First of all an apology: Due to an editorial error, the last Newsletter contained an article that had been published previously, instead of a new one by the same author. I hope I have got it right this time, so here is Peter Wallis’s article ‘More Batteries’
Peter R Wallis
You may be getting bored by my articles on battery development, but a paper on “An ultrafast rechargeable aluminium-ion battery” published in Nature on 16th April 2015 deserves some attention. It has been written by a group of chemists and chemical engineers based at university departments in Stanford (USA), Changsha (China) and Taipei (Taiwan). The authors  point out that aluminium has 3-electron redox properties which lead to high capacity. Research efforts over the last 30 years encountered numerous problems, such as cathode material disintegration, low cell discharge voltage and insufficient cycle life. They now present a new battery using an aluminium metal anode and a three-dimensional graphite cathode. The battery operates by electrochemical deposition and dissolution at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, with a non-flammable ionic liquid electrolyte. The cell exhibits a well-defined discharge plateau close to 2 volts and has a specific capacity of about 70ma h per gram.
They worked at first with a pyrolitic graphite cathode but found that this limited the charging rate. In view of the importance of high-rate and high-power for applications such as grid storage, they moved to a graphite foam cathode. This achieved a remarkably high charge/discharge rate of 5 Amps per gram, some 75 times that achieved with the previous design. This would allow a charging time as low as 1 minute; the cell could also be discharged at such a rate or over an extended period. The battery cell operates at room temperature and is mechanically bendable. They drilled through one in operation and observed no safety hazard, owing to the lack of flammability of the liquid electrolyte in air.
The authors report in summary that their new Al-ion battery has a stable cycling life of up to 7,500 charge/discharge cycles without decay at high current densities. The present design offers an energy density of 40 Wh per kilogram (comparable to lead-acid and with room for improvement) and a power density up to 3kW per kg.
Readers may have seen reports in the newspapers that the Californian firm Tesla will be selling batteries this summer, based on the Lithium-ion technology used in their electric cars, to house owners to increase the efficiency of solar power which is often intermittent and unmatched to power needs. The ”Powerwall” daily cycle battery of 7 kWh capacity is estimated to cost some $3,000. Maybe we shall hear about an Al-ion alternative soon.1: Principally Meng-Chang Lin, Ming Gong, Bingan Lu and Yingpeng Wu, supported by several others. [back]
Whenever the contentious subject of ‘global warming’ is discussed, we are presented with the fact that we can watch this process actually going on by observing the melting of the Antarctic glaciers. We were warned that ultimately the melting would cause a dramatic rise in world-wide sea levels and a study by the UN’s Panel on Climate Change (2013), stated that the melting of the glaciers was causing a rise in sea level of some .27 mm annually. Recent research is casting doubt on this finding.
The Antarctic continent has been under regular surveillance by satellites from NASA and ESA since 1992 and the height of the ice sheet has been monitored by radar and laser sensors. Although it is generally accepted that the Antarctic glaciers in west Antarctica are indeed receding, new studies, reported in the Journal of Glaciology by its author Jay Zwally, indicate that in other areas, the ice sheet is thickening and moreover at a rate that exceeds the loss from the melting glaciers. Hitherto, scientists attributed gains in the Eastern ice sheet to enhanced snow fall, but using data obtained from ice cores from as long ago as 1979, the NASA team proved that the ice sheet in the area was in fact thickening.
Once again, continued research is showing that the causes and effects of enhanced ‘global warming’ may not be so sharply defined as previously thought. But at the same time, you will struggle to find this new data widely reported by the media; the exception being the Daily Telegraph (02/11/15). This is presumably because this evidence is in direct conflict with the generally accepted ‘standard model’ for a man-made enhanced global warming theory. Just last night (09/11/15) on TV news, much was being made of the fact that average global mean temperatures show a rise of 1 degree per century. The Meteorological Section of the HSS pointed this out some years ago. We have records from the same site now spanning 115 years that confirms this average temperature increase. However, we do not, as yet have any proof that this is caused by the industrial activities of mankind or due to naturally cyclic events over which we have no control or, for that matter, a combination of both.
We should also be aware of the fact that during the last half century, London’s size has greatly increased as has its population rising from about seven million in 1910 and now in excess of 8.5 million. These increases together with expanding manufacturing processes naturally produce more heat, leading to the phenomenon known as ‘the heat island effect’. This has to be taken into account when attempting to calculate an accurate mean temperature increase, particularly in the vicinity of large urban concentrations.
Assuming that the recorded rise in mean temperature of 1 degree/century is correct, then what we need to know is if this seemingly small increase is sufficient to cause all the adverse effects of enhanced global warming predicted to pose a threat to our continued existence by the purveyors of windmills. Incidentally, many of the windmills scattered around the country were forced to shut down during the recent strong winds that swept in from Atlantic storms – presumably the wrong sort of wind?
Reminder: The first lecture of the New Year will take place on Thursday January 21st when Professor Martin Elliot of Great Ormond Street Hospital will deliver his talk entitled: The Artificial Heart: A New Ending? I hope to see you at the meeting.
Last updated 27-Jan-2018