How Do Solar Energy Systems Work? On-Grid, Off-Grid and Hybrid Systems
Solar energy systems (solar PV) convert solar irradiation into electrical energy, enabling electricity demand to be met from a renewable source.
Applicable to a wide range of needs, from industrial plants to commercial buildings, and from homes to areas without grid access, these systems can be classified by their operating principle as grid-connected (on-grid), stand-alone (off-grid) and hybrid.
The fundamental difference between these systems lies in how the electricity generated is used, whether it is stored, and how the system operates in relation to the electricity grid.
How Do Solar Energy Systems Generate Electricity?
Solar panels convert solar irradiation into direct current (DC) electricity by means of photovoltaic cells. The electricity generated is converted by an inverter into the alternating current (AC) used in facilities, and can then be used to power electrical equipment.
Depending on the design of the system, the electricity generated can be consumed directly, stored in batteries, or exported to the electricity grid where the necessary technical and legal conditions are met.
The amount of electricity obtained from solar energy depends on factors such as solar irradiation, panel capacity, orientation and tilt angle, shading, temperature and system losses.
Types of Solar Energy System
On-Grid (Grid-Connected) Systems
On-grid systems are solar energy systems that operate connected to the electricity grid.
The electricity generated by the solar panels is used for the facility's consumption. When solar generation is insufficient, the electricity required is drawn from the grid.
During periods when generation exceeds consumption, the surplus electricity can be exported to the grid, provided that the necessary connection and permit conditions are met.
Because these systems generally do not require battery storage, they are simpler in terms of both investment and operation.
However, standard on-grid systems stop generating during a grid outage for safety reasons. On their own, therefore, they do not provide an uninterrupted electricity supply.
Off-Grid (Stand-Alone) Systems
Off-grid systems operate without a connection to the electricity grid and are designed to meet energy demand independently.
The electricity generated by the solar panels can be consumed directly. Surplus generation is usually stored in batteries so that it can be used during hours when there is no solar generation.
In determining the capacity of the system, daily energy consumption, instantaneous power demand, battery capacity and periods of low solar irradiation are considered together.
They may be preferred in particular where there is no grid access or where connection costs are high. To ensure continuity of supply, however, generation and storage capacity must be sized correctly.
Hybrid Solar Energy Systems
A hybrid solar PV system is a system architecture that can use solar generation together with battery storage and the electricity grid.
The electricity generated by the solar panels can be used for the facility's consumption, and surplus energy can be stored in batteries. When solar generation is insufficient, energy can be supplied from the batteries or from the electricity grid, depending on the system's operating scenario.
One of the important advantages of hybrid systems is that, when properly designed, they can continue to supply designated critical loads during a grid outage.
This capability is not, however, automatically present in every hybrid inverter or system. Operation during an outage requires a suitable inverter, adequate battery capacity, protection systems and the technical infrastructure to disconnect safely from the grid.
While battery storage makes it possible to use solar-generated electricity at different times, factors such as investment cost, system complexity and battery life must also be taken into account.
Which Solar Energy System Should Be Chosen?
In determining the most suitable system, the facility's electricity consumption profile, grid connection status, need for continuity of supply and investment budget should be considered together.
For facilities that have a grid connection and high daytime electricity consumption, on-grid systems may be economically advantageous. Off-grid systems come to the fore in areas without grid access, while hybrid solutions may be considered for applications that require energy storage and backup supply.
It cannot be assumed, however, that a technically feasible system is economically viable or permissible under the legislation in every case.
In Türkiye, grid-connected solar PV projects are subject to the connection, design, approval and acceptance procedures laid down in the applicable regulations, first and foremost the Regulation on Unlicensed Electricity Generation in the Electricity Market. For storage systems that interact with the grid, additional technical and regulatory requirements may apply, depending on how the system is connected and used.
For this reason, choosing the right system for a solar energy investment is not limited to determining the panel capacity to be installed. It is important to carry out a feasibility study in which electricity consumption, generation potential, system architecture, connection options and economic return are assessed together.