power-line mounted turbines?

Check out this winner of the 2008 red dot design awards by Nils Uellendahl, it's a concept for a helical turbine that mounts directly onto over-head power lines. It's quite interesting in two ways:

• it generates electricity directly into the line using induction
• It's actually horizontally mounted, however is actually a traditional vertical-axis turbine

I'm sure there are some large issues with the electrical connection and grid stability (to say the least!), and with the additional loading of the power lines, however it's a great concept.

24 October 2009 - an international day of climate action

In preparation for the December '09 Copenhagen round of international discussions on climage change, 350.org is busy preparing local actions around the world on the 24th of October to reiterate the goal of a return to 350ppm of CO2 - a worthy aim for any climate change negotations indeed!

The Copenhagen round will be keenly watched by the renewable-energy industry, as it could well provide a huge boost to meet any meaningful CO2-reduction target. It's fair to say that the wind industry will be set to receive the lion's share of any boost, as it's commercially the most ready technology we have available at the moment. A 2010 boost would be welcome news to an industry that is starting to feel the effects of the GFC through hard-to-find financing.

Big rotors king for 2010+

A few years back, it was quite common to see various turbine manufacturers releasing their latest Class IA turbine, followed rather quickly with a class II and III rotor. This was typically just a longer blade with minimal nacelle changes. The Vestas 2WM, Siemens 2.3 MW, and GE 1.5 MW platforms are good examples of this.

This was understandable at the time, as there were numerous easily exploitable IA sites around, with demand in the market for suitable class IA turbines. However now in 2009, as we are rapidly shooting past 100 GW of installed capacity around the world, the number of high-wind sites that are also close to the grid and easily developable are becoming quite rare (although there is no shortage of high-wind sites in the world) - a quick chat with any developer will tell you that! The dominant sites for 2010+ are looking to be for class II and class III.

Preempting this, we are seeing the latest generation of turbines being released with this in mind. No longer are turbine manufacturers jumping straight in with their smaller-rotor IA machines. The first release looks to be the II/IIIA specific turbine, with the IA coming later as an after thought (if at all). Have a look at the new Repower 3.xM, Vestas V112-3MW, and GE 2.5XL. Adding to this the last iteration of existing nacelles with new class III rotors: Siemens 2.3-101, Vestas V100-1.8, and the Nordex N100-2.5 ; big rotors are set to be king for 2010+.

Picture of the SWT-2.3-92 I took in the US.  Progression from Class IA (82m rotor) to class IIA (92m rotor) to class IIIA (101m rotor) in around 5 years.

density correction of stall-controlled power curves

For energy estimates at non-standard IEC conditions (p=1.225 kg/m3), the power curve should always be density corrected. For stall-controlled turbines this can be quite tricky.

If you follow the IEC 61400-23 recommendations (which are for power-curve testing) then a simplistic ratio approach is recommended. However, this standard is intended for normalising datasets at 'near sea level' conditions - not for detailed energy estimates. In reality, a stall-controlled turbine will be tuned for site, with the pitch setting feathered for lower density so that rated power is always hit.

For example, if we take a 2000m site (p=0.99 kg/m3) and correct it using IEC measurements we see a large decrease in energy (around 25%) - whereas the actual power curve will be around 10-15% decreased after adjusting the pitch settings. In this case, the pitch settings were feathered by around 2 degrees to achieve this power curve.

Therefore, the site-specific power curve should always be used for energy estimates, and this should be sourced from the manufacturer. For sites at higher altitude (I would say above 1000m), then tested power curves should be insisted on as the aerodynamics of the turbine will change (particuarly for stall-controlled turbines) which invalidated the original testing. I'll go into more detail on stall-controlled turbine aerodynamics in a future post. 

Clean-coal busters - this is reality strikes back!

I love it, the organisation thisisreality.org have come back with a vengeance at all that clean-coal spin! Check out their website to see how they are trying to educate the public and dispel the mistruths of the glossy clean-coal spin doctors! 

The credit-crisis for engineers

For those of you developing wind farms right now, I'm sure you are well aware of the scarcity of credit at the moment, making it difficult to finance wind farm development.  Even for no-brainer projects with excellent wind resource, great grid connections, and full planning permits - it's difficult to pry any cash from lenders' white-knuckled hands. 

The very talented Jonathan Jarvis has done a great summary of the credit crisis as part of his thesis, allowing even the pragmatic engineer that doesn't like to get involved with the rubbery and subjective world of finance to understand!


The Crisis of Credit Visualized from Jonathan Jarvis on Vimeo.

The destructive spin of 'Clean coal'...

If you're reading this blog, I'm preaching to the converted, however there is a great article in Scientific American here summarising the destructive spiral of events that the supposedly 'clean-coal' technology has had on the planet. 

'Clean-coal': lot's of spin and hollow promises from the coal industry that not only is delaying renewable-energy development, but actively blocking it with hundreds of millions of dollars of spin and lobbying in the US alone (let's not even talk about all that wasted 'research' funding subsidies the coal industry is receiving) - the ever distant promise of clean coal, let's just do nothing until that arrives. Sounds very familiar to other fairy tales of the modern age like hydrogen-powered cars, and cold-fusion generation to name a few. 

It doesn't take a genius to figure out that it won't be cheaper to run a coal-fired power station whilst:

• scrubbing all of the CO2 out of the emissions (that's over 11-billion tonnes a year), 
• compressing the CO2 (yes, the same 11-billion tonnes every year)
• transporting the CO2 to a suitable storage site (how do you transport 11-billion tonnes of CO2a year anyway?)
• pumping and storing that same CO2 underground so that it won't leak... for all future generations of mankind (that's more stringent than nuclear waste storage, however there's 11-billion tonnes of it every year to deal with)
  

How stupid does the coal industry think the public are?? Obviously fairly stupid. For a great laugh, check the latest spin commercial from the US coal industry (are there people out there that actually buy this??). Oh man, I would love to meet one of the geniuses in the marketing team behind this one... 

High-wind hysteresis losses explained

For anyone who has been presented with energy-estimate reports, a little entry called 'high-wind hysteresis' in the losses table is often brushed over. I've seen values from 0-4% depending on the site, so what actually is it?

In simple terms, it's the turbine's control-system lag between shutting down in high wind speeds, and starting up again. Most modern pitch-controlled turbines will shut down at 10-minute average wind speeds above 20-25m/s, with 3s-gust speeds a little higher than this (typically around 5m/s higher); to prevent the turbine from starting up again during the high wind (just to shut down again), a re-start speed of around 5 m/s less than this value is specified. Physically, this is controlled through discrete parameters in the turbine controller that specify this number.

An example of this is shown below in some historic 10-minute average hub-height wind data:

 

If we assume a modern turbine (such as the V90) was running here, the turbine would shut down at 25m/s and remain shutdown until the extreme event had passed and decreased below 20m/s. However from an energy estimate perspective, if we are running this data through a power curve, the turbine is assumed to be producing energy whenever the wind speed is below 25m/s and therefore doesn't consider this data. It is this value that we are trying to estimate.

This analysis should be conducted on a representative time series of at least a year to be meaningful. To provide a more detailed analysis, the 3s-gust speeds should also be used, as the turbines will often have a higher 3s-gust shutdown or startup speed; so both scenarios can be considered together, and a more accurate hysteresis loss estimated.

Empirically, the higher the wind speeds and the 'gustier' the sites (particularly inland mountainous sites), the higher the hysteresis loss that can be expected.

Energy Revolution blueprint - wind energy practicalities

Greenpeace has issued their Energy Revolution blueprint to provide a basis for reducing mankind's CO2 emissions. 

There's some great stuff in their blueprint, too much to go into in any detail here, however a key part of their energy strategy involves wind energy. In fact, they recommend increasing fromcurrent levels of around 100GW of installed capacity, to 2733 GW in 2050! This will require a massive increase in: identification and development of sites, local government approval of projects, production of wind turbines, and development of grid infrastructure. A great challenge for our industry indeed!

I've done some rough calculations based on the supplied data, and some of my ideas are:

• We will need to significantly ramp up the wind industry in the next few years to meet this target of 2733 GW - more than tripling our current rate of installation to around 60 GW per year. That would involve installing around 30,000 2MW-turbines every year, being around a thousand projects commissioned every year - that's alot of sites that need development.
• Onshore wind will definitely be key, however offshore wind will need to grow significantly to around 20% of the total by 2050 - 547 GW of offshore wind energy, that's thousands of large individual offshore projects. Significant development in site acquisition studies, and energy estimation will be a key element of this.
• This will transform the wind turbine-manufacturing  industry from around US$30b/year today to over $100b/year! Plenty of room for new manufacturers, and novel design concepts. Reducing the capital cost will be the key driver, with smart developers looking at the realistic and accurate costs for generated energy over the projcet's life ($/MW.hr) 
• Operational and Maintenance (O&M) will become a serious industry, from current levels of around US$4b/year to US$100b/year in 2050.  This will be a serious industry, surpassing the turbine-manufacturing industry, and resulting in some interesting market and industry movements. Maybe the wind industry will go the way the aircraft industry went, with more money in operations, and leasing being the predominant business model?

Ambitious targets, and exciting times for the wind industry.  Our future energy needs will require a portfolio approach, with the renewable-energy industry being increasingly important with all its different technologies healthily competing to displace the old-world technologies. 

The true cost of coal

"Coal burning contributes more to climate change than any other

fossil fuel. Coal-fired power stations pump vast amounts of CO2

into the atmosphere each year, 11 billion tonnes to be precise.

This amounts to 72% of CO2 emissions from power generation

and 41% of total global emissions of CO2 from fossil fuels."

Greenpeace has released a great report: 'the true cost of coal'  looking at the true cost of using coal for electricity generation.  It takes  a good look at coal use throughout the world, and some of its current and future affects to the environment. Some of the key points I took out of the report were:

• Coal use is our single biggest emitter of CO2
• Coal is used for 40% of the word's energy supply - and expected to rise
• The true annual cost of coal use has been estimated at EUR360 billion in 2007 - with an estimated 150,000 deaths! That would pay for 3 times our total current level of wind energy - in a single year.
• Australia has a dirty history with coal, being the world's largest exporter, and relying on coal-fired power stations for 80% of its energy supply. 
• Carbon Capture and Storage (CCS) is a false promise from the coal industry, with more of a focus on diverting public attention away from coal's current and future impact. CCS is not expected to be commercially available until at least 2030, and even this is technically unproven, will drastically increase the cost of coal-fired power generation, and it is still unsure how all this CO2 will actually be stored safely underground... for ever. The sooner we drop this red herring the better.   

My next article will focus on both the: Greeenpeace Energy Revolution blueprint to radically reduce CO2 emissions; and the IPCC assumptions for energy supply for the various scenarios. And what this means for wind energy.