Plants Show the Way as Solar Energy Engineers


Plants made the move at the beginning: Harvesting the sun’s light to produce immense amounts of energy. And although humans are relatively new players in reaping the sun’s power instead of burning fossil fuels, scientists remain dedicated to innovative solar energy conversion. It’s virtually limitless, clean and promises to be a game changer.  

Carbon emissions remain dangerously high and climbing, and the federal government’s order for the U.S. Environmental Protection Agency to cap the release of atmospheric pollutants makes alternative energy sources all the more critical. 

In response to the crisis, scientists are now taking a lesson from nature to create an organic, solar energy system inspired by photosynthesis in plants. The research helped capture one of 46 Energy Frontier Research Centers that the U.S Department of Energy established nationwide.

Leading the multimillion dollar DOE center is Michael Wasielewski, director of Argonne National Laboratory and Northwestern University Solar Energy Research Center. His team uses artificial photosynthesis to create an organic, flexible and affordable solar energy model that can easily become part of everyday life.              

Medill News Service talked to Wasielewski, a professor of chemistry at Northwestern, about the center’s research progress as he plans to become part of yet another DOE network - the Energy Innovation Hub. 

Michael Wasielewski (Photo courtesy of Leslie Streicher)Michael Wasielewski (Photo courtesy of Leslie Streicher)What are you working on at the Energy Frontier Research Center, now part of the Argonne-Northwestern Solar Energy Research Center?   
My group works largely on artificial photosynthesis with some work on photovoltaics. The Argonne-Northwestern Solar Energy Research Center is focused on the basic science that will feed information into the Energy Innovation Hub on “Fuels from Sunlight.” The role of the Hub is to take the results from basic science research in several related fields and provide translational research which will make it possible to identify potential new technologies that can be widely implemented. The solar energy research center and the other frontier research centers will remain separate entities focused entirely on basic research.

What are organic photovoltaics?
An organic photovoltaic cell contains a layer of organic molecules (molecules that contain carbon) and/or polymers sandwiched between two electrodes made of different materials, one of which is a metal and the other is a transparent conducting metal oxide. Absorption of light by the organic material results in generation of positive and negative charges which migrate to the different electrodes. Electricity will then flow to a wire or device attached to the two electrodes.

What does this mean for developing solar energy alternatives?   
We have two main directions. First is what is called solar fuels. In other words, taking examples from nature like photosynthesis and using those concepts to generate hydrogen and fix carbon dioxide so one can generate a liquid fuel from the hydrogen/carbon dioxide combination.

The other side of the coin is to use soft materials, or organic materials, in new types of solar cells for direct electricity production. An organic photovoltaic is particularly exciting because you can mass produce solar cells very cheaply. The process can be as simple as multi-layer printing. One envisions running off tens to hundreds of meters per minute of solar cells on a printing press. Modest deficiencies and extremely low cost makes it possible to replace them on a shorter lifecycle. You could go to your local hardware store and purchase a roll of solar cells. You can roll it out, use it, and when it doesn’t work anymore go back to the local hardware store.

How does artificial photosynthesis work? 
Photosynthesis normally carried out in green plants does two things. It has a very large enzyme complex that splits water into oxygen and protons. On the other end, it’s also fixing CO2, or causing oxidation reduction. We can generate in the laboratory a lot of different molecules that closely mimic the light capture and generation of charges. The main challenge now is to integrate those systems with new catalysts. That chemical and physical interface process is really important to make an integrated system that is going to do the whole fuel cycle. 

We are also taking a lesson from nature and integrating what’s called self-assembly. In other words key components come together spontaneously, recognize each other and adopt certain orientations and distances. 

What is the next step to bring this research to a consumer market? 
Our biggest plan is to go after the Innovation Hub. The Department of Energy is trying to accelerate research by organizing an even bigger center called the Innovation Hub, which will focus on the intermediate stage between lab results and industry. We are competing to lead the center and develop it amongst a multi-institutional group of people. It’s a much bigger enterprise overall.

How long will it take to see results from all this research?
Things are moving rapidly, so that with sustained funding we should see meaningful results in 5-10 years. This whole enterprise is of real societal benefit. We are conducting fundamental research because we don’t have many of the answers to important questions, but we are also focused on the larger goal of solving the energy problem very soon.

To learn more about the Wasielewski research group's work, check out their other Science in Society features, Nature's Blueprint for Going Green and Our Solar Future.


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