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The fallacy of currently operating “clean coal”: Part 2

with 3 comments

Next up we might look at what the coal industry calls “a world-leading low-emissions coal power plant for Queensland” – the ZeroGen project.

Through a staged deployment program, the project will first develop a demonstration-scale 120 IGCC power plant with CCS, with a gross electrical power output of 120 MW. Again – only a gross electrical output of 120 MW, and a net electricity output to the grid which will be significantly less than that – it’s a tiny demonstration-scale plant, which is feebly small by the standards of most coal-fired power stations.

“The facility is due to begin operations in late 2012 and will capture up to 75% of its carbon dioxide emissions. Some of the CO2 will be transported by road tankers for partial geosequestration in deep underground reservoirs in the Northern Denison Trough, approximately 220 km west of the plant.”

(Quoted straight from the NewGenCoal website.)

Again, only some of the CO2 is captured, and only some of that CO2 which is captured is transported, for partial geosequestration.

To facilitate more rapid uptake of the technology at commercial scale, ZeroGen will concurrently develop a “large-scale” 400 megawatt IGCC power plant with CCS. Due for deployment in 2017, the facility will be “one of the first of its kind in the world” and will capture up to 90% of its CO2 emissions. It will be located at a site in Queensland as yet to be determined by a feasibility study. Of course, capturing 90% of CO2 emissions does not mean geosequestration of 90% of CO2 emissions, and in any case, 400 MW of electrical power output is not really a “large-scale” power station at all.

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. Of course, this is a pulverised-coal system under consideration, and not IGCC as the ZeroGen plant(s) are proposed to use, but it is very interesting material nonetheless.

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 and sequestered. To do so, the extra energy input 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.

The current industrial price for natural gas, as of August 2008, is USD $9.95 per thousand cubic feet, according to the EIA’s natural gas market page. One thousand cubic feet of natural gas corresponds to a heating value of about 1.09 GJ.

If a plant consumes 1350 GJ/h of natural gas at full output, then that is a fuel cost of 108 million dollars per year – leading to a significant increase in the operational cost of the plant.

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 CO2 emissions to the atmosphere of between 253 to 406 gCO2/kWhe 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. It is not at all “clean coal”.

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 of methane associated with the production and handling of coal and natural gas, and so forth.

At the Munmorah Power Station in New South Wales, a research-scale pilot plant will capture up to 3000 tonnes of CO2.

“It is hoped the Munmorah project will provide the foundation for a $150 million post-combustion capture and storage demonstration project in NSW, planned for operation by 2013, capturing up to 100,000 tonnes of CO2 each year.

The CO2CRC (the Cooperative Research Centre for Greenhouse Gas Technologies) Otway Project is Australia’s most advanced carbon dioxide storage project. Launched in April 2008, the project involves the extraction, compression and transport and storage of 100,000 tonnes of naturally occurring CO2. The CO2 is being stored in a depleted natural gas reservoir two kilometres below the earth’s surface.

3000 tonnes of CO2? 100,000 tonnes of CO2? That’s nothing. It is just not enough to make any difference to anything. The Munmorah power station emitted 2.1 million tonnes of CO2 to the atmosphere in 2007. Even if 100,000 tonnes of CO2 was captured and sent to geological sequestration, the remaining 95.24% of the CO2 is still going into the atmosphere as usual. Capture and geological sequestration of this 4.76% of CO2 is probably indistinguishable from normal variance in the plant’s total energy output and total CO2 emissions from year to year. You wouldn’t even notice any quantitative difference in the emissions.

In 2007, Eraring power station in New South Wales emitted 13.8 million tonnes of carbon dioxide, and in 2006, Loy Yang Power in Victoria emitted 19.3 million tonnes of carbon dioxide. For there to be any chance of “clean coal” to become a reality in any honest, meaningful way, these are the kinds of quantities of carbon dioxide which must be practically, safely and economically sent to geological sequestration, in their entirety.

There are at least two Cooperative Research Centers in Australia dealing with coal-based energy technology – the CRC for Coal in Sustainable Development, and the CRC for Greenhouse Gas Technologies (The “CO2CRC”.)

As far as I’m aware, there is not one CRC dealing with solar energy, wind energy, nuclear energy, or geothermal energy. There is not one, dealing with any such technologies. We do have industries who want to invest in these technologies as commercial enterprises in Australia, and we do have plenty of good scientists and academics who believe in all these different technologies, and yet, astonishingly, surprisingly, it is only the coal industry which has a showing in the CRC program.

The large energy requirements of capturing and compressing CO2 significantly raise the fuel costs and operating costs of CCS-equipped fossil fuel power plants, with the fuel requirement of a plant with CCS being increased by about 25% for a coal-fired plant, and about 15% for a gas-fired plant.

Additionally, increasing the overall greenhouse gas emissions intensity is increased well above what it’s claimed to be, since the gas is not captured with 100% efficiency. In addition, there are significant increases in capital costs for the plant.

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.”

Since 1996, the Sleipner gas field in the North Sea, the industry’s poster child for large-scale, established, operational geosequestration, has stored about one million tonnes of CO2 per year. A second project in the Snøhvit gas field in the Barents Sea stores about 700,000 tonnes per year.

The Weyburn project is currently the world’s largest carbon capture and storage project.
Started in 2000, Weyburn is located on an oil reservoir discovered in 1954 in Weyburn, southeastern Saskatchewan, Canada. The CO2 injected at Weyburn is mainly used for enhanced oil recovery with an injection rate of about 1.5 million tonnes per year.

These projects are by far the largest operational CO2 geological injection/geological sequestration projects in the world – and there are only a few such facilities in the world. Each such facility does not have nearly enough capacity for carbon dioxide geosequestration to handle the output from even just one large coal-fired power station.

3 Responses

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  1. Some ‘green’ academics have claimed that Australia’s electricity emissions could be halved using combined cycle natural gas without CCS. It is thought that the combination of developed gas, deepwater gas off WA and Qld coal seam methane could add up to about 5 gigatonnes each with heating value of about 6 X 10^10 J if my calculations are correct. That could take us past 2050. I’m excluding renewable gas such as biomethane.

    The problems are insatiable gas demand from the Northern Hemisphere which will force up local gas prices and the fact there are other ways to generate electricity, particularly base load. That will free up compressed gas for use as vehicle fuel when oil runs out and as feedstock for nitrogen fertiliser for which there are few other practical large scale substitutes. The simple conclusion is not to use either gas or coal for electrical generation if it can possibly be avoided.

    John Newlands

    November 16, 2008 at 12:00 pm

  2. Good analysis. Clean coal is a crock of shit. If they can get it to work in any substantial sense (i.e. more than 5% of any given power station’s emissions) its gonna be expensive as hell.
    I notice you are an advocate of nuclear power- what do u think of Yucca mountain? Whats the point of stopping climate change if 5000 or 10000 years from now theres heaps of radioactive waste all through the food chain… not trying to be an arsehole, its just the first thing that comes to mind…

    Old Mate

    November 18, 2008 at 5:30 pm

  3. I think the link for the paper by David Singh is now http://www.wise.uwaterloo.ca/pdf/co2_simulation.pdf.

    Cheers

    Anon

    March 5, 2009 at 11:02 pm


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