Efficiency of Your Solar Panels – Consider Cool Roofing
- joelkohli8
- Jan 20
- 11 min read
Updated: Apr 2
Solar Panels: How Do They Work?
Increasingly common in the landscape, have you ever wondered how a solar panel works? Unsurprisingly, a solar panel converts sunlight into usable electrical energy.
Let’s break down this phenomenon step by step:
1 – Absorption of Sunlight: Solar Panels
In a solar panel, there are components called photovoltaic (PV) cells, which are most often made of silicon. What’s that? Silicon is a material with excellent semiconductor properties. This makes it ideal for use in solar panels, as it converts solar energy into electricity. Did you know? Silicon is highly abundant in the Earth’s crust, ranking second only to oxygen!
Pieces of Silicon
2 – Electrons at the Heart of the Reaction
Without delving into overly technical explanations, there exists a unit of energy measurement (quantum) called the photon:
A photon is a "packet" of energy and one of the key players in electromagnetic force. It changes or transforms when light is absorbed or emitted.
It is the energy of photons that causes electrons to move within the material. As a result, a voltage difference is created between two layers of semiconductors (for example, between two layers of silicon).
3 – The Electric Current is Here!
Since there is now a voltage difference (also known as a "potential difference"), electrons begin to flow. This flow creates a direct current (DC). That’s why solar panels are equipped with integrated circuits: to capture this current.
4 – Converting Direct Current (DC) to Alternating Current (AC)
Do you use a toaster in the morning for breakfast? Or a hair dryer after your shower? These everyday appliances run on alternating current (AC), which is different from direct current (DC). As we mentioned in step 3 of our explanation, solar panels generate direct current (DC). So, how do we switch from one to the other? With the help of an inverter, of course!
PV Inverter Circuit Topology
Direct Current (DC): The flow of electrons always moves in the same direction, from the negative terminal to the positive terminal. The speed of the electrons is estimated to be a few meters per hour.
Alternating Current (AC): The electrons move alternately in both directions of the circuit. In practical terms, this means that the electrons follow a back-and-forth movement over a distance of about one-thousandth of a millimeter. They oscillate (which is why alternating current is described as sinusoidal), and it is this oscillation that allows vibrational energy to be transmitted to the end of the conductor.
Source : alternating current and direct current - Engie
5 – Now, Use or Store the Energy
Once it has passed through the inverter, the energy, now converted into alternating current, can either be used directly for your electrical devices or stored in batteries for later use.
Now that we understand how solar panels work, let’s focus on their efficiency. Indeed, solar panels are not always efficient at any time of the day. They have periods of varying intensity.
This depends on several factors:
The intensity of the sun
The temperature
And also the quality of the photovoltaic (PV) cells used for converting sunlight.
When it comes to temperature, it is very important!
Good to know: A major challenge for solar panels is overheating. An overheated solar panel is a less efficient solar panel. If the temperatures are too high, the efficiency of the photovoltaic (PV) cells decreases, which in turn impacts the amount of electricity that is supposed to be produced. There are, in fact, two types of solar panels.
Monofacial and bifacial panels
Monofacial panels: Monofacial panels capture sunlight on only one side, which is positioned on the upper part.
Bifacial panels: Bifacial panels capture sunlight on both sides. These two sides allow for even greater efficiency when the panel is placed on a reflective surface.
Comparison between Monofacial and Bifacial Panels
Can I Install a Solar Panel on My Roof?
What Type of Roof is Suitable for Solar Panels? Solar panels are becoming increasingly common, both for businesses and homeowners. And it’s no surprise—who wouldn’t want to save on energy costs at home, especially if it’s done in an environmentally friendly way?
Regulations Regarding Solar Panels
In Switzerland, several specifics and regulations are related to the production capacity of photovoltaic panels.
If you opt for a photovoltaic installation, it will also change the aesthetics of your roof. The installation of solar panels in Switzerland is a well-regulated process, which varies slightly depending on the canton and municipality. Each canton or municipality can have specific rules regarding the installation of photovoltaic panels. These aspects affect the installation process, connection to the grid, subsidies, and use of the energy produced.
Here are the main points to consider:
1 – Types of Subsidies Based on Capacity
The production capacity of photovoltaic panels is a key criterion for determining eligibility and the type of financial support available:
Small installations (< 100 kWc) :
Eligible for the One-Time Payment (RU), which covers part of the installation cost.
No long-term contract for compensation of injected energy (sale on the local electricity market is possible).
Ideal for priority self-consumption.
Large installations (> 100 kWc) :
Eligible for the One-Time Payment (RU) for part of the initial investment, but with a specific ceiling.
There is also the possibility of receiving Compensation for Injection (RPC), which remunerates the energy injected into the grid for a defined period.
2 – Grid Connection Based on Capacity
The connection of the panels to the electrical grid also depends on the power of the installation:
Capacity < 30 kWc : Generally simple, with limited administrative procedures. Ideal for single-family homes and small businesses.
Capacity > 30 kWc : The local grid operator (GRD) may request a technical analysis to ensure that the grid can accommodate the injected power.
Very high capacity (> 1 MWc) : These installations require in-depth studies and may be subject to specific restrictions related to grid stability.
3 – Self-Consumption Obligations
To promote local consumption of renewable energy:
Installations must prioritize self-consumption, especially for small systems. In general, energy consumed on-site is financially more advantageous than energy injected into the grid.
Collective projects (such as self-consumption communities) allow energy produced in nearby buildings or neighborhoods to be shared, with specific conditions depending on the production capacity.
4 – Pricing and Buyback Rates
Small Installations (< 100 kWc): The tariffs for energy injected into the grid often decrease as installed capacity increases. Small producers receive higher tariffs to offset their smaller scale.
Large Installations (> 100 kWc): Larger systems typically need to negotiate directly with suppliers or sell their electricity on the open market.
5 – Regulatory Impact Based on Size
Large Installations (> 100 kWc): These may be subject to additional requirements:
Environmental impact assessments (if installed on large ground surfaces or in sensitive areas).
Obligations to meet specific standards for production and injection management.
6 – Managing Surplus Energy
Small Installations: It’s often advised to size the system based on self-consumption needs, as selling surplus energy is less profitable.
Large Installations: Designed to maximize production, these often include an economic model for grid injection.
7 – Technical Limitations Related to the Grid
The grid operator may limit the maximum injection capacity of an installation in certain regions where the grid is saturated.
Storage systems (batteries) or production management devices may be required to regulate the power sent to the grid.
The production capacity of photovoltaic panels determines administrative procedures, financial aid, and technical obligations in Switzerland. It’s essential to carefully evaluate the optimal capacity based on energy needs and local conditions to maximize economic and environmental benefits. For precise recommendations, it’s advised to consult a certified installer and the local grid operator.
Types of Roofs Suitable for Solar Panels
1 – Tiled Roofs
Tiled roofs are generally well-suited for solar panel installations. However, ensure the tiles are in good condition to avoid issues such as water infiltration.
2 – Slate Roofs
Slate roofs require a specialized approach, especially for attaching solar panels. While fragile, precautions can be taken to install solar panels without damaging the slates.
3 – Flat Roofs
Flat roofs are ideal for solar panels. They not only support installations but also allow you to control the panel’s tilt based on sunlight, optimizing efficiency.
4 – Metal Roofs (Steel Sheets, Corrugated Iron)
Metal roofs, such as steel sheets or corrugated iron, are also great for solar panels. Unlike slate, metal roofs are robust and can easily support the weight of solar panels.
Key Factors to Consider for Solar Panel Installation
Orientation and Inclination of Your Roof:
Ideally, a south-facing roof will capture the most sunlight. The recommended tilt is usually between 30° and 35° for optimal efficiency. Pay attention to shadows (trees, buildings, etc.) and local weather conditions (snow, hail, strong winds). Additional protections can help maintain long-term panel efficiency.
Roof Durability:
Ensure your roof is in good condition and can support the panels' weight. Consult a roofer or photovoltaic installer for an inspection and advice.
Available Space:
The number of panels needed depends on your energy requirements, so confirm you have sufficient space.
Access for Maintenance:
Over time, roofs and panels collect dirt. Regular maintenance and cleaning are necessary to ensure optimal performance. Plan for access when installing your panels.
Boosting Solar Panel Efficiency: Think Cool Roofing!
Cool Roofing refers to a range of reflective products, such as reflective paints, liquid waterproofing solutions, reflective waterproof membranes, and solar lacquers. It’s also known as cool roof, reflective paint, or heat-reducing paint.
To briefly illustrate the synergy between Cool Roofing and solar panels, after a video explanation, we’ll consider a building equipped with both technologies: cool roofing and solar panels.
But first, what is Cool Roofing?
Learn More About Cool Roofing
For more details, we invite you to read the article: "What Is Reflective Paint or Cool Roof?"
In short, here are some advantages of using cool roofing:
Improved Indoor Comfort: By reducing indoor temperatures.
Energy Savings: Lower cooling costs for air conditioning or ventilation systems.
No Winter Losses: No risk of increased energy consumption during colder months.
Boosting Solar Panel Efficiency with Cool Roofing
Suppose your cool roof has an albedo of 0.8 (80% reflectivity) and is equipped with solar panels. By combining Cool Roofing and solar panels, you can expect a 10-25% increase in energy production compared to a standard roof (according to a study by SolarWorld and the Institute for Solar Energy Research Hamelin).
What Is Albedo?
"Albedo measures a surface's ability to reflect sunlight. A high albedo means better light reflection and less heat absorption. High-albedo roofing materials, or 'cool roofs,' reduce heat absorbed by buildings, improving indoor comfort and energy efficiency."
Reflective paints are one of the solutions to turn a roof into a high-albedo surface, along with other white roofing materials (e.g., white steel sheets, white membranes).
How Does Cool Roofing Enhance Solar Panel Efficiency?
Reflective coatings like Cool Roofs help keep rooftop surfaces cooler, preventing overheating of the solar panels. Cooler panels operate more efficiently, improving energy conversion rates and ensuring a more consistent output even on hot days. This synergy enhances the overall energy production of the system.
According to a study by SolarWorld and the Institute for Solar Energy Research Hamelin, reducing your roof's temperature with cool roof paint enables your solar panels to operate more efficiently.
In fact, each degree of temperature reduction translates to a 0.5% increase in the efficiency of your solar panels. Imagine reducing the operating temperature of your panels by 10°C – that would boost their efficiency by 5%.
Roofs equipped with Cool Roofing technology increase the reflectivity (albedo) of the surface. This means the technology reflects more light directly onto your solar panels. And this is significant: the light reflected by the cool roof paint serves as additional light, potentially increasing the energy output of your solar panels by up to 25%.
Environmental and Economic Benefits of Combining Cool Roofing and Solar Panels
You save even more energy
Solar panels combined with cool roof paint not only produce solar energy but also reduce air conditioning costs. Cool roofing helps avoid the use of air conditioning. By keeping your interior cooler, you need to use it less. As a result, your energy bill will thank you. Long-term savings are guaranteed.
Did you know?
Roof surfaces such as bituminous membranes can reach temperatures of 75°C – 80°C, while steel sheet surfaces can reach 70°C. In contrast, white paint helps maintain roof surface temperatures between 30°C and 35°C.
Cooling the roof will significantly impact the building's interior temperature and also improve the performance of the panels. The efficiency of the panels decreases by 0.4% – 0.5% for every additional degree above 25°C (the temperature at which the panel operates at 100% efficiency).
The National Institute for Solar Energy (INES) found that a 1°C reduction in ambient temperature increases the efficiency of monofacial PV panels by 0.5% and bifacial panels by 1%. By reducing the ambient temperature by 30°C or 40°C, the gains become significant.
Reflective paint is perfectly complementary to the use of photovoltaic panels and helps ensure their optimal performance.
Reflective roofs can reduce the surface temperature
by 30°C to 40°C.
You reduce your energy costs
In France, studies show that buildings equipped with high albedo roofs reduce their energy consumption by around 40% and energy costs by 7% to 15%.
Air conditioners and roof replacement are both among the top 10 most expensive renovation projects, and extreme heat and ultraviolet rays degrade these systems.
Reflective surfaces reduce the transfer of heat into buildings and the overall load on air conditioners. This reduces the stress on cooling systems and extends the lifespan of your equipment.
By combining with PV panels, the savings increase thanks to the production of electricity less dependent on fossil fuels.
You boost your electricity production
The International Energy Agency (IEA) states that bifacial panels can increase their electricity production by 10% to 20% on reflective surfaces. In France, this could represent an annual increase of 150kWh to 300 kWh per square meter of panel.
To be more precise, the Sog Solar study office measures the increase in photovoltaic energy production at 8% for monofacial panels and 22% for bifacial panels when positioned on high albedo surfaces.
Reflective paints, like those from Enercool, Renovcoat, or Oxi, reflect much more sunlight and are significantly more emissive than simple white. They are particularly enriched with reflective pigments and also silica aerogels, the most efficient insulator in the world. As a result, energy production will be greatly increased.
What are silica aerogels?
You reduce your CO2 emissions
For the same reasons, more solar energy, less air conditioning = a contribution to the fight against global warming.
You are proactive
Cool roofing not only cools your roof, but it also cools your solar panels. By reducing the heat on your panels, you reduce the risk of failure. With reduced maintenance on your solar installation, you ensure the extended lifespan of your panels: less maintenance = more foresight!
What more could you ask for?
Several figures in France and abroad already confirm the marriage between solar panels and cool roofing:
Marseille: The installation of bifacial panels on high albedo roofs showed an 18% increase in electricity production.
United States: According to the EPA, cool roofs combined with bifacial PV panels increase energy efficiency of buildings by 25%.
Australia: The University of Melbourne reports a 22% increase in electricity production for bifacial panels on reflective roofs.
As we mentioned at the beginning of this article, temperature influences the performance of your solar panels. To repeat, an overheating solar panel is a less efficient one. If temperatures get too high, the efficiency of the photovoltaic cells will decrease and impact the amount of electricity that is supposed to be produced. Thanks to cool roofing, you avoid overheating!
Optimizing the energy efficiency of your building is a crucial challenge, and we know it. That’s why cool roofing and solar panels are here to help. When combined (especially with bifacial panels), these two technologies offer a powerful synergy, able to help you save money while making your life more comfortable. Plus, your panels get a boost!
In the end, it’s even the planet that thanks you for choosing this approach that is beneficial for ecological transition: you reduce the carbon footprint of your building, both regionally and globally.
By Joël Kohli, Chief Operating & Sales Strategy
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