EES Blog

HOT EES communication

The recombination of charges before they reach the electrode in a solar cell has been identified as one of the key reasons for a loss of efficiency in these systems. Tracey Clarke and coworkers have developed a new switch-based time resolved technique for studying the recombination process. This allowed the researchers to overcome the resistance-dependence limitations of typical time-of-flight experiments.

Read the full HOT EES communication:

Non-Langevin bimolecular recombination in a silole-based polymer:PCBM solar cell measured by time-resolved charge extraction and resistance-dependent time-of-flight techniques
Tracey M. Clarke, Jeff Peet, Patrick Denk, Gilles Dennler, Christoph Lungenschmied and Attila J. Mozer
DOI: 10.1039/C1EE02434E

Platinum has been the electrode material of choice for the oxygen reduction reaction which takes place in fuel cells. However it is expensive, and previous research using alloys of Pt with Co, Ni and Fe have required high Pt ratios.

Now researchers working at the Brookhaven National Laboratory have synthesized nanoparticles with a carbon-supported IrNi core and a surface monolayer of platinum. These nano-electocatalysts have an approximately 3 times higher Pt mass activity than currently available commercial Pt/C electrocatalysts.

Read the full details of this HOT EES paper:

Bimetallic IrNi core platinum monolayer shell electrocatalysts for the oxygen reduction reaction
Kurian A. Kuttiyiel, Kotaro Sasaki, YongMan Choi, Dong Su, Ping Liu and Radoslav R. Adzic
DOI: 10.1039/C1EE02067F

Scientists in the US have taken the first steps towards designing a flexible and lightweight fabric that can act as a power supply for smart garments.

Electronic textiles, or ‘smart’ textiles, are fabrics that have built-in functions such as sensing, data storage and communication. But as with all electronics, they require a power source. Conventional batteries are too bulky to wear, so a power source that can be combined and integrated into the garment is highly desirable.

Previous attempts to make wearable energy storage devices involved the use of nonwoven materials not usually used in clothes and expensive active materials like carbon nanotubes and nanowires.

Yury Gogotsi and colleagues at Drexel University, Philadelphia, have taken everyday fabrics like woven cotton and polyester materials and impregnated them with porous carbon powders, taking advantage of the natural porous nature of these materials. Using common techniques like screen printing, ink-jet printing and dip-coating, textile electrodes can be made on a large scale without the expense of new processes needing to be designed.

A battery can be integrated into a garment by impregnating woven cotton and polyester fabrics with porous carbon

‘Our work makes a significant advancement in this area as our electrodes can store 400-700 times the energy per area of previously reported literature while also being flexible, non-toxic and has great potential to be integrated into textiles and clothing,’  says Gogotsi.   

The woven and knitted fabrics have empty space between individual fibres and between yarns, and it is into these spaces that the carbon powders are inserted, allowing ion transfer. The team were able to achieve higher mass loadings and capacitance levels on comparison with previous techniques.  

‘The relatively simple approach to engender conductivity to textile substrates has broad impact,’ comments Tushar Ghosh, a specialist in textile engineering from North Carolina State University, US. ‘The work contributes to the body of knowledge necessary for energy harvesting and storage in textiles of the future.’   

Although more work is needed to get a finished product, the hope is to develop this technology into a number of smart garment devices that can be used in a variety of fields such as healthcare, the army and even aerospace exploration. 

Rebecca Brodie   

Read the paper from Energy & Environmental Science:

Carbon coated textiles for flexible energy storage
Kristy Jost, Carlos R. Perez, John K. McDonough, Volker Presser, Min Heon, Genevieve Dion and Yury Gogotsi
Energy Environ. Sci., 2011
DOI: 10.1039/c1ee02421c

A miniature biofuel cell can generate electricity using the sugars in grapes, according to researchers in Japan.

The device has a needle bioanode that can be inserted into the grape, and a gas diffusion biocathode that uses oxygen in the air to oxidise the sugars. The maximum power produced was 26.5µW at 0.34V, which was used to power a light emitting diode (LED), which indicated the level of sugar in the grape.

The device could be used in the same way to test blood sugar levels (a test was done by inserting the needle into an animal vein) to monitor health.

Read this exciting EES paper now:

Enzymatic biofuel cells designed for direct power generation from biofluids in living organisms
T Miyake, K Haneda, N Nagai, Y Yatagawa, H Onami, S Yoshino, T Abe and M Nishizawa,
Energy Environ. Sci., 2011
DOI: 10.1039/c1ee02200h

Researchers in the US and Canada simulated solar radiation management (SRM), a form of geo-engineering that involves reflecting sunlight to reduce global warming.

Suggested approaches are to increase the amount of light-scattering stratospheric aerosols or increase the reflectivity of low-altitude marine clouds. The idea has attracted renewed interest but there are enormous uncertainties about the risks and effectiveness of SRM.

 The team used a HadCM3L programme for the simulations and came to the conclusion that solar geo-engineering could be tested to reduce uncertainty about climate response, but tests would require decades of modulated climate forcing.

 Read the EES article today hot off the press!

Can we test geoengineering?
D G MacMynowski, D W Keith, K Caldeira and H-J Shin,
Energy Environ. Sci., 2011
DOI: 10.1039/c1ee01256h

Marta Hatzell, Younggy Kim and Bruce Logan at work in the lab. Photograph by Robert Davis

Microbial fuel cells (MFCs) are a potential “green” energy source of the future, using organic matter in water to produce electricity. However, the voltages obtained from MFCs are generally too small to be useful.

Now Bruce Logan and his co-workers at Penn State University have shown that MFC voltages can be increased while maintaining continuous power production.

They introduced two sets of capacitors that are alternately charged and discharged into their circuit. The capacitors were charged in parallel by the MFCs, but linked in series while discharging thus preventing a phenomenon known as voltage reversal which can cause an overall decrease  in the voltage achieved. Impressively, the system also had negligible energy losses compared to those reported up to now.

Read the full details of this HOT EES paper:

Capturing power at higher voltages from arrays of microbial fuel cells without voltage reversal
Younggy Kim, Marta C. Hatzell, Adam J. Hutchinson and Bruce E. Logan
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE02451E

Scientists are attempting to reduce the costs of harnessing the sun’s energy by creating ceramic tiles that can perform photovoltaic action, so-called “solar tiles” that can be used to tile roofs.

Hugo Aguas, Rodrigo Martins and their research group at Universidade NOVA de Lisboa and UNINOVA have successfully fabricated solar tiles and demonstrated market viability with a cost estimation.

Their new solar tiles were able to achieve a 5% conversion efficiency and 80% quantum efficiency.

Read the EES article today:

Silicon thin film solar cells on commercial tiles
H Aguas, S K Ram, A Araujo, D Gaspar, A Vicente, S A Filonovich, E Fortunato, R Martins and I Ferreira
Energy Environ. Sci., 2011, DOI: 10.1039/c1ee02303a