Currently, over 90% of the lubricants used in Europe today are not biodegradable and are mainly based on mineral oil (non-renewable raw materials). In recent years interest has grown for biodegradable and non-toxic lubricants, initially developed for applications with total loss or risk of leakage, in order to avoid the polluting effects on rivers, lakes and aquifers. In parallel, the concept also has increased of renewability applied to lubricants, hence the increased interest in the production of lubricants from vegetable esters.
The biolubricants based on renewable resources offer great potential for rural economic development. Since vegetable oils are abundant in Spain, farmers could benefit from increased demand for their products. The use of biodegradable lubricants allows us to follow much more sustainable and environmentally friendly work systems, moreover avoiding the disastrous consequences in the case of accidental spillages.
Biolubricants can reach a technical performance similar to mineral-based lubricants in many applications, even thought here are some limitations related mainly extreme temperatures. They also have the additional advantage that they are readily biodegradable (they decompose) and lack toxic components, both for the environment and for humans.
Verkol, S.A. and Sotavento Galicia, S.A. have been working in the field of biodegradable, non-toxic and renewable lubricants within BIOVESIN project (Project 420000-2008-004PSE) co-financed with FEDER funds through the Ministry of Science and Innovation. Currently, after finishing the project, we are at the testing and demonstration phase of the operation where field tests being developed at the Sotavento Experimental Wind Farm with an oil for gearboxes and a grease for slewing rings.
It is intended to lubricate all the elements of a wind turbine from renewable, non-toxic and biodegradable lubricants to bring the clean energy concept to its logical conclusion in the generation (wind energy) and equipment maintenance (“green” lubricants).
This work was done on the choice of plant and synthetic fluids which meet the eco-toxic requirements of technical performance and in the selection of additives that improve the performance of the lubricant bases being used, in turn conforming with the requirements of Ecolabel, the European benchmark specifying the requirements for different products including lubricants, to identify them as environmentally friendly.
This project has proposed the use of vegetable oils for the production of lubricating fluids in wind turbines, where the renewable source thereof together with its biodegradability and non-toxicity, can add value in the concept of clean energy.
TECHNOLOGY FOR BIOLUBRICANT DEVELOPMENT:
The bio lubricants that are wanted to develop in this project are:
- Gear oil for the gearbox
- Grease for the lubrication of the slewing ring
The technical characteristics of the products to be developed are fixed by the application, for the specific requirements of the sector and environmental requirements, collected in the European benchmark Ecolabel.
1. Systematic Design
VERKOL, S.A. has established a process of design and development of lubricants sequenced in the following steps:
- Defining characteristics
- Preparation of prototypes
- Characterization trials
- Laboratory accelerated trials
- Tests on trial banks
- Field Tests
Step 1 defines the product features to develop and creates the Design Specification Product (DSP).
Steps 3 and 4 verify the product design developed by checking the results of the design compared to the DSP.
Steps 5 and 6, validate the performance. At present, we are testing six selected products at this stage in our facilities at Sotavento Experimental Wind Farm.
2. Areas of Expertise
Biolubricant properties depend essentially on the type and viscosity of the base fluid, the additives and in the case of lubricating greases of the type and concentration of the thickener, and the manufacturing process.
The knowledge areas involved in the development of a biolubricant are:
- The rheology
- The physical-mechanical stability
- The chemical stability
- The tribology
- The biodegradability and toxicity
The biolubricants used in this project were based on high oleic sun flower oil (HOSO 83%).
3.1. Gear oil for gear boxes
The developing gear oil should have a viscosity of 320 mm2/s at 40°C.The 83% HOSO has a viscosity of about 40 mm2/s at 40°C.This involves the use of a thickener to allow us to increase the viscosity of the base fluid. Also employed are additives to meet the technical requirements (anti-oxidants, corrosion inhibitors, copper passivators, anti-wear, extreme pressure and anti-foam), in turn fulfilling Ecolabel demands for biodegradability and toxicity with the restrictions that this entails (limitations on the type and dosage of additives).
3.2 Grease for the slewing ring
From the view point of grease lubrication, the slewing ring of the wind turbine is characterised by:
- Having a low amplitude movement
- To be subjected to heavy loads
- To have upright tooth flanks
- Having a tendency to high corrosion
The necessary components have been defined for a fat with suitable properties for the application which also meets the requirements Ecolabel.
The result is a grade 2 grease with good adhesion to prevent it falling from the point of application, anticorrosive properties and an excellent result in trials when sprayed with water. Such a fat prototype is being tested now on the wind turbines at Sotavento Experimental Wind Farm.