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Inconvenient Truths About 'Renewable' Energy

Inconvenient Truths About 'Renewable' Energy →

Matt Ridley makes a few good points, I think.

It turns out that the great majority of this energy, 10.2% out of the 13.8% share, comes from biomass, mainly wood (often transformed into charcoal) and dung. Most of the rest is hydro; less than 0.5% of the world's energy comes from wind, tide, wave, solar and geothermal put together. Wood and dung are indeed renewable, in the sense that they reappear as fast as you use them. Or do they? It depends on how fast you use them.

One of the greatest threats to rain forests is the cutting of wood for fuel by impoverished people. Haiti meets about 60% of its energy needs with charcoal produced from forests. Even bakeries, laundries, sugar refineries and rum distilleries run on the stuff. Full marks to renewable Haiti, the harbinger of a sustainable future! Or maybe not: Haiti has felled 98% of its tree cover and counting; it's an ecological disaster compared with its fossil-fuel burning neighbor, the Dominican Republic, whose forest cover is 41% and stable. Haitians are now burning tree roots to make charcoal.

You can likewise question the green and clean credentials of other renewables. The wind may never stop blowing, but the wind industry depends on steel, concrete and rare-earth metals (for the turbine magnets), none of which are renewable. Wind generates 0.2% of the world's energy at present. Assuming that energy needs double in coming decades, we would have to build 100 times as many wind farms as we have today just to get to a paltry 10% from wind. We'd run out of non-renewable places to put them.

This entry was tagged. Solar Power

Increasing Solar Efficiency

Researches keep moving along with solar power advancements. The latest advancement is a new antireflective coating that allows solar panels to absorb more sunlight.

Researchers at Rensselaer Polytechnic Institute have discovered and demonstrated a new method for overcoming two major hurdles facing solar energy. By developing a new antireflective coating that boosts the amount of sunlight captured by solar panels and allows those panels to absorb the entire solar spectrum from nearly any angle, the research team has moved academia and industry closer to realizing high-efficiency, cost-effective solar power.

"To get maximum efficiency when converting solar power into electricity, you want a solar panel that can absorb nearly every single photon of light, regardless of the sun's position in the sky," said Shawn-Yu Lin, professor of physics at Rensselaer and a member of the university's Future Chips Constellation, who led the research project. "Our new antireflective coating makes this possible."

... An untreated silicon solar cell only absorbs 67.4 percent of sunlight shone upon it -- meaning that nearly one-third of that sunlight is reflected away and thus unharvestable. From an economic and efficiency perspective, this unharvested light is wasted potential and a major barrier hampering the proliferation and widespread adoption of solar power.

After a silicon surface was treated with Lin's new nanoengineered reflective coating, however, the material absorbed 96.21 percent of sunlight shone upon it -- meaning that only 3.79 percent of the sunlight was reflected and unharvested. This huge gain in absorption was consistent across the entire spectrum of sunlight, from UV to visible light and infrared, and moves solar power a significant step forward toward economic viability.

That's exciting stuff. Of course, there's a while to go yet before we have solar panels on our houses. The comments on the original article point out some of the remaining issues. For instance, this new coating requires 7 new layers on top of the solar cell. How expensive are these layers? Does the additional energy offset the additional manufacturing cost? What about converting that extra sunlight into electricity? The sunlight isn't necessarily converted into electricity just because it's absorbed by the panel. What about conversion efficiency? Existing panels convert sunlight to electricity at around 30% efficiency. New panels with this coating will collect more light but still convert it with ridiculously low efficiency.

To have a viable solar infrastructure we need panels that can absorb nearly 100% of the incoming sunlight, convert nearly 100% of the incoming sunlight, and convert the sunlight with much better efficiency. More than that, the final panels need to be relatively cheap or no one will be able to buy and use them. We're not there yet. But we are getting closer. And I look forward to the day that I can power a significant portion of my home's energy needs with solar energy.

This entry was tagged. Energy Solar Power

Power from Space

Space Solar Power is a fascinating idea. It involves putting satellites into space, covered with solar panels. These satellites would catch the energy from the sun -- undiluted by atmosphere or night -- and beam it down to earth. The idea has been around since the 1960's, but has yet to actually become feasible.

Still, recent studies have indicated it might be possible to do this economically in the near future.

A special study group of the National Research Council (NRC) has taken a new look at NASA's current SSP efforts. Their findings are in the NRC report: Laying the Foundation for Space Solar Power - An Assessment of NASA's Space Solar Power Investment Strategy.

While not advocating or discouraging SSP, the advisory team said "it recognizes that significant changes have occurred since 1979 that might make it worthwhile for the United States to invest in either SSP or its component technologies." The study urges a sharper look at perceived and/or actual environmental and health risks that SSP might involve.

The NRC study group singled out several technological advances relevant to SSP:

  • Improvements have been seen in efficiency of solar cells and production of lightweight, solar-cell laden panels;
  • Wireless power transmission tests on Earth is progressing, specifically in Japan and Canada;
  • Robotics, viewed as essential to SSP on-orbit assembly, has shown substantial improvements in manipulators, machine vision systems, hand-eye coordination, task planning, and reasoning; and
  • Advanced composites are in wider use, and digital control systems are now state of the art - both developments useful in building an SSP.

Now it appears that the Pentagon is interested in doing some trials as early as 2015.

"A first demonstrator project in, say, the year 2015 might power a military base, be capable of sending power to disaster areas, or transmit energy to troops abroad. The cost of petroleum fuel, not only money but lives lost in wars fought over oil, is a big driver of the Pentagon’s interest in space solar power. [Col. M.V. Smith] has gone from skeptic to enthusiast since the study began. ..."

Sounds good to me.

This entry was tagged. Solar Power

More Efficient Solar Cells

Silicon nanoparticles enhance performance of solar cells

Placing a film of silicon nanoparticles onto a silicon solar cell can boost power, reduce heat and prolong the cell's life, researchers now report.

To make their improved solar cells, the researchers began by first converting bulk silicon into discrete, nano-sized particles using a patented process they developed. Depending on their size, the nanoparticles will fluoresce in distinct colors.

Nanoparticles of the desired size were then dispersed in isopropyl alcohol and dispensed onto the face of the solar cell. As the alcohol evaporated, a film of closely packed nanoparticles was left firmly fastened to the solar cell.

Solar cells coated with a film of 1 nanometer, blue luminescent particles showed a power enhancement of about 60 percent in the ultraviolet range of the spectrum, but less than 3 percent in the visible range, the researchers report.

The process of coating solar cells with silicon nanoparticles could be easily incorporated into the manufacturing process with little additional cost, Nayfeh said.