Open Thread 20

DBB, I read the linked article. You chose to criticise me for not following further links, which you did not cite. I find it odd that, despite the comments policy of this site, my supposed failure to follow unreferenced links could be construed as valid grounds for criticism.

Two links further on, in the actual report, we find that the real problem lies not with the 10ppb concentration of arsenic in groundwater, but the adoption of drinking water standards when clearly they are not relevant.

As I said – making a lot of noise about small problems is not the way to achieve optimal outcomes.

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Contrary to affirmation, I have, through necessity and a modicum of postgrad study, had to become reasonably familiar with regulations affecting water and with management of contamination of land and water. Perhaps not expert, but certainly in possession of a working, practical knowledge of licence requirements and of means of testing and of compliance.

In NSW, it is certainly not automatically expected that the quality of bore water is adequate for human consumption. Distinction is made between water’s various purposes, eg process water, recreational, stock and human consumption. I am astounded to discover that “…in the USA the expectation is that well water is safe to drink.” My recommendation would be to be aware of which aquifer was being tapped, to test before use, to retest regularly and to assume nothing.

That said, I happily accept DBB’s olive branch. Different regulatory regimes clearly have different approaches.

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Never having encountered
http://en.wikipedia.org/wiki/Khazzoom-Brookes_postulate
before I take it as a updated version of Jevon’s paradox.

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@ Cyril R raises the question of how much water would be needed by NP. That does assume the standard practice of raising steam to drive turbines.

If each of us consumes 1 kW of electricity, then about 2 kW of heat must be dumped. If that is taken away by evaporation of water at 2.45 MJ/L then 23.8 m3/a must be evaporated for each of us. We really should not be wasting 24 tonnes per annum per capita if we can avoid it. Currently each Australian uses about 150 m3/a of once-through fresh water (ABS) . In most places we have exceeded sustainability.

In an average year, the biggest river in Australia no longer reaches the sea, and its farmers are being pushed off the river. Most of the country has no brackish water to spare. We must find other ways of dumping heat. It would be pretty brainless to put our power stations beside the sea and have long powerlines that lead to a limited number of consumers in the near hinterland.

I reckon we should use air to drive our turbines. If we can do away with water, we can take the power to where it is needed and do away with a lot of transmission lines. If that power station is a nuke then that town doesn’t need a gas pipeline, a coal-bearing railway line or a water pipeline. It can even desal its own drinking water.

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The biggest single unit generator in Australia, the 750 MW Kogan Creek coal reactor, is air cooled. There should be no practical barrier to an air cooled design. The Hyperion SMR design is air cooled.

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Localized thermal pollution from once through condenser cooling is just that: localized. Where it plays a more significant role is on river locations where the high temp effluent can cause major fish kills by funneling hotter water down stream. This is a major regulatory hurdle in France where most of their plants are on rivers.

Ocean based plants don’t have nearly the same issue and the local ecology adapts pretty quickly the slightly warmer temperatures.

Actual sea life damage through such thermal excursions, traveling screen kills and “fry” killed by overheating as they travel through the condenser tubes often sound high due to absolute numbers “Billions and billions” but are actually a small, single digit percentage of any localized ecology.

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RC this reference says 23-27 kwh thermal per kL
http://en.wikipedia.org/wiki/Multi-stage_flash_distillation

whereas if I recall reverse osmosis needs 2-4 kwhe per kL. I guess if the heat was going to be dissipated anyway it could be used if it doesn’t reduce efficiency too much. I also understand the ideal RO inlet temperature for normal seawater is about 27C. Seaside thermal plant could be using seawater well under 20C most of the year so there is some leeway for pre-warming RO inlet water.

I seem to recall an aquaculture project on the NSW central coast was going to grow warmth loving sea worms in power station outlet water. I haven’t seen the packaged worms at the supermarket yet.

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John Newlands — thank you for the figure of 25 kWh/kL — in that case 2 kW per capita of exhaust heat from the reactor would supply a maximum of 700 kL/a of water warmed by 20°. A less efficient (perhaps less multi-) flash distillation would provide less water, but hotter. A range of choices, depending on the industry that town served.

Per capita arguments obscure implications of scale. A mine site and village consuming 20 MW (e) and dumping 40 MW (th) would hardly be worried about a few kilometres of hot pipe between the two plants. A city needing to dump 1 GW (th) probably could not send that amount of hot pipe into the suburbs, and might need to delay the water through a tangled pipe farm first.

Perhaps the piped heat would allow growth of a light industry, park, maybe including a thermal worm farm…

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Yes John Bennets, that’s how it works. Steam in condenser tubes. Air on the outside of the tubes, cooling them down. In the industry they are often called air cooled condensers, ACC.

There are many examples of this technique, most are used in combined cycle gas turbine plants, for the bottoming steam turbine. Such steam bottoming turbines operate at high temperature, and thus need less cooling, making dry cooling more attractive.

http://www.world-nuclear.org/info/cooling_power_plants_inf121.html

According to a 2006 Department of Energy (DOE) report discussed in the Appendix, in the USA 43% of thermal electric generating capacity uses once-through cooling, 42% wet recirculating cooling, 14% cooling ponds and 1% dry cooling (this being gas combined cycle only). The spreads for coal and for nuclear are similar. For 104 US nuclear plants: 60 use once-through cooling, 35 use wet cooling towers, and 9 use dual systems, switching according to environmental conditions. This distribution is probably similar for continental Europe and Russia, though UK nuclear power plants use only once-through cooling by seawater, as do all Swedish, Finnish, Canadian (Great Lakes water), South African, Japanese, Korean and Chinese plants.

Gas combined cycle (combined cycle gas turbine – CCGT) plants need only about one third as much engineered cooling as normal thermal plants (much heat being released in the turbine exhaust), and these often use dry cooling for the second stage.*

* CCGT plants have an oil or gas-fired gas turbine (jet engine) coupled to a generator. The exhaust is passed through a steam generator and the steam is used to drive another turbine. This results in overall thermal efficiency of over 50%. The steam in the second phase must be condensed either with an air cooled condenser or some kind of wet cooling.

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The footnotes to the WNN page on cooling are revealing…

Kogan Creek PS (750 MW coal) uses air-cooled condenser (ACC), whose fans consume 1.0-1.5 % of its power output. “South African experience puts ACC [capital?] cost as about 50% more than recirculating wet cooling and indirect dry cooling as 70 to 150% more.” However it does not say what that amounts to in $/W, though Scott’s comment above gives some idea.

WNN goes on to say that air cooling is unlikely in a large nuclear plant because of the value of copious supplies of water for emergency cooling. However, JM’s comment above points out that (small) Hyperion is air cooled. At shutdown, Toshiba’s (small) 4S is passive air-cooled.

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The brochure for the B&W mPower SMR states that it will optionally be available with air cooled condensers:

Click to access E2011002.pdf

The electrical output is 5-6 times that of the Hyperion.

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It’s certainly possible to have large amounts of freshwater stored onsite for emergency cooling, and still use dry cooling or hybrid cooling for normal operation. Increasing the demineralized feedwater supply in the condenser for example is really cheap. This would only be used in an emergency, for example in a PWR you can boil off the steam generator water inventory to cool the core without any AC power. In BWR the isolation condenser can perform the same function.

In a BWR it is less attractive to have dry cooling because the steam is radioactive and if there is no water on top of the condenser tubes then any leak could go outward without getting scrubbed out by the water. It wouldn’t be a safety issue but people will wine about any microcurie that comes out of a nuclear plant. The Vermont Yankee plant being a case in point.

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Backing wind with NPPs —
Prvided the NPPs are as agile as an ATMEA1, cycling at 5%/minute between 30% (minimum) and 100% with ‘instant’ return to full power, it appears that some penitration of wind power into a 100% NPP grid appears feasible. The economics, however, are a bit odd as a result of the necessity of providing backup to the variable wind generation combined with the lack of any signifcant variable costs associated with running NPPs; periodic replenishment is required irrespective of the attained capacity factor (CF).

Including reserves for NPPs undergoing replenishment & refurbishment, an additional 6% reserve margin for generator tripoffs and using believable (but approximate) costs and financing suitable for the USA, the NPPs daytime LCOE is US$0.0912/kWh (CF=86%) while the nightime LCOE is US$0.135/kWh (CF=60%) [assuming the load is 70% of the daytime load]. Suppose that customers and the NPP fleet operator are satisfied with this arrangment but that wind farm operators now want a piece of the action.

The difficulty is that all the NPPs must remain to act as balancing agents, i.e., backup, for the wind farms even though the NPPs will, on average, operate at lower CFs and so hgher LCOEs. Assuming an average of 5% of the energy is supplied by the wind farms: for the NPPs the daytime LCOE increases to US$0.0968/kWh (CF=81%) and the nighttime LCOE increases to US$0.1423/kWh (CF=55%). Since the NPP fleet operator cannot increase prices, she expects the wind farm operators to pay an integration fee to cover the difference; US$0.0056/kWh in the daytime and US$0.0073/kWh at night. Therefore so long as the wind farm operators can collect their LCOE and also the integration fee, everyone is satisfied at this level of wind penitration into the market. In particular then, the wind LCOE cannot exceed US$(0.0912-0.0056=0.0856)/kWh in the daytime and US$(0.135-0.0073=0.1277)/kWh at night. [For around here, both figures are more than enough; this might not be true in locations where the wind blows only at night.]

The limitation on wind penitration is set absolutely by the minimum CF of 30%; for 25% wind with an average of 5% penitration the maximum is 20% penitration during especially windy spells so half again as much wind could be accomidated provided the ever increasing integration fee can be met.

Unless someone finds a error, I’ll revise my prior claims to follow this analysis: if the LCOE for wind is low enough a modest penitration of wind into a low carbon grid can be accommidated.

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DBB: Spelling. Penetration, not penitration. Yes, I know I’m being picky.

Interesting post, though.

A table of calculated integration fees rising through 5% penetration steps will be very interesting. I expect that there will be two penetration limits.

The first will be technical, when NPP loads drop below 30%, or whatever the lower limit is.

The second will be commercial, which is reached when the anticipated marginal value of wind power first exceeds the anticipated marginal cost of nuclear, due to reducing average CF of wind as wind turbines are forced to spill due to oversupply. These are tricky calculations.

I look forward to reading how the integration fee is calculated, or at least how it is determined to be at the various levels of wind penetration. Is that fee a given constant, as set by the system operator, or is there a sliding scale?

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Not Australia. No more hints. I guess that makes me a sell-out in some people’s eyes. Gotta eat.

Re FiT’s and REC’s. I’m with Garnaut. These tools of bribery and waste will go, the sooner the better. They are essentially irrelevant.

I have just read Paul Gilding’s “The Great Disruption – How the Climate Crisis Will Transform the Global Economy”. I expected to disagree with someone such as him who has a very long history of left wing environmental activism, at times, even by his own admission, as an extremist.

Surprising (to me) i found a very logical and persuasive book which, though much in need of a better editor, makes a very good case that climate damage and economic collapse are now inevitable and tries to articulate an alternative to the current view of the economy as something which must always grow GDP. I recommend it as holiday reading. It’s on the shelves now, at $33 – or less, via the internet and after a wait.

Perhaps BNC can accommodate a discussion about economic models and post-collapse economics, but like most economics, it would probably degenerate rapidly into factional name calling and clashes of opinions.

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An interesting discussion about wind.

See: http://www.europeanenergyreview.eu/site/pagina.php?id_mailing=236&toegang=01161aaa0b6d1345dd8fe4e481144d84&id=3417

The Danes have long planned the elimination of oil, gas, coal and nuclear energy from their society. Their new government has increased the targets for doing so from 20% to 40% on a whole of nation basis by 2020, with complete phasing out by 2050.

The linked article itself is critical of the proposal. The real value of this link is in the comments, which parallel much of the similar discussions on this site. We are not alone in considering intermittency, subsidies and much more. We also have company in the nature of the comments from both sides.

Some of the linked articles appear to be interesting, but I do not have time to check them out today.

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John Bennetts — Thank you for the correction. I’m now not convinced by my own argument; I’ll attempt a more precise version. {Maybe even have all the spelling right as well.]

Cyril R. — Wherever wind farms go natgas burners are sure to follow. The Pacific Northwest and ERCOt are two more examples.

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An article about recent research suggesting LNT is an overly conservative notion of risks from low dose ionizing radioation:
http://esciencenews.com/articles/2011/12/20/new.take.impacts.low.dose.radiation

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# John Bennetts

I would very much like to endorse your suggestion that Barry invites a post from an economist. IMO, it should be one who accepts the scientific conclusions relating to global warming and its consequences and who has thought about the economic implications.

Can our existing capitalist model continue to exist in the absence of GDP growth?
Can liberal democracies exist in a system of zero or negative economic growth?
Can GDP growth be obtained in a biologically sustainable manner such that discretionary incomes can stabilise or increase?

If the answers to all three questions are negative, it would seem that our species, after a temporary escape from normal constraints made possible by fossil fuels, will revert to a situation in which the “laws of nature” once more obtain.

Happy Christmas!

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My comment just gave me an idea. The Canadian report that was posted here the other day i.e. http://www.ospe.on.ca/resource/resmgr/doc_advocacy/2011_draft_13dec_windelectri.pdf presented an interesting idea for cycling nuclear. it was to keep the reactor running at full output and then dump excess heat when less heat is needed to run the turbine and generator at lower electrical output. I.e. a new way to cycle nuclear power that could potentially have a very fast response time. But the waste heat got me to thinking that both the waste heat and the normal heat could be used in a distillation process. I know that this subject has been discussed before and many planners are saying that more water can be produced cheaper using reverse osmosis. Then other people I talk to dont want to use reverse osmosis because of cleaning and maintenance requirements. I want to present a new idea. The idea is that if we had a variable water supply then the heat could be quickly directed between electricity and water production. This means that the nuclear plant could take up the slack instead of gas plants for cycling purposes. I.e it would be possible to build an integrated wind solar and nuclear system where nuclear plays the role of both water producer as well as electrically stabilizing the power balance on the grid. The nuclear reactor would run at full output all the time producing either water or electricity. You could introduce as much wind and solar as you can to the system and nuclear power could fill in the rest. All fossil fuels on the system would be eliminated. Well its just an idea I thought you might want to consider.

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Some philosophical points on the discussion.
A NY Times blog entry around Amory Lovins’ latest book informed us he was paraphrasing Eisenhower’s “if a problem seems to have no solution, the best approach is to enlarge it.”
That seems to me to also be the best way to really, really, really, mess something up. I think that connects to the work of Thomas Homer-Dixon, one of the speakers at the Equinox summit this summer (wgsi.org), where he notes complexity is how we solve things.
I’m skeptical, and tend to think simplicity is always desirable, so I would note:
My understanding is that municipal water treatment is one of the easiest energy intensive uses that can be altered to use low-demand periods (daily). Conversely, letting millions of stoves and refrigerators cycle on and off randomly, instead of operating the individual cycling remotely, seems like an intelligent thing to do.
All of which is to say that I think Gene is correct in looking for the simplest methods to use generation that can’t be consumed immediately.

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There are those who like to tell nice sounding stories about smart grids and smart meters and how we can have our washing machine turn itself on at midnight etc, but what actually matters is how much demand is likely to be moveable, what are the time constraints (eg intra day, multi day etc) and what are the requirements for infrastructure changes over and above just the metering, signalling, control, power switching etc.

As part of the Renewable Energy Review, the UK Climate Change Committee commissioned a report on technical constraints on renewables: http://hmccc.s3.amazonaws.com/Renewables%20Review/232_Report_Analysing%20the%20technical%20constraints%20on%20renewable%20generation_v8_0.pdf

Figure 29, page 81 shows projected movable demand in 2030 and 2050. In 2030, essentially all movable demand is intra day for a total of 56 TWh of 400 TWh annual demand being movable.

But the really important thing is that the 2030 movable demand is almost all heating or transport. Sorry, the smart washing machines don’t matter much. The significance is that the usefulness of the “smart grid” is highly dependent on the rate of deployment of EV and PHEVs and on the large sale replacement of gas heating by electric heating. The latter in particular is no trivial or cheap exercise.

The bottom line is that it’s not just the “smart grid” that matters – it’s also very much the infrastructure that plugs into it. Changes to the latter will be costly and may well not happen at the rate we may like. Making overly optimistic assumptions could lead to a mess and extended life for fossil fuel burners because the movable demand hasn’t arrived.

Of course the situation will be somewhat different in countries with predominantly warm climates such as Aus, but in colder climates the UK situation may be representative.

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PV and aircon are a pretty nice fit. Not always – you can have hot hazy days – but in most places, especially arid desertlike place, there is a really good correlation.

The correlation can be much improved by making some cold water or ice. A big insulated tank of chilled water attached to the aircon as energy storage. The PV makes electricity at noon which is used to chill water in the big tank. It doesn’t have to be grid connected, per se. It could be a full standalone system with a small battery for pumps and fans in the evening.

The grid in aircon heavy places would be much relieved with such a PV cold store system rollout, allowing nuclear baseload plants to take up most of the grid demand. There will still be excess nighttime nuclear generation, we’ll dump that in plugin hybrids and other electric vehicles as nighttime charging.

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Hi all. I rarely post around here as I’m not as knowledgeable as a lot of you folks, though I am definitely in the pro-nuclear camp, and learning more everyday.

I had a question I was hoping one of you could help me out with. First off, I’m part of a community of “traditional” environmentalists (read, do not support nuclear) and I do my best to make a pro-nuclear case to them when they post “we’re all going to die!” articles related to Fukushima. Here’s the latest one. A friend posted this link on their FB page:

http://fukushima-diary.com/2011/12/water-underground-contaminated/

And everyone on the FB thread seems to think now that all Japanese groundwater will kill you, and nuclear is the devil. etc etc. You’ve all heard the emotional rhetoric. This reaction is from a measured reading of 1.3-14.7 Bq/kg of cesium-137 in drinking water.

It is clear that no one who has commented on the link on FB thread knows anything about radioactivity or measuring dosage, so I want to post something intelligent to calm their fears (if possible!). I know that Bq is not a measure of radiation dose, and my understanding is that the human body is naturally radioactive at about 100 Bq/kg (mostly from potassium?). Also, the regulatory safe level for caesium-137 in drinking water in Japan is 200 Bq/kg. So is there reason to freak out about a reading of 1.3-14.7 Bq/kg in drinking water in Japan? What would you say to clam people’s fears?

Thank you!

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@ Chris. One thing you could do is show the natural radioactivity all around us, in the sea and in the soil. Seawater for example contains around 11 Bq/liter of K-40, a similar nuclide to radiocesium. Typical soil even contains 400 Bq/kg, which is around 800 Bq/liter, of K-40. There are other elements in soil and sea water as well, such as uranium and thorium. This is perfectly natural. You certainly won’t have to worry about a few Bq/liter in drinking water. Especially not for cesium which doesn’t bioaccumulate in small organs.

http://www.physics.isu.edu/radinf/natural.htm

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Slightly off topic, but the link below is to a news item which links cancer and breast implants, even though further down in the article, it is stated that no link has been demonstrated.

It seems to me that the whole purpose of the article is to get the trigger word “cancer” into the headline to attract eyeballs, even though in this case, as with so many other cancer scare items, there is no demonstrated link.

But the agency stressed that no link had been established between cases of cancer and having PIP implants. It said the number of breast cancer cases in women with PIP implants reported to date “remains lower than the rate observed in the general population”.

When it comes to presentation of the facts regarding the causes and incidence of cancer, whether in relation to radiation or otherwise, journalists have stirred up a lot of unwarranted fear and anxiety.

http://www.abc.net.au/news/2011-12-31/20-cancer-cases-in-women-with-faulty-breast-implants/3753696

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It seems clear that the State of Queensland has not the slightest intention of participating in the low carbon push. On ABC 7.30 (no transcript) was a discussion of fly-in fly-out mining employment. It was proposed to run a shuttle flight from the Gold Coast to a mine seeking another 1,000 employees. Commenters were at pains to say it produced ‘resources’ but BMA the company concerned mines coal. I’m sure asbestos was also once described as a resource not a harmful product. I think of coal as CO2 that was sequestered millions of years ago. Funny thing I’m sure all those countries now buying more and more Queensland coal recently put their hands up at the climate conferences to say they were cutting back.

Now Gladstone harbour wants to be exempted from the heritage area that helps protect the Barrier Reef coastal zone. The harbour dredging will facilitate liquefied coal seam gas export which they describe as natural gas. I guesstimate that CO2 from Australia’s exported coking coal, thermal coal and LNG is now about 800 Mt a year. Add CO2 from LCSG to that in future plus increased solid coal and natural (marine sediments) gas exports. Meanwhile domestic net CO2e from all sources should be around 550 Mt this year, aiming for 480 by 2020. I hope someone from the government can explain why we are even bothering with a domestic carbon tax.

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Clarification: JN asked for a response from the government. I am not a member of or spokesperson for any political party or government.

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I share Mark Duffett’s exasperation with BOM’s reference to a severe weather event as “a once in a lifetime event”.
https://bravenewclimate.com/2011/12/07/open-thread-20/#comment-147075 (BOM is Australian Bureau of Meteorology)

Such useage implies that the next lifetime’s weather is going to be the same as the last lifetime’s weather. And if anyone has the authority – and responsibility – of warning the public that it aint gonna be so, it is BOM’s.

Better to say “Records only indicate a 2% probability of it happening in past years”. This still allows a “gosh-spooky!” inference by the casual listener while allowing the more thoughtful to realise that severe weather is becoming more frequent.

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John Bennetts — Changes in the frequency and severity of tropical cyclones (hurricanes and typoons in the northern hemisphere) remain speculative.

Straightforward physical arguments suggest that globally averaged precipitation should increase with increasing temperature. However, over the satellite era [when global data can be acturately obtained] no such trend is observable with statistical significance. This is quite a mystery and may relate to changes in cloud cover.

What is observable is a marked increase in precipitation in mid and high latitudes; possibly also in the tropics. It follows that precipitation is declining, on average, in the semitropics, which includes the deserts, semi-deserts, savannas and steppes. There is some evidence for this as well, but the coverage is quite poor.

In regions with increased precipitaion, if all else remains the same [it doesn’t], the proportion of extreme precipitation events remains the same and so such occur more frequently. However, there perhaps is evidence that the proportion is increasing.

Rather than continuing to conduct this inadvertent experiment for knowledge’s sake, far better to bring it to an end in favor of conditions best conducive to the practice of agriculture.

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Roger C:
You got me again. Factor of 1000 error. Work it out for yourself, from the figures I provided:
Installed capacity of MacGen’s two stations is 4660MW.
There are 8660 hours per year.
The water licence is for a max of 73GL/a.
Subtract for natural evaporation from storages, about 10GL/a.
Add for overland inflow, which is not much due to small catchment areas.
Subtract for shortfall on extracting 73 Gl, which is a bit of a moveable feast due to weather and license restrictions. Besides which, if water releases are ordered from Glenbawn Dam and, when they pass the river pumps mechanical failure prevents extraction of part of the released volume, that is lost. Similarly, in the uncommon situation when water is released back into the river, eg due to safety checks of the discharge valves, that is also lost.

Evaporation from dams is about 10GL/a excluding thermal forcing due to operating plant.

Adjust for typical unit loading – ranges between 75 and 85 percent, plus a further reduction for planned outages – say 3 x 500MW x two weeks per annum, max.

The number is of course as rubbery as is the weather, but 1.6kg/kWh is close to the actual end result.

My apologies – I used a small calculator which has limited significant figures, rather than XL or similar.

Another rough rule of thumb is that MacGen uses 12 to 14 million tonnes of coal each year. So, for every tonne of coal burned, about 5 tonnes of water are “consumed”, plus natural evaporation of a further 10GL, which is constant and independent of load. Of course, this varies with coal quality and opeally has higher ash content than export coal.

The main point that I set out to make, but mightily stuffed up, is that power generation uses far, far less water than cities. South Australia’s and the MDB’s water woes are hundreds or even thousands of GL/a. Australia’s largest power generator extracts not more than 73 GL each year from the Hunter River, with a long term average significantly below 70.

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JB – Thanks for the update. It’s good to hear that BOM and planners now use probabilities instead of average-return-intervals, as the latter are instantly outdated in a changing climate.

Also for the estimated water cost of electric power: 1.6 kg/kWh. Good for that 3-second sound-bite, too: “Every unit costs the rivers a litre of water and the greenhouse a kilo of CO2”.

That’s 14 kL/a too. In comparative terms, it means that a person using 1 kW of electric power and about 140 kL/a of clean water, has used 10% of one to make the other.

I wish it were the other way around, that in the creation of 1 kW (e) the exhaust heat created the 140 kL/a — as we discussed earlier.

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Integrating solar PV with NPPs —

Having discovered the value of energy storage in the previous installment,

Open Thread 20

we now equip every NPP with a thermbine. A thermbine is a thermal storage equivalent of a small and inexpensive pumped hydro unit. Rather than storing the potential energy of superior position a thermbine stores heat in a thermal store. Some solar thermal generators use much the same but these thermbines have lower efficiency since the thermal store can only be heated to the temperature provided by a typical nuclear reactor.[NB 1] Translated to electical equivalents for simplicity and comparison to a pumped hydro unit, the Levelized Cost of Electricity (LCOE) is given by
LCOE(thermbine) = US${0.0292 + LCOE(NPP)/.8}
for diurnal operation.

With these the reference grid can then be energized by 28 1.1 GW nameplate NPPs of which at any time two are off line for replenishment and refurbishment. The remaining 26 are all on line at all times so that the overall capacity factor (CF) is 86% which leaves a reserve of about 2.1 GW. The LCOE for NPP operations is US$0.912/kwh. Thence LCOE(thermbine) = US${0.0292+0.912/0.8=0.1432}/kWh. The reference grid requires 20 GW for 8 hours followed by 28.57 GW for 16 hours:
LOCE(day) = US${0.7(0.0912) + 0.3(0.1432) = 0.1068}kWh;
LCOE(average) = US${(1/3)(0.0912)+(2/3)(0.1068)=0.1016}/kWh;
this is a cost improvement in comparison to daily cycling of the NPPs to meet to varying load. Suppose that customers and the NPP fleet operator are satisfied with this arrangement for wholesale prices. However, retail markup adds about US$0.04/kWh for customers and as solar PV price come down, eventually LCOE(solarPV) is less than US$0.1416/kWh. What happens to the grid and its market?

Assume the sun shines enough for full solar PV generation 4 hours per sunny day, between 10 am and 2 pm, and otherwise there is no such generation. On average 90% of days are sunny but cloudy periods may last up to 40 days.

There are three issues:
(1) assuring a balancing agent, i.e., backup for cloudy days;
(2) resolving the matter of displaced fixed costs, if any;
(3) setting prices fairly so that those without solar PV are not subsidizing those with solar PV.

For the first few individual customers with solar PV (solars), a small portion of the reserve can act as balancing agent on cloudy days without significantly increasing the risk of load loss. Possibly solars should pay a small fee for the increase in loss of load probability. If these solars can be treated as new load equivalents in a grid with growing load, then there are no displaced, i.e., unbillable, fixed costs. Indeed the price structure needs no modification.

Now assume a more significant solar PV penetration which displaces existing load during the sunny interval on sunny days. The otherwise unused thermal energy is stored for later use in the thermbines. As this is used 10% of the time on average, to recover costs requires an
LCOE(backup) = US${0.300 + .0912/0.8 = 0.414}/kWh
billable to solars on cloudy days. On average the solars pay the utility US$0.0414/kWh betweeen 10 and 2 pm. Using solar PV then becomes financially attractive when LCOE(solar) is less than US${0.1016-0.0414=0.602}/kWh as the retail markup is a wash.

This works fairly up to 30% of the daytime load. If solar PV begins to displace the remaining 70% then alternate low carbon storage schemes appear to substantially increase the cost of providing a balancing agent capable of operating for 40 days.[NB 2]

To the extent that solar PV energy unneeded by the solars does not displace energy provided by fixed cost resources, utilities could pay the solars for that energy. The net effect is to keep the thermal storage units well energized. The details depend upon exact circumstances, but the net to solars might average one to two UScents per kilowatt-hour. This could slightly increase net LCOE(solar).

In summary, some customer owned and operated solar PV is compatable with the assumed NPP+thermbine fleet.

Questions and commentss are most welcome.

Notes Below:

NB 1: Part of the steam produced from the nuclear reactor is directed to a heat exchanger to energize the thermal store. The fraction os directed is not variable so energizes the thermal store whenever the NPP is on-line. At the other end of the thermal store there is anothr heat exchanger to produce steam for the Rankine cycle generator of the thermbine. This is analogous to a pumped hydro unit with a pump which runs continuously and a generator which runs as required. The fixed cost estimate of US$0.0292/kWh is based on costs for a combined cycle gas turbine but the efficiency is just less than the assumed (31/37) in comparison the usual Rankine cycle efficiency for the turbine of an NPP. Other arrangements might well be more efficient but these thermbines are assumed to be readily added to any NPP.

NB 2: Adding additional storage in the form of pumped hydro ends up being even more expensive than what has been discussed. The only low cost balancing agent appears to be combined cycle turbines powered by natgas (CCGTs) since the variable cost of the fuel is a significant portion of LCOE(CCGT). But natgass burning is not a low carbon source of electricity.

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Maybe this carbon dioxide capture method will actually work?

New Materials Remove Carbon Dioxide from Smokestacks, Tailpipes and Even the Air
http://www.sciencedaily.com/releases/2012/01/120104115100.htm

This press release rewrite makes it appear more hopeful than prior materials developed as lab exercises. Even if viable, there is a long interval, with many pitfalls, to deployment.

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John Morgan — There are two questions which are better separated: (1) carbon dioxide capture from exhaust gases; (2) carbon dioxide capture from air. The article I linked clearly aims only at the first question, a problem currently beset with difficulties. As for the second, I suggest simply growing lotsa trees.

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@JM – regarding the K-F Lenz blog – I wouldn’t give him any oxygen. As things stand he is getting few visits and no comments. He is in fact (as Barry would say) at home, shouting at the wall.

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@Dino Rosati

Another way to use the mass difference between fission products and actinides is by roasting the fuel then etching the fission products off its surface. This seems like a quite non-proliferating way to handle breeding fuel.

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