Stand-alone system configurations/es

Diagrama de cableado de tres líneas de un sistema FV autónomo de solo CC con un controlador de carga con control de iluminación de CC para iluminación y pequeñas cargas de CC.

Hay muchos diseños y configuraciones posibles diferentes para sistemas FV autónomos. El enfoque de este proyecto de diseño está en sistemas a pequeña escala, que servirán para limitar el número de diseños que se explorarán aquí. Vale la pena señalar que el número de diseños posibles aumenta enormemente a medida que aumenta el tamaño y la complejidad del sistema. Los sistemas autónomos de pequeña escala se pueden dividir en tres categorías principales según las cargas que están destinadas a alimentar: solo CC, CA y CC, y solo CA. El más apropiado de estos diseños será determinado por las necesidades energéticas y las cargas particulares del proyecto.

Los diagramas de cableado de tres líneas que se presentan a continuación y en el resto de este proceso de diseño omiten ciertos componentes ya que no están instalados con todos los sistemas y agregarlos agregaría complejidad adicional al diagrama de cableado. Se debe considerar la incorporación de los siguientes componentes en cualquier sistema autónomo:

• Dispositivo de protección contra falla a tierra (GFPD)

• Dispositivo de corriente residual (RCD) o dispositivo de protección contra fallas a tierra (GFCI)

• Shunt

• Sensor de temperatura para el controlador de carga

• Low voltage disconnect

• DC-DC converter

DC only system

Wiring diagram of a stand-alone AC/DC PV system with a charge controller with DC lighting control for lighting/DC loads and an inverter for AC loads.

An ideal system for systems that have limited load requirements like lighting, cell phone charging, a radio, an energy efficient DC TV, and an energy efficient DC fan. DC appliances do not suffer from the efficiency losses of an inverter, the standby consumption of an inverter, nor from downtime resulting from an inverter failure.

Considerations:

• Safe for users, very low likelihood of an accident occurring.

• Low cost.

• A DC system voltage of 12 V is typical for these systems in order to ensure compatibility with DC appliances, although a DC-DC converter is an option for larger 24V or 48V designs in order to ensure compatibility with 12 V appliances. DC appliances are not common in many areas of the world and may also be higher in price - this must be considered when designing a system.

• If the current requirement of the loads exceeds the lighting/load output of the charge controller, then a seperate connection to the battery with a low voltage disconnect should be made.

• The low operating voltage of 12 V DC systems can make them susceptible to voltage drop problems with long circuit runs for lighting/loads.

AC/DC system

Wiring diagram of a stand-alone AC-only PV system with a charge controller with an inverter that supplies power to both lighting and loads.

A system that incorporates an inverter to create a more flexible system that can power both DC and AC loads. Retaining DC lighting allows the user to turn off the inverter when not in use in order to avoid standby consumption losses and to still have light in the event of an inverter failure.

Considerations:

• Less safe for users than a DC only system, higher likelihood of an accident occurring due to the higher voltage of AC circuits.
• Additional cost of an inverter.

• Increases system complexity if both AC and DC circuits need to be run to the same location.

• This type of system will still suffer from voltage drop issues on longer circuit runs for lighting.

• The inverter may need to be turned on/off regularly based upon the needs of users.

AC only system

A system that incorporates an inverter to power all lighting and loads with AC. The preferred configuration as off-grid system size grows. The system will have steady inverter standby losses that can be substantial, and all AC lighting/loads will become inoperable in the event of an inverter failure.

Considerations:

• System must be adequately sized to handle the standby losses of the inverter, which can be substantial for small systems.

• Simplicity of only running AC circuits to lighting/loads.

• System is not likely to have issues with voltage drop on longer lighting/load circuits.

• Less safe for users than a DC only system, higher likelihood of an accident occurring due to the higher voltage of AC circuits.

• Recommended that a DC light is still installed for emergency use in the room/building where the system equipment is installed to provide light for troubleshooting in the event of inverter issues.