Purpose and target audience of BraveNewClimate.com

Posted on 7 March 2012 by Barry Brook

Before I write a scientific paper, I always try to identify: (1) my main message [MM], in 25 words or less, and (2) my target audience [TA]. Doing this helps focus the ‘story’ of the manuscript on a key point. Papers that try to present multiple messages are typically confusing and/or too long for busy researchers to read. It also dictates the background and specialist terminology that the reader might be safely assumed to understand, as well as guiding the choice of journal that I will submit to. For instance, a paper written for Nature requires more general context setting than one sent to Wildlife Research.

However, it occurred to me that I’ve never tried to define the main message of the BraveNewClimate.com blog, nor really reflected on who the chief audience is. So let’s try.

In reality, both have evolved over time. Back in late 2008 – early 2009, when the blog (and my thinking on climate change policy) was in its infancy, it would have read something this:

2009 MM: Communicate the scientific evidence for anthropogenic global warming to the general public and policy makers, and advocate the need for, and urgency of, effective mitigation.

2009 TA: People seeking understanding of past climate change, current/future impacts, and the basis of modelled forecasts – all explained in relatively straightforward terms. A secondary target audience was those who were confused by, or enamored of, the repeated assertions of ‘the sceptics’.

Although I was proud to have developed the website on this scientific and philosophical foundation, neither of the above MM or TA are appropriate to BNC’s central purpose in 2012. So let’s try again.

2012 MM: To advocate an evidence-based approach to eliminating global fossil fuel emissions, based on a pragmatic and rational mix of nuclear and other low-carbon energy sources.

2012 TA: Environmentalists who disregard or oppose nuclear energy, and instead believe that renewables are sufficient (or that continuing to rely on fossil fuels is a rational energy policy).

The main message changed because I became progressively more interested in educating people on practical solutions to the problems of global change, rather than preaching doom-and-gloom. This shift in purpose was not because I don’t still consider the impacts of climate change to be incredibly serious and the evidence (ever increasingly) compelling — I do! It’s rather that I found the generic message of: “This is really bad, we must do something!” to be ineffectual, unappealing, and frankly, depressing. Besides, there are other sites that do this very well, so I now tend to leave it in their capable hands.

Instead, I became interested (okay, obsessed is a better word) with grasping and communicating the high-level issues associated with which low-carbon energy solutions will work most effectively at displacing fossil fuels and thus ‘solving’ climate change, at scale, in time, and within reasonable costs.

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Filed under: Clim Ch Q&A, Nuclear, Policy, Renewables | 45 Comments »

100% Renewable Electricity for Australia: Response to Lang

Posted on 27 February 2012 by Barry Brook

Guest post by Dr Mark Diesendorf, Institute of Environmental Studies, UNSW.

Click here for a printable 6-page PDF version of this response.

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This is a personal response to Lang’s (2012) article critiquing the peer-reviewed paper Elliston, Diesendorf and MacGill (2011) ‘Simulations of scenarios with 100% renewable electricity in the Australian National Electricity Market’, referred to hereinafter as EDM (2011).

I appreciate the large amount of work that Lang has done in attempting to assess our work. However, I think his critique is premature, because he has misunderstood the intent of our work, which was clearly identified as exploratory. It is the first of a series of planned papers that will pick up on some of the issues that he has raised (and others) and step by step prepare the ground for an economic analysis. Several other questions that he raises are simply repetitions of questions that we have already raised and in some cases answered in EDM (2011).

Lang appears to be confused and mistaken in some key issues, such as the reliability of generation, where his conclusions are incorrect and potentially misleading.

Reliability of generation

Lang misunderstands and hence misrepresents our result that, in its baseline scenario, supply does not meet demand on six hours per year. He draws an incorrect conclusion from this result to claim that ‘renewable energy cannot realistically provide 100% of Australia’s electricity generation’. However, he overlooks the fact, clearly stated in the abstract, the main body and the conclusion of EDM (2011), that all our scenarios meet the same reliability criterion as the existing polluting energy system supplying the National Electricity Market (NEM), namely a maximum energy generation shortfall of 0.002%. This criterion inevitably means that any energy supply system, including the existing fossil-based system, is likely to fail to meet demand on at least several hours per year.

This is simply realistic, because no electricity supply system has 100% reliability. To achieve this ideal would require an infinite amount of back-up and hence an infinite cost. For this reason, electricity supply systems have reliability criteria such as Loss-of-Load-Probability (LOLP, the average number of hours per year that supply fails to meet demand) or energy shortfall. The NEM uses the latter. Since Lang refers to LOLP later in his article, he presumably partly understands this fundamental principle of electricity supply, yet somehow forgets this when critiquing the principal conclusion of our paper.

His oversight invalidates his conclusion. Hence our conclusion stands: namely that, subject to the conditions of the model, a 100% renewable electricity system is technically feasible for the NEM based on commercially available technologies.

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Filed under: Emissions, Policy, Renewables | 67 Comments »

The Grattan Report on low-emissions energy technology – some critical comments

Posted on 14 February 2012 by Barry Brook

Guest post by Dr Ted Trainer, University of NSW (http://ssis.arts.unsw.edu.au/tsw/).

Wood, A, T. Ellis, D. Mulloworth, and H. Morrow (2012) No Easy Choices: Which Way to Australia’s Energy Future. Technology Analysis. Grattan Institute, Melbourne.

This report is a valuable addition to the literature on the prospects for renewable energy in Australia, providing some recent data on key output and cost factors. It is especially to be commended for expressing a considerable degree of caution about this possibility, and pointing to the difficulties and problems that would have to be overcome. Almost all literature on renewable energy reinforces the faith that it can fuel energy intensive societies, and enable smooth transition to a carbon free economy. Over some years I have groped to a more confident statement of a case contradicting this position. (Trainer, 2012.)

The following brief comments indicate the strength of this case, and argues that the Grattan Report fails to recognise the reasons why it is very unlikely that the world can run on renewable energy.

The Report’s cost and output assumptions for the various renewable energy technologies seem to be inline with those in other recent documents. The explanation of the limits and difficulties associated with geothermal, carbon capture and sequestration, nuclear and biomass are especially valuable. Their estimate of biomass potential is a remarkably low c 500 PJ of primary energy, about 8% of the present Australian total, and their discussion of the logistical problems in getting large quantities of this low density material to generators is sobering.

I think that the major problem in the Report is that there is no analysis of the quantity of plant and the resulting capital cost of a total renewable energy supply system. Two years ago I published an attempt to do this, (Trainer, 2010a), and have now considerably improved the application of the approach based on more recent and more confident data. Trainer 2012 explores the amount and cost of plant needed to meet a 2050 world renewable energy demand assumed to be 1000 EJ of primary energy, about twice the present amount, in winter and net of long distance transmission energy losses and the embodied energy cost of the plant.

The conclusion arrived at is that the ratio of energy investment needed to GDP would be much less than derived in Trainer 2010a, but still unaffordable. It would be around 15 times as great as it is now – even though a number of significant factors difficult to quantify were not included in the analysis. These would multiply the ratio several times. (The output and capital cost assumptions used were more or less in line with those in the Grattan Report.) Combining more optimistic assumptions (including solar thermal plant costing one-quarter of today’s cost) would only reduce the total capital cost by 40%.

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100% renewable electricity for Australia – the cost

Posted on 9 February 2012 by Barry Brook

Download the printable 33-page PDF (includes two appendices, on scenario assumptions and transmission cost estimates) HERE.

For an Excel workbook that includes all calculations (and can be used for sensitivity analysis), click HERE.

By Peter Lang. Peter is a retired geologist and engineer with 40 years experience on a wide range of energy projects throughout the world, including managing energy R&D and providing policy advice for government and opposition. His experience includes: hydro, geothermal, nuclear, coal, oil, and gas plants and a wide range of energy end use management projects.

Summary

Here I review the paper “Simulations of Scenarios with 100% Renewable Electricity in the Australian National Electricity Market” by Elliston et al. (2011a) (henceforth EDM-2011).  That paper does not analyse costs, so I have also made a crude estimate of the cost of the scenario simulated and three variants of it.

For the EDM-2011 baseline simulation, and using costs derived for the Federal Department of Resources, Energy and Tourism (DRET, 2011b), the costs are estimated to be: $568 billion capital cost, $336/MWh cost of electricity and $290/tonne CO2 abatement cost.

That is, the wholesale cost of electricity for the simulated system would be seven times more than now, with an abatement cost that is 13 times the starting price of the Australian carbon tax and 30 times the European carbon price.  (This cost of electricity does not include costs for the existing electricity network).

Although it ignores costings, the EDM-2011 study is a useful contribution.  It demonstrates that, even with highly optimistic assumptions, renewable energy cannot realistically provide 100% ofAustralia’s electricity generation.  Their scenario does not have sufficient capacity to meet peak winter demand, has no capacity reserve and is dependent on a technology – ‘gas turbines running on biofuels’ – that exist only at small scale and at high cost.

Map of Australia's transmission lines. There are no transmissions lines to any of the proposed CSP sites, and the best solar areas are far removed from the existing transmissions infrastructure.Source: Grattan Institute, Figure 10.1 (attributed to DRET (2010), Grattan Institute)

Introduction

I have reviewed and critiqued the paper “Simulations of Scenarios with 100% Renewable Electricity in the Australian National Electricity Market” by Elliston et al. (2011a) (henceforth EDM-2011).

This paper comments on the key assumptions in the EDM-2011 study.  It then goes beyond that work to estimate the cost for the baseline scenario and three variants of it and compares these four scenarios on the basis of CO2 emissions intensity, capital cost, cost of electricity and CO2 abatement cost.

Comments on the EDM-2011 study

The objective of the desktop study by EDM-2011 was to investigate whether renewable energy generation alone could meet the year 2010 electricity demand of the National Electricity Market (NEM).  Costs were not considered.  The study used computer simulation to match estimated energy generation by various renewable sources to the known hourly average demand in 2010.  This simulation, referred to here as the “baseline simulation” proposed a system comprising:

  • 15.6 GW (nameplate generation capacity) of parabolic trough concentrating solar thermal (CST) plants with 15 hours thermal storage, located at six remote sites far from the major demand centres;
  • 23.2 GW of wind farms at the existingNEMwind farm locations – scaled up in capacity from 1.5 GW existing in 2010;
  • 14.6 GW of roof-top solar photovoltaic (PV) inBrisbane,Sydney,Canberra,MelbourneandAdelaide;
  • 7.1 GW of existing hydro and pumped hydro;
  • 24 GW of gas turbines running on biofuels;
  • A transmission system where “power can flow unconstrained from any generation site to any demand site” – this theoretical construct is termed a “copperplate” transmission system.

The accompanying slide presentation by Elliston et al. (2011b), particularly slides 5 to 12, provides a succinct summary of the objective, scope for their simulation study, the exclusions from the scope, the assumptions and the results.

The results of the baseline simulation show that there are six hours during the year 2010 when demand is not met, with a maximum power supply shortfall of 1.33 GW.  It should be noted that the supply shortfall would be significantly greater with higher time resolutions, e.g. 5 minute data rather than the 1 hour increments used, but this limitation is not addressed by EDM-2011.

The EDM-2011 approach is more realistic than Beyond Zero Emissions (2010) “Zero Carbon Australia – Stationary Energy Plan” (critiqued by Nicholson and Lang (2010), Diesendorf (2010), Trainer (2010) and others), especially because EDM-2011’s approach, as they say, “is limited to the electricity sector in a recent year, providing a more straight forward basis for exploring this question of matching variable renewable energy sources to demand.”  As the authors say, “this approach minimises the number of working assumptions”.

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Burning energy questions – ERoEI, desert solar, oil replacements, realistic renewables and tropical islands

Posted on 19 January 2012 by Barry Brook

Late last year, Tom Blees, I and a few other people from the International Award Committee of the Global Energy Prize answered reader’s energy questions on The Guardian’s Facebook page. The questions and answers were reproduced on BNC here. Now we’re  at it again, this time for the website Eco-Business.com (tagline: Asia Pacific’s sustainable business community). My section is hosted here (Part I), and Tom’s here (part III).

Part II, which I don’t reprint, answered by Iceland’s Thorsteinn Sigfusson, covered the relationship between large-hydro and climate change, and why solar conversion isn’t used more extensively.

I’ve reproduced my and Tom’s answers below.

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Barry Brook’s Q&A

Sunil Sood: What are the “Real Energy Payback Periods” for Solar PV and Wind Energy Systems? Taking in to account the energy consumed during manufacture of components, balance of systems, transportation, installation, servicing and variations in availability of energy and usage patterns, actual life expectancy (not theoretical).  Are we consuming more of ‘Dirty Coal’ to produce these so-called ‘Clean’ energies?

Calculating true energy paybacks are tough. Every energy system has initial investments of energy in the construction of the plant. It then must produce energy for a number of years until it reaches the end of its effective lifetime. Along the way, additional energy costs are incurred in the operation and maintenance of the facility, including any self-use of energy. The energy payback period is the time it takes a facility to “pay back” or produce an amount of energy equivalent to that invested in its start-up. A full accounting of energy payback includes not only the materials and energy that are input into the extraction (mining) and manufacturing processes, but also some pro-rata calculation for inputs into the factory that constructed the power generation facility, some estimate for human (worker) inputs, etc. As you can imagine, it can be difficult to fully integrate all possible inputs.

However, there are reasonable ballpark estimates for a range of technologies, including wind, solar PV, solar thermal and nuclear. Material inputs tells one part of the story, and some attempts are a standardized comparison are given here and here for a few technologies (wind, solar thermal, Gen III nuclear). As a short-cut for estimate of total energy-returned-on-energy-invested (ERoEI), we can use studies that have looked at the life-cycle emissions of alternative technologies, and then calibrate these against the emissions intensity of the background economy used to produce the technology. This gives us an approximate ERoEI. Based on a range of studies, the estimates range from 180 to 11 for Gen III nuclear, 30 for wind, 11 for solar thermal and 6 for solar PV. That is, your PV panels would repay their inputs 6 times over during their lifespan, and if they lasted on your roof for 25 years then the payback time is about 4 years. If a nuclear plant had a ERoEI of 50 and operated for 40 years, its energy payback time would be 10 months.

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Filed under: Emissions, Nuclear, Renewables | 27 Comments »

Global Energy Prize and Breakthrough Institute

Posted on 27 December 2011 by Barry Brook

Russian President Dmitry Medvedev at the 2008 International Global Energy Prize award ceremony

The Christmas to New Year period is traditionally ‘hibernation mode’ for blogs, when page views and comment counts plummet (my hits have dropped about 70% compared to early December!).

I suppose this is a time when people find better things to do than sit in front of a computer screen (family time, good food, beach/snow [depending on hemisphere], travel, reading, new games and toys, whatever). So during this activity lull, it’s as good a time as any to announce a few little personal triumphs.

Within the last month or so I received two tokens of recognition for my work in the sustainable energy space. To explain what, I reproduce below a short write-up done by the University of Adelaide’s media office. I’ve added a few relevant hyperlinks and cites, for further information.

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International recognition for Environment Professor

The University of Adelaide’s Professor Barry Brook — an environmental scientist who holds strong pro-nuclear energy views — has received recognition from two prominent international bodies.

Professor Brook, who is Director of Climate Science at the University’s Environment Institute, has become the first Australian appointed to the international award committee of the $1.2 million Global Energy Prize.

Known as the “Nobel Prize of Energy”, this is the most prestigious international award granted for outstanding scientific achievements in the field of energy that have benefited the human race. From Wikipedia:

The Global Energy Prize is an independent award for outstanding scientific research and technological development in energy, which contribute to efficiency and environmentally friendly energy sources for the benefit of humanity.

The award was established in Russia, through the non-commercial Global Energy partnership and with the support of leading Russian energy companies Gazprom, FGC UES and Surgutneftegaz. Laureates are presented with their award by the President of Russia.

The Global Energy Prize promotes energy development as a science and demonstrates the importance of international energy cooperation, as well as public and private investment in energy supply, energy efficiency and energy security. It stands for the belief that advances in science and technology should serve the long-term interests of human development, improving social security and living standards of people in all countries.

Barry Brook

Professor Brook has also been made a 2012 Senior Fellow at the California-based think tank, The Breakthrough Institute.

The Institute is dedicated to “modernizing liberal thought for the 21st Century” and creating “secure, free, prosperous, and fulfilling lives on an ecologically vibrant planet”.

Both appointments are in recognition of Professor Brook’s work on energy policy. He holds strong views on the use of nuclear energy and alternative energy systems from an economic, environmental and scientific point of view.

“I’m honoured to have been chosen for the international selection committee of the Global Energy Prize and as a fellow of The Breakthrough Institute within a short space of each other,” Professor Brook says.

“Although many environmentalists consider nuclear power to be somehow anti-environment, it’s my firm belief that nuclear energy actually offers a viable low-carbon, low-impact alternative that cannot be matched by other low-carbon solutions.

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Filed under: Hot News, Nuclear, Policy, Renewables | 34 Comments »

Draft Energy White Paper – Discussion Thread

Posted on 14 December 2011 by Barry Brook

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Guest post by John Morgan. John runs R&D programmes at a Sydney startup company. He has a PhD in physical chemistry, and research experience in chemical engineering in the US and at CSIRO. He is a regular commenter on BNC.

Energy minister Martin Ferguson has today released the Draft Energy White Paper 2011 (The Australian, ABC). The Government is soliciting submissions , so with a quick review, I’d like to open some discussion on possible material for a submission.

So what’s in the white paper? In short, lots of new gas development, energy market privatization, and “…the Gillard Government unambiguously does not support the use of nuclear energy in Australia”.

But Ferguson does seem to be determined to inject some ambiguity into the matter. Elaborating on this unambiguous position he explained:

Nuclear for Australia is always there as an option. We don’t have to invest in R and D and innovation on that front. Other nations are the specialists. But if we get to the end of this debate some years in the future and we haven’t made the necessary breakthrough on clean energy at a low cost outcome, then nuclear is there for Australia to blow off the shelf after a debate in Australia.

His Opposition counterpart Ian Macfarlane is singing from the same song sheet:

We haven’t had any active consideration of nuclear energy in Australia but the fact remains that nuclear energy is the one base load technology that is clean energy and until we find a better alternatives to clean, zero-emission energy than nuclear, then it’s going to remain on the agenda of other countries.

And of course the Greens are furious.

The white paper itself expresses this unambiguous position in remarkably equivocal terms. The full position on nuclear power is buried right at the back of the document on page 223 in a text box aside from the main text, where it is offered as a ‘contingency’ consideration. I will quote this in full:

• Australia’s plentiful natural endowment of a range of low‐cost energy resources has played a major role in shaping our energy generation base around coal and gas.

• Other countries have chosen to adopt nuclear power often as a way of diversifying their energy mix. As one of the world’s largest uranium exporters, Australia has respected and supported this right through trade under strict safety and security safeguards. Nuclear‐powered electricity generation currently produces around 16 per cent of the world’s electricity – around 10 times Australia’s total annual electricity generation. Undeniably this results in lower global carbon emissions.

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Filed under: Nuclear, Policy, Renewables | 82 Comments »

The Guardian questions: thorium, shale gas, off-grid renewables, and much more…

Posted on 11 December 2011 by Barry Brook

The Guardian newspaper’s Environment Facebook page recently put the following to their readers:

Ask the Global Energy Prize‘s expert panel your toughest energy questions and they’ll be back here on Friday with their answers. What should power our cities, homes and industry in the future — renewable energy, nuclear power, or fossil fuels? How significant will shale gas be? And what role will oil play in our energy future? Just post your energy Qs here. 5 experts will answer the 10 best questions: Harry Fair (US), Tom Blees (US), Thorsteinn Sigfusson (Iceland), Barry Brook (Australia) and Klaus Riedle (Germany).

Below are the six questions put to me (Barry Brook) and Tom Blees — and our answers, of course! The original answers were not hyperlinked, but if you are curious about anything we mention here, try searching for the keywords on this website (e.g. type bravenewclimate.com/?s=thorium in your browser address bar), or on Google (e.g. type  ”ammonia site:bravenewclimate.com” in your search box).

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BARRY W. BROOK

Q1. Do you agree that Thorium power is a safe, plentiful, and viable energy source that should be investigated as a matter of urgency?

Yes, thorium power is an attractive prospect for the next generation of nuclear reactors, but then surprisingly enough, so is uranium.

For today’s reactors, it takes about 150 tonnes of natural uranium to fuel a 1 gigawatt (GW) power plant for an entire year (the total energy produced is called a gigawatt year, or GWyr).  One GWe of power (the ‘e’ stands for electrical power rather than ‘t’ for thermal power, or heat) is a huge amount. It’s enough to run 65 million desk lamps (assuming they used 15 W compact fluorescent globes), or more practically, to satisfy today’s electricity demand of a typical UK city of more than half a million people. For comparison, to deliver a GWyr of energy using a coal-fired power station, about 4 million tonnes of coal must be burned (the amount can vary depending on the grade of coal).

Most of the nuclear power stations in use today are called ‘thermal reactors’, or ‘light water reactors’ (LWR). They use ordinary (‘light’) water as a coolant, which take heat away from the reactor core. The water also acts as a ‘moderator’, slowing down subatomic particles called neutrons, which shoot out of the atom’s nucleus when a nuclear chain reaction is underway. These neutrons are responsible for causing unstable heavy atomic nuclei to split apart and release energy. Other reactor designs use heavy water (enriched in ‘heavy hydrogen’: deuterium) or graphite (a form of carbon found in pencils) to moderate the neutrons (the latter is used in the UK’s gas-cooled Magnox reactors, for instance), but the effect is similar. These nuclear power plants need, as fuel, a form (isotope) of uranium that has 143 neutrons in its nucleus, called 235U (or ‘uranium 235’). Yet natural uranium contains 0.7% 235U; the other 99.3% is composed of an isotope that has 3 additional neutrons, called 238U (or ‘uranium 238’). As a result, today’s LWRs are able to extract less than 1% of the atomic energy content of uranium. The rest is discarded, unused, either as spent fuel (‘nuclear waste’) or as depleted tails (the leftovers, composed mostly of 238U, after the fuel has been ‘enriched’ to raise the concentration of 235U to 3 – 5%).

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Solar combined with wind power: a way to get rid of fossil fuels?

Posted on 30 November 2011 by Barry Brook

Guest Post by Jani-Petri Martikainen. Jani-Petri is a theoretical physicist doing fundamental research in the field of ultracold quantum gases. Most of his current research activities are computational and involve bosonic or fermionic atoms in optical lattices. He has a lively interest on environmental, climate, and energy issues. He runs the blog PassiiviIdentiteetti, which is mostly written in Finnish.

Jani’s previous post, Geographical wind smoothing, supergrids and energy storage, focused on distributed wind alone. In this follow-up, he turns his attention to solar combined with wind.

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Earlier, I wrote on how crucially an unreliable sources of power such as wind depend on fossil fuels. Based on real world production data from around the world, I noted that even with massively distributed production wind power is very variable and necessitates a reliable backup power source (typically from fossil fuels) which must be able to produce essentially all the power society consumes. A way around this problem would be a massive energy storage, but I found the size of the required storage to be unreasonably large.

One typical response to findings such as these, is to brush them aside by claiming that even if true, the results will not matter since we will have many different renewable energy sources acting together (as if there is some “harmony” in two essentially random signals). Most importantly quite a few people base their vision of future energy production on a mixture of wind and solar power. For this reason I felt the need to return to this problem so that also solar power is considered. Unfortunately, I have yet to find a good source for real world production data for solar power. The best I have come up with are images (typically of the daily production), but raw data is better hidden.

However, since solar power (without storage) production is proportional to insolation we can use meteorological data as a reasonable starting point. US has a National solar radiation database which has large collection of insolation modelling data around USA. From this data they have also formed a “typical meteorological year 3 (TMY3)” datasets. (There are some quirks in the construction of TMY3 that I frown upon. For example, after El Chichón and Mount Pinatubo eruptions insolation was reduced, but these periods were apparently excluded from the TMY3 as atypical. Of course they were atypical, but they are still things that do happen and whose effects must be considered. However, I suspect that the effect due to eruptions was still minor in US.) As my insolation data I take the average of TMY3 data from six different class I sites (class I has the best data) in three different states: Prescott Love and Tucson Airport in Arizona, Arcata Airport and Fresno Yosemite Airport in California, and Denver Airport and Limon in Colorado. These sites have an average latitude similar to southern Spain. (Why did I choose these sites? Well, being lazy I started from the entries listed in alphabetical order by states and picked the first southern states I encountered.)

Somewhat annoyingly only hourly data is provided. We know from BNC among others that solar power (especially PV) can have large swings on shorter timescales. Therefore, this limitation may have important consequences. Nevertheless, let us ignore the torpedoes with an understanding that the solar power we talk about here is such that sufficient storage has been already implemented to smooth out hourly variation in production. So keep in mind, that the starting assumptions for solar production have a bias towards the optimistic side. Since the production data for wind power is given every 5 minutes I will linearly interpolate the solar insolation data to deduce the production of solar power every 5 minutes (link to the data here). As in the earlier study the data corresponds to one year starting July the 1st. and the consumption data corresponds to the Bonneville Power Authority load with a possible scale factors to suit my needs.

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Filed under: Emissions, Renewables | 114 Comments »

Energy Storage Discussion Thread

Posted on 13 November 2011 by Barry Brook

For high-penetration utility-scale wind, we'll need much bigger batteries than these...

Debate over large-scale energy storage is a regular theme in the comments on this blog. The post is intended to be a place to centralise this discussion. Some questions that might be considered in the comment thread:

1. What is the cost (per Watt hour, kWh, MWh, GWh — how does this cost scale up, and how does this scale as higher levels of reliability are required, e.g. energy delivered on demand 90% vs 99% vs 99.9% of the time)?

2. What is the energy density of the proposed storage technology currently, and what are its physical limits? (i.e., how good can it get, with perfect engineering, and how long can the energy store be held?)

3. If the storage technology becomes cheap, what is to stop baseload plants like coal and nuclear from undercutting renewables, given that they can charge large batteries in low-demand times and then sell the power during peak (high-price) periods?

4. What are the material inputs for the storage system, and how does this effect the energy returned on energy invested of the paired energy technology (e.g., what is the EROEI and life-cycle CO2 emissions of, say, a 2kW solar PV system with no storage vs the same system with 10 hours battery storage to cover nights [ignoring winter and long cloudy periods])?

5. Lifetime: how many cycles can the storage technology handle (100, 10,000, near-indefinite [e.g. conversion to hydrogen])?

6. Does the storage technology need its own power-generation system, or can it be paired to the original generating technology (e.g., a molten salt heat storage can create steam for use in the same turbine set as the solar thermal plant itself, whereas compressed air energy storage for wind requires a different generation system to the wind itself)?

(If people can propose some other general questions, I’ll add them to this list)

Anyway, to kick the discussion off, here is something sent to me by George Stanford, in response to the following missive:
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Filed under: Nuclear, Renewables | 214 Comments »

CO2 abatement cost with electricity generation options in Australia

Posted on 2 November 2011 by Barry Brook

Guest Post by Peter Lang. Peter is a retired geologist and engineer with 40 years experience on a wide range of energy projects throughout the world, including managing energy R&D and providing policy advice for government and opposition. His experience includes: coal, oil, gas, hydro, geothermal, nuclear power plants, nuclear waste disposal, and a wide range of energy end use management projects.

A 10-page printable PDF version of this post can be downloaded here.

An Excel worksheet showing the calculations (allowing you to change inputs/assumptions) is also available.

Introduction

What is the cost of carbon dioxide (CO2) emissions abatement with the various electricity generation technologies being considered for Australia?

The abatement cost of a technology depends on many factors such as the engineering characteristics of the electricity grid to which the new technology will be connected, the geographic location and many others.  One important factor often not mentioned is the reference case against which the abatement cost is calculated.  The abatement cost for a new technology is only meaningful when compared with another new technology or with an existing generator it would ‘displace’; e.g. nuclear compared with a new coal power station or nuclear compared with an existing power station.

The Electric Power Research Institute (EPRI, 2010) report http://www.ret.gov.au/energy/Documents/AEGTC%202010.pdf for the Australian Department of Resources, Energy and Tourism provides data that allows CO2 abatement costs to be estimated for a range of new technologies. Unfortunately, the report is complex and opaque in parts.

The purpose of this paper is twofold:

  1. to summarise in tabular form the relevant information from the EPRI report so others can access it easily and produce levelised cost of electricity (LCOE) figures under differing assumptions, particularly using the NREL LCOE calculator http://www.nrel.gov/analysis/tech_lcoe.html .
  1. to calculate and compare the CO2 abatement costs for a range of new technologies for each of three ‘displaced’ technologies.

This paper does not attempt to calculate the effects of carbon price on the LCOE or CO2 abatement costs, because:

1)     the EPRI report does not include the effects of carbon price — nor feed in tariffs, renewable energy certificates and other subsidies — so incorporating the effect of CO2 pricing, and other incentives and disincentives in the analysis would require many additional assumptions, and

2)     the purpose of this paper is to show the abatement costs for the various technologies so options can be compared and so the cost of incentives and disincentives (including carbon pricing), which would be needed to make each technology viable, can be made visible.

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Filed under: Emissions, Nuclear, Policy, Renewables | 262 Comments »

Geographical wind smoothing, supergrids and energy storage

Posted on 29 October 2011 by Barry Brook

Guest Post by Jani-Petri Martikainen. Jani-Petri is a theoretical physicist doing fundamental research in the field of ultracold quantum gases. Most of his current research activities are computational and involve bosonic or fermionic atoms in optical lattices. He has a lively interest on environmental, climate, and energy issues. He runs the blog PassiiviIdentiteetti, which is mostly written in Finnish.

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For quite some time I have been troubled by the difficulty of finding open and sensible discussions on energy scenarios where erratic energy sources such as wind and (somewhat less erratic) solar provide the bulk of the power produced. Proponents of such alternatives routinely talk as if scaling such energy sources up to significant levels poses no insurmountable challenges or costs that the society cannot afford. One can often read claims such as:

By aggregating power generation from wind farms spread across the whole (North Sea) area, periods of very low or very high power flows would be reduced to a negligible amount. A dip in wind power generation in one area would balanced by higher production in another area. European renewable energy council and Greenpeace (page 34).

Strangely, proponents feel comfortable in making such statements, but show a noticeable lack of interest in actually demonstrating whether the statements are true. Why is this? In science the burden of proof falls upon the claimant and it would be desirable if the same  principle were to apply to discussions about energy policies. (Notice by the way, that EREC+GP are not even satisfied with claiming that wind speeds in different parts of the North Sea are uncorrelated, but actually claim that speeds are anti-correlated.)  Why is it, that an amateur like me [in energy analysis] feels the need to do his own computations to figure out such issues rather than just being able to read proper studies online?

Since it appears difficult (certainly outside academic journals) to find detailed numbers on how strongly, for example, wind power actually relies on fossil fuels, I decided to do some estimates myself. I am not primarily interested in cosmetic amounts of wind power production, but will take the ambitious renewable visions seriously and study scenarios where wind power would be enough to power our entire society. I want to understand to what extent electricity production in such scenarios still relies on reliable energy sources and what kind of energy storage is required to enable wind power to stand on its own feet. Since hydropower capacity at a global level is limited, I will mostly use the term “reliable energy source” as an euphemism for fossil fuels. Not to be too parochial and allow for massively distributed generation,  I will assume a “super(duper?)grid” coupling wind power sources from three different continents together.

As a starting point I want to create a production profile based on real wind power production data. As sources I choose south-eastern Australia, Ireland, and the Bonneville Power Administration in Oregon, US. Each has roughly comparable amounts of wind power installed, but I will scale the capacity of each to 3333 MWe so that the combined capacity will end up being 10 GWe (peak). Data for BPA and Australia is given every 5 minutes while the Irish data is every 15 min.

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Filed under: Emissions, Renewables | 104 Comments »

TCASE 15: Comparison of four ‘clean energy’ projects

Posted on 21 October 2011 by Barry Brook

How can we compare the cost, performance and value-for-money of alternative large-scale clean energy projects? Actually, it’s pretty tough to try and avoid apples-and-oranges comparisons. Still, some adjustments can be made, such as for capacity factor, to partially levelise comparisons.

Below is a simplified comparison of four recent real-world projects. All can be considered first-of-a-kind installations, except for the wind farm.

1. A large proposed wind farm in South Australia (600 MWe peak)

The wind project will use 180 of the 3.4 MWe Suzlon turbines and “generate enough electricity to power 225,000 homes“. It includes a biomass plant that could produce up to 120 MWe of backup power to cover low-wind periods, and might offset up to 2.5 million tonnes of CO2 per year. At average 8m/s winds the capacity factor is estimated to be about 35%. A 60 km undersea high voltage direct current cable will connect it with Adelaide. Cost is $1.3 billion for the generating infrastructure and $0.2 billion for the cable.

2. A large Generation III+ nuclear power plant in Finland (1600 MWe peak)

The in(famous) Olkiluoto 3 NP unit, a European Pressurised Reactor (EPR) being built by the French (AREVA). The project has seen significant delays (first electricity now expected in 2014), and a cost blowout from the original € 3.7 billion to a new figure of € 6.4 billion. Despite this, the Fins have ordered two more EPR units. Assume it runs at the average Finnish capacity factor of 86%. 

3. A large solar PV plant under construction in New South Wales (150 MWe peak)

To be built in Moree, this will cover 3.4 km squared with 645,000 multi-crystalline PV panels, and is forecast to output 404 GWh per year (enough for 45,000 households). Part of the “Solar Flagships” programme, the cost is $A 923 million. Estimated to abate 364,000 tonnes of CO2 per year (based on NSW emission factor 0f 0.9 tCO2/MWh). Estimated capacity factor is 30.7% (based on peak power and GWh forecasts) — this seems high compared to typical PV performance.
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Filed under: Nuclear, Renewables, TCASE | 150 Comments »

Coal dependence and the renewables paradox

Posted on 25 September 2011 by Barry Brook

In a recent issue of Dissent magazine, a regular commenter here on Brave New Climate, industrial engineer Graham Palmer, engaged in a debate with Mark Diesendorf on energy futures. Unfortunately, this exchange of prose is not available online, although Graham did send me a scanned version (because of potential copyright issues, I won’t post it here). The promo from Dissent was as follows:

Mark Diesendorf says that nuclear energy is a very dangerous, complicated and expensive way of boiling water which is not a sensible alternative to renewable energy in the production of base-load electricity.

Graham Palmer argues that because base-load electricity cannot be stored and wind and solar power are dependent on the wind and sun, renewable energy must be backed up by fossil or nuclear base-load capacity.

Fortunately, Graham also delivered a condensed version of his side of the debate to a national radio audience this weekend, via Robyn William’s ABC show Ockham’s Razor. With Graham’s permission, I’ve reproduced the transcript of his essay below (with a few hyperlinks and relevant pictures added), because I think it provides a useful context for discussion on the BNC blog. I trust you’ll find it interesting.

Coal dependence and the renewables paradox

(by Graham Palmer)
Listen to audio MP3 reading by Graham, here (6.5 MB, 14 min)

Just about everyone agrees that the most pressing challenge in averting climate change is reducing our dependence on coal. Like most environmentalists, I used to pretty much go along with the idea that a combination of wind and solar, combined with serious energy efficiency policies, could probably go a long way towards achieving that aim in the long term. But after two decades of intense international efforts, we seem to be running fast but actually getting nowhere. And growth in coal continues unabated. Even countries like Denmark and Germany, that have invested heavily in renewables over decades, despite managing modest relative reductions in emissions, have not found a way to displace their base-load coal with wind and solar. Indeed, despite around 100,000 wind turbines globally, and enormous investment in solar, there is not a single example anywhere in which a coal plant has been retired as a direct result of the installation of wind or solar. So what’s going on? To answer this, requires stepping back to 1865, and re-examining Stanley Jevons economics classic, The Coal Question.

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Filed under: Emissions, Nuclear, Renewables | 194 Comments »

What is your energy philosophy?

Posted on 31 August 2011 by Barry Brook

People seem to like to infer motives. (Perhaps it’s an inherent evolutionary trait, allowing anticipation of your prey’s or predator’s next move?) I find that a lot of people get me wrong about my position on energy and sustainability — often deliberately so, I suspect. So here’s a post to clarify my position, and allow you to let others know about your philosophy (in the comments below).

Consider this a personal view, but one I would justify as being informed by extensive reading, talking and thinking. It doesn’t mean I’m right, just that I’ve made the effort to properly contemplate. I think that’s all you can ask of anyone — you, or the people you’re debating!

General philosophy: Anthropogenic climate change is a very urgent problem — probably the most serious one now facing humanity. We must solve it: there is no choice here and hiding our heads in the denial sandpit is pointless. We must also deal with other issues of global sustainability, especially clearance and degradation of tropical landscapes, overfishing, fragmentation of natural habitats within urban-agricultural areas, and chronic pollution from fossil fuel combustion. Most of these problems have common solutions, centred on the need for abundant clean and sustainable energy (not less), ‘techno-fixes’, stabilisation of population, provision of viable economic and agricultural systems, and a functioning, realistic and pragmatic society. We need to use all practical, cost-effective and timely options at our disposal.

Climate change: Human activity, via the burning of fossil fuels and also through agricultural and forestry changes, is almost exclusively (>95 %) responsible for the substantial global warming witness in the last 3-5 decades (+0.5C). It is also mostly (>70%) responsible for the warming since 1910 (+0.8C in the last 100 years). The most likely trajectory for the next 40 years (through to 2050) is an additional +1.2C (to +2C compared to pre-industrial), and a further +3C by 2100. There is some (low) probability that feedbacks in the climate system will double the 2100 estimate (or more) — much as I’d like to, I cannot dismiss this possibility. Sea level rise by 2100 will be > 1 m, and will continue for centuries thereafter (probably >10 m by 2300). Some of this may be avoidable, but I doubt it — especially the +1.2C warming between now and 2050 and the ongoing sea level rise. We’re just too far committed to a fossil-fuel-intensive pathway now and for the next few decades, and it will take substantial time to ‘turn the ship around’. There is plenty of hurt on the way — we can adapt to some of it, but many impacts will be difficult to ameliorate.

Peak fossil fuels: We are depleting accessible supplies of coal, oil and gas substantially, and peak global production of traditional sources will almost certainly arrive within the next few decades — probably sooner rather than later (although locally, they will continue to be abundant, e.g. coal in Australia). This will increase extraction and processing costs, which will in turn spur increasing exploitation of unconventional supplies, including underground gasified coal, coal seam methane, fracked shale gas, tar sands and Arctic hydrocarbons. It may be that demand will outstrip supply by about 2030, after which there will be an increasingly compelling reason to manufacture synthetic fuels such as ammonia, methanol and (I hope), serious investigation of boron as an energy carrier. Carbon prices will accelerate this decision. Peak fossil fuels will not, in and of itself, lead to significant greenhouse gas abatement this century. Too little, too late.

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Filed under: Future, Nuclear, Renewables | 189 Comments »

TCASE 14: Assessment of electricity generation costs

Posted on 17 August 2011 by Barry Brook

In the previous TCASE post, I considered how various low-carbon energy technologies meet the following criteria: commercial readiness, scalability, dispatchability, fuel constraints, load access, storage requirements, capacity factor and emissions intensity. Here I consider the next issue: cost of deployment, based on expert consensus.

Emission intensity for fit-for-service baseload electricity generating technologies. Error bars represent 90% confidence intervals for the mean (bar height). NOTE: PF Coal = Pulverised fuel black coal, CCGT = Combined cycle gas turbine, IGCC = Integrated gasification combined cycle, CCS = carbon capture and storage, FOAK = first of a kind, CC = combined cycle.

The primary data again come from the work I had published in 2011 in the peer-reviewed journal Energy (with colleagues Martin Nicholson [lead author] and Tom Biegler). Cost was analysed on the basis of 15 comprehensive levelised cost of electricity studies published over the past decade. The data are as follows (see also figure above), with references given in the footnote:

(LCOE = levelised cost of electricity (in 2009 US$/MWh) — see footnotes for a more detailed explanation.)

Enthusiastic supporters of various renewable energy technologies have long made claims that all or most of the world’s electricity needs could be met with renewable energy. Our analysis point to the costs involved and hence to the reliance on future major advances on that front in order to be competitive with other, low-emission, alternatives. In our view such reliance is highly speculative and risky as part of any plan to secure future energy.

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Filed under: Emissions, Nuclear, Policy, Renewables, TCASE | 91 Comments »

TCASE 13: Assessment of suitability of technologies for carbon dioxide mitigation

Posted on 12 August 2011 by Barry Brook

The problem of replacing our dependence on fossil fuels is complex. In Thinking Critically About Sustainable Energy (TCASE) #12, a checklist was provided to allow assessment of energy transition plans. The sort of questions listed in TCASE 12 are critical for evaluating the feasibility of future scenarios, like the ones from the recent IPCC report on renewable energy.

However, we also need to assess the capabilities of individual technologies to mitigate CO2 emissions, effectively (and economically). The following is a list of criteria that can be used to determine the relative viability of various alternative technologies. This comes from the work I had published recently in the peer-reviewed journal Energy (with colleagues Martin Nicholson and Tom Biegler):

Proven: Has the technology been used at commercial scale?

Scalable: Can the technology be built in sufficient quantity to replace significant proportions of existing fossil-fuel generators?

Dispatchable: Can the output be allocated by the system operator to meet the anticipated load?

Fuel supply: Is the energy source reliable and plentiful, even when, as with some kinds of renewable energy, it varies with time?

Load access: Can the generator be installed close to a load centre?

Storage: Does the technology require electricity storage in order to deliver a high capacity factor?

Emission intensity: Is the emission intensity high, moderate or low (as defined in the table below)?

Capacity factor: Is the capacity factor high, moderate or low (as defined below)?

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Filed under: Emissions, Nuclear, Renewables, TCASE | 86 Comments »

A critique of the 2011 IPCC Report on Renewable Energy

Posted on 9 August 2011 by Barry Brook

The following is a detailed guest post by Dr Ted Trainer, University of NSW (http://ssis.arts.unsw.edu.au/tsw/). In it, he provides the most detailed critique I’ve yet seen of the recent IPCC renewable energy scenarios report. Now, I don’t agree with everything Ted says — in particular the conclusion that the only feasible alternative to large-scale renewables is “The Simpler Way” — but that’s another matter.

His analysis of the report is important and robust, and deserves wide dissemination. Ted is also looking for critical feedback, so please supply this in the comments at the foot of this BNC post.

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Preamble, by Ted Trainer

Below is a critical discussion of the recent IPCC Working Group 3 Report on Renewable Energy. It is being referred to as a report from many experts showing that the world can be running mostly on renewable by 2050.

However I think it is a remarkably unsatisfactory document. Following are some of the main points I detail.

• It is not a report on an examination by the IPCC of the potential of renewables. It is a statement of the conclusions evident in 164 studies, which were not selected at random. The IPCC does not evaluate these studies; we do not know how valid their conclusions are.

• What the IPCC actually concludes is that more than half the studies reviewed project that renewables could provide more than 27% of energy in 2050. Again, the IPCC does not inquire as to whether such projections are sound.

• There is no reference to the studies I know of that doubt the potential of renewable energy.

• Even if this conclusion could be regarded as well-established it would fall far short of solving the greenhouse problem. According to the IPCC’s own figures it would leave us with a higher CO2e emission level than we have now. Yet the Report’s air is one of optimism.

• In the key Chapter 10 most attention is given to one study which concludes that by 2050 70% of world energy could come from renewables. This study, by Greenpeace, is highly challengeable. It does not establish its claims, and it fails to discuss a number of problems confronting renewable energy.

• The brief reference to investment costs is not derived or supported, and is highly challengeable. I sketch three approaches indicating that the cost would be far higher than claimed, and not affordable.

The document is puzzling. It does not do what it should have done, and is being taken to have done, i.e., critically examine as much of the evidence as possible on the potential and limits of renewable energy in order to derive demonstrably convincing conclusions which deal thoroughly with all the relevant difficulties. It does not advance the issue; it just summarises what some others have said, without assessing the validity of what they have said. Most difficult to understand is why it gives so much attention to one clearly problematic study, and allows its highly optimistic conclusions to be taken as those the IPCC has come to. It is likely that as the Report is examined it will damage the credibility of the IPCC.

The Report reinforces the dominant faith that renewable energy can save us and there is no need to question the commitment to affluent living standards and the pursuit of limitless economic growth. In my opinion that belief is seriously mistaken and this report will make it less likely that attention will be given to a sound analysis of our situation and what to do about it.

I should make it clear that my comments do not cast doubt on the IPCC’s statements re: climate science. It is also my view that we should transition to full dependence on renewables as soon as possible…although this will not be possible in a consumer-capitalist society.

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Filed under: Policy, Renewables | 96 Comments »

Hansen warns not to drink sustainable energy Kool-Aid

Posted on 5 August 2011 by Barry Brook

Regular readers of BNC would know that I’m hardly the only climate change researcher to recommend serious deployment of nuclear energy to displace fossil fuels. (Although I’m often portrayed as an isolated [and presumably therefore ignorant?] voice on this point). One very prominent example of a colleague in arms is my fellow SCGI member, Dr James Hansen (pictured left). Some call him the ‘grandfather of global warming‘. He’s an incredibly influential and important figure in science and advocacy circles around the issue of human-caused climate change. For instance, the 350.org initiative is based on his recommended number.

This guy ought to be taken seriously by any environmental ‘activist’ who wishes their case to be scientifically based and consistent. Yet, he’s being blithely ignored (or even denigrated) by the ’100% renewable energy will solve everything’ crowd and their anti-nuclear side-kicks. This is a shame, because he has some really important things to say on energy matters, as well as climate. He’s a polymath, and thinks big. He’s clever. He’s willing to speak out. We need more folks like Jim.

Below I reproduce a slightly abridged version of a recent essay by Jim on the topic of sustainable energy. I do so because: (i) its content matches so well the other material and arguments I’ve published on BNC; (ii) Hansen has featured on many other past posts (see list here); (iii) he’s a personal friend and IFR supporter, and I respect what he says; and (iv) it’s a great topic of conversation for readers. I look forward to your feedback and comments on Hansen’s piece. It should be read widely.

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Introduction

Today’s adults, unless they have a sudden change of heart, are preparing to leave young people a dynamic mess out of their control.

This is an odd situation. It is a wonder to see instinctive, sometimes frantic, reactions of many species as they try to protect their young from dangers. One would think that the intelligent species would have become particularly good at providing protection for their young, and that a democratic system would give that function high priority. But as our paper #3 (“The Case for Young People“) makes clear, governments are failing to protect the rights of young people to inherit a planet that preserves creation and preserves their equal opportunity for good lives.

A facile explanation would focus on the ‘merchants of doubt’ who have managed to confuse the public about the reality of human-made climate change. The merchants play a role, to be sure, a sordid one, but they are not the main obstacle to solution of human-made climate change.

The bigger problem is that people who accept the reality of climate change are not proposing actions that would work. This is important, because as Mother Nature makes climate change more obvious, we need to be moving in directions within a framework that will minimize the impacts and provide young people a fighting chance of stabilizing the situation.

Let me try to provide some insight about the problem via personal experience and simple charts for the United States and the world.

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Filed under: Emissions, Nuclear, Policy, Renewables | 91 Comments »

Germany’s grand energy experiment

Posted on 29 July 2011 by Barry Brook

Most readers of BNC know the story — after the Fukushima nuclear crisis, the German government announced that Germany would phase out all of its nuclear generation capacity by 2022. In almost the same period, Germany also aims to cut its national greenhouse gas emissions to 40% of 1990 levels (by 2020). Their emissions have already fallen by 22% since 1990, due in part to the reunification of West and East Germany and the subsequent closing down of the most polluting industrial and energy plants. So they have another 18% to go. Given the nuclear policy, can it be done?

According to this study by the Ecologic Institute (published prior to the nuclear shutdown announcement), Germany will have to initiative a range of aggressive measures, focused on energy efficiency, smart metering, car taxation, renewable energy heating systems, etc. etc. This was to make up a ‘gap’ compared to 2009 policies of 70 – 90 million tonnes (Mt) of CO2-e. The gap is now much larger.

Let’s look at the task ahead.

In 2010, 16.9% of Germany’s electricity came from renewable energy sources; nuclear provided 23.3%. The relative share, spread across renewable-based electricity (not final energy), is shown in the figure on the right. The installed renewable capacity was 55.7 GWe, producing 101.7 TWh of electricity, for an all-tech-averaged capacity factor of 20.8%. The aim is for renewables to provide 35% of electricity by 2020.

Nuclear provided 141 TWh of electricity in 2010. If this had come from coal instead (assuming an EI of 1.12 t/MWh), it would have produced about 158 Mt of additional CO2-e. Germany’s total emissions for 2010 were 960 Mt CO2-e, compared to 1230 Mt in 1990. The 2020 target is 740 Mt, with the remaining gap, to fill in the next 9 years, being 220 Mt. If we wipe out consideration of the now-to-be-retired nuclear fleet, that brings the ‘gap’ up to almost 380 Mt CO2-e.

Note that total final energy use in Germany in 2010 was 8,984 PJ, which is 2,495 TWh. So the economy-wide emissions intensity (EI) is 0.385 tCO2-e/MWh. This breaks down to a mix of 34.6% oil, 22.5% coal, 21.7% gas, 11% nuclear, 1.5% wind, 0.8% hydro, 0.9% solar and 7.9% biomass combustion. I calculate, based on standard EI values, that about 40% of Germany’s total 960 Mt CO2-e comes from oil emissions, 39% from coal, 20% from gas and ~1% from other.

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Filed under: Emissions, Nuclear, Policy, Renewables | 108 Comments »

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