Upgrades: Optimisation during ongoing operation

Thu, 01/02/2018 - 12:02

The weaknesses of a turbine become apparent especially during routine servicing operations. (Photo: psm)

It takes an average of two years of work to bring a new wind turbine onto the market. This is too little time to test each component in detail. But no problem: updates can improve the yields and cost structures of existing turbines.

The speed at which manufacturers are bringing new wind turbines onto the market these days is breathtaking. A model hardly achieves a noteworthy number of installations before Gamesa, Nordex, Senvion & co. present the next generation of the “old” turbine. A development time of just two years stands against an operation lifetime of over 20 years. Development is so fast that there meanwhile seems to be almost no time for working on details.

It is thus good that an installed turbine is not an unchangeable construction, but one which can be further improved during operation through updates also known as retrofits. The optimisations have differing aims depending on the approach; they can increase yields, prolong the lifetime of a turbine, optimise the servicing or improve turbine safety.

Accordingly, the players in this field and their products are as diverse as the aims. They range from electronic updates and construction parts to additional sensors and measurement systems. Upgrades are on offer from manufacturers just as from service providers, suppliers and innovative start-ups.

Service providers recognise weaknesses

Independent service providers are in an ideal position to develop upgrades for existing turbines. Through their regular service and maintenance work they get really close to the weaknesses of a turbine and can detect the components with faster wear and tear almost as an aside to their daily work. They thus develop a fine feeling for which products make their work easier or can generate additional value for the operator.

At psm Nature Power Service & Management, for example, an upgrade associated with the blade bearings is primarily in demand right now – a blade bearing monitor developed by the Nuremberg-based rolling bearing specialist eolotec and exclusively sold by psm. The “Blade Bearing Guard” (BBG) is an early-warning system which can be retrofitted to all conventional wind turbine types. “Customers are almost kicking down the door to get one right now,” says psm head Ian-Paul Grimble.

“We have a lot of turbines in our portfolio which have seen damage to the blade bearings after ten years of operation,” he adds. Grimble expects a tendency towards increased blade bearing problems in the future and formulates his scepticism pretty clearly: “The future will show whether the loads calculated for the bigger rotors are sufficient. But given the prevailing cost pressures, no manufacturer today will be working with huge reserves.” The development and installation of blade bearing monitors was a logical consequence of this.

However, a bit of luck is also always required to have a successful product. A few years ago psm wanted to get to grips with the water content in transmission oil and pushed the idea of installing a venting dryer. Grimble admits here: “It didn’t reach the levels we envisaged.”

The company Deutsche Windtechnik also offers a wide range of optimisations, including for azimuth systems, pitch systems, the main bearings, the controls, the generator and the gearbox. Since last year it has offered an upgrade to the control unit of the Senvion-MM series. The new CSC4 control unit by the inverter manufacturer Woodward aims to avoid inverter faults and potential problems with getting replacement parts for the old controller. “Yield losses due to a lack of replacement parts or even a replacement of the whole inverter would be much more costly, which is why we strongly recommend the upgrade in light of the future spare part supply situation,” says Dirk Henning, head of Engineering at Deutsche Windtechnik X-Service.

Automisation technology provides many approaches

The field of automisation appears to offer sheer inexhaustible opportunities for optimisation. The reason for this, however, is at times unpleasant for the operators. It is often the much criticised poor accessibility to the controllers which forces operators to go for upgrades. Gabriel Schwanzer, director of the wind power section of Bachmann electronic, can tell you a thing or two about this. “Upgrades are often necessary because the required data is not available and the operators or service providers cannot access the system at the levels they need,” he says. This can make the installation of a parallel condition monitoring system necessary, for example. Depending on the turbine type the existing sensors may or may not be usable, but even a completely newly installed system can pay off for the operator, says Schwanzer.

In other cases it can even make sense to replace the entire control electronics of a turbine and put in your own SCADA system. But then legal matters appear apart from just the technical challenges; does a yield-optimised operation through the new controller change the loads on the turbine? Is a new certification possibly required because of this?

By this point at the latest something becomes clear which not only for Bachmann always stands right at the beginning of upgrade development: the business scenario for the customer. Obviously, an upgrade only makes sense if the expected profits or reduced costs are higher than the investments. “This is almost always the real and biggest challenge for us: making a business case for our clients,” says Schwanzer. 

Economic viability is hard to measure

The "Blade Bearing Guard", an early-warning monitoring system for blade bearings, enables the permanent monitoring of wear and tear. (Photo: psm)

Assessing the economic viability of updates is indeed a real challenge, for although the sector is largely convinced of the usefulness of upgrades, it is very hard to prove their concrete value. Take upgrades which serve to optimise costs, for example. They usually save costs because damage is avoided, but it is impossible to measure an event which doesn’t happen.

Yield-improving upgrades face similar problems. They are “really really hard to measure,” says Grimble. To prove their economic viability the turbine would have to be specially measured beforehand and after. This would result in additional costs without a concrete value gain. Even test turbines are not a 100 % reliable proof of the viability on your own turbine, says Schwanzer.

All the suppliers can do is to communicate well with their customers and convince them with trust built up over time. Grimble confirms that operators certainly have an interest in optimising their turbines: “You do have to push firmly on the door, but with enough of a shove you can get in,” he says on the willingness of his customers to invest in upgrades. For an operator to then actually put up the money for the upgrade, you ultimately need the necessary trust to be there, however.

Digitalisation enables intelligent turbines

At the latest when the business with new turbines in Germany began to falter, but the existing stock wanted to be optimally serviced, was when turbine manufacturers discovered the upgrade business for themselves. At the same time as the service business is growing in importance for them, so is retrofitting. In this the turbine manufacturers have the advantage that they really do in principle have access to all the turbine data, as opposed to operators or independent service providers. They are thus logically glad to use this field and supply software upgrades, for example.

All manufacturers are trying equally to increase the yields of their existing turbines through electronic upgrades such as “Energy Thrust” (Gamesa), “Power Boost” (Siemens), “Turbine Control Upgrade” (Senvion) or “Xtended Power” (Nordex). Now Siemens Gamesa is taking a look at the loads over the entire lifetime with a product which it presented just last November. “Dynamic Power Curves” make it possible to fully utilise the load boundaries of a turbine at times when the feed-in tariff is high: even to exceed them slightly. At times of low remuneration the turbines can be operated sparingly enough to ensure that the envisaged lifetime is not put in doubt.

Behind this lies a digital load management which observes and controls turbine operation in the long term. In this it is more of a concept than a specific product. “A traditional power curve understands energy as being exclusively a function of the wind speed. In reality, however, it is a function of many variables and the turbine must adjust flexibly to changes in all these variables,” says Cassia Pole, Head of Strategic Portfolio Management at the Onshore business unit of Siemens Gamesa. For the future, Siemens Gamesa thus envisages a turbine which can continuously monitor and control its operation conditions and grid requirements on its own and adjust the power accordingly. This intelligence is based on data collected from sensors, although in the future external data sources such as market prices and weather forecasts are also to be included.

And once again, here in connection with upgrades for wind turbines, you cannot avoid the trend subject of big data. The “Dynamic Power Curves” from Siemens Gamesa already show how much you can do with the available data. But this is certainly just the beginning of a whole stream of developments. When the multitude of data from a turbine really begins to be systematically analysed, a whole lot of development potential will open up in the field of maintenance too. Digitalisation, especially in existing stock, will enable a multitude of optimisation opportunities.

Katharina Garus