A stand alone solar system uses solar PV modules to generate electricity from sunlight, but it is not connected to the utility grid or other electricity sources. A solar PV system can provide power for different uses like lighting, water pumping, ventilation, communication, and entertainment in remote places where there is no electricity or the electricity supply is not dependable.
Components of a Stand Alone System
Typically, a stand alone solar system is made up of four main components.
- Solar PV modules or arrays – To convert solar energy to direct current (DC) power
- Charge controller – It regulates the current and voltage supplied from PV panels to inverters, batteries, and appliances. They can be pulse width modulation (PWM) or maximum power point tracking (MPPT) controllers.
- Solar Inverter – It converts direct current to alternate current which is supplied to battery and appliances.
- Battery banks – They store excess power generated by solar panel systems during the day. This stored power can then be used at night to ensure appliances operate efficiently.
Stand Alone System Parameters
In order to create an optimal standalone solar PV system for a specific application, it is important to take into account a variety of factors.
- Load characteristics – AC coupled/DC coupled, current, frequency, power, and voltage
- Solar resource availability – The angle of panels, the intensity of solar radiation, and sunlight hours
- System configuration – Series or parallel connection of modules and batteries
- System monitoring – Indicators, meters, and sensors
- System protection – Breakers, fuses, and surge protectors
- System sizing – Battery efficiency and capacity, inverter rating, and PV module or array size.
Types of Stand Alone System
A standalone solar PV system can be configured in various ways, depending on the type and size of the load.
1. Standalone Solar PV System with Only DC Load
- Main components: A PV module and a DC load.
- Pros: Simplest and most cost-effective stand-alone system as it directly connects with DC loads like fans, motors, and pumps.
- Cons: Limited performance and applications; provides power only during daylight hours.
2. Stand Alone System with Control circuit and DC Load
- Main components (in order): Solar module, electronic control circuit (either a charge controller or MPPT), and DC loads.
- Pros: Enhanced efficiency and utilization; extended lifespan; improved performance and reliability of the load; provides stable current and voltage.
- Cons: Increased cost and complexity; does not provide power at night; needs a battery to function efficiently during the day
3. Stand Alone System with Battery, DC Load, and Electronic Control Circuit
- Main components (in order): Solar module, electronic control circuit (either a charge controller or MPPT), battery (DC coupled), and DC loads.
- Pros: Continuous and reliable power supply (day and night); handle variable loads and power demands
- Cons: More components make it costly; increased maintenance; heavy to handle; limited lifespan and efficiency
4. Stand Alone System with AC/DC Load, Electronic Control Circuit, and Inverter
- Main components (in order): Solar module, electronic control circuit (either a charge controller or MPPT), inverter, battery, and DC loads.
- Pros: Can power both AC and DC loads (computers, TV, lights, etc); more flexible and efficient
- Cons: More expensive; complex; inverter adds humming noise; requires more protection from faults and surges
Also See: What is a Solar Constant?