Solar Academy

  If your home has solar panels installed, it’s essential to know how to properly maintain them. Neglecting solar panel maintenance can lead to decreased efficiency and performance. It could even void your warranty. The good news is that solar panels require very little maintenance and mostly take care of themselves. Side Note: Hiring professionals to do regular inspections is safer if you mount your panels on the roof. Always use the proper safety gear if you intend to complete the work yourself. Now let’s check out your checklist! 1. Create a Maintenance Checklist The best way to ensure you get everything done is to write it all down. Using an established maintenance checklist will keep you organized and on track. Several of the steps included in this article make excellent additions. Keep your records for your solar panel maintenance checklist. Should something go awry later, you have proof that you completed regular checks. It also makes it easier for you to catch minor problems early before they spiral into a complete system shutdown. If you hired a professional to install your panels, ask whether the company offers a maintenance plan. Many companies do, and this can include yearly inspections and cleaning. At the very least, the company might provide you with a free checklist. 2. Record Solar Power Generation The wattage ratings on solar panels represent the best-case scenario on a clear summer day. Solar panels generally produce less energy than this. Therefore, the only way to know whether your solar panels have lapsed in performance is to measure their performance over time. Start by measuring performance once a week or once a month at midday. Continue to do so for a year. Note: The lowest performance level and conditions versus the highest level and conditions. Then record the average. You’ll now know what typical performance is in the years that follow. Ideally, you use a user-friendly interface that showcases and stores this information. It’s then easy to record specific trends and plan accordingly. 3. Review the Manufacturer’s Solar Panel Maintenance Guidelines The panel type and brand can create wide variations in how companies recommend you care for their products. Instead of only following recommendations online, review the information for your specific panels. The company should provide the following information: • Whether you can walk on the panels • How much weight walkable panels can withstand • What kind of material or chemicals to use or not to use • How often to clean the panels Be mindful that, in colder climates, solar panel maintenance includes adding insulation over the solar trackers during the winter months. Insulation prevents them from freezing in place and breaking off during wind gusts. 4. Check Electric Solar Wiring Every 6 Months When solar panels malfunction, they usually fail open. This means the panel no longer produces power or feeds electricity back int...

The conversion efficiency of a photovoltaic (PV) cell, or solar cell, is the percentage of the solar energy shining on a PV device that is converted into usable electricity. Improving this conversion efficiency is a key goal of research and helps make PV technologies cost-competitive with conventional sources of energy. FACTORS AFFECTING CONVERSION EFFICIENCY  Not all of the sunlight that reaches a PV cell is converted into electricity. In fact, most of it is lost. Multiple factors in solar cell design play roles in limiting a cell's ability to convert the sunlight it receives. Designing with these factors in mind is how higher efficiencies can be achieved. • Wavelength—Light is composed of photons—or packets of energy—that have a wide range of wavelengths and energies. The sunlight that reaches the earth's surface has wavelengths from ultraviolet, through the visible range, to infrared. When light strikes the surface of a solar cell, some photons are reflected, while others pass right through. Some of the absorbed photons have their energy turned into heat. The remainder have the right amount of energy to separate electrons from their atomic bonds to produce charge carriers and electric current. • Recombination—One way for electric current to flow in a semiconductor is for a "charge carrier," such as a negatively-charged electron, to flow across the material. Another such charge carrier is known as a "hole," which represents the absence of an electron within the material and acts like a positive charge carrier. When an electron encounters a hole, they may recombine and therefore cancel out their contributions to the electrical current. Direct recombination, in which light-generated electrons and holes encounter each other, recombine, and emit a photon, reverses the process from which electricity is generated in a solar cell. It is one of the fundamental factors that limits efficiency. Indirect recombination is a process in which the electrons or holes encounter an impurity, a defect in the crystal structure, or interface that makes it easier for them to recombine and release their energy as heat. • Temperature—Solar cells generally work best at low temperatures. Higher temperatures cause the semiconductor properties to shift, resulting in a slight increase in current, but a much larger decrease in voltage. Extreme increases in temperature can also damage the cell and other module materials, leading to shorter operating lifetimes. Since much of the sunlight shining on cells becomes heat, proper thermal management improves both efficiency and lifetime. • Reflection—A cell's efficiency can be increased by minimizing the amount of light reflected away from the cell's surface. For example, untreated silicon reflects more than 30% of incident light. Anti-reflection coatings and textured surfaces help decrease reflection. A high-efficiency cell will appear dark blue or black. DETERMINING CONV...

  (If you’re thinking about going solar at your home or business, you want the biggest bang for your buck.) Luckily, solar is cheaper than ever, thanks to the falling cost and rising efficiency of photovoltaic (PV) solar panels. But here’s something to consider: figuring out the real cost of solar energy is about more than just the price tag on the panels and their rated power output. For example, there’s the lifespan of the panels to take into account. And then there’s the system’s “solar energy yield” -- or how much electricity it will actually generate over the course of the year. Solar panels are rated on efficiency and the power output under standard laboratory conditions. Of course, your solar energy system isn’t being installed in a lab. It’s going outside, where all kinds of things can change its actual solar energy yield. That’s why the Energy Department’s Solar Energy Technologies Office (SETO) is funding research into better, tougher modules that can last longer and generate more electricity in less-than-ideal conditions. Read on to learn about three ways the outside world can conspire to cut into your solar energy yield -- and how SETO-funded projects are working on solutions. MAN, IT’S A HOT ONE High temperatures reduce the voltage of a solar cell -- which, as you might guess, is a bad thing. Conventional rooftop solar modules can lose as much as 30 percent of their electricity output on hot summer days. Researchers at Arizona State University are trying to address this problem by improving the backsheet -- or bottom layer -- of a solar PV module, which serves as an electrical insulator and protects the module from moisture and other environmental damage. By studying backsheets with different heat-conducting properties, the team hopes to keep solar panels cooler and improve performance in hot weather. DIRT DOES HURT Another way panels lose power is simply that they get dirty. The effects of “soiling” (as it’s known in the solar industry) vary widely by location, but energy yield losses of 10 percent are not uncommon. Research on environmental conditions and panel maintenance procedures could help us better understand how and why panels lose power to dirt, which in turn could lead to better prediction of soiling from one solar energy system to another and more effective dirt-resistant treatments for PV module glass. SHADY SITUATIONS While heat and dirt reduce solar panels’ energy yield in a pretty straightforward way, shadows are a bit more complicated. In instances when a faint cloud goes over the solar module, the power levels are simply reduced. However, sometimes the light is completely or regularly blocked by a permanent structure -- like a utility pole that shades just one part of the module -- which can actually cause “hot spots” that can damage the module over time.

Solar manufacturing encompasses the production of products and materials across the solar value chain.  While some concentrating solar-thermal manufacturing exists, most solar manufacturing in the United States is related to photovoltaic (PV) systems. Those systems are comprised of PV modules, racking and wiring, power electronics, and system monitoring devices, all of which are manufactured. PV Module Manufacturing SILICON PV Most commercially available PV modules rely on crystalline silicon as the absorber material. These modules have several manufacturing steps that typically occur separately from each other. • Polysilicon Production – Poly silicon is a high-purity, fine-grained crystalline silicon product, typically in the shape of rods or beads depending on the method of production. Polysilicon is commonly manufactured using methods that rely on highly reactive gases, synthesized primarily using metallurgical-grade silicon (obtained from quartz sand), hydrogen, and chlorine. In one process, called the Siemens process, the silicon-hydrogen-chlorine compound gas passes over a heated silicon filament, breaking the molecular bonds and depositing the silicon atom on the filament, which ultimately grows into a large U-shaped polysilicon rod. The hydrogen and chlorine atoms are reused in a closed cycle. To keep the filament from contaminating the high-purity poly, the filament itself is also made of pure silicon. In another method, small silicon beads sit at the bottom of an inverted cone-shaped vessel where a compound gas of silicon and hydrogen is pumped in, causing the small beads to float near the surface. Heating the vessel causes the silicon-hydrogen bonds to break, which results in the silicon atoms depositing onto the small beads until they are too heavy to float and drop to the bottom of the vessel where they are harvested, ready for use. • Ingot and Wafer Production – To turn polysilicon into wafers, polysilicon is placed into a container that is heated until the polysilicon forms a liquid mass. In one process, called the Czochralski process, a large cylindrical ingot of monocrystalline silicon is grown by touching a small crystalline seed to the surface of the liquid and slowly pulling it upward. In another process, call directional solidification, the liquid mass is slowly cooled until it solidifies from the bottom up, forming a large-grained multicrystalline-silicon ingot. Silicon ingots are then sliced into very thin wafers using diamond-coated wire saws. The silicon sawdust that is created is called kerf. Though less common, kerfless wafer production can be accomplished by pulling cooled layers off a molten bath of silicon, or by using gaseous silicon compounds to deposit a thin layer of silicon atoms onto a crystalline template in the shape of a wafer. • Cell Fabrication – Silicon wafers are then fabricated into photovoltaic cells. The first step is chemical texturing of the wafer surface, which...

Solar photovoltaic modules are where the electricity gets generated, but are only one of the many parts in a complete photovoltaic (PV) system. In order for the generated electricity to be useful in a home or business, a number of other technologies must be in place. MOUNTING STRUCTURES  PV arrays must be mounted on a stable, durable structure that can support the array and withstand wind, rain, hail, and corrosion over decades. These structures tilt the PV array at a fixed angle determined by the local latitude, orientation of the structure, and electrical load requirements. To obtain the highest annual energy output, modules in the northern hemisphere are pointed due south and inclined at an angle equal to the local latitude. Rack mounting is currently the most common method because it is robust, versatile, and easy to construct and install. More sophisticated and less expensive methods continue to be developed. For PV arrays mounted on the ground, tracking mechanisms automatically move panels to follow the sun across the sky, which provides more energy and higher returns on investment. One-axis trackers are typically designed to track the sun from east to west. Two-axis trackers allow for modules to remain pointed directly at the sun throughout the day. Naturally, tracking involves more up-front costs and sophisticated systems are more expensive and require more maintenance. As systems have improved, the cost-benefit analysis increasingly favors tracking for ground-mounted systems.  BUILDING-INTEGRATED PV While most solar modules are placed in dedicated mounting structures, they can also be integrated directly into building materials like roofing, windows, or façades. These systems are known as building-integrated PV (BIPV). Integrating solar into buildings could improve material and supply chain efficiencies by combining redundant parts, and reduce system cost by using existing building systems and support structures. BIPV systems could provide power for direct current (DC) applications in buildings, like LED lighting, computers, sensors, and motors, and support grid-integrated efficient building applications, like electric vehicle charging. BIPV systems still face technical and commercial barriers to widespread use, but their unique value makes them a promising alternative to traditional mounting structures and building materials. INVERTERS  Inverters are used to convert the direct current (DC) electricity generated by solar photovoltaic modules into alternating current (AC) electricity, which is used for local transmission of electricity, as well as most appliances in our homes. PV systems either have one inverter that converts the electricity generated by all of the modules, or microinverters that are attached to each individual module. A single inverter is generally less expensive and can be more easily cooled and serviced when needed. The microinverter allows for independent operation of each panel, which is useful ...

When light shines on a photovoltaic (PV) cell – also called a solar cell – that light may be reflected, absorbed, or pass right through the cell. The PV cell is composed of semiconductor material; the “semi” means that it can conduct electricity better than an insulator but not as well as a good conductor like a metal. There are several different semiconductor materials used in PV cells. When the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material called electrons. This extra energy allows the electrons to flow through the material as an electrical current. This current is extracted through conductive metal contacts – the grid-like lines on a solar cells – and can then be used to power your home and the rest of the electric grid. The efficiency of a PV cell is simply the amount of electrical power coming out of the cell compared to the energy from the light shining on it, which indicates how effective the cell is at converting energy from one form to the other. The amount of electricity produced from PV cells depends on the characteristics (such as intensity and wavelengths) of the light available and multiple performance attributes of the cell. An important property of PV semiconductors is the bandgap, which indicates what wavelengths of light the material can absorb and convert to electrical energy. If the semiconductor’s bandgap matches the wavelengths of light shining on the PV cell, then that cell can efficiently make use of all the available energy. Learn more below about the most commonly-used semiconductor materials for PV cells. A picture of three solar cells made out of different silicon materials: thin-film, monocrystalline, and polycrystalline silicon. SILICON  Silicon is, by far, the most common semiconductor material used in solar cells, representing approximately 95% of the modules sold today. It is also the second most abundant material on Earth (after oxygen) and the most common semiconductor used in computer chips. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This lattice provides an organized structure that makes conversion of light into electricity more efficient. Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules are expected to last for 25 years or more, still producing more than 80% of their original power after this time. THIN-FILM PHOTOVOLTAICS  A thin-film solar cell is made by depositing one or more thin layers of PV material on a supporting material such as glass, plastic, or metal. There are two main types of thin-film PV semiconductors on the market today: cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). Both materials can be deposited directly onto either the front or back of the module surface. CdTe is the second-most common PV materi...

What is photovoltaic (PV) technology and how does it work? PV materials and devices convert sunlight into electrical energy. A single PV device is known as a cell. An individual PV cell is usually small, typically producing about 4 or 5 watts of power. These cells are made of different semiconductor materials and are often less than the thickness of four human hairs. In order to withstand the outdoors for many years, cells are sandwiched between protective materials in a combination of glass and/or plastics. To boost the power output of PV cells, they are connected together in chains to form larger units known as modules or panels. Modules can be used individually, or several can be connected to form arrays. One or more arrays is then connected to the electrical grid as part of a complete PV system. Because of this modular structure, PV systems can be built to meet almost any electric power need, small or large. PV modules and arrays are just one part of a PV system. Systems also include mounting structures that point panels toward the sun, along with the components that take the direct-current (DC) electricity produced by modules and convert it to the alternating-current (AC) electricity used to power all of the appliances in your home.