science technology

The plant power plant

I generally don’t get very excited about technology, but every once in a while I read a technology article that captures my imagination. That happened twice this week, so I thought I’d share them.

The first was li-fi – transmitting data using light bulbs. Because LEDs can switch on and off faster than the human eye can perceive them, they can be used to stream data through what appears to be a regular beam of light. Which means that one day you might be able to access the internet through the lightbulb above your head. In theory. Here’s the Wired article about it, and here’s inventor Harald Haas demonstrating it at TED (of course).

The second one is to do with light too, and involves plants. All plants are solar powered, converting sunlight into energy through photosynthesis. For all our research into solar power, we’ve never come up with anything as simple and efficient as what plants do in their cells. Our photovoltaics require rare earth metals and sophisticated technology. But what if we could just use the plants themselves?

The New Scientist explores this idea here. Apparently you can hammer a nail into a tree and get a tiny trickle of electric current, but not in amounts that could ever be useful. Underground however, chemical processes in the soil offer another opportunity to generate electricity. Plant roots release organic materials such as carbohydrates into the soil, and micro-organisms then break them down. In the right anaerobic conditions, this microscopic deconstruction results in free electrons that can can be harvested by electrodes, making it possible to create microbial fuel cells.

The long and short of it is that there is a lab in the Netherlands that can generate enough power to charge a mobile phone from a square of marsh grass growing on the roof.

Needless to say it’s early days, but the scientists working on it have only been on the case for five years or so. With the right plants, soil composition and technology, they estimate that they can achieve 3.2 W/m2. (Solar farms get 7.7) It’ll never be enough to run the world, but it’s much more efficient than biofuels. Besides, there are plenty of advantages to green roofs. Why not add energy generation to the list of benefits too, and make them a mainstream option? And is there any way to harvest electricity from crops growing for food anyway? A team in Japan has been testing the energy generating possibilities of rice paddies.

I don’t suppose we’ll see either of those technologies anytime soon, but we can let our imaginations run a little from time to time. It is friday after all.


  1. I’m being neglectfully unspecific – the 7.7 figure is from solar farms, where there are of course gaps between panels, and they used that figure to compare it to growing crops. Domestic solar only measures the coverage of the panels themselves and does much better. Thanks for pointing it out.

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