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.