Wednesday, February 24, 2010

Revolutionary Energy Solutions: Bloom Energy


CBS 60 Minutes has reported this week about Bloom Energy a new Silicon Valley startup that has come up with a revolutionary solid oxide fuel cell (SOFC) technology to convert natural gas into electricity. Bloom cofounder and CEO K.R. Sridhar uses mediator inks which are simply painted onto ceramic plates. The ceramic plate with a mediator ink for natural gas on one side and a different mediator ink for oxygen on the other are sandwiched between grooved metal plates which allow the flow of gas and oxygen to enter the system and which conduct the electricity away.

The most revolutionary thing about the BloomBox is first that it's already working. Companies like EBay, Walmart, and Google have installed BloomBoxs and are currently producing high amounts of electricity. In the report, a representative of Google shows how his crop of BloomBoxes are producing much more electricity then their expansive system of solar panels. Google estimates that their Bloom Boxes are producing 15% of all their electricity.

Other revolutionary aspect of this technology is that it has the potential to make the US energy independent. While the US doesn't have much petroleum, what we do have is plenty of natural gas. And the Bloom Box is perfect in converting natural gas into electricity with twice the efficiency compared to burning it. Bloom is hopeful that small fuel cell stacks the side of a toaster inside a dishwasher-size unit would be enough to power an average US home. The cost for the entire unit would be about $3000. Larger units the size used by Amazon, Google, and Ebay would power entire neighborhoods. This technology is going to be the next "game changer" like the Internet.

The Bloom Box has some issues with air filters getting clogged, but this is an easy fix. SOFCs historically can be poisoned by sulfur but the Bloom Box stacks are so cheap to produce, I think they could be replaced easily. Natural Gas has almost no sulfur in it compared to petroleum so, I foresee the units lasting for a long time and being very low maintenance. The boxes need to run at hotter temperatures to avoid needing platinum for the oxygen side. This temperature requirement could be used to heat homes which would increase efficiency.

The bi-product of the reaction is carbon dioxide. So, when run on natural gas, critics complain that the BloomBox is not carbon neutral unless it is run by landfill gas or something similar. But, again, all the ice core data proves that there is no such thing as man-made global warming. Global warming and cooling is directly related to solar luminosity, solar cycles, and Milankiovitch cycles which describe variations in the tilt of the Earth and variations in Earth orbit around the sun. Ice core data shows that throughout history rising CO2 levels lag 800 years behind rising temperatures, proving that higher temperatures heat the oceans and result in higher atmospheric CO2 and not the other way around.


Science Daily reported last week about a new technology in thin-film flexible solar cells. Harry Atwater, Nathan Lewis, Michael Kelzenberg at Caltech published the results of their new solar array on February 14 in Nature Materials. Their solar cell uses an array of vertically arranged micron-sized silicon wires to absorb sunlight. These silicon wires are embedded in a flexible transparent polymer which is impregnated with reflective light scattering particles. The rods themselves are coated with an anti-reflective coating. The result is over a 85% efficiency in collecting collectible solar energy which is then converted into electricity. Currently, the best thin-film solar cells have only about a 15%-20% efficiency. The efficiency recorded for the more traditional crystalline silicon solar cells using multi-junction concentrator technology is only 40%.

The advantage of this technology is that it is flexible, avoids the cost and difficulty associated with pure crystalline silicon, and claims to be more efficient than other thin film technologies (First Solar, Nano Solar, Uni-Solar). Using micro-silicon wire arrays uses just 1/50th of the silicon and can be produced in a cheap roll-to-roll manufacturing process. However, I am a little fuzzy about their claim of efficiency. They claim 85% of collectible light is converted to electricity, but I am not sure how that compares to traditional solar panel efficiency. Photons coming from the sun have an energy between 1.5-3 eV according to E=hv. Solar panels using muti-junctional concentration or different layers that absorb at different wavelengths generate electrons of 0.7-1.8 eV at 40% efficiency. I am not sure if the Caltech efficiency is talking about the same thing as solar cell efficiency as described in the following graph. However, I think the micro-rods/wire array concept is great. This idea reminds me of the rods and cones in the retina of the eye. Also, I wonder if multi-junctional concentration could also incorporated?

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