Pv 7 inverter.JPG
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Part of Photovoltaics
Keywords Photovoltaics, solar power, solar energy, solar cell, solar panel, module, charge controller, battery, inverter, loads, circuit breakers, fuses, switches, solar radiation, hours of sun exposure, voltage regulator, meter, generator, wiring, sizing, wattage, photovoltaic, voltage, current, solar energy, solar power
SDG Sustainable Development Goals SDG07 Affordable and clean energy
Authors Lonny Grafman
Published 2021
License CC-BY-SA-4.0
Impact Number of views to this page. Views by admins and bots are not counted. Multiple views during the same session are counted as one. 520

The main components of a photovoltaic system are cells, panels or modules, arrays, a battery, a charge controller, a voltage regulator, a low voltage disconnect, an inverter, loads, a meter, a generator, and an overcurrent protection which includes fuses, circuit breakers, disconnects and grounding

Cell[edit | edit source]

Thin squares, discs, or films of semiconducting material which generate voltage and current when exposed to sunlight.[1]

Panel or module[edit | edit source]

Panel

Configuration of PV cells laminated between a clear superstrate (glazing) and an encapsulating substrate. [clarification needed]

A Photovoltaic panel can be directly wired to a DC Load if the load is needed only when there is sun, and the load is not sensitive to large voltage fluctuations.

Examples include:

  • A greenhouse fan - this is a load that will serve to cool down the greenhouse during the day. The more direct sunlight there is, the more the load will be working and compensating for the heat within the greenhouse.
  • A waterpump - this is a load that does not need to be operational at specific times, and hence, is only operating when there is enough sunlight to power the pump.

Array[edit | edit source]

One or more panels wired together at a specific voltage.

Deep-Cycle Battery[edit | edit source]

Battery
12 V, 40 Ah lead-acid car battery (if you have a free photo of a deep-cycle lead-acid battery, please add it!)
A deep-cycle lead-acid battery (DCLA battery) is designed to be regularly deeply discharged using most of its capacity. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver short, high current burst for cranking the engine, and to be frequently discharged of only a very small part of their capacity. While a DCLA battery can be used as a starting battery, the lower "cranking amps" imply that an over-sized battery may need to be used.

It is a type of battery (Direct Current electrical energy storage device) that can be discharged to a large fraction of capacity many times without damaging the battery.

Batteries are required for any system that needs some sort of storage capacity. If you will be using your system at times when there may not be sunlight available, a battery will store the energy from the PV array in order to power the loads at a later time.

Purpose/Importance[edit | edit source]

  • Batteries allow you to store energy directly from the energy generated by the PV Array.
  • Batteries store DC energy and allow you to utilize the energy during the night, when there is not a sufficient amount of sunlight, or when there is a blackout (if you are connected to the grid).
  • Batteries are an extremely important power supply for critical electrical loads that consistently require usage. If you are wishing to power a load only during the day, a battery may not be required, i.e. to power a fan on sunny days inside of a greenhouse. Utility grid-connected pv systems do not require the use of batteries, though they can be used as an emergency backup power supply.

Days of Autonomy[edit | edit source]

  • Autonomy refers to the number of days a battery system will provide a given load without being recharged by the pv array or another source.
  • General weather conditions determine the number of "no sun" days, which is a large variable when determining autonomy.
  • The general range of autonomy is as follows:
    • 2 to 3 days for non-essential uses or systems with a back-up power supply.
    • 5 to 7 for critical loads with no other power source.

Battery Capacity (AH)[edit | edit source]

  • Batteries are rated by amp-hour (AH) capacity. The capacity is referring to how much energy that particular battery is capable of storing. The capacity of the battery needs to be capable of supplying energy to the load. It is necessary to factor in the days of autonomy in order to determine how much storage capacity is required of your battery. The AH will tell you how many amps you can pull from the battery in one hour.
  • If more storage capacity is required for the pv system than one battery is capable of supplying, batteries can be wired in parallel to add additional storage capacity. Higher voltages are obtained through series wiring.
  • Initially, the battery capacity should be slightly larger than is required by the load because the batteries will lose capacity as they age. But if you greatly oversize the battery bank, it may remain at a state of partial charge during periods of reduced insolation - ultimately shortening the battery life. Determine the battery based on the size of your load.
  • The AH capacity will be listed on the battery.

Rate and Depth of Discharge[edit | edit source]

  • A battery is charging when energy is being put in and discharging when energy is being taken out. One cycle is considered one charge-discharge sequence, which often occurs over a period of one day.
  • The rate at which the battery is discharged directly affects it capacity. The faster the discharge, the lower the capacity. The slower the discharge, the larger the capacity.
  • The discharge rate refers to period of time at which the battery discharge was tested. For a battery rated at C/20, the discharge C (in Ah) was reached after 20 hours of discharge. For instance a 220 Ah battery, rated at 220Ah/20 would be discharged for 20 hours at 11 amps continuously.
  • Depth of Discharge (DOD) refers to how much capacity can be withdrawn from a battery. Most PV system batteries are designed for regular discharges of 40 to 80 percent. Battery life is directly related to how deep the battery is cycled; the shallower the cycle, the longer the life span.

Environmental Conditions and Battery Sizing[edit | edit source]

  • It may be unreasonable to size a battery system that would be capable of providing power during extreme weather conditions, such as three to four weeks without sun. Hence, it may be a better option to size the system according to the average number of cloudy days or to create a design with a hybrid approach adding in a generator or a wind turbine.
  • Battery capacity decreases at lower temperatures while battery life increases.
  • When sizing a battery, you can compensate for the effects of temperature by using a battery temperature multiplier. Multiply the battery capacity needed by the battery temperature multiplier.

Charge controller[edit | edit source]

Charge controller

Regulates battery voltage and controls the charging rate, or the state of charge, for batteries.

Purpose/importance

  • The charge controller functions as a voltage regulator. The main function of a controller is to prevent the battery from being overcharged by the pv array.
  • The charge controller is capable of sensing a battery´s current state of voltage. When a battery is fully charged, the controller will either stop or slow down the amount of current flowing into the battery from the pv array.
  • Charge controllers come in different sizes and must match the pv system voltage.
  • The controller must also be able to handle the maximum pv array current flowing through the controller at any given moment.

Voltage regulator[edit | edit source]

Voltage regulator

Purpose/importance

The Voltage Regulator prevents the pv panel from overcharging the battery by regulating the voltage to always be below a certain limit. The battery will specify that it cannot continue to accept current past a certain charge. The voltage regulator lowers the current as it reaches closer to this limit in order to lessen the amount of current charging the battery.

Low voltage disconnect[edit | edit source]

Low voltage disconnect (LVD)

Purpose/Importance

A Low Voltage Disconnect prevents the battery from discharging too deeply. (LVD) is a feature that can disconnect DC loads from the battery so that is does not discharge to the point of damage. If batteries are being discharged to a low level, a controller can shut off the current flowing from the battery to the DC load. The LVD must be capable of handling the maximum amperage, or load current. Lights or Buzzers on a controller can be used for critical DC loads instead of the LVD. This is important for appliances such as refrigerators that must not be cut off from a power supply without proper warning.

Inverter[edit | edit source]

Inverter

Changes direct current (DC) to alternating current (AC). To power any AC Loads, the current must be converted via an inverter.

Purpose/Importance[edit | edit source]

  • Photovoltaic modules generate only DC power. Batteries can store only DC power. An inverter is used as a "bridge" which converts DC electricity into AC electricity.
  • AC is easier to transport over long distances, this is an important component for many pv systems.
  • AC appliances have become the conventional modern electrical standard, inverters are necessary to power any type of AC load.

Watts Output[edit | edit source]

  • This indicates how many watts the inverter can supply during standard operation.
  • Choose an inverter that can handle the system´s peak AC load requirements.

Voltage Input or Battery Voltage[edit | edit source]

  • This indicates the DC input voltage that the inverter requires to run - usually 12, 24, or 48 volts.
  • The inverter input voltage must match the nominal pv system voltage.

Load[edit | edit source]

Any electrical component within a circuit that draws power from that circuit. Most loads can be turned on and off, such as a light bulb or a refrigerator. Loads are either AC or DC.

Meter[edit | edit source]

Meter

A gauge that allows you to see from where you are pulling your power, and how much power is being drawn from the loads.

Purpose/Importance

A meter acts as a gauge that informs you of where you are pulling your power from, and how much power is being drawn at any given moment.

Volt Meter[edit | edit source]

  • Battery Voltage (state of charge)
  • Panel Voltage, Current, Power and Total Energy produced over a certain period
  • Load Power and Total Energy used over a certain period

Overcurrent Protection[edit | edit source]

Fuses and circuit breakers are the two types of overcurrent protection. When a current exceeds a circuit breaker or fuse´s rated amperage, the circuit opens and stops all current flow. When a fuse has "blown," it must be replaced while a circuit breaker must be reset.

Fuses[edit | edit source]

  • Fuses consist of a wire or metal strip that will burn through when a predetermined maximum current passes through the fuse, which opens up the circuit to protect wires from damaging.

Operating too many loads at once or faulty wiring will cause a fuse failure, which protects the wires and systems from damaging by integrating overcurrent protection into the system.

Circuit Breakers[edit | edit source]

  • Circuit Breakers, unlike fuses, do not need to be replaced. When the current exceeds a circuit breaker´s rated amperage, the circuit opens and stops the current flow.

Disconnects[edit | edit source]

  • A switch gear used to connect or disconnect components of a PV system for safety or when maintanace is needed. Every component in the system must be capable of disconnecting from all sources of power. Disconnects can be switched fuses or circuit breakers.

Grounding[edit | edit source]

  • To ground a wire means to connect to the earth or to some conducting body that serves as the earth.
  • Grounding limits voltages due to lightning, line surges or unintentional contact with higher voltage lines.
  • Grounding stabilizes voltages.
  • Grounding equipment provides some protection from shock.

Generator[edit | edit source]

Generator

A Generator is an optional alternative source to a power supply for those needing extra assurance that there will be power available to their system in times of need.

  • Generators may be AC or DC.
  • The diagram above shows how an AC generator can be wired through the inverter to supply DC power to the battery and DC loads. There are only specific inverters that are capable of operating in this way.
  • DC generators can be directly wired to through the charge controller to supply the entire system.
  1. For mono-crystalline cells: if the specifications are not to be found on the panel, it is safe to assume each cell is equal to 0.45 volts. Also, the current can be assumed to be 0.22 Amps per square inch.