As the demand for wind energy continues to grow at exponential rates, reducing operation and maintenance (OM) costs and improving reliability have become top priorities in wind turbine (WT) maintenance strategies. In addition to the development of more highly evolved WT designs intended to improve availability, the application of reliable and cost-effective condition-monitoring (CM) techniques offers an efficient approach to achieve this goal. This paper provides a general review and classification of wind turbine condition monitoring (WTCM) methods and techniques with a focus on trends and future challenges. After highlighting the relevant CM, diagnosis, and maintenance analysis, this work outlines the relationship between these concepts and related theories, and examines new trends and future challenges in the WTCM industry. Interesting insights from this research are used to point out strengths and weaknesses in today’s WTCM industry and define research priorities needed for the industry to meet the challenges in wind industry technological evolution and market growth.

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Wind Turbine Condition Monitoring: State-of-the-Art Review, New Trends, and Future Challenges

In the last two decades, a significant number of innovative sensing systems based on optical fiber sensors have been exploited in the engineering community due to their inherent distinctive advantages such as small size, light weight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability. A lot of optical fiber sensor-based monitoring systems have been developed for continuous measurement and real-time assessment of diversified engineering structures such as bridges, buildings, tunnels, pipelines, wind turbines, railway infrastructure, and geotechnical structures. The purpose of this review article is devoted to presenting a summary of the basic principles of various optical fiber sensors, innovation in sensing and computational methodologies, development of novel optical fiber sensors, and the practical application status of the optical fiber sensing technology in structural health monitoring (SHM) of civil infrastructure.

https://downloads.hindawi.com/journals/tswj/2014/652329.pdf

Structural health monitoring of civil infrastructure using optical fiber sensing technology: a comprehensive review.

Carbon fiber cement paste piezoresistive sensors (CFCPS) are made of piezoresistivity of carbon fiber cement paste and mainly used for local monitoring of concrete structures. Two electrode fixing styles for measuring the resistance of CFCPS are compared and the conception of embedded gauze electrode is put forward. The characteristics, layout styles and configuration parameters of embedded gauze electrode and the methods for measuring the resistance of CFCPS are studied. The mould of sensors is designed and the data acquisition system based on voltage signal is developed. It is revealed that the four-pole layout is suitable for setting embedded gauze electrode and the direct-current four-pole method adapts to measure the resistance of CFCPS. The resistivity of CFCPS is independent of the area of voltage pole and the mesh size of gauze electrode. The space between current pole and voltage pole does not influence the resistivity of CFCPS when more than a critical value. The developed data acquisition system has many advantages such as simple circuit, good practicability, high precision and ability to realize real-time, on-line and multi-channel acquisition.

Electrode design, measuring method and data acquisition system of carbon fiber cement paste piezoresistive sensors

A review on five key sensors for monitoring of concrete structures

Progress in triboluminescence-based smart optical sensor system

The overall deterioration of the national civil infrastructure due to aging and usage beyond the anticipated loads and lifetimes for which it was designed, combined with the increasing cost of maintenance and repair, has resulted in the need for improved techniques for non-destructive evaluation of the structural health of reinforced concrete. A recent review of the available statistics reveals that almost 40% of United States bridges are ‘structurally deficient’ or ‘functionally obsolete’ [1]. New reinforced concrete constructions would also benefit from in situ structural monitors which could detect a decrease in performance or imminent failure, thereby optimizing lifetimes without compromising safety. Finally, although modeling the behavior of some structures made from well-characterized materials is fairly accurate, the use of new materials, unusually complex designs, or variability in strength-related factors such as void fraction or moisture content can lead to unexpected structural weakening, damage or failure. The inadequacy of the nation’s highways, bridges, etc. prompted the initiation in 1993 of a National Science Foundation program, with the goal of developing new technologies aimed at ‘prolonging the life and enhancing the capacity of our existing and future civil infrastructure systems’ [2]. In response to the increased need, various techniques are being developed, and some of the most promising are based on the use of fiber optic sensors (FOS).

https://iopscience.iop.org/article/10.1088/0964-1726/5/2/008/pdf

Fiber optic sensors in concrete structures: a review

Dose gradients in large mirror substrates due to unequal exposure to the natural space radiation environment have been calculated for two circular orbits: 1200 km altitude/98 deg inclination and 3700 km/30 deg. Dose gradients were translated to density-change profiles based on experimentally determined density changes as a function of dose for fused silica and the low-CTE glass ceramic, Zerodur-M. Finite element analysis of deformation due to the radiation-induced density gradient was performed for a 4 meter by 0.5 cm disk representing a mirror faceplate. Displacements of nearly 2500 micrometers at the outer edge were calculated for a Zerodur faceplate after 10 yr at 3700 km/30 deg. Silica, which is much less sensitive, deformed by only a few angstroms. Reinforcement with a backing having the equivalent stiffness of 5 cm of SiC resulted in a 10-fold decrease in the calculated deformation.

E. J. Friebele

Papers

Fiber optic sensors in concrete structures: a review

Finite element analysis of deformation in large optics due to space environment radiation