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Geosequestration

Sequestration of CO2: underground; below the seabed; in depleted oil or gas reservoirs; or in deep saline aquifers is technically possible. But the scale required, to sequester just 25% of NSW coal sourced CO2 (for example that produced by coal fired electricity), is an enormous engineering challenge.  It is one thing to land a man on the Moon; it is another to relocate the Great Pyramid (of Cheops) there.

Most current work is directed to finding appropriate deep leak proof geological strata below land for the purpose. Undersea sequestration would be an engineering challenge on an even greater scale, and potentially very damaging to ocean organisms coral reefs and fisheries.

Not only is CO2 over twice the weight of the coal used to generate it; but the volume (after being compressed to a liquid) is around five and a half times greater:

The specific gravity of carbon in black coal is around 2.15 (1 cubic metre weighs 2.15 tonnes).  1 cubic metre produces 7.9 tonnes of CO2 (see Footnote 4).  The specific gravity of liquid CO2 is 1.18 (slightly denser than water) and the volume occupied by 7.9 tonnes is 6.68 cubic metres (6.68 kilolitres). 

Thus after adjusting for carbon content, one cubic metre of coal going into a power station will produce about five and a half cubic metres of liquid CO2 when compressed.

If it was liquefied, the CO2 produced annually by NSW power stations would compress to about 63 GL (gigalitres) = 63 thousand million cubic metres.

If it was liquefied, the CO2 produced annually by NSW power stations would compress to a volume of about a quarter of a thousand square kilometers one meter deep.  As indicated in the introduction, disposal of a volume of this size is an enormous challenge.

It can be seen that under carbon capture and storage, getting the CO2 from a power station to the sequestration site and injecting it is a much bigger job than mining the coal or getting the coal to the furnace.  This means that the existing power stations are the wrong technology in the wrong place for CCS.  They need to be located on good sequestration sites; as opposed to being close to the source of coal.

For these reasons alone, CCS technology is unlikely to be applied (in any but a demonstration or token way) to existing stations in NSW, and for similar reasons is unlikely to be applicable to the majority of current generation coal fired power stations in the World. But there are additional reasons to doubt that CCS can be generally applied even if a new generation of plants make capture economically feasible.

Pumping CO2 underground is a massive undertaking that is well in excess of the coal mining enterprise providing the coal.  Pumping a few thousand litres down a hole at a test site proves little.  Small scale return of to oil wells has been employed for many years. 

But to have any impact on carbon emissions, hundreds of gigalitres of CO2 would need to be sequestered over the life of each new or converted coal fired power station. Apart from the mass and volumes involved there are handling difficulties. 

At less than 5 times atmospheric pressure liquid CO2 undergoes a phase transition and becomes a solid, dry ice. To keep it liquid it needs to be kept at a pressure well in excess of five atmospheres[6] at -56.4o C. At ambient temperature it needs to be kept at above 60 atmospheres to remain liquid. To be pumped across the countryside in uninsulated piplines it needs to be above the critical point pressure of 73 atmospheres.  Any loss of pressure, due to a rupture or a loss of power, may well result in its boiling to gas followed by solidification of sections of the pipeline and/or damage the pumps. Ordinary carbon steel corrodes in the presence of moist CO2 and the pipelines need to be lined or made of stainless steel. A very significant and entirely novel infrastructure of large diameter high pressure pipelines and pumping stations will be required.  The pumps need to move large tonnages and volumes of liquid, comparable to a good sized city’s water supply, at very high pressures.

This will consume a lot of energy. The initial compression of the gas to liquid needs to overcome the latent heat of liquefaction of CO2 (approx 160 kWh/tonne).  For example according to its Wikipedia entry[7]Liddell power station releases an estimated 14.7 million tonnes of CO2 to generate 17,000 GWh per year. Assuming no inefficiencies, compressing this gas would consume 14.7 x 160 = 2,350 GWh per year or about 14% of its present electricity output.

To this needs to be added the unknown, but substantial, energy required for transportation to the sequestration sites and for underground injection, as well as vast additional infrastructure; capital and running costs.  Existing gas pipelines burn some of the gas to run pressure booster pumps along the string but these would need to be electric for CO2, involving additional high voltage lines and inevitable grid losses.

 Clever integrated design may potentially reduce some of these overheads (for example some of the heat released during compression may be recoverable at the compressing power station) but it is probable that the additional infrastructure and energy overheads required for CCS would make any future coal fired station so inefficient and resource consuming as to be impractical.

 

 


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Travel

Hong Kong and Shenzhen China

 

 

 

 

 

Following our Japan trip in May 2017 we all returned to Hong Kong, after which Craig and Sonia headed home and Wendy and I headed to Shenzhen in China. 

I have mentioned both these locations as a result of previous travels.  They form what is effectively a single conurbation divided by the Hong Kong/Mainland border and this line also divides the population economically and in terms of population density.

These days there is a great deal of two way traffic between the two.  It's very easy if one has the appropriate passes; and just a little less so for foreign tourists like us.  Australians don't need a visa to Hong Kong but do need one to go into China unless flying through and stopping at certain locations for less than 72 hours.  Getting a visa requires a visit to the Chinese consulate at home or sitting around in a reception room on the Hong Kong side of the border, for about an hour in a ticket-queue, waiting for a (less expensive) temporary visa to be issued.

With documents in hand it's no more difficult than walking from one metro platform to the next, a five minute walk, interrupted in this case by queues at the immigration desks.  Both metros are world class and very similar, with the metro on the Chinese side a little more modern. It's also considerably less expensive. From here you can also take a very fast train to Guangzhou (see our recent visit there on this website) and from there to other major cities in China. 

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Fiction, Recollections & News

April Fools’ Day

 

 

 

He was someone I once knew or so I thought.  One of those familiar faces I thought I should be able to place. 

What was he to me? An ex-colleague, the friend of a friend, someone from school?  In appearance he's a more handsome version of me, around the same size and colouring.  Possibly slimmer, it’s hard to tell sitting.  Maybe younger?  But not young enough to be one of my children’s friends.  I just couldn’t remember.

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Opinions and Philosophy

The race for a SARS-CoV-2 vaccine

 

 

 

 

As we all now know (unless we've been living under a rock) the only way of defeating a pandemic is to achieve 'herd immunity' for the community at large; while strictly quarantining the most vulnerable.

Herd immunity can be achieved by most people in a community catching a virus and suffering the consequences or by vaccination.

It's over two centuries since Edward Jenner used cowpox to 'vaccinate' (from 'vacca' - Latin for cow) against smallpox. Since then medical science has been developing ways to pre-warn our immune systems of potentially harmful viruses using 'vaccines'.

In the last fifty years herd immunity has successfully been achieved against many viruses using vaccination and the race is on to achieve the same against SARS-CoV-2 (Covid-19).

Developing; manufacturing; and distributing a vaccine is at the leading edge of our scientific capabilities and knowledge and is a highly skilled; technologically advanced; and expensive undertaking. Yet the rewards are potentially great, when the economic and societal consequences of the current pandemic are dire and governments around the world are desperate for a solution. 

So elite researchers on every continent have joined the race with 51 vaccines now in clinical trials on humans and at least 75 in preclinical trials on animals.

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