Small Solar Module Connected to a Large Battery
Components: Solar module, fuse and/or fused disconnect switch
How it works: A small current flows from the solar module through a starting battery to counteract any inherent self-discharge in the battery. A trickle charge flows only during daylight hours, but on average offsets any self-discharge.
Applications: Trickle charging of vehicle starting batteries (fleet vehicles, seasonal road equipment like snowplows) and boat batteries
Stand-Alone Systems
Solar Modules Connected Through a Charge Regulator to Battery Storage
Components: Solar modules and mounting hardware, a charge regulator, storage batteries and disconnect switches or circuit breakers
How it works: A solar array produces DC current that passes through the charge controller into storage batteries. The charge regulator reduces or stops charging current to prevent battery overcharge. Small DC loads may be connected to the charge regulator, which can then prevent battery over-discharge. The battery operates loads at night and during overcast or stormy days. Solar modules recharge the batteries when average or good weather returns.
Applications: Remote industrial areas (telecommunications, navigational aids, cathodic protection and traffic systems) and remote home systems
Above System with DC-AC Inverter Connected to Battery
Components: Above components with the addition of an inverter and an AC distribution center
How it works: Same as above with the addition of an inverter to operate AC loads. The inverter draws power from the battery and changes DC to AC current and voltage. For safety, power is sent to the distribution center which houses circuit breakers for individual AC circuits. The inverter operates from battery energy day or night.
Applications: Remote home systems
Above System with Generator
Components: Above components with the addition of a fuel generator (gasoline, diesel or propane), a rectifier and a sophisticated hybrid system controller
How it works: The system controller monitors the battery voltage. When the voltage drops to a safe but low level, the generator is turned on. AC output is converted to DC power and recharges the battery. AC output can also be used directly to power AC loads. When the battery reaches an almost full recharge level, the generator is turned off. The solar array can be sized to supply average GE needs throughout the year, and the generator is used to fill in during seasonal low output periods and prolonged bad weather.
Applications: Village power systems
Grid-Connected Systems
Solar Modules Connected to a Utility Interactive Type Inverter
and Utility Power Grid
Components: Solar modules and mounting hardware, disconnect switches or circuit breakers and a grid interactive inverter
How it works: The solar array produces DC current that passes through inverter, which converts to AC current and voltage. Power is sent to the utility meter and is either consumed immediately by home or business loads, or is sent out to the general utility grid network. The utility meter spins backwards, or two meters are used to record incoming and outgoing power. At night, loads operate from utility power since the solar power system does not produce power. The inverter shuts down automatically in case of utility power failure for safety, and reconnects automatically when utility power resumes.
Applications: Urban residential and commercial systems and utility-scale power plants
Above System with a Bi-directional Inverter and Battery Backup
Components: Above components with the addition of a battery bank, charge regulator and bi-directional inverter.
How it works: The solar array charges the battery bank through a charge regulator. DC power from the battery passes through the inverter and is converted to AC current and voltage. Power is sent to the utility meter and is either consumed immediately by home or business loads, or is sent out to the general utility grid network. The utility meter spins backwards, or two meters are used to record incoming and outgoing power. At night, loads operate and the battery bank is kept trickle charged from utility power since the solar power system does not produce power. In case of utility power failure, the direct connection to the utility meter is shut down for safety. Selected circuits in the home or business that are connected to a special secondary inverter output continue to operate, drawing energy from battery bank. The solar array recharges the battery each day until normal utility power resumes.
Applications: Urban residential and commercial systems
