Your Guide to PV Modules & Solar Panel Design Basics
Solar energy is rapidly transforming the way we generate and consume electricity. According to the International Energy Agency (IEA), the global number of installed solar panels is expected to almost triple by 2030, highlighting the shift toward renewable energy. In the United States alone, over 220,000 solar installations were completed in 2024, with businesses and homeowners embracing solar power.
Source: SEIA
Despite this growth, many users still do not use solar in its full force. So, let’s explore what a solar cell module is, how to properly choose its type, and design an efficient system.
The Importance Of Proper PV System Design
A proper solar power system design maximizes energy conversion, reducing the space and materials needed for a given output. With the optimized solar PV system, you can be sure it performs well even under low-light conditions, high temperatures, partial shading, etc.
Residential PV design should be scalable, allowing you to add more panels or batteries wherever needed. Meanwhile, you need to keep an eye on the proper installation of solar cells, as it minimizes risks such as electrical faults, short circuits, overheating, voltage and current issues, etc.
What You Need To Know About The Internal Structure of PV cell
To understand the fundamentals of photovoltaics, we must first explore the specifics of solar cells. They can be made from different materials and connected in different ways, depending on the manufacturer. Generally speaking, scattered cells are connected in series to form a panel. The number of cells in a panel influences its output:
- Residential panels typically contain 60 solar cells.
- Commercial panels often feature 72 solar cells.
To ensure durability, solar panels are insulated, framed, and weatherproofed to withstand harsh environmental conditions. This not only extends the lifespan of solar cells but also protects users from potential electrical hazards.
Series and Parallel Connections in Solar Modules
The solar system performance depends on the specifications of chosen PV modules and how they are connected. There are only 3 ways to unite solar panels: in series, in parallel, or with a mixed approach.
In a series connection, the positive terminal of a PV cell connects to the negative terminal of another cell, increasing voltage while keeping the current constant. Most solar cells use this setup. However, this approach leads to mismatch losses, even when one PV cell is shaded or defective. These losses can cause hot spots and permanent damage. In severe cases, like open circuit voltage or short circuit current, those mismatches may even lead to a fire hazard.
Solar panels connected in parallel have slightly different architecture. Here, all positive terminals connect together, and all negative terminals connect together. It increases current while keeping voltage constant, making the system more resilient to shading and cell performance variations. PV modules connected this way also have mismatches, but in most cases, they are less severe.
Mismatch Effects in Solar Modules
Most solar systems use a combination of series and parallel wiring. It especially relates to the large installations. In such setups, a string refers to a set of solar cells or modules connected in series. Due to this mixed wiring design, mismatch effects can occur across the entire solar array.
To mitigate potential mismatches, installers often use bypass and blocking diodes. Let’s examine both approaches:
- Bypass diodes (connected in parallel) reduce effective resistance and prevent overheating by allowing current to bypass shaded or faulty modules.
- Blocking diodes (connected in series) prevents reverse current flow, protecting weaker strings from overloading by stronger ones.
Each string of PV modules in the array should include a blocking diode to reduce mismatch losses.
Solar System Design And Installation Rules
Designing an efficient solar system for your roof involves optimizing various aspects to maximize energy conversion while maintaining durability and cost-effectiveness. Your solar PV designer in the installer team should keep the following aspects in mind:
- Choose the PV cell material that suits your needs
- Correctly place PV modules
- Ensure proper system design
- Obtain necessary permits and conduct regular inspections
Choose the PV Cell Material That Suits Your Needs
It’s the first thing to consider while designing a solar system. The more efficient PV modules you have, the fewer panels you need to achieve the desired amount of energy. It’s especially relevant to those who have limited roof space. Currently, there are 2 types of silicon solar cell (monocrystalline and polycrystalline) and various thin-film materials.
A monocrystalline PV cell is the most efficient option, with up to 22% conversion rate. These PV modules have a jet-black color, while their average lifespan tends to be 25-30 years. They demonstrate the highest solar cell efficiency, but they are quite expensive, costing 50-60 cents per watt.
A polycrystalline PV cell is noticeable by its bluish look. If you want cheaper polycrystalline options (typically 30-50 cents per watt) in your solar power design, you may need to place more panels, as their peak efficiency is closer to 15-16%.
Choosing PV modules made from thin-film solar cells is another common approach. However, the efficiency rate of those systems rarely exceeds 14%. Another thing to keep in mind about a thin-film PV cell is that its average lifespan is usually shorter, with up to 10-15 years of reliability.
Correctly Place PV Modules
This trick allows you to catch the maximum amount of sunlight throughout the year. According to this rule, PV modules should face the Earth’s equator, and their angle should match the location’s latitude. In Chicago’s case, panels should face South and be placed at the 40°-42° angle.
Ensure Proper System Design
Calculate the right size of your system to determine how many PV modules you may need. It’s recommended to slightly exaggerate a solar power calculation. For instance, if you determine that you consume 30 kW daily, it’s better to place a system that produces 35 kW. If you are limited in space, choose a monocrystalline PV cell, as this investment will pay off.
Keep in mind that solar electricity production is weather-dependent. At the same time, the average PV cell degrades at 0.7-1% annually. With this slight overestimation, you can be sure you generate enough energy to power your house even in cloudy weather 10 years after the installation.
Source: Q Cells
We also recommend you fix your roof while you calculate solar system sizing. You need to ensure that the new roof has no leaks, as solar panels work for 20-30 years after installation. It may be unreasonably expensive to disassemble and reassemble a PV cell system just to fix the roof.
Obtain necessary permits and conduct regular inspections
Another crucial consideration is compliance with local regulations. The City of Chicago offers specific programs to facilitate the permitting process for residential and commercial solar installations:
- Solar Express Permit Program: It’s designed to streamline the permitting process for small-scale rooftop solar PV modules and systems.
- Green Permit Program: This program suits large installations, typically commercial solar PV designs, offering them incentives such as fee reductions.
For new installations, solar design, drawings, and calculations must be prepared by an Illinois-licensed architect or structural engineer. It ensures that the system design complies with local building codes and structural requirements.
Wrapping Up: Take Your Time While Choosing PV Modules And Their Design
Choosing the right solar panel system design for your situation involves understanding the materials of the PV cell, wiring configurations, and potential mismatches. Monocrystalline solar cell structure offers the highest efficiency, while polycrystalline is a more budget-friendly alternative.
Proper series and parallel connections of photovoltaic modules can ensure optimal energy output. However, you need to prevent or mitigate mismatch losses by using bypass and blocking diodes and microinverters along the way.
With advancements in solar technology, modern PV modules now offer lifespans of 25+ years, with performance guarantees ensuring up to 80-90% efficiency retention over time.
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FAQ
What is a PV module?
PV modules are the building blocks of solar panels. They are a collection of interconnected solar cells that convert sunlight into electricity.
How to size your solar system
To size your solar system, calculate your daily energy consumption in kWh. Later, divide these results by peak sun hours. If you want to go off-grid, remember that average batteries and inverters aren’t 100% efficient, so you need to make your system slightly more capacious by placing more panels or choosing a more efficient PV cell type.
What’s the difference between solar modules vs. solar panels?
The solar module is a single unit consisting of multiple interconnected solar cells enclosed in a protective frame. Meanwhile, the solar panel is a collection of one or more PV modules assembled together to form a larger unit. So, a solar panel comprises one or more PV modules, and multiple panels form a solar array for large-scale energy generation.
