SYMBIOS
eco-tecture + design + build
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Greening Buildings: Goodbye Carbon - The authors from the Institution of Mechanical Engineers (UK) say that without geo-engineering it will be impossible to avoid dangerous climate change.
A recent report highlighted the most promising geo-engineering methods to “decarbonise” the atmosphere and employing buildings as a means to capture carbon ranked in the top three most viable methods.
Although the team studied hundreds of different options, they have put forward just three as being practical and feasible using current technology. A key factor in choosing the three was that they should be low-carbon technologies rather than adding to the problem.
Integrated “algae based photo bioreactors” on building facades could play an enormous role in sucking up carbon. The photo bioreactors would be transparent containers containing algae, which would remove carbon dioxide from the air by using incoming sunlight and conducting photosynthesis, absorbing carbon and producing oxygen.
Modern day urban environments could provide millions upon millions of square feet of potential surface area for attachment of photo bioreactor units onto or integrated into the buildings external envelope or ‘skin’. Algae units could be designed into new buildings or retrofitted onto existing buildings as well. There may even be secondary uses of harvesting the algae in order to producing bio-fuels or as an organic soil fertilizer.
Given the legacy of the built environment as being one of the great villains of our ecological crisis it would quite redeeming that in the near future that buildings may play a heroic role.
Source - BBC Science and Environmental News Agency.
Nanoengineered coating to improve solar panels
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.
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.
Lin’s new coating also successfully tackles the tricky challenge of angles.
Most surfaces and coatings are designed to absorb light — i.e., be antireflective — and transmit light — i.e., allow the light to pass through it — from a specific range of angles. Eyeglass lenses, for example, will absorb and transmit quite a bit of light from a light source directly in front of them, but those same lenses would absorb and transmit considerably less light if the light source were off to the side or on the wearer’s periphery.
Lin’s discovery could antiquate these automated solar arrays, as his antireflective coating absorbs sunlight evenly and equally from all angles. This means that a stationary solar panel treated with the coating would absorb 96.21 percent of sunlight no matter the position of the sun in the sky. So along with significantly better absorption of sunlight, Lin’s discovery could also enable a new generation of stationary, more cost-efficient solar arrays. Lin said the new coating could be affixed to nearly any photovoltaic materials for use in solar cells, including III-V multi-junction and cadmium telluride.
Typical antireflective coatings are engineered to transmit light of one particular wavelength. Lin’s new coating stacks seven of these layers, one on top of the other, in such a way that each layer enhances the antireflective properties of the layer below it. These additional layers also help to “bend” the flow of sunlight to an angle that augments the coating’s antireflective properties. This means that each layer not only transmits sunlight, it also helps to capture any light that may have otherwise been reflected off of the layers below it.
Source: Rensselaer Polytechnic Institute “Realization of a Near Perfect Antireflection Coating for Silicon Solar Energy,” published this week by the journal Optics Letters.