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    Solar Power: From the basics to the technical

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    Post  bobhardee on Mon Jun 29, 2015 7:02 am

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    Post  bobhardee on Wed Jul 01, 2015 4:11 pm

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    Post  bobhardee on Sun Jul 05, 2015 7:12 pm

    This is not a solar set up but watch it anyway.

    https://www.youtube.com/watch?v=rW6M2ugucpc
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    Post  bobhardee on Mon Jul 20, 2015 8:25 am

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    Post  Carol on Mon Jul 20, 2015 8:55 am

    Hi Bob, Love your thread. Do you remember the one thread I started on that small solar unit? I've searched and can't find it. That info would go great in this thread. Mahalo, Carol


    _________________
    What is life?
    It is the flash of a firefly in the night, the breath of a buffalo in the wintertime. It is the little shadow which runs across the grass and loses itself in the sunset.

    With deepest respect ~ Aloha & Mahalo, Carol
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    Post  bobhardee on Wed Jul 22, 2015 2:03 pm

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    Post  bobhardee on Mon Jul 27, 2015 1:34 pm

    7/27/2015
    High efficiency solar

    https://www.youtube.com/watch?v=xmF9fLvCEDw
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    Post  bobhardee on Sat Aug 01, 2015 6:50 pm

    8/1/2015

    Full spectrum solar. Utilizing all the wave lengths that light has to offer and not just the yellow/green.


    A huge gain in this direction has now been made by a team of chemists at the University of California, Riverside that has found an ingenious way to make solar energy conversion more efficient. The researchers report in Nano Letters that by combining inorganic semiconductor nanocrystals with organic molecules, they have succeeded in "upconverting" photons in the visible and near-infrared regions of the solar spectrum.

    "The infrared region of the solar spectrum passes right through the photovoltaic materials that make up today's solar cells," explained Christopher Bardeen, a professor of chemistry. The research was a collaborative effort between him and Ming Lee Tang, an assistant professor of chemistry. "This is energy lost, no matter how good your solar cell. The hybrid material we have come up with first captures two infrared photons that would normally pass right through a solar cell without being converted to electricity, then adds their energies together to make one higher energy photon. This upconverted photon is readily absorbed by photovoltaic cells, generating electricity from light that normally would be wasted."

    Bardeen added that these materials are essentially "reshaping the solar spectrum" so that it better matches the photovoltaic materials used today in solar cells. The ability to utilize the infrared portion of the solar spectrum could boost solar photovoltaic efficiencies by 30 percent or more.

    In their experiments, Bardeen and Tang worked with cadmium selenide and lead selenide semiconductor nanocrystals. The organic compounds they used to prepare the hybrids were diphenylanthracene and rubrene. The cadmium selenide nanocrystals could convert visible wavelengths to ultraviolet photons, while the lead selenide nanocrystals could convert near-infrared photons to visible photons.

    In lab experiments, the researchers directed 980-nanometer infrared light at the hybrid material, which then generated upconverted orange/yellow fluorescent 550-nanometer light, almost doubling the energy of the incoming photons. The researchers were able to boost the upconversion process by up to three orders of magnitude by coating the cadmium selenide nanocrystals with organic ligands, providing a route to higher efficiencies.

    "This 550 -- nanometer light can be absorbed by any solar cell material," Bardeen said. "The key to this research is the hybrid composite material -- combining inorganic semiconductor nanoparticles with organic compounds. Organic compounds cannot absorb in the infrared but are good at combining two lower energy photons to a higher energy photon. By using a hybrid material, the inorganic component absorbs two photons and passes their energy on to the organic component for combination. The organic compounds then produce one high-energy photon. Put simply, the inorganics in the composite material take light in; the organics get light out."

    Besides solar energy, the ability to upconvert two low energy photons into one high energy photon has potential applications in biological imaging, data storage and organic light-emitting diodes. Bardeen emphasized that the research could have wide-ranging implications.

    "The ability to move light energy from one wavelength to another, more useful region, for example, from red to blue, can impact any technology that involves photons as inputs or outputs," he said.

    The research was supported by grants from the National Science Foundation and the US Army.

    The research was conducted also by the following coauthors on the research paper: Zhiyuan Huang (first author), Xin Li, Melika Mahboub, Kerry M. Hanson, Valerie M. Nichols and Hoang Le.

    Tang's group helped design the experiments and provided the nanocrystals.

    Story Source:

    The above post is reprinted from materials provided by University of California - Riverside. Note: Materials may be edited for content and length.
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    Post  bobhardee on Mon Aug 03, 2015 6:48 am

    8/3/2015

    https://www.youtube.com/watch?v=Vcssf6n00Ck

    I am looking for material on concentrated photovoltaic cells. If anyone who is watching this finds anything along that line, feel free to post. Research currently is focused on the utilization of the entire light wave which increases the efficiency from 20+% to 50+%. The draw back is keeping the solar cell cooled. You can get the higher efficiency but they must find a cheap way to cool it down so that run rate remains stable. Not sure if concentrating the solar is the right way to go but would appreciate any additional information.
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    Post  bobhardee on Sat Aug 08, 2015 8:28 pm

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    Post  bobhardee on Thu Nov 05, 2015 7:20 am

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    Post  bobhardee on Tue Nov 17, 2015 7:07 am

    11/16/2015
    These are down home southern boys in unrehearsed conversations. SE and SW Solar installation.

    https://www.youtube.com/watch?v=K-WCE-8Sku8
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    Post  bobhardee on Fri Nov 27, 2015 8:08 pm

    11/27/2015

    Tandem solar cells are simply better
    Higher efficiency thanks to perovskite magic crystal
    Date:
    November 23, 2015
    Source:
    Swiss Federal Laboratories for Materials Science and Technology (EMPA)
    Summary:
    Stacking two solar cells one over the other has advantages: Because the energy is 'harvested' in two stages, and overall the sunlight can be converted to electricity more efficiently. Researchers have come up with a procedure that makes it possible to produce thin film tandem solar cells in which a thin perovskite layer is used. The processing of perovskite takes place at just 50 degrees Celsius and such a process is potentially applicable for low cost roll-to-roll production in future.
    What is true for double-blade razors is also true for solar cells: two work steps are more thorough than one. Stacking two solar cells one on top of the other, where top cell is semi-transparent, which efficiently converts large energy photons into electricity, while the bottom cell converts the remaining or transmitted low energy photons in an optimum manner. This allows a larger portion of the light energy to be converted to electricity. Up to now, the sophisticated technology needed for the procedure was mainly confined to the realm of Space or Concentrated Photovoltaics (CPV). These "tandem cells" grown on very expensive single crystal wafers are considered not attractive for mass production and low cost solar electricity. The research team working under Stephan Buecheler and Ayodhya N. Tiwari from the Laboratory for Thin Films and Photovoltaics at Empa-Swiss Federal Laboratories for Material Science and Technology has now succeeded in making tandem solar cells that are based on polycrystalline thin films, and the methods are suitable for large area low cost processing, Flexible plastic or metal foils could also be used as substrate in future. This marks a major milestone on the path to mass production of high-efficiency solar cells with low cost processes.
    The secret behind the new process is that the researchers create the top solar cell perovskite film with a low-temperature procedure at just 50 degrees Celsius. This promises an energy-saving and cost-saving production stage for future manufacturing processes. The tandem solar cell yielded an efficiency rate of 20.5% when converting light to electricity. Already with this first attempt Empa researchers have emphasized that it has lots more potential to offer for better conversion of solar spectrum into electricity.
    Molecular soccer balls as a substrate for the magic crystal
    The key to this double success was the development of a 14.2% efficient semi-transparent solar cell, with 72% average transparency, made from methylammonium lead iodide deposited in the form of tiny perovskite crystals. The perovskite is grown on a thin interlayer made of the substance abbreviated as PCBM (phenyl-C61-butyric acid methyl ester) is used . Each PCBM molecule contains 61 carbon atoms interconnected in the shape of a soccer ball. The perovskite film is prepared by a combination of vapour deposition and spin coating onto this layer, which has tiny football like structure, followed by an annealing at a "lukewarm" temperature. This magic perovskite crystal absorbs blue and yellow spectrum of visible light and converts these into electricity. By contrast, red light and infrared radiation simply pass through the crystal. As a result, the researchers can attach a further solar cell underneath the semi-transparent perovskite cell in order to convert the remaining light into electricity.
    Advantage of the double-layer cell: better use of the spectrum of sunlight
    For the lower layer of the tandem solar cell, the Empa researchers use a CIGS cell (copper indium gallium diselenide), a technique that the team has been researching for years. Based on the CIGS cells, small-scale production is already under way for flexible solar cells (see Empa News from 11 June 2015). The advantage of tandem solar cells is that they exploit sunlight better. A solar cell can only convert radiation with an energy level higher than the bandgap of the semiconductor used. If the radiation energy is lower, no electricity is generated. If the radiation is higher in energy, the excess radiated energy is converted to heat and is lost. A double-layer solar cell like Empa's perovskite CIGS cell can combine substances with differing bandgaps and thus efficiently convert a larger share of the incident solar energy to electricity.
    More than 30% efficiency is possible
    While very good single-layer polycrystalline solar cell may practically convert a maximum of 25% of the solar energy to electricity, tandem solar cells could increase this figure to beyond 30%. That's according to Ayodhya Tiwari, head of the Thin Film and Photovoltaics laboratory. He does say, however, that a lot of research work is needed before that will be possible. "What we have achieved now is just the beginning. We will have to overcome many obstacles before reaching this ambitious goal. To do this, we will need lots of interdisciplinary experience and a large number of combinatorial experiments until we have found a semi-transparent high-performance cell together with the right base cell, and technologies for electrical interconnections of these solar cells."
    Stephan Bücheler, who coordinates the lab research in Tiwari's team, reminds us that the race for efficiency in solar cell research is certainly not just an academic show. "When producing solar-powered electricity, only half of the costs are down to the solar module itself. The other half are incurred for the infrastructure: inverters, cables, carriers for the cells, engineering costs and installation. These ancillary costs are reduced when the solar cells become more efficient and can be built in smaller sizes as a result. This means that efficient solar cells are the key to low-cost renewable electricity."
    ________________________________________
    Story Source:
    The above post is reprinted from materials provided by Swiss Federal Laboratories for Materials Science and Technology (EMPA). Note: Materials may be edited for content and lengt
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    Post  bobhardee on Wed Dec 23, 2015 7:59 am

    12/23/2015
    Berkeley Lab Research News
    An unexpected discovery could yield a full spectrum solar cell
    Contact: Paul Preuss, paul_preuss@lbl.gov
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    BERKELEY, CA � Researchers in the Materials Sciences Division (MSD) of Lawrence Berkeley National Laboratory, working with crystal-growing teams at Cornell University and Japan's Ritsumeikan University, have learned that the band gap of the semiconductor indium nitride is not 2 electron volts (2 eV) as previously thought, but instead is a much lower 0.7 eV.

    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.

    The serendipitous discovery means that a single system of alloys incorporating indium, gallium, and nitrogen can convert virtually the full spectrum of sunlight -- from the near infrared to the far ultraviolet -- to electrical current.

    "It's as if nature designed this material on purpose to match the solar spectrum," says MSD's Wladek Walukiewicz, who led the collaborators in making the discovery.

    What began as a basic research question points to a potential practical application of great value. For if solar cells can be made with this alloy, they promise to be rugged, relatively inexpensive -- and the most efficient ever created.

    In search of better efficiency

    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.

    A tantalizing lead

    The first clue to an easier and better route came when Walukiewicz and his colleagues were studying the opposite problem -- not how semiconductors absorb light to create electrical power, but how they use electricity to emit light.

    "We were studying the properties of indium nitride as a component of LEDs," says Walukiewicz. In light-emitting diodes and lasers, photons are emitted when holes recombine with electrons. Red-light LEDs have been familiar for decades, but it was only in the 1990s that a new generation of wide-band gap LEDs emerged, capable of radiating light at the blue end of the spectrum.

    Light emitting diodes made of indium gallium nitride held clues to the potential new solar cell material.

    The new LEDs were made from indium gallium nitride. With a band gap of 3.4 eV, gallium nitride emits invisible ultraviolet light, but when some of the gallium is exchanged for indium, colors like violet, blue, and green are produced. The Berkeley Lab researchers surmised that the same alloy might emit even longer wavelengths if the proportion of indium was increased.

    "But even though indium nitride's band gap was reported to be 2 eV, nobody could get light out of it at 2 eV," Walukiewicz says. "All our efforts failed."

    Previously the band gap had been measured on samples created by sputtering, a technique in which atoms of the components are knocked off a solid target by a beam of hot plasma. If such a sample were to be contaminated with impurities like oxygen, the band gap would be displaced.

    To get the best possible samples of indium nitride, the Berkeley Lab researchers worked with a group at Cornell University headed by William Schaff, renowned for their expertise at molecular beam epitaxy (MBE), and also with a group at Ritsumeikan University headed by Yasushi Nanishi. In MBE the components are deposited as pure gases in high vacuum at moderate temperatures under clean conditions.

    When the Berkeley Lab researchers studied these exquisitely pure crystals, there was still no light emission at 2 eV. "But when we looked at a lower band gap, all of a sudden there was lots of light," Walukiewicz says.

    The collaborators soon established that the alloy's band-gap width increases smoothly and continuously as the proportions shift from indium toward gallium, until -- having covered every part of the solar spectrum -- it reaches the well-established value of 3.4 eV for simple gallium nitride.

    Promising signs

    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.

    The Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

    Additional information

    "Effects of the narrow band gap on the properties on InN," by J. Wu, W. Walukiewicz, W. Shan, K. M. Yu, J. W. Ager III, E. E. Haller, Hai Lu, and William J. Schaff, appears in the journal Physical Review B, 15 November 2002.
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    Post  bobhardee on Mon Dec 28, 2015 7:50 am

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    Post  bobhardee on Fri Feb 05, 2016 8:32 am

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    Post  bobhardee on Sun Feb 28, 2016 4:46 pm

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    Post  bobhardee on Thu Mar 03, 2016 7:16 pm

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    Post  bobhardee on Fri Mar 04, 2016 7:30 am

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    Post  bobhardee on Sun Apr 03, 2016 6:46 am

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    Post  bobhardee on Tue Apr 12, 2016 8:37 am

    4/12/2016 His "system has paid for itself 6 times over!!!!"


    https://www.youtube.com/watch?v=Vel9LH57RII
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    Post  bobhardee on Sun Apr 17, 2016 6:28 am

    4/17/2016 This video has nothing to do with solar power. However, it was made by one of the people who have numerous free videos on that subject and I am posting it as a thank you to him. It is about a property for sale in Western NC that was owned by a friend of his who he is trying to help out.

    https://www.youtube.com/watch?v=_JiOQKGtU3Y
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    Post  bobhardee on Tue May 03, 2016 7:32 am

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    Post  bobhardee on Thu May 05, 2016 6:58 am

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    Post  bobhardee on Sat May 07, 2016 11:06 am


      Current date/time is Thu Feb 27, 2020 6:26 am