Friday, March 29, 2013

Farewell to colleagues

 
 

There was a terrible helicopter accident on Thursday 21 March 2013 at Bulli Tops, just south of Sydney.  The four people who lost their lives were John Dunlop, 66, Tony Farmer, 68, Gerry Haddad, 71 and Don Price, 67.  I knew them all and had a special friendship with Don.  I write this post to honour their memory.

I worked for CSIRO Australia, the national applied research laboratory, for nearly 25 years in two stints.  In the 1980s, I was located at the National Measurement Laboratory in suburban Lindfield in Sydney and it was there that I got to know the four, all of them physicists on site.  I eventually moved to another CSIRO site in 1992 and we drifted apart somewhat, although we continued to catch up occasionally.  By 2013, all four had recently retired after distinguished careers.  All leave behind loving wives, partners and families, to whom I send heartfelt condolences.

I shared many things in common with all four, especially our love for science and how it should be applied to make the world a better place. 

During the 1980s I was an enthusiastic distance runner, as was Don, and we trained together almost every lunchtime for about six years.  John was another member of the regular running group.  With Tony and Don I shared a passion for squash, a popular game at the time, and we played friendly matches together on many occasions.  With Gerry I shared participation in a CSIRO Research Leadership course and I recall many animated discussions (furious agreement really!) on any number of topics.

What do I miss especially about these friends?

Don’s considerable talents might not have been obvious to all at first because of his modesty, but he had a huge work ethic, a steely determination, an understated sense of humour and was absolutely reliable in all aspects of his life.  In addition to his scientific achievements, he was an accomplished amateur sportsman, especially in squash and running where he completed many marathons and had a best time under 2 hours 40 minutes.

I remember John’s sharp intelligence and dry wit as we would dissect the latest CSIRO management disasters on our lunchtime runs, Tony’s friendly greetings in the interminable corridors of the National Measurement Laboratory, and Gerry’s desire, eventually fulfilled, for a senior management role in CSIRO.  All were dedicated professionals, the sort of admirable colleagues you knew you could rely on through the ups and downs of a career in a government research organisation.

So, I’m grieving for all four.  The happy memories I have are a comfort to me, but the coming week will be a tough one for everyone who knew them, with multiple funerals to attend.

I especially extend my deepest sympathies to the loved ones all four have left behind.  Their loss is great.

 

 

Thursday, March 7, 2013

Pebble bed paper accepted

The Editor of Applied Thermal Engineering this week accepted for publication my paper on pebble bed heat storage simulations.  Even at my age, now 64, I still get a buzz from the acceptance of a paper, so I thought I’d share the news here.

The title and abstract are as follows:

Simulations of air-blown thermal storage in a rock bed

This paper presents computer simulations of air-blown thermal storage in a loosely packed bed of rocks.  An important application is storage of solar thermal energy for power generation or process heating.  A new formulation is developed for one-dimensional flow of air through the rock bed, including the variation of density with temperature.  The model equations are solved numerically and results given for the effect of important parameters such as particle size, depth of bed and air flow-rate.  It is shown to be useful for the rock bed to be charged with downwards airflow and discharged with upwards airflow. This schedule is always superior – sometimes significantly so – to a schedule in which the bed is charged and discharged in the same (upwards) direction.

I began to think about these simulations in mid-2011 when I realised that thermal storage in pebble beds would be a good fit with my evaporation engine.  I designed and coded the simulation algorithm in early 2012.  In one part of the paper I compare my simulations with those of Hänchen et al. (2011) whose work also includes experimental validations.  Those comparisons show that results from my code match well with experimental results.  That’s always pleasing!

I then go on to look at the importance of molecular diffusion inside individual pebbles.  For pebbles up to about 50 mm in diameter, you might as well just assume the pebbles heat up or cool down uniformly.  Full molecular diffusion gives slightly more accurate results, but the extra accuracy hardly justifies the extra computation that is required.

Another topic I studied is the sharpness of the front between hot and cold zones in the bed.  The front becomes sharper as the particle diameter decreases. 

Yet another topic is the efficacy of charging and discharging through bi-directional (2-way) and uni-directional (1-way) strategies.  In the 2-way strategy, the bed is charged with downwards airflow and discharged with upwards airflow.  In the 1-way strategy, the airflow is always upwards.  Representative results can be viewed at www.sunoba.com.au (follow the link to “Thermal storage simulations” on the right-hand side).  My conclusion here is that the 2-way strategy is always to be preferred, even if it requires extra plumbing and ducting of the pebble bed.

The last section of my paper looks at two sorts of losses.  For large beds, thermal losses from insulated beds are generally very small, typically of the order of 1% of the total useful heat content over a 24 hour period.  I also show that the parasitic loss associated with pumping air through the pebble bed is acceptable for the sort of practical application I have in mind.

Since writing the paper, I have used the simulation code to investigate how pebble bed storage could be used in conjunction with my evaporation engine.    This is the abstract for the conference paper that resulted (Barton, 2012):

A simulation study is presented for air-blown thermal storage in a solar thermal power station powered by passive heat collection under a transparent insulated canopy.  The principal objective of this study is to investigate the round-trip efficiency of thermal storage in a pebble bed.  In the proposed system, heat energy is converted to power by a new heat engine based on evaporative cooling of hot air at reduced pressure.

The work examines the performance of the canopy/engine/storage system over representative days each month for a full year.  The useful heat reclaimed from the storage system is typically about 95% of the useful heat input, less small additional losses at the walls and ducts of the storage system.  Because the heat reclaimed has a smoother daily temperature distribution than the heat gathered by the canopy, there is another 5% penalty in conversion of heat into power.  For the configuration used in this study, the power output using storage is 88% of what would be obtained without storage.  This estimate includes modest losses due to pumping and heat transfer at walls and ducts.  Coarse economic evaluations indicate that storage would reduce the Levelised Cost of Electricity by 27% and increase the Capacity Factor of the engine by 88%.

Conclusion

I’m enthusiastic about the prospects for pebble bed thermal storage.  The pebble bed simulation code will be useful for various applications including dispatchable solar thermal power generation and provision of process heat in domestic and industrial applications.  The next application to be studied will be to my BRRIMS (Brayton-cycle, Re-heated, Recuperated, Integrated, Modular, Storage-equipped) concept for solar thermal power generation.

References

N.G. Barton, “Passive Solar Power Generation with Air-blown Thermal Storage”, Solar2012, Australian Solar Council, Melbourne (2012).

M. Hänchen, S. Brückner, A. Steinfeld, “High-temperature thermal storage using a packed bed of rocks – heat transfer analysis and experimental validation”, Applied Thermal Engineering, 31 (2011) 1798-1806.

Sunday, March 3, 2013

Climate change infographic


Just over nine years ago, I resigned my senior job at CSIRO Australia, the national applied research laboratory.  I had spent nearly 30 years as an academic and government researcher in industrial and applied mathematics, and I’d decided that the rest of my productive life would be as an inventor in renewable energy and related fields.  That led to an interesting journey, which still continues.

Most of those nine years have focussed on new ideas for solar thermal power such as BRRIMS.  There have also been investigations of dryers and dehumidifiers and desalination, the latter topic being so secret that I have never described my work in publications or on the internet.

My passion still burns fiercely – I think we are making the world worse, not better, and I want contribute to an improvement.  I am deeply concerned about excessive consumption of resources, especially energy, and the damage this causes to our spaceship home, Planet Earth.  Above all, there is the terrible prospect of long-term climate change that in a worst case might leave the planet uninhabitable for humans.  See here and here for my further comments on these issues.

It’s always a pleasure to meet others holding similar views to mine, especially when they have a different set of competencies, a scientifically honest standpoint, and are willing to promote their views for all to see.

This blog post then is a tribute to the authors of the handful of blogs I read every day.

In the field of climate change, I only read four blogs:

www.skepticalscience.com is, quite simply, astounding.  If my memory serves me well, it was founded by a school teacher who wanted to rebut denialist views of his father.  Or was it the father-in-law?  Whatever, it is now an immensely valuable resource in which up-to-date climate science is presented daily in a very readable way. 

www.realclimate.org is at a higher level.  It’s written by the people who publish in the best journals in the field.  The blog posts aren’t all that frequent, but what appears is of extremely high quality.

www.tamino.wordpress.com is a blog written by “tamino”, nom de plume of a US-based statistician.  He is razor sharp and blogs frequently.  He can be counted on for a lacerating debunking of denialist posts, often within hours of them appearing.

www.moyhu.blogspot.com is written by my former CSIRO colleague Nick Stokes.  A natural genius, Stokes will always find a new way to look at big problems such as climate change and then pursue in-depth practical implementations.

I also follow two blogs concerned with oil and fossil fuel energy:

www.theoildrum.com is a big blog with numerous contributors.  Most of the postings are written by engineers in the fossil fuel industry.  Typical posts deal with technicalities, such as how much oil remains, who is producing what, and what are the major issues that need to be confronted.  The blog is refreshingly free from commercial hype, and I read it to know better the devil that must not be fully exploited.

www.peakoil.net deals with similar issues to The Oil Drum, but is less frequent and has more of scholarly standpoint.

That’s the long and short of the blogs I read.  On some days there is enough reading for 30-45 minutes, on other days I skim the contents in 5-10 minutes.  My daily reading also includes the mainstream media and various e-magazines, but I won’t discuss them here.

I was inspired to write this blog post because I recently had an approach from Allison Lee, who I assume is a young person based in the USA.  She had found my blog and asked if I’d comment on some infographics that she had prepared.  The topic – why it’s climate change of course!  I like the way she assembles relevant information and provides it in a palatable way for a younger audience such as 10-18 year olds at school, or for young adults with similar educational levels.

You can check out Allison’s infographic here.  It might be a useful link for your children or grandchildren.