science – ZacharyShahan.com

Climate Science In The Classroom (Fun Climate Education + Climate Action)

In the wake of dire warnings about the future and current threats of global warming and climate change from the US government, the International Panel on Climate Change (IPCC), and the International Energy Agency (IEA), it’s clear that we need to tackle our illogical fossil fuel addiction fast. It’s critical that we tackle this issue [&hellip

Climate Science In The Classroom (Fun Climate Education + Climate Action) was originally posted on: PlanetSave. To read more from Planetsave, join thousands of others and subscribe to our free RSS feed, follow us on Facebook (also free), follow us on Twitter, or just visit our homepage.

By Zachary Shahan | May 15, 2014 | Climate Change |

From Selenium to Silicon and Beyond: Celebrating the 60th Anniversary of the First Solar Cell Capable of Converting Enough Sunlight Directly into Electricity for Practical Power

By John Perlin, author of Let It Shine*

The solar cell had its birth in 1873, as bars of selenium. When two British scientists, William Grylls Adams and Richard Evans Day, in 1876 exposed the bars to candlelight they discovered something totally new: that light, not heat, could directly generate electricity in certain materials such as selenium. Adams and Day called the current produced this way, “photoelectric.” But try as they may, no one could increase selenium’s low conversion of sunlight into electricity and scientists concluded that to realize the vision of solar cells powering the world would require finding a new photovoltaic material.

That came when the collaborative effort of Daryl Chapin, Calvin Fuller and Gerald Pearson at Bell Laboratories developed a photovoltaic device capable of converting enough sunlight directly into electricity to generate useful amounts of power. Their public display at Bell’s press conference on April 25, 1954 of a 21-inch Ferris wheel spinning round and round powered by the first watt of silicon solar cells presented to the world one of the most significant breakthroughs ever recorded in the history of solar energy and of electricity. The New York Times realized the importance of what its reporters saw, stating on its front page that the invention of the Bell silicon solar cell marked “the beginning of a new era, eventually leading to the realization of one of mankind’s most cherished dreams – the harnessing of the almost limitless energy of the sun for the uses of civilization.” US News and World Report speculated that the new solar cell “may provide more power than all the world’s coal, oil and uranium…[its] future is limitless.”

At the time of the Bell announcement in 1954, all the solar cells in the world delivered about one watt. Today, more than 100 billion watts of generating capacity of photovoltaics have been installed worldwide. This year not only marks the 60th anniversary of the silicon solar cell but also the beginning of reaching the Holy Grail solar scientists had only previously dreamt of – entering the Era of Grid Parity Era, where solar panels generate power at costs equal to or less than electricity produced by fossil fuels and nuclear. With the phenomenal growth of solar PV in the last several years and its future even brighter, the time is ripe to celebrate the founding of a technology that led Science magazine almost forty years ago to declare, “If there is a dream solar technology, it is photovoltaics — solar cells…a space-age electronic marvel at once the most sophisticated solar technology and the simplest, most environmentally benign source of electricity yet conceived.”

*The material for the article comes from John Perlin’s recently published book, Let It Shine: The 6000-Year Story. John and the crew at Renewables100 recently organized a 60-year birthday party for solar in Palo Alto, California.

From Selenium to Silicon and Beyond: Celebrating the 60th Anniversary of the First Solar Cell Capable of Converting Enough Sunlight Directly into Electricity for Practical Power was originally published on Solar Love!.

Biodegradable, Implantable Battery Can Melt In Your Body

Modern medicine does not fall behind other business in this age of technology. Modern medicine focuses on integrating life-changing advances with progressive technological advances. A recent marriage of medicine and technology hopes to enable progress in monitoring and administering treatment with difficult health circumstances. This recent progress is a biodegradable, implantable battery that will help

Biodegradable, Implantable Battery Can Melt In Your Body was originally published on CleanTechnica.

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By Cynthia Shahan | March 31, 2014 | Health |

Cleaner Cooking Fuels & Improved Kitchen Ventilation Lead To Far-Better Lung-Health, 9-Year Study Shows

The switch from relatively dirty types of cooking fuels, such as biomass, to cleaner ones — along with improvements to kitchen ventilation — can greatly reduce the likelihood of developing chronic obstructive pulmonary disease (COPD), as well as improve other markers of lung health, according to the results of a 9-year study conducted in southern

Cleaner Cooking Fuels & Improved Kitchen Ventilation Lead To Far-Better Lung-Health, 9-Year Study Shows was originally published on CleanTechnica.

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By James Ayre | March 31, 2014 | Health |

Concepts In Photovoltaic Technology

Since the first solar cell was produced by Bell Labs in the 1950s, solar photovoltaic (PV) technology has been gradually evolving. The work resulted in the development of a compound which is formed of semiconductor elements found in the periodic table and the synthesis of an organic solar cell. Broadly, photovoltaic technologies are now classified as: crystalline silicon solar cells, thin-film solar cells, and organic solar cells. In the following paragraphs, an overview of various concepts in photovoltaic technology based on crystalline silicon wafers are briefly described. Such concepts were used from the early 1990s to deliver relatively high-efficiency solar modules for the market. As the $/watt of a solar panel is dropping, the evolution in photovoltaic technology is also progressing.

High-efficiency concepts of crystalline silicon (c-Si) wafer based solar cells

Many researchers are working on c-Si solar cell solutions aimed at overcoming the limitations faced using the traditional method of photovoltaic technology production. The prime approach to increase the efficiency of c-Si solar cell would reduce both surface and bulk recombination within the cell. For this reason, most of the high-efficiency c-Si solar cells is based on monocrystalline wafers. Notably, in c-Si PV technology, there are three important concepts: PERL, IBC, and Hetero-junction types of solar cells.

1. PERL: PERL is an abbreviation for Passivated Emitter Rear Locally diffused. This concept was first developed by Prof. Martin Green’s group at the University of New South Wales (UNSW) in the late 1980s and early 1990s. Many of us who know him have dubbed him as a “father of photovoltaics.” Through this concept, a collaboration between Suntech and UNSW achieved a 20.3% efficiency record for a production solar cell in March 2012. This concept has been an example for various PV technologies developed afterwards. Figure 1, below, shows the PERL solar cell concept, which uses p-type Float zone silicon wafers.

Fig 1 : PERL solar cell.

In the PERL concept, the front contact area, the emitter layer, and the rear contact are together able to achieve higher efficiency.

Now, the optical losses in the front contact area are reduced by implementing a textured inverted pyramid structure coated with an anti-reflector. The contact area at the front side has been made as small as possible. This enhances the total amount of light coupled into the solar cell by allowing collection of reflected light for the second time with less shadowing losses.
The emitter is heavily doped underneath the contacts. In PERL, this is achieved by phosphorous-diffused regions. The rest of the emitter is moderately doped to preserve the “blue response.” A silicon oxide is passivated on the top of the emitter to suppress the surface recombination velocity.
In the rear surface of the solar cell, point contacts are used in combination with the thermal oxide passivation layers to reduce the unwelcome surface recombination at the uncontacted area. Heavily doped boron acts as a local back surface to limit the recombination of the minority electrons at the metal back.

2. IBC: IBC is an abbreviation for an Interdigited Back Contact solar cell. Back-contacted solar cells, in contrast to PERL, use n-type Float zone monocrystalline wafers. SunPower commercialized IBC solar cell modules with an initial achievement of 22.5% of efficiency. Now SunPower has achieved an efficiency of 24.2% from a monocrystalline silicon IBC solar cell.

Fig 2: IBC solar cell.

The IBC solar cell has many localized junctions instead of a single large p-n junction. The electron-hole pairs generated by the incident light that is absorbed at the front surface can still be collected at the rear of the cell. The semiconductor-metal interfaces are kept as small as possible to reduce the unwelcome recombination at this defect-rich interface. Such a small cross-section of metal fingers also reduces the resistive losses of the contacts. As depicted in Figure 2, the back of the IBC solar cell has two metal grids. One collects the current from the n-type contact and the other contact collects the current from the p-type contact. The front surface field is created by being heavily n-doped at the front of the cell to reduce surface recombination. However, the doping intensity decreases gradually towards the back to act as a p-doped region. Finally, it behaves like a p-n junction. The front surface acts as a passivation (silicon dioxide) of the defects at the front interface. As in case of PERL, the top front surface is textured and deposited with double layered anti-reflection coating.

3. Hetero-junction: So far, both PERL and IBC solar cells are homo-junction solar cells, or a p-n junction with a depletion zone (i.e., these junctions are fabricated by different doping types within the same semiconductor material). This means that the band gap in the p- and n-doped material is the same. However, in hetero-junction solar cells, the junction is made from two different semiconductor materials. One semiconductor material is p-doped and the another type of semiconductor is n-doped. The crystalline silicon wafer–based hetero-junction solar cell concept was invented by the Japanese company Sanyo, which is currently part of Panasonic. It is also called a HIT solar cell, which stands for heterostructure with intrinsic thin film, and has achieved an efficiency of 24.7%.

Fig 3: Hetero-Junction solar cell.

In c-Si wafer–based hetero-junction solar cells, one semiconductor material is from an n-type float zone monocrystalline silicon wafer and the other material from hydrogenated amorphous silicon. As depicted in Figure 3, there are two junctions — front and rear — in the solar cell. The front junction is formed by a thin layer of intrinsic amorphous silicon with deposition of a thin layer of p-doped amorphous silicon on top of it. In Figure 3, i/p a-Si stands for intrinsic p-doped amorphous silicon. Similarly, the rear junction (i/n a-Si) is composed of a thin layer of intrinsic amorphous with deposition of n-doped amorphous silicon on top. HIT allows the introduction of the n-type backside contact scheme as seen in IBC, thus allowing it to use a bi-facial configuration (i.e., it can collect light from the front as well as scattered and diffuse light falling on the back of the solar cell).

Remarks

A comparison remark of the above three concepts is presented here. From this remark, a customer can decide which is the right PV technology for their needs. The c-Si wafer–based HIT solar cell from Panasonic achieved an efficiency of 24.7% on a wafer size of 102 square centimeters, making it a favorable PV technology in the commercial market. However, it is still important to acknowledge the below remarks.

1. PERL vs IBC

Often, the PERL concept requires a more expensive process in fabrication than IBC or HIT. The IBC solar cell doesn’t suffer from shading losses of a front metal contact grid. And due to the use of n-type float zone c-Si wafers, the IBC solar cell doesn’t suffer from light-induced degradation. Another important note is that the IBC n-type silicon wafer is not sensitive to impurities like iron impurities. However, in PERL p-type float zone c-Si wafers, boron doping is homogeneously distributed over the IBC n-type float zone c-Si wafer. This means that within one n-type wafer the electrical properties can vary, resulting in a lower energy yield of solar cell production from n-type float zone c-Si wafers like IBC.

2. PERL & IBC vs HIT

In HIT solar cells, the use of amorphous silicon in the contact area makes it a good passivation material which enables a longer lifetime of the charge carriers, thereby increasing the yield. In PERL and IBC, diffusion to the contacts takes place in the emitter layer through a metal finger spacing, but in HIT, it occurs through a transparent conductive oxide metal ITO which shortens the diffusion length as compared with PERL and IBC.

Concepts In Photovoltaic Technology was originally published on Solar Love!.

First 3-D Nanoscale Observations Of Structural Changes In Rechargeable Battery Material During Operation

The first 3-D nanoscale observations of the structural changes that occur in the anode of a lithium-ion battery during operation (discharging and recharging) were recently achieved by researchers at the US Department of Energy’s Brookhaven National Laboratory. This achievement is expected to lead to a much greater understanding of such processes, and, as a result,

First 3-D Nanoscale Observations Of Structural Changes In Rechargeable Battery Material During Operation was originally published on CleanTechnica.

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By James Ayre | March 31, 2014 | Energy Storage |

High-Energy Biofuel For Rockets, Missiles, And Other Aerospace Applications, Via Engineered Bacteria

A high-energy biofuel — potentially capable of replacing or supplementing expensive missile fuels, such as JP10 — has been created via the use of a genetically engineered bacterium by researchers at the Georgia Institute of Technology and the Joint BioEnergy Institute.

For those wondering, the hydrocarbon in question, pinene, is actually exactly what it sounds like, a chemical produced by trees (especially pine trees). Kind of funny when you think about it — rockets powered by a chemical used by trees to repel insects produced by bacteria genetically engineered by humans. :/

Georgia Tech researchers examine the production of the hydrocarbon pinene in a series of laboratory test tubes. Shown are (l-r) Pamela Peralta-Yahya, an assistant professor in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering, and Stephen Sarria, a graduate student in the School of Chemistry and Biochemistry.
Image Credit: Georgia Tech Photo, Rob Felt

Improvements to the process are still necessary in order for it to become economically viable (production boosted 26-fold), but given the great value placed on high-energy fuels by governments/militaries/etc, it’s very likely that we’ll hear more about this in the relatively near future.

The researchers also note the interesting fact that the biofuel could potentially help “facilitate (the) development of a new generation of more powerful engines.” Hmmm…

The Georgia Institute of Technology provides more:

By inserting enzymes from trees into the bacterium, first author and Georgia Tech graduate student Stephen Sarria, working under the guidance of assistant professor Pamela Peralta-Yahya, boosted pinene production six-fold over earlier bioengineering efforts. Though a more dramatic improvement will be needed before pinene dimers can compete with petroleum-based JP-10, the scientists believe they have identified the major obstacles that must be overcome to reach that goal.

“We have made a sustainable precursor to a tactical fuel with a high energy density,” stated Peralta-Yahya, an assistant professor in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech. “We are concentrating on making a ‘drop-in’ fuel that looks just like what is being produced from petroleum and can fit into existing distribution systems.”

Given the fact that JP-10 is itself a very limited fuel — only so much can be extracted from any single barrel of oil — the potential for it to be replaced by a (relatively) expensive biofuel is much greater than it is for something like gasoline. JP-10 currently sells for around $25 per gallon.

“If you are trying to make an alternative to gasoline, you are competing against $3 per gallon,” Peralta-Yahya continued. “That requires a long optimization process. Our process will be competitive with $25 per gallon in a much shorter time.”

More information on the research process:

Peralta-Yahya and collaborators set out to improve on previous efforts by studying alternative enzymes that could be inserted into the E. coli bacterium. They settled on two classes of enzymes — three pinene synthases (PS) and three geranyl diphosphate synthases (GPPS) — and experimented to see which combinations produced the best results.

Their results were much better than earlier efforts, but the researchers were puzzled because for a different hydrocarbon, similar enzymes produced more fuel per liter. So they tried an additional step to improve their efficiency. They placed the two enzymes adjacent to one another in the E. coli cells, ensuring that molecules produced by one enzyme would immediately contact the other. That boosted their production to 32 milligrams per liter — much better than earlier efforts, but still not competitive with petroleum-based JP-10. Peralta-Yahya believes the problem now lies with built-in process inhibitions that will be more challenging to address.

“We found that the enzyme was being inhibited by the substrate, and that the inhibition was concentration-dependent,” she explained. “Now we need either an enzyme that is not inhibited at high substrate concentrations, or we need a pathway that is able to maintain low substrate concentrations throughout the run. Both of these are difficult, but not insurmountable, problems.”

“Even though we are still in the milligrams per liter level, because the product we are trying to make is so much more expensive than diesel or gasoline means that we are relatively closer.”

The new findings were published in the journal ACS Synthetic Biology.

High-Energy Biofuel For Rockets, Missiles, And Other Aerospace Applications, Via Engineered Bacteria was originally published on CleanTechnica. To read more from CleanTechnica, join over 50,000 other subscribers: Google+ | Email | Facebook | RSS | Twitter.

New Prototype Home That’s Heated & Cooled Entirely By Fermenting Straw

A new prototype home that is heated and cooled entirely through the action of fermenting straw has been created by researchers at Japan’s Waseda University. It might sound like a strange idea — or perhaps even unbelievable — but the concept has actually been around for a couple of decades now, and has been utilized

New Prototype Home That’s Heated & Cooled Entirely By Fermenting Straw was originally published on CleanTechnica.

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By James Ayre | March 30, 2014 | Energy Efficiency |

MAGNETIDE Project — Purpose Designed Generator For Wave Energy Technologies

The EU’s MAGNETIDE project continues to move forward — 14 months into the projected 24-month development program, the gains are becoming apparent.

The project — which is intended to result in the development of a purpose-designed generator for wave energy extraction — has managed to reduce the cost of the system while increasing the efficiency by up to 30%. These improvements were achieved via the modification of the generator’s design, so that components manufactured using PIM, Powder Injection Moulding, could be installed.

Researchers have modified the generator’s design so that components manufactured using PIM, Powder Injection Moulding, could be installed.
Image Credit: Universidad Carlos III de Madrid – Oficina de Información Científica

“These generators use magnetic components that we are producing using PIM technology, which turns out to be more versatile when it comes to modifying the compositions and makes it possible to get the parts for a lower price,” states professor José Manuel Torralba, the researcher who is coordinating UC3M’s participation in the project.

This powder injection moulding has shown itself to be an available alternative to more-conventional approaches in the (relatively) fast manufacture of complex parts — as a paper the researchers recently published in the International Journal of Microstructure and Materials Properties has shown.

The press release from the Universidad Carlos III de Madrid – Oficina de Información Científica provides more:

Powder Injection Moulding is an advanced powder metallurgy technology that combines the advantages of plastic injection moulding and powder technology. It is similar to making bread in an oven but, rather than flour, it uses alloys of metallic powders that “bake” in moulds and produce milimetrically exact parts. In this case, the scientists are studying the best combination of metallic powders with a magnetic character (iron, silicon, cobalt, nickel…) in order to later inject them into a polymer plastic mould that will allow them to create complex parts that are difficult and expensive to produce mechanically.

“The great advantage of this technology is that once you design the material, by modifying the mould, it is easy to manufacture millions of pieces that are exactly the same, in a manner that is simple, fast and quite inexpensive,” Torralba explains.

The MAGNETIDE project is expected to wrap up next year, when the researchers are expected to have created the first prototypes of the new generators made with this technology. These generators — also potentially useful for other energy sources, such as wind — will then be tested in real-world conditions, in locations where there are strong tidal currents.

MAGNETIDE Project — Purpose Designed Generator For Wave Energy Technologies was originally published on CleanTechnica. To read more from CleanTechnica, join over 50,000 other subscribers: Google+ | Email | Facebook | RSS | Twitter.

Closure Of Coal-Burning Power Plant In Tongliang, China Led To Great Improvements In Children’s Health, Research Shows

Childhood developmental scores and levels of brain-derived neurotrophic factor (BDNF) — a key protein for brain development — are significantly higher with decreased levels of exposure to air pollution in utero, according to a new study that examined the after-effects of the closure of a coal-burning power plant in Tongliang, China. The study — performed

Closure Of Coal-Burning Power Plant In Tongliang, China Led To Great Improvements In Children’s Health, Research Shows was originally published on CleanTechnica.

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By James Ayre | March 30, 2014 | Health |

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