Tuesday, November 20, 2012

Photovoltaic Power

This week’s article is about exciting developments in solar energy. I’m not referring to appliances like solar hot water heaters or ovens, but innovations that capture energy from the sun and convert it into electricity. Most of us are familiar with the photovoltaic cells that power calculators, flashlights and battery chargers, but aren’t yet aware of the breakthroughs made in the 2nd and 3rd generations of PV that will have a big impact in the future. How about: thin film collectors that roll out like window shades; solar spray paint that turns your windows into solar panels; nanowires, woven into your sails that will produce electricity; and even solar paint blended with nanoparticles to turn your home or boat into a huge solar panel? This isn’t some future dream, it’s now!

Although the means to produce solar electricity has been around for over 50 years, solar electricity generating devices, often referred to as photovoltaics or PV, are still considered cutting-edge technology. The promise of clean, cheap, and abundant electricity from the sun has been the dream of many scientists and businesses. As a result, every year a number of discoveries and advances are made, but most people know little or nothing about the current stage of PV technology.

In this installment I discuss the three generations of PV, and the equipment currently on the market and soon to be available.

1st Generation:  
Rigid Solar Panels. Originally developed for NASA for use in the space program, photovoltaics (PV) or solar cells are semiconductor devices that convert sunlight into direct current (DC) electricity. Solar cells are connected to form solar panels; panels are connected to create arrays, which can be used to charge batteries, operate motors, and power any number of electrical loads. By using a battery storage bank and an inverter, a PV system can produce alternating current (AC) compatible with conventional appliances.

A PV cell uses sunshine to strip electrons from a silicon wafer. A typical silicon PV cell is composed of a thin wafer consisting of an ultra-thin layer of phosphorus-doped (N-type) silicon on top of a thicker layer of boron-doped (P-type) silicon. An electrical field is created near the top surface of the cell where the two materials are in contact, called the P-N junction. When sunlight strikes the surface of a PV cell, this electrical field provides momentum and direction to light-stimulated electrons, resulting in a flow of current when the solar cell is connected to an electrical load.

2nd Generation:  
Thin Film Printed Panels. The big breakthrough in PV technology came when scientists and engineers discovered they could apply extremely thin layers of a semiconductor material (copper indium gallium diselenide, abbreviated as CIGS) to a low-cost backing such as glass, flexible metallic foil, high-temperature polymers or stainless steel sheets. Nanosolar, http://www.nanosolar.com/technology/technology-overview/ a company with manufacturing plants in Germany and San Jose, California, uses ink-jet printing technology to apply nanoparticle ink on continuous rolls of metallic film moving at high speed past the printer heads. The foil is then cut into strips to create solar panels that can be rolled up like window shades. The company’s long-term goal, once the production process is fully optimized, is to produce photovoltaic panels at 60 cents per watt and retail them for about $1.00 a watt. Their proprietary approach to printing CIGS and nanoparticle inks minimizes the use of expensive, high-vacuum manufacturing equipment.

These thin-film panels, which have revolutionized the marine PV market, are available to boaters in flexible, foldable, and rollable panels which can be compactly stowed and rolled out much like a window shade when needed, to provide solar power to keep batteries charged or to store electricity in a house battery bank for powering your inverter system. In my novel Boca Chita, (www.bocachita.net) Mark uses thin-film PV panels to charge his boat’s battery bank. Among the companies currently offering thin-film PV panels are http://www.powerfilmsolar.com/, Ganz GSP Marine Grade Solar Panels, and Brunton SolarRoll.

The 3rd Generation:  
Nanoparticles. Nanophotovoltaics are the third generation of PV and the latest in the quest to develop less-expensive, cheaper-to-produce solar panels that are even lighter than their predecessors. Right now, scientists are creating photovoltaic panels using technologies such as carbon nanotubes, nanowires, nanoantennas, and quantum dots. These nanophotovoltaics can consist of PV components that are 1/1,000th the thickness of a human hair, printed directly onto sheets of metal or other substrate.

Carbon Nanotubes: Using novel nanomaterials, researchers at Stanford University have built the first all-carbon solar cells. The carbon photovoltaics don’t produce much electricity, but as the technology is perfected, all-carbon cells could be inexpensive, printable, flexible, and tough enough to withstand extreme environments and weather.

Silicon Nanowires: About 1/1,000th the thickness of a human hair, each nanowire is a complete photovoltaic cell with a “p” (positive) and “n” (negative) junction. Cells manufactured with nanowire technology use minute amounts of silicon and can utilize a lower-grade of material, making them much less expensive to produce than crystalline silicon cells that need expensive, high-grade silicon. These nanowires could be woven into fabric from clothing to sails to produce PV electricity.

Microscopic antennas: 
http://www.sciencedaily.com/releases/2008/08/080810214010.htm Scientists at the U.S. Department of Energy's Idaho National Laboratory have learned to capture up to 80 percent of the sun’s mid-infrared rays. Their nanoantennas are 1/25th the width of a human hair. The material, which looks like gold on a sheet of plastic, could cost pennies a yard, be imprinted on flexible materials, and still draw energy after the sun has set. They are also able to absorb infrared heat and waste heat to produce electricity, which would allow the nanoantennas to cool buildings and computers without air conditioning. These nanoantennas could also be used in clothing which would warm or cool the wearer.

Nanospray: Solar Windows.
http://www.newenergytechnologiesinc.com/technology/solarwindow New Energy Technologies has developed a method of spraying windows with a transparent nano-thin PV material. Its PV cells are 1/4 the size of a grain of rice and 1/1,000th the thickness of a human hair. The tiny cells produce electricity from both natural and artificial light. The company is developing a product called SolarWindows, which uses the spray process to create electricity-producing windows. Researchers at the Tampa, Florida college, USF, have engineered a simple spray that makes any piece of glass a photovoltaic cell. This means that any window, glass, skylight or other glass structure on the outside of a building, house, or boat could be sprayed to produce photovoltaic power.

Solar Paint: 
http://news.softpedia.com/news/Cheap-Solar-Paint-to-Replace-Traditional-PV-242316.shtml Scientists at Notre Dame University have developed an innovative “solar paint” that relies on semiconducting nanoparticles called “quantum dots,” which they have blended into a spreadable compound that can be applied to any conductive surface without special equipment. Users would only have to apply a single coat of paint on the outside of their homes (or boats) to enable sunlight to activate the power-producing nanoparticles and produce clean, green electrical energy. It will soon be marketed under the name “Sun-Believable” paint.

Solar energy will play an increasingly important role in our future, but the future is now. Thin-film solar panels are routinely sold online and in retail marine stores; you can buy them in any size and roll them up until you’re ready to bugout and need them. Solar windows are available now. Solar paint is a reality. Think about how you might power your future from the ultimate renewable, sustainable source: the sun.

Next time, I’ll discuss marine electrical equipment, including generators, wind turbines, towed generators and inverter systems.

The Treasure Coast


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