Grid-Tied Solar Systems

Grid-tied solar

A grid-connected solar power system generates electricity while being connected to the utility grid. This photovoltaic system includes a solar panel, an inverter, and grid-connection equipment. Grid-connected systems can be used in a variety of settings, including residential. Commercial and large-scale grid-connected solar power systems differ from off-grid solar power systems. In most grid-connected systems, battery backup is unnecessary because when the system generates more energy than the load, it immediately transfers to the associated utility grid.

Grid-tied solar systems are by far the most prevalent and widely used by households and businesses since any extra solar power generated is exported to the electricity grid, and you are typically compensated for the energy you export through a feed-in tariff or any kind of credits.

On-grid solar systems, unlike hybrid systems, cannot work or generate electricity during a blackout for safety concerns. Because blackouts typically occur when the energy grid is destroyed, if the solar inverter continued to feed electricity into a damaged grid, it would jeopardize the safety of those working to repair the network’s faults.

During a blackout, most hybrid solar systems with battery storage can immediately disconnect from the grid (known as islanding) and continue to deliver some power.

If needed, batteries can be added to on-grid systems at a later time. A common AC battery system that can be added to an existing solar system is the Tesla Powerwall 2.

A typical on-grid system’s components are solar panels that convert solar energy into electrical energy. It is made up of photo-voltaic cells. Solar modules are made of aluminum or galvanized iron and are attached to the roof using module mounting devices. The mounting system for the modules should last for at least 25 years. The DC power from solar panels is converted to AC power by the Solar Grid Inverter.

The energy is transferred through DC cables. The array junction box connects many solar panels in a parallel configuration. Their size is determined by the capacity of the system. It also houses safety devices such as surge protectors. It’s also referred to as a ‘DC Distribution Box’. The AC distribution box is used to connect the solar inverter to the grid power source. To safeguard the system from thunder and lightning, Lightning Arrestors and an Earthing Component are used.

This is what happens after energy hits the switchboard in an on-grid system:

The meter; to be precise. Excess solar energy is channeled through the meter, which determines how much power you’re exporting or importing (purchasing).

Many states across the world have distinct metering systems. In this explanation, I’m presuming that the meter only records the amount of electricity that is exported to the grid, as is the case in much of Australia. In some states, meters record all solar energy generated by your system, thus your power will pass through your meter before reaching the switchboard, rather than after. The meter measures both production and export in some regions (now in California), and the consumer is taxed (or credited) for net electricity used over a month or year. In a subsequent blog, I’ll go through metering in further detail.

The electrical grid; the electricity that your solar system sends to the grid can then be consumed by other grid users (your neighbors). You will start importing or using electricity from the grid if your solar system is not operational or if you are using more electricity than your system produces.

In brief, it is less expensive and easier to install than an off-grid solar system, hence it is highly recommended because it reduces your electricity bill significantly.

References:

Kumar, Ajay, Nitin Gupta, and Vikas Gupta. “A comprehensive review on grid-tied solar photovoltaic system.” Journal of Green Engineering 7.1 (2017): 213-254.

Alhussainy, Abdullah Ali, and Thamar Saad Alquthami. “Power quality analysis of a large grid-tied solar photovoltaic system.” Advances in Mechanical Engineering 12.7 (2020): 1687814020944670.

Pathak, Pawan Kumar, Anil Kumar Yadav, and Pravendra Tyagi. “Design of three-phase grid-tied solar photovoltaic system based on three-phase VSI.” 2018 8th IEEE India International Conference on Power Electronics (IICPE). IEEE, 2018.