What is a solar panel?
Solar photovoltaic (PV) panel is a solar technology that absorbs sunlight as a source of energy in order to generate direct current electricity. A photovoltaic module is a packaged, connected assembly of photovoltaic solar cells that are available in different voltages and wattages. PV modules are a part of the PV array of a PV system that generates and supplies solar electricity in commercial and residential applications.
History of Solar Panels
The history of solar panels can be traced all the way to 1839 when Alexandre-Edmond Becquerel was able to observe the ability of some materials to create an electrical charge from light exposure for the first time. At the time, the first solar panels were too inefficient for even simple electric devices, but they were still used as an instrument to measure light.
This observation by Becquerel was not replicated again until 1873 when Willoughby Smith discovered that the charge could be caused by light hitting selenium. After this discovery, William Grylls Adams and Richard Evans Day published “The Action of Light on Selenium” in 1876. This is where they described the experiment they used to replicate Smith’s results.
In 1881, Charles Fritts created the first commercial solar panel, which was reported by Fritts as “continuous, constant, and of considerable force not only by exposure to sunlight but also to dim, diffused daylight.” However, these solar panels were still very inefficient, especially when compared to coal-fired power plants.
It was only in 1939 when Russell Ohl was able to create the solar cell design that is used in many modern solar panels. He patented this design in 1941, and in 1954, this design was first used by Bell Labs to create the first commercially viable silicon solar cell.
In the late 1950s and early 1960s, satellites in the space program of both the United States and the Soviet Union were powered by solar cells. And in the late 1960s, solar power was practically the standard for powering space bound satellites.
In the early 1970s, a way to lower the cost of solar cells was discovered. This enabled the price to be brought down from $100 per watt to around $20 per watt. This research was spearheaded by Exxon, and around this time, most off-shore oil rigs used the solar cells to power the warning lights on the top of the rigs.
During the period from the 1970s to the 1990s, there was quite a change in the usage of solar cells. They began being used on railroad crossings and in remote places to power homes. Australia used solar cells in their microwave towers to expand their telecommunication capabilities. Even desert regions were able to see solar power bring water to the soil where line-fed power was not an option.
Today, we see solar panels just about everywhere. And a piece of even better news is the fact that not only are solar panels in the present day more efficient than the ones in the past, but they are also incredibly cheap now. In fact, it has been reported that in just over the last four decades, the cost of solar energy products, most particularly the PV modules, has dropped by 99%.
Because of this price drop of solar panels, there has been a resurgence of solar-inspired products. There are now solar-powered cars as well as solar-powered aircraft. Aside from that, solar shingles that can be installed on our roofs instead of the usual roofing materials exist as well. Best of all, international markets have opened up, and solar panel manufacturers are now playing a key role in the solar power industry.
Theory and Construction of Solar Panels
How They Work
Photovoltaic modules make use of light energy from the sun to generate electricity through the photovoltaic effect. The photovoltaic effect is a physical and chemical phenomenon where the creation of voltage and electric current happens when a material is exposed to light. Essentially, a solar panel works by allowing photons, or particles of light, to knock electrons free from atoms, thus generating a flow of electricity.
Solar panels are actually comprised of many, smaller units called photovoltaic cells. Each photovoltaic cell is basically a sandwich that is made up of two slices of semiconducting material, usually silicon. In order for it to work, photovoltaic cells have to establish an electric field. The same as a magnetic field, which happens because of opposite poles, an electric field happens when opposite charges are separated.
To get this field, manufacturers “dope” silicon with other materials, giving each slice of the sandwich a positive or negative electrical charge. To be more specific, they seed phosphorous into the top layer of silicon, which adds extra electrons with a negative charge to that layer. At the same time, the bottom layer gets a dose of boron, which results in fewer electrons or a positive charge. All this adds up to an electric field at the junction between the silicon layers. And then, when a photon of sunlight knocks an electron free, the electric field will push that electron out of the silicon junction.
The majority of modules use wafer-based crystalline silicon cells or thin-film cells. The structural, or load-carrying, member of a module can either be the top layer or the back layer. Additionally, cells must also be protected from mechanical damage and moisture. Most of the time, modules are rigid, but semi-flexible ones based on thin-film cells are also available. The cells are connected electrically in series, one to another to the desired voltage, and then in parallel to increase amperage. The voltage and amperage of the module are then multiplied to create the wattage of the module.
A PV junction box is attached to the back of the solar panel, and it is its output interface. On the outside, most of PV modules use MC4 connectors type to facilitate easy weatherproof connections to the rest of the system. Oftentimes, a USB power interface can also be used.
Module electrical connections are made in series to achieve the desired output voltage or in parallel to provide a desired current capability (amperes) of the solar panel or the PV system. The conducting wires that the current of the modules are sized based on the ampacity and may contain silver, copper, or other non-magnetic conductive transition metals. Additionally, bypass diodes may also be incorporated or used externally, in case of partial module shading, to maximize the output of module sections that are still illuminated.
Some special solar PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells. This allows the use of cells with a high cost per unit area, such as gallium arsenide, in a cost-effective way.
Furthermore, solar panels also use metal frames that consist of racking components, brackets, reflector shapes, and troughs to better support the panel structure.
Efficiencies of Solar Panels
Each module is rated by its DC output power under standard test conditions (STC), and usually ranges from 100 to 365 W. The efficiency of a module determines the area of a module that is given the same rated output. For example, an 8% efficient 230 W module will have twice the area of a 16% efficient 230 W module. There are only a few commercially available solar modules that exceed the efficiency of 24%.
Sometimes, PV modules can produce electricity from a range of frequencies of light, depending on the construction. But even still, they usually cannot cover the entire solar range, specifically ultraviolent, infrared, and low or diffused light. That is why much of the incident sunlight energy is wasted by solar modules, and they can give far higher efficiencies if they are illuminated with monochromatic light. Because of this, another design concept is to split the light into six to eight different wavelength ranges that will produce a different color of light and direct the beams onto different cells that are tuned to those ranges. This design concept has been predicted to be capable of raising efficiency by 50%.
A single solar module can produce only a limited amount of power. That is why most installations contain multiple modules that add voltages or current to the wiring and PV system. A PV system usually includes an array of PV modules, an inverter, a battery pack for energy storage, charge controller, interconnection wiring, circuit breakers, fuses, disconnect switches, voltage meters, and optionally a solar tracking system. Each piece of equipment that is intended to be added into a PV system is carefully selected. This is so that output and energy storage can be optimized and power loss during power transmission and conversion from direct current (DC) to alternating current (AC) can be reduced.
Scientists from Spectrolab, which is a subsidiary of Boeing, have reported the development of multi-junction solar cells with an efficiency of more than 40%. That is a new world record for solar photovoltaic cells. Aside from that, the Spectrolab scientists also project that concentrator solar cells could achieve efficiencies of more than 45% or even 50% in the future, with theoretical efficiencies being about 58% in cells with more than three junctions.
As of right now, the best achieved sunlight conversion rate, or solar module efficiency, is around 21.5% in new commercial products. This is typically lower than the efficiencies of their cells in isolation. The most efficient mass-produced solar modules have power density values of up to 175 W/m2 (16.22 W/ft2).
A research conducted by Imperial College, London has revealed that the efficiency of a solar panel can be improved by studding the light-receiving semiconductor surface with aluminum nanocylinders similar to the ridges on Lego blocks. The scattered light then travels along a longer path in the semiconductor, which means that more photons can be absorbed and converted into current. Although these nanocylinders have been used before — aluminum was preceded by gold and silver — the light scattering that occurred in the near-infrared region and visible light was absorbed strongly. Aluminum was found to have absorbed the ultraviolet part of the spectrum while the visible and near-infrared parts of the spectrum were found to be scattered by the aluminum surface. As a result, the research then argued that this could bring down the cost significantly and improve efficiency as aluminum is more abundant and less costly than gold and silver.
Moreover, the research also noted that the increase in current makes thinner film solar panels technically feasible without “compromising power conversion efficiencies, thus reducing material consumption.”
There are other things to take note of when it comes to the efficiencies of solar panels. The first is the fact that the efficiencies of solar panels can be calculated by the maximum power point (MPP) value of solar panels. Secondly, solar inverters convert the DC power to AC power by performing the MPPT process. This means that solar inverter samples the output Power (I-V curve) from the solar cell and applied the proper resistance (load) to solar cells to obtain maximum power. And finally, the MPP of the solar panel consists of MPP voltage and MPP current. It is a capacity of the solar panel and the higher value can make higher MPP.
Micro-inverted solar panels are wired in parallel, which produces more output than normal panels which are wired in series with the output of the series determined by the lowest performing panel. This is also known as the “Christmas light effect.” Micro-inverters work independently, so each panel contributes its maximum possible output given the available sunlight.
Differences Between Solar Cells, Solar Modules, Solar Panels, and Solar Arrays
With the wide array of solar products that are available nowadays, it is quite easy to get a few of them jumbled up. To be more specific, solar cells, solar modules, solar panels, and solar arrays are oftentimes interchangeable for some people. However, it should be noted that these four actually have differences from each other.
To begin with, a solar cell is the most basic unit of a solar photovoltaic system. It is a thin 6-inch square tablet of silicon crystalline substance. They key characteristic of a solar cell is that each of them produces about 0.5-voltage output when exposed to light.
A solar panel is a component with a typically rectangular flat or curved surface that is placed onto a surface, usually with a support structure. It is oftentimes interchangeably referred to as a solar module since a solar PV panel is manufactured as a standard solar system module. However, a solar module is a standardized independent unit within a more complex structure or system. Modules can easily be used to set up or construct the solar PV system. Basically, the solar panel is often a module that is composed of multiple solar cells that are mounted together in series to produce a set voltage output.
And finally, a solar array is the PV part of the solar power generating system that is composed of multiple PV panels or modules. The array can be connected so as to deliver a particular DC output to an inverter that provides AC voltage into the home or can be exported to the electric utility grid.
Technology behind Solar Panels
Most solar modules are currently produced from crystalline silicon (c-Si) solar cells that are made of multi-crystalline and monocrystalline silicon. In 2013, crystalline silicon accounted for more than 90% of worldwide PV production. Meanwhile, the rest of the overall market is made up of thin-film technologies that are using cadmium telluride, CIGS, and amorphous silicon.
An emerging third generation of solar technologies makes use of advanced thin-film cells. They produce a relatively high-efficiency conversion for the low cost compared to other solar technologies.
Additionally, high-cost, high-efficiency, and close-packed rectangular multi-junction (MJ) cells are preferably used in solar panels on spacecraft since they offer the highest ratio of generated power per kilogram lifted into space. MJ cells are compound semiconductors and are made of gallium arsenide (GaAs) and other semiconductor materials.
Another emerging PV technology using MJ cells is concentrator photovoltaics (CPV). CPV also generates electricity from sunlight, but unlike conventional photovoltaic systems, it uses lenses or curved mirrors to focus sunlight onto small, highly efficient, MJ solar cells. Additionally, CPV systems often use solar trackers and sometimes a cooling system to further increase their efficiency.
A thin-film solar cell is a second-generation solar cell that is made by depositing one or more thin layers or thin-film (TF) of photovoltaic material on a substrate, such as glass, plastic, or metal. Thin-film solar cells are commercially used in several technologies, including cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous thin-film silicon (a-Si, TF-Si).
In rigid thin-film modules, the cell and the module are manufactured in the same production line. The cell is created on a glass substrate or superstate, and the electrical connections are created in situ, a so-called “monolithic integration.” The substrate or superstate is laminated with an encapsulant to a front or back sheet, usually another sheet of glass. The main cell technologies in this category are CdTe, a-Si, a-Si+uc-Si tandem, or CIGS (or variant). Amorphous silicon has a sunlight conversion rate of 6-12%.
Flexible thin-film cells and modules are created on the same production line by depositing the photoactive layer and other necessary layers on a flexible substrate. If the substrate is an insulator, like polyester or polyimide film, then monolithic integration can be used. But if it is a conductor, then another technique for electrical connection must be used. The cells are assembled into modules by laminating them to a transparent colorless fluoropolymer on the front side (usually ETFE or FEP) and a polymer suitable for bonding to the final substrate on the other side.
Crystalline silicon (c-Si) is the crystalline forms of silicon, either multi-crystalline silicon (multi-Si) that consists of small crystals or monocrystalline silicon (mono-Si) which is a continuous crystal. Crystalline silicon is the dominant semiconducting material that is used in photovoltaic technology for the production of solar cells. These cells are then assembled into solar panels as part of a photovoltaic system to generate solar power from sunlight.
Solar cells that are made of crystalline silicon are usually called conventional, traditional, or first-generation solar cells. This is because they were developed in the 1950s and remained the most common type up to the present time. Because of the fact that solar cells made of crystalline silicon are produced from 160-190 micrometer thick solar wafers, they are oftentimes called wafer-based solar cells.
Furthermore, solar cells that are made from c-Si are single-junction cells and are generally more efficient than their rival technologies, which are the second-generation thin-film solar cells, such as CdTe, CIGS, and amorphous silicon. In particular, amorphous silicon is an allotropic variant of silicon, and amorphous means “without shape” to describe its non-crystalline form.
Organic Solar Cell
An organic solar cell (OSC), also known as a plastic solar cell, is a type of photovoltaic that makes use of organic electronics, which is a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect. Most organic photovoltaic cells are polymer solar cells.
The molecules used in organic solar cells are solution-processable at high throughput and are cheap, thus resulting in low production costs to fabricate a large volume. Combined with the flexibility of organic molecules, organic solar cells are potentially cost-effective for photovoltaic applications. In addition to that, the optical absorption coefficient of organic molecules is high, so a large amount of light can be absorbed with a small number of materials, usually on the order of hundreds of nanometers.
The primary disadvantages that are associated with organic photovoltaic cells are low efficiency, low stability, and low strength compared to inorganic photovoltaic cells such as silicon solar cells.
Additionally, when compared to silicon-based devices, polymer solar cells are lightweight (which is important for small autonomous sensors), potentially disposable and inexpensive to fabricate, flexible, customizable on the molecular level, and potentially have a less adverse environmental impact. Polymer solar cells also have the potential to exhibit transparency, thus suggesting applications in windows, walls, and flexible electronics.
The inefficiency and stability problems that polymer solar cells have, along with their promise low costs, actually made them a popular field in solar cell research. As of 2015, polymer solar cells were able to achieve over 10% efficiency via a tandem structure. In 2018, a record-breaking efficiency for organic photovoltaics of 17.3% was reached via a tandem structure.
Monocrystalline vs. Polycrystalline
As the name suggests, both monocrystalline and polycrystalline are types of solar cells that are made from crystalline silicon. To start with, monocrystalline is the oldest and most developed of the current solar cell technologies. Monocrystalline panels are created from a single continuous crystal structure. As such, they can be identified as the solar cells that all appear as a single flat color.
On the other hand, polycrystalline solar panels are made from silicon as well. However, instead of using a single crystal of silicon, manufacturers melt many fragments of silicon together to form the wafers for the panel. Because of this, polycrystalline solar panels are also sometimes referred to as “multi-crystalline” or many-crystal silicon. Additionally, polycrystalline solar panels tend to have a blue hue instead of the black hue of monocrystalline panels.
Between the two, monocrystalline solar panels are generally thought of as the premium solar product. This is because the cells are composed of a single crystal, thus allowing the electrons that generate a flow of electricity to have more room to move. In other words, monocrystalline panels have higher efficiencies, and they also have sleeker aesthetics.
Meanwhile, since polycrystalline have many crystals in each cell, there is less freedom for the electrons to move. As a result, they have lower efficiency ratings than monocrystalline panels. That said, however, polycrystalline solar panels have the main advantage of a lower price point. That is why they are still popular in the solar industry as of right now.
Transparent Solar Panel
As the name suggests, a transparent solar panel is a solar panel that is either partially or completely transparent. Conventional solar panels absorb sunlight and convert photons into usable energy. The difficulty with making transparent solar panels is that the sunlight passes through the transparent material. This means that the process that generates the electricity in the solar cell cannot be started because no light is absorbed.
As of right now, there is still a long way to go before transparent solar panels become a reality. But there have already been innovations that will definitely lead to the progress of this particular technology.
Nanoparticle Solar Panels
Silicon nanoparticles exhibit many useful properties — some of which include an active surface state, low bulk density as well as unique photoluminescent and biocompatible properties. As a result, these nanoparticles are usually incorporated into lithium-ion batteries, solar energy cells, micro, and integrated semiconductors, and luminescent display devices. When applied for solar energy products, the size and microstructure of silicon nanoparticles, including their luminescence and quantum efficiency properties, are highly specific.
Nanotechnology offers a lot of benefits for the manufacturing of solar panels. In particular, it reduces manufacturing costs as a result of using a low-temperature process instead of the high-temperature vacuum deposition process that is typically used to produce conventional cells made with crystalline semiconductor materials. Additionally, it also reduces installation costs, achieved by producing flexible rolls instead of rigid crystalline panels.
As of right now, available nanotechnology solar cells are not as efficient as traditional ones, but the lower cost offsets this. In the long run, nanotechnology versions should both be lower cost and, using quantum dots, should be able to reach higher efficiency levels than conventional ones.
Infrared Plastic Solar Cell
Researchers at Idaho National Laboratory, along with partners at Lightwave Power Inc. in Cambridge, MA and Patrick Pinhero of the University of Missouri, have devised an inexpensive way to produce plastic sheets containing billions of nanoantennas that collect heat energy generated by the sun and other sources. These nanoantennas target mid-infrared rays, which the Earth continuously radiates as heat after absorbing energy from the sun during the day. Aside from that, double-sided nanoantenna sheets can also harvest energy from different parts of the sun’s spectrum. This is an advantage considering that traditional solar cells can only use visible light, thus rendering them idle after dark.
With this, the next generation of solar cells could be produced using a new semiconductor alloy that can capture the near-infrared light on the leading edge of the visible light spectrum. In other words, this infrared plastic solar cell can turn the sun’s power into electric energy even on a cloudy day. Just like the nanoparticle solar cells, infrared plastic solar cells also make use of nanotechnology.
UV Solar Cell
Japan’s National Institute of Advanced Industrial Science and Technology (AIST) has succeeded in developing a transparent solar cell that utilizes ultraviolet (UV) light to generate electricity but allows visible light to pass through it. This transparent, UV-absorbing system was achieved by using an organic-inorganic heterostructure made of the p-type semiconducting polymer PEDOT: PSS film deposited on a Nb-doped strontium titanate substrate.
These solar cells are only activated in the UV region and result in a relatively high quantum yield of 16% electron/photon. Future work in this technology involves replacing the strontium titanate substrate with a strontium titanate film deposited on a glass substrate in order to achieve low-cost, large-area manufacturing.
Photovoltaic (PV) vs. Concentrated Solar Power (CSP)
Currently, there are two technologies that are dominating the solar power industry. These two are the Concentrated Solar Power (CSP) and Photovoltaic (PV). Even though these two make use of the sun to generate electricity, they are still highly different from each other.
To begin with, the concentrated solar power (CSP) technology uses the sun’s radiation to heat a liquid substance that will be used to drive a heat engine and drive an electric generator. The photovoltaic (PV) technology, on the other hand, uses sunlight through the photovoltaic effect, which is the creation of voltage and electric current in a material upon exposure to light, to generate an electric current.
Both CSP and PV have their own advantages and disadvantages. When it comes to energy storage and efficiency, CSP is superior because it can store energy with the help of Thermal Energy Storage (TES) technologies. This is something that PV can’t do. PV is incapable of producing or storing thermal energy since they use sunlight directly to generate electricity. There have been efforts to find a way to store energy from PV, but still, it’s quite difficult to achieve that.
Even though CSP is clearly the more efficient one in terms of saving energy, that doesn’t mean it’s the preferred option. Between the two, PV is cheaper, so energy investors are more inclined to use it than CSP. In other words, PV is more accessible than CSP, so it’s the favored one.
What are Smart Solar Modules?
Several companies have begun embedding electronics into PV modules so as to allow the individual modules to perform maximum power point tracking (MPPT). Additionally, embedding electronics also enables the measurement of performance data for monitoring and fault detection at the module level. Some of these solutions make use of power optimizers. And as of 2010, such electronics can also compensate for shading effects, wherein a shadow falling across a section of a module causes the electrical output of one or more strings of cells in the module to fall to zero but not having the output of the entire module fall to zero.
Smart modules are a type of solar panel that has a power optimizer embedded into the solar module at the time of manufacturing. Usually, the power optimizer is embedded in the junction box of the solar module. Power optimizers that are attached to the frame of a solar module, or connected to the photovoltaic circuit through a connector, are not properly considered smart modules.
Smart modules actually differ from traditional solar panels. This is because the power electronics embedded in the module offers enhanced functionality such as panel-level maximum power point tracking, monitoring, and enhanced safety.
A solar micro-inverter is a plug-and-play device used in photovoltaics that converts direct current (DC) generated by a single solar module to alternating current (AC). Microinverters contrast with conventional string and central solar inverters, in which a single inverter is connected to multiple solar panels. The output from several microinverters can be combined and usually fed to the electrical grid.
Microinverters have several advantages over conventional inverters. The primary advantage is that they electrically isolate the panels from each other, so small amounts of shading, debris or snow lines, on any of the solar modules, or even a complete module failure, does not disproportionately reduce the output of the entire array. Each of the microinverters harvests optimum power by performing maximum power point tracking (MPPT) for its connected module. Other advantages include simplicity in system design, lower amperage wires, simplified stock management, and added safety.
On the other hand, the main disadvantage of a microinverter is a higher initial equipment cost per peak watt than the equivalent power of a central inverted since each inverter needs to be installed adjacent to a panel (usually on a roof). Aside from that, this also makes microinverters harder to maintain and more costly to remove and replace. Some manufacturers have addressed these problems by producing panels with built-in microinverters.
A microinverter has often a longer lifespan than a central inverter, which will need replacement during the lifespan of the solar panels. As a result, the financial cost is a disadvantage at first, but it may become an advantage in the long term.
Performance and Degradation of Solar Panels
Module performance is typically rated under standard test conditions (STC): irradiance of 1,000 W/m2, a solar spectrum of AM 1.5, and module temperature at 25℃. The actual voltage and current output of the module changes as lighting, temperature, and load conditions change. Because of this, there is never just one specific voltage, current, or wattage at which the module operates. Additionally, performance varies depending on the time of day, amount of solar insolation, direction and tilt of modules, cloud cover, shading, temperature, geographic location, and day of the year.
In order to achieve optimum performance, a solar panel has to be made of similar modules that are oriented in the same direction perpendicular towards direct sunlight. The path of the sun varies by latitude and day of the year, and it can be studied using a sundial or a sun chart and tracked using a solar tracker. Differences in voltage or current of modules may affect the overall performance of a panel. That is why bypass diodes are used to circumvent broken or shaded panels to optimize output.
Electrical characteristics of a solar panel include nominal power (PMAX, measured in W), open-circuit voltage (VOC), short circuit current (ISC, measured in amperes), maximum power voltage (VMPP), maximum power current (IMPP), peak power (Wp), and module efficiency (%).
- Nominal voltage refers to the voltage of the battery that the module is best-suited to charge. This is a leftover term from the days when solar modules were only used to charge batteries. At a glance, the nominal voltage allows users to make sure the module is compatible with a given system.
- Open-circuit voltage is the maximum voltage that the module can produce when not connected to an electrical circuit or system. VOC can be measured with a voltmeter directly on an illuminated module’s terminals or on its disconnected cable.
- Peak power is the maximum output under standard test conditions but not the maximum possible output. Typical modules, which could measure approximately 1 m x 2 m (3 ft 3 in x 6 ft 7 in), will be rated from as low as 75 W to as high as 350 W, depending on their efficiency. At the time of testing, the test modules are binned according to their test results. A manufacturer might usually rate their modules in 5 W increments and either rate them at +/-3%, +/-5%, +3/-0%, or +5/-0%.
The ability of solar modules to withstand damage by rain, hail, heavy snow load, and cycles of heat and cold varies by manufacturer. Fortunately, most solar panels on the U.S. market are UL listed, which means that they have gone through testing to withstand hail. A lot of the crystalline silicon module manufacturers offer a limited warranty that guarantees electrical production for 10 years at 90% of rated power output and 25 years at 80%.
Potential induced degradation (PID) is potential induced performance degradation in crystalline photovoltaic modules, caused by so-called stray currents. This effect may cause a power loss of up to 30%.
The largest challenge for PV technology is reported to be the purchase price per watt of electricity produced. New materials and manufacturing techniques continue to improve the price of power performance. The problem resides in the enormous activation energy that must be overcome for a photon to excite an electron for harvesting purposes. Additionally, advancements in photovoltaic technologies have brought about the process of “doping” the silicon substrate to lower the activation energy, thus making the panel more efficient in converting photons to retrievable electrons.
Furthermore, chemicals such as boron (p-type) are applied to the semiconductor crystal in order to create donor and acceptor energy levels substantially closer to the valence and conductor bands. In doing so, the addition of boron impurity enables the activation energy to decrease 20-fold from 1.12 eV to 0.05 eV. Since the potential difference (EB) is so low, the Boron is able to thermally ionize at room temperatures. This enables for free energy carriers in the conduction and valence bands, thus allowing greater conversion of photons and electrons.
Maintenance of Solar Panels
Solar panel conversion efficiency, which usually falls in the 20% range, is reduced by dust, grime, pollen, and other particulates that accumulate on the solar panel. In fact, Seamus Curran, who is an associate professor of physics at the University of Houston and director of the Institute for NanoEnergy, has asserted that a dirty solar panel can reduce its power capabilities by up to 30% in high dust or pollen or desert areas.
With that said, paying to have solar panels cleaned is actually not a good investment. This is because researchers have found out that panels that had not been cleaned or rained on for 145 days during a summer drought in California lost only 7.4% of their efficiency.
Overall, for a typical residential solar system of 5 kW, washing panels halfway through the summer would translate into a mere $20 gain in electricity production until the summer drought ends, which was about 2 and a half months. Meanwhile, for larger commercial rooftop systems, the financial losses are bigger but still rarely enough to warrant the cost of washing the panels. On average, panels lost a little less than 0.05% of their overall efficiency per day.
Recycling of Solar Panels
Most parts of a solar module can be recycled including up to 95% of certain semiconductor materials or the glass, as well as large amounts of ferrous and non-ferrous metals. A few private companies and non-profit organizations are currently engaged in take-back and recycling operations for end-of-life modules.
Recycling possibilities depend on the kind of technology that is used in the modules. Some of the possibilities are the following:
- Silicon-based modules. Aluminum frames and junction boxes are dismantled manually at the beginning of the process. After that, the module is then crushed in a mill, and the different fractions are separated — glass, plastics, and metals. It is possible to recover more than 80% of the incoming weight. This process can be performed by flat glass recyclers since the morphology and composition of a PV module is similar to those flat glasses that are used in the building and automotive industry. For example, the recovered glass is readily accepted by the glass foam and glass insulation industry.
- Non-silicon-based modules. These require specific recycling technologies, such as the use of chemical baths in order to separate the different semiconductor materials. For example, for cadmium telluride modules, the recycling process starts by crushing the module and subsequently separating the different fractions. This recycling process is designed to recover up to 90% of the glass and 95% of the semiconductor materials contained. Some commercial-scale recycling facilities have been created in recent years by private companies. As for aluminum flat plate reflectors: the trendiness of the reflectors has been brought up by fabricating them using a thin layer (around 0.016 mm to 0.024 mm) of Aluminum coating present inside the non-recycled plastic food packages.
Since 2010, there is an annual conference in Europe that brings together manufacturers, recyclers, and researchers to look at the future of PV module recycling. This conference is called the International Conference on PV Module Recycling.
Solar Panel Manufacturers
In 2010, a total of 15.9 GW of solar PV system installations were completed. During the same year, the solar PV pricing survey and market research company PVinsights reported that there was a growth of 117.8% in solar PV installation on a year-on-year basis.
Because of the over 100% year-on-year growth in PV system installation, PV module manufacturers dramatically increased their shipments of solar modules in 2010. They actively expanded their capacity and turned themselves into GW players. According to PVinsights, five of the top ten PV module companies in 2010 are GW players.
The basis of producing solar panels revolves around the use of silicon cells. These silicon cells are usually 10-20% efficient at converting sunlight into electricity, with newer production models now exceeding 22%. So as to make solar panels more efficient, researchers all over the world have been trying to develop new technologies to make solar panels more effective at turning sunlight into energy.
As of right now, there are thousands of solar panel manufacturers all over the world. The following are only some of them.
Top Solar Panel Manufacturers in China
- Trina Solar. Founded in 1997, Trina Solar Ltd. delivers PV products, applications, and services to promote global sustainable development.
- China Sunergy. Founded in 2006, China Sunergy specializes in creating solar cells from silicon wafers, and they both use monocrystalline and multi-crystalline silicon solar cells for this.
- DelSolar Co., Ltd. is a solar company that engages in the research, design, manufacture, and distribution of solar cells, solar modules, as well as the development of the photovoltaic system.
- JA Solar Holdings. Founded in 2005, JA Solar Holdings covers the design, development, manufacturing, and sale of silicon wafers, batteries, modules, and photovoltaic power plants.
- Motech Industries. Founded in 1981, Motech Industries Inc., also known as Motech Solar, is dedicated to the research, development, and manufacture of high-quality solar products and services, ranging from photovoltaic (PV) cells, PV modules, to PV systems.
- Suntech Power. Founded in 2001, Suntech Power Holdings Co., Ltd. is engaged in the research, development, and production of crystalline silicon solar cells and modules.
- Yingli Solar. Yingli Solar, formerly known as Yingli Green Energy Holding Company Limited, covers the manufacturing of the photovoltaic value chain from ingot casting and wafering through solar production and solar panel assembly.
- Jinko Solar. Jinko Solar is a solar panel manufacturer headquartered in Shanghai. Founded in 2006, the company started out as a wafer manufacturer and went public on the New York Stock Exchange in 2010.
- Shunfeng International Clean Energy. Shunfeng International Clean Energy Limited, commonly known as SFCE Solar, aims to create a low-carbon environment through its integrated photovoltaic services and solar power stations constructions and operations, and manufacturing of solar power products as well as solar energy storage.
- Hanwha Q CELLS. Founded in 2012, Hanwha Q CELLS company is known for its high-quality, high-efficiency solar cells and solar modules, and it offers a wide variety of photovoltaic products, applications and solutions, solar modules, solar kits, and also large-scale solar power plants.
Top Solar Panel Manufacturers in the Middle East and North Africa (MENA) Region
- A.R.E. Group. The A.R.E. Group was established in October 2014 with the primary goal of bringing state-of-the-art solar solutions and silicon technologies to Egypt.
- SARL Algerian PV Company. Established in 2010 in Algeria, SARL Algerian PV Company, or ALPV for short, is a company that is engaged primarily in the manufacturing of solar PV panels.
- Atom Enerji. Since the company’s establishment in 2012, Atom Enerji has manufactured primarily solar panels and off-grid solar system equipment.
- Aures Solaire. Aures Solaire is a solar panel manufacturer that is based in Algeria.
- Aurasol. Established in April 2011, Aurasol is a company based in Tunisia that engages primarily in the renewable energy sector.
- Copex Solar Energy Systems and Trading. Copex Solar Energy Systems and Trading is a renowned manufacturer of power backup and power conditioning systems that was established in 2012 at Dubai, U.A.E.
- Cleanergy Morocco. Established in 2010, Cleanergy Morocco is a company created by engineers with long experience in the high technology industrial field as well as practical experience for the preservation of the environment.
- DuSol Industries. DuSol Industries is the first PV module manufacturing company that is based in Dubai, U.A.E.
- Egyptian German Co. Trading and Supply. Egyptian German Co. Trading and Supply (EGTS) is a company that aims to introduce the solar energy system to the Egyptian market.
- Emirates Insolaire. Established in 2013 in Dubai, U.A.E., Emirates Insolaire LLC is a joint venture of Dubai Investments PJSC and SwissINSO Inc. that specializes in the manufacturing of solar products.
Top Solar Panel Manufacturers in India
- Vikram Solar. Formerly known as Vikram Solar Pvt. Ltd. is a company that specializes in high-efficiency PV module manufacturing comprehensive solutions.
- Waaree Energies. Founded in 1989 in Mumbai, India, Waaree Energies Ltd. is a solar manufacturing company that focuses on providing EPC services, project development, rooftop solutions, solar water pumps, as well as an Independent Power Producer.
- Goldi Green Technologies. Goldi Green Technologies only began in 2011 with a 10 MW production capacity, but despite its humble beginnings, the company has become one of the fastest-growing solar PV module manufacturers.
- Tata Power Solar. Tata Group was established by Jamsetji Tata in the second half of the 19th century, thus making it one of the biggest and most respected business organizations in the world.
- Loom Solar. Loom Solar is an Indian solar brand store that sells solar systems, solar panels, solar inverters, and solar chargers.
- Moser Baer Solar. Established in 1983 in New Delhi, Moser Baer India Ltd. (MIBL) is one of the leading technology companies in India.
- XL Energy. Formerly known as XL Telecom and Energy Limited, XL Energy Limited aims to provide end-to-end solutions in the field of solar power with expertise in the field of production of solar PV modules.
- Emmvee Photovoltaics. Since its founding in 1992, Emmvee Photovoltaics Private Limited has been developing various centers of excellence in solar water heating systems, photovoltaics, and other industrial products.
- Navitas Green Solutions. Navitas Solar is the latest venture into renewable energy by a group of companies that have a rich history of over four decades in engineering and manufacturing activities.
- Saatvik Green Energy. Saatvik Green Energy actively supports the global effort to energize the world through alternate and greener sources of energy.
Top Solar Panel Manufacturers in Europe
- SolarWorld. SolarWorld is a German company that is dedicated to the manufacturing and marketing of photovoltaic products all over the world.
- REC Group. Based in Norway, REC Group was founded in 1996 and has since become one of the world’s leading providers of solar energy solutions.
- Kioto Solar. Founded in 2007, Kioto Solar is an Austria-based provider of solar thermal and PV systems.
- Photowatt. Photowatt is a manufacturer of photovoltaic panels from France.
- Victron Energy. Victron Energy is a solar manufacturing company that was founded in 1975 in the Netherlands.
- Lorentz. Founded in Germany in 1993, Lorentz is a company that has pioneered, innovated, and excelled in the engineering and manufacturing of solar-powered water pumping.
- ATERSA Group. From the company’s establishment, ATERSA has developed, manufactured, and commercialized all the components needed for the configuration of a solar PV system.
- Megasol Energy. Founded by Markus Gisler when he was only 12, Megasol Energy has transformed from being a garage company to becoming one of the leading solar manufacturing companies in all of Europe.
- AE Solar. Founded by Dr. Alexander Maier and his brothers Waldemar Maier and Victor Maier, AE Solar GmbH is a German renewable energy manufacturing company.
- Luxor Solar. Luxor Solar is a premium manufacturer for solar modules since 2004.
Top Solar Panel Manufacturers in the United States of America
- SolarTech Universal. SolarTech Universal is an American solar panel manufacturing company that is based in Riviera Beach, Florida.
- SunSpark Technology. SunSpark Technology is relatively new to the solar panel manufacturing business, but the company is still considered as a globally recognized brand for solar panel manufacturers.
- SolarWorld Americas. Founded in 1975 as Solar Technology International, SolarWorld Americas is the longest operating solar manufacturer in the Earth’s western hemisphere.
- Tesla Energy/Panasonic. In 2018, Tesla Energy has partnered with Panasonic to manufacture solar panels in the United States.
- CertainTeed Solar. Founded in 1904 as General Roofing Manufacturing Company, CertainTeed is one of the leading brands of exterior and interior building products in North America.
- First Solar. First Solar has developed, financed, engineered, constructed, and operated many of the world’s largest grid-connected PV power plants.
- Global Solar Energy. Founded in 1996, Global Solar Energy has evolved into a leading manufacturer of thin-film Copper Indium Gallium diSelenide (CIGS) solar solutions.
- GreenBrilliance. GreenBrilliance is a vertically integrated, end-to-end alternate energy services provider.
- LG Solar U.S.A. LG manufactures and sells a wide variety of electronic products, and as of right now, they have started to manufacture and sell solar panels as well.
- Lumos Solar. Founded in 2006, Lumos Solar is committed to facilitating the widespread adoption of solar energy as they believe that this is the way to ensure the future health of our planet.
Solar Panel Pricing
Over the last four decades, the cost of solar panels has dropped by 99%, and as of right now, the cost is still continuing to fall. As a result, solar electrical power is now cheaper than running existing coal, and it is projected to become cheaper than fossil fuels by 2020. This phenomenon of alternative energy like solar being able to generate power at a Levelized cost of electricity that is less than or equal to the price of power from the electricity grid is also known as grid parity.
The average pricing information is divided into three pricing categories. These are the small quantity buyers (modules of all sizes in the kilowatt range annually), the mid-range buyers (usually up to 10 MWp annually), and the large quantity buyers (they have the access to the lowest prices).
As was mentioned, there has been a noticeable systematic reduction in the price of solar cells and modules. For example, in 2012, it was projected that the quantity cost per watt was about $0.60, which was about 250 times lower than the cost per watt in 1970 of $150. Furthermore, a 2015 study has shown that price/kWh is dropping by 10% per year since 1980, and it also predicts that solar could contribute 20% of total electricity consumption by 2030. Meanwhile, the International Energy Agency has predicted that solar could contribute 16% of total electricity consumption by 2050.
Real-world energy production costs heavily depend on local weather conditions. For example, in a cloudy country like the United Kingdom, the cost per watt produced kWh is higher compared to those countries that are sunny, like Spain.
With the prices of solar panels continually dropping, the Energy Information Administration has reported that prices per megawatt-hour are expected to converge and reach parity with conventional energy production sources during the period of 2020-2030. Additionally, the same organization has said that the parity can be achieved without any need for subsidy support and can be accomplished through organic market mechanisms, such as production price reduction and technological advancement.
For merchant solar power stations, where the electricity is being sold into the electricity transmission network, the cost of solar energy will have to match the wholesale electricity price. This point is oftentimes referred to as “wholesale grid parity” or “busbar parity.”
Some photovoltaic systems, like rooftop installations, can provide power directly to an electricity user. In these cases, the installation can be competitive when the output cost matches the price at which the user pays for his electricity consumption. This case is oftentimes known as “retail grid parity,” “socket parity,” or “dynamic grid parity.” In 2012, UN-Energy conducted research where they suggested that areas of sunny countries with high electricity prices, such as Italy, Spain, and Australia, and areas using diesel generators have already reached retail grid parity.
Solar Panel Mounting
Ground-mounted photovoltaic systems are usually large, utility-scale solar power plants. Because of this, their solar modules have to be held in place by racks or frames that are attached to ground-based mounting supports.
Ground-based mounting supports include:
- Pole mounts, which are driven directly into the ground or embedded in concrete
- Foundation mounts, such as concrete slabs or poured footings
- Ballasted footing mounts, such as concrete or steel bases that make use of weight to secure the solar module system in position and do not require ground penetration. This kind of mounting system is perfect for sites where excavation is not possible. Some examples for sites like this are capped landfills. Because of the nature of this kind of mounting system, decommissioning or relocation of solar module systems is simplified.
Ground-based mounting supports are not the only mounting options for solar systems. Another popular choice is the roof-mounted solar power systems, and as the name suggests, these consist of solar modules that are held in place by racks and frames attached to roof-based mounting supports.
Roof-based mounting supports include:
- Rail mounts, which are attached directly to the roof structure and may use additional rails for attaching the module racking or frames
- Ballasted footing mounts, such as concrete or steel bases that make use of weight to secure the panel system in position. This kind of mounting support does not require through penetration, and it also allows for decommissioning or relocation of solar panel systems with no adverse effect on the roof structure.
- All wiring connecting adjacent solar modules to the energy harvesting equipment must be installed according to local electrical codes and should be run in a conduit appropriate for the climate conditions.
And the third common choice for mounting supports is the solar carport system.
As the name suggests, a solar carport mounting system is an overhead canopy that is built to cover parking areas. This kind of mounting system actually shares quite a number of similarities with ground-mounted solar systems. The similarity is seen at the fact that both ground-mounted solar systems and solar carport mounting systems get rid of the need for a surface on which the panels can be mounted. The only obvious difference between these two is that solar carports are taller in terms of structure because they need to have space for a car to park.
The greatest advantage of solar carport mounting systems is that they don’t require additional land for the installation. As a result, this kind of solar system offers more efficient use of space than the other kinds, even the ground-mounted ones. Long story short, solar carport mounting systems have fewer restraints and conflicts than their other kinds of solar systems, thus making them preferable for some people.
What are Solar Trackers?
In order to maximize the energy output, sometimes, solar panel systems have solar trackers. This is because the primary purpose of a solar tracker is to direct solar panels or modules toward the sun. Solar trackers sense the direction of the sun, and as a result, their orientation always has to change throughout the day so as to follow the sun’s path and maximize energy capture.
In solar PV systems, solar trackers help minimize the angle of incidence — also known as the angle that a ray of light makes with a line perpendicular to the surface — between the incoming light and the panel. As a result, the amount of energy that the installation produces will be increased.
There are two kinds of solar trackers that are popular nowadays. The first one is the single-axis solar tracker, which is the one that rotates on one axis moving back and forth in a single direction. Under single-axis solar trackers, there are subtypes, namely horizontal, vertical, tilted, and polar aligned — all of them rotate as their names suggest.
The second kind of solar tracker is the dual-axis tracker, which is the one that continually faces the sun since they can move in two different directions. The subtypes under this include tip-tilt and azimuth-altitude. Dual-axis tracking is commonly used to orient a mirror and redirect sunlight along a fixed axis towards a stationary receiver.
Solar Panel Quality Standards
In order to make sure that the solar panels are of high-quality and are ready to be sold, manufacturers follow standards that are established by certification companies. The most popular certification company that manufacturers adhere to is the International Electrotechnical Commission (IEC). The IEC is a Swiss association that acts as an international standards organization that prepares and publishes international standards for all electrical, electronic, and related technologies that are collectively known as “electrotechnology.”
IEC standards cover a wide array of technologies — from power generation, transmission, and distribution to home appliances and office equipment, semiconductors, fiber optics, batteries, solar energy, nanotechnology, and marine energy. For solar panels, the standards or certification that manufacturers follow are IEC 61215 (crystalline silicon performance), IEC 61646 (thin-film performance), and IEC 61730 (safety of all modules).
Another popular certification company is the Underwriters Laboratories (UL). UL is one of several companies approved to perform safety testing by the U.S. federal agency Occupational Safety and Health Administration (OSHA). The standards from UL that solar panel manufacturers use are UL 1703, UL 1741, and UL 2703.
Manufacturers also adhere to the standards established by CE marking. CE marking is a certification mark that indicates conformity with health, safety, and environmental protection standards for products that are sold within the European Economic Area (EEA). Aside from that, the CE marking is also found on products that are sold outside of the EEA that are manufactured in, or designed to be sold in, the EEA. As a result, this makes the CE marking recognizable all over the world.
What are Solar Connectors?
Outdoor solar panels typically include MC4 connectors while automotive solar panels can opt to include car lighters and USB adapters. Aside from that, indoor panels, including solar PV glasses, thin films, and windows, can integrate microinverters, such as AC solar panels.
Practical Applications of Solar Panels
Solar panels, or photovoltaics in general, offer so many possibilities for practical applications. For one thing, they can be used in agriculture as a power source for irrigation. Aside from that, they can also be used in healthcare to refrigerate medical supplies and for infrastructure. PV modules are also used in photovoltaic systems and include a wide variety of electric devices, such as:
- Photovoltaic power station: also known as a solar park. It is a large-scale photovoltaic system that is designed for the supply of merchant power into the electricity grid.
- Rooftop photovoltaic power station: a photovoltaic system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure.
- Standalone PV system: it is also known as an off-grid system, and it is not connected to the electrical grid.
- Solar hybrid power systems: hybrid power systems that combine solar power from a photovoltaic system with another power generating energy source.
- Concentrated photovoltaics: a photovoltaic technology that uses lenses or curved mirrors to focus sunlight onto small, highly efficient, multi-junction solar cells, so as to generate electricity.
- Solar vehicles: electric vehicles that are powered completely or significantly by direct solar energy.
- Solar planes
- Solar-pumped lasers
- Solar panels on space crafts and space stations
Largest Solar Power Plants in the World
As solar keeps getting bigger, more and more solar power plants are being constructed all over the world. Because of this, the list of largest solar power plants in the world is ever-changing. That said, the five solar power plants are the largest out of all the existing ones as of right now:
- Sweihan Independent Power Project. The Sweihan power project is a solar photovoltaic (PV) independent power project (IPP) that was originally proposed to be a 350 MW project. But because of the availability of additional land, the capacity has been increased to 1,177 MW. This plant is being constructed on a 780 ha site in the eastern part of Abu Dhabi.
- Longyaxia Dam Solar Power Park. The Longyangxia Dam is a concrete arch-gravity dam that was initially built for the purposes of hydroelectric power generation, irrigation, ice control, and flood control. But in 2013, a solar PV station was built, and this station, named the Longyangxia Dam Solar Power Park, was completed in 2015. The completed solar power park has a capacity of 850 MW, which can generate about 200,000 households.
- Bhadla Solar Park. Bhadla Solar Park is one of the largest solar parks in India. Spread over a total area of 10,000 acres of a sandy, dry, and arid region, the park currently has the generating capacity of 1,515 MW.
- Pavagada Solar Park. The Pavagada Solar Park is a solar park spread over a total area of 13,000 acres. Currently, the generating capacity of the Pavagada Solar Park is 1,400 MW.
- Kurnool Ultra Mega Solar Park. The Kurnool Ultra Mega Solar Park is a solar park that is spread over a total area of 5,932.32 acres in the Gani and Sakunala villages of Kurnool district. Its total generating capacity is 1,000 MW.
Solar Panel Limitations
Pollution and Energy in Production
Generally speaking, solar panels have been well-known for being able to generate clean and emission-free electricity. However, it should be noted that they produce only direct current (DC), which is not what normal appliances use. Because of this, solar PV systems often consist of solar PV panels and inverters, which convert DC to AC.
Furthermore, solar PV panels are chiefly composed of solar photovoltaic cells, which have no fundamental difference to the material for making computer chips. In other words, the process of producing solar PV cells — as well as computer chips — is energy-intensive and involves highly poisonous and environmental toxic chemicals.
On a slightly more positive note, there are a few solar PV manufacturing plants around the world that produce PV modules with energy produced from PV. This measure greatly reduces the carbon footprint during the manufacturing process. Managing the chemicals that are used in the manufacturing process is subject to the factories’ local laws and regulations.
Impact on Electricity Network
With the increasing levels of rooftop photovoltaic systems, the energy flow becomes two-way. When there is more local generation than consumption, electricity is then exported to the grid. However, the electricity network is not traditionally designed to deal with the two-way energy transfer. As a result, some technical issues are bound to happen.
An over-voltage issue may come out as the electricity flows from these PV households back to the network. There are solutions that can be done to manage the over-voltage issue. Some of these solutions include regulating PV inverter power factor, new voltage and energy control equipment at the electricity distributor level, re-conducting the electricity wires, demand-side management, and many more. But even with all these solutions, there are often still limitations and costs that are related to them.
Implication onto Electricity Bill Management and Energy Investment
There is no silver bullet in electricity or energy demand and bill management, simply because customers (sites) have different specific situations. For example, customers have different comfort or convenience needs, different electricity tariffs, or different usage patterns. Electricity tariff may have a few elements, such as daily access and metering charge, energy charge (based on kWh or mWh) or peak demand charge (e.g. a price for the highest 30-minute energy consumption in a month).
Generally, PV is a promising option for reducing energy charges when the electricity price is reasonably high and continuously increasing, such as in Australia and Germany. However, for sites that have peak demand charges in place, PV may be less attractive if peak demands mostly occur in the later afternoon to early evenings, such as in residential communities.
Long story short, energy investment is largely an economical decision. Therefore, it is better to make investment decisions based on systematical evaluation of options in operational improvement, energy efficiency, onsite generation, and energy storage.
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Much of the focus on innovation for solar energy comes down toresearchers trying to create the most efficient and powerful solar cellpossible. Where some choose to focus their vision there, however, others are trying to find a way to ensure that solar energy cells can lastlong enough to make the higher levels of efficiency worthwhile. At 3M, a new ultra thin plastic film has been developed that they believe willallow solar cells to last longer and operate under a greater variety ofconditions.
3M’s decision to begin working on the plastic film was to create a wayto replace glass as the primary means of protecting solar energy cellswhile installed and operating. The way many solar cells work now, thinsheets of glass are mounted on racks that are situated above the solarcells in order to protect them from the elements. Once moisture, inparticular, is introduced to the solar cell, it can result in a totalbreakdown of the cell and a much shorter lifespan. The plastic film isdesigned not only to prevent moisture from reaching the cells but alsoto prevent the reflection of sunlight, allowing a great quantity ofsunlight to be gathered by a solar cell allowing it to create moreenergy. With this new film, however, 3M believes that solar cells willbe able to receive a much higher level of protection as well as pushingflexible solar cells to the limits of their flexibility now that theyare no longer held back by the need to use glass.
While this new film is an exciting development, 3M is quick to note that using plastic to cover solar energy cells is hardly the newest and most original innovation for the solar energy industry. Smaller scale solarcells and panels are frequently covered in plastic. The difference,however, is that those plastics are not meant to last where 3M’s newfilm is believed to have an estimated life of twenty to twenty fiveyears. According to 3M, their new plastic film is made from amultilayer, fluoropolymer-based material and is an impressive twentythree micrometers thick. Ideally, the plastic film would be used tolaminate a solar panel and completely encapsulate it in the plasticmaterial. Once laminated, the 3M allows virtually no moisture into thesystem.
It is believed that 3M will begin offering the film for sale to solarenergy companies sometime next year after they have sorted out a product line to offer potential customers. Derek DeScioli, a businessdevelopment manager at 3M, has said that they already have severalcustomers lined up for the new plastic film. Once it has been released,companies will be able to determine if 3M’s new plastic film is theanswer to the problem of how to create a more flexible and betterprotected solar cell. If it is, then it could only be a matter of timebefore plastic film is the industry standard for covering a solar cell.
Thelatest advancements in technology have made people forget CDs and storetheir favorite music on their portable media devices. However, sincemost of these devices, be it cellphones or iPods, don’t come withhigh-quality integrated speakers, users are mostly left to listeningmusic on their earphones. UK-based Devotec Industries has delivered what many people in the world would have been longing for.
Thecompany has released the world’s first Bluetooth Stereo Speakers, knownas Solar Sound, which are powered by clean solar energy. The deviceplays music through 2 X 2W speakers, which according to the companyoffer superior sound quality. The device can be connected to mostcellphones and music players wirelessly but if your PMP isn’t equippedfor wireless transfer, you can also connect your device with a wire.
Thedevice captures solar energy during the day, which is stored in abuilt-in battery for use when the sun isn’t shining. The devicefeatures touch sensitive controls. The company claims that the 150mAsolar panel is enough to keep the device going for 4 hours at maxvolume.
How much do solar panels decrease over time? The solar industry standard is a conservative estimate of 3% in the first year, and less than 1% per year after that. However, solar panel manufacturers are starting to realize that this is too conservative, and they are beginning to warranty their panels to more realistic degradation rates.
There are three points I want to make.
- Use the solar panel’s warranty to compare output loss over time because that is the only output you are guaranteed.
- Realistically expect less than a 3% decrease in output the first year, and about .5% decrease per year after that for most panels.
- One solar panel from 1979 was tested in 2010 (after 30 years) and its output was better than the original factory specs.
First, the industry standard for solar output warranties is 90% output in year 10, and 80% output in year 25. This is the 2011 warranty for companies such as JA Solar, First Solar, Yingli Solar, Canadian Solar, Sanyo, and Sharp. Right now there is not enough data to know reliable degradation rates after 20-25 years, so you must rely on manufacturer warranties in order to compare expected solar output losses over time.
Now, most solar panels won’t degrade this much. This is just want the manufacturers will guarantee. So, some manufacturers are starting to update their warranties to set themselves apart from the competition. Here is a list of the best warranties available from major solar panel manufacturers.
- SolarWorld and Trina Solar both offer linear performance guarantees which basically means that they are guaranteeing only the small decrease for each year up to 25 years. Technically, it protects you a little more. Check both of their websites to see how they explain it.
- Suntech protects you at year 5, 12, 18, and 25, which gives you more protection than the standard.
- Sunpower warranties 90% to year 12, which is 2 years longer than the standard.
- Every other solar company is the standard – 90% at year 10, and 80% at 25.
Here is a chart comparing the solar output warranties of 10 major companies. Click to enlarge.
Lastly, solar panels will last for more than 30 years. They were originally designed to withstand the conditions in space and to be used in remote places without electricity access. There are no moving parts in a solar panel. The cells are encased in metal and glass frames designed to withstand hurricane winds, rain, hail and other extreme weather conditions.
Martin Holladay bought a panel back in 1980 that was manufactured in 1979. In 2010, he tested the output of his solar panel for the 30 year anniversary. It performed better than expected, returning 97% of the original voltage and more amps than the spec sheet said it should output originally. You can read more here.
Solar will last a long time. Expect a 2% decrease when you install them, and then a reasonable 0.5% per year after that. Let’s hope this article helps improve the 2011 industry standard warranties.
Solar energy is on the cusp of becoming a mainstream form of energy. As moreinformation about alternative energy flies around the Internet, it isimportant to realize that not everything you hear about solar energy is true. Here are the top five myths about going solar:
Myth # 1- Solar energy is too expensive:
There is an upfront cost to convert your home to solar energy, but thatdoesn’t mean it is too expensive. In fact, solar has never been moreaffordable. Depending on your state, there are huge incentives,including tax breaks and Solar Renewable Energy Credits, which can offset some of the upfront cost. The truth is that you can see a return on your investment from Day 1.
Myth # 2 – Solar doesn’t work on cloudy, cold days.
While solar panels work slightly by effectively in direct sun, solarsystems work just fine on cloudy days. Consider that Germany, a countrynot known for its bright, sunny days, is the solar capital of the world. As for the cold? Just because it might be cold, doesn’t mean that there isn’t sunlight. Plus, solar systems actually work better in coldertemperatures since the panels can conduct electricity more efficientlyin milder weather.
Myth # 3 – With all the advancements in solar energy, I should just wait. Prices will come down.
The time to buy is now. While it may be true that the cost of solarpanels might come down, so will the large amount of federal and stateincentives. The solar incentives are not going to be around forever, sowhy not start cutting your electricity bills in half now?
Myth # 4 – I am not going to be in my house long enough to see a return on my investment.
You will still see a return on your investment even if you move out ofyour house just a few years after you install a solar system: it justwon’t come as reduced energy bills. Installing a solar system canincrease your house value by $20,000 for every $1,000 saved in annualutility costs.
Myth # 5- Solar is hard to maintain.
Solar panel systems that are connected to the grid are easy to maintain. They just need to be rinsed off with water occasionally. The onlymaintenance they really require is to be kept free of things like dust,debris and snow. In fact solar panels are made to withstand rain, hail,and pretty much anything Mother Nature can throw at it.
I often refer to Moore’s Law, which posits that the effectiveness oftechnology increases exponentially over time. I talk cavalierly abouthow this “law” (named for Intel co-founder Gordon Moore, whichoriginally applied to the number of transistors that could be crammedonto a semiconductor chip) can be extrapolated to what we’re all tryingto do here in renewable energy.
But how legitimate is all this? Does it apply in some cases, likeIT, and not others, e.g., power engineering? In particular, can we useit to predict accurately the results of our driving the technology ofrenewables forward, as we increase the output of solar, wind, and otherforms of clean energy?
If you want a lecture that is anything but cavalier, I present this talk on Moore’s (and Wright’s) Law at the University of Waterloo, Canada. On the other hand, if you don’t like really academic stuff, you may want to skip this one.
“Oppositions: Pennies From Heaven?” event with Urban Green Council in New York City was a debate aboutwhether solar PV was worth the premium cost compared to lesscapital-intensive strategies such as energy efficiency measures. Theevent felt like the judges had made up their minds beforethe defendants had a chance to testify – the event was hosted at the $1B Bank of America Tower, one of the greenest office buildings in theworld, and yes one that lacks solar PV. But the most damning argumentswere yet to come. Read past the break for the full story and join the Green Light Distrikt Facebook group for updates on new events, blog posts and more.
The event brought together thought leaders from several highly respected organizations:
- Laurie Kerr (LK) from the NYC Mayor’s Office of Long Term Planning and Sustainability (Moderator)
- Bill Guiney (BG) from Johnson Controls’ Global Renewable Energy Development Group
- Nikhil Krishnan (NK) from McKinsey and Company’s Clean Technology Practice
- Richard Perez (RP) from SUNY Albany’s Atmospheric Sciences Research Center.
While the panel was defined as a “lively debate” and the moderatorjoked that following the panel “there would be a fight in the parkinglot,” most of the speakers agreed on the issues, including the argumentthat energy efficiency strategies should be the first strategy todecrease fossil fuel energy use. The following is a transcript of thediscussion. In the interest of time, I have paraphrased all comments and listed speakers by their abbreviations. In order to give you a chanceto decide for yourself, I have saved my comments for the end of thepost.
Transcript from Oppositions: Pennies from Heaven?
Question #1: What are the relative costs of different strategies and technologies?
- LK: I am a skeptic of solar. I did a thought experiment where Imeasured the efficiency of replacing incandescent bulbs with CFL bulbsand compared that to adding a solar PV system. I found that CFL’s were457 times more cost effective than solar PV without any rebates orincentives.
- LK: Our office also did a study comparing options. We found thatlighting retrofits pay back in 7-10 years, and the payback time isdramatically less if you just turn off the lights and don’t add motionsensors and dimmable controls.
- BG: Solar thermal has an equal if not better payback than solar PV,depending on natural gas prices. In 2006, the payback was 20 years.Today, that payback time is 40 years, double the time it took five years ago, because the cost of electricity from natural gas has cut in halfin the past five years.
- BG: There was a recent study in Kentucky showing that if all coalminers were forced to retire, paid their pensions in full, and there was a subsequent major investment in renewable energy, we would be muchbetter off economically [Editor: I tried locating this study withoutresults – please share if you know what study this refers to.]
- NK: McKinsey put together a greenhouse gas emissions cost curve. From a pure macroeconomic analysis, what we found was that energyefficiency is by far the most cost-effective strategy, which pays backvery quickly depending on the approach. Energy efficiency strategiesinclude increasing insulation, retrofitting lighting, improvingindustrial facilities, etc. Solar PV doesn’t even compare – it’s on theright side of the cost curve, meaning it doesn’t pay back.
- RP: Solar offers ten times the energy return on the embodied energyit takes to manufacture the panels. This efficiency will continue toimprove.
- RP: Agreed that efficiency strategies such as daylighting harvesting are the first things you should do. But solar is still necessarybecause daylighting is on the demand side – it doesn’t supply thebuilding with the energy it needs to operate.
Question #2: What should the government’s role be?
- [Editor: most pass on this question.]
- RP: Government should provide the long-term vision.
Question #3: What are the opportunities?
- BG: We expect a 15-20% growth in solar thermal in the next ten years and up to 25% if there is any positive movement from government ortechnology breakthroughs.
- BG: Solar thermal is an $800M industry; it’s much smaller than thesolar PV industry because the costs to manufacture solar thermal aresignificantly less.
- BG: China is taking the lead in renewable energy. 2005 was the first year in which the US imported more renewable energy products than itexported. This gives China a significant competitive advantage as theworld moves towards renewable energy. Europeans are also putting a stake in the ground, including many that are investing in the US because they see major market potential. Also, countries such as Germany are goingthrough painful transitions away from nuclear and towards renewableenergy over the next few decades, but this puts these leaders at asignificant competitive advantage similar to China’s.
- NK: Energy efficiency presents a $1B revenue opportunity at aninvestment of $520M. That’s a huge return on investment. Thiscalculation doesn’t even include technological breakthroughs orbehavioral change.
- RP: There is an order of magnitude more solar energy available thanall fossil fuels combined. NYC offers the densest solar PV potential onthe planet.
- RP: The solar PV industry has grown 50% a year over the past tenyears. The price of modules has steadily decreased and will continue todo so. Currently the cost is roughly $4/watt and will be $1/watt in tenyears.
- RP: The real benefit of solar PV is that it doesn’t just offsetfossil fuel needs; it’s a distributed power plant. [Editor: This onlymatter if you produce more electricity than you consumer, which isn’tthe case with the majority of homeowners.]
Question 4: What are the barriers?
- BG: First, for solar thermal, many of the systems are designed inEurope. Those systems won’t work in the US because we get 2-3 times thesunlight of Europe and the systems can’t handle that much excess heat.Second, most homes in the US used forced hot air for A/C. We cannotutilize solar thermal to offset the energy used in forced hot air. Thisisn’t a problem in Europe because most people have radiant coolingsystems.
- BG: The cost of natural gas is the other major barrier. With theincrease in shale natural gas and the decrease in cost by 50%, it’s more difficult to make the case for solar thermal.
- NK: Natural gas costs don’t impact energy efficiency strategiesmuch. [Editor: I wanted to hear him back up this statement. Presumably, if electricity costs less, than the ROI of energy efficiency strategies isn’t as great.]
- NK: The barriers to broad adoption of energy efficiency strategiesare many (displays slide). There are three categories: structural (e.g.fragmentation and lack of centralization), behavioral (e.g. most peoplearen’t thinking about their energy consumption), and availability (e.g.private banks aren’t willing to lend because they have a hard timecalculating the risks).
- RP: If you include societal benefits, the payback of solar PV isobvious. But most people look at the pure economic payback and thisdoesn’t include externalities such as societal benefits.
- RP: The incentives structure is too complex. We should do what they did in Spain and use feed-in-tariffs [Editor: This is very expensive for government, partially contributing to Spain’s current financial troubles.]
Question #5: Where would you put your money?
- LK: We look at solutions that are technology neutral, meaning weonly look at performance. We’re not in the business of providingincentives, but if we were, we would focus on reductions first.
- [Editor: each panelist agrees that efficiency is the first step,with BG advocating for solar thermal afterwards and RP advocating forsolar PV. NK doesn’t even talk about technology as there’s so muchopportunity with energy efficiency alone.]
- Random audience member: Nuclear is the largest energy subsidy in the US, followed closely by fossil fuels. In comparison, renewable energysubsidies make up a very small amount of US energy subsidies. I suggestwe get rid of all subsidies and show that renewable energy iscost-effective when you level the playing field.
What do you think? Where would/do you and/or your business put your investments? Is solar PV worth it? Why/why not?
All in all, the panelists were intelligent, provided sound reasoning, and on the same team. But there were some curious assertions, many ofwhich I questioned throughout the transcript. Beyond those points, I have come to several of my own conclusions:
- The biggest barrier to the feasibility of solar PV and otherstrategies and technologies is the cost of natural gas. I had theprivilege to attend the RBC Capital Markets “Global Energy and Power Conference” last week. It was staggering tohear the earnings and projections of the shale natural gas companies.Many are looking at 25% plus growth over the next few years. Withimprovements in horizontal drilling technology and few regulations (EPA is currently investigating hydraulic fracturing, but not until 2012 and then again in 2014), natural gas prices willcontinue to stay low for at least the next 2-3 years and likely forquite some time after that. In some ways, the most strategic leveragefor clean energy advocates is to raise the cost of natural gas. I’m notadvocating that necessarily; cheap energy can stimulate the economyduring a downturn. But I want to bring to light that for all thevariation amongst the speakers, and beyond that with people that support alternatives to fossil fuels, the common thread is a massive threatfrom low-cost shale natural gas costs. If nothing else, we should be paying more attention to the major activity across the US to discover and produce natural gas from shale. As Bill Guiney from Johnson Controls said, “Moneycontrols.”
- Richard Perez’s main argument about the benefit of solar PV is thatit is in essence a power station and not just a way to reduce yourbuilding’s fossil fuel energy consumption. I assume that the majority of buildings that use solar PV also use fossil fuel energy to supplyenergy that the solar PV isn’t able to. I’m having trouble findingresearch to supply my assertion (or Richard’s), so if you know ofanything, please let me know. But the simple fact that Richard’scalculations included societal benefits (which most entities don’tfactor in) and that the argument for the power-plant nature of solar PV(which the evidence for this position is lacking) leads me to believethat solar PV isn’t the most cost-effective strategy or technology toreduce US greenhouse gas emissions.
- The argument that the US is losing (has already lost?) it’sstrategic position as a renewable energy manufacturer has seriouseconomic implications. If we look at the concentrated wealth inoil-producing nations, we can get a glimpse of the benefits that marketleaders of renewable energy technologies will hold in the comingdecades. Read my article about fracking here.
- This morning I read an article in the Wall Street Journal on the top ten thriving industries in the US. Numbers 2, 4, and 7respectively are: wind power, environmental consulting, and solar power.
- It was also interesting that the speakers presented their data in terms of ROI, not IRR. Chris Williams wrote a great post on why this thinking is backwards.
- Finally, the only mention of behavioral change was that it is abarrier to broad adoption of energy efficiency measures. This lack ofattention to behavioral change was echoed in a panel I attended withSolar1 a few weeks ago on the “Value of a Negawatt” (post coming soon). This is not to say that other entities, such asentrepreneurs, aren’t paying attention to behavior change, but that many people looking at the necessary greenhouse gas emissions reductionsaren’t counting on people to make the right choices.
Rikki Suarez majors in Creative Writing and loves writing about renewable energy, clean technology, and solar power.