The above diagram, which comes from The Electricity Operator in Ireland (SEMO), shows the increases in the different types of reserve or back up required by 2020 to keep the system stable with high penetrations of wind.
Some of these reserve increases will come from fast acting plant like open gas cycle turbines (OCGT) and interconnectors (both existing and new entrants according to the paper). OCGT are less efficient and higher emitting than their modern versions (CCGT). Likewise, SIR referred to above, refers to Synchronous Inertial Response which relates to the level of stability a generator can provide when operating at low outputs during periods of high wind. CCGT operating at these low loads are also less efficient and higher emitting.
Nobody, it seems, has bothered to do a study to see if this will offset any gains from higher wind penetrations.
So who or what is driving these changes to our electricity system ?
These changes are being driven in large part by European legal obligations outside the control of the SEM Committee.
Making an obligation legal does not make it achievable if it is impossible to achieve. Over the last 5 years or so wind penetration of the domestic market has flattened off at around 15%. Even though significant increases in capacity have been commissioned. At the current rate of increased penetration, of wind in the domestic market,it will take 100+ years to achieve 37% of wind penetration of the domestic market. Increasing wind access to the grid from 50% to 75% of output at a given time might reduce the number of years to get to the 37% to 90. Which is a moot point any way as these larger greater than 2 megawatt wind turbines are pieces of engineering junk. As outlined in a recent publication" How turbulent winds abuse wind turbines drivetrains" these larger wind turbines might last 8 years. This is an act of desperation grid security is being thrown under a bus in attempt to achieve the obviously unachievable target of 37%. Installing extra back up capacity, at massive expense, for what are going to be negligible increases in usable wind output. As wind production is unpredictable hence produces massive amounts of unusable electricity.
ReplyDeleteGreed and Pride a deadly combination.In this case accompanied by incompetence.
The whole wind program should have reviewed in 2012 when the UNECE released it judgment. If it not closed down and these crazy plans implemented expect the economy to collapse returning every one to a peasant life style.
On Sean's comment.
DeleteAn observation of various turbines show that the larger the diameter of the turbine blade the slower they turn The centrifugal / centripetal forces oppose each other and must be balanced so that the blade has enough tensile strength to stop it yielding to the pressure in high winds and flying off. Here are some observations.
65 meter diameter = 21 rpm x 65 x 3,14 = tip speed of 4286 meters per minute
126 meters diameter = 12 rpm x 126 x 3.14 = tip speed of 4747 meters per minute
If we take a figure of 4500 as an approximate average maximum tip speed, the formula for blade speed is 4500/(pye x blade diameter) = speed of rotation in RPM (revs per minute).
So to find the rotation speed of a turbine with a diameter of (say) 137 meters it's 4500/(3,14 x 137) = 10rpm. For 63 meters diameter its 4500 /(3.14 x 63) = 22.84rpm. This is roughly correct with my observations. Remember wind speed does not materially effect the result.
Take it that the average alternator to fit in a nacelle of a modern wind turbine will need to turn @ 1700 RPM, what is the formula for the rpm ratio between the turbine blades and the alternator? 1700 divided by 4500/(3.14 x blade diameter) = ratio that the gear train must step up rotation speed between blade and alternator.
Example: An Enercon E126 turbine has a blade of 126 meters and a rated capacity of 7.5mw so.
4500 /(3.14 x 126) = 11.37 rpm. = 1700/11.7 = 145 : 1
The Queen of Oak Bay -roll on roll off - Canadian Ferry has total engine capacity of 8.8 mw at full throttle. She can carry 1,400 passengers and 362 cars. We can see that in strong winds the E126 would be reaching 85% of the ferry capacity. I use the ferry because it is a common experience for readers. There is a lot of power there. Therefore, when the torque on the alternator shaft would be 85% of that leaving the engines of the ferry at full throttle, the torque on the turbine main input shaft would be 7.5mw x 145 = 1,087 mw. 104 times the torque on the ferry.. It would take a substantial steel shaft to carry that load, probably 500 mm diameter. Such a load would put enormous strain on gearbox housing, cog wheels and bearings. Step up gear trains absorb massive amounts of the energy they transmit and the heavier the cog wheels the more they absorb.
Bearings: One type is shell bearings as used in internal combustion engines, but these need warm oil to be pumped in under enough pressure to keep the bottom of the shaft journal separated from surface of the shell bearing. This would absorb massive amounts of the turbines energy.
The alternative is to use roller bearings, with low pressure oil. The problem here is that only a segment of the rollers are in contact with the races, they have to bear all the weight among just a few. Recent reports suggest that at times of gusts, the alternator speed exceeds (grid connected) the input torque causing it to drive the turbine.
All gear trains have a devil called back lack lash. If you jack up the front wheel of your car, put it in gear and turn the wheel in both directions, you will find some travel before engagement, That is back lash. It plays havoc with step up gear trains and causes roller bearings big problems as they wiggle around.
DeleteSummary: What you are seeing here is the constraints on size. If trees get too big, the trunk can't support the weight, if a elephant were to grow twice the normal weight, its legs would not hold it up. As turbines increase in size, the difficulty in bringing all this transmission weight up to 1,700 rpm gets worse, things run for a while when new, but if they use light weight metals they yield and if they use heavy steels they absorb too much energy. After a few years, the whole lot galls and has to be replaced. Any engineer worth his salt would tell them that, but of course engineers are the last people the industry or their government supporters want involved.
I read one report where they appear to have used titanium, a light weight substitute for steel. While it is strong, it can't retain a polished surface like steel and is too soft to resist binding when used as bearings races or cog wheels. Proof of this is that titanium is used in expensive firearms, but the barrel bore is always lined with alloy steel. So if you invest in wind, sell on as soon as you can. Heard of one that broke in Wexford that cost 600,000 Euros to repair.
Before leaving Sean's point above; Checking the Cavan wind farms data, I found that they never appear to come close to generating at maximum name plate output during hight winds. Our present 2,300 mw of wind never appears to deliver 2,300 mw of output per Eirgrid's web site.
ReplyDeleteOne way to dodge the gear box problem might be to keep turbine output low to avoid the extremely high torque. Perhaps they are receiving constrained payment in which case consumers are funding the avoidance of design faults. The output can be curtailed by restricting the direct current to the wound rotor and also by turning the blades away from the wind (like the sail of a yacht). But this begs the question, why do they need to make turbines larger and larger, in a kind of race for size? This also increases resistance among local communities. Professor David McKay, advisor to the British government, said that it is the area of ground covered (not the size of the turbines) which effects production per plot of ground. If turbines are large enough to be above local wind sheer height, they should be adequate. More small ones can be fitted on a plot of land than if they were larger ones. (same as a kilo of small tomatoes contains more than a kilo of large ones.) Knowing the industry as I do, I could hazard this guess. Notwithstanding all the subsidies, all the hype and huge government inducements, planning procedural fixing, the obstacles to making money with wind farms over the long term are so great that they are not making money. Wind farms are not like Hotels, football stadiums, toll roads supermarkets or farms which have considerable residual value if sold after owners want to leave the industry or retire. Wind farms are more like factories. Their values is confined to the product they produce day in day out. There are no barriers to entry because the land use is agricultural value only and can still be used for agriculture. Experience is teaching financiers, that there is a problem with wind farms as a going concern. There is a problem with sustaining profitability because of lower achieved capacity factors than is being forecast. The turbine producers must make some excuse for this failure and provide some solution (some new innovation) to overcome it. There is only one innovation possible, ---MAKE 'EM BIGGER--- . The capital depreciation tax allowance for wind turbines is much higher, (faster write down of depreciation) than normal but after this short period elapses, taxation accrues. We can see that both natural and man made design places a limit on size, a balance. We see it in cars size, shipping, aircraft, tractors, cows, people, An exception may be buildings, but buildings do not have external moving parts and have many uses. Wind farming is an unsustainable industry, totally dependent on subsidies. Those investing lack the intelligence to see the problems, but possess the bravery of buccaneers. Just like Flash Harry a post war movie or indeed the Celtic Tiger bankers and builders, they go for the biggest, brightest, shiniest, and more ostentatious latest thing.
When consumers are forced to pay and and clean up the mess, sure why not?
If you have time search with Google, http://www.telegraph.co.uk/news/worldnews/europe/denmark/7996606/An-ill-wind-blows-for-Denmarks-green-energy-revolution.html
ReplyDeleteIf the link fails to work, google "an ill wind blows for Denmark's green energy revolution - telegraph" . It appear to me that we are dealing with slow learners and our campaigns to alert the public are slowly but surely working.
Just checked my domestic electricity bill from ESB Electric Ireland, Bill for November/December 2014 and May June 2015, 6 month interval. Taking the price by the total bill divided by kwh used to give price per kwh (unit). I find an increase of 5.08% for the half year. The latest one charged 24.75 euro cent. So 4 units is now one euro.
ReplyDelete