The renewable solution right in our faces

The location and timing of this year's World Future Energy Summit, which opens in Abu Dhabi tomorrow, could hardly be better. For the thousands of energy experts attending, the UAE is renowned - despite having among the highest per capita energy consumption in the world - for being a world leader in its commitment to sustainable energy sources. As for timing, 2011 also looks set to be a key year in perceptions of renewable energy technologies.

The UAE is in the fortunate position of having the solution to its own challenges staring it in the face every day. The sun provides more energy in just one hour than the entire world uses in a year, and few regions of the world are better placed to exploit solar energy than the Emirates.

Mention solar energy to most people, and chances are they will think of vast fields of black photovoltaic cells or "PVs". Since their emergence during the 1960s as the principal means of powering satellites, PVs have dominated the solar energy market. When searching for the main power source for Masdar City, the flagship sustainable energy development of Abu Dhabi, planners focused on PVs. A 10MW plant already powers the construction effort at Masdar, and this will be followed by a 100MW PV plant as the city nears completion.

Yet after years of incremental improvements, the science of turning sunlight into electricity is undergoing a revolution. And at its core are attempts to mimic one of the key processes that sustains life itself: photosynthesis.

As taught in school biology lessons, photosynthesis may seem an unlikely power source. It's usually portrayed as simply the means by which plants convert carbon dioxide and water into nutrient in the form of carbohydrate, producing oxygen as "waste". Yet to bring about this transformation, plants use the energy of sunlight to extract electrons from water molecules. And if electrons are freed to move from one place to another, the result can be turned into an electric current.

It took life on Earth several hundred million years to evolve the means of harnessing sunlight to release electrons. Even now plants don't do it especially well: the efficiency of photosynthesis is only around 5 per cent. Small wonder, then, that scientists have found it difficult to make the process at least twice as efficient to make it competitive with PVs .

Leading the charge has been Professor Michael Gratzel of the Swiss Federal Institute of Technology, Lausanne. Last year, his work on turning photosynthesis into a source of energy won him one of the world's most prestigious awards, the $1 million (Dh3.7 million) Millennium Technology Prize, whose past winners include Tim Berners-Lee, inventor of the World Wide Web.

The accolade reflects Prof Gratzel's invention of the so-called dye-sensitised cell (DSC), often called simply the Gratzel cell. During the 1970s he and his colleagues focused simply on trying to combine chlorophyll, the sunlight-absorbing green dye in plants, with a more efficient means of generating electricity. To do it, they used titanium oxide, a cheap compound used in paint which also has a silicon-like ability to conduct electrons. The results were, however, disappointing, with cells converting barely 0.01 per cent of the original solar energy into electricity.

By the late 1980s, Prof Gratzel and his colleagues had abandoned chlorophyll in favour of a more effective dye, combining it with new forms of titanium oxide. The result was a hundred-fold improvement in conversion efficiency. Since then, Gratzel and others around the world have been working steadily towards a commercially viable form of DSC capable of mass production. Conversion efficiencies are now above 10 per cent, while raw material and manufacturing costs are much lower than conventional PV-based solar cells. DSCs can also be coloured or even transparent, so they can be used as an energy-generating replacements for windows.

But the advantages of DSCs don't stop there; they also have a plant-like ability to cope with dull, overcast skies and indoor light - unlike conventional PV cells which need intense sunlight to work well.

All this means that DSCs have the potential to make solar cells a viable source of energy in those countries that lack reliable, intense sunlight. Test sites and prototypes are already up and running, and both governments and private companies are investing in production plants.

The revolution isn't quite there yet, however, as some practical problems remain. Chief among them is the use of the liquid electrolyte needed to turn the cells into a power source; this is tricky to manufacture in bulk, and also tends to degrade over time. Efforts to tackle these shortcomings are now well advanced, with researchers led by Dr Henry Snaith at the University of Oxford, UK, having developed solid electrolytes which are both easier to make and less subject to degradation. Mass-production of these solid state DSCs is likely to begin in the next few years.

Thus, before long solar cells are likely to be a common sight both indoors and out in countries where sunshine is far less reliable than it is in the UAE. And the migration of the technology cannot come too soon, given the recent problems that have hit the major competitor to solar cells in the renewable power field: wind energy.

Critics have long claimed that in many regions of the world, the wind is simply too fickle to be relied on. These criticisms have come to the fore over the last few weeks, following bouts of bitterly cold weather in northern Europe. The cause was a large area of high pressure that dominated the region's weather - and also reduced wind speeds to virtually zero. In the UK, the contribution of wind power to total energy supply plummeted just when demand reached its peak.

Fortunately, conventional energy sources like fossil fuel plants were able to make up the difference. Yet with the EU committed to getting an average of 20 per cent of its energy from renewable sources - principally wind - by 2020, there are concerns about longer cold snaps producing power cuts. Last month, 10 European nations bordering the North Sea signed an agreement to construct a pan-national "grid" linking together power networks across the continent, which should help boost reliability. Yet concern remains that in the search for clean alternatives to fossil fuels, too much emphasis is being put on wind power.

Many of those attending this week's summit will be looking for ways to diversify their energy supplies over the coming years, and looking to Masdar City for inspiration. Those arriving from gloomier climes will doubtless feel envious of the plethora of energy options available in the UAE.

Robert Matthews is a visiting reader in science at Aston University, Birmingham, England