## Study of Wind Power in UK Finds Actual Results Extremely Variable

##### 11 December 2006

An independent study commissioned by the UK’s Renewable Energy Foundation (REF) has found that power generation by the UK wind sector varies enormously with location, and that even with a large installed base of wind turbines, results for wind power in the UK would be extremely spotty.

Although most wind power sites were built on expected capacity factors of around 30%, actual results include 19% (approximate) capacity factor for the wind turbines at Dagenham, Essex; 9% (approximate) capacity factor at the Barnard Castle plant, County Durham; and 7.7% for the turbine close to the M25 at Kings Langley, Herts at the HQ of Renewable Energy Systems, the green energy division of Robert McAlpine group—the worst results found.

Power generation capacities offshore are encouraging, while those onshore are generally only superior in locations very distant from the populations requiring the electrical energy.

Using this analysis, the researchers calibrated a model to project the performance of a large installed capacity of wind power built across the UK. The project used Meteorological Office data to model output for every hour of every January from 1994-2006.

The results show that, even when distributed UK wide, the wind power output is still highly volatile, with the average January power variation over the last 12 years equivalent to 94% of installed capacity. It is an uncontrolled variation decided by the weather. The average minimum output is only 3.7% or 0.9GW in a 25GW system.

Power swings of 70% in 30 hours are the norm in January, according to the results.

The British Government’s expectation is that three quarters of the 2010 renewables target, and the lion’s share of the “20% by 2020” target will be made up of windpower. However, the new research offers predictions which are in keeping with Danish and German empirical experience and demonstrate the need for a broader spread of investment in the renewable sector.

This important modelling exercise shows that even with best efforts a large wind carpet in the UK would have a low capacity credit, and be a real handful to manage. This isn’t the best way to encourage China and India to move towards the low-carbon economy. As a matter of urgency, for the planet’s sake, we need to bring forward a much broader range of low carbon generating technologies, including the full sweep of renewables. Wind has a place, but it must not be allowed to squeeze out other technologies that have more to offer.

—Campbell Dunford, CEO of REF

The report was commissioned from Oswald Consultancy Limited and funded by donation from the entrepreneur Vincent Tchenguiz. Tchenguiz is, according to the Times of London, with his brother among Britain’s richest people, with a combined fortune of £400m. The brothers made their money in property.

In November, 2006, Tchenguiz, with the Crown Prince of Abu Dhabi, established the £130m Abu Dhabi Masdar Clean Tech Fund to invest in renewable and alternative energy such as solar power. Tchenguiz has remodelled his £1bn business portfolio to invest in everything from low-carbon technology to forestry projects.

The Renewable Energy Foundation is a registered charity that funds independent research into renewable and alternative energy technologies and policy. REF is funded by private donations and has no political affiliation or corporate membership.

According to the Telegraph, a spokesman for the British Wind Energy Association accused the Renewable Energy Foundation of having an “anti wind agenda” and said it was “deeply suspicious” of the findings.

Resources:

These numbers are deceiving...

Capacity is a term from the hydro or nuclear energy sectors - where the energy source is on or off. For wind, capacity is when the turbines are generating at 100% of their rated output. Unlike nuclear, the wind is not on or off - it is an analogue. Just because the wind is not at 100% of the rated maximum of the turbine doesn't mean that the turbine is off, however that is what capacity reflects.

Wind turbines operating at peak capacity of 15% of the time is impressive. Remember that there is still going to be wind blowing another 40 or 50 or 60 percent of the time, and those lighter breezes will also generate electricity. Averaged over time the generators are likely generating power equal to 30% of their rated output if the wind was at the maximum wind speed all the time...

For a better explanation, have a look here: http://www.biofuels.coop/windblog/?p=111

This looks like another niche market for advanced weather forecasting. With numerous sensors, advanced software, and supercomputers (10-100 petaflop range), it may be possible by 2020 to efficiently exploit wind energy.
_Offshore wind farms in the North Sea may replace oil/gas in importance.

"Offshore wind farms in the North Sea may replace oil/gas in importance"

^^^I agree^^^^

I don't see how much use weather forecasting will be in this regard. The problem is that demand follows one variability pattern, while production from wind turbines follows another, and there is no good way to buffer the difference. With this sort of variability, a large installed wind turbine base would need a very large set of backup generators which can be brought online to meet demand on those days when the wind isn't blowing. One typical solution would be to build a large number of natural gas fired plants to back up the wind plants. Instead of running them full time, or each day during the peak demand period, they would be run when wind is low and idled when wind is high. But this is a very capital intensive way to implement alternative power -- you essentially have to build two power systems over -- and the costs of building all that (in time and carbon emissions) really eats into the savings that arise from avoiding the need to burn natural gas.

One way to avoid this outcome is to create buffering technologies using various energy carriers. A tried-and-true method is pumped storage hydroelectric power. When windmills are turning during moments of peak demand, the electricity flows to customers. When they are turning during off-peak moments, the electricity pumps water uphill. When they are not turning during peak moments, the uphill water is released to turn a hydroelectric turbine. Such a system is somewhat capital intensive, but it has the bonus of capturing and storing off-peak wind generation, and avoiding the burning of fossil fuels during peak demand times when the wind is slack. Hydrogen could be used in the same way -- off-peak generation creats hydrogen gas from water, which can either be fed into cars that burn it, sold to industrial users (refineries) that need it, or fed into fuel cells or generators to make peak electricity.

Britian is also a tought case. It is fairly small and non-diverse geographically. Variable wind-power generation can be offset by counter-variable wind power generation from some other location with different weather patterns (so long as you can transmit the electricity around the grid as needed), but you need geographic diversity, and line-losses that are not too overwhelming. Britian lacks geographic diversity to a certain extent, so even if you spread windmills throughout the country, there will be a substantial overlap in windy or calm conditions for all turbines. There will not be the offsetting variabilities needed to even out the system. The U.S., Canada and continental Europe might have slightly different cases.

"As unconstant as the wind," it would not be wise to depend on it for utility power generation. Sometimes, there are periods of days without significant wind, and it may not be practical or economical to build hydrostatic storage means big enough to bridge that gap.

However, the electricity from the wind can be used to generate hydrogen using high-temp solid oxide electrolyzer, using the high heat of a gas turbine power generating plant. In this fashion, electrical efficiency of H2 generation can be up to 140-150% of input electricity. Now, if this H2 will again be fed to a combine-cycle power generating plant at 60% efficiency, then 1.5 x .6 = 0.9, or 90%-efficient energy storage. Even battery or hydrostatic electricity storage can't beat that. Alternatively, the H2 can be sold as transportation fuel for a low cost given the high efficiency in H2 generation, and this is renewable H2.

Assuming transmission efficiency .92 from wind turbine to power plant, high-temp electrolysis efficiency 1.5, and ICE-HEV efficiency of .45, then the wind to wheel efficiency for an ICE-HEV will be= .621, or 62%

Now, for a BEV with an accepted home socket to wheel efficiency of .7 and transmission efficiency of .92 from wind turbine to home socket, then Wind to Wheel efficiency for BEV will be 64%. About comparable to the circuitous wind to H2 route! Without the high cost, and weight, and prolonged charging time of battery, and performance drop off of the battery due to extreme temperature.

Hydrogen is a dead end because it is so inefficient. Vanadium redox batteries can be used to store and resupply grid power. They are scalable, non-self-discharging, responsive in fractions of a second and over 80% efficient right now. Vanadium is relatively common, in fact a contaminant in some oil supplies, so it doesn't seem that resource constraints will prevent usage.

Roger, what kind of ICE using hydrogen averages %45 efficiency? Are any of these high-temp solid oxide electrolyzer doohickies in operation?

Hmm, South westerly prevailing winds? Would make sense to be on the west coast really not the North Sea. Hence plans like the Lewis wind farms are on the board.

Without a great deal more pumped storage (we have only about three of these spread in Wales (1) and Scotland (2)) then we would need a lot more spinning reserve.

Ultracapacitors are more and more widely used in wind turbines to compensate for momentary wind fluctuations and grid electricity failure:

http://biz.yahoo.com/prnews/061206/law078.html?.v=83

Vanadium redox batteries are probably the best ones for stationary energy storage applications. As a flow battery, it stores the energy in the tank of electrolyte separate from actual battery, and could be scaled-up for increased energy storage just by increasing of vanadium electrolyte tank. I happened to talk to guys from Vancouver-based VRB Power systems, and was quite impressed with their technology:

http://www.vrbpower.com/

Vanadium in diesel fuel is extremely damaging to engine components, and is removed from fuel. However, vanadium is not cheap, trading for about 40$per pound of ferrovanadium, which gives to specialty alloy steels amazing qualities: http://www.crumetals.com/products/CPM/index.cfm I use these steels for hobby knifemaking. Build a big, fat HVDC power line to continental Europe. Or better yet, to Norway where enourmous amounts of hydropower can be stopped at high winds and run full throttle at low wind. Hydropower is the ultimate load balancing technology. PHEVs is another option. When there is not enough wind power for charging from the grid, the ICE can be used. The variability of wind is not a show-stopper, but a challenge. The biggest challenge comes from the fact that the variability is present at time scales from seconds, hours, days to seasons and the solutions to each time scale is different. In Denmark, where wind already accounts for 20-25% of electricity consumption we have other options. First of all, we transmit a lot of power to/from Germany, Sweden and Norway. This works excellently! But a new options on the horizon is to use wind power in our district heating systems (via heat pumps, of course) that already have massive accumulators. This is another elegant way of absorbing most of the variability. It is not a problem to store enough heat for days or even weeks at a time, should that be necessary. In Europe, it is often either sunny or windy, with exceptions, of course. Wind and solar would complement each other and perhaps allow 2-3 times as much renewable energy for the same "net variability". However, vanadium is not cheap, It's also (not unrelatedly) not terribly abundant. http://minerals.usgs.gov/minerals/pubs/commodity/vanadium/vanadmcs06.pdf Maybe those offshore wind turbines could earn their keep by also acting as supports for polyamidoxime adsorber arrays, extracting vanadium and uranium from seawater. I listened to a podcast with the president of VRB. One of the interesting things he mentioned is that Vanadium is a byproduct of the tar sands operations in Canada and this is where they were planning on acquiring it from in the future. What about metering as a function of the time? Currently, there are generally two kinds of meters. 1. Not time related. You just count the KWh used and multiply by the rate, and you have your bill. 2. Time related, but only in segments. You essentially have a small number of meters: Meter_1 runs during 9am-5pm M-F for example, meter_2 runs 5pm-9pm M-F, and meter_3 runs nights and weekends. Then, they bill you for usage_1*rate_1 + usage_2*rate_2 + usage_3*rate_3. But what about: 3. Instantaneous time metering. What if the price of electricity was constantly changing -- by the second, or even shorter intervals. Furthermore, what if your meter knew the instantaneous price? Furthermore still, what if your meter could relay that information to your appliances? Then, effectively, you could set certain appliances to only run during certain times. Your alarm clock? 24/7/365 please. Your dishwasher? Sometime between 9pm-6am, and whenever "the system" thinks prices are particularly low. Charging your electric car? A total of 4 hours between 10pm and 6am -- "the system" chooses when, based on past and predicted price. Why is this good? Well, it allows users to shift their demand to the current supply. Not 100% of the demand, but some. Individuals could do it with washing dishes/clothes, and eventually with charging their EVs. Industrial applications would vary I'm sure, but generally speaking there'd be niche industries which could find huge savings this way. End result? By making demand flex more with supply, all you need is for the wind to blow some time in a time interval for it to be useful. Effectively, you're helping to make sure that electricity usage goes up when electricity is cheaper to make, and down when it isn't. When is electricity cheapest to make? When variable costs are$0 -- when its windy, when its sunny, etc. Since the problem with wind power is that its supply doesn't meet demand, you can either move supply (put wind farms in places where wind matches electrical demand) *or* move demand (encourage people to use electricity when the wind is blowing).

The first is tough. Maybe the second isn't so tough.

Thomas Pedersen;

Agree with you that very large hydro-electric reservoirs make excellent power storage and/or power balancing venues.

To fully complement variable wind + sun energy generators, the existing hydro power plants have to be 'over-equipped' with extra turbine-generators to supply excess power whenever the other sources (sun + wind) are down or in low production periods. Hydro plants over equipment does increase capital cost but it is acceptable when imposed over a very long 50 + years period. Interconnection of the two power sources is already being done efficiently with existing technologies.

Of course, widespread use of P2G could also help to balance power consumption and production. It would require some kind of automated charge-discharge control system to every PHEV connection to work effectively. Coupled with variable power rates, this is a very interesting solution. No really new technologies are required.

A combination of those two methods would work suffisantly well in many countries or regions. Hydro + sun + wind sharing can be implemented now and P2G within a few years (2010?) or as soon as PHEVs and EVs come on board in sufficient numbers.

Sucks to be them. Huh? Not much chance on solar. The southernmost point on the English mainland is the Lizard in Cornwall, which is about 49 degrees north latitude, that is the northern boundary of the western US states. My guess is that there is not much unused or marginal agricultural land on which to produce bio-fuels. Connecting to the mainland power grid means trusting the French, not a good policy historically.

Robert Schwartz,
The British Isles still has agricultural and biodegradable garbage, human and animal waste.

NBK-Boston,
As for the point of much improved weather forecasts, developed nations already have electric generation systems in position. You do not need a completely new set of power plants. Granted, you will need to upgrade them, in order to increase assortment of the fuels they can utilize (biomass, coal, CH4, etc), and to augment their startup/operational efficiency. However, to coordinate and optimize the entire system, you need insight to what is going to happen, to wind conditions, in the next hour, day, week, month, etc. With that approach, you will know when and where to turn on/off power plants, and when to trim production. Combined with pumped storage, it is possible to run a seamless operation, of which is predominately wind energy sourced. Much of the remainder may be tidal, wave, and biomass energy.

Ruaraidh,
I do concur that the Celtic Sea is a prime wind province. However, the statement I made about the North Sea was also referring to the gas, and oil there. As we deplete the hydrocarbon reserves, they will grow less important. Wind energy production situated there, has the potential to eclipse, and replace the fossil energy resources, that were once there. Furthermore, the North Sea is still a good location. If the farms are 12Nm out or more, the effect of land on wind is minimal.

A new class of wind energy generators would be able to overcome the main limitations of the present aeolian technology based on wind mills.

www.kitewindgenerator.com/

The project won the WREC (World Renewable Energy Council) 2006 award and seems they recieved from EU and other Authorities around 17 Mil.€ to build a 2 Mw test plant.
A mobile prototype is already working. You can see the movie and tech details on their site.
Their paper “Control of tethered airfoils for a new class of wind energy generator” is going to be presented at the 45th IEEE Conference on Decision and Control, San Diego, California - December 13-15, 2006

Wind power is a waste of time. The people in power know this but push wind to make it look like they are trying to move to a cleaner and more self reliant future. But meanwhile behind the scenes building more natural gas and coal plants.

Stormv,

You have just described perhaps the most important technology required to realize the untapped potential of flexible power consumption. This would, without a doubt, lower the average cost of electricity.

Harvey D,

In my mind, hydro power should be used solely as load balancing power, of course respecting min and max flow limits downstream of the power plant (and upstream, if there are any limits). Hydro power is potentially capable of load balancing on time scales from minutes to seasons.

I would like to mention something else. If/when electricity from renewable energy becomes our primary source of energy, the fraction of must-have-right-now power (for cooking, lights, tv, etc.) will drop significantly. This means that the number of occasions where production dips below this type of consumption becomes much rarer and much less relative to average power production. The remaining fluctuations in production will be soaked up by PHEVs, heating & cooling, washing, drying, dish washing, etc. In doing all this, a very high percentage of renewable energy should be possible.

Look in this link to a recent GCC article re-H2-ICE engines: http://www.greencarcongress.com/2006/09/the_arguments_f.html
Ultralean multimode H2 combustion with complete combustion can get you 45% efficiency. Diesel already got ya 42%, and diesel combustion is slower and not as complete, hence not as efficient as H2 burning.

aa2,
How is wind power a waste of time? Large-scale wind electricity costs as low as 5 cents/ kwh, which is competitive with fossil fuel power plants. If you would use the electricity to produce H2 using the most efficient electrolysis method available, then wind energy is a very cost-effective to produce renewable fuel. Even cheaper than solar.

Have any BSFC maps? I'm somewhat wary of a single efficiency figure (ala the Prius), and EVs tend to have efficiency ranges of something like 85-90%. If the H2-ICE is anything like other ICEs, and efficiency drops with load, then the established electric motor would have a significant leg up on the H2-ICE.

The established electric motor will always be more efficient to any heat engine, which is subjected to the limitation of the second law of thermodynamic. However, the process in which electricity is generated is in turn subjected to the second law of thermodynamic, and will always be much less than 85-90%, more like 35-55%. Even wind turbine is a component of a heat engine using air as working fluid from the heat supplied by the sun.

The efficiency of an ideal Otto-cycle with compression ratio of 10 is above 60%. An ICE using direct H2 injection and high compression ratio of ~14 can get its ideal-cycle efficiency even higher, near 70%. Now, why is the efficiency of the auto engines only 30%? The answer is heat loss thru the cylinder wall and cylinder head accounts for 30-35% from fuel in a stoichiometric combustion. A diesel engine at part load (low equivalent ratio) with a spray of fuel at the center of the combustion chamber has air around it acting as an insulating blanket. Diesel heat loss via coolant is only 18% of fuel heating value. Repeat the same with H2-direct injection at low equivalent ratio (ultra-lean combustion), and you'll get the same low heat loss due to the air blanket, hence high efficiency like Diesel engine, only higher, since H2 burns faster, hence more power released early in the power stroke that you can see in the PV diagram, and H2 burns more complete without any soot. At high load, you simply turbocharge the engine to get the ultra-lean combustion by forcing more air into the cylinder. Same old trick used in Diesel engine, except with H2 you'll have no PM and HC and CO2 to worry about.

Now then, it is the job of the hybrid drive system to ensure that the engine operates within a high-efficiency regime. With H2, it's not hard to do, as the engine can run efficiently at a wide range of power setting. By putting the heat engine delivering power right to the wheels with minimum transmission loss like in the Toyota HSD, you will bypass the efficiency loss in power transmission, in the charger, in battery internal resistance, power controller, and resistance in the motor windings... A BEV has a well-accepted grid-to-wheel efficiency of ~70%. So, a ICE-HEV with efficiency of even 37 % like the Prius can still beat a BEV from well to wheel (fossil fuel to wheel). Coal-fired power plant has efficiency of only 35-40%. Combined-cycle gas-fired power plant can do 55%, but when considering the losses, .55 x .7 = 38.5%, still quite comparable to the Prius. I believe that the Japanese version of the Prius II has the engine turns slower at cruise than the American Prius II, hence efficiency of 37% can be realized without having to wait for more durable battery technology.

Take home point: H2-ICE can have higher efficiency than diesel. Since diesel is already 42%-effcient, 45-50% for H2-ICE is not far-fetched. No other fuel can burn as lean as H2. None!

BSFC maps?

Roger:

Detailed thermodynamic calculations of ICE cycles were done about 100 years ago, and since then major discussion is closed and the results are routine part of ICE thermodynamic course for engineering students.

Theoretically you are right, instant combustion yields more useful mechanical work than slow diesel combustion – at same compression ratio. Reality is different.

Limiting factor of ICE design is engine mechanical integrity, which effectively limits max combustion pressure. Now, when you have mechanical limitations, you can choose between 14:1 CR engine with instant combustion (self detonation limitations aside), or 18:1 CR engine with slow diesel-like combustion, and both will be at the engine limit to handle max pressure. And guess what, second one will be more thermodynamically efficient than first one.

It is possible to twinkle with separate parameter of ICE and predict very good results. However, all processes in ICE are interconnected, and gaining in one aspect you invariably losing in another. Increase of compression ratio beyond 24:1 is calculated to have negative effect on efficiency. Leaning mixture, you increase energy drain to move in and out and compress bigger masses of air. Faster combustion of hydrogen in SI engine means you have to reduce compression ratio to suppress detonation. Add hydrogen to diesel engine intake to speed-up combustion, and you just dig into engine safety margin. In fact, modern high-pressure fuel injection systems on diesel engines have to inject fuel in couple of events – just to prolong combustion time and to avoid too much peak pressure rise. Increase RPM – and friction losses are going through the roof. Insulate combustion chamber, and you have to decrease compression ratio to suppress detonation, and most of the gains any way will be lost in hotter exhaust.

I do not even mention NOx formation limitations, which are of uppermost importantce to high-compression lean combustion (diesel included) engines.

The last biggest achievement in engine technology is direct injection stratified charge gasoline engines. It allows to raise CR from 10 to 12, and with upcoming NOx adsorbers promises to reduce significantly part-throttle pumping losses. Any other improvements in ICE efficiency are incremental steps to reduce parasitic losses, like friction (offset crank on Prius and Honda Hybrid), heat losses (combustion chamber coating), valvetrain/water/oilpump/alternator losses, and alike. Variable transmissions allow for deeper Miller and Atkinson cycles, homogenous charge compression ignition is about lowering of emissions, not really about increased efficiency.

All improvements are very small, and there is no way to increase ICE efficiency anyhow dramatically even theoretically.

Allen_Z,

My point was simply that in a scenario that involes a lot of wind generating capacity, you need to maintain in readiness an amount of non-wind generating capacity equal to your highest peak electrical demand, as well as maintain the transmission interconnects necessary to support all that. You do this so that when a peak-demand moment comes along when the wind is not blowing, you don't have to black out your customers.

It is hard to argue with the fact that weather forecasting makes the operation of such a system smoother, somewhat cheaper, or even technically possible in the first instance. The further ahead you can predict both supply and demand, the more options you can keep on the table for managing both. If you can predict shifts in the wind 6 hours in advance instead of 1 hour (to invent an example) you can use a power plant technology that requires 6 hours to warm up to full capacity, instead of going with the technology that can be brought up to speed in 1 hour. The 6 hour technology might be cheaper or better in some respect, so improved forecasting helps in that regard.

But that spare power plant -- using one technology or the other -- still has to be built and maintained to accomodate peak demand, and that is a capital-intensive, and therefore expensive, proposition. Given that reality, I then argued that pumped storage hydro, hydrogen gas generation, fixed batteries, or something similar, are probably the best candidates under the circumstances. First, they allow you to capture off-peak wind generation, which a wind-fossil combination would not allow -- off-peak wind would simply be wasted, there. Relatedly, when pumped storage or hydrogen gas are drawn down to meet peak demand on a low-wind day, they release no emissions.

It might be the case, though, that there is not enough off-peak wind generation to charge these energy storage devices to allow them to supply all the peak-demand electricity they will be called upon to supply. In that case, fossil power would need to be used to make up the difference. The advantage is still that the needed fossil-derived electricity can be produced during the most advantageous off peak hours and stored.

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