“Scientists seek to make energy as plants do”

[jody]

Scientists seek to make energy as plants do

For example, Tom Mallouk, a professor of chemistry and physics at Pennsylvania State University in University Park, has built an experimental device that uses light to launch a daisy-chain of tiny molecules that pass electrons - the particles that carry electrical energy - from one to another. When the electrons reach the end of the chain, they take part in a chemical process that generates hydrogen, which can be stored for use later as a fuel, he explained.

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Another researcher, Song Jin, a chemist at the University of Wisconsin, in Madison, is experimenting with nanometer-scale wires instead of clusters of molecules to convert solar energy (light) into chemical energy (fuel).

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Yet another preliminary technique is being tested by an international team of scientists, headed by Leone Spiccia of Monash University in Victoria, Australia, and Charles Dismukes at Princeton University in New Jersey. They use a molecular cluster containing atoms of manganese, a chemical used in plant photosynthesis to help break water molecules apart into hydrogen and oxygen.

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Practical artificial-photosynthetic systems are at least 10 years away, Mallouk said. There are many technical problems to be solved to equal the efficiency of nature's way.

[HereSince1628]

1. Strange infinitive in that title for a journal promoting physical science.

[BlooInBloo]

2. All alternative energy production sources are interesting....

But scalability and efficiency are the 2 questions any such candidate source must answer to be taken seriously.

It appears that photosynthetic efficiency is around 3%-6% - not good.

[drm604]

3. Plants don't "make energy".

They absorb it from sunlight and convert it into chemical reactions.

[phantom power]

4. Photosynthesis is 3% to 6% efficient. Setting the bar pretty low.

Approximately 114 kilocalories of free energy are stored in plant biomass for every mole of CO2 fixed during photosynthesis. Solar radiation striking the earth on an annual basis is equivalent to 178,000 terawatts, i.e. 15,000 times that of current global energy consumption. Although photosynthetic energy capture is estimated to be ten times that of global annual energy consumption, only a small part of this solar radiation is used for photosynthesis. Approximately two thirds of the net global photosynthetic productivity worldwide is of terrestrial origin, while the remainder is produced mainly by phytoplankton (microalgae) in the oceans which cover approximately 70% of the total surface area of the earth. Since biomass originates from plant and algal photosynthesis, both terrestrial plants and microalgae are appropriate targets for scientific studies relevant to biomass energy production.

Any analysis of biomass energy production must consider the potential efficiency of the processes involved. Although photosynthesis is fundamental to the conversion of solar radiation into stored biomass energy, its theoretically achievable efficiency is limited both by the limited wavelength range applicable to photosynthesis, and the quantum requirements of the photosynthetic process. Only light within the wavelength range of 400 to 700 nm (photosynthetically active radiation, PAR) can be utilized by plants, effectively allowing only 45 % of total solar energy to be utilized for photosynthesis. Furthermore, fixation of one CO2 molecule during photosynthesis, necessitates a quantum requirement of ten (or more), which results in a maximum utilization of only 25% of the PAR absorbed by the photosynthetic system. On the basis of these limitations, the theoretical maximum efficiency of solar energy conversion is approximately 11%. In practice, however, the magnitude of photosynthetic efficiency observed in the field, is further decreased by factors such as poor absorption of sunlight due to its reflection, respiration requirements of photosynthesis and the need for optimal solar radiation levels. The net result being an overall photosynthetic efficiency of between 3 and 6% of total solar radiation.

http://www.fao.org/docrep/w7241e/w7241e05.htm

[NNadir]

6. Don't worry. Nature has plenty of "breakthroughs" planned.

Solar breakthroughs are happening at an ever accelerating rate, and we now have as many brazillion breakthroughs as we have solar roofs in California.

[pscot]

7. Nature has time on its side

Efficiency matters only to short-lived creatures like ourselves.

[The2ndWheel]

5. Nature is pretty inefficient

Which is a good thing. That's why diversity exists.

[XemaSab]

8. Daisy chain

:P