Monday, November 25, 2013

Upping sea level rise

Sea-level rise in this century is likely to be 70-120 centimeters if greenhouse-gas emissions are not mitigated, a broad assessment of the most active scientific publishers on that topic has revealed. The 90 experts participating in the survey anticipate a median sea-level rise of 200-300 centimeters by the year 2300 for a scenario with unmitigated emissions.

In contrast, for a scenario with strong emissions reductions, experts expect a sea-level rise of 40-60 centimeters by 2100 and 60-100 centimeters by 2300. The survey was conducted by a team of scientists from the USA and Germany.

"While the results for the scenario with climate mitigation suggest a good chance of limiting future sea-level rise to one meter, the high emissions scenario would threaten the survival of some coastal cities and low-lying islands," says Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research. "From a risk management perspective, projections of future sea-level rise are of major importance for coastal planning, and for weighing options of different levels of ambition in reducing greenhouse-gas emissions."

Projecting sea-level rise, however, comes with large uncertainties, since the physical processes causing the rise are complex. They include the expansion of ocean water as it warms, the melting of mountain glaciers and ice caps and of the two large ice sheets in Greenland and Antarctica, and the pumping of ground water for irrigation purposes. Different modeling approaches yield widely differing answers. The recently published IPCC report had to revise its projections upwards by about 60 percent compared to the previous report published in 2007.

Wednesday, November 20, 2013

Can individual action save the day?

At a major United Nations climate summit in Warsaw this week, a plan is being hammered out (in the 19th annual effort) for negotiations on a new climate treaty to be finalized in Paris in two years’ time. Delegates from 195 nations are also seeking to obtain commitments from countries to limit their greenhouse-gas emissions between now and 2020.

The moot question : will it make any difference? The path ahead is rife with disputes between rich and poor countries over funding, and how to allocate and enforce emissions reductions. The conference aims to outline the schedule and to set parameters for negotiations ahead of the next major climate summit in Paris in 2015, when countries hope to forge a treaty to follow the 2009 agreement settled on in Copenhagen. At Copenhagen, negotiations over a formal treaty broke down, but eventually resulted in a set of non-binding pledges — the Copenhagen Accord — for emissions reductions until 2020. The accord also blurred the distinction between developed countries, which were bound by the 1997 Kyoto Protocol to reduce emissions.

The Warsaw talks are split into two main tracks. One focuses on the architecture of a new global climate treaty that would take effect after 2020, when the current Copenhagen commitments expire. The second examines what can be done to strengthen commitments between now and 2020 to increase the chance of limiting global warming to a target of 2
°C above pre-industrial temperatures (see ‘Emissions up in the air?’).

Indigenous leaders from across North America met half a world away and offered a prophecy: The solution will never come via the UN talks. Tribal elders from the United States, Greenland and Mexico spoke of the need for individual action rather than government edicts, and of the difficulty – and urgency – of replacing economic questions with moral ones.

A return to the "old values:" Respect, concern for the future, and sharing – alone can help the world they believe. But as one elder pointed, it is a colossal task to get people to change. “How do you instruct 7 billion people as to their relationship to the Earth?" he asked. "It's very difficult – when you're struggling to protect your people and you're hanging by a thread – to instruct other people."

Friday, November 15, 2013

Solar bonanza

A new solar cell material has properties that might lead to solar cells more than twice as efficient as the best on the market today. The material—a modified form of a class of compounds called perovskites, promises to be a good choice though not experimentally used.

Researchers are making new perovskites using combinations of elements and molecules not seen in nature; many researchers see the materials as the next great hope for making solar power cheap enough to compete with fossil fuels. Perovskite-based solar cells have been improving at a remarkable pace. It took a decade or more for the major solar cell materials used today—silicon and cadmium telluride—to reach efficiency levels that have been demonstrated with perovskites in just four years.

The perovskite material described in the latest Nature has properties that could lead to solar cells that can convert over half of the energy in sunlight directly into electricity according to the center for energy innovation at the University of Pennsylvania.

That’s more than twice as efficient as conventional solar cells. Such high efficiency would cut in half the number of solar cells needed to produce a given amount of power. Besides reducing the cost of solar panels, this would greatly reduce installation costs, which now account for most of the cost of a new solar system.

Unlike conventional solar cell materials, the new material doesn’t require an electric field to produce an electrical current. This reduces the amount of material needed and produces higher voltages, which can help increase power output. While other materials have been shown to produce current without the aid of an electric field, the new material is the first to also respond well to visible light, making it relevant for solar cells.


The researchers also showed that it is relatively easy to modify the material so that it efficiently converts different wavelengths of light into electricity. It could be possible to form a solar cell with different layers, each designed for a specific part of the solar spectrum, something that could greatly improve efficiency compared to conventional solar cells.

Friday, November 8, 2013

Aluminum to the rescue

When it comes ot fuel cells , the challenge of storing the hydrogen has been vexing. Lightweight interstitial hydrides -- compounds in which hydrogen atoms occupy the interstices (spaces) between metal atoms -- have now been proposed as a safe and efficient means for storing hydrogen for fuel cell vehicles. And fuel cells are what many see as the future.

Hydrides using magnesium, sodium and boron have been manufactured, but so far, none have proven practical as a hydrogen repository. An aluminum-based alloy hydride offers a more viable candidate because it has the desired traits of light weight, no toxicity to plants and animals, and absence of volatile gas products except for hydrogen.

Until now, however, only complex aluminum hydrides -- unsuitable for use as a hydrogen storage system -- have been created. In a recent paper in the AIP Publishing journal APL Materials, a joint research group with members from the Japan Atomic Energy Agency (Hyogo, Japan) and Tohoku University (Sendai, Japan) announced that it had achieved the long-sought goal of a simple-structured, aluminum-based interstitial alloy.

“Although its synthesis requires very extreme conditions and its hydrogen content is low, our new compound showed that an aluminum-based alloy hydride is achievable," said Hiroyuki Saitoh, lead author of the APL Materials paper. "Based on what we've learned from this first step, we plan to synthesize similar materials at more moderate conditions -- products that hopefully will prove to be very effective at storing hydrogen."

Wednesday, November 6, 2013

Glaring truth!

Energy consumption continues to grow. The costs of generation and transmission of energy must come down for the increased consumption to be sustainable. Energy must be generated without depleting resources, without causing pollution, and without incurring waste. Transmission of energy too must be efficient. Big challenge. But experts insist it can be an easy solution - onsite generation of electricity using the photovoltaic (PV) method of converting solar energy directly into electrical energy.

Nothing new in that but more and more scientists are focusing on the advantages of solar PV instead of the disadvantages like intermittency, storage, etc. For instance, silicon is the second most abundant element in the earth’s crust. Then consider the power saved. The creation of local DC power grids can save power being lost in the transmission and unnecessary conversion from DC to alternating current (AC) and then back to DC. Most electronic appliances and electric loads operate on DC and by transmitting and converting AC power to DC about 30% of the total power generated is lost.

The use of thin films of semiconductors such as cadmium telluride, amorphous silicon and copper indium gallium arsenide is still to make a major commercial impact. PV modules comprising organic and dye-sensitized solar cells shall not play a role in bulk power generation, without fundamental breakthroughs in material synthesis and performance.

Researchers at Penn University have proposed a new multi-terminal multi-junction architecture for inexpensive PV electricity generation. Efficiency will exceed the currently feasible 25%. The proposed architecture is based on the use of currently commercial crystalline solar cells and thin-film solar cells made of materials (such as copper oxide) that are abundant in Earth's crust. However, the additional manufacturing costs to be incurred thereby remain unknown, according to the researchers.


Empa scientists have developed a new technique for manufacturing high-efficiency, flexible, thin film solar cells from CIGS (copper indium gallium di-selenide) semiconductors. This has enabled them to achieve an efficiency of 20.4% for the conversion of sunlight into electrical energy. As the solar cells are deposited onto plastic foils, they could be produced on an industrial scale using cost-effective roll-to-roll manufacturing. The researchers are presenting a new manufacturing technique for CIGS solar cells, in which tiny quantities of sodium and potassium are incorporated into the CIGS layer.

All the research points to the sun as the future source of energy. More reason why we should be thinking of local micro grids rather than centrally generated power with potential for huge losses in transmission!

Revenue from pricing carbon emissions can exceed loss for plant owners

Stabilizing global warming at around 2 degrees Celsius by cutting greenhouse-gas emissions from fossil fuels would mean to leave much of coal, gas and oil unused underground. Yet the instrument of pricing global CO2 emissions could generate a revenue of 32 trillion US dollars over the 21st century, exceeding by far the 12 trillion US dollars reduction of fossil fuel owners' profits, according to a study now published by scientists of the Potsdam Institute for Climate Impact Research.

"Implementing ambitious climate targets would certainly scale down fossil fuel consumption, so with reduced demand their prices would drop," says Nico Bauer, lead-author of the study. "The resulting profit loss would be overcompensated by revenues from auctioning emissions permits or taxing CO2, which are two of the possible instruments of climate policy."

The distribution of revenues from emissions pricing depends on how climate policies are implemented on a national and international level. "Moreover, revenues from pricing carbon cannot be simply seen as a compensatory fund for the loss of income from fossil fuels," says Bauer. "This is because climate policy results in higher energy prices for households and companies, which lead to a -- rather small -- reduction of economic output. So there might be many appetites for the money raised from CO2 pricing."


We know that fossil fuel owners will lose out on profits, but the big question is who will benefit from the new revenues generated by climate policy? It will fall to policy makers and society at large to decide this, adds Elmar Kriegler, project leader and co-author of the study. "It would be interesting to ask for the effect of using the revenues from carbon pricing to finance infrastructure investments in developing countries."

Tuesday, November 5, 2013

Powered from Space

India’s ambitious Mars Mission saw a successful launch today. The 1350 kg satellite was placed in an elliptical earth orbit from where it will be transfered into a heliocentric one and from there to Mars will be the last leap. The 400 million km odyssey will take around a year roughly, if everything goes smoothly.

The craft carries 850 kilograms of propellant and oxidiser.
Propellant is the chemical mixture burned to produce thrust in rockets and consists of a fuel and an oxidizer. By controlling the flow of propellant to the combustion chamber, the engine can be throttled, stopped, or restarted. The main engine uses the bipropellant combination monomethyl hydrazine and dinitrogen tetroxide for orbit insertion and other manoeuvres. But the craft is largely powered by solar cells.

Some of Nasa’s deep space probes have relied mostly on a certain type of plutonium, plutonium-238. It powers these spacecraft with the heat of its natural decay. But plutonium-238 isn't found in nature; it's a byproduct of nuclear weaponry and tough to lay hands on! Solar power is preferable to plutonium because it is cheaper and has fewer safety concerns, but obviously will not work as the craft moves away from the sun.
Fuel cells, devices that transform the chemical energy of hydrogen into electrical energy through their reaction with oxygen and feed the electricity to run an electric engine, were first employed in space missions in the 1960s. Due to their high efficiency and their water vapor emissions (no CO), hydrogen fuel cells have triggered global research efforts to reduce greenhouse gas and air pollutant emissions. But they are costly and global research at present focuses on the automobile sector.

That is all about fuel for man’s ambitious space ventures. However, a by-product of the space missions throws up energy potentials for the energy-starved earth. For instance, with space shuttles becoming as risk-free as any flight, we could think of setting up solar arrays in space.
Without the obstacles like rain, clouds and nighttime, these would receive more concentrated solar rays than they would on Earth. The panels also wouldn't be subject to the seasonal fluctuations that are unavoidable on Earth. Solar energy becomes ever present!

S
olar panels would either be attached to orbiting satellites or stationed on the moon and the electricity created would be converted into microwaves and beamed down to Earth. Rectifying antennas on the ground would collect the microwaves and convert them back into electricity. Communications satellites already do something very similar when they transmit your cell phone conversations. Some people have even suggested that the solar panels could piggyback on communications satellites. Space-based solar power is a hot favourite as all of the necessary equipment and technology is already developed and understood.

Recent proposals talk of small satellites fitted with solar arrays circling the Earth continuously. They would be more manageable than huge ones and still produce considerable energy output. A satellite less than 1,000 feet (300 meters) across orbiting 300 miles (540 kilometers) above Earth could potentially power 1,000 homes. The major obstacle right now, as with any new technology, is cost. Launching, setting up and maintaining a solar farm on the moon would require vast amounts of manpower and money.


But just as space missions were once the subject of fiction, so also any new technology will seem tough. Not impossible. And energy is what the Blue Planet needs desperately, after food and water.