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Nordic nano to propel energy efficiency

  • Published 22/03/2013
  • Author Kristin S. Grønli
Nanotechnology harbors some hope for a sustainable and efficient energy supply. Nordic teamwork delivers four promising solutions to the doorstep of commercial production.

A salt-and-paper battery. Improved fuel cells. More efficient solar cells. Surfaces that shrug off hampering ice. These are research innovations brought to a world in urgent need of energy efficient solutions for the future.

 

Unlocking the technological paths to reducing CO2-emissions and safeguarding energy supply requires more than good ideas and scientific breakthroughs. To help overcome barriers ahead of the production line, Nordic countries have gathered forces from research and development, innovation, industry and business.

 

Cutting edge nanotechnology solutions are now emerging from Energy efficiency with nanotechnology, a sub program of The Top-level Research Initiative, declared by the Nordic Prime Ministers in 2008 to help the region front the struggle to solve global climate challenges.

 

The salt-and-paper battery

Maria Strømme and her colleges at Uppsala University were coating individual cellulose fibers from green algae with polymer, for biotechnological extraction. Suddenly they realized that the coating gave the fibers a large capacity for hosting ions.

 

“The composite material had the properties of electrodes in a battery. We assembled the first battery cell with these sheets of cellulose-based nanomaterial, and a salt solution as the electrolyte. The results were published in 2009, and created rather hysterical media attention”, Strømme remembers.

 

The interest in the environmentally friendly, flexible and quickly rechargeable battery was great, but the researchers still had to bring the concept to an industrially viable stage. Through the Nordic financing initiative Strømme's research group gathered industrial and research partners.

 

Their aim is an environmentally sustainable and easily disposable battery on the market. Today, increasing amounts of energy are poured into the mining of metals like cobalt and lithium for the production of existing battery types. “Those will not do for the next generation”, says Strømme.

 

She envisions batteries in places where we can not put them today due to safety issues, like in walls or wallpaper, the casing of cars, clothing or packaging. She is also hoping to replace current types of batteries for some applications. Developing a smart grid system, for example, requires a huge amount of intermittent small and fast charge storage devices.

 

A suitable screen printing process has been developed within the project, demonstrating that mass production techniques are feasible. The cellulose production has also been scaled up. “We are now looking for a partner with years of experience tackling technical problems in battery development, to solve some typical questions related to stability and resistances, as well as finding a current collector compatible with our materials that is not based on expensive materials”, says Strømme.

 

She emphasizes how the grant from the Nordic initiative paved way for cooperation that would not have happened otherwise. “The project put us in touch with partners and communities we did not know beforehand. Joining forces also increases the chance of keeping and developing industry in the region”, she says.

 

Nano coated solid oxide fuel cells
Close collaboration with big industrial partners has been important for a project to improve solid oxide fuel cells (SOFCs), lead by researcher Jan Froitzheim at Chalmers University of Technology in Gothenburg, Sweden. One of the project's many partners is Sandvik Materials Technology, who has been able to demonstrate the project's very thin coating of steel plates on an industrial scale.

 

The researchers are developing this coating to prolong the life time of SOFCs. These fuel cells have a number of advantages over other advanced fuel cells technologies, like an unmatched fuel flexibility, which makes them suitable as bridge technology. “They can run on hydrogen, natural gas, biogas or reformatted diesel – so you don't need a new fuel infrastructure”, explains Froitzheim.

 

SOFCs are currently targeted for use in power and heat generation for homes and businesses as well as auxiliary power units for electrical systems in vehicles. The fuel flexibility is related to a high operating temperature, which is very challenging. Initially, SOFCs were built with expensive ceramics as interconnect materials. “Today the interconnect plates are almost exclusively made of steel”, says Froitzheim.

 

At temperatures from 600 to 900 degrees Celsius, the steel corrodes very fast. Additionally, evaporation of chromium from the steel will eventually destroy the fuel cell. “With nanocoatings we can reduce the evaporation by a factor of 10, and improve the corrosion resistance by a factor of 3. This will greatly increase the lifetime of the SOFCs”, Froitzheim says.

 

There are still problems ahead, but he reports being quite close to something that can be commercialized. Bringing down cost and increasing life time are main issues.“A couple of years ago this type of fuel cell was operating for around 1000 hours – now we are talking 10 000-40 000 hours. For mobile applications we need 40 000 hours, and 100 000 hours for stationary ones. We are in the lower end of where we need to be”, says Froitzheim.

 

Nanowire solar cells
Today, the cost per kWh for normal solar cells based on silicon thin-film is still higher than other competing energy sources. “We are using silicon nanowires instead, which have a much larger efficiency potential than thin-film” explains professor Helge Weman at the Norwegian University of Science and Technology (NTNU).

 

The tiny nanowires absorb and concentrate the light, so the amount of semiconductor material needed for the same efficiency is cut by a factor of 10. Grown vertically on wafers, the nanowires resemble miniscule beds of nails, and an important part of the project is to adjust parameters like the height and diameter as well as the distance between them.

 

Project partners are working on growing the wires in different ways, and Obducat, one of the industrial partners, is experimenting with nanoimprinting of masks for growth of positioned semiconductor nanowires on larger wafers for possible mass production. Nano wire solar cells is still a fairly new area of research, but has advanced very rapidly. “One of our partners at Lund University has reported an efficiency of almost 14 percent, and the research has only been going on for about 5 years” says Weman.

 

Traditional solar cells typically have an efficiency of around 20 percent. “We still have a lot left to optimize, and calculations show that we can do better than that. There are already some small companies starting up, like Sol Voltaics in our consortium,” says Weman.

 

The researchers at NTNU also have a spinoff company called CrayoNano working on growth of the nanowires on graphene. “This can make the solar cells even cheaper, because they are grown directly on an automatically thin material – not on thick semiconductor substrates. It also opens the possibility of flexible solar cells,” explains Weman.

 

Avoiding icing and frost on surfaces

Ice build-up on surfaces can cause a lot of problems, for example on airplane wings or windmill blades. Coating surfaces so they prevent ice adhesion and frost formation is a much wanted solution within the industry.

 

Agne Swerin is research director at SP Technical Research Institute of Sweden. His team is  working to solve these problems for airplane wings, heat exchangers and wind power turbines. For air planes, just a little bit of ice can be catastrophic. When ice or frost starts sticking to windmill blades, the turbine's efficiency either drops directly, or some of the energy harvested has to be spent heating the surfaces. “The ice buildup can get so severe that the turbine has to stop”, says Swerin.

 

Whereas de-icing involves heat, chemicals or other external means, anti-icing is a function of the surface itself. In the project, a number of surface solutions have been scrutinized. 10 different samples are currently mounted on a test rig atop a windmill in southern Lapland, facilitated by the project partner Vattenfall. This test is also relevant for airplane application.

 

One track in the project has been so-called superhydrophobicity, meaning extreme water repellency, which can affect ice adhesion. Frost formation is quite another problem, because frost has a different structure. “Superhydrophobic surfaces may not solve frost problems, so we work with other solutions there”, says Swerin. The researchers have come up with a molten layer that has been working in the lab so far.

 

“We are verifying the concepts. The next step is to involve industrial partners who can supply a chemistry that will work for these types of coatings,” he explains. Another important goal for the project has been to establish a Nordic platform for expertise in the area. Altogether the project has 15 participating institutions. “A professor nowadays is more like an entrepreneur involved with industry partners and spinoff companies, as well as working with students and other researchers”, says Swerin.

 

Three levels

“I fully agree,” says Anne-Christine Ritschkoff, chair of the Programme Committee. “This is the way we are heading. Fundamental research is very important, and you need to be a top scientist before your science can be used. But no less important is being able to apply the innovations and create something new from them, as well as connecting with someone who is able to make it into business.”

 

“The four projects in this sub-program are different, but they all have these three levels. They are all creating something new which can be a competitive edge for the Nordic countries,” says Ritschkoff. Finalizing the innovation processes might still take some years, but each of the project groups are producing something that is rather mature and can be exported to industry.