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Fri Jan 18, 2013, 12:27 PM

Photovoltaics Beat Biofuels at Converting Sun’s Energy to Miles Driven

http://www.bren.ucsb.edu/news/geyer_pv_biofuels.htm
Photovoltaics Beat Biofuels at Converting Sun’s Energy to Miles Driven

New study shows solar power is not only better in terms of energy efficiency, land use, and greenhouse gas emissions – but is cost competitive, too

January 16, 2013

In 2005, President George W. Bush and American corn farmers saw corn ethanol as a promising fossil fuel substitute that would reduce both American dependence on foreign oil and greenhouse gas emissions. Accordingly, the 2005 energy bill mandated that 4 billion gallons of renewable fuel be added to the gasoline supply in 2006. That rose to 4.7 billion gallons in 2007 and 7.5 billion in 2012.

Since then, life cycle assessments (LCAs) have shown that corn ethanol has a modest effect, if any, on reducing CO2 emissions and may actually increase them, while posing a threat to natural habitats and food supplies, as food stocks are turned to fuel and marginal lands are put under the plough to keep up with demand. In 2010, fuel ethanol consumed 40 percent of U.S. corn production, and 2012 prices are at record highs. Since the U.S. also accounts for 40 percent of the world’s corn, U.S. ethanol production has affected corn prices around the planet.

As electric vehicles (EVs) increasingly enter the market and charging stations are built to serve them, EVs are competing with alternative-fuel vehicles. Using electricity generated by coal-fired plants to power the cars defeats the purpose to some extent, but what if the energy comes from the ultimate clean and renewable source – the sun itself? How would that compete with ethanol in terms of land use, life-cycle emissions, and even cost?



The results, which appear in a paper titled “Spatially Explicit Life Cycle Assessment of Sun-to-Wheels Transportation Pathways in the U.S.” and published in the Dec. 26 issue of the journal Environmental Science & Technology, showed photovoltaics (PV) to be much more efficient than biomass at turning sunlight into energy to fuel a car.

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Reply Photovoltaics Beat Biofuels at Converting Sun’s Energy to Miles Driven (Original post)
OKIsItJustMe Jan 2013 OP
hedgehog Jan 2013 #1
rightsideout Jan 2013 #2
Jackpine Radical Jan 2013 #3
NoOneMan Jan 2013 #4
OKIsItJustMe Jan 2013 #5

Response to OKIsItJustMe (Original post)

Fri Jan 18, 2013, 12:31 PM

1. Nice to know since there is limit to how much bio fuel we can make -

I heard a report yesterday that European governments are pulling financial support from bio fuels because of the limits.

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Response to OKIsItJustMe (Original post)

Fri Jan 18, 2013, 12:32 PM

2. Like this . . .

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Response to OKIsItJustMe (Original post)

Fri Jan 18, 2013, 12:32 PM

3. Corn ethanol never was a good bet.

On the other hand, some oils derived from cold-expressing might have considerable potential.

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Response to OKIsItJustMe (Original post)

Fri Jan 18, 2013, 01:02 PM

4. Maybe we can finally let this bad idea rest in peace

 

Though, algae may have the potential to change the equation.

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Response to NoOneMan (Reply #4)

Fri Jan 18, 2013, 06:16 PM

5. I don’t think algae have the potential to change the equation

My reasoning goes like this. Living organisms are optimized to produce the energy they need to live, not to produce excess energy for us to use.

We can “tweak” their genes to try to get them to produce more “excess” energy, but at a fundamental level, they use photosynthesis to live.

One might argue a similar situation exists with a PV panel, in that some energy is used creating, installing and maintaining the PV panel. However, I think you’ll find that the ratios are quite different.

(Please note, US Government publication, copyright concerns are nil.)
http://www.nrel.gov/news/features/feature_detail.cfm/feature_id=1512
Algae Research in Full Bloom at NREL

November 3, 2010

In a test tube, vibrant green microalgae look fragile, but in reality getting them to spill their lipid secrets to make renewable fuels is a challenge — one that researchers at the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory are tackling, again.

From 1978 to 1996, DOE funded NREL's study of microalgae under the Aquatic Species Program. During that time, 3,000 algae strains were isolated from various aquatic habitats. Roughly 50 caught the attention of researchers for their potential use in producing transportation fuels.

Then in 1996, the price of oil bottomed out at roughly $20 a barrel. The estimated cost of algae oil at the time was about $80 a barrel. With those price factors and other budget pressures, DOE stopped funding the Aquatic Species Program. Algae strains were sent to the University of Hawaii for safekeeping and the NREL team summarized nearly 20 years of research in the program's Close Out Report (PDF).

Algae Comes Back into the Race

Fast forward 10 years and the Energy Independence and Security Act of 2007 (EISA) is passed by Congress. The 2007 law required that the U.S. produce and use 36 billion gallons of renewable fuels by 2022. EISA capped the use of starch based ethanol at 15 billion gallons and called for the remainder to be made up by "advanced biofuels"— basically anything else.



"Algae has a lot of potential, and NREL has been doing a good job of not subscribing to all of the hype," Darzins said. "We have been a credible advisor to DOE, industry and the general research community. Our message has been that for algal biofuels the potential is huge — it could be a game changer. But, the challenges are equally as daunting — and boy, have we got our work cut out for us."



It seems to me that NREL is pursuing algae today, well, because they are required to.


I think the “challenges” identified in the “Close Out Report” are still daunting, e.g.

http://www.nrel.gov/docs/legosti/fy98/24190.pdf


IV.A.2.b. Maximum Efficiency of Photosynthesis

Many environmental factors affect the performance of the complex photosynthetic machinery in microalgae, reducing its efficiency to well below the maximum at which photosynthesis can perform. That maximum is dictated by the underlying mechanisms, biophysical constraints, and physiological adaptations. One objective of applied microalgal R&D would be to develop strains and techniques that achieve productivities as close as possible to the maximum.

However, somewhat surprisingly, there is still argument about the maximum limit for photosynthetic efficiencies. The arguments boil down to the mechanisms assumed and the many possible loss factors that may or may not be considered. Most researchers agree that an absolute minimum of eight quanta (photons) of light absorbed are required by the two-photosystem mechanism (Z-scheme) of photosynthesis to reduce one molecule of CO2 (and closer to 10 to 12 quanta if the energy needs for CO2 fixation and cell metabolism are considered). However, there have been many reports of higher efficiencies. For example, recently Greenbaum et al. (1995) reported that some algal mutants lacking one photosystem still fixed CO2 (and produced H2), suggesting less than 8 (and as few as 4) quanta per CO2 reduced. However, recent reports cast doubts on this interpretation, and the two-photosystem mechanism appears robust.

The maximum efficiency can be estimated at about 10% of total solar (Bolton 1996). Such efficiencies have been used in the projections for microalgae biodiesel production (see Section III.D.). However, high sunlight conversions are observed only at low light intensities. Under full sunlight, typically one-third or less of this maximal efficiency, biomass productivity is obtained, because of the light saturation effect.

Light saturation is simply the fact that algae, like many plants, can use efficiently rather low levels of light, typically only 10% of full sunlight (and often even less). Above this level, light is wasted. In fact, full sunlight intensities can damage the photosynthetic apparatus, a phenomenon known as photoinhibition. Light saturation and photoinhibition result from several hundred chlorophyll molecules collaborating in light trapping, an arrangement ideally suited for dense algal cultures, where on average a cell receives little light. However, exposed to full sunlight, the photosynthetic apparatus cannot keep up with the high photon flux and most of the photons are wasted, as heat and fluorescence, and can damage the photosynthetic apparatus in the process. One possibility, suggested by Neidhardt et al. (1998), is that photosynthetic productivity and light utilization could be maximized in microalgae by reducing the size of the light-harvesting antenna through mutation or genetic engineering. This is an interesting idea that will be discussed further in the next section.

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