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 ‘fossil fuels

More on the Garnaut report.

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The next thing that gets on my nerves about the Garnaut report is its repeated emphasis – and optimism – on what are described as “near-zero emissions coal technologies”.

The success of near-zero emissions coal technologies will mean that new fossil fuel plant will continue to be coal, while Australia continues to gain as an exporter from the ongoing high global gas prices.”

“For Australia, the importance of reducing emissions from coal combustion is of large national importance.”

If this industry is to have a long-term future in a low-emissions economy, then it will have to be transformed to near-zero emissions, from source to end use, by the middle of this century. A range of technical, environmental and economic challenges must be addressed effectively to achieve this objective, in a time frame consistent with a global agreement on climate change and Australia’s own domestic commitment.

There is seemingly precious little discussion about the maturity of such technologies, how scalable they are, how far they are away from practical widespread use, the extent to which they actually mitigate carbon dioxide emissions, and how much these technologies will cost, and their economic competitveness, even under a GHG emissions trading scheme.

At its simplest, the challenge is to develop technologies that allow coal combustion with zero, or near-zero, carbon dioxide emissions while maintaining its relative competitive position as a fuel.

Those same forces of high capital costs, high world gas prices and relatively strong export coal prices will strongly favour retrofitted (post-combustion capture) coal plants with captive coal supplies and low-emissions profiles and ultimately, near zero emissions plants involving integrated coal drying and gasification technology.

This notion of “zero-emissions” or “near-zero-emissions” from coal is simply ridiculous and unfounded.

The IPCC Special Report on Carbon Capture and Storage reports that:

“Available technology captures about 85–95% of the CO2 processed in a capture plant. A power plant equipped with a CCS system (with access to geological or ocean storage) would need roughly 10–40% more energy than a plant of equivalent output without CCS, of which most is for capture and compression. For secure storage, the net result is that a power plant with CCS could reduce CO2 emissions to the atmosphere by approximately 80–90% compared to a plant without CCS.”

There’s an interesting paper here which provides a realistic analysis of the implementation of retrofitted CO2 capture for an existing pulverised coal power station.

This paper examines the retrofit of a 400 MWe pulverized-coal fired plant emitting 368 t/h of CO2 to enable CO2 capture while maintaining 400 MWe output, where 90% of the CO2 emitted from the coal plant is captured. To do so, the extra energy required for capturing CO2 was supplied by natural gas-fired gas turbines.

I’ve quoted the key points from the paper below. I’ve applied some minor editing and collation, but most of the material is straight from the paper cited.

Even when CO2 emitted from the gas turbines is not captured, the overall process still have some impact in reducing CO2 emissions, corresponding to an overall reduction in carbon dioxide output to the atmosphere of between 60-70%, with atmospheric CO2 emissions of between 110 and 138 t/h, compared to 368 t/h for the original coal combustion plant, at the cost of a natural gas requirement of about 1350 GJ/h.

When CO2 from the gas turbines is captured, the reduction in CO2 emission is between 68 and 77%, or CO2 emission to the atmosphere of 86-113 t/h. However, a considerably large amount of natural gas is required (around 3140 GJ/h), which is certainly not reasonable.

The total amount of natural gas required is between 3100 and 3300 GJ/h. To put this number into perspective, this amount of natural gas would generate about 460 MWe when used in a combined-cycle gas turbine plant without CO2 capture. The relative emissions are between 23% and 32% of the original coal power plant, which has a significant impact on the reduction of CO2 emissions.

In addition to the cost analysis, the future work will investigate other possibilities of integrating gas turbines into the coal power plant. The configuration presented in this paper represents one extreme, where all the electricity is generated from coal and the auxiliary power is generated from the gas turbine and natural gas boilers. Another extreme is to consider the classical view of producing all the auxiliary power from the coal plant, at the expense of decreasing the net electrical output. To compensate for the lost electrical output, a combined-cycle gas turbine with CO2 capture will be added. Combinations between these two extremes will also be investigated.

For a nameplate capacity of 400 MW, and a capacity factor which we may assume to be, say, 85%, carbon dioxide emissions of between 86 and 138 t/h correspond to emissions of between 253 to 406 grams of carbon dioxide per kWh generated.

The results from this study certainly paint a less optimistic assessment of the carbon dioxide emissions intensity of “clean coal” than the 80-90% reductions estimated by the IPCC.

That’s not clean coal. Much like the use of fossil fuel methane, it’s a bit cleaner, but it certainly isn’t clean.

Indeed, such levels of carbon dioxide emissions intensity are not much better than existing high efficiency combined-cycle natural gas fired gas turbine power plants. Given that the carbon dioxide emissions aren’t grossly worse, and given that gas turbine plants are already established, mature technology which is likely to remain far more economically competitive with this expensive, immature, unproven future technology, it is easy to envision that natural gas will be the main focus of the fossil fuel combustion energy industry over coming years, as opposed to the development of CCS technology, even where emissions trading is introduced.

The exception to this, of course, is where there is a vested interest in keeping the existing coal-fired power plants, and enormous coal-mining infrastructure, even if it is a less than sensible choice on many different levels. Natural gas turbines are of course, along with nuclear power, by far one of the biggest “threats” to the coal mining and coal-combustion electricity generation industry.

Additionally, that’s only considering greenhouse gas emissions from combustion at the power plant – without any consideration of whole-of-life-cycle analysis of coal mining and natural gas production – the enormous scale on which coal is mined, along with the fugitive emissions associated with the production and handling of natural gas, and so forth.

There is a large body of literature and knowledge of the whole-of-life-cycle analysis of energy intensity, environmental impact and greenhouse gas emissions associated with, for example, nuclear power, solar photovoltaics or wind power.

However, since fossil fuel combustion energy generation has such a comparatively fantastically high level of carbon dioxide emissions in the combustion process itself, I feel that sometimes it’s easy for some of us to forget that it’s only sensible to apply the same metrics across the life cycle for fossil fuels, just as people insist on analysis the impact of the entire life cycles for nuclear energy or solar energy, for example.

What is desperately needed is further research into the life cycle analysis of coal or other fossil-fuel combustion based energy generation systems when they are combined with proposed carbon capture and storage technologies. This is clearly important if a fair comparison is to be made between the economic and environmental feasibility of fossil-combustion CCS and alternatives such as nuclear power, wind, hydro or so forth.

Personally, I believe that as such analyses are performed, the extreme skepticism with which many of us view the comparative practicality of these “low-emissions” fossil fuel combustion technologies will begin to be vindicated.

Not-really-clean-coal for Victoria.

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Just two days before the Garnaut report on climate change is handed down, the Victorian Government has given the go-ahead to a new brown-coal power station in Latrobe Valley.

Environmental campaigners said it was “complete madness” to approve the $750 million plant, but the Government said the station would use new technology that would slash greenhouse gas emissions.

The project is a joint venture between consortium HRL and Chinese power giant Harbin Power, and will receive funding of $100 million from the Federal Government and $50 million from the Victorian Government.

“The $750 million HRL plant will use technology which has been developed right here in Victoria and is part of the new generation of clean coal power stations designed to slash greenhouse gas emissions,” said the Energy Minister, Peter Batchelor.

“The project uses a process called integrated drying gasification combined cycle (IDGCC) which can reduce emissions of CO2 from brown coal-fired power generation by 30 per cent and reduce water consumption by 50 per cent, compared to current best practice for brown coal power generation in the Latrobe Valley.”

Robert over at Larvatus Prodeo actually reported on this at length last year, when the project was first announced, and there’s a good body of details of the project and discussion to refer to there.

Typical generators burning Victorian brown coal generate 1175 g CO2e per kWh of electricity generated.

The IDGCC plant will reduce carbon dioxide emissions by 30% – so, that’s about 823 g CO2e/kWh.

For a good supercritical black coal burning plant you’ve got about 863 gCO2e, and 751 g for natural gas, or 577 g for combined cycle natural gas – which is about the absolute lowest you’ll get for a fossil fuel.

The carbon dioxide emissions are still high as all hell. It’s basically the same as a black coal fired power plant – in absolutely no way is it low in greenhouse gas emissions. All that the IDGCC technology is really accomplishing is to turn a plant powered by brown coal – the most especially inefficient and carbon dioxide intensive form of coal – into the emissions equivalent of a more conventional black coal fired plant. Make no mistake – the entirety of that dangerous fossil fuel waste is being discharged straight into the environment, as per business as usual.

But there’s one aspect to this which I find interesting, in particular.

This plant is slated to cost 750 million (Australian) dollars, and will have a nameplate capacity of 400 MW.
That is; $1875 per kilowatt of nameplate capacity.

The US nuclear energy industry is aiming to build new nuclear power plants for a cost of $1500 to $2000 per kW capacity.

The General Electric ABWR was the first third generation power plant approved. The first two ABWR’s were commissioned in Japan in 1996 and 1997. These took just over 3 years to construct and were completed on budget. Their construction costs were around $2000 per KW.

Westinghouse claims that the AP1000 power reactor will cost $1400 per KW for the first reactor and fall to as low as $1000 per KW for subsequent reactors.

I don’t know what kind of capacity factor is to be expected from an IDGCC plant – but at best, it’s comparable to that of nuclear power. If the capacity factor is significantly less, then this decreases the economic competitiveness of the coal plant relative to nuclear power still further.

We’re looking at the construction of a coal-fired power station that is not mitigating its carbon dioxide emissions in any meaningful way, emitting about 823 g CO2e/kWh straight into the atmosphere, along with all kinds of other dangerous coal byproducts, where the construction of a new nuclear power plant is already likely to be directly competitive, if not superior, on construction cost terms, even in the absence of any kind of emissions trading scheme, carbon dioxide ‘price’, carbon dioxide capture and storage or carbon dioxide sequestration.

What’s up with that?

Written by Luke Weston

July 3, 2008 at 4:52 am

A little coal-fired satire.

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If the embedded video above doesn’t work properly on your web browser, use this link.

Written by Luke Weston

April 30, 2008 at 3:23 pm

Earth Hour, candles and carbon

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There’s one thing in particular that bothers me about Earth Hour – these people who electric lights and then go and light up candles, and think that they’re helping do something about anthropogenic forcing of climate change.

The widespread practice of misguided eco-Luddites turning off their lights for Earth Hour and burning candles as a source of light is grossly misguided and actually contributes to increased carbon dioxide emissions.

Yes, I know candles are nice and romantic – but you’re taking paraffin wax, in the form of a candle, and burning it, very inefficiently, at a low temperature. This stuff is pure hydrocarbon – it’s a heavy alkane fraction distilled straight off crude oil. This stuff is getting so scarce that nations are prepared to go to war just to secure it, remember?

A candle flame burns at a low temperature – so it’s a thermodynamically very inefficient source of energy – and most of the energy released in a candle is wasted as heat, anyway.

Even if 80% of your electricity comes from coal and fossil fuel fired power stations, as it does in Australia, burning candles is very polluting and certainly very greenhouse gas and carbon dioxide emissions intensive, even more so than electric lighting.

If you need to do something that requires light – then leave an electric light on – just one. It’s far more efficient, less carbon dioxide emissions intensive and better for the environment – not to mention much safer than using hazardous candles.

If you want the romance of a candle, try looking for candles that you are certain are made from pure “carbon neutral” beeswax or tallow – not from crude oil in the form of paraffin wax.

Can’t we just put science, reason, rationality, education and reason ahead of trendy politics and trendy dogmas – before it’s too late?

What Earth Hour should not be about is the notion that we want to have a civilisation without artificial lighting – this is absolutely ridiculous. Lighting up the darkness was one of the most useful technological achievements in human history – why would we give that up?

Using electricity for lighting is far more efficient and environmentally sound than the primitive technologies, burning fossil fuels dirtily, at ambient pressure and relatively low temperatures, that came before electrification.

The use of electricity, and the use of electric lighting, is part of our way of life, in a developed, technological first-world society – I, for one, am not prepared to give that up, not the least because we don’t have to.

Light bulbs don’t produce greenhouse gases – burning fossil fuels to generate electricity does.

Let’s focus our efforts on moving away from fossil fuel based electricity generation, and expanding the use of non-greenhouse gas intensive hydroelectricity, nuclear energy, and wind energy, to solve our problems with anthropogenic greenhouse gas emissions.

Earth Hour should be about doing everything that you can to reasonably, sensibly limit your demand for electricity – and we can do this every hour of every day, of course. It makes sense for everyone – after all, you pay for the electricity.

I guess I have a problem with the idea that Earth Hour symbolises something.

It might symbolise something, but it doesn’t actuallydo anything.

The only thing it symbolises is primitive society.

I’d much rather see people spend their Earth Hour doing something that really does count for something.

Instead of spending your Earth Hour bearing with an uncomfortable, dark lifestyle, use that hour to think about the things that we can all do every day to limit electricity consumption, that we will actually bother to do every day, that are compatible with the fact that, yes, in our developed first-world society, we actually use electricity, and we work after the sun goes down. Think about the things that are compatible with our sensible lifestyles in the developed world, and do them, and it works out better for everybody!

Now, let’s consider just how much, quantitatively, this use of candles during Earth Hour is responsible for increased emissions of greenhouse gases.

Postulate I: A typical candle produces about 13 lumens of visible light, from a total power output of about 40 W, most of which is heat.
Postulate II: A 40 W electric incandescent light bulb consumes 40 W of electric power, and produces approximately 500 lumens of visible light output.
Postulate III: The overwhelming majority of candles are made from petroleum, in the form of paraffin wax. Paraffin wax has a heat of combustion of approximately 42 kJ/g, and can be assumed to consist, chemically, entirely of pentacosane – \mathrm{C_{25}H_{52}}.
Postulate IV: The average greenhouse gas emissions intensity for electric power generation in Australia is about 1000 g \mathrm{CO_{2e}}/kWh, and electricity is transmitted with transmission losses of about 7%.

\mathrm{C_{25}H_{52}(g)\ +\ 38\ O_{2}(g)\ \to 26\ H_{2}O(g)\ +\ 25\ CO_{2}(g)}

\mathrm{M(C_{25}H_{52})} = 352.68 g/mol;

\mathrm{M(CO_{2})} = 44.0 g/mol.

Thus, we know the emission of carbon dioxide from burning candles:

\mathrm{\frac{40\ W/candle\ \cdot\ 25\ mol/mol\ \cdot\ 44\ g/mol\ \cdot\ 3600\ s/h}{4.2\ \times\ 10^{4}\ J/g\ \cdot\ 352.68\ g/mol}\ =\ 10.69\ gCO_{2e}} – per candle per hour.

And the rate of carbon dioxide emissions from the electricity generation corresponding to the use of 13 lumens worth of lighting – the equivalent of one candle – for one hour:

\mathrm{\frac{13\ lumens/candle\ \times\ 1000 g/kWh\ \times\ 107\%\ \times\ 40\ W\ \times\ 10^{-3}\ kW/W}{500\ lumens}\ =\ 1.11\ gCO_{2e}} – per candle-equivalent of electric light per hour.

Therefore, for every candle that is burned to replace electric lighting during Earth Hour, greenhouse gas emissions over the course of the one hour are increased by 9.6 g of carbon dioxide.
If the light output from a 40 W light bulb was to be completely replaced by candles, this will lead to the emission of an extra 295 grams of carbon dioxide per over simply using the electric lights – if the equivalent of one thousand 40 W bulbs are replaced by candles, that’s an extra 295 kilograms of \mathrm{CO_{2}} emitted.

In places where a greater proportion of the electricity supply is generated by nuclear energy or hydroelectricity, this increase in greenhouse gas emissions is even larger.

Written by Luke Weston

March 31, 2008 at 5:13 pm


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