- Solar Panels Definition: Solar panels, also known as photovoltaic panels, convert sunlight into electrical energy using interconnected solar cells.
- Battery Role: Batteries store solar energy to ensure a consistent power supply, even when sunlight is not available.
- Controller Function: Controllers prevent battery damage by regulating the charge and discharge cycles, maintaining battery health.
- Inverter Purpose: Inverters convert DC electricity from solar panels into AC electricity, making it usable for household appliances.
- Solar Power Generation Block Diagram: The block diagram shows the flow of electricity from solar panels through controllers and inverters to power devices or feed into the grid.
Solar Panels
The generating component of a PV system is the solar panel, more precisely called a module. Products differ in cell material, power rating, dimensions, efficiency and electrical characteristics. A solar panel is a weather-protected assembly, while solar panels connected together form an array. The term photovoltaic solar panels distinguishes them from solar thermal collectors. Each module contains interconnected solar cells, usually wired mainly in series and protected by bypass diodes.
The operating potential difference of one solar cell is typically around 0.5 to 0.7 V, depending on cell type and conditions. Modern module and string voltages vary widely. A charge controller selected for a 12 V battery must accept the array’s full voltage and current range rather than rely on a fixed 14-18 V panel rule. Series connections increase voltage, while parallel strings increase available current. Designers must keep open-circuit voltage, short-circuit current and operating power within the controller, inverter, cable and protection ratings under expected temperatures.
Batteries
A grid-connected PV system does not require a battery. Its modules or strings feed a grid-interactive inverter, and the inverter supplies AC to the site’s distribution panel. Local loads use available solar power first according to the connection and controls, while the grid supplies a shortfall or receives permitted surplus.
The grid sets the reference voltage and frequency for a grid-following inverter. The inverter synchronises its output and controls injected current within interconnection limits. Solar production still varies with irradiance, temperature and shading; the utility grid balances the difference in a storage-free grid-connected system.
Stand-alone and backup systems use storage when power is needed after sunset or during low generation. A battery bank stores solar electricity, but it does not create energy or guarantee unlimited backup. The battery, inverter, controller and protected-load panel must be designed together for the required energy, continuous power, surge power and autonomy.
Deep-cycle lead-acid batteries remain in use, while lithium-ion batteries are common in newer stationary systems. Each chemistry needs compatible voltage limits, charge stages, temperature controls, ventilation or fire-safety measures where applicable, and protection against excessive charge and discharge. Series connections raise bank voltage; parallel connections raise capacity, but each configuration must follow the battery manufacturer’s limits and balancing requirements.
Charge Controller
A solar charge controller regulates energy from the array into storage. For a lead acid battery, it applies the required charging stages and limits overcharge. Many controllers or inverters also disconnect loads at a low-voltage threshold to prevent damaging over-discharge. Lithium battery systems use a battery-management system to monitor cells, temperature and safety limits. Controller type, voltage, current and maximum-power-point tracking range must match the array and battery.
Inverter
PV modules and batteries produce DC electricity, while most household loads and public grids use AC. An inverter converts DC to AC at the required voltage, frequency and waveform. It may also perform maximum-power-point tracking, monitoring, protection, battery charging and grid-support functions, depending on the product.
In an off-grid system, an inverter draws from the battery or a regulated DC bus and supplies an AC distribution panel. A grid-interactive inverter converts array DC and synchronises its AC output with the utility. A hybrid inverter can manage PV, storage, loads and the grid, but backup operation requires a designated protected circuit and equipment approved to operate while isolated from the utility.
Modern systems may use one central inverter, several string inverters, module-level power optimisers with an inverter, or one microinverter per module. A microinverter lets each module operate independently, which can reduce the effect of uneven shading, but it is one option rather than a requirement for every grid-tied system.
Components of a Stand-Alone Solar System
In a basic stand-alone system, the array sends electric power through a charge controller to the battery and any supported DC distribution. Regulated DC loads can include suitable communications equipment or LED lighting. The battery supplies stored energy when array production is below demand, while the controller enforces charging and low-voltage limits.
An inverter connected through correctly rated protection converts battery DC to AC for compatible loads. The array, battery and inverter must be sized for daily energy, peak demand, motor starting surge, expected low-sun periods and allowable depth of discharge. Critical stand-alone systems may also need a generator or another backup source; storage alone does not make the supply unlimited.
Components of a Grid-Tied Solar System
A grid-tied system may use a central inverter, string inverters or module-level microinverters. With a central or string architecture, PV strings feed the inverter’s DC input through the required switching and protection. The inverter’s AC output connects to the site’s distribution system and utility interconnection point.
When PV generation is below local demand, the grid supplies the difference. When generation exceeds demand, approved equipment may export the surplus under the site’s interconnection agreement.
A normal grid-following inverter monitors utility voltage and frequency. If the grid fails or leaves its permitted range, anti-islanding protection stops solar electricity from energising the disconnected utility circuit. Backup requires storage and an inverter designed to form a safe local island. A bidirectional energy meter can record import and export where the utility permits grid export.
In a microinverter system, each module supplies its own grid-compatible AC output. The microinverters connect in parallel on a protected AC branch circuit, so their currents and powers combine at the common system voltage.
Their output voltages are not added in series. Each unit synchronises with the same grid waveform, and the combined branch current must remain within cable, connector and overcurrent-protection ratings.
