LiTEplus Lifetime Extension
13 Questions. 13 Answers.
Everything you wanted to know.
As part of our LiTEplus expert panel, we collected your questions and answered them below.
If you have any more questions, then please do not hesitate to contact us!
Questions & Answers: Lifetime Extension
1. How is measurement technology installed?
For a standard installation in the typical steel tower system for which LTE is currently relevant, four CLS strain sensors are installed at the base of the tower to measure the load in two directions. The sensors are bonded to the tower wall without compromising the corrosion protection. They are then connected to a small data acquisition unit housed in a small control cabinet and magnetically attached to the tower wall.
2. What are the infrastructure requirements in the plant or wind farm?
The unit requires a 230V power supply and transmits the pre-evaluated data to a Bachmann server. The data can be transmitted either via a suitable wind farm network and the farm router or via a separate UMTS router, which we can provide as an option.
3. How long does it take to install the system?
System installation is quite simple and can be completed within a few hours.
4. Can we do the installation at the same time as the lifetime extension inspection?
Ideally, installation is carried out as part of the practical lifetime extension inspection, making it very cost effective. In addition, downtime of the inspected system is minimized.
5. Are there additional efforts for monitoring the measuring systems?
All measurement support services as part of the lifetime extension inspection are included in the LiTEplus package offered by Deutsche Windtechnik. In addition to on-site installation and commissioning, this includes system configuration and continuous data acquisition and storage over a period of approximately 6-12 months (seasonally dependent on the start of the measurement), as well as the provision of data to P.E. Concepts after data acquisition. This is all part of the complete package for data-optimized in-service testing, which is completed with the delivery of the in-service report.
6. Are there other reasons to continue to monitor the system after the lifetime extension inspection?
By monitoring the system during the continued operation phase, risk can be minimized through early detection of structural changes, such as shifts in natural frequencies or early monitoring of damage loads. This makes it possible to detect and evaluate changes in normal behavior.
Ultimately, this allows for better planning, especially with regard to economic decisions during the continued operation phase. In addition, the load history is continued, which allows a repeated assessment of any remaining lifetime reserves at the end of this phase. Another aspect can be the avoidance or minimization of conservative operating restrictions and associated yield losses, e.g. in the case of changes to the turbine layout (e.g. additions, repowering), which have an impact on the individual turbine load and thus on the remaining useful life.
7. How long is the measurement period before the lifetime extension report can be generated?
Depending on the location, a measurement period of approximately 3-6 months is sufficient to collect enough data for evaluation. In the first LitePlus projects, 3 months was sufficient. Therefore, at least six months should be allowed before preparing the report. In general, the longer the measurement period, the more accurate the results.
8. By when would LiTEplus have to be installed in order to determine the best load reserves (in relation to the time of the analytical assessment)?
In general, it is worth making a statement about the remaining useful life at an early stage. For example, an installation may have a certain life expectancy that does not materialize even after measurement. In this case, operating restrictions can help to reduce load on the system. Smaller losses in annual energy yield are accepted in order to extend system lifetime and optimize overall yield. The earlier such measures are taken, the more effective they will be - once the system has experienced a load, it cannot be changed retroactively.
9. What data do we need from the SCADA system for the evaluation?
The evaluation procedure is designed to be robust, as older generations of turbines in particular do not always provide all the data one would like from the SCADA system. However, at least the 10-minute data on wind speed, electrical power, generator or rotor speed, wind direction and nacelle position, blade pitch angle, and ambient temperature or air density should be available. At a minimum, the average, minimum and maximum values should be provided.
10. What are the approximate costs for lifetime extension with LiTEplus?
The total cost of a LiTEplus lifetime extension report is approximately three times that of a conventional report. However, as with a conventional report, it should be noted that there are economies of scale when looking at multiple plants, so the cost per plant can be significantly lower than when looking at a single plant. Of course, costs also depend on the type of plant and location. Depending on the additional lifetime extension that can be achieved, the additional costs are therefore in the low single-digit percentage range of the additional yield.
11. Can the foundation also be monitored?
The foundation is, of course, one of the load-bearing components evaluated in the analytical calculation. For certain types of plants, foundation monitoring may be required for continued operation due to cracks in the foundation. Foundation monitoring is not a standard feature of LiTEplus, but a project-specific option can be implemented for the integration of foundation monitoring, as the corresponding hardware for data acquisition is already available in the system with LiTEplus.
12. Will the Cantilever Sensor also be installed in the rotor blades?
Cantilever sensors (CLS) were designed for load measurement in rotor blades and are used, for example, for load control and structural monitoring. However, for the optimized continuous operation test with LiTEplus, CLS are only installed in the tower. Installation in the rotor blade is not required.
13. Will LiTEplus be installed independently of system type or do the number of sensors or measured variables differ depending on the system?
The measurement system is standardized and can be used for all turbines with tubular steel towers up to 100 m hub height. For higher hub heights and other tower designs, e.g. concrete hybrid towers, the system may need to be extended to include additional measurement points - such requirements will of course be agreed in advance.