UPMSP High School Solar Repair key terms

The process by which a semiconductor material converts absorbed light energy directly into electrical current by freeing electrons and creating a voltage difference across a junction.

The instantaneous power of sunlight falling on a surface, measured in watts per square metre. It changes with time of day, season, cloud cover and panel tilt angle.

The daily solar energy available at a site expressed as the number of hours of full 1000 W/m² sunshine that would deliver the same total energy.

The reference laboratory conditions of 1000 W/m² irradiance, 25 °C cell temperature and a specified air mass spectrum, used to compare module power ratings.

The smallest current-producing unit of a photovoltaic device, usually a thin wafer of silicon with a positive and negative layer that generates about 0.5 to 0.7 volt when lit.

The maximum voltage a solar cell or module produces when no load is connected and no current flows. It rises as cell temperature falls.

The current that flows when the positive and negative terminals of a solar device are connected together with negligible resistance, measured under a defined irradiance.

The ratio of a module's maximum power to the product of its open-circuit voltage and short-circuit current. A high value indicates a good-quality cell with low internal losses.

The operating voltage and current combination at which a module delivers its greatest power under given light and temperature. It shifts continuously as conditions change.

A number describing how much a module's power or voltage changes for each degree Celsius of cell temperature change, usually expressed as a percentage per degree.

A diode connected across a group of cells inside a module so that current can route around a shaded or faulty section, limiting hot-spot heating and power loss.

A localised overheated area on a module caused by a failing cell or partial shading that forces other cells to drive current through a high resistance.

A diode placed in series with a module or string to stop reverse current from flowing back into it at night or when its voltage is lower than other parallel strings.

A series connection of several modules whose voltages add up while the same current passes through each. The string voltage must stay within controller and inverter limits.

The complete assembly of modules, usually several strings wired in parallel or series-parallel, that together forms the photovoltaic generator of a system.

The angle at which a module surface is inclined from horizontal. It is chosen so the array captures the most annual or seasonal sunlight for the site latitude.

The site study of trees, buildings, poles and other obstructions that will cast shadows on the array at different hours and seasons, used to position modules.

A photovoltaic system that operates independently of the utility grid, storing energy in batteries to supply loads at night and during cloudy periods.

A power system that combines photovoltaics with another source such as a diesel generator, wind turbine or the grid, often with battery storage and a controller.

A rechargeable battery designed to be discharged repeatedly to a large fraction of its capacity and still deliver many cycles, unlike a starting battery.

The percentage of a battery's rated capacity that has been withdrawn. Limiting it extends battery life, especially for lead-acid types.

The remaining energy in a battery expressed as a percentage of its full capacity. It is the complement of depth of discharge.

The density of battery electrolyte compared with water, measured with a hydrometer to estimate the state of charge of a flooded lead-acid cell.

A controlled deliberate overcharge of a flooded lead-acid battery that stirs the electrolyte and balances cell voltages, removing sulfation from plates.

The buildup of hard lead sulfate crystals on battery plates caused by leaving a battery discharged too long. It reduces capacity and may become permanent.

A device placed between the modules and battery that regulates charging current and voltage to prevent overcharge, over-discharge and reverse current flow.

A charge controller that rapidly switches the module connection on and off to hold battery voltage at a safe level, effectively pulling array voltage down to battery voltage.

Maximum power point tracking, a control technique in which the controller adjusts its input operating point to harvest the greatest available module power before converting it to battery voltage.

An electronic device that converts direct current from modules or batteries into alternating current suitable for household appliances or grid connection.

An inverter output whose waveform is a smooth sine curve, matching utility power and safe for motors, chargers and sensitive electronics. Contrasted with modified square wave.

The short-term power an inverter can deliver for a few seconds to start motors and compressors, above its continuous rated output.

Deliberate connection of exposed metal frames, enclosures and circuit conductors to the ground so fault current has a safe path and touch voltage stays low.

A protective switch that trips when it detects a small imbalance between live and neutral current, indicating leakage to earth that could shock a person.

A manually operated switch that disconnects the direct-current side of a photovoltaic system so modules, wiring or equipment can be worked on safely.

A locking, touch-protected plug-and-socket pair used to join module leads and string cables, designed to maintain polarity and weather sealing outdoors.

The loss of voltage along a conductor caused by its resistance, which reduces power delivered to loads and must be kept small by correct cable sizing.

A test that applies a high DC voltage between conductors and earth to confirm cable and module insulation is intact and free of moisture or damage.

Use of an infrared camera to reveal temperature differences on modules, connections and breakers, exposing hot spots, loose joints and failing bypass diodes.

A diagnostic method that sweeps the operating voltage of a string or module and plots current against voltage, revealing shading, mismatch or degradation faults.

A small stand-alone appliance combining a photovoltaic panel, a rechargeable battery, a charge controller and LED light for off-grid lighting.