Turning every home into a power station

Claire O'Connelltalks to a scientist whose recent discovery may make it possible to store energy from renewable sources in our homes

HERE'S THE answer to the global energy crisis: the power of one. No, not the home-grown campaign that encourages you to turn off lights and wash laundry at 30 degrees.

No, this is the power of one as outlined by US chemist Prof Daniel Nocera, an advocate of "personalised energy" who is currently in Ireland to speak at a major scientific conference.

His vision turns your house into a power station, reaping renewable energy from the sun or wind, converting it to electricity and then - rather than feeding it back to a communal power grid - stores it in your basement so that you can use it at your leisure.

It is an elegant solution to the rather cumbersome problem of new energy users starting to power up in their billions on to an already struggling system, as Prof Nocera explains: "We have three billion people who aren't born yet and we have three billion non-energy users - mostly in China, Africa and India - so that's six billion non-energy users in the next 50 years," he says.

"You can attack this top-down with a big grid-based infrastructure like in America, a century-old idea where we do everybody a billion at a time. Or we go with a new wave idea, to attack six billion people one at a time by giving them individual power. It's modular, so wipe out the carbon dioxide problem by going after them one at a time, six billion people with an energy system that's cheap, personalised energy."

Much in the way PCs took over from mainframe computing in the 1980s, he reckons personalised energy can beat down the old-fashioned grid with its voracious appetite for fossil fuels. "It's the power of one times six billion, that's how you are going to end up solving this energy problem," says the Henry Dreyfus professor of energy at the Massachusetts Institute of Technology in Boston.

But to hit that target of each person, family or company generating and storing their own environmentally-friendly power supply we have to address a nagging problem with renewable energy sources - their variability. "What happens when the sun goes down? You are out of energy. Now think about your life and think you can only live when the sun is shining. That's not how we built our society," he says.

"If I had to choose one word to describe what's stopping renewables from being implemented, to explain the most important issue, I would say storage. Without storage you are never going to implement renewables on a large scale."

But now there's a possible solution to that chestnut. Enter Prof Nocera's discovery, unveiled earlier this year, of a catalyst that can use the electricity generated by wind or sun to split water and release hydrogen, which can in turn be stored in a fuel cell.

The reaction mimics the first phase of photosynthesis, the biochemical process by which green leaves harness energy from the sun. Prof Nocera's artificial "leaf in a beaker" uses a cobalt-based inorganic catalyst that can split water to release hydrogen and oxygen with surprising efficiency at room temperature.

So how does splitting water fit into solving the world's energy problems? In his home-power-station scenario, the photovoltaic solar panel on your roof or the wind turbine in your garden generates electricity and feeds it to the cobalt catalyst in a small tank of water in your house. When enough energy gets on board, the catalyst splits water molecules and the resulting hydrogen atoms are spirited off to a nearby fuel cell, where energy is stored and drawn on later as needed.

The self-contained energy system could potentially even be used in a car, where an on-board catalyst draws energy from the alternator to split water and fuel-inject hydrogen into the engine to improve combustion, he says.

It is straightforward, and this is why he believes it will work: "I think at the end of the day for technology it has to be simple. It's always the simplest things that end up being successful."

But what about efficiency? How much energy leaks out through all these transitions in the system? And what about safety when you are dealing with a combustible agent like hydrogen in the basement of a house? "The efficiency of the catalyst itself is really good but that doesn't mean I am home free, because I have all these other issues, and these need to be ultimately assessed if you want to make an energy system," says Prof Nocera, who is linking up with industry in the search for answers.

When he announced details of his cobalt catalyst at a conference in Edinburgh last June, he was initially met with an enthusiastic response. "Everybody there was excited, people hadn't been able to split water to hydrogen and oxygen under normal conditions like leaves do it," he says. "That's the new part of the discovery: I got the leaf in the beaker and my discovery opens a door or pathway to personalised energy."

Then came the backlash. "It's natural, people think about their experience and they say it's going to be too expensive, you need all these other system components on board."

But again Prof Nocera is trying to turn current thinking on its head by encouraging people to think less about efficiency and more about cost, a particular barrier in developing countries.

"Here's the big problem in energy: everybody's always designing to efficiency, and this can get really expensive. Alternatively, if I can give up something in efficiency, meaning I don't do it as fast - but I have all day when the sun is out to do this - I do it just well enough to take care of energy storage at night. Now let me design to cost, which is different than designing to efficiency."

But, to his surprise, he is finding that often people have not even bothered to do the sums for cost-efficient systems. "Hardly anyone has done those equations, and I'm talking some of the biggest energy companies in the world. People haven't even thought about that; it's always efficiency, efficiency, efficiency," he says.

"But the bottom line is to store enough energy for a person for one day. You don't need as much energy as you think you need. It's a lot less. For storing the water I only need to be dealing with between four and eight litres a day. There's that much energy in water once you break the bond. So all of a sudden the answers start looking different in terms of costs, and that's what we are doing now."

The leaf-in-a-beaker catalyst works well in the lab, but how long before consumers can start living the good life around the clock on power they generate themselves?

"This has got to be done in under five years," says Prof Nocera, who is setting up partnerships with energy, engineering and distribution firms around the world. "If you think about how quickly China and India are growing, I would like to give myself five years to figure out what's the cheapest energy solution we can have for this personalised energy problem, not this grand-scale energy problem, I mean one person at a time, and actually fuelling distribution. If I don't do it, I am going to feel like I have failed. It has to be done this quickly."

• Prof Daniel Nocera will address the Science Foundation Ireland summit on "Convergent Worlds" today and tomorrow at Lyrath Estate in Kilkenny