Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Posts Tagged ‘anthropogenic climate change

Blog Action Day

with 3 comments

Well, long time no post. I hope all my readers are well.

So, apparently today is something called “Blog Action Day“, and this year the topic of interest is anthropogenic forcing of the climate system, and mitigating the potential thereof.

So, OK, I thought I’ll write a blog post about it. The day is supposed to be about action, as the name suggests, so let’s talk about specific actions, with a view towards making a significant mitigation, in a realistic way, of Australia’s anthropogenic carbon dioxide emissions.

Australia’s brown coal (lignite) fired electricity generators have by far the highest specific carbon dioxide emissions intensity per unit of electrical energy generated, since they’re burning relatively high moisture brown coal. They are the most concentrated point contributors to the anthropogenic GHG output. Therefore, these are the “low-hanging fruit” – a very valuable target to look at first and foremost if we want to make the greatest realistic mitigation of the country’s carbon dioxide emissions in a practical way, followed by black coal-fired generators.

Australia’s total net greenhouse gas emissions in 2006 were 549.9 million tonnes of CO2 equivalent.

If we look at the three main sets of lignite-fired generators in the Latrobe valley in Victoria, they represent a very concentrated point source of CO2 output, so they’re a very good case to focus on specifically.

In 2006, Hazelwood generated 11.6 TWh of electrical energy, and 16,149,398 tonnes of carbon dioxide to atmosphere.

In 2006, Loy Yang A generated 15.994 TWh of electrical energy sent out to the grid and 19,326,812 tonnes of carbon dioxide to atmosphere.

I’ll exclude Loy Yang B from this list for the moment, since its numbers are eluding me.

In 2006, the Yallourn power station generated 10.392 TWh of electrical energy sent out to the grid and 14,680,000 tonnes of carbon dioxide to atmosphere.

If you look at the the total contribution of just those three brown-coal-fired plants combined, you’re looking at 9.12 percent of Australia’s total anthropogenic carbon dioxide emissions. If you replace those with clean technology that can deliver an equivalent electricity output, you get a 9.12 percent reduction in Australia’s CO2 emissions. (When you include Loy Yang B, I think it’s approximately 11-12%.)

That’s not a bad target for Australia to implement for the relatively short term for a real reduction in CO2 emissions. It can actually be done, if the real political will exists to do it.

Now, I’m not interested in this “100% renewable energy by 2020” business from the extremist any-excuse-for-a-protest Socialist Alternative set, because it is nonsense.

Replacing all the coal-fired and gas-fired generators in this country inside 10 years (and presumably only using wind turbines and solar cells, not nuclear energy of course since it doesn’t fit their para-religious ideology)? That’s complete bullshit, of course, because in the real world it cannot be done.

There’s a difference between setting a challenging target and setting a nonsense target. Unless you’re only trying to implement a political bullshit stunt instead of actually trying to hit your targets.

Of course, you don’t just close down the coal-fired generators. You’ve actually got to build their clean replacements first. So what do you use that can realistically replace a coal-fired power station? Nuclear power, of course.

Now, again, to be realistic, we probably can’t build LFTR/MSR, PBMR/HTGR, IFR/PRISM or any kind of nuclear fusion based generation capacity on a large scale to generate grid-connected energy right now. That’s not to say that pilot-scale research and development on those very cool technologies shouldn’t continue, but right now, getting more nuclear energy on the grid means advanced light water reactors – or maybe heavy water CANDU-type things, or conventional sodium-cooled fast reactors maybe. The most practical thing for serious deployment in the relatively short term is advanced LWR technology. In the slightly longer term, there is certainly a place to be encouraging both Gen. IV and fusion.

To get the same amount of energy as the total output from those coal plants, as above, which we’re talking about replacing, we need 4.56 GW of installed nuclear capacity, assuming a 95% capacity factor.

With 4 x 1154 MWe Westinghouse AP1000s, with a 95% capacity factor, you’ve got 4.62 GW, which is a little more than what’s needed.

You can easily have four nuclear power reactors integrated into one nuclear power plant.

Now, how much does it cost?

On March 27, 2008, South Carolina Electric & Gas applied to the Nuclear Regulatory Commission for a COL to build two AP1000s at the Virgil nuclear power plant in South Carolina. On May 27, 2008, SCE&G and Santee Cooper announced an engineering, procurement, and construction contract had been reached with Westinghouse. Costs are estimated to be approximately $9.8 billion for both AP1000 units, plus transmission facility and financing costs.

That gives you an idea of how much a nuclear power plant costs today, in the current financial environment, in the current regulatory environment.

If we double that figure of USD$9.8 billion, it’s AUD $21.4 billion. There will be some saving since we’re considering building four reactors at one plant, not two independent two-reactor plants.

How much that saving will be, quantitatively, I don’t really know. If the cost is reduced by 30%, we’re looking at 15 billion Australian dollars.

How long would it take? If the real political will exists to do it, 10 years is heaps of time. We could probably do even more in that timeframe if we really, really wanted to. AP1000 construction takes 36 months from first concrete poured to fuel load, if you ignore any political protest rubbish.

This is really just a base-line relatively achievable “base case”. After this decade, of course, the rate of nuclear power deployment – and related GHG emissions mitigation – could foreseeably accelerate.

What about the uranium input? About 600 tonnes of natural uranium per year total, for all four reactors. Australia’s present production, off the top of my head, is something like 10,000-11,000 tonnes. Australia’s present uranium production can very, very easily provide for Australia’s total electricity production even without expansion of uranium production – again, considering the inefficient once-through use of low-enriched uranium in conventional LWRs.

What about the so-called “waste”?
Roughly 80-85 tonnes of used uranium fuel per year. 96% of that is unchanged uranium, so that 76.8 tonnes of uranium can be seperated and re-used. It’s just uranium, so it’s not going to hurt you.

The remaining 3200 kg is made up of the valuable, interesting and unique byproduct materials from a nuclear reactor – unique resources with all kinds of different technological applications, which aren’t all radioactive, which you cannot get anywhere else.

Anyway, that’s one scenario which I happen to think has a lot of merit.

Maybe you don’t agree – but if you don’t agree, I’d love to see you elucidate an alternative scenario which can deliver the equivalent greenhouse gas emissions mitigation – shown to be accurate in a quantitative way – within a comparable timeframe and within a comparable cost.

It will not be inexpensive, and it will not happen overnight – but I have yet to see any scenario which can honestly do the same job faster and cheaper, when some real quantitative analysis is applied.

Written by Luke Weston

October 15, 2009 at 12:45 pm

Nitrogen trifluoride as an anthropogenic-greenhouse-forcing gas.

with 9 comments

A couple of articles in the media captured my interest this evening:

TV boom may boost greenhouse effect
Plasma, LCDs blamed for accelerating global warming

I must say, this looks like more biased “You’ve got a TV? You’re guilty of climate change!” baloney from the “green” fanatics in the press who like spinning scientific papers out of context.

Nitrogen trifluoride is used in the plasma and thermal cleaning of chemical vapor deposition (CVD) reactors in the semiconductor industry. It is also used as a source of fluorine radicals for plasma etching of polysilicon, silicon nitride, tungsten silicide, and tungsten, in which application it can replace perfluorocarbons such as hexafluoroethane and sulfur hexafluoride, resulting in both ecological advantage and improved process efficiency. NF3 is an alternative to these other potent greenhouse gases and its usage has increased markedly over the last decade.

This has got nothing to do specifically with manufacturing plasma TVs, and everything to do with manufacturing semiconductor devices and materials such as polycrystalline silicon.

One has to wonder what the emissions of sulfur hexafluoride, perfluorocarbons and/or nitrogen trifluoride are for the manufacturing of a typical plasma TV, and how it compares to the emissions of sulfur hexafluoride, perfluorocarbons and/or nitrogen trifluoride over the manufacturing of, say, one typical solar photovoltaic panel. Obviously a photovoltaic panel has got much more polycrystalline silicon in it than your TV – yet, do we hear anything about manufacturing of solar photovoltaic cells in this regard?

In fact, worldwide interest in sustainable energy systems and the ensuing growth of the solar photovoltaics industry is one of the main forces driving increased industrial demand for nitrogen trifluoride and other gases employed in the processing of semiconductor materials:

Emerging thin-film solar cells will be based on thin-film deposition technologies including CVD processing, says industry analyst Mike Corbett, managing partner of Linx Consulting, based in Boston, Massachusetts, US.

“Basically, tandem-cell thin-film solar cell production uses similar CVD tool sets as those used in the LCD industry. So as thin-film solar cells become more popular, there will be a high volume-growth potential for these gases,” says Corbett.

According to US-based industrial gas supplier Air Products, solar capacity is growing at more than 30%/year.

“With photovoltaics using many of the same raw materials as semiconductor manufacturers, we would expect to see strong growth in the products Air Products supplies to the photovoltaics industry,” says Dave Tavianini, photovoltaics business development manager for the company.

Looking ahead, Tavianini adds, demand for specialty gases will continue to accelerate as second-generation thin-film siliconphotovoltaics proliferate.

[From here]

The use of such materials applies to basically everything containing semiconductors – essentially all modern electronic technologies are equally relevant, from your PC to your TV to your solar panels to your PC to your cellphone. Semiconductor technology is a fundamentally important cornerstone of our modern civilisation.

Nitrogen trifluoride is a potent greenhouse gas, with a global warming potential (GWP) of 17,200 over a 100 year timescale. This places it second only to sulfur hexafluoride in the group of Kyoto-recognised greenhouse gases. It has an estimated atmospheric lifetime of 740 years, though newer research suggests a slightly shorter lifetime of 550 years and a GWP of 16,800.

With 2008 production equivalent to 67 million metric tons of CO2, based on estimated emissions for 2008, it has been calculated that NF3 may play a more significant role than emissions of the industrialized nations of perfluorocarbons or sulfur hexafluoride, which are included in the Kyoto protocol.

Increased wafer size and reduced critical dimensions demand higher process stability and often new processes. With new production lines being built newer and generally more severe environmental statutes apply. On top of that, there is the worldwide goal of perfluorocarbon emissions reductions.

Regarding the consumption of perfluorocarbon etch gases, chamber cleaning processes are the major contributor. Since the utilisation of etch gas in these processes is usually less than 50%, the remaining gas has to be destroyed and removed by a waste gas abatement system. Generally, for CVD and etch processes, waste gas abatement is necessary for several reasons, certainly including but not limited to environmental concern and legal restrictions on emissions of greenhouse-forcing fluorinated gases.

Tetrafluoromethane is used in the microelectronics industry alone or in combination with oxygen as a plasma etchant for silicon, silicon dioxide, and silicon nitride. Tetrafluoromethane is a gas that contributes to the greenhouse effect. It is very stable, lasts a long time in the atmosphere, and is a powerful greenhouse gas. Its atmospheric lifetime is 50,000 years and it has a global warming potential of 6500.

Hexafluoroethane is also used as a versatile etchant in semiconductor manufacturing. It can be used for selective etching of metal silicides and oxides versus their metal substrates and also for etching of silicon dioxide over silicon. Hexafluoroethane is very stable in the atmosphere and thus acts as an extremely potent greenhouse gas, with an atmospheric lifetime of 10,000 years and a global warming potential (GWP) of 9200.

Sulfur hexafluoride is also used as a plasma etchant in the semiconductor industry, along with other technological applications. It is the most potent greenhouse gas known, with a global warming potential of 22,800 over a 100 year time horizon – SF6 is very stable. Its mixing ratio in the atmosphere is lower than that of CO2; about 6.5 parts per trillion in 2008, compared to 380 ppm of carbon dioxide.

Recently, the use of NF3 as an etch gas for chamber cleaning processed has been reported to give promising results, and use of this gas has been increasing. Aside from the advantage of less wear on the chamber, gas consumption is lower, since the utilisation of NF3 is very high, at 85 to 99\%. At the same time NF3 has a far smaller atmospheric lifetime of 550 years than standard etch gases like tetrafluoromethane and hexafluorethane, with estimated atmospheric lifetimes of 50,000 and 10,000 years, respectively.

When comparing the global warming potentials of these gases, a 100-year integrated time horizon is used, and the benefit of using nitrogen trifluoride to replace the alternative reagents with regards to anthropogenic greenhouse effect forcing is obfuscated for that reason.

Global Warming Potentials over an 100-year integrated time horizon:

Tetrafluoromethane: 6500
Hexafluoroethane: 9200
Nitrogen trifluoride: 16,800
Sulfur hexafluoride: 22,800

Atmospheric lifetimes:

Nitrogen trifluoride: 550 years
Sulfur hexafluoride: 3200 years
Hexafluoroethane: 10,000 years
Tetrafluoromethane: 50,000 years

The fact is, nitrogen trifluoride presents an environmentally friendlier alternative to sulfur hexafluoride, and arguably an environmentally friendlier alternative to perfluorocarbon gases.

Whilst these inorganic fluorine compounds and perfluorocarbons have large global warming potentials, which make for dramatic media headlines, their atmospheric abundances and mixing ratios are very small, and hence their contributions to radiative forcing in the atmosphere and hence to anthropogenic forcing of climate processes are very small by comparison to carbon dioxide, methane and water vapor.

Carbon dioxide is responsible for an increased radiative forcing term of 1.66 W/m2, according to up-to-date IPCC data, along with 0.5 W/m2 for methane and 0.16 W/m2 for nitrous oxide. For comparison, sulfur hexafluoride is associated with a far smaller increased radiative forcing term of 0.002 W/m2, along with 0.001 W/m2 for perfluoroethane. We can reasonably expect that the contribution from nitrogen trifluoride is similar, at around 0.001 to 0.002 W/m2. Whilst nitrogen trifluoride is certainly worthy of inclusion under the Kyoto protocol, along with perfluorocarbons and the like, especially as worldwide consumption of the gas grows, it is however nothing worth making a huge irrational fuss in the media about.

Ref:

Robson, J. I., L. K. Gohar, M. D. Hurley, K. P. Shine, and T. J. Wallington (2006), Revised IR spectrum, radiative efficiency and global warming potential of nitrogen trifluoride, Geophys. Res. Lett., 33, L10817, doi:10.1029/2006GL026210.

Prather, M. J., and J. Hsu (2008), NF3, the greenhouse gas missing from Kyoto, Geophys. Res. Lett., 35, L12810, doi:10.1029/2008GL034542.

Reichardt, H., Frenzel, A. and Schober, K., Environmentally friendly wafer production: NF3 remote microwave plasma for chamber cleaning. doi:10.1016/S0167-9317(00)00505-0