Gas Expanded Lubricants: Smart Fluids for Improving Efficiency of Wind Turbines

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

0967915 Clarens The goal of this research is to develop the fundamental knowledge base needed to deliver gas-expanded lubricants (GELs) for improved efficiency in gears and bearings of next-generation wind turbines. GELs are binary mixtures of synthetic lubricants and dissolved liquid carbon dioxide maintained at moderate pressure. The properties of these lubricating fluids can be dynamically adjusted by controlling mixture composition, and consequently can help reduce operating inefficiencies for wind turbines that are subject to dynamically changing loads. Reliable and adaptive lubricant systems are necessary for turbines to be made larger or to be installed in inaccessible or offshore sites. The proposed research proposed will build the foundation of chemical understanding that is necessary to select proper components and process operating conditions needed for optimal performance and minimum environmental impact. Preliminary modeling results suggest that GELs could reduce power losses in a fluid film bearing by over 20%. Intellectual Merit This study will measure the mechanical and thermal characteristics of GELs under relevant conditions and evaluate their behavior in a modified rotor test bed. The proposed study is broken down into five tasks: 1) Study the high pressure phase behavior of lubricants and carbon dioxide; 2) Measure the rheology of GELs under relevant pressure and temperature conditions; 3) Evaluate the thermal characteristics of GELs relative to straight lubricants; 4) Develop an experimental testbed to measure bearing performance using GELs; 5) Create a life cycle model of GEL delivery to establish large-scale feasibility. This research is potentially transformative because it represents a completely new approach to wind turbine lubrication that has considerable promise to make significant improvements in increasing the energy efficiency for electric power generation from wind energy. The proposed research has the potential to advance fundamental understanding of the tribology of high-pressure liquid/gas mixtures, their phase behavior, and flow properties. Specifically, the research plan seeks to reveal the effect of two important lubricant parameters, viscosity and density, in predicting stiffness and shear forces in rotating machinery. An understanding of these relationships will be developed for a family of bio-based synthetic lubricant chemistries. The results will be validated experimentally using a specially modified test rig that mimics the nonlinear loadings typical of real wind turbines. This new understanding will be summarized in a set of design guidelines and tools which can be easily used by the wind industry. The results of this work will have clear implications for wind turbine manufacturers and supporting industries trying to improve turbine life and reduce the generation cost of wind electricity. Broader Impacts The education activities will contribute to a larger effort to develop a green energy education programs in the state of Virginia. The recent boom in manufacturing and service sectors associated with sustainable technologies such as wind energy suggests that training programs must be implemented to provide skills for people hoping to work in these areas. The PIs have partnered with Southwest Virginia Higher Education Center to provide a course in wind turbine fundamentals and maintenance to augment existing curricula for both university and community college students. Research outcomes will be transferred to industry via the Rotating Machinery and Controls (ROMAC) university-industry cooperative program at the University of Virginia (UVa) and its forty industrial partners, including GE, Rolls Royce Energy, and Praxair.