Nanotechnology has become a much-discussed subject of late, but its full potential has yet to be realized, not least in the power sector. Matt Harris of FEI Company, a nanotechnology research company, looks at the importance of nanoscale science in the energy sector.

Matt Harris, FEI Company, USA

The UK Government’s Energy Review of 2006, which declared a long-term sustainable approach to supplying the UK’s power supply, devoted just two of its 218 pages to the importance of innovative new technologies. Looking ahead, those formulating our policies should not underestimate the ways in which nanoscale science is already influencing how we manage energy. As our ability to meet the rising energy demands using traditional methods declines, we must consider the important role nanotechnology can play in the production, storage, conservation and delivery of energy. Historically, countries such as the UK and USA have relied on their own fossil fuel resources, but they will have to increasingly depend on imports in the future.

There are two courses to pursue when addressing this deficit – the development of inexpensive and Earth-friendly alternative fuel sources, and the use of existing fuels. Nanotechnology research and the resulting commercialization has a fundamental role to play.

Carbon nanotubes conduct electricity over greater distances than copper wires and could allow cities to be connected to distant wind farms
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Nanotechnology involves characterizing and analyzing materials and structures below 100 nm. At this scale, familiar materials begin to develop unusual properties because this is where the behaviour of matter is determined. Nanoscience – the discipline that aims to explore and discover the basic blocks of our universe – has been researched for decades, but the first wave of real nanotechnologies is just beginning to emerge and they look impressive.

Power sources

The Pacific Northwest National Laboratory (PNNL) in the USA is already using nanotechnology to develop materials that can store solid hydrogen and in turn reduce our reliance on carbon-based fuels. Hydrogen is abundant in our atmosphere and has more energy per unit of mass than any known substance. Although the concept of a hydrogen economy has been circulating for many years, there are technical barriers to its wide-scale adoption – the greatest being storage.

In its gaseous state, hydrogen’s energy content is low. The challenge for storage is to maximize the energy available, while ensuring it can be easily processed to generate power. Atom by atom manipulation means solid hydrogen can be stored in nanoscale pores that are built into PNNL’s new material. At this scale, the hydrogen retains its solid state and can easily be transported. The material can then be broken down, releasing the hydrogen.

Nanotechnology is also helping wind power take off. There are 1672 operational wind turbines in the UK, delivering 1833 MW of power each year. That number must rise to 40 000 MW before 2010 to meet targets set by the European Union directive on renewable energy. But the problem of reliability still exists, which has raised concerns among the investment and insurance communities.

Wind turbines are huge, rotating objects operating in wet conditions. They accumulate rain and seawater, which freeze to form ice, increasing the weight, drag and force required to move the fibreglass blades. Turbine efficiency can drop by as much as ten per cent under these conditions.

New coatings, at the atomic level, can help blades repel water. The Degussa Corporation in Germany has used electron microscopes to replicate the water repellent surfaces of plant leaves. Degussa manufactures these as a thin film covered with nanoscale wax crystals, which causes water to quickly bead. This can be applied to turbine blades to make water run off before it can freeze.

Sunny side up

Another example is the development of cheaper solar panels to encourage more people to invest in them.

Solar power became popular in the 1970s, but fell out of favour due to fluctuations in savings over fossil fuels. Nanotechnology is now helping to reduce the cost of producing these panels by removing the need to build them from silicon.

Thin films of new photovoltaic substances just one nm thick can generate as much electricity as a 200-300 nm thick silicon wafer and can be manufactured at a lower cost. One company, California-based Nanosolar has begun development of the world’s largest photovoltaic (PV) manufacturing facility, in what could be the beginning of the first truly mass produced solar technology. Nanosolar is offering a solar cell manufacturing technology that is all solution-based and does not require expensive vacuum systems.

Thin-film PV panels 1 nm thick can generate as much electricity as a 300 nm silicon wafer
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The 430 MW thin-film plant is being constructed in the San Francisco area and will produce around 200 million solar cells per year. According to Nanosolar, the use of thin-film printing technology, and the scale of the proposed facility, will allow it to produce PV at a fraction of the cost of conventional producers.

Chris Eberspacher, Nanosolar’s head of technology said: “Thin-film printing overcomes the complexity, high cost, yield and scalability limitations associated with vacuum-based processes. It enables low-cost, high-yield production previously unattainable.”

Nanosolar is building a new production plant in Germany, producing 200 million nanotechnology solar cells per year – enough to power 400 000 homes. The company claims a silicon-based factory of the same capacity would cost an additional $900 million to build. Nanosolar hopes the factory, located near Berlin, to be in volume by the second half of this year.

Grids of the future

Future electricity grids could also be built using nanoscale science. Carbon nanotubes – tiny tubes of carbon grown for their strength and lightweight properties- are better conductors of electricity than traditional copper wires. They can carry over a billion amps of current per square centimetre and lose very little energy as heat. In theory, they could transport electricity thousands of miles.

With the ability to conduct electricity over such long distances, cities could use energy generated by giant solar farms in deserts or by wind farms off coastal shores rather than relying on local coal, gas or nuclear power plants.

Upping the ante

Nanoscale science is also facilitating a better understanding of the properties of different fuels, so that we can manipulate them to deliver energy more efficiently. The materials science department at the University of Cambridge, UK, is developing nanotechnology that could reduce the UK’s electricity consumption by 16 per cent by bringing white light emitting diodes (LEDs) into our homes and offices. Ninety-five per cent of the energy used in traditional lighting is wasted in the form of heat, but LEDs are up to ten times more efficient because they do not require heat to produce light.

White LEDs, widely used in torches and on bike lights, produce a light too harsh for human eyes. The university is using electron microscopes to cover LEDs with nanoparticles of phosphors – substances that emit different colours when subjected to white light. When these are used in a particular combination on a white LED they produce natural light suitable for homes and offices.

Fuel efficiency

The UK’s Stagecoach Group is already using nanotechnology to increase the fuel efficiency of its coaches and buses. Oxonica, a small company based in Oxford, UK, has developed a fuel additive that use nanoscale particles called Envirox. Made for diesel fuel, the particles coat the inner workings of the engine and remove all carbon deposits during the combustion process.

Envirox delivers fuel economy by two separate mechanisms. Cerium oxide is a redox catalyst that helps to promote the optimum amount of reactive oxygen within the combustion chamber, leading to a more complete and cleaner burn and increased power. In addition the material significantly lowers the temperature at which carbon deposits in the engine are burnt off allowing the potential to restore and retain the engine as close as possible to its original design state.

Envirox has been extensively tested both in the laboratory and under commercial operating conditions in long-term trials. In a trial in Hong Kong, Envirox demonstrated a significant statistically tested fuel economy benefit as high as 11.4 per cent. The trial comprised 80 vehicles, 40 with Volvo engines and 40 with Cummins engines.

Of these, 20 were allocated to the additised group and 20 to the control group. All of the vehicles were approximately seven years old at the start of the trial and all routes were city operation. The trial lasted six months and data were collected for a further two months after the dosing ended.

The data from the Hong Kong trial were analyzed by an independent statistician. The additive had a progressive effect on fuel economy. However, the full effects could only be seen after six-to-eight weeks. This trial period was therefore disregarded when measuring the fuel economy benefits.

A fuel economy benefit of 11.4 per cent for the additised Cummins group, compared to the control Cummins group, was observed after six months of use. Similarly, a fuel economy benefit of 9.9 per cent was observed for the additised Volvo group.

Nanotechnology is here now

We have looked at just some of the ways in which viewing and manipulating material at the nanoscale can influence how we manage our energy supply and demand. There are a finite number of energy sources on the planet, but there are measurable ways to improve our use of them.

By viewing substances atom by atom we will understand how best to exploit their traits and develop new materials and products to support our drive for a cleaner, more energy-efficient world. This is not a discipline for future generations to exploit. If we continue to label nanotechnology as a science for the next century we are likely to overlook its immediate advantages. Nanotechnology must not be relegated to the realms of fantasy, it is a reality which can help us in the here and now.