tour of a solar photovoltaic (pv) system

1. Solar PV SystemsWhat Makes A Solar PV System http://buildyourownsolarpanelshelp.com 2011

2. PV Components • The module is the smallest component of the PV system. This is a connected set of solar cells which have been sealed to protect themselves from the environment. • A group of modules attached together is known as a panel. • Groups of panels are then put together to make a sub-array, which is the part of an array assembly that can be considered a unit and delivers some fraction of the total system output. • An array, is an assembly of subarray, panels or modules (or a combination of these) which includes a support structure but no non-pv components. • The array-field is a collection of all the arrays in the system.

3. Modules • The module is a collection of solar PV cells connected in series and sealed for protection against the environment. • Generally sold in any size (5-150W). • Typically the cells sit in an encapsulant (EVA) sandwiched between the front cover and the back protection. • Moisture proof backing is generally used. There is also a terminal box where the cables to connect the module are found.

4. Array Field • Modules are connected into series strings to provide the correct voltage. • Modules in a string are matched as the module with the lowest current determines the string current. • By pass diodes are also used across the modules to limit any damage due to mismatch (hotspots). • The strings are then matched in terms of total voltage and connected in parallel to provide the required system current. • A blocking diode is connected in series with each string to prevent battery discharge at night.

5. Array Field • Modules are connected into series strings to provide the correct voltage. • Modules in a string are matched as the module with the lowest current determines the string current. • By pass diodes are also used across the modules to limit any damage due to mismatch (hotspots). • The strings are then matched in terms of total voltage and connected in parallel to provide the required system current. • A blocking diode is connected in series with each string to prevent battery discharge at night.

6. Balance Of System Components • The BOS components, non-PV components, contribute significantly to the system. They are separated into electrical and mechanical components. The electrical components include the following: • Battery, cables, fuses, earthing, inverters, Maximum Power Point tracker, protection against lightning, charge regulation. • Mechanical components include the mountings which can be fixed or track the sun. Trackers must work automatically so add to the complexity of the system. Array racks can be stand alone or integrated into building structures. This requires consideration of the roof and wall materials.

7. System Configuration and Performance • System Configurations • PV Systems can be stand-alone, with storage / backup (battery) and grid connected (ie. Deliver power to the electricity grid). Storage / Backup is needed if the system is to deliver continuous power. Grid connected systems can be made to supply all power to the grid and also just to use the grid as a backup. • System Performance • Performance of a PV system measured by the performance ratio. (Ratio of actual energy obtained over a period to the ratio of theoretical energy). Good systems have PR’s of over 80% with anything under 60% needing investigation.

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