Saturday, May 30, 2009

Armenian and Moscow Visas.

I returned last night from a round of trips, firstly in Bulgaria last week and then on to Yerevan in Armenia via. Moscow. I would advise that the security check in Moscow is rather draconian and I had my bottles of water, shaving foam and shampoo confiscated, as they were all greater in volume that the 100 ml allowed, beyond which one might apparently be considered liable to perpetrate an act of terrorism. I suspect there may be a roaring trade going on in the resale of such contraband but it is all bloody annoying anyway. As a piece of further advice, I met a man on the plane back to London from Moscow with a rather salutary tale.

He had returned from Ukraine, intending to fly back from Moscow having made his connection, to London. However, because he needed to traverse the route from terminal 1 ("domestic") at Moscow Sheremetyevo airport to terminal 2 ("international" flights), he found himself in limbo, because he didn't have a visa to enter Russia. Even though he was only going from one part of the airport to another, this apparently counted as entering Russian territory, and eventually he had to give an airport official his credit card and passport so he could buy him an Aeroflot ticket back to London, whereupon he could be granted a visa and hence get to terminal 2. Russian bureaucracy seems about what I remember it from 20 years ago, in soviet times, but please do be warned that they take their regulations to the letter.

In contrast to when I visited Armenia some 8 years ago - having returned to London on the morning of 9/11 to in my experience unprecedented levels of security - and needed to go to the Armenian embassy in London to get my visa (and relinquish my passport for those days while the deed was being done), now you can just get an from the e.consulate of the government of Armenia. At Heathrow they didn't seem to know of the scheme, which caused some consternation on the journey out, but once I arrived in Yerevan, they were well aware of this more recent innovation in allowing access to their wonderful country, and I would recommend anyone going there to avail themselves of its facility (link below). It costs $60. By the way, you also have to pay an exit-tax to get out of Armenia which you do at the Converse bank in Yerevan airport. That is about another $30.

20 years ago, Aeroflot was not the greatest of airlines mainly in that it used old aircraft, but now it is really a very decent airline, and cheap too in relation to British Airways for example and so I would certainly fly with them again, although here is a lot of bad-mouthing of Aeroflot on the internet. I can only speak from my good recent experience of friendly staff who can speak some English, that they use modern Airbus 320's, and flying with mainly Russians who are in general also in my experience a nice lot, as they were at a conference I attended on satellite technologies and gave the keynote lecture in Yerevan.

More about this kind of subject later, including Quantum Dots, but just to say that "I'm back", at least for a while until I go to the States later in the year, to give some lectures on the subject of "energy" and its relations.

Wednesday, May 13, 2009

Short on Gas.

Kurt Cobb has given a rather neat picture of a party that is about to be pooped [1]. He begins with discussion of balloons filled with helium which are a red-herring to the underlying connection of helium to natural gas, and that if helium is about to run short (so no more party-balloons), so is the world's provision of natural gas. Helium is a remarkable material, with some unique properties, especially in liquid form, as it is used as a coolant, for example to run superconducting magnets, e.g in MRI (magnetic resonance imaging; the safer alternative to x-ray body scanners) applications. It is also used as a blanket-gas to shield sensitive materials from atmospheric oxygen, and enable certain chemical reactions to be performed and indeed specialist welding operations in which the weld is stronger when the metal surface has not been exposed to reactive atmospheric gases. Helium finds further application in gas-cooled nuclear reactors, as a heat-transfer agent.

Most of the world's helium is found in the United States, and it is recovered by separating it from natural gas with which it is coincident. Helium arises from the decay of radioactive elements like thorium and uranium, whose atomic nuclei decay to form alpha-particles - helium nuclei - which form elemental helium by capturing a couple of electrons from their surrounding media. The majority of helium - since it is a material of low mass - simply rises into the atmosphere and escapes the Earth's gravitational pull to dissipate into outer-space, but some of it becomes trapped in the rocky formations of gas-wells, from which it may be recovered in concentrations of up to 7%.

As is the case for all fossil-materials, natural gas was laid-down in long times past and we will eventually use it up, especially against current rising demand for it. It is the same story for oil, ultimately coal, and indeed uranium, so most of our current energy production methods are living on borrowed time. Helium is also a fossil material, but it can be recycled, as I recall from working at the Paul Scherrer Institute (PSI) in Switzerland, which uses huge amounts of liquid helium to cool the vast array of magnets used to steer beams of charged particles, particularly muons, toward particular experimental arrangements.

At PSI, the helium is recovered and liquefied on site so it can be recycled, since is a comparatively pricey substance, and another recollection about it is that it diffuses through the steel walls of cylinders in which it is stored under high pressure. If you get a new helium cylinder and don't use it for say, 6 months, when you attach the pressure valve, about half of it has gone!

While the world would certainly not grind to a complete halt if all its particle physics institutes had to close-down in the absence of helium, modern medicine would be disadvantaged and need to return to using x-rays as a means to "photograph" the inside of human bodies as in the CT-scanner alternatives to MRI. If we run short of natural gas, however, the world won't run on with this fact largely unnoticed, and peak gas looks to hit at around 2025 [2]... a mere 15 years time, and more and more of it is used each year, along with all other sources to slake a dust-dry thirst for energy.

I have written before "Metals Shortages" [3] about how indium and gallium are likely to run out in 5 - 10 years with impacts on any and everything electronic, at least in the complex matrix of electrical devices. Hafnium is another metal whose days are numbered, which is an essential component of computer-chips and also employed as a thermal-neutron absorber in nuclear control-rods, and may literally run-out within 10 years. Peak oil we all know about, but peak gas, peak uranium and peak coal will follow. There is in fact a peak in the production of all materials that were laid down in the distant past, and we are using them up at an expanding rate.

Even if we manage to solve our energy problems, we won't have enough "stuff" to make things from.

Related Reading.
[1] "Let's party 'til the helium's gone", By Kurt Cobb.
[2] "Natural Gas: how big is the problem?", By Louis de Sousa.
[3] "Metals Shortages", by Chris Rhodes: Chemistry and Industry, 25th August 2008, p21; the article is also on and on this blog too:

Tuesday, May 12, 2009

Quantum Dots and Ultra-efficient Solar Cells?

I have been invited to give a lecture at the Yerevan Physics Institute in Armenia at the end of this month, on "Solar Energy and Space Applications", in which I plan to stress technology for keeping satellites going, and hence maintaining the global information function of the world, even if other aspects of its connectivity begin to fade. During the process, I came across "Quantum Dots" which strike me as rather interesting materials in this respect, particularly in terms of increasing the energy conversion efficiency of solar radiation to electricity (photovoltaic capacity), radiation resistance and lightweight payload for launching. Given that energy efficiency is probably the key feature to exploit in our riding-down Hubbert's peak, I thought I would share this with you.

The term “quantum dot” (QD) was coined by Mark Reed at Yale University. A QD is a semiconductor whose excitons are confined in all three spatial dimensions. Accordingly, they have properties that are between those of bulk semiconductors and those of discrete molecules. They were discovered by Louis E. Brus, who was then at Bell Labs. QDs are nanocrystalline materials (or materials that contain nanocrystals) in which the dimension of the crystal is smaller (in all directions) than the Bohr exciton radius of the exciton pair (M+ ... e-).

This causes the energy levels to become quantised (quantum confinement), as in individual molecules, rather than coalescing into the “band structure” of bulk semiconductors Traditional (bulk) semiconductors lack versatility, since their band-gap and hence optical and electronic properties cannot be easily changed, if at all. By tuning the size of the QD particle, the band-gap can be tailored for specific applications. The gap enlarges as the crystalline dimension decreases, so that the fluorescence wavelength shortens; and conversely, as the crystal becomes bigger, the wavelength increases, so the fluorescence shifts toward the red end of the visible spectrum.

QDs range in size from 2 - 10 nanometers (10 - 50 atoms) in diameter and contain as few as 100 to 100,000 atoms. Nearly 3 million quantum dots could be lined up end to end and fit within the width of a human thumb. There are several ways to confine excitons in semiconductors, resulting in different methods to produce quantum dots. In general, quantum wires, wells and dots are grown by advanced epitaxial techniques in nanocrystals produced by chemical methods or by ion implantation, or in nanodevices made by state-of-the-art lithographic techniques.

There are also colloidal methods to produce many different QD semiconductors, including cadmium selenide, cadmium sulfide, indium arsenide, and indium phosphide. Large quantities of quantum dots may be synthesized via colloidal synthesis., which can be done under benchtop conditions, i.e. you just mix chemicals in a flask, rather than complex molecular beam epitaxy techniques. QDs are less rapidly damaged by radiation because ejected electrons and positive holes can recombine harmlessly (i.e. without molecular structure changes, e.g. atomic displacements, bond breaking, cascade ionisation and creating further damage centres etc.)

There is a dimensional restriction on the normal reactivity of the bulk material, since the QD is smaller than the radiation spur (track) distance, which limits the extent of chemical reactions normally induced in the bulk semiconductor, and in the absence of alternative routes, the holes and electrons are more likely to simply recombine. Thin-films too are relatively radiation-resistant, and one can invoke a simple geometric argument, in that the total concentration of active material is comparatively small, hence kinetically the relative rate of damage is lower.

Quantum dots offer the potential to improve the efficiency of solar cells in two respects: (1) by extending the band gap of solar cells so they can harvest more of the solar spectrum, and (2) by generating more excitons from a single photon.

Extending the solar cell band gap into the IR region.

Almost half the intensity of sunlight ranges within the IR region of the electromagnetic spectrum. Thus Photovoltaic cells that respond to IR – ‘thermovoltaics’ - can even capture radiation from a fuel-fire emitter; and co-generation of electricity and heat are said to be quiet, reliable, clean and efficient. A 1 cm2 silicon cell in direct sunlight will generate about 0.01W, but an efficient infrared photovoltaic cell of equal size can produce theoretically 1W in a fuel-fired system.

It was discovered in the 1970s that chemical doping of conjugated organic polymers increased electronic conductivity by several orders of magnitude, leading to the application of electronically conducting materials as sensors, light-emitting diodes, and solar cells. Conjugated polymers provide ease of processing, low cost, physical flexibility and large area coverage. They now work reasonably well within the visible spectrum.

In order to make conjugated polymers work in the infrared range, researchers at the University of Toronto wrapped the polymers around lead sulphide quantum dots tuned (by size) to respond to infrared [5]. The polymer poly(2-methoxy-5-(2’-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) absorbs between ~400 and ~600 nm. QDs of lead sulphide (PbS) have absorption peaks that can be tuned from ~800 to ~2000 nm.

By wrapping MEH-PPV around the QDs shifted the absorption spectrum of the polymer was shifted into the infrared. Commercial implementation is predicted to come about within 3-5 years.

Multiple excitons from one photon..

Researchers led by Arthur Nozik at the National Renewable Energy Laboratory Golden, Colorado in the United States showed recently that the absorption of a single photon by their QDs yielded - not one exciton as is usual for bulk semiconductors - but three excitons!

The formation of multiple excitons per absorbed photon requires that the energy of the photon absorbed is far greater than the semiconductor band gap. This phenomenon does not readily occur in bulk semiconductors where the excess energy simply dissipates away as heat before it can cause other electron-hole pairs to form. In QDs, the rate of energy dissipation is significantly reduced, and the charge carriers are confined within a minute volume, thereby increasing their interactions and enhancing the probability for multiple excitons to form.

A quantum yield of 300 percent was recently demonstrated for 2.9nm diameter PbSe (lead selenide) QDs when the energy of the photon absorbed is four times that of the band gap. However, multiple excitons start to form as soon as the photon energy reaches twice the band gap. Quantum dots made of lead sulphide (PbS) also showed this phenomenon.

“We have shown that solar cells based on quantum dots theoretically could convert more than 65 percent of the sun’s energy into electricity, approximately doubling the efficiency of solar cells”, said Nozik.

QDs do seem to offer remarkable potential in photovoltaic applications generally, but in space-applications particularly, in terms of radiation resistance, low payload weight, and light to electricity conversion efficiency.

Related Reading.

Thursday, May 07, 2009

Microwaves for Industrial Scale Biochar Production.

Industrial scale microwave ovens could be used to produce biochar on a large scale. Professor Chris Turner from Exeter University, has built a 5 meter long prototype device that can lock-up a tonne of CO2 by pyrolysing wood into biochar, at a cost of $65. Each crop of trees absorbs CO2 from the atmosphere through photosysnthesis while they grow, and much of that carbon can be stored in a form of charcoal that is stable in soil for hundreds to thousands of years. In addition to storing carbon in this way, and remediating its presence in the atmosphere, the strategy could also produce synthetic terra preta soil, which is particularly fertile and less demanding in the amounts of water and nutrients that need to be added to it to grow plants in it.

Biochar has received regular mention for the past several months, and I have outlined its nature and advantages on various postings here. The wood or other biomass does need to be heated in some way, ideally such that liquid and gaseous decomposition products can be used as fuels to drive the process itself, making it self-supporting, and needing only biomass as a fuel and a reactant.

Frankly, I am sceptical as to how many microwaves can be built, and quickly at that, but the same question mark follows many proposed methods of environmental engineering. Allegedly, Turney's idea stems from a piece of serendipity that arose when he was a teenager. He microwaved a potato for 40 minutes by accident and found it had been converted into charcoal. He stresses that the kind of carbon capture and sequestration projects that are being promoted around the world only deal with emissions e.g. from power plants as they arise and do not address the carbon that is already in the atmosphere. If this can be pulled down through photosynthesis into biomass and the latter pyrolysed into biochar, in principle it is possible to decrease the atmospheric CO2 concentration.

As noted, however, building enough microwave ovens to produce biochar on a scale of the 8.5 billion tonnes of carbon per year released from fossil fuels will be no mean task, and probably impossible.

Related Reading.

Monday, May 04, 2009

Russia Floats Arctic Nuclear.

In its efforts to find oil and natural gas in the Arctic, Russia is looking to build floating nuclear power stations that can be propelled to strategic points to provide power for drilling etc. Five plants are planned, each carrying two reactors with a combined generating capacity of 70 MW. Since they are self-propelling, these vessels would enable the exploration of some of the most far-flung oil and gas fields in the Barents and Kara seas. Their design is such that they would need refuelling only once every 12 - 14 years and they would carry their own nuclear waste, which would finally need to be put somewhere.

I recall a newspaper headline from some while ago about "floating Chernobyls" which is probably rather unfair, but there are not surprisingly concerns about the safety of these devices. The Scandinavian watchdog group, Bellona, has voiced its reservations, saying that any radioactive leakage and indeed the heat output from the plants could impact on the fragile Arctic environment. Further fears from environmentalists are that the nuclear waste will simply be dumped into the sea. This is a somewhat time-honoured policy and there is supposed to be all kinds of nuclear detritus on the floor of the Barents sea, including abandoned nuclear submarines. Probably no one knows just what is down there, and most likely no one wants to know.

It is known that there are at least 12 nuclear reactors dumped on the islands of Novaya Zemlya and on its northern coast, along with 5,000 or so containers of nuclear waste. As I recall, Novaya Zemlya is where the Russians used to do their nuclear testing - I believe the atmospheric testing was done over the northern island and the underground tests on the southern island. It is likely as radioactive as hell there anyway.

As I have noted before when some pretty extreme proposals have been advanced to try and grab the world's remaining hydrocarbon reserves, the scheme does smack of desperation. Nonetheless, according to the U.S. Geological Survey, perhaps 25% of the world's total oil and gas lie under the Arctic, and there are diplomatic issues as to rights of their ownership. Russia famously planted a flag underwater, to stake its claim to one potential field off the northern coast of Siberia, where incidentally, there are hotspots of methane emissions from permafrost that is melting at a surprising rate. I doubt there is any connection other than that there is a lot of methane there in the form of methane hydrate.

A prototype floating power station is being built in the SevMash shipyard in Severodinsk, and there is an agreement made to build four more of them between Rosatom, the Russian state nuclear corporation and the Republic of Yakutiya in northern Siberia.

Impetus to find more gas may be in part connected with a recent fall in Russian gas production which sharpened steeply in April. Does this mean that the country is running out of gas, or are there other aspects of production or politics? If Russia's provision of gas is indeed less than has been thought, the impact on both east and western Europe could be as severe as that of the fall in oil once the giant Ghawar field begins to give up the ghost, i.e. perhaps 20 countries beginning to run short of fuel. Russian oil production remains firm, however.

In contrast, Gazprom's output of gas fell by 7% from 1.24 billion cubic metres to 1.15 billion cubic metres in April, in fact a fall by 28% from April 2008. Gazprom accounts for 80% of all gas in Russia and provides 25% of all gas used in Europe. Britain is trying to avoid being overly dependent on Russia for its gas, at a time of the poorest diplomatic relations between the two countries since the cold war. Instead, we are importing somewhere near to one fifth of our gas in liquid form from Qatar and are engaged in earnest discussions with our Norwegian friends to get them to bring a new gas pipeline to Britain rather than to mainland Europe.

We live in interesting times, as the countries of the world try to grab what is left of its plenty of oil and gas, even in such inhospitable regions as the Arctic, and inevitably the day will come when there is not enough to go around for all of us.

Related Reading.
[1] "Russia to build floating nuclear power stations," By John Vidal,
[2] "Russian gas output collapse in April," By Simon Shuster,