EES Blog

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

Producing supercapacitors with energy densities similar to those of traditional batteries is currently a hot topic in energy research as they have great potential for use in electric vehicles. Graphene has been identified as promising supercapacitor material.

In this HOT article Ruoff et al. report for the first time the interfacial capacitance of a single sheet of graphene, and show that the greater charge can be stored on a single side of the graphene sheet than can be stored simultaneously on both sides. This means that an increase in the graphene surface area does not result in a linear increase in energy storage capacity, as was previously thought.

Read this exciting article in full:

Interfacial capacitance of single layer graphene
Meryl D. Stoller, Carl W. Magnuson, Yanwu Zhu, Shanthi Murali, Ji Won Suk, Richard Piner and Rodney S. Ruoff
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE02322E

An exciting article in Energy and Environmental Science has been highlighted in this week’s Editor’s Choice in Science. The article by Teixeira et al. describes their studies into the way cellulose behaves at high temperatures.

You can read the article on our website:

Aerosol generation by reactive boiling ejection of molten cellulose
Andrew R. Teixeira, Kyle G. Mooney, Jacob S. Kruger, C. Luke Williams, Wieslaw J. Suszynski, Lanny D. Schmidt, David P. Schmidt and Paul J. Dauenhauer
Energy Environ. Sci., 2011
DOI: 10.1039/C1EE01876K

Or why not look at our EES blog post about this exciting work.

Scientists are looking into the safety of lithium ion batteries so that they can be used to power large devices such as cars or power grids.

Lithium ions are OK for use in small devices, such as laptops and phones, but there is a risk of fire if they need to power devices with higher energies.

Scientists from France have used a fire calorimeter – a device recognised by US and EU regulating bodies – to get an insight into the fire behaviour of these batteries.

The apparatus provides online analysis of mass loss and combustion gas production (O2, CO, CO2, hydrogen halides, HCN, NOx, SOx, aldehydes, THC). From these data, the rate of heat release, heat of combustion and the mass of burnt products from the combustion tests could be deduced. The data could help in fire simulation tests, say the researchers. They add that the identification and quantification of toxic emissions from combustion gases can be estimated.

As a result, the data could play a part in improving the safety of batteries, they conclude.

Read the Energy & Environmental Science paper today:

Investigation on the Fire-Induced Hazards of Li-ion Battery Cells by Fire Calorimetry
P Ribiere, S Grugeon, M Morcrette, S Boyanov, S Laruelle and G Marlair
Energy Environ. Sci., 2011, DOI: 10.1039/c1ee02218k

An energy scavenger device that can convert both solar energy and movement energy into electricity to power portable electronics has been made by scientists from Korea and the US. The device could find its way into your home in the future as it’s flexible enough to be attached to clothes, bags, curtains or flags, say the researchers.

Sang-Woo Kim from Sungkyunkwan University in Suwon and colleagues made the device from piezoelectric zinc oxide and an organic solar cell so that electrical energy can be provided either by sunlight or wind or body movement, depending on which source is available at the time.

It’s been believed that solar energy is sufficient for powering portable electronics because it has a high efficiency, but many mobile electronics are operated indoors in areas with dim lighting. In such cases, the power that can be harvested drops by two to three orders of magnitude, say the researchers, and harvesting energy from other sources becomes viable. 

The device can be incorporated into flags to harvest both movement and solar energy

So far, attempts to make multi-type energy devices have been plagued by cross-talk problems, in which energy transfer between adjacent conductors occurs, causing a drop in efficiency. Kim’s device gets around this problem. The team made a cathode from an indium tin oxide coated polymer. They coated this with a layer of zinc oxide nanorods – the parts that are activated by movement. Another polymer layer – the part that’s activated by light – was added between the nanorods. The rods have a dual role because they also transport electrons generated by the solar cell.

In tests, the device gave outputs of tens of millivolts to 120 millivolts when using solar energy and tens of millivolts to 150 millivolts when using piezoelectric energy.

‘Materials chemistry can provide integrated solutions to energy harvesting and regeneration via new developments, especially in the area of smart and multifunctional systems. This work presents one such development via the fusion of photovoltaic and piezoelectric hybrid materials,’ says Elias Siores, an expert in piezoelectric materials from the University of Bolton, UK. ‘Such systems will pave the way forward in enhancing effectiveness and efficiency in energy conversion systems.’

Elinor Richards

Read the paper from Energy & Environmental Science:

Control of naturally coupled piezoelectric and photovoltaic properties for multi-type energy scavengers
Dukhyun Choi, Keun Young Lee, Mi-Jin Jin, Soo-Ghang Ihn, Sungyoung Yun, Xavier Bulliard, Woong Choi, Sang Yoon Lee, Sang-Woo Kim, Jae-Young Choi, Jong Min Kim and Zhong Lin Wang
Energy Environ. Sci., 2011
DOI: 10.1039/c1ee02080c