If your business is looking for ways to cut down on energy costs, you’ve likely considered using renewable energy with high efficiency.
While most utility costs can only be reduced through increased efficiency, electricity costs can be reduced by making your own power via a solar energy system. In the case of commercial businesses, rooftop solar utilizes the space on top of your building for solar panels, feeding power into the grid to replace what you take.
But, how much power can you get from an installation? It depends on the effectiveness and efficiency of the commercial solar panels, the power losses from your inverter, and the climate in your area. Each factor impacts the efficiency of commercial solar installations, and ultimately the amount of power you can generate in a given space.
Table of Contents
- How Are Commercial Solar Panels Used?
- Efficiency Rating
- Using the Grid
- Cell Types: Balancing Price, Performance and Weight
- Monocrystalline Solar Panel Modules
- Polycrystalline Solar Panel Modules
- Thin Film Solar Panel Modules
- Perovskite Solar Panel Modules
- Weather’s Impact on Commercial Solar Installations
- Inverters and Output
- When You’re Serious About Solar Power, Call the Experts
How Are Commercial Solar Panels Used?
A commercial solar panel is made up of a series of solar cells, which are wired together and held in a frame. It’s photovoltaic technology (or a PV system) panel that generates electricity on a large scale from sunpower. PV cells are usually made from silicon (absorbs photons and releases electrons).
There are a variety of residential panels on the market, but commercial panels mostly use the same size and construction. A standard commercial roof panel is roughly the same size as a piece of plywood and uses 72 cells.
There are also 60-cell and 96-cell panels, depending on the needs or requirements of the commercial building. The number of cells is determined by the desired voltage and current output.
The average panel on the market has 20% conversion efficiency, which means theoretically, 20% of the sunlight (or amount of energy) that hits the panel is converted into electricity. The actual output varies widely depending on the type of cells used, as well as the wiring and the back sheet that goes behind the cells.
Electricity produced by solar panels is direct current. If you’re using battery backup power, solar electricity can charge the batteries directly. Both direct solar power and battery power must be converted to alternating current by an inverter before it can be sent to the grid or used by on site appliances.
Using the Grid
Most commercial installations only send power to the grid. This electricity is measured by a meter, and subtracted from the power the building draws from the grid, reducing the total electric bill. Since your building still gets its power from the grid, there is no change in how it operates. If the utility allows net metering, they pay for excess power. Depending on local laws and agreements, this could be as much as the full retail cost of electricity from the utility.
For more on how solar energy production can improve energy bills, check out this resource from the National Renewable Energy Laboratory (NREL).
Cell Types: Balancing Price, Performance and Weight
The main factor determining a solar system’s efficiency is the type of solar cells used in the panels. Since all commercial panels are roughly the same size, output for each panel scales with cell efficiency. Today, panels are dominated by the following cell technologies: monocrystalline solar panels, polycrystalline solar panels, thin-film solar panels and perovskite solar cells.
Monocrystalline Solar Panel Modules
A monocrystalline cell is made out of a single silicon crystal. It’s considered the most efficient solar panel type. A single silicon crystal is grown then sliced into thin wafers (which are made into solar cells), then wired together to create a solar panel. Monocrystalline silicon is expensive, but popular with both homeowners and commercial property owners.
Creating a large crystal reduces imperfections, boosting efficiency. Bifacial crystals have two sides, allowing the back to capture light reflected off of the roof or a mirrored back sheet inside the panel. Passive emitter and rear cell (PERC) panels use a second layer of solar cells to capture additional light, boosting efficiency up to 5%.
Depending on how monocrystalline cells are constructed, they have a higher efficiency of solar panels of 20-23%, or somewhere between 300 and 550 watts per panel.
Polycrystalline Solar Panel Modules
This type of solar panel uses crystal fragments instead of solid crystals. This decreases energy efficiency, but it also reduces cost and there’s less waste in the growing process. These small crystals are easy to make, and can even be constructed from recycled monocrystalline cells.
On average, polycrystalline cells are 15-17% efficient, so they have a slightly lower efficiency than the monocrystalline, with an energy output of 300-400 watts per panel. Polycrystalline is also a popular choice for commercial and residential owners.
Thin Film Solar Panel Modules
These solar panels are made by depositing a thin layer of photovoltaic material on a substrate, like plastic or glass. This makes them significantly lighter than silicon cell-based panels, allowing them to be used on light roof structures, including metal roofs.
There are three materials used to create thin film cells. Copper indium gallium selenide (CIGS) is 13-15% efficient, Cadmium telluride (CdTe) is 9-11% efficient, and amorphous silicon (a-Si) is 6-8% efficient. Most commercial solar panels use a CdTe coating. Output varies widely across these panels.
Perovskite Solar Panel Modules
These PV cells are new compared to the above-mentioned. They’re made using low-cost materials – a perovskite later between two electrodes (like titanium dioxide and carbon). Perovskite cells have shown to be higher efficient solar cells than silicon.
It’s important to note that there’s no “best” type of solar panel that has the single highest efficiency for all applications. Crystalline cells are known for durability.
Talk with a reputable commercial roofing and solar company to find out if your roof space and structure can support a solar panel, and even learn about tax credits and warranties. The best solar panels will vary from business and even geographic location.
Weather’s Impact on Commercial Solar Installations
Part of planning a solar installation is evaluating the amount of sunlight available at the site. The National Solar Radiation Database (NSRDB) provides historical data on solar radiation across the U.S. This information is used to predict the conditions your solar panel will experience and its expected performance.
Solar panels don’t just capture visible light. They also capture infrared and UV light. To estimate power output accurately, calculations have to take into account the full spectrum of solar radiation the cells can capture. This varies depending on the type of cells used.
Resistance in electric circuits increases with heat, which limits the amount of power generated on hot days. Using heat-reflective roofing materials and panels designed for high heat applications increases summer performance.
While clouds can block up to 90% of sunlight, actual losses are far less. Clouds usually limit the amount of solar radiation that reaches the earth, but they also reflect this light back to the ground. During “cloud lensing,” reflection from the clouds increases local solar radiation, resulting in higher than normal output. Cloud coverage also isn’t uniform, causing generation to fluctuate on cloudy days. NSRDB tracks these weather patterns, providing information on predicted average output on cloudy days.
There’s a standard test condition (STC), which is a set of standardized conditions manufacturers use to measure solar panel and solar cell efficiency. This allows for a consistent quality of solar cell technology.
Inverters and Output
The efficiency of commercial solar isn’t just affected by your choice of commercial solar panels. Some power is lost when the inverter turns direct current (DC) power from solar cells into alternating current (AC) power for the grid. The amount of loss varies depending on voltage, current and temperature. The efficiency curve varies from model to model, but there are a few characteristics common across inverters. They are very inefficient when they’re using a small percentage of their capacity, and may even draw more power than they convert.
Solar panel efficiency jumps up to 80% or more by the time the inverter reaches 10% capacity, and reaches nearly 100% efficiency at 20% capacity. From there, efficiency decreases slowly until the inverter reaches full capacity.
Most inverter manufacturers include efficiency information based on the CEC inverter test protocol. This allows an apples-to-apples comparison between inverters, so you can choose the model that best fits the expected average output of your panels.
When You’re Serious About Solar Power, Call the Experts
Now you know more about the efficiency of commercial solar panels!
TEMA Roofing Services isn’t just an expert commercial roofing company – we also offer solar panel installation (which includes equipment, as well as the structural supports and connections you need to support your new panels). Want to see how solar can impact your business, including utility cost reductions, tax incentives and upfront costs? Contact us, and we’ll help you plan a system that fits your building(s), your power needs AND your budget.