Case study: perfect incubation for wind

  

A question we often hear asked is 'Why isn't wave energy commercial yet? Is there something fundamentally wrong with it?' The question is both really interesting, and a pain to get asked: there is no simple answer, everyone has a different take on this, and often the person asking just wants a simple thumbs up or down. 

Wind energy can be a useful analogy, especially for those of us ancient enough to have watched as it 'grew up', and to remember the same types of doubts directed at it. There are several techno-economic ideas (see Glossary for definitions) that are familiar when applied to wind energy, which we can then use as lenses for looking closer at wave energy.

R&D incubation

In the 1940-1970s there were all sorts of wind turbine design. By the 1980s, there was a noted convergence on the three-bladed 'Danish design'. One Danish company in particular is recognised as an innovator: Vestas. Here is a potted history, highlighting the approaches they got right, and the conditions that allowed them to innovate and survive. 

By the 1970s, the Vestas company was an established manufacturer of cranes and coolers. They invested their profits into exploring new products. In response to the 1970s oil crisis, they secretly developed a prototype 'egg-whisk' type wind turbine, but weren't satisfied with the result, so collaborated with independent inventors who had developed a three-bladed design. Vestas' financial security meant that they didn't have to rush development. Rather than investing into getting a their first candidate solution ready for market (high TRL), they assessed its potential for high performance (high TPL). The graph above shows that the three-bladed design has a more useful power coefficient than the Darrieus, a relative of the egg-whisk that they first explored.

Innovator market: robustness first

The concept of 'Innovation Windows' (right) is a useful framing to describe what happened once Vestas started selling turbines and introducing improvements. At first they focused on making their design robust – including moving the construction of unreliable components (blades) in-house. Notably, they responded in a transparent and responsive way to early failures - the reputation and culture of their parent company no doubt made this necessary, while its economic safety net made this possible. The turbine design could be described as agricultural, and it suited the needs of an early market: Danish farmers who needed robust maintainable kit. This market was heavily incentivised by Danish tax rebates for wind power generation.

An 'early adopter' boom and bust

The timing of the notorious Great California Wind Rush was fortunate for Vestas: it allowed them time for 'technology learning' (i.e. cost reductions), as they were making hundreds of identical wind turbines a year for these early adopters. The support mechanism was for installed capacity rather than power generation, so the Wind Rush is mainly remembered for the speed with which most of the turbines installed by their competitors broke. There was no doubt learning to be had about what not to do, and this may have influenced their continued focus on robustness.

Control to increase capture and shed loads 

 

Their first innovation window was introduced five years into the California Wind Rush: pitch control, initially just for the blade tip. The graph to the right compares the power curves of a pitch regulated wind turbine with the older passive 'stall' method. The stall power curve is shaped like a rolling hill, whereas pitch gives a mesa-shape. This improves the economics in several ways:

• At below-rated operation, the maximum power tracking is improved, 
• rated power is attained at lower wind speeds, 
• the loads during rated power are lower, 
• and there is a steadier 'rated power' . 

This innovation secured their competitive lead, but their success nearly killed them: in 1985 the shipping company charged with delivering a thousand of their turbines to California went bust , and Vestas only survived by splintering from their parent company with a much-reduced workforce. 

 

 

  

Capacity factor as an sub-system sizing optimisation

Over the next decade they produced new models with conservative improvements in design and size. By the 1990s, their experience of scaling up turbines and operating at a variety of sites allowed them to improve the relationship between blade diameter and generator ratings, resulting in capacity factors of around 25% - 40%.

 For thermal plant, such capacity factors are an indication of poor economic utilisation (hence the typical propaganda above). However, for wind energy, capacity factor reflects a sub-system sizing that optimises LCOE. To visualise this, consider the wind power curve below: 

 

• You could increase the capacity factor by putting bigger blades onto the same electrical generator. The effect would be to shift the below-rated power curve to the left. Although you are improving below-rated efficiency (Region 2), this might not be economic because for a significant amount of time (rated, Region 3) you'd be throwing away a lot of the energy that could have been captured, so you might not get a good return on those more expensive loads that will attract higher loads.
• You could decrease the capacity factor by putting smaller blades onto the generator. The below rated power curve would then shift to the right. Then for most of the year you are operating at below rated with low efficiency. Meanwhile you still have the same expensive generator.

Clearly there is a sweet spot that is economically driven.

By the 1990s most other turbine manufacturers were offering very similar designs. Vestas responded by drastically reducing the blade weight. Their blades had been over-engineered in response to previous blade failures, but operational experience allowed them to narrow their safety margins and their in-house blade manufacturing made this possible.

Enablers for the majority market

A third innovation that their own website is proud of is power regulation. In the mid-90s they introduced a new type of generator that smoothed the instantaneous power output during rated operation: blade pitch alone was too slow to deal with sudden gusts of wind. The poor power quality had limited how much wind energy could be grid connected, so this allowed wind power to make a significant contribution to the energy mix.

Another limit to grid penetration was turbine size: this appeared to have converged at around 500-600kW. In the 90s, Vestas was one of the first companies to sign up to an EU led drive (WEGA) to solve technical barriers of MW scale turbines, which pressurised their competitors to join. A common measurement programme and a high degree of collaboration resulted in technical improvements (e.g. gearboxes) that enabled larger wind farms: larger turbines are need to reduce the proportion of 'balance of plant' costs.

We are presently on the offshore wind 'S-curve' which is taking over from onshore wind as land sites become more limited. Again Vestas were the first company to gain experience in this, building an early demonstration array in 1995. 

Summary of Vesta's journey

To summarise, the following conditions and design choices allowed Vesta to remain market leaders as the technology evolved:

• A well-funded unrushed R&D programme that made it possible to explore different solutions and openly respond to teething problems.
• A trusted relationship with their 'innovator' market, buoyed by domestic public support for power generation.
• A robust and simple market-entry design. 
• In-house of development of components specific to wind turbines (blades). 
• An early adopter market with an opportunity for cost reductions principally due to mass production (rather than technology improvements or increase in turbine size).
• Innovating control to increase capture and shed loads - resulting in a more complex design. (Interesting that pitch control applies to the first part of the wind-to-wire process: it allows the turbine to selectively decouple from the resource.)
• Optimising blade design only after a decade of operational experience.  
• Capacity factor as a sub-system sizing optimisation: access to long term production data from many sites, and a focus on driving down LCOE, resulted in this convergence for the whole industry during the 1990s.
• Innovating control to improve rated power performance. (Interesting that power regulation applies to the final part of the wind-to-wire process.)
• A limited collaboration with competitors to overcome common technical barriers put the wind energy market as a whole on to a course to being cost competitive with fossil fuels

In response to the question about the commercialisation of wave energy, the first thing to observe is just how different the culture and focus of wave energy development is. It is interesting to ask what the wave energy equivalent of each step is, and this will be the focus of a future blog post. 

 

Credits

This blog was written as a first step in generating material for the AIM-WEC project, at the University of Heriot Watt. 

Many of the ideas were borrowed from a talk by Andrew Garrad, that I have dissected elsewhere; amazing how it has not gone out of date!

The title image was from a website that appeared to be AI generated, too wierd to link to, but thanks for the cute picture.