulator should be in the float mode. The regulators are connected to the battery charging equipment so that over voltage is not delivered to the battery. But the low SG in the batteries indicates that the charging equipment does not deliver the required power to be charged to the battery bank. The batteries can not work or can not have power without the charger, so this has to be in good working condition all the time. An old battery charger can cause trouble such as brownouts if it fails to charge the batteries which in turn supply the inverter. The components in the circuit of the charging equipment also consist of heat-sinks. Overheating in the heat-sinks and components should be checked. There could be some damage in the charger. The battery charger’s performance worsened during bad weather where leaks and open wires could expose the system to short circuit and malfunctioning. Another trouble could be pinpointed at the wiring connection between the regulator and the charger, but a thorough checking revealed that there was no leak, neither was there open wire, nor that lightning could have struck on the connection. The location of the two regulators and the charger, or the entire storage equipment is a safe location, free of lightning. Conclusion: The old battery charger is not working normally. Replace. Assignment 2 Rectification and Filtering 1. Voltage and Current Waveforms For the following graphs the following features must be included ... Graph Title X and Y axes Title, Symbol and Units Waveform Period, Shape and Amplitude Voltage Waveform Current Waveform Draw and label the voltage waveforms for the half wave rectifier output ... without capacitor filtering Half-wave rectifier with capacitor filtering Draw and label the rectifier voltage waveforms for the full wave rectifier output ... Full wave rectifier without capacitor filtering Full-wave rectifier with capacitor filtering Rectification and Filtering ... 2. For both Half wave and Full wave rectification ... a. Comment on any discrepancies between the calculated and measured values that you found in Prac 2. Discrepancies between the calculated and measured values differ slightly and is illustrated in the diagram drawing above. The effect of filtering has on Eavg, a comparison of a rectifier circuit with a filter and one without filter are illustrated. The output waveforms represent the unfiltered and filtered outputs of the half-wave and full wave rectifier circuits. Current pulses flow through the load resistance R each time a diode conducts. The dashed line indicates the average value of output voltage. For the half-wave rectifier, Eavg, is less than half (or approximately 0.318) of the peak output voltage. This value is still much less than that of the applied voltage. With no capacitor connected across the output of the rectifier circuit, the waveform has a large pulsating component (ripple) compared with the average or dc component. When a capacitor is connected across the output, the average value of output voltage is increased due to the filtering action of capacitor. b. What effects are observed when the size of the filter capacitor is increased. Consider the voltage waveform, ripple content and the average DC voltage. The value of the capacitor ensures a decrease of the discharge voltage, and a substantial charge remains on the capacitor at the time of the next half cycle of operation. As a result, no current can flow through the diode until the rising ac input voltage at the anode of the diode exceeds the voltage on the charge remaining on the capacitor. The charge on the capacitor is the cathode potential of the diode. When the potential on the anode exceeds the potential on the cathode, which is the charge on the capacitor, the diode again conducts, and the capacitor begins to charge to approximately the peak value of the applied voltage. The ripple component of the output voltage is an ac voltage and the average output voltage is the dc component of the output. The filter capacitor offers a relatively low impedance to ac, and the majority of the ac flows through the filter capacitor. The ac component is therefore bypassed or shunted around the load resistance and the entire dc (or Eavg) component flows through the load resistance. c. Describe the effect of increasing the load current, on the voltage waveform, ripple content and average DC voltage. By increasing the load current, the impedance of the capacitor is reduced. When a simple capacitor filter is used in conjunction with a full-wave rectifier, improved filtering is provided because the increased ripple frequency decreases the capacitive reactance of the filter capacitor. This allows the ac component to be passed through the capacitor more easily. The output of a full-wave rectifier is much easier to filter than that of a half-wave rectifier. In a full wave rectifier, with a capacitor filter, during the discharge period, voltage across the capacitor and load resistance gradually decreases until the time of the next half cycle of rectifier operation. For good filtering, the filter capacitor should charge as fast as possible and discharge as little as possible. Works Cited Australian Government, Department of Water Resources, Australian Greenhouse Office. 6 March 2006. Remote Area Power Supply. 14 Oct. 2007. 186610_Assignments.doc 24/10/07 Read More