What is a grid connected pv system? How does it work? How is it designed? Discover all in this in-depth article
Installing a photovoltaic system is the best way to produce clean energy and save on electricity bills. A grid-connected system is the most suitable choice when seeking stable supply and the ability to feed excess electricity generated back to the national grid.
How to design a grid connected pv system?
If you’re planning a grid connected pv system, or any other photovoltaic system, and want to ensure optimal performance and precise calculation, placement, and sizing, using specific solar design software can be helpful. Let’s explore in detail the various types of photovoltaic systems, their key features, and the tools to avoid evaluation errors.
What Does Grid Connected PV System Mean?
A grid-connected photovoltaic system, or a photovoltaic system connected to the grid, is a solar energy generation system connected to the national or local electrical grid. This type of system harnesses solar energy to generate electricity through photovoltaic panels and then transmits the produced energy, entirely or partially, directly to the electrical grid, converted into alternating current.
How It Works
The grid-connected photovoltaic system comprises a photovoltaic array dedicated to harvesting solar energy, divided into several strings of photovoltaic modules arranged in parallel.
Optimally orienting the photovoltaic panels is crucial to benefit from sunlight exposure. The best exposure is between south, southeast/west, east, but specific location factors such as nearby trees or buildings casting shadows on panels, mountainous terrain, etc., need consideration.
The distinctive component of a grid connected system is the inverter, necessary to convert the energy generated by the photovoltaic array – direct current (DC) – into electrical energy for the grid in the form of alternating current (AC). It’s essential to highlight that, being “connected to the grid,” the system requires connection cables resistant to high temperatures and UV rays.
All these parts contribute to the system’s operation and the production of energy subsequently fed into the national grid.
Types of Photovoltaic Systems
There are various types of photovoltaic systems that differ in their electricity usage:
- Stand-Alone Photovoltaic Systems (stand-alone or off-grid): These systems are not connected to the distribution electrical grid, so the generated energy is entirely used to meet the needs of the individual building on or near which they are installed. Stand-alone photovoltaic systems are optimal for ensuring energy production even in remote areas not served by the distribution grid;
- Grid-Connected Photovoltaic Systems: In this context, the system is connected to the electrical grid. The generated energy is drawn from the grid distribution network, while conversely, it is supplied to the grid operator during times when the system isn’t generating energy. The electrical energy produced and fed into the grid constitutes a credit for the user;
- Hybrid Photovoltaic Systems: These systems are connected to the electrical grid, but the presence of a storage system allows the use of stored solar energy to entirely meet the user’s needs. If the stored energy is also consumed, the building will reconnect to the grid through a power control unit.
Based on the panel positioning, there are photovoltaic systems:
- On roofs;
- On facades or sunbreakers (brise soleil) of new or existing buildings;
- On the ground (photovoltaic parks with panels also of the “sunflower” type);
- On a flat terrace;
- On a photovoltaic canopy (parking).
Stand-alone and Grid-Connected Photovoltaic Systems: Differences
The main differences between a grid-connected and a stand-alone photovoltaic system concern the connection to the electrical grid, energy management, and energy independence. Here’s an overview of the disparities:
- Grid Connection
- Grid-connected: This type of system is linked to the national or local electrical grid. The generated energy can be used locally and/or fed into the grid. Additionally, when the system doesn’t produce sufficient energy, drawing electricity from the grid is possible.
- Stand-alone: In a stand-alone system, the produced energy is directly used to power local loads or stored in storage batteries for use when sunlight is unavailable (nighttime, cloudy days, etc.). There’s no connection to an external electrical grid.
- Energy Management
- Grid-connected: In a grid-connected system, excess energy can be injected into the grid, and the owner may receive credits or compensations for this energy. Accessing energy from the grid is possible when the system doesn’t produce enough.
- Stand-alone: In a stand-alone system, energy must be managed locally. Energy storage systems, such as batteries, are often present to ensure continuous supply when sunlight is unavailable.
- Energy Reliability
- Grid-connected: Grid-tied systems offer higher reliability as they can draw energy from the grid when solar production is insufficient.
- Stand-alone: Stand-alone systems entirely rely on solar production and the batteries’ capacity to store energy. Their reliability is tied to weather conditions and the size of the storage system.
- Applications and Usage
- Grid-connected: Commonly used in urban and suburban areas, grid-connected systems are suitable for those aiming to contribute to renewable energy, benefit from net metering tariffs, and have a reliable energy supply.
- Stand-alone: Stand-alone systems are ideal in remote locations without access to the electrical grid. They’re often used in applications such as weather stations, water pump systems, or off-grid houses.
In summary, the primary distinction between the two types of systems is their connection to the electrical grid, resulting in differences in energy management and reliability.
Designing a Photovoltaic System
Designing a photovoltaic system requires meticulous planning and consideration of various factors, including:
- Site Analysis
Geographical Position: Evaluate the site’s position to determine solar exposure and the available solar irradiance.
Shading: Identify any obstacles like trees or buildings that could cause shading on the photovoltaic arrays.
- System Sizing
Energetic Load Calculation: Estimate the building or device’s daily energy consumption connected to the system.
System Sizing: Determine the system’s size based on the required power and anticipated solar irradiance.
- Component Selection
Photovoltaic Panels: Choose panels with suitable efficiency and capacity.
Inverters: Select an inverter matching the photovoltaic panel’s power. Options include centralized inverters or string inverters based on the project.
Support Structures: Assess mounting options like fixed frames, solar tracking systems, or building-integrated structures for the panels.
- System Design
Array Configuration: Determine the optimal orientation and tilt to maximize solar irradiance.
Element Distribution: Plan the positioning of panels, inverters, and cables based on site characteristics.
- Financial Evaluation
Financial Analysis: Assess return on investment (ROI) and tax benefits.
Costs: Calculate initial and operational costs of the entire system.
All these aspects can be significantly simplified and managed using a guided procedure, thanks to a photovoltaic software.
In this video, we’ll be showing a practical example to guide you through the process.