Guide to Solar Panels
September 10, 2021
WHAT ARE SOLAR PANELS?
A solar panel is a collection of solar photovoltaic (PV) cells that absorb sunlight and convert that light into electricity. For most installations, multiple solar panels are connected to create a solar array. The components of a solar panel include the solar cells, glass casing, backsheet, metal frame, and cabling to transmit electricity.
A BRIEF HISTORY OF SOLAR ELECTRIC POWER TECHNOLOGY
Thomas Edison developed direct current (DC) electricity, a circuit in which electrons flow in a single direction. DC electricity worked similar to a battery powering a lightbulb, which was the standard in the United States until the 1880s. Nikola Tesla believed that alternating current (AC) electricity was a better solution because it could easily be converted to different voltages, making it easier to transport over long distances.
The tide began to turn when Tesla’s technology was chosen for the Chicago World’s Fair in 1893, and AC electricity became the standard for the electric power grid in the United States. Tesla, Inc. is now the name of a company created by Elon Musk that utilizes AC electricity for their energy-efficient vehicles and solar technologies.
The sun’s energy is critical to all life on earth, and humans have always found ways to harness its energy. Solar PV technology, as we know it today, has been around since Bell Labs created the first silicon cell in 1954. By 1960, solar cell efficiency had improved from 4% to 14%.
The solar energy industry continued to expand throughout the following decades. Solar technology improved due to investments in research and development and regulatory frameworks for solar interconnections established by federal and state governments. These both included policies such as tax credits, rebates, and renewable energy standards.
[Related: Guide to Federal Solar Panel Incentives]
By 1999, cumulative installed solar capacity had reached 1,000 megawatts (MW). In 2000, while astronauts were installing solar panels on the International Space Station, Sandia Laboratories invented the modern inverter that improved system safety during power outages.
In the almost two decades since then, solar panel costs have fallen dramatically due to innovations in solar panel design and racking system improvements that make installations easier and faster to complete.
According to a data report from Statista, within the nearly two decades spanning from 2000 to 2019, worldwide net solar PV power generation increased from 1,288 MW to 633,700 MW.
The future of solar technology innovation will continue to advance, making it easier for average people to acquire highly efficient panels, and new systems will likely focus on materials beyond or in addition to silicon. For example, recent breakthroughs with perovskites may lead to higher-efficiency panels and the ability to coat various surfaces with solar as easily as painting.
Given that the amount of sunlight reaching Earth every hour is enough to power the entire globe’s electricity use for a year, the potential for solar power is unlimited.
TYPES OF SOLAR PANELS
Solar panel manufacturers use varying types of solar cells and solar technologies, but the most common material used for solar cells is Silicon (Si). Silicon is a key component of different types of solar panels, all with their own advantages and disadvantages. But depending on how you’re using solar energy, knowing the benefits of any emerging solar cell technologies using additional techniques or materials is important.
Solar cells are made from silicon and are built with a positive and negative layer to create an electric field, similar to a battery. Most solar panels are made from either monocrystalline or polycrystalline silicon.
- Average efficiency range: 15%-24%
- How it’s made: Wafers are cut from a single crystal block of highly pure silicon with cells that form a distinctive shape.
- Appearance: Monocrystalline cells have a uniform appearance of small black squares with notched corners. Solar panels made with these solar cells typically have either a white or black backsheet.
- Features: These panels conduct electricity more efficiently and perform better in high temperatures and shaded conditions, enabling them to generate more solar power than other panels of the same size. Since this type of technology is the most established, it also has a proven track record of durability. However, they’re the most expensive panels and generate more waste in the manufacturing process.
POLYCRYSTALLINE (OR MULTICRYSTALLINE) SILICON
- Average efficiency range: 12%-16%
- How it’s made: Fragments from multiple silicon crystals are heated, melted, and pressed together to form a large solar cell.
- Appearance: These solar cells have a multifaceted, nonuniform, gem-like surface and are typically blue in color.
- Features: Polycrystalline solar panels are less efficient, but less expensive, and also less wasteful in the silicon manufacturing process. These are the most prevalent solar panels globally, primarily due to a production boom in China over the last few years. Additionally, these solar cells are covered by a glass casing, typically made from anti-reflective glass to increase sunlight absorption and improve solar panel efficiency, while also protected by a backsheet.
THIN FILM SOLAR PANELS
- Average efficiency range: 7%-13%
- How it’s made: A thin layer of photovoltaic material or combination of materials such as noncrystalline amorphous silicon (a-Si), Cadmium Telluride (CdTe), or copper indium gallium selenide (CIGS) is deposited onto a surface such as glass, plastic, or metal.
- Appearance: Thin film silicon panels are generally larger and have a uniform, solid black appearance.
- Features: This is a newer technology that’s commercially available and is suitable for homes or businesses where space is not an issue. Thin film solar panels are low-cost, easy to produce, flexible, portable, and lightweight. However, they’re less durable and have a shorter lifespan.
SILICON SOLAR PANELS SUMMARY
|Silicon Cell Type||Efficiency||Key Advantages||Key Disadvantages|
|Monocrystalline||15%-24%||Most efficient, durable, proven, aesthetically pleasing||Highest cost|
|Polycrystalline||12%-16%||Lower cost, improving efficiencies||Lower efficiency, poorer aesthetics|
|Thin Film||7%-13%||Low cost, easy to make, best aesthetics||Low efficiency, less proven|
OTHER SOLAR CELL TECHNOLOGIES
Multi-junction solar cells are based on the same principles as silicon-based cells, except they’re designed with multiple layers of different semiconductors that can capture more of the light spectrum.
HETEROJUNCTION WITH INTRINSIC THIN-LAYER (HIT)
HIT solar cells, invented by Panasonic, use thin intrinsic amorphous silicon layers on both the top and bottom surfaces of a crystalline silicon wafer.
Solar cells made from Perovskite are a family of crystals named after the Russian geologist, Lev Perovski. Perovskites are less stable than silicon but can achieve similar solar energy efficiency as monocrystalline cells at a lower cost.
Although not yet commercially available, this promising technology could soon be applied as a film over existing silicon-based cells to boost the efficiency of standard solar panels. Oxford PV is piloting production of this technology in Germany.
[Related: The Race to the Most Efficient Solar Panels]
HOW SOLAR PANELS WORK
Solar panel system functions are simpler than people think.
The sun releases tiny packets of energy called photons that travel to Earth, and this sunlight shines onto panels in varying amounts depending on their orientation and the location of your home or business. Solar panels then convert the sun’s energy (photons) into electricity when they hit a solar cell by knocking electrons loose from their atoms. These electrons then flow through a conduit to an inverter.
Inverters convert that electrical energy from DC to AC — AC electricity is what we use for our lights, appliances, and devices (anything that gets plugged into a wall outlet). AC electricity then flows to your electricity meter to power your home or to your city’s grid.
When the sun isn’t shining and your panels don’t have any solar energy to convert to electricity, your home will continue to be powered from the electric grid. If your solar panel system generates more electricity than you’re using at any given moment, that electricity will flow out of your home back into the grid. Many utility companies have net metering policies that credit you for the excess solar power you generate.
[Related: How Do Solar Panels Work?]
TYPES OF INVERTERS
Another key part of a solar electric power system is the inverter technology. There are three main types of inverters:
- String inverter: The DC electricity from your solar system is routed through a single inverter, which is then connected to your electrical panel. String inverters are the least expensive inverter solution, but they make it difficult to assess performance issues with individual panels.
- Microinverter: Micro-inverters attach on the backs of each individual panel. These tend to be more expensive but enable panel-level monitoring.
- Hybrid: This offers a middle-ground solution that combines a centralized inverter with power optimizers on each panel. Power optimizers are a DC-to-DC converter technology that improves performance by tuning each panel’s output to match the inverter. This technology offers some of the same system performance benefits as microinverters but at a lower cost.
Inverters provide additional features beyond converting electric currents for our use, such as ground fault protection and providing insights into energy production and maximum power point tracking.
[Related: Who Makes the Best Solar Panels]
WHAT DIRECTION SHOULD SOLAR PANELS FACE?
Ideally, solar panels mounted on a standard pitch roof should face south, allowing for maximum production. Should your panels face southeast or southwest, you can expect them to generate roughly 10% less power, but that may still be enough to power your home.
If you can’t install your solar panels facing south, consider:
- Installing panels facing a different direction: Panels facing west or southwest may still be able to produce enough energy to fully or partially power your home. Your installation professional can make this determination.
- Installing more panels: While solar panels that don’t face south won’t receive as much direct sunlight, you may be able to compensate by using more panels.
- Installing your panels on the ground or wall: It’s a common misconception that you can only install solar panels on your roof. If you don’t like the appearance or if your roof doesn’t face south, you can install your system on a south-facing wall that receives direct sunlight. A ground-mounted system is also possible as long as you have the space for it, and is sometimes preferred since it’s cheaper to install and maintain than a wall-mounted system.
Take a look at Freedom Solar’s easy to use solar potential calculator to determine an estimate for the solar potential of your home. An installation professional can also use technology to track how the sun hits your home, allowing them to install your panels facing the right direction at the right tilt.
WHEN SHOULD YOU GO SOLAR?
Going solar at any time is a smart life decision, but acquiring and installing your solar panel system right before summer will reap the most benefits. You can potentially keep your home up to 5° F cooler by shading your roof, which is especially helpful over the warm summer season — that’s a 38% reduction of your home’s annual cooling load.
Transitioning to solar power not only saves you money on your electricity bill, but can also potentially help you keep your lights on when the summer heat climbs and electricity outages are more likely to occur.
Since electricity rates can be volatile for consumers over the summer, it’s smart to go solar before the hot season starts, but to be clear, any time is a good time.
FIND A TRUSTWORTHY SOLAR INSTALLER TO HELP YOU GO SOLAR
Don’t let anything stand between you and installing the system of your dreams. An experienced, trustworthy solar panel installer can help you harness the power of the sun no matter where you live or which direction your roof faces.