tag:blogger.com,1999:blog-6156940350159100953.comments2024-01-14T22:07:22.183-08:00Sustainable Energy - without the hot airDavid MacKay FRShttp://www.blogger.com/profile/08023079754784119955noreply@blogger.comBlogger796125tag:blogger.com,1999:blog-6156940350159100953.post-10678762727995260342016-03-14T13:40:57.596-07:002016-03-14T13:40:57.596-07:00We should not forget that it is not just about ene...We should not forget that it is not just about energy - carbon is pretty important too (just having had the single highest monthly temperature rise over the accepted average - Feb 2016). Electricity from the grid can (and is being) steadily decarbonised. There is no realistic way to decarbonise diesel on a large scale. So, adoption of the e-Golf over the TDi will help to force that transition, and so the carbon benefit (of e-Golf over TDi) will increase over time.<br /><br />Also, the exhaust pipe emissions are important to all those pedestrians, cyclists, other drivers, and those who live near busy roads. The e-Golf wins there too.<br /><br />So let's go 'glass half full', assume the batteries will be available (actually cheaper, lighter, less embodied energy, and most importantly compatible), and go for the e-Golf.<br />Danny Bonnetthttps://www.blogger.com/profile/11297127711806731525noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-72856569611027205832016-02-03T01:41:49.115-08:002016-02-03T01:41:49.115-08:00Well, I believe that gas is one of the important p...Well, I believe that gas is one of the important part of cooking. Most of us uses gas to cook.<br /><a href="http://www.jericos.co.uk/" rel="nofollow"><b>GAS</b></a>Anonymoushttps://www.blogger.com/profile/03219878280610104755noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-71459213238066003462016-01-17T20:30:59.514-08:002016-01-17T20:30:59.514-08:00I have very bad circulation. My hands and feet are...I have very bad circulation. My hands and feet are always much colder than the rest of my body and it's worse in the winter. I hate having to get up in the morning since my warm and toasty toes always become really cold when they touch the floor. I think underfloor insulation might just be the way to go. You're right about comfort. I would not mind paying just a bit more for warmer toes.<br /><br /><a href="https://britechhvac.wordpress.com/2015/09/08/have-heating-and-cooling-experts-deal-with-your-summer-ac-problems/" rel="nofollow">Henrietta Fuller @ Bri-Tech Heating and Cooling</a>Anonymoushttps://www.blogger.com/profile/00813915450860649745noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-86978764843688192272015-10-24T01:49:38.482-07:002015-10-24T01:49:38.482-07:00@Nick,..
In the case of downwind faster than the...@Nick,..<br /> In the case of downwind faster than the wind, it is the wheels which are driving the propeller,.. given the equation Power = Force x Speed,.. the higher speed of the wheels relative to the ground experiencing a lower drag, can translate to a greater thrust force at the propeller at a lower relative airspeed, giving a net forward thrust without violating the conservation of energy.<br /> The confusion arises from thinking the wind alone is the usable power source when in fact it is the relative motion of the two media(air and ground) in which the vehicle is traveling.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-41139884082592400222015-10-21T01:31:10.908-07:002015-10-21T01:31:10.908-07:00Using 300 W/kg ( https://en.wikipedia.org/wiki/Sol...Using 300 W/kg ( https://en.wikipedia.org/wiki/Solar_panels_on_spacecraft ) and a space elevator($220/kg) I get a cost of $733/KW for space solar.<br /><br />A falcon nine heavy is $5,333/Kw. (for LEO)<br />Assuming $3,000 for the 1KW solar,transmitter,receiver,grid etc itself.<br />80% efficiency for beaming.<br /><br />$8,333/KW for space solar. ($10,416.25 / KW delivered)<br /><br /><br /> $6,499 for a 24kWh Nissan leaf battery.<br />$12,000 for a 6kw solar system. (quick google search)<br /><br />$19,000 for a 1KW for 24 hours system. (And you can store up to 24Kw of unused power.)<br />$10,416 for a 1KW LEO space solar. (any power not used is wasted, and we have time in the shadow of the earth and time when we are not in sight of the receiver. )<br />$20,416 for a 1KW GSO space solar. (and any power not used is wasted)<br /><br /><br /><br /><br />Catproghttps://www.blogger.com/profile/14967819844261829312noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-25369418550612950002015-10-15T00:16:31.849-07:002015-10-15T00:16:31.849-07:00thanks!!!thanks!!!Anonymoushttps://www.blogger.com/profile/12260942381656189001noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-83969580564871847592015-10-08T06:43:29.922-07:002015-10-08T06:43:29.922-07:00Hi David
Just come across your blog, thanks for p...Hi David<br /><br />Just come across your blog, thanks for putting all this work out there. I came across your book a few months ago whilst looking at various figures for PV solar panels and found it very useful.<br /><br />My thoughts on this post mirror a few of those above. Might it not be useful too, to show the CO2 output of each? Surely that's a vitally important factor. Also, how about the Net Energy Gain - I don't know huge amount about the process of fracking, but that number of trucks alone is going to require a huge amount of energy, aside from the CO2 output. Also an economic analysis of some sort I would suggest is important too. <br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-45238295364392580622015-09-30T03:59:53.262-07:002015-09-30T03:59:53.262-07:00Dear Professor MacKay, have you already written a ...Dear Professor MacKay, have you already written a comment on the new report by Greenpeace called "Energy [R]evolution"? http://www.greenpeace.org/international/Global/international/publications/climate/2015/Energy-Revolution-2015-Full.pdf<br /><br />I'm sorry if I'm asking something already answered elsewhere.Maurihttps://www.blogger.com/profile/08863079903315871522noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-54450497809798698922015-09-16T19:11:07.417-07:002015-09-16T19:11:07.417-07:00Here's my calculation for lifecycle energy of ...Here's my calculation for lifecycle energy of an electric Golf (e-Golf ) vs diesel.<br /><br />Lifecycle energy = Embodied energy (in production) + operational energy consumed by using the car <br /><br />We’ll use 200,000 lifetime miles as reasonable expected life, although diesels have proven to run for longer. At average annual driving distance 12,000 miles (19,000 km), this equates to 16 years life, which should be expected for a Golf.<br /><br />During this 200,000 miles, we can assume that the batteries in the e-Golf will need to be replaced at least once. <br /><br />Production embodied energy<br /><br />Using LCA software, Volkswagen has calculated around 24,000 kWh (85 GJ) for production of a standard Golf and 40,000 kWh (145 GJ) for production of an e-Golf.<br /><br />http://en.volkswagen.com/content/medialib/vwd4/de/Volkswagen/Nachhaltigkeit/service/download/umweltpraedikate/e-golf-hintergrundbericht-2014-englisch/_jcr_content/renditions/rendition.file/e_golf_umwpraed_hb_eng_1006.pdf<br />pages 19-20<br /><br />The difference in embodied energy between the e-Golf and TDI is the batteries = 40,000 – 24,000 kWh = 16,000 kWh<br /><br />So embodied energy for e-Golf (assuming 200,000 miles life with one battery replacement) is actually = 40,000 kWh + 16,000 kWh = 56,000 kWh<br /><br />Energy consumed by using the car. <br /><br />The 2015 e-Golf has an official EPA rated combined fuel economy of 116 miles per gallon gasoline equivalent (MPGe) for an energy consumption of 29 kW-hrs/100 mi. <br /><br />2015 Golf TDI (2.0) has an official EPA rated combined fuel economy of 36 miles per gallon equating to 93 kW-hrs/100 mi. <br /><br />Operational energy, using 200,000 lifetime miles as expected life:<br /><br />e-Golf = 200,000 (29/100) = 98,000 kWh<br />Golf TDI = 200,000 (93/100) = 186,000 kWh<br /><br />Total lifecycle energy = Embodied energy (in production) + operational energy consumed by using the car <br /><br />e-Golf = 56,000 kWh production + 98,000 kWh = 154,000 kWh<br />Golf TDI = 24,000 kWh production + 186,000 kWh = 210,000 kWh<br /><br />The e-Golf wins with a 73% lifecycle energy consumption. However…. The above calculation assumes that you can actually get replacement batteries for the e-Golf after 10 years (minimum mandatory stocking period for any car manufacturer). If not, then your e-Golf is about as useless as a rechargeable drill without a charger and battery, which have a built-in obsolescence of about 3 years it seems. Given the rate at which battery technology is changing, I’m not sure it’s safe to assume that the same battery form will exist 10 to 16 years hence.<br /><br />I’m sticking with the TDI…Anonymoushttps://www.blogger.com/profile/06398140872266003687noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-74256061189804942432015-09-15T22:43:08.375-07:002015-09-15T22:43:08.375-07:00Congratulations. I still regularly refer people to...Congratulations. I still regularly refer people to SEWTHA, unfortunately I no longer lend my paper version, because the last person never gave it back!<br /><br />I'd love to see some kind of 'template' so that people could hack together equivalent numbers for their country. I believe something like that was started but stalled?Benjolhttps://www.blogger.com/profile/14076527068502260545noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-78801424300388031532015-09-11T15:52:21.516-07:002015-09-11T15:52:21.516-07:00As far as I can make out, a 3MW wind turbine occup...As far as I can make out, a 3MW wind turbine occupies - at most - about 400 square metres. The rest of the area occupied by the wind farm can be used for agriculture as it was before the wind farm was installed. If you assume the actual output of a turbine is about a third of its rated output we have 1MW generated from about 400 square metres. 2500 watts per square metre.<br /><br />This figure compares well with the land area occupied by a conventional coal station, eg Drax, where about 3.25 square kilometres produce 4GW - about half that of the wind turbines! If you include the area of the coal mines needed to feed this station the figure drops even lower.<br /><br />It is clearly unfair to assume, as seems to have been done, that the land between the turbines is unusable for anything else. In the majority of cases the arrival of the wind farm has only a tiny impact on the agricultural use which can carry on as before.Anonymoushttps://www.blogger.com/profile/12006525248375546616noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-39686866554412930472015-09-10T01:33:55.897-07:002015-09-10T01:33:55.897-07:00How much could this ratio be changed, if the incli...How much could this ratio be changed, if the inclination of solar installations was optimized for greatest wintertime production, rather than greatest overall production?<br /><br />Also, would this make hotter climates a more sustainable place to live? Solar panels produce more energy closer to the equator, the difference between summer and winter production is smaller, and due to the warmer climate the energy demand is actually greater during the summer. Such places tend to be rather dry, which represented a barrier to populating them before because people need water more than they need warmth, but with sufficiently cheap energy desalination of sea water could become a feasible source of drinking water.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-9893109820112220592015-09-04T11:24:18.521-07:002015-09-04T11:24:18.521-07:00- John Russell, I think my numbers agree with what...- John Russell, I think my numbers agree with what you said, bearing in mind that "a sunny December day" is not the same as an average December day. In the UK the ratio between an <em>average</em> June day and <em>average</em> December day is ~ 22.5 kWh/d : ~ 2.5 kWh/d <a href="http://www.inference.eng.cam.ac.uk/mackay/presentations/Simonyi2014/mgp00043.html" rel="nofollow">DATA HERE</a> i.e. about 9:1. There tend to be much more dull days in December than June. This nine-to-1 ratio is the main problem with the wishful thinking about solar power making a "huge" contribution in northerly locations. I'll write more in due course as promised. David MacKay FRShttps://www.blogger.com/profile/08023079754784119955noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-33715026824642326062015-09-04T10:27:06.291-07:002015-09-04T10:27:06.291-07:00Anyone who lives in the temperate zones and has so...Anyone who lives in the temperate zones and has solar panels on their roof should know that peak summer month generation will total approximately five times that of the lowest winter month. In the UK I can generate ~25kWh on the sunniest June day and ~5kWh on a sunny December day (when I need power most!). <br /><br />Obviously this multiple will become larger the nearer the poles you are.John Russell (@JohnRussell40)https://twitter.com/JohnRussell40noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-68647678997590919922015-08-17T02:49:00.378-07:002015-08-17T02:49:00.378-07:00I know this is an old post, but I stumbled upon yo...I know this is an old post, but I stumbled upon your blog when looking up information in the online version of your book. Is there any chance you could put up your draft chapters? Obviously if you think marking it as a draft isn't sufficient then mark in some way if calculations haven't been thoroughly checked or if you need more references ([citation needed]?). Since you've already embraced the creative commons approach to publishing (part of the reason I bought a physical copy of the book) is it such a stretch to share your unpolished work too?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-62512071424520693002015-08-04T03:56:21.774-07:002015-08-04T03:56:21.774-07:00Pawb1 is right.
With the abandonment of many Roun...Pawb1 is right.<br /><br />With the abandonment of many Round 3 projects in more exposed/distant waters, especially off the West Coast ( e.g. Celtic Array and Atlantic Array) it seems that offshore development is increasingly being concentrated on easier, closer, more economic East Coast sites and extensions to existing schemes with lower capacity factors due to wind resource.<br /><br />This is probably more than balanced for operators by less wear and tear and downtime due to access difficulties.BillGhttps://www.blogger.com/profile/05962119919631086707noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-17474794154998828642015-08-03T14:17:18.987-07:002015-08-03T14:17:18.987-07:00David - any news on how well your underfloor insul...David - any news on how well your underfloor insulation has performed through the Spring?Andrew Harmsworthhttps://www.blogger.com/profile/10584253651150632078noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-37205374119813902592015-08-03T12:23:12.055-07:002015-08-03T12:23:12.055-07:00There could be, at least 2 factors at work here. T...There could be, at least 2 factors at work here. The reduction in aerodynamic performance by the lack of regular cleaning of the blades is one reason and the fact that the earlier offshore farms were not offshore at all, they're close inshore and relatively inexpensive to build, whereas the later farms are further offshore and in cleaner wind.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-88207490322174084982015-08-03T11:34:15.235-07:002015-08-03T11:34:15.235-07:00Another hypothesis would be that size matters. It...Another hypothesis would be that size matters. It looks to me like the bigger producers also have higher load factors (outside of the anomolous one in 2014). Of course, the bigger ones also tend to be the most recent, so all very difficult to interpret. You would need data from a previous point in time to disentangle the effects, but your aging hypothesis looks like the cleanest explanation to me.<br /><br />JamesJamesnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-36019843023774554412015-08-03T11:33:17.620-07:002015-08-03T11:33:17.620-07:00The performance of wind farms is very dependent on...The performance of wind farms is very dependent on their location. This applies to both onshore and offshore wind farms. For example the rolling average load factor for onshore wind farms in England is 25%, in Wales it's 25%, in Scotland it's 28% and in NI it's 31%. Within England there are big regional differences (22% to 26%). Has the location (and hence wind resource) been factored into the offshore data analysis?pawb1https://www.blogger.com/profile/12409197045896335933noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-18403331420212296742015-08-03T09:20:15.562-07:002015-08-03T09:20:15.562-07:00@Anonymous: The Staffell-Green paper didn't re...@Anonymous: The Staffell-Green paper didn't resolve whether the ageing is caused by changes in the turbines or because of maintenance downtime. This is the sort of information that wind farm owners will have at their fingertips, I am sure, but (even though the public have actually paid everything) such data are never published, sadly!<br /><br />@BishopHill - yes, what you said is conceivably true; and it is possible that some but not all of the new wind farms are indeed much better, and that we would be able to see an improvement signal if we could disaggregate the data by wind-turbine technology. Sorry, I just did a quick and dirty one-hour job on this, to see if there was any stand-out signal in the data. David MacKay FRShttps://www.blogger.com/profile/08023079754784119955noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-16647344037457750392015-08-03T09:03:31.818-07:002015-08-03T09:03:31.818-07:00Presumably one could equally conclude that the tur...Presumably one could equally conclude that the turbines are ageing faster than Staffell and Green suspected but that there has been some technological advance. I would have thought this was a more plausible explanation than no tech advance at all.Bishop Hillhttps://www.blogger.com/profile/10959746529461713876noreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-51262565467461695612015-08-03T08:39:55.823-07:002015-08-03T08:39:55.823-07:00Is the aging a reduction in individual turbines...Is the aging a reduction in individual turbines' output or simply an increase in the annual amount of maintenance downtime required averaged across a farm?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-55537480398404322782015-07-30T23:09:27.542-07:002015-07-30T23:09:27.542-07:00Just came across your blog and very interested to ...Just came across your blog and very interested to see your calcs and thinking on insulating the underside of suspended floors. I lived in a house with this floor structure many years ago and the thermal comfort was truly awful, aggravated by very poor airtightness round the edge of course as joists had settled/moved in a few places to make it even worse.<br /><br />I viewed a suspended 60’s bungalow a couple of years ago when house hunting for my in-laws and there were fan heaters everywhere as a result!<br /><br />A little while ago I came across this startup company http://www.q-bot.co/services.php which is doing very well in developing a small tethered robot to insulate underfloor structures with spray foam. DECC are running some trials which I believe are going extremely well.<br /><br />I agree with you that the comfort driver carries great weight in such an investment decision.<br /><br />I was also looking at U values of carpet underlay a little while ago, and there are some surprisingly high TOG value/Low U-Value underlays (TOG 3.4 – U value circa 3) out there. We have some of this down in our bedroom and it is surprising how thermal comfort feels really good in bare feet (albeit this over an internal upstairs floor void rather than ground floor)<br /><br />Mark Thompson - Lead Technologist, Innovate UK<br />Mark Thompson - Innovate UKhttps://www.linkedin.com/profile/view?id=12076500&trk=hp-identity-photonoreply@blogger.comtag:blogger.com,1999:blog-6156940350159100953.post-25123763258823832212015-07-16T00:02:45.981-07:002015-07-16T00:02:45.981-07:00I think this is one of the most important think in...I think this is one of the most important think in humans history to take part in that we must to use space solar powerhangar doorhttp://barduva.eu/en/products/fabric-hangar-doors/noreply@blogger.com