Notes regarding Solar Panels
Solar modules use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The structural (load carrying) member of a module can either be the top layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most solar modules are rigid, but semi-flexible ones are available, based on thin-film cells. These early solar modules were first used in space in 1958.
Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the modules may contain silver, copper or other non-magnetic conductive transition metals. The cells must be connected electrically to one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic modules use MC3 (older) or MC4 connectors to facilitate easy weatherproof connections to the rest of the system.
Bypass diodes may be incorporated or used externally, in case of partial module shading, to maximize the output of module sections still illuminated.
Some recent solar module designs include concentrators in which light is focused by lenses or mirrors onto an array of smaller cells. This enables the use of cells with a high cost per unit area (such as gallium arsenide) in a cost-effective way. Efficiencies See also: Solar cell efficiency
Depending on construction, photovoltaic modules can produce electricity from a range of frequencies of light, but usually cannot cover the entire solar range (specifically, ultraviolet, infrared and low or diffused light). Hence much of the incident sunlight energy is wasted by solar modules, and they can give far higher efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light into different wavelength ranges and direct the beams onto different cells tuned to those ranges. This has been projected to be capable of raising efficiency by 50%. Scientists from Spectrolab, a subsidiary of Boeing, have reported development of multijunction solar cells with an efficiency of more than 40%, a new world record for solar photovoltaic cells. The Spectrolab scientists also predict 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.
Currently the best achieved sunlight conversion rate (solar module efficiency) is around 21.5% in new commercial products typically lower than the efficiencies of their cells in isolation. The most efficient mass-produced solar modules[disputed discuss] have power density values of up to 175 W/m2 (16.22 W/ft2). Research by Imperial College, London has shown 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 previously (aluminum was preceded by gold and silver), the light scattering 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. This, the research argued, could bring down the cost significantly and improve the efficiency as aluminum is more abundant and less costly than gold and silver. 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".
Efficiencies of solar panel can be calculated by MPP(Maximum power point) value of solar panels Solar inverters convert the DC power to AC power by performing MPPT process: solar inverter samples the output Power(I-V curve) from the solar cell and applies the proper resistance (load) to solar cells to obtain maximum power.
MPP(Maximum power point) of the solar panel consists of MPP voltage(V mpp) and MPP current(I mpp): 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 known as the "Christmas light effect"). Micro-inverters work independently so each panel contributes its maximum possible output given the available sunlight.
Crystalline silicon modules Main article: Crystalline silicon
Most solar modules are currently produced from solar cells made of polycrystalline and monocrystalline silicon. In 2013, crystalline silicon accounted for more than 90 percent of worldwide PV production. Thin-film modules
Main articles: Thin film solar cell and Third generation solar cell
Third generation solar cells are advanced thin-film cells. They produce a relatively high-efficiency conversion for the low cost compared to other solar technologies.
Rigid thin-film modules
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 superstrate, and the electrical connections are created in situ, a so-called "monolithic integration". The substrate or superstrate 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, or a-Si, or a-Si+uc-Si tandem, or CIGS (or variant). Amorphous silicon has a sunlight conversion rate of 6-12%.
Flexible thin-film modules
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 (e.g. polyester or polyimide film) then monolithic integration can be used.
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 colourless fluoropolymer on the front side (typically ETFE or FEP) and a polymer suitable for bonding to the final substrate on the other side. The only commercially available (in MW quantities) flexible module uses amorphous silicon triple junction (from Unisolar).
So-called inverted metamorphic (IMM) multijunction solar cells made on compound-semiconductor technology are just becoming commercialized in July 2008. The University of Michigan's solar car that won the North American Solar Challenge in July 2008 used IMM thin-film flexible solar cells.
The requirements for residential and commercial are different in that the residential needs are simple and can be packaged so that as solar cell technology progresses, the other base line equipment such as the battery, inverter and voltage sensing transfer switch still need to be compacted and unitized for residential use. Commercial use, depending on the size of the service will be limited in the photovoltaic cell arena, and more complex parabolic reflectors and solar concentrators are becoming the dominant technology.
Flexible thin-film panels are optimal for portable applications as they are much more resistant to breakage than regular crystalline cells, but can be broken by bending them into a sharp angle. They are also much lighter per square foot than standard rigid solar panels.
The global flexible and thin-film photovoltaic (PV) market, despite caution in the overall PV industry, is expected to experience a CAGR of over 35% to 2019, surpassing 32 GW according to a major new study by IntertechPira.
Smart solar modules
Main articles: Smart module and Solar micro-inverter
Several companies have begun embedding electronics into PV modules. This enables performing maximum power point tracking (MPPT) for each module individually, and the measurement of performance data for monitoring and fault detection at module level. Some of these solutions make use of power optimizers, a DC-to-DC converter technology developed to maximize the power harvest from solar photovoltaic systems. As of about 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.
Newer Technology Coming
"Graphene, the well-publicised and now famous two-dimensional carbon allotrope, is as versatile a material as any discovered on Earth. Its amazing properties as the lightest and strongest material, compared with its ability to conduct heat and electricity better than anything else, mean that it can be integrated into a huge number of applications. Initially this will mean that graphene is used to help improve the performance and efficiency of current materials and substances, but in the future it will also be developed in conjunction with other two-dimensional (2D) crystals to create some even more amazing compounds to suit an even wider range of applications. To understand the potential applications of graphene, you must first gain an understanding of the basic properties of the material."
"Offering very low levels of light absorption (at around 2.7% of white light) whilst also offering high electron mobility means that graphene can be used as an alternative to silicon or ITO in the manufacture of photovoltaic cells. Silicon is currently widely used in the production of photovoltaic cells, but while silicon cells are very expensive to produce, graphene based cells are potentially much less so. When materials such as silicon turn light into electricity it produces a photon for every electron produced, meaning that a lot of potential energy is lost as heat. Recently published research has proved that when graphene absorbs a photon, it actually generates multiple electrons. Also, while silicon is able to generate electricity from certain wavelength bands of light, graphene is able to work on all wavelengths, meaning that graphene has the potential to be as efficient as, if not more efficient than silicon, ITO or (also widely used) gallium arsenide. Being flexible and thin means that graphene based photovoltaic cells could be used in clothing; to help recharge your mobile phone, or even used as retro-fitted photovoltaic window screens or curtains to help power your home."
"One area of research that is being very highly studied is energy storage. While all areas of electronics have been advancing over a very fast rate over the last few decades (in reference to Moore's law which states that the number of transistors used in electronic circuitry will double every 2 years), the problem has always been storing the energy in batteries and capacitors when it is not being used. These energy storage solutions have been developing at a much slower rate. The problem is this: a battery can potentially hold a lot of energy, but it can take a long time to charge, a capacitor, on the other hand, can be charged very quickly, but can't hold that much energy (comparatively speaking). The solution is to develop energy storage components such as either a supercapacitor or a battery that is able to provide both of these positive characteristics without compromise."
"Currently, scientists are working on enhancing the capabilities of lithium ion batteries (by incorporating graphene as an anode) to offer much higher storage capacities with much better longevity and charge rate. Also, graphene is being studied and developed to be used in the manufacture of supercapacitors which are able to be charged very quickly, yet also be able to store a large amount of electricity. Graphene based micro-supercapacitors will likely be developed for use in low energy applications such as smart phones and portable computing devices and could potentially be commercially available within the next 5-10 years. Graphene-enhanced lithium ion batteries could be used in much higher energy usage applications such as electrically powered vehicles, or they can be used as lithium ion batteries are now, in smartphones, laptops and tablet PCs but at significantly lower levels of size and weight." source http://www.graphenea.com/pages/graphene-uses-applications#.VkX0ZV6qnGh
The properties of graphene, carbon sheets that are only one atom thick, have caused researchers and companies to consider using this material in several fields. More efficient dye sensitized solar cells. Researchers at Michigan Technological University have developed a honeycomb like structure of graphene in which the graphene sheets are held apart by lithium carbonate. They have used this "3D graphene" to replace the platinum in a dye sensitized solar cell and achieved 7.8 percent conversion of sunlight to electricity.
Lower cost solar cells: Researchers have built a solar cell that uses graphene as a electrode while using buckyballs and carbon nanotubes to absorb light and generate electrons; making a solar cell composed only of carbon. The intention is to eliminate the need for higher cost materials, and complicated manufacturing techniques needed for conventional solar cells.
Module performance is generally rated under standard test conditions (STC): irradiance of 1,000 W/msq, solar spectrum of AM 1.5 and module temperature at 25 degree C.
The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter. The total amount of energy received at ground level from the sun at the zenith depends on the distance to the sun and thus on the time of year. It is about 3.3% higher than average in January and 3.3% lower in July (see below). If the extraterrestrial solar radiation is 1367 watts per square meter (the value when the earth-sun distance is 1 astronomical unit), then the direct sunlight at the earth's surface when the sun is at the zenithis about 1050 W/m2, but the total amount (direct and indirect from the atmosphere) hitting the ground is around 1120 W/m2. In terms of energy, sunlight at the earth's surface is around 52 to 55 percent infrared (above 700 nm), 42 to 43 percent visible (400 to 700 nm), and 3 to 5 percent ultraviolet (below 400 nm). At the top of the atmosphere, sunlight is about 30% more intense, having about 8% ultraviolet (UV), with most of the extra UV consisting of biologically damaging short-wave ultraviolet.
Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, higher than most artificial lighting, including fluorescent. Multiplying the figure of 1050 watts per square metre by 93 lumens per watt indicates that bright sunlight provides an illuminance of approximately 98 000 lux (lumens per square meter) on a perpendicular surface at sea level. The illumination of a horizontal surface will be considerably less than this if the sun is not very high in the sky. Averaged over a day, the highest amount of sunlight on a horizontal surface occurs in January at the South Pole (see insolation).
Looks to me as 42% of 1120 W/m2 =470.4 W/m2 1 square meter= 10.76391 square ft 1ft squared= 0.09290304 square meter 2496 sq inches 2496 Square Inches = 17.333333333333332 Square Feet 1640 mm*990 mm = 1623600 sq mm = 1.623600 square meters 1.6*2 = 3.2
Electrical characteristics 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. The actual voltage output of the module changes as lighting, temperature and load conditions change, so there is never one specific voltage at which the module operates. Nominal voltage allows users, at a glance, to make sure the module is compatible with a given system.
Open circuit voltage or VOC is the maximum voltage that the module can produce when not connected to an electrical circuit or system. VOC can be measured with a meter directly on an illuminated module's terminals or on its disconnected cable.
The peak power rating, Wp, is the maximum output under standard test conditions (not the maximum possible output). Typical modules, which could measure approximately 1x2 meters or 2x4 feet, will be rated from as low as 75 watts to as high as 350 watts, depending on their efficiency. At the time of testing, the test modules are binned according to their test results, and a typical manufacturer might rate their modules in 5 watt increments, and either rate them at +/- 3%, +/-5%, +3/-0% or +5/-0%.
Solar modules must withstand rain, hail, heavy snow load, and cycles of heat and cold for many years. Many crystalline silicon module manufacturers offer a warranty that guarantees electrical production for 10 years at 90% of rated power output and 25 years at 80%.
PRODUCT OVERVIEW Model # GS-S-265-Fab1x2 Internet # 205481288 The Grape Solar 265-Watt 2 piece savings pack bundles 2 Grape Solar GS-S-265-Fab1 panels together for even greater savings. The Grape Solar 265-Watt Mono-crystalline Solar Panel uses high efficiency solar cells (approximately 19%) made from quality silicon material for high module conversion efficiency, long term output stability, and reliability. Virtually maintenance free. High transmittance, low iron tempered glass for durability and enhanced impact resistance.
2 piece Grape Solar GS-S-265-Fab5 panels bundled together for even greater savings Positive power output tolerance of 0% to +3%
Outstanding electrical performance under high temperature and weak light environments Can withstand snow and wind loads greater than 50 lbs. per 2 ft.
Unique frame design for easy installation Rigorous quality control to meet the highest international standards Positive and negative leads equipped with MC4 connectors
When charging 12-Volt battery systems with this panel, an MPPT charge controller must be used
Dimensions Panel Height (in.) 1.6 Product Depth (in.) 67
Panel Width (in.) 39 Product Height (in.) 12
Panel length (in.) 64.6 Product Width (in.) 42
Amperage (amps) 8.5 Panel weight (lb.) 44
Charge controller included No Portable No
Electrical Product Type Solar Power Panel Returnable 90-Day
Inverter included No Solar panel type Monocrystalline silicon panel
Low voltage audible alarm No Voltage (volts) 31.2
Mounting frame included No Wattage (watts) 265
Number of Panels 2
Warranty / Certifications
Manufacturer Warranty 10 year limited product warranty on materials and workmanship. 25 year warranty on >80% power output and 10 year warranty on >90% power output.
High efficiency solar cells (approx. 18%) with quality silicon material for high module conversion efficiency and long term output stability and reliability.
Positive power output tolerance from 0% to +3%.
Rigorous quality control to meet the highest international standards.
High transmittance, low iron tempered glass with enhanced stiffness and impact resistance.
Unique frame design with strong mechanical strength for greater than 50 lbs/ft2 wind load and snow load withstanding and easy installation.
Advanced encapsulation material with multilayer sheet lamination to provide long-life and enhanced cell performance.
Outstanding electrical performance under high temperature and weak light environments. CERTIFICATIONS ISO 9000:2000 CE
Cell Size 156mm x 156mm (6.14 inches x 6.14 inches)
Module Dimension (LxWxT) 1640mm x 982mm x 40mm (64.6 inches x 38.7 inches x 1.6 inches)
No. of Cells 6 x 10 = 60
Weight 19.4 kg (42.8 lbs)
Cable Length 900mm (43.3 inch) for positive (+) and negative (-)
Typed of Connector MC-IV Junction Box IP65 or IP67 Rated
No. of Holes in Frame 4 draining holes, 8 installation holes, 2 grounding holes, 16 air outlet holes
Electrical Specifications (STC* = 25 degree C, 1000W/m2 Irradiance and AM=1.5)
Characteristic Details Max System Voltage 1000V / 600V
Max Peak Power Pmax 260 W (-2%, +2%)
CEC PTC Listed Power 231.6 W
Maximum Power Point Voltage Vmpp 31.6 V
Maximum Power Point Current Impp 8.23 A
Open Circuit Voltage Voc 37.9 V
Short Circuit Current Isc 8.67 A
Module Efficiency (%) 16%
Temperature Coefficient of Voc -0.128 V/degree C (-0.34% /degree C)
Temperature Coefficient of Isc 3.63x10-3 A/degree C (0.04% /degree C)
Temperature Coefficient of Pmax -1.25 W/degree C (-0.48% /degree C)
Other Performance Data
Power Tolerance Operating Temperature Max Series Fuse Rating NOCT*
-2% / +2% -40 degrees C to +85 degrees C 15 A 45 degrees C +-2 degrees C *Normal Operating Cell Temperature
Solar panels generate the most electricity on clear days with abundant sunshine (not surprisingly). But, do solar panels work in cloudy weather? Yes just not quite as well On a cloudy day, typical solar panels can produce 10-25% of their rated capacity. The exact amount will vary depending on the density of the clouds, and may also vary by the type of solar panel; some kinds of panels are better at receiving diffuse light. SunPower solar cells, for example, have been designed to capture a broader range of the solar spectrum. By capturing more red and blue wavelengths, their solar panels can generate more electricity even when it's overcast.
Ultraviolet light also reaches the earth's surface in abundance during cloudy days (if you've ever been at the beach when it's cloudy and gotten a sunburn, you've experienced this firsthand). Some solar cells are in development that can capture UV rays, although these are not out on the market yet. Even with a standard solar panel on a cloudy day, though, you will be able to generate some power when it's daylight. The same thing is true in foggy weather. If you live in a city with frequent fog, like San Francisco, you'll still be able to generate electricity when the fog rolls in.
A silver lining to that cloud: how the 'edge of cloud' effect can produce more solar power than a sunny day
If you have solar panels and keep a close watch on your power output, you may have noticed a strange phenomenon: on a partly cloudy day, it's possible to exceed your solar system's power rating and produce more power that you could on a sunny day. Known as the "edge of cloud" effect, this happens when the sun passes over the outer edge of a cloud, magnifying the sunlight. The intense light causes your solar system to boost power output temporarily, which can help balance out losses from full cloud cover.
Monocrystalline Polycrystalline Amorphous CdTe CIS/CIGS
Typical module efficiency 15-20% 13-16% 6-8% 9-11% 10-12%
Best research cell efficiency 25.0% 20.4% 13.4% 18.7% 20.4%
Area required for 1 kWp 6-9 m2 8-9 m2 13-20 m2 11-13 m2 9-11 m2
Typical length of warranty 25 years 25 years 10-25 years
Lowest price 0.75 $/W 0.62 $/W 0.69 $/W
Temperature resistance Performance drops 10-15% at high temperatures
Less temperature resistant than
monocrystalline Tolerates extreme heat Relatively low impact on performance
Oldest cell technology and most widely used Less silicon waste in the production process
Tend to degrade faster than crystalline-based solar panels
Low availability on the market
Lowest price is based on listings of wholesalers and retailers on the Internet (June 3, 2013).
Best research cell efficiency is data collected from National Renewable Energy Laboratory (NREL).
Photovoltaic & Amorphous Solar Cells
Solar cells are made out of N-type and P-type semiconductor material that use the visual light spectrum to generate electricity. Solar radiation with wavelengths of 380 nm to 750 nm (violet to red) strike the material with enough energy to knock electrons from their weak bonds and create an electric current. The unused wavelengths (ultraviolet & infrared) do not have enough energy to dislodge the electrons and are absorbed as heat.
Multi-layer Amorphous Solar Panels
Thin layers of amorphous semiconductor can be applied on top of one another. Each layer is specifically doped to take advantage of a certain wavelength. Light will travel through each layer until it strikes the appropriate layer where it frees one electron and makes an electric current. This stack-up makes use of all of the various wavelengths and holds promise to creating more efficient solar panels.
Full-Spectrum Photovoltaic Material
With existing solar cells, the unused ultraviolet and infrared wavelengths are not converted into electricity but rather wasted as heat. A recent discovery of a new semiconductor material made from indium, gallium and nitrogen can convert virtually the full spectrum of sunlight - from the far ultraviolet to the near infrared - into electricity. One panel can use the entire electromagnetic spectrum and holds promise of being the most efficient solar panel ever created.
A newly established low band gap for indium nitride means that the indium gallium nitride system of alloys (In1-xGaxN) covers the full solar spectrum.
Many factors limit the efficiency of photovoltaic cells. Silicon is cheap, for example, but in converting light to electricity it wastes most of the energy as heat. The most efficient semiconductors in solar cells are alloys made from elements from group III of the periodic table, like aluminum, gallium, and indium, with elements from group V, like nitrogen and arsenic.
One of the most fundamental limitations on solar cell efficiency is the band gap of the semiconductor from which the cell is made. In a photovoltaic cell, negatively doped (n-type) material, with extra electrons in its otherwise empty conduction band, makes a junction with positively doped (p-type) material, with extra holes in the band otherwise filled with valence electrons. Incoming photons of the right energy -- that is, the right color of light -- knock electrons loose and leave holes; both migrate in the junction's electric field to form a current.
Photons with less energy than the band gap slip right through. For example, red light photons are not absorbed by high-band-gap semiconductors. While photons with energy higher than the band gap are absorbed -- for example, blue light photons in a low-band gap semiconductor -- their excess energy is wasted as heat.
The maximum efficiency a solar cell made from a single material can achieve in converting light to electrical power is about 30 percent; the best efficiency actually achieved is about 25 percent. To do better, researchers and manufacturers stack different band gap materials in multijunction cells. Dozens of different layers could be stacked to catch photons at all energies, reaching efficiencies better than 70 percent, but too many problems intervene. When crystal lattices differ too much, for example, strain damages the crystals. The most efficient multijunction solar cell yet made -- 30 percent, out of a possible 50 percent efficiency -- has just two layers.
At first glance, indium gallium nitride is not an obvious choice for solar cells. Its crystals are riddled with defects, hundreds of millions or even tens of billions per square centimeter. Ordinarily, defects ruin the optical properties of a semiconductor, trapping charge carriers and dissipating their energy as heat.
In studying LEDs, however, the Berkeley Lab researchers found that the way indium joins with gallium in the alloy leaves indium-rich concentrations that, remarkably, emit light efficiently. Such defect-tolerance in LEDs holds out hope for similar performance in solar cells.
To exploit the alloy's near-perfect correspondence to the spectrum of sunlight will require a multijunction cell with layers of different composition. Walukiewicz explains that "lattice matching is normally a killer" in multijunction cells, "but not here. These materials can accommodate very large lattice mismatches without any significant effect on their optoelectronic properties."
Two layers of indium gallium nitride, one tuned to a band gap of 1.7 eV and the other to 1.1 eV, could attain the theoretical 50 percent maximum efficiency for a two-layer multijunction cell. (Currently, no materials with these band gaps can be grown together.) Or a great many layers with only small differences in their band gaps could be stacked to approach the maximum theoretical efficiency of better than 70 percent.
It remains to be seen if a p-type version of indium gallium nitride suitable for solar cells can be made. Here too success with LEDs made of the same alloy gives hope. A number of other parameters also remain to be settled, like how far charge carriers can travel in the material before being reabsorbed.
Indium gallium nitride's advantages are many. It has tremendous heat capacity and, like other group III nitrides, is extremely resist to radiation. These properties are ideal for the solar arrays that power communications satellites and other spacecraft. But what about cost?
"If it works, the cost should be on the same order of magnitude as traffic lights," Walukiewicz says. "Maybe less." Solar cells so efficient and so relatively cheap could revolutionize the use of solar power not just in space but on Earth.
New technology will enable graphens which is 1 atom thick carbon to be used to form colar cells that can absorb all wavelengths of light.
Amorphous Silicon Solar Panels
Last updated June 26, 2013 by Mathias Aarre Maehlum
Amorphous silicon (a-Si or a-Si:H) solar cells belong to the category of silicon thin-film, where one or several layers of photovoltaic material are deposited onto a substrate.
Some types of thin-film solar cells have a huge potential. These technologies are expected to grow rapidly in the coming years as they mature. In 2011, amorphous silicon solar cells represented about 3% of market.
The word amorphous literally means shapeless. The silicon material is not structured or crystalized on a molecular level, as many other types of silicon-based solar cells are.
Most pocket calculators are powered by thin film solar cell made out of amorphous silicon. For a long time, the low power output of amorphous silicon solar cells limited their use to small applications only.
This problem is partially solved by stacking several amorphous solar cells on top of each other, which increases their performance and makes them more space-efficient.
In laboratory conditions, scientists have pushed efficiency rates to 12.5%. The efficiency of amorphous silicon solar cells that are manufactured in high-volume processes ranges from 6% to 9%. Oerelikon set the world record for stable amorphous solar cells to above 10% in 2009.
42 degrees N lattitude 83 W 42 28 23 83 1 15 if it produces 220 84.2 hours = 924
3. Divide the number of watts of power you use each day by the average hours of sunlight per day. This will be the number of watts you need to produce per hour. Continuing the example, suppose that you get about three full hours of sun per day. 10,904 watts / 3 hours = 3,635 watts / hour. Computer 100 + lights 50 = 150 *16 hrs = 2400/4.2 = 571 4. Divide the watts you need to produce per hour by the rating of the panels you want to purchase and round up. This will tell you how many panels to use. Different panels will have different watt ratings, so you have choices about which ones to purchase. For the example, if 500-watt panels were being purchased, you would need 3,635 / 500 = 8 panels.
571/220 = 2.5 When connecting panels, you can do either of the following:
Increase the Voltage, by connecting panels with the same AMPS, in series or Increase the Amps, by connecting panels with the same Vmax in PARALLEL.
Series: 18V, 3A & 17V, 3A & 26V, 3A = 61V @ 3A
Parallel: 18V, 3A & 18V, 20A & 18V, .6a = 18V @ 23.6A
-end example- Begin truism :
A series string is limited by the lowest amp panel, and the voltages all add together
A parallel string is limited to the lowest voltage panel, and the amps add together.
Schottky diodes are best for direct charging batteries, to keep the battery from backfeeding the array at night, and draining the batteries.
The are two different types of diodes which may have an important role in the functioning of solar panels (actually the diodes themselves may be identical, it is the way in which they are used which has two possibilities). First let's confirm what a diode is and what it does -
What is a Diode
A diode uses a semiconductor material, usually silicon, with two terminals attached. It's function in it's simplest form is to allow electricity to pass in one direction but not the other.
schematic diagram of simple circuit with a blocking diode
The diagram to the right shows a simple setup with two panels charging a battery (for simplicity no controller is shown) with a blocking diode in series with the two panels, which are also wired in series. When the sun shines, as long as the voltage produced by the two panels is greater than that of the battery, charging will take place.
However, in the dark, when no voltage is being produced by the panels, the voltage of the battery would cause a current to flow in the opposite direction through the panels, discharging the battery, if it was not for the blocking diode in the circuit.
Blocking diodes will be of benefit in any system using solar panels to charge a battery. Blocking diodes are usually included in the construction of solar panels so further blocking diodes are not required.
Now let's consider what happens if one of the panels in the above diagram is shaded. Not only will that panel not be producing any significant power, but it will also have a high resistance, blocking the flow of power produced by the unshaded panel.
schematic diagram of a simple circuit with blocking and by-pass diodes
This is where by-pass diodes come into play as shown in the diagram to the right. Now, if one panel is shaded, the current produced by the unshaded panel can flow through a by-pass diode to avoid the high resistance of the shaded panel.
By-pass diodes will not be of use unless panels are connected in series to produce a higher voltage. They are most likely to be of benefit where an MPPT Controller or String Inverter involves panels connected in series to produce voltages well above that items minimum input voltage.
Some solar panels are constructed with the cells divided into groups, each group having a built-in by-pass diode.
Shading of part of a panel may be caused by a tree branch, debris, or snow.
Renogy states that its 100W Mono Solar Panel that its High module conversion efficiency (approx. 15.46%) of every Renogy 100-Watt Mono solar panel. Has Ideal output: 500 watt hours per day. Can fully charge a 50Ah battery from 50% in 3 hours (depends on sunlight availability).
New to solar? This Starter Kit is the perfect kit for someone who wants to begin utilizing solar energy for their off-grid adventures.
Renogy 100 Watt Monocrystalline Solar Panel, 30 amp PWM Charge Controller, 20 ft. MC4 Adaptor Kit, and a set of Z-brackets are all included in this specialized kit.
This kit is the perfect introduction to solar!
Renogy 100W Monocrystalline Solar Panel
Maximum Power: 100W
Optimum Operating Voltage (Vmp): 18.9V
Optimum Operating Current (Imp): 5.29A
Renogy 30A PWM Charge Controller
Rated Charge Current: 30A
Max. Solar Input Voltage: 42V
Max. PV Input Power: 360W (12V), 720W (24V)
Renogy 20Ft MC4 Adaptor Kit
Rating Voltage: 600/1000V
Mounting Z Brackets, 4 Z Shape Solar Panel Brackets, 8 Long Cap Bolts and 4 Short Bolts, 4 Spring Washers and 4 Washers, 4 Nuts
Product Dimensions: 47 x 1.5 x 20.9 inches ; 19.8 pounds Shipping Weight: 25.4 pounds
How many amps are charging the battery while inuse, on a sunny day ?
I purchased this system to act as a 'test bed' prior to buying my main dual-axis 2 panel system (Two 250W, 24V 8A panels). It's a monocrystilline 100w panel stated to output 5 amps, 12volts. I see consistent 13~14 volts at 4 amps, and have hit 5 amps on really good days (but 4A are more realistic). As a test item, I had it charging a 73AH Deep Cycle Gel battery from West Marine (the panel came with a 30A PWM charge controller). It worked fine and charged the battery in a matter of short hours ( I have both an amp meter and a volt meter connected to track its output). Previously, I was using two 45W amorphous panels (Harbor Freight) that took up to 4 days to do what this one panel can do in 4 hours. Buy with confidence
Do you have to ground this system (solar panel, controller or battery)?
yes you really should ground the system otherwise you will have a floating neutral situation which is not very good for most power sensitive appliances etc.
How do you hook more two batteries together? In parallel, I assume? And this would double the battery usage time, correct?
The batteries may be wired together in either parallel or series configurations - depends on your needs. Parallel wiring = increased amp/hr rating at same voltage
Series wiring = increased voltage at same amp/hr rating
David Dean answered on January 6, 2014
In parallel you double the amps, in series you double the voltage
Michael L. answered on January 7, 2014
You need to make sure of a couple things. #1 the Batteries ideally need to be bought at the same time as a pair. #2 at a minimum the batteries need to be the same class (capacity) and close to the same age. Otherwise you will not have even charging, one battery will charge fully, and actually discharge itself to bring the other battery up to its level of charge.
You must use deep cycle batteries. Standard car batteries are not designed to have a constant drain down and recharge like deep cycle's are.
A little advise....Do not waste your$$ on marine deep cycle batteries. They are made very cheaply now days and will not give much longevity. Spend a little more if you want to run a 12 volt or 24 volt set up and use 6v "flooded golf cart batteries" in the correct hook up for your voltage preference. They are built very strong to have a longer life, way thicker more durable lead plates and will have much more reserve to use.
All you have to do is pick up a 12 marine battery and then pick up one 6 v cart battery. SURPRISE!! The weight difference will be very clear.
You may get a year if your lucky with a marine battery but cart batteries are made to last the punishing rigors of discharge/charge for years. Costco or Sams have great deals on cart batteries and Trojan manufactures some of the best around.
sealed and gel cells are less of a choice in solar. always go with "flooded" type for best results as you can exactly determine if your battery is FULLY charged use a old school hydrometer ( very inexpensive). It is the only true way to determine if your battery has a full charge to its rated capacity.
That's what I've done. I don't know that it "doubles" the usage time but certainly extends it. I also periodically use a battery charger to "boost" the batteries.
TJ answered on January 6, 2014
Yes I have 4 hooked up. Just connect all the positives and all the grounds to the battery u connect to
The total output per day of a solar power system depends on the size of that system and the amount of direct sunlight it receives. A 4-kilowatt (kW) system will produce 4 kW of solar power under direct sunlight. That same system, under an average five hours of sunlight per day, will produce 20 kilowatt-hours of solar energy each day and 7,300 kWh per year.
However, calculating actual system output is usually not so simple. A number of factors affect output, including wiring losses, shading, inverter efficiency, orientation to the sun and the fact that photovoltaic panels deliver an average of 95% of the power rating given by the manufacturer. According to Solar-Estimate.org, total losses from inefficiencies (assuming an unshaded, clean array) are 22%, meaning that 78% of the solar system's rated power is actually delivered to the source, your home.
Therefore, that 4-kW system described above, creating 20 kWh of energy per day, would actually deliver 15.6 kWh of solar energy each day (5,694 kWh per year). That is 468 kWh per month, about half of what the average American home consumes. However, a well-sealed, insulated, energy-efficient and energy-conserving home can use much less and realize much more effect from its solar power system.
1. If a 100 watt light bulb is left on for one hour, it will consume 100 watt-hours of energy. Left on for 10 hours, it will consume 1000 watt-hours, which is the same as 1 kilowatt-hour, or 1 kWh. Similarly (and under ideal conditions), if a 345 watt solar panel is left in the brightest sun for 1 hour, it will generate 345 watt-hours of energy. Under those same ideal conditions, after three hours, it will generate a little over 1 kWh.
The size of a solar system is specified in watts, or kilowatts (kW) or megawatts (MW). For example, a commonly seen residential rooftop solar system might be 4kW, a large solar power plant in the California desert can be well over 100 MW. The output of a solar system is given in kilowatt-hours (kWh) or megawatt-hours (MWh) or gigawatt-hours (GWh). Only the W is supposed to be capitalized but few people care and all variations are used interchangeably. Your electricity bill is priced in cents per kWh.
So how do you estimate kWh's from kW's? Here is just one way to do it:
Step 1 is to start with the maximum power your system can generate, and then de-rate it for each less than ideal factor. For example, dust may build up on the panels, blocking some of the light. Also, the direct current (DC) that the panels produce must be inverted into alternating current (AC) that homes and the power grid use, and there is some loss in the process. There are other factors that every solar installer understands, and there are standard tools to do the calculations. The result is that the maximum AC power that a rooftop solar system will generate is typically between 75% and 80% of the maximum DC (nameplate) power that's stamped on the panels by the manufacturer. For example, if you purchased a 4.14 kW system (that would be 4.14 kW DC, comprised of 12 345-watt DC panels), it would generate at its maximum between about 3.1 kW and 3. 3 kW AC. Let's go with 3.1 kW AC.
Step 2 is to calculate how much energy the system will generate on an average 24-hour day. At noontime on the brightest summer day, the system will put out 3.1 kW. Over the noontime hour on that bright day, it will generate 3.1 kWh. An average day means taking the average of a full year's worth of 365 days to account for seasonal changes. This would be a hard calculation involving morning fog, nighttime, rain, the sun's varying angle, but the National Renewable Energy Laboratory (NREL) has made it easy for everyone, by giving us the peak sun hours for a large number of locations across the country. Peak sun hours describes, given your system's maximum power (3.1 kW AC), how much energy that system will generate on the average day. The San Francisco Bay Area's number is about 5.5, meaning for a 3.1 kW AC system, 3.1 times 5.5 or about 17 kWh will be generated during the average day. Because the 5.5 is based on the full year's worth of 24-hour days, the yearly output of the 3.1 kW AC system is simply 365 times 17 kWh or 6205 kWh.
Now we can figure out how much energy (kWh) will be generated per square foot of solar panel. The 3.1 kW AC system is a 4.14 kW DC system made up of 12 345-watt panels, where each panel is about 17.3 sq feet. So 12 panels would be about 207 square feetand if that 207 square feet of panels generates 6205 kWh per year, then one square foot of solar panel generates about 30 kWh per year (6205 divided by 207 = 30).
Renogy 100 Watts 12 Volts Monocrystalline Solar Panel is Renogy's most popular product! High in power but sleek in size, this monocrystalline solar panel is the perfect item for off-grid application. Use it for your RV when camping or beach trips with the family, either way the 100 Watts 12 Volts monocrystalline solar panel will give you the most efficiency per space. With a set of MC4 connectors coming from the panel, connection with other Renogy panels is a breeze. If off-grid solar interests you then start with Renogy today! If you have any questions regarding this product, please leave us a message or give us a call at 1 (800) 330-8678 or (909) 287-7100. For Installation Guide, check us on YouTube
Key Features Reliability EL tested solar modules; no hot-spot heating guaranteed. Advanced encapsulation material with multilayered sheet laminations to enhance cell performance and provide a long service life. Corrosion-resistant aluminum frame for extended outdoor use, allowing the panels to last for decades as well as withstand high winds (2400Pa) and snow loads (5400Pa). Anti-reflective, high transparency, low iron-tempered glass with enhanced stiffness and impact resistance. The attached junction box is rated IP65 (complete protection against environmental particles and low pressure water jets). TPT back sheet ensures smooth performance over a long period of time. Efficiency High module conversion efficiency. Ideal output: 500Wh per day (depending on the availability of sunlight). Bypass diode minimizes power drop caused by shade and ensures excellent performance in low-light environments. Easy Installation Pre-drilled holes on the back of the panel for fast mounting and securing. A pair of 28in cables with MC4 connectors comes included with the panel.
Off-Grid Rooftop/Ground Mounted Residential/Rural RVs, trailers, motorhomes, caravans, etc. 12V Battery Charging
25-year transferable power output warranty: 5-year/95% efficiency rate, 10-year/90% efficiency rate, 25-year/80% efficiency rate 5-year material and workmanship warranty
This system 100w will provide approximately 300-Watt Hours or 25-Amp Hours of charge per day. Everything you Need to Know About the Basics of Solar Charge Controllers
What is a Solar Charge Controller?
Why do I need one?
A charge controller, or charge regulator is basically a voltage and/or current regulator to keep batteries from overcharging. It regulates the voltage and current coming from the solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no regulation the batteries will be damaged from overcharging. Most batteries need around 14 to 14.5 volts to get fully charged.
Do I always need a charge controller?
Not always, but usually. Generally, there is no need for a charge controller with the small maintenance, or trickle charge panels, such as the 1 to 5 watt panels. A rough rule is that if the panel puts out about 2 watts or less for each 50 battery amp-hours, then you don't need one.
For example, a standard flooded golf car battery is around 210 amp-hours. So to keep up a series pair of them (12 volts) just for maintenance or storage, you would want a panel that is around 4.2 watts. The popular 5 watt panels are close enough, and will not need a controller. If you are maintaining AGM deep cycle batteries, such as the Concorde Sun Xtender then you can use a smaller 2 to 2 watt panel.
Why 12 Volt Panels are 17 Volts
The obvious question then comes up - "why aren't panels just made to put out 12 volts". The reason is that if you do that, the panels will provide power only when cool, under perfect conditions, and full sun. This is not something you can count on in most places. The panels need to provide some extra voltage so that when the sun is low in the sky, or you have heavy haze, cloud cover, or high temperatures*, you still get some output from the panel. A fully charged "12 volt" battery is around 12.7 volts at rest (around 13.6 to 14.4 under charge), so the panel has to put out at least that much under worst case conditions.
*Contrary to intuition, solar panels work best at cooler temperatures. Roughly, a panel rated at 100 watts at room temperature will be an 83 watt panel at 110 degrees.
Detailed information on MPPT charge controllers.
The charge controller regulates this 16 to 20 volts output of the panel down to what the battery needs at the time. This voltage will vary from about 10.5 to 14.6, depending on the state of charge of the battery, the type of battery, in what mode the controller is in, and temperature. (see complete info on battery voltages in our battery section).
Using High Voltage (grid tie) Panels With Batteries
Nearly all PV panels rated over 140 watts are NOT standard 12 volt panels, and cannot (or at least should not) be used with standard charge controllers. Voltages on grid tie panels varies quite a bit, usually from 21 to 60 volts or so. Some are standard 24 volt panels, but most are not.
What happens when you use a standard controller
Standard (that is, all but the MPPT types), will often work with high voltage panels if the maximum input voltage of the charge controller is not exceeded. However, you will lose a lot of power - from 20 to 60% of what your panel is rated at. Charge controls take the output of the panels and feed current to the battery until the battery is fully charged, usually around 13.6 to 14.4 volts. A panel can only put out so many amps, so while the voltage is reduced from say, 33 volts to 13.6 volts, the amps from the panel cannot go higher than the rated amps - so with a 175 watt panel rated at 23 volts/7.6 amps, you will only get 7.6 amps @ 12 volts or so into the battery. Ohms Law tells us that watts is volts x amps, so your 175 watt panel will only put about 90 watts into the battery.
Using an MPPT controller with high voltage panels
The only way to get full power out of high voltage grid tie solar panels is to use an MPPT controller. See the link above for detailed into on MPPT charge controls. Since most MPPT controls can take up to 150 volts DC (some can go higher, up to 600 VDC) on the solar panel input side, you can often series two or more of the high voltage panels to reduce wire losses, or to use smaller wire. For example, with the 175 watt panel mentioned above, 2 of them in series would give you 66 volts at 7.6 amps into the MPPT controller, but the controller would convert that down to about 29 amps at 12 volts.
Charger Controller Types
Charge controls come in all shapes, sizes, features, and price ranges. They range from the small 4.5 amp (Sunguard) control, up to the 60 to 80 amp MPPT programmable controllers with computer interface. Often, if currents over 60 amps are required, two or more 40 to 80 amp units are wired in parallel. The most common controls used for all battery based systems are in the 4 to 60 amp range, but some of the new MPPT controls such as the Outback Power FlexMax go up to 80 amps.
Charge controls come in 3 general types (with some overlap):
Simple 1 or 2 stage controls which rely on relays or shunt transistors to control the voltage in one or two steps. These essentially just short or disconnect the solar panel when a certain voltage is reached. For all practical purposes these are dinosaurs, but you still see a few on old systems - and some of the super cheap ones for sale on the internet. Their only real claim to fame is their reliability - they have so few components, there is not much to break.
3-stage and/or PWM such Morningstar, Xantrex, Blue Sky, Steca, and many others. These are pretty much the industry standard now, but you will occasionally still see some of the older shunt/relay types around, such as in the very cheap systems offered by discounters and mass marketers.
Maximum power point tracking (MPPT), such as those made by Midnite Solar, Xantrex, Outback Power,
Morningstar and others. These are the ultimate in controllers, with prices to match - but with
efficiencies in the 94% to 98% range, they can save considerable money on larger systems since they provide 10 to 30% more power to the battery. For more information, see our article on MPPT.
Most controllers come with some kind of indicator, either a simple LED, a series of LED's, or digital meters. Many newer ones, such as the Outback Power, Midnite Classic, Morningstar MPPT, and others now have built in computer interfaces for monitoring and control. The simplest usually have only a couple of small LED lamps, which show that you have power and that you are getting some kind of charge. Most of those with meters will show both voltage and the current coming from the panels and the battery voltage. Some also show how much current is being pulled from the LOAD terminals.
All of the charge controllers that we stock are 3 stage PWM types, and the MPPT units. (in reality, "4-stage" is somewhat advertising hype - it used to be called equalize, but someone decided that 4 stage was better than 3). And now we even see one that is advertised as "5-stage"....
What is Equalization?
Equalization does somewhat what the name implies - it attempts to equalize - or make all cells in the battery or battery bank of exactly equal charge. Essentially it is a period of overcharge, usually in the 15 to 15.5 volt range. If you have some cells in the string lower than others, it will bring them all up to full capacity. In flooded batteries, it also serves the important function of stirring up the liquid in the batteries by causing gas bubbles. Of course, in an RV or boat, this does not usually do much for you unless you have been parked for months, as normal movement will accomplish the same thing. Also, in systems with small panels or oversized battery systems you may not get enough current to really do much bubbling. In many off-grid systems, batteries can also be equalized with a generator+charger.
What is PWM?
Quite a few charge controls have a "PWM" mode. PWM stands for Pulse Width Modulation. PWM is often used as one method of float charging. Instead of a steady output from the controller, it sends out a series of short charging pulses to the battery - a very rapid "on-off" switch. The controller constantly checks the state of the battery to determine how fast to send pulses, and how long (wide) the pulses will be. In a fully charged battery with no load, it may just "tick" every few seconds and send a short pulse to the battery. In a discharged battery, the pulses would be very long and almost continuous, or the controller may go into "full on" mode. The controller checks the state of charge on the battery between pulses and adjusts itself each time.
The downside to PWM is that it can also create interference in radios and TV's due to the sharp pulses that it generates. If you are having noise problems from your controller, see this page. What is a Load, or "Low Voltage Disconnect" output?
Some controllers also have a "LOAD", or LVD output, which can be used for smaller loads, such as small appliances and lights. The advantage is that the load terminals have a low voltage disconnect, so it will turn off whatever is connected to the load terminals and keep from running the battery down too far. The LOAD output is often used for small non-critical loads, such as lights. A few, such as the Xantrex C12, can also be used as a lighting controller, to turn lights on at dark, but the Morningstar SLC lighting controller is usually a better choice for that. Do not use the LOAD output to run any but very small inverters. Inverters can have very high surge currents and may blow the controller.
Most systems do not need the LVD function - it can drive only smaller loads. Depending on the rating of the controller, this may be from 6 to 60 amps. You cannot run any but the smallest inverter from the LOAD output. On some controllers, such as the Morningstar SS series, the load output can be used to drive a heavy duty relay for load control, gen start etc. The LOAD or LVD output is most often used in RV & remote systems, such as camera, monitor, and cell phone sites where the load is small and the site is unattended. What are the "Sense" terminals on my controller?
Some charge controllers have a pair of "sense" terminals. Sense terminals carry very low current, around 1/10th of a milliamp at most, so there is no voltage drop. What it does is "look" at the battery voltage and compares it to what the controller is putting out. If there is a voltage drop between the charge controller and the battery, it will raise the controller output slightly to compensate. These are only used when you have a long wire run between the controller and the battery. These wires carry no current, and can be pretty small - #20 to #16 AWG. We prefer to use #16 because it is not easily cut or squished accidentally. They attach to the SENSE terminals on the controller, and onto the same terminals as the two charging wires at the battery end.
What is a "Battery System Monitor"?
Battery system monitors, such as the Bogart EngineeringTriMetric 2025 are not controllers. Instead, they monitor your battery system and give you a pretty good idea of your battery condition, and what you are using and generating. They keep track of the total amp-hours into and out of the batteries, and the battery state of charge, and other information. They can be very useful for medium to large systems for tracking exactly what your system is doing with various charging sources. They are somewhat overkill for small systems, but are kind of a fun toy if you want to see what every amp is doing :-). TriMetric's newPentaMetric model also has a computer interface and many other features.
Renogy 100W Monocrystalline Solar Panel
Maximum Power: 100W
Optimum Operating Voltage (Vmp): 18.9V
Optimum Operating Current (Imp): 5.29A
Renogy 30A PWM Charge Controller
Renogy 100W Monocrystalline Solar Panel
Maximum Power: 100W
Optimum Operating Voltage (Vmp): 18.9V
Optimum Operating Current (Imp): 5.29A
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