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muoncounter at 05:22 AM on 13 July 2011The Medieval Warm(ish) Period In Pictures
scaddenp#22: "That said, I think Eric is onto a rich vein of denial memes" 'Warmer weather is good for glaciers' should have an especially good run. Our current warming must therefore be the teaser for the upcoming fourth Ice Age, which is scheduled for worldwide release in July 2012. Manny, Diego, and Sid - embark upon their greatest adventure after cataclysm sets an entire continent drift. Separated from the rest of the herd, they use an iceberg as a makeshift ship, which launches them on an epic seafaring quest. ... as they encounter exotic sea creatures, explore a brave new world, and battle ruthless pirates. -
KR at 05:18 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
Oh, in my previous post I should note that the 4 W/m^2 power density is for a 1000 kWh/yr site with 12% efficient cells - using current technology in a far from ideal location. Using 30% efficient CSP in a 2000 kWh/yr site (>230 Wh/m^2 average from MacKay, not the 200 BBD introduced), such as in the tropics, or even 20% efficient PV, the power density for solar will easily exceed strip-mined coal land use power density over a 30 year run. And coal, as we all know (as with all fossil fuels), is a limited resource... Again - area used does not hold up as an objection to solar power. May we now move on to other things? -
Tom Curtis at 05:12 AM on 13 July 2011What we know and what we don't know
Eric the Red @15, the last few years have shown a lower than usual growth in CO2 content because: 1) There was a decline in emissions in 2008 related to the Global Financial Crisis:
2) There was an increase in oceanic absorption of CO2, particularly in 2008, because of a strong La Nina.
Despite this the trend in the growth of CO2 concentration was positive over the period 2005-2009 (the last year in Tamino's analysis):
Let me emphasise that, even with the Global Financial Crisis and the coolest global temperatures in a decade, growth in CO2 concentrations was greater than linear. So unless you are projecting the GFK as the new economic norm, and 2008 temperatures or less as a constant feature for the coming decades, the last few years have had unusually low growth in CO2 concentrations relative to normal conditions.
If, instead of cherry picking aberrant conditions for your projections, you take the whole of the data, we can expect continued faster than exponential growth unless serious measures are taken to restrict emissions.
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KR at 04:58 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
There was a reference, Vaclav Smil 2010, along the way in this discussion, claiming that the power density of the Waldpolenz Solar Park (also mentioned along the way) was only just above 4 W/m^2, due to fill factor, inefficiencies, etc., and arguing that this was a reason not to go with renewable sources. This power density does turn out to be accurate. As a numbers check against the earlier LAGI discussion: Waldpolenz occupies 110 hectares, using 12% efficient cells, and generates ~40,000 MWh per year. 4*10^7 kWh/year, divided by 1.1*10^6 meters, comes out to about 36 kWh/m^2 per year. Divide that by the cell efficiency, 12%, and you see collectors are intercepting 303 kWh/yr, converting 12% as an end product. There may or may not be a factor of 0.85 in DC/AC conversion in this, meaning that the panels would be intercepting 356 kWh/yr. Insolation in Germany is about 1000 kWh/yr, meaning that for fixed PV panels the Waldpolenz effective fill factor, the sunlight intercepted, is >= 30% of total sunlight available.
A scaling factor of ~3 is therefore quite reasonable between collector area and plant area - even for simple fixed PV panels.
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Smil then compares this power density to that of coal - but only from deep mines, with 20T/m^2, leading to a power density per year of 2.5-4.8 kW/m^2. Strip mines (New Mexico figures) have a best case density of ~2T/m^2, which puts the power density in the 250-480 W/m^2 range per year.
So - in terms of land use, coal from deep mines (limited/expensive) is much more concentrated, but over a 30 year power production run, strip mines (the current preference) have an energy density of 8-16 W/m^2, only 2x-4x that of a 30 year solar power plant. And that coal land can never be used for coal production again - it's once through only.
Area used is just not a good argument against solar power.
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CBDunkerson at 04:55 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
Yeah, it is amazing that the 'land area' arguments against renewable power keep popping up... despite countless real world examples of dual purposing land so that wind power uses very little 'extra' space and solar power uses none. Solar panels are going up on the roofs of tons of large buildings across the United States: malls, warehouses, schools, et cetera. Some of these actually generate more power than they use and thus are not only decreasing their own future power bills, but becoming power plants for neighboring consumers. Large parking lots are another area currently seeing alot of solar development. I suspect that within a few decades it will be more common than not for these type of large structures to be solar covered. It just makes sense to profit from 'sunlight resources' on property which is already needed for other purposes. -
Dikran Marsupial at 04:52 AM on 13 July 2011What we know and what we don't know
Eric the Red You do realise the 1975 start date is a cherry pick? You have obviously chosen the start point to maximise the evidence for your hypothesis. Can I suggest that we abandon this topic of conversation. Eric seems to have quite neatly derailed the discussion of the topic of the article with pointless quibbling about whether the growth of atmospheric CO2 is exponential or linear, despite the fact that Tamino has already covered this with a much more solid analysis than Eric's (it even includes a test for statistical significance - take note Eric). -
BBD at 04:50 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KR It all boils down to which numbers you use for power density of plant (average raw energy density x plant conversion efficiency). As you point out at #300: (200W/m2 x 20%) x 24 x 365 = 350.4kWh/m2/year LAGI says 400kWh/m2/year. Completing LAGI's area calculation gets this: 198,721,800,000,000/350.4 = 567,128,424,657.5 or 567,128 km2 A 13.5% exaggeration. Still, not really enough to overturn LAGI. But After MacKay, using 15W/m2 for CSP: 15W/m2 x 24 x 365 = 131.4kWh/m2/year 198,721,800,000,000/131.4 = 1,512,342,465,753.4 or 1.5 million km2 After Smil, using 10W/m2 for CSP: 10W/m2 x 24 x 365 = 87.6kWh/m2/year 198,721,800,000,000/87.6 = 2,268,513,698,630.1 or 2.3 million km2 My problem is that I simply do not believe the power density estimates employed when people are talking up the potential vs footprint of renewables. And I have real-world data on my side. This has gone on for long enough (I'm sure if nothing else, we all agree on that). Given that MacKay calculates with a 100% packing factor while Smil looks at actual plant footprint, the truth is going to be somewhere above 2 million km2. A very big difference from 500,000km2. -
Eric the Red at 04:43 AM on 13 July 2011What we know and what we don't know
CB, Best to look at a moving average. I used a 5-year moving average, which has changed very little in 13 years; 2.00 in 1996, 1.98 in 2008, ranging from 1.74 to 2.14. The low values during the 1990s yield a misleading spike in the 2000s. This is the problem with cherry-picking values. -
Dikran Marsupial at 04:43 AM on 13 July 2011What we know and what we don't know
Eric the Red. You have got the situation 180 degrees the wrong way round. The reason we have statistics is because we are able to see in noisy data pretty much anything we wish to see. However being able to see some pattern in the data doesn't mean that it is meaningful rather than an artifact of the noise. Statistical hypothesis testing is one way in which we can guard against jumping to such conclusions. Your analysis did nothing to suggest that the hypothesised departure from exponential is anything other than an artifact of the noise. In short, you can do "more than that", you can devise some test that demonstrates that there is statistically significant evidence for your hypothesis. -
Albatross at 04:36 AM on 13 July 2011What we know and what we don't know
I sense something Monckton'esq going on here, and more strawmen arguments from contrarians to distract us from inconvenient truths...darn it I should be doing other stuff. Tamino has addressed this silliness here and here. He concludes: "CO2 has increased faster than exponential. Even using the shorter NOAA global dataset. And yes, the result is statisically significant." EOS. -
CBDunkerson at 04:34 AM on 13 July 2011What we know and what we don't know
Let's examine a 10 year running average; 1961-1970: 0.898 1971-1980: 1.336 (+0.438) 1981-1990: 1.547 (+0.209) 1991-2000: 1.545 (-0.002) 2001-2010: 2.043 (+0.498) From this we can see that there was a 'leveling off' in the 90s (mostly due to 1992 having the second lowest increase on record), but then increases accelerated in the 2000s. Note again that these are increases in the rate of increase... a linear rise would have these values staying steady. Instead, the most recent ten years show the largest increase in the series. -
Dikran Marsupial at 04:13 AM on 13 July 2011What we know and what we don't know
Eric, I wrote: "If you can show me an anlysis that robustly demonstrates that it is linear (rather than there just isn't enough data over shuch a short time span to distinguish between linear and exponential with statistical significance) then I am happy to stand corrected." You failed to do so, you still have failed to do so. Now I've had enough of this nonsense, TTFN. -
KR at 03:51 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
Tom - Agreed, the land cost is not a huge factor, especially with dual purpose land such as you show here. I actually suspect the major factors will be political, in the large scale grid interconnectivity needed to support distributed power generation, making it robust against weather variations, and in changing where the $$$ for power goes rather than to OPEC. I'm always puzzled by "we can't do it" objections such as the ones that have appeared in this thread. They just don't make sense. --- Side note/thought experiment: I think that if you set up rectangular mirrors trimmed from parabolic shapes, you could put them together with near zero waste space. Off vertical, each would partially shade neighbors behind it, but the full field area should still receive complete coverage. Again, though, land is relatively cheap, and you're going to want some room for servicing the collectors. -
Dikran Marsupial at 03:44 AM on 13 July 2011What we know and what we don't know
Eric the Red I like the "our point", most amusing. CBDunkerson's plot directly refutes your assertion that "The rise has been fairly linear since 1975.". That assertion is clearly incorrect, has been challenged, the challenge ducked and now you are trying to suggest that we had been making the same point! Your chutzpah is beyond belief! -
Tom Curtis at 03:38 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
Further to 301, exactly how much area of the Earth's surface should we count this Million kWh per annum solar power plant as occupying?It does not use a single square mm of land that is not already being used for another purpose. The opportunity cost of the roof area used is very close to zero. In North Africa, along the coast, if excess power production is used to run desalination plants, solar power plants may even have a negative opportunity cost. That is, they may actually increase the area of available arable land by providing water to allow arid land to be irrigated. Again, the point is that the idea that we should measure efficiency in terms of total plant area instead of total collector error is a serious distortion.
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Eric the Red at 03:27 AM on 13 July 2011What we know and what we don't know
Yes CB, that was our point. The rate of CO2 increase was increasing as your graph shows, but is now averaging about 1.8 ppm/yr. http://www.esrl.noaa.gov/gmd/ccgg/trends/Response:[DB] Looking at all of the data instead of the standard dissemblers cherry-picked start dates:
year ppm/yr
1959 0.94
1960 0.54
1961 0.95
1962 0.64
1963 0.71
1964 0.28
1965 1.02
1966 1.24
1967 0.74
1968 1.03
1969 1.31
1970 1.06
1971 0.85
1972 1.69
1973 1.21
1974 0.77
1975 1.13
1976 0.84
1977 2.10
1978 1.29
1979 1.75
1980 1.73
1981 1.43
1982 0.74
1983 2.17
1984 1.37
1985 1.27
1986 1.45
1987 2.33
1988 2.12
1989 1.31
1990 1.28
1991 0.98
1992 0.46
1993 1.36
1994 1.93
1995 1.93
1996 1.23
1997 1.92
1998 2.98
1999 0.90
2000 1.76
2001 1.57
2002 2.60
2003 2.30
2004 1.55
2005 2.50
2006 1.73
2007 2.24
2008 1.63
2009 1.89
2010 2.42
[Source]
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Tom Curtis at 03:25 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KR @300, I do not know of any actual designs, so no, I cannot provide links. But it is certainly possible to do. One potential design would be a field divided squares each filled by a fixed parabolic reflectors. A series of gantries could be mounted each field line of squares, able to track east or west to follow the focal point of each parabolic section during the day, with a carriage on the gantry carrying a sterling engine, and able to move north-south to track seasonal changes. Because the mirrors are fixed, they can be butted together with no gaps, except for the rail to carry the gantry. Is it practical? No. Is it economical? No. Can it be done? Yes. The point is the argument that we should measure our efficiency in terms of the land area of the plant (at $10 an acre, or whatever picayune price it costs in the Sahara) rather than in terms of the area of the collectors is nonsense. Land area is a factor in England, but primarily because the low solar intensity means greatly enlarged areas are needed for the same power generation. In Singapore and Hong Kong land area is definitely a factor, and I am happy to predict that we will never see a CSP plant in either. But even in farmland in Granada, Andasol considers land so small a relative cost that they could not even bother building the power plant and salt storage tanks underground to allow collectors to be run over the top of them. The cost per m^2 of land is not the limiting factor of solar power. The cost per m^2 of collectors is. -
CBDunkerson at 03:03 AM on 13 July 2011What we know and what we don't know
Actually, the rate at which the atmospheric CO2 concentration is increasing... is itself increasing;
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Albatross at 02:52 AM on 13 July 20112010 - 2011: Earth's most extreme weather since 1816?
For those still following this thread, The skeptics are misrepresenting Trapp et al's findings. Nowhere in their 2007 and 2009 papers do they even use the word "supercell". So no, they do not hypothesize that CAPE is the dominant factor in determining supercell formation as is claimed @330. Besides, severe weather can be caused by other types of thunderstorms (e.g., multicell, MCSs before they go upscale, squall lines, derechos etc.). Moreover, Trapp et al. state very clearly that they are identifying "severe thunderstorm environmental conditions". Their motivation for using the product of CAPE and 0-6 km wind shear is solidly rooted in theory and has been corroborated by empirical studies comparing proximity soundings to severe events. An interesting tidbit. Brooks et al. (2003) looked at the magnitude of the vector wind difference between the surface and 6 km (m s^-1) and CAPE (J kg^-1) for all reanalysis soundings associated with severe thunderstorms in US for 1997–1999. They found that as CAPE increased, the 0-6 km wind shear required to produce significant severe storms (i.e., hail of 5 cm or greater in diameter, wind gusts of 120 km hr^-1 or greater, or a tornado of F2 intensity or greater) decreased. The graph looks similar to the one below (sorry I have been unable to identify the source, nor find a suitable graphic that is not embedded in a PDF):[Source] Why this is, is an interesting story....but now I really do have to take care of some work.
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KR at 02:46 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD - How about you answer a question? ~225 W/m^2 daily hour average * 24 * 365 = ~2000 kWh/year/m^2. 1000 W/m^2 peak * 2000 hours effective peak available = ~2000 kWh/year/m^2 2000 kWh collected at 20% efficiency is 400 kWh/year. For both computations, when done right, as 2000 = 2000. You (repeatedly) claim the peak * peak available is incorrect - if so, why isn't the average hourly rate times the number of hours? Either both are right, or both are wrong. And, as the moderator stated, 'trickery' is not an appropriate term. If you cannot accept that you made an error here, BBD, I cannot expect that you will be an effective contributor to the various discussions. --- Tom - Thanks for pointing that out, I was not aware of field designs with zero waste space, although I knew parabolic trough designs get close to that. Any links you can point me to? -
Dikran Marsupial at 02:38 AM on 13 July 2011What we know and what we don't know
Eric the Red O.K. I see that you are merely trolling, as exemplified by the fact that rather than produce some evidence that the rise in CO2 is linear rather than exponential, or admit that you have no such evidence, you point out that linear is a special case of exponential as if that somehow made your point (rather than mine). Sorry Eric, life is too short. The idea that there is no essential difference between linear and exponential I'm sure will revolutionise the field of control theory! ;o) -
Tom Curtis at 02:37 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD @296, MacKay's method (not the standard method) only provides an accurate estimate of plant output for fixed horizontal collectors. For other types of collectors, different methods should be used, as detailed here. As can be seen below, different collection methods behave quite differently in terms of seasonal performance, and in terms of total power collected trhough the year:
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Eric the Red at 02:31 AM on 13 July 2011What we know and what we don't know
Yes Dikran, An exponential with a zero exponent is linear, so there is essential no different between the two. Using a continuation of past data works for the short term. At some point, the trend will change. We just do not know in which direction, how fast, or for how long. An example uses the 1970s prediction of mass starvation based on the exponential population increase and linearly rising food production. Nice quote. I need to remember that. -
CBDunkerson at 02:30 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD wrote: "Please clarify for me why LAGI's use of peak 1000W/m2 x 20% for every single sunlight hour in its calculation is not incorrect? LAGI assumes 8 hours per day and 250 sunshine days a year" The Sun only shines 8 hours a day and 250 days a year on your planet? You should move. It is much sunnier here on planet Earth. -
Tom Curtis at 02:28 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KR @294, your points are correct except for one. It is perfectly possible to design collectors with 2 axis tracking and zero waste space. There will be a loss of efficiency, but that will be inversely proportional to the size of the field and can be reduced to less than 5%. It is not economically worthwhile doing this because in most areas the land is so cheap relative to the cost of the collectors. Actually, LAGI's calculation of the minimum area needed is quite correct. ON the other hand, an estimate of three times LAGI's figures as the practical requirement is also valid, but only because economically, the land area is inconsequential as a cost (except in Singapore and other similarly crowded states). -
BBD at 02:20 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KREither ~225 W/m^2 daily hour average * 24 * 365, or 1000 W/m^2 peak * 2000 hours effective time at that peak = ~2000 kWh/year/m^2. Please clarify for me why LAGI's use of peak 1000W/m2 x 20% for every single sunlight hour in its calculation is not incorrect? LAGI assumes 8 hours per day and 250 sunshine days a year and cacluates: 8 x 250 = 2000 hours BUT it uses 2000 hours of 200W/m2 (eg peak mid-day) output: 2000 x 200 = 400,000 or 400kWh Which is wrong. I do not understand you point about mixing equations in #288. I used the standard method instead of LAGI's because the annual average energy density is a much better indicator of annual average plant performance (assuming a conversion efficiency is included). The average raw energy density x plant conversion efficiency will give the most accurate estimate of average plant output. That's why it's the standard method (eg MacKay) for obtaining them.
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Tom Curtis at 02:19 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD @292:"What I am doing avoids the trickery by LAGI, which uses peak for every single sunlight hour in its calculation."
Is that that same "trickery" that assumes there are only eight hours of daylight in any day? Or the same "trickery" that assumes that only 250 days of a year have clear skies in the Sahara? I don't see any complaints from you about LAGI's trickery that reduces the expected power generated. Regardless, as I have shown with the Albaquerque data, with 2-axis tracking, close to the equator you gain approximately the same energy for four hours on either side of noon. Hence there was no trickery from LAGI at all. -
KR at 02:10 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
Various readers - Given that solar power levels are presented in various formats, it's easy to miscalculate available energy due to a mis-conversion (as seen in this thread). The Wiki Insolation page, in the "Applications" section, has a conversion table that might be helpful in this regard. Given tropical insolation, and solar collection efficiencies of ~20%, roughly 500,000 km^2 of solar panels or CSP collection mirrors would supply an average of 23 TW to the world - sufficient for mid-century power supply including transportation. Note that there will be infrastructure (towers, supports, panel spacings, energy storage facilities, etc.) that enlarge this by some factor, but it's a reasonable estimate of what would be needed as collection area. Wind power follows similar calculations for area, and the Surface Area Required to Power the Whole World With Solar and Wind Power shows those at scale. Note that just solar or just wind isn't on anyone's horizon - nuclear, wave, geothermal, and biomass cann all make contributions as replacements for fossil fuels. But it at least gives some perspective. -
Tom Curtis at 02:07 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD @288, there is not a "correct method". There are just different methods. In what you call the correct method, an implicit assumption is that all solar collectors are laid horizontal to the ground, and are never tilted to track the sun. That is, of course, a false assumption. In contrast, the LAGI method assumes that the projected power plants will use collectors which track the sun both for season and for time of day (ie, on two axis). That is also a false assumption, but closer to the truth. Further, as the are calculating the minimum area required to provide the worlds power, it is the correct approach. In calculating the minimum, they do not assume that if all the worlds power was generated by solar (which they recommend against), that the minimum area will be in fact achieved. If we look again at the summer solstice clear sky data for Albaguerque, New Mexico (below), you will see that both two axis tracking collectors, and single axis tracking collectors orientated on the North-South axis both collect nearly the same energy throughout day light hours. Significantly, they collect nearly the same value as at noon for the four hours on either side of noon, ie, for eight hours a day. That fact justifies LAGI's method.
It is only if you assume the collectors will not track the sun during the day that LAGI's assumption is false. Indeed, during the winter solstice, a one axis tracking, N_S axis collector actually performs better during mid morning and mid afternoon than it does at noon (see chart @269 above). It should also be noted that the 2 axis tracking collectors do not perform as well in mid morning and afternoon as at noon (though much better than the N-S single axis tracking). That is because of the very low angle of the sun. Therefore LAGI's assumption only holds when the angle of the sun is not very low, ie, for sites in the tropics.
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BBD at 02:06 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
CBDunkerspnHowever, what you are doing is applying AVERAGE insolation for only the time per day and days per year when PEAK insolation is available. That is obviously incorrect.
The average includes the peak. What I am doing avoids the trickery by LAGI, which uses peak for every single sunlight hour in its calculation. That is obviously incorrect.Response:[DB] If you persist in casting aspersions of "trickery" to methodologies which give answers different to those methodologies which you employ, you will find it even more difficult to participate in this discussion...
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KR at 01:43 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD - OK, I'll try this one last time. Yearly power incident on a tropical site: Either ~225 W/m^2 daily hour average * 24 * 365, or 1000 W/m^2 peak * 2000 hours effective time at that peak = ~2000 kWh/year/m^2. Don't mix the equations, BBD, don't cross the streams. The same amount of energy can be computed either way. 2000 kWh/year/m^2, collected with 20% efficiency, is 400 kWh/year/m^2 power output. --- Now, using your method correctly, given 228 W/m^2 as a 24 hours a day average, 365 days a year (MacKay figures), * 20% efficiency = 45.6 W/m^2 average power year round. 45.6 * 1,000,000 m^2/k^2 * 500,000 km^2 = 2.28*10^13 = 22.8 TW. --- Please, BBD, correct your math - use one equation or the other, but stop mixing the two. Your math is wrong, your conclusions are therefore wrong; you're scaling 24 hour daily averages with the time that peak power is available. -
CBDunkerson at 01:37 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD: This is really quite simple. Either of the approaches below would be reasonable; 1000 W/m^2 peak insolation * 20% efficient panels * 8 peak hours per day * 250 peak days per year = 400 kWh OR 250 W/m^2 average insolation * 20% efficient panels * 24 hours per day * 365 days per year = 438 kWh However, what you are doing is applying AVERAGE insolation for only the time per day and days per year when PEAK insolation is available. That is obviously incorrect. -
Alec Cowan at 01:24 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
#276 Tom, I understand that when someone is saying "I'm gonna kill you", he or she probably doesn't mean it the literal way. But I wasn't going to read LAGI or whatever. BBD simply quoted them and nobody has said that BBD misquoted them. "...1000 watts that strikes the surface in each SM of land" is factually and utterly false; I'm tempted to add shamefully. That doesn't make the conclusions in LAGI wrong -in fact what everybody have quoted here looks 'rightish' at a conclussion level-. Also, that doesn't make BBD arithmetic a sound one either. The fact here is we are not talking of Aristotle. LAGI is not a dead scholar from times gone and the text is not written in a parchment so it's easy to use a text editor and change the content of the site. There's no excuse. In fact those verbal blunders allow the BBDs in the world to continue their harangues. That should concern you, not showing instead how deeply wrong is BBD's, or making of me a substitute target. Making infantile math like 20% of 1000 during 2000 only attracts the infants and allows the mathematically infantile to flit about. -
BBD at 01:16 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KR Okay. LAGI has tied us all in knots. Let's try again. Here's my take for dissection: LAGI is based on an unrealistic estimate of output from solar plant. It generates an exaggerated value for this as follows: It takes the peaking mid-day figure of 1000W/m2 and applies a 20% efficiency: 1000 x 20% = 200W/m2 This figure will be correct for the middle of the day. It is the highest possible output the plant can achieve. Peak. LAGI then uses this peak value for every sunshine hour in its caclulation. It assumes 8 hours per day and 250 sunshine days a year. Perfectly reasonable. 8 x 250 = 2000 hours BUT - 2000 hours of 200W/m2 output: 2000 x 200 = 400,000 or 400kWh Which is a substantial exaggeration based on: - the incorrect assumption of constant 200W/m2 plant output - non-standard method This then forms the basis of its estimate of 500,000 km2 = 23W. The correct method is:average raw energy density x plant conversion efficiency = average output
200W/m2 x 20% = 40W/m2 It looks like I am applying a 20% conversion efficiency on top of LAGI's 20% conversion efficiency. But I am not. I'm using the standard method. This is why we are all confused. I am more convinced than ever that LAGI is a deliberate attempt to mislead. -
Alec Cowan at 00:49 AM on 13 July 2011The Medieval Warm(ish) Period In Pictures
#35 Rob, I've got the gridded data from climate normals 1961-1990 as an anomaly on a 1941-1970 base. This is the graphic -using a 250km radius-:
Now I have the problems of having two different grids and that those gridded data in Figure 1 are supposed to be plotted using a Matlab file. But I think that I'll finally manage to get a 5° grid for the image and to write a script to take gridded info from Figure 1 in order to develop a graphic that will approximately show what I am speaking form the very beginning. By eyeballing both images I could notice what I expected -what is dangerous itself: to expect- in comparison with Figure 1: even a bit warmer Iceland and Greenland, not so turbulent Mongols and Tartars, and about the "Figure 1" for LIA -Figure 2 in Mann et al- a confirmation of the reason for my city of birth to be established twice.
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Dikran Marsupial at 00:45 AM on 13 July 2011What we know and what we don't know
Eric the Red an exponential with a low rate constant can look "fairly linear", but it is still exponential. If you can show me an anlysis that robustly demonstrates that it is linear (rather than there just isn;'t enough data over shuch a short time span to distinguish between linear and exponential with statistical significance) then I am happy to stand corrected. The rise in CO2 is unaffected by our expectations, it is affected by our actions. As Niels Bhor said "Prediction is very difficult, especially about the future" - in the 70s they though we would all be flying around in our hovercars and would have a domestic robot doing our chores by now, but it hasnt happened. IMHO it is extremely rash to decide the action we should take now on the basis of what technological solutions the future may offer. There is an appreciable probability that such solutions will not be made available, or if they are they will be available too late. The advantage of predictions based on a continuation of what has gone before is that we know it is plausible a-priori. -
Eric the Red at 00:43 AM on 13 July 2011Trenberth on Tracking Earth’s energy: A key to climate variability and change
Ken, Nice post between the two theories. There may be other explanations for where the heat went, or why the heat has not reached the surface, which may be revealed when the data materializes. However, it does come down to two basic interpretations: either the heat is there, and we are just not measuing it (Trenberth), or the heat is not (Hansen). -
KR at 00:36 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
In my previous comment I am referring to pre-conversion energy available at tropical sites. Equations 1 and 2 yield the same numbers (with LAGI's figures being rather conservative), and hence LAGI is properly doing their math. -
Eric the Red at 00:35 AM on 13 July 2011What we know and what we don't know
Dikran, The CO2 rise was only exponential when you start from preindustrial levels. The rise has been fairly linear since 1975. Change is the only constant in our civilization, and no one could foresee the changes today 90 years ago, and we cannot foresee the changes 90 years from now. I do not think many people expect a contiued rise to 550 ppm by 2100. I do not think the point of this article to claim that we do not know anything at all, but rather what is certain, and what is uncertain. Nor do I think this article advocated not taking any action. -
KR at 00:34 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD - To be as clear as possible: Power over the course of the year can be calculated in two different ways. (1) Daily average power/m^2 * number of hours per year, or 200 * 24 * 365. (2) Peak power/m^2 * effective number of hours peak power is available, or 1000 * 2000. You keep calculating it as: Daily average power/m^2 * effective number of hours peak power is available This is a fundamental math flaw, mixing the two equations. -
KR at 00:26 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
BBD - And... you repeat the error, by stating "200W/m2 x 2000 = 400kWh per m2" It's not 200W * 2000 hours, but 200W * 24 hours * 365 days. Or, 1000W * 2000 hours/year of available time for collection. 200W is daily per/hour average, while 1000W on the other hand is peak power that is then scaled by the hours that power is available (2000/year, or 5.5 hours a day, more, actually, tapered for morning/evening). Apples and oranges, BBD - you are taking a 24 hour daily average and then scaling again by a fraction of a day. This is an error. I simply don't know how to put that any more clearly, BBD. 200W daily average is already scaled by hourly availability - yet you scale it again! LAGI then (properly) applies a 20% conversion efficiency. 30% is possible for CSP, minus additional plant footprint - not unreasonable. -
BBD at 00:06 AM on 13 July 2011A Detailed Look at Renewable Baseload Energy
KR Yes! You've got it:LAGI figures of 1 KW/m^2 * 2000 hours = 2000 kWh/m^2/year before conversion efficiency applied. MacKay figures of Honolulu, HI, 248 W/h/m^2 daily average * 24 hours * 365 = 2172 kWh/m^2/year before conversion efficiency applied. No disagreement once scaling factors are accounted for.
LAGI has used a reasonable estimate for average raw energy density of 200W/m2. It's properly conservative compared to those we have for SA (220W/m2) and Honolulu (248W/m2). It then takes this estimate, and treats it as 'capacity' - without a plant conversion efficiency factor - and uses it to get its footprint estimate. In LAGI:average raw energy density = plant output
LAGI does this:average raw energy density = average output
200W/m2 x 2000 = 400kWh per m2 Instead of this:average raw energy density x plant conversion efficiency = average output
200 x 15%* = 30W/m2 30W/m2 x 2000 = 60kWh per m2 That's why it is wrong. *This is an example only. Put in your preferred CEF, but remember, anything above 20% is getting fanciful. -
Dikran Marsupial at 00:05 AM on 13 July 2011What we know and what we don't know
Eric the Red We do know something very important about what lies in the future for CO2 emissions, which is that it is almost entirely in or own hands; if we want atmospheric CO2 to fall, we can make it happen; if we want it to stabilise we can make that happen too; if we are stupid enough to continue the exponential rise all we have to do is carry on with "business as usual". As regards climate sensitivity etc., the fact that we don't know anything for certain doesn't mean we don't know anything; not all theories that have yet to be refuted have equal support from the observations. Some theories are more plausible than others, and there is a well understood mechanism for determining the best course of action under uncertainty - namely statistical decision theory. So lack of certainty is not a good reason for not taking any action and waiting to see what will happen. -
Rob Honeycutt at 00:03 AM on 13 July 2011Trenberth on Tracking Earth’s energy: A key to climate variability and change
Ken... "we could not expect Asian aerosols to disappear anytime soon." You might be surprised on that one. The rate of change on almost every level in society in China is very rapid. The clean air act in the US had a pretty rapid affect on air pollution here. There is no reason to believe that China's responses to air pollution will be any slower. -
Eric the Red at 23:49 PM on 12 July 2011What we know and what we don't know
Very good analysis of what we do know, and the contentions that a majority of scientists believe that humans have contributed. The unknowns need to be assessed for what they are. We do not know what lies in the future for CO2 emission, nor do we know how much warming will be caused. Other contributors and feedbakcs are still being assessed. Lastly, we can only speculate on future effects based on observed effects. -
KR at 23:45 PM on 12 July 2011A Detailed Look at Renewable Baseload Energy
BBD - Comparisons, converting both 'apples' and 'oranges' into juice: LAGI figures of 1 KW/m^2 * 2000 hours = 2000 kWh/m^2/year before conversion efficiency applied. MacKay figures of Honolulu, HI, 248 W/h/m^2 daily average * 24 hours * 365 = 2172 kWh/m^2/year before conversion efficiency applied. No disagreement once scaling factors are accounted for. -
KR at 23:36 PM on 12 July 2011A Detailed Look at Renewable Baseload Energy
BBD - Reposting sometimes occurs when a page is refreshed; that's happened to me a number of times. -
BBD at 23:35 PM on 12 July 2011A Detailed Look at Renewable Baseload Energy
Moderator Dikram Marsupial I do not understand why the deleted comment has re-appeared. If I have somehow re-sent it I did so in errorModerator Response: [Dikran Marsupial] No problem, I have deleted it. I suspect KR is right, I've done the same thing myself more than once! -
KR at 23:35 PM on 12 July 2011A Detailed Look at Renewable Baseload Energy
BBD - MacKay does not indicate in that chart whether that is raw power or power over the course of the day. Looking at raw insolation for Africa, for example, extracting 400 kWh/m^2 over the course of the year represents about 20% of available power.
MacKay's chart looks like daily average insolation (including night), whereas the LAGI figures are raw insolation times hours that is available - Apples and oranges, BBD.
You state:
"LAGI says:
We can figure a capacity of .2KW per SM of land (an efficiency of 20% of the 1000 watts that strikes the surface in each SM of land). What it means is that average raw energy density at the surface is 200W/m2.
The choice of words is fabulously confusing. One might even suspect deliberately so."
What LAGI actually states in that figure is: "Areas are calculated based on an assumption of 20% operating efficiency of collection devices and a 2000 hour per year natural solar input of 1000 watts per square meter striking the surface."
I found that quite clear - you have (mis)stated the figure, which shows your confusion on the LAGI statement. Raw insolation is on the order of 1000 W/m^2, not 200 W/m^2, and taking (as you have repeatedly) an output value of 200 W/m^2 and then applying conversion efficiency again is an error.
---
And now for some math from your South Africa example:
5.25 kWh/m^2 per day * 365 days is 1916 kWh/year available; extracting 20% of that would be 383 kWh/m^2 - both numbers right about what LAGI estimates. An average of 220 W/m^2 over the course of the day looks about right for an insolation peak of 1000 W/m^2.
You keep confusing averages over the course of the day with peak insolation * hours available, BBD, and then claiming calculations based on the latter are incorrect. I don't believe it's worth discussing this matter further with you until we can agree on a common vocabulary.
-
Ken Lambert at 23:34 PM on 12 July 2011Trenberth on Tracking Earth’s energy: A key to climate variability and change
Michael Sweet #11 This is remarkable statement: "Here we see real skepticism at work in science. Hansen has proposed that aerosols reflect more heat into space. Trenberth proposes that the missing heat has been absorbed into the deep ocean. Hansen is skeptical of Trenberth's results and Trenberth is skeptical of Hansen. Both of them will marshall their data to determine which is more correct (it may be a combination of both effects). In the end the data will determine who is correct. This is an example of real climate scientists debating the data." Probably the two most prominent climate scientists on the planet disagree about whether or not the warming imbalance is 0.9W/sq.m or 0.59W/sq.m over the last 5-6 years when the imbalance must in theory be increasing due to increased CO2GHG in the atmosphere. Dr Trenberth says the missing heat 'is there but we just can't yet measure it in the oceans' and Dr Hansen says the heat 'is not there because extra aerosols have reflected it out to space'. This seems to be a fundamental difference in how the trajectory of warming might evolve - as we could not expect Asian aerosols to disappear anytime soon. Dr Trenberth wrote: "While the planetary imbalance at TOA is too small to measure directly from satellite, instruments are far more stable than they are absolutely accurate. Tracking relative changes in Earth’s energy by measuring solar radiation in and infrared radiation out to space, and thus changes in the net radiation, seems to be at hand." The CERES satellite data quoted in the Aug09 paper for 2000-05 were adjusted to an estimated imbalance of 0.9W/sq.m from an absolute value of about +6.4W/sq.m. The latest data shown in Fig 3 above shows an Rt value varying around the 1.0W/sq.m. How is this data 'adjusted' from the absolute value? I would also like to ask Dr Trenberth whether the ENSO-La Nina cycles are 'internal' redistributions of global heat already within the system or are external global forcings which should be added to the RF and climate response terms to determine an imbalance. The final issue I query is how Dr Trenberth's 'missing heat' gets into the deep oceans in a relatively short few years. viz. "The overturning may involve the ocean down to several kilometers and can take many centuries to complete a cycle".
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