Athanasios Mermigkas’s report

IEEE Pulsed Power and Plasma Science conference in California — June 2013

Athanasios at the conference

I am currently a 3rd year PhD student at the University of Strathclyde in Glasgow. My PhD research is focused on the development of an impulsive micro-electrostatic precipitation technology (?-ESP) for increasing the efficiency of removal of sub-micron particles for small-scale air-cleaning applications. This technology is based on utilizing short plasma impulses and dc voltage in order to charge and remove particles in an efficient way. Shorter impulses allow higher voltages to be applied, which is expected to increase the precipitation efficiency and to reduce power losses. The potential benefits from implementation of the micro-electrostatic precipitation technology in small-scale indoor environments such as homes, schools and hospitals are considerable, passively improving the health of people who use it by acting to eliminate the inhalation of large amounts of PM2.5.

To put the research into context, let me explain a few things about the actual problem, which is in the interest of the Simon Wolff Charitable Foundation (SWCF). Various industrial, agricultural and domestic operations, as well as developing nano-technologies, produce particles of micron and sub-micron sizes. While larges particles tend to settle quickly after their release, smaller ones tend to stay longer in the air, thus increasing their spatial dispersal. According to a recent report “Road transport was responsible for around a quarter of primary PM2.5 emissions in the UK in 2008 (NAEI, 2010), with diesel vehicles accounting for a much higher proportion than petrol.” To make matters worse, small enough particles have the ability to migrate deep into the respiratory system, and exposure of the public to high concentration has been linked to respiratory diseases and increased mortality rates. This is not something new, as there was concern among scientists even many years ago about such risks, one of them being Dr Simon P. Wolff, who forewarned the unsuspecting community that “the switch to diesel which is now taking place may well be a large-scale experiment in lung cancer” and of the danger of transport fumes in general. It may be argued that transport-emitted particle concentrations decline rapidly away from the roads; however, most people nowadays live and work in urban environments, meaning that roads will be close to human activities, residential or commercial. Thus, such particles require monitoring and control.

While electrostatic precipitation is a fairly old application, the voltage management regimes enabled by power electronics has made it possible to use electrostatic precipitators in much more efficient ways. The use of impulses is one way to reduce power consumption compared to DC energisation, and is also very effective when the resistivity of the particles collected is high. Electrostatic precipitators are mainly used in power plants and factories to clean flue gases and exhausts. This means that much research has been conducted on negative-polarity energisation, which is more efficient for larger-scale applications (like electrostatic filters in power plants). However, this type of discharge produces ozone and nitrogen oxides which must be avoided for indoor applications. Thus, positive polarity was used in my research which produces much less ozone and nitrogen oxides (about 10% to that of negative polarity). Apart from the polarity, it was also decided to use impulses of much shorter duration (nanoseconds or 10s of microseconds), despite the fact that longer impulses are usually used in industrial precipitators, in order to further reduce the power losses and be able to have higher electric fields that further charge the particulate matter.

To these ends, various topologies have been tested (single-stage and double-stage cylindrical reactors) as well as different particle sources, like the ones already present in the ambient laboratory air; cigarette smoke; beeswax candle smoke; and various dusts, in order to investigate the effects of different energisation combinations on particles with different size distribution, resistivity and permittivity.

Last month, the generous donation of the SWCF helped me to attend the IEEE Pulsed Power and Plasma Science conference. As you can see, I was fortunate that this year the pulsed power conference, where I submitted my abstract to, was combined with the plasma science conference. This expanded the topics to be presented, adding also very interesting plasma applications into the schedule. However, this also meant that the conference had many parallel sessions running for 5 days, with one plenary session each morning and 6 parallel sessions both mornings and afternoons. As a consequence, frequently decisions had to be made on which presentations to attend and not a few times silent steps have been taken out of a lecture room, just to rush to another one in time during the sessions! According to the conference program, there were more than 1000 submitted abstracts representing 43 different countries.

The first International Pulsed Power conference took place in 1976, and since 1979 the conference is held biennially under the sponsorship of the IEEE (Institute of Electrical and Electronics Engineers). It is the principal forum for communicating advances in the areas of pulsed power science, technology, new systems and emerging applications. Additionally, the authors are invited to submit their extended papers for publication in the IEEE Transactions of Plasma Science which is a peer reviewed journal. Thus, this conference leads to a first step towards an all-important journal publication, an opportunity that I’m not intending to miss.

IEEE is the largest association of electronic and electrical engineers, but also includes other scientists, even medical doctors. Its aim is to advance innovation and technological excellence for the benefit of humanity. It is thus no wonder that it hosts more than 300 conferences annually and publishes 130 journals, transactions and magazines on various scientific topics.

On the very first morning of the conference, I was assigned to do an oral presentation on my work titled “The Use of Impulsive Corona Discharges for the Removal of Fine Particles in a Novel Coaxial Electrostatic Precipitator”. This afforded me the opportunity to contact renowned scientists, researchers and industrial engineers present from a variety of backgrounds, due to the diverse topics in the combined conference schedule. This was also an opportunity to get wider feedback in areas adjacent to my research, like a comparison of my results with similar attempts in the industry or particle modeling in the view of their charging mechanisms. Moreover, the paper also highlighted the key findings of two years of my research project, in addition to the results with a new, larger-scale precipitator, thus giving the delegates a chance to see the course taken throughout my PhD and give constructive feedback.

The fact that I had an oral presentation at the international level, with such a varied audience with wide fields of interest and expertise asking diverse questions, not only raised my awareness in view of my PhD defense, by pointing to aspects not known or not investigated yet, but also granted me invaluable presentation experience in an international panel of academics and industrialists.

The EEE (Electronic and Electrical Engineering) department of the University of Strathclyde was represented by my first supervisor, Dr I.V. Timoshkin, the Dean of Engineering, Prof Scott J. MacGregor, and 2 students. The EEE department contributed 3 oral presentations, 3 posters and also a plenary session by Prof MacGregor highlighting the key research activities, past and present, of the High Voltage Technologies (HVT) research group, which I am also part of. This talk, as well as the 3 oral presentations and posters, helped to promote the international profile of the University of Strathclyde, by making visible to the global research community its research aims and achievements, and also by strengthening the links with other research institutes which had its members present in the conference.

Since the conference had such a wide range of topics, it was imperative to choose among the so many interesting subjects presented. Some that were mostly related to my research were the Environmental and industrial applications, including contaminant destruction like NOx; the Basic plasma phenomena and the partially-ionized plasmas, as the plasma generated in my reactor plays a crucial role in particle charging; medical biological and environmental applications including ozone production (in my case it is imperative to have as low O3 as possible); and compact pulsed power and power supplies, needed for energisation of the reactor. Presentations included diverse and exotic subjects as “Growth control of leaf vegetables using pulsed electric field” and algae growth enhancement having possible applications for biofuel industry.

It was also very beneficial that in the conference hall there were presentation stands of leading industrial companies that manufacture pulsed power equipment and pulsed power diagnostic systems. This gave young academic participants like myself a rare opportunity to speak directly to the companies’ representatives, see some of the products that they have available and even to witness a live demonstration of a high voltage pulsed power system, which expanded my knowledge of the state-of-the-art pulsed power equipment available on the market which potentially can be used in my future research work. According to the general chair there were 30 exhibitors from industry and academia presenting their technical wares and products. Additionally, there was an organized job opportunity center, with announcement board and people to contact with. One could also find representatives from the companies / universities / research labs that had job / placement adverts placed on the board at the conference, which was very useful especially for the final-year students!

San Francisco lies in the west coast of the US having a climate similar to the one found in the Mediterranean countries. Despite the busy conference schedule, I had the chance to visit the Golden Gate Bridge, the Chinatown, which used to be one of the biggest in the world, and the environs of the city. The beauty of the town, Victorian style houses, modern skyscrapers and the landscape are breathtaking. Unfortunately, I did not have the chance to visit Alcatraz island, since staying for extra days in San Francisco in the summer proved to be very expensive….so, till next time!

I would like to thank the Simon Wolff Charitable Foundation once more for awarding me the invaluable grant in order to present my research at this renowned international conference, especially now that I am in the final stages of my PhD. I’m really honored at being selected for the travel grant and hope that the Foundation can continue its essential support for young researchers, especially now that many other sources of funding are unavailable.

Athanasios Mermigkas