Solar Power Made Simple
The Solar Photovoltaic (PV) Power System
Photovoltaic Systems make use of the solar panels converting natural light to electricity. The ‘photovoltaic effect’; (photo = light and voltaic = electricity).
Sunlight is composed of photons, or ‘packets’ of energy. These photons have various amounts of energy corresponding to different wavelengths of light. When the photons strike a PV cell, they may be reflected or absorbed. When a photon is absorbed, the energy of the photon is transferred to an electron in an atom of the cell, a semiconductor based material (such as silicon). With its newfound energy, the electron is able to escape from its normal position associated with that atom, to become part of the current in an electrical circuit. By leaving this position, the electron leaves a hole behind. While the electron is negatively charged, the hole is recognized as a positive charge carrier and contributes to current. The PV cell has a built-in electric field, providing the voltage needed to drive the current through an external load, such as a light bulb.
Photovoltaic cells are connected to form a module (or panel) typically 60 to 72 cells per module. Crystalline silicon cells produce approximately 0.5 V each irrespective of the size of the cell. Therefore a 72-cell module will operate at close to 36 V. Modules are then connected in series and parallel to form an array to generate the required current, voltage and power. The array is then connected to an inverter which converts the DC output into AC to match the requirement of the utility.
The electricity produced by your PV system is completely independent of your electricity usage in the building as it is connected directly to the utility grid. It will rarely be the case that your electricity production exactly matches your demand. The grid essentially acts like a battery whenever you use less energy, feeding the excess electricity into the utility. On the other hand, if you need more electricity than your PV system produces, you are backed up by your local power utility provider.
Table 1: Solar Photovoltaic components and explanations.
|1. Solar Panels||Converts sunlight into electrical power via the photovoltaic effect, producing direct current (DC) to the system.Solar panels and modules are connected together into PV strings to form a solar PV array.|
|2.Mounting Hardware||Provide support and fixed position between solar panels and roof.|
|3.AC and DC Isolators||Enables separation from and within the PV system which ensures safety when carrying out installations and maintenance work.|
|4.Inverter||Enables excess power to be fed back into the grid safely. The inverter deactivates at night and automatically begins operating the next day when sunlight is sufficient. It is the heart of a Solar Power System.|
Solar Power Product
Solar E selects some of the best components in the market which make up your system.
The performance guarantee for the PV power output is given for 25 years. Over that period of time, the efficiency decreases to approximately 80% of its initial value at Standard Testing Condition. Owners are encouraged to check the performance to ensure the systems are operating at its optimal capability. This can be done by recording the energy on the inverter display board or through a wireless monitoring system.
The tilt angle is the angle of the PV panel from the horizontal ground. The tilt angle may be smaller or larger depending on the season (winter or summer). However, a minimum of 10° is recommended for standard installation to cater for self-cleaning preventing dirt from accumulating on the surface of the panel. Majority of domestic installations have their tilt angle aligned with the roof inclination. Brackets can be used to adjust the tilt angle of the panels.
The most ideal orientation for PV panels should be the true north (0°), however the angle is ultimately determined by the orientation of the roof where they are installed. Any orientation between -30° and 30° from the true north are acceptable angle for the PV panels with system performance between 95% and 100% energy yield.
Shading on any part of an array will reduce its energy output so if there is shading on a cell or module and it is connected to other cells or modules, their performance may also be reduced. In addition to that, partial shading can cause damage to PV cells. This is because the panels are connected in a series and as such, the weakest link determines the energy output. Solar PV panels have built-in bypass diodes to reduce the effect of partial shading.
Partial shading cannot be entirely eliminated, especially at times of sunrise or sunset when the shadows are longer. Marginal shading is generally accepted for time in the early morning and late evening due to the lesser energy production of the system. In the event where shading of panels cannot be eliminated, Solar E may suggest not installing a Solar PV system.
Soiling/Dirt of the Panels
Dirt deposited on the panels will form as a layer of shading on the panels. Since the dirt is deposited evenly across each panel, light still gets through but the Solar PV system will have a slightly reduced output. Natural rainfall is often sufficient to prevent the panel from accumulating large amounts of dirt; however cleaning of panels is required in very dusty and dry regions. On large applications it is available to carry out a yearly maintenance program to remove dirt and impurities that have accumulated over the course of a year.
PV cells are sensitive to temperature increases, the higher the cell temperature the lower the energy production. For example; when the solar radiation is at its strongest in summer at noon, the cells can be heated up to around 70°C or more. Heat is dissipated via the back of the panels by natural convection but it is very important to ensure clear air flow around and underneath the panels. A rise of 10°C lowers the effective power output of the PV system by 3% to 5%.
The efficiency of the PV system will reduce slowly over time, typically by 0.5% per annum. This means that the systems efficiency will be reduced to 80% of its initial value at STC.
The PV system is designed to work automatically with minimum attention. The inverter is a simple technology that is mounted (fixed) on the wall and does not require interference. However, the inverter LCD/LED display provides important and useful information such as total energy generated, daily energy generated etc. depending on the brands. Solar E uses inverters that are approved by CEC and comply with Australian and NZ standards. Different inverters have different functions on their LCD/LED indications, therefore it is recommended to refer to the Instruction/Operation Manual of inverter installed.
If the inverter is installed outside the house next to the switch board, it may also make sense to construct a canopy above the inverter to reduce heat stress and accumulation of rain water. The canopy must be at least 0.25m above the inverter. Refer to inverter manual for specifications.
The inverter displays most fault conditions and the nature of failure. However, some faults are non-critical and resolve themselves, such as unexpected fluctuations detected in the utility grid. For other fault conditions that may be critical and required attention, for example if the inverter cannot be synchronised to the grid. Therefore it is recommended to:
- Always have inverter manual ready
- Look up the error message in the manual and follow advice given
- In unable, contact Solar E and specify the error.
The PV system is characterized as “low maintenance” mainly due to the absence of moving parts. However, regular maintenance involving inspection for damage and simple cleaning (if necessary) is required. Shall the system appear not to be working after following the suggestions below or if you have any questions, please contact Solar E on the numbers given in section 2.
Solar Photovoltaic Array
The modules should be inspected for broken module glass, shading, and excessive soiling.
WARNING: Do not attempt to clean or otherwise come in contact with the surface of a PV module with broken glass face; this could result in a dangerous shock.
Dirt accumulated on PV arrays may cause reduced efficiency of up to 8%, depending on the local conditions. Flushing down with a water hose should be sufficient to remove the dust or dirt accumulated. In the event where dust or dirt cannot be cleaned by the water hose alone, a sponge and soapy water may be necessary. Shading of PV array by vegetation or other objects should be avoided.
General System Inspection
An annual inspection of fasteners, mounting hardware and incidental corrosion is suggested. This inspection can be covered with an ongoing Solar E maintenance program. In general, the wiring, the inverter, and the metering device should not need any maintenance or further inspection unless system output or power drops below expected values and cannot be brought back up by PV array cleaning. During inspection, it is important to reduce any expected shading due to vegetation overgrowth.
System Circuit Breakers
Home owners should regard the PV system’s AC circuit breaker in the similar approach as any other circuit breaker. They are safety devices that are developed for safe operations if in doubt. These breakers are located in the isolation enclosure close to the inverter or in a separate switch/meter box. When the breaker is found to be “off” (or open), simply move the breaker to the “on” (or closed) position. If faults exist, the breaker will quickly open again. In this case, the home owner should contact Solar E directly.
The performance/output of the PV system operations can be seen on the inverter LCD/LED screen and meter display (depending on meter). Power generated is indicated on these displays. The data in this handbook can be used as a guide for the generation, however the normal operating performance may be familiarised with time and experience. If solar PV system is generating exceptionally low output, and it not improved from washing the PV array, the owner should contact Solar E.
WARNING: Solar E expressly recommends that unauthorised persons DO NOT explore the wiring systems or components beyond the level of their license.
Full: 2 year Warranty on Workmanship
Inverter: 5 Year Manufacturer Replacement Warranty
Solar PV Module: 10 Year Manufacturer Replacement Warranty
10 Years Performance Guarantee 90% Output
25 Years Performance Guarantee 80% Output
*Warranties commences on completion date of fully commissioned system.
Equipment Data and Specifications
Solar Panel and inverter data sheets can be requested via Solar E on firstname.lastname@example.org
Solar E’s top priority is for the safety of its clients and employees. It is important that once your system has been installed, you comply with the following safety instructions:
The warning symbol draws your attention to an electrical safety issue and that a potential dangerous condition could exist without proper precaution. Service personnel must apply extreme caution at all times.