Sustainability of the Wind Turbine Blade Manufacturing Process: A Bio-Based Alternative

Abstract

Content : Globally, more than 23,000 wind turbines were manufactured in 2011 and there were 225,000 operational wind turbines by the end of 2012. United States' installed wind capacity will need to increase from 11.6GW to 300 GW to achieve the 20% wind production goal by 2030. To meet the increasing demand, not only more blades are being manufactured, but also longer blades of up to 100 meters long are being produced. The current stock of blades and the manufacturing process use petroleum based thermoset composites as the primary materials. The anticipated influx in disposal and manufacturing leads to health and environmental concern, given that the industry does not manufacture blades in a sustainable manner and has no practical way to recycle these blades. The main objective of this research project is to create an energy pathway for the sustainability of wind energy. In particular, this research is trying to develop a bio-based epoxy system for the wind turbine blade manufacturing process, in which the toughness, stiffness, durability and costs are comparable with petroleum based epoxy systems. The bio-derived thermoset will allow the industry to substitute a fossil fuel for vegetable oil, a more readily available feedstock, in the blade manufacturing process. In addition to the bio-based system, we want to realize the property of reworkability in both conventional and bio-based epoxies. The property of reworkability means that we could be able to thermally reprocess any anhydride-cured epoxy system with the addition of a special catalyst. It should allow for an effective recycling at the end of the blades' life cycle, presumably without the negative economic, health and environmental consequences that current disposal methods for thermoset composite impose. Overall, the expectation is to produce a high performance bio-based reworkable system which should enable manufacturing of blades that would be easily repaired, reworked or ground up for reuse with another purpose. The combination of these complementary technologies should improve sustainability both at the beginning and the end of the life cycle of a typical wind turbine blade. Approach to evaluation To evaluate the environmental, health and economic implications of replacing the petroleum based epoxy with a bio based epoxy, we use two different methodologies. The first one is a Life Cycle Cost Analysis (LCCA) to compare conventional and bio-based manufactured blades. The aim of the LCCA is to compare different alternatives in the manufacturing process and determine which one is the least costly while maintaining the same performance. We expect the bio-based manufacturing process to be very similar in terms of blade performance, but to differ in terms of the cost over the life cycle of the blades. The present value of all recurring costs and residual value of the blade at the moment of being disposed are calculated in order to determine the best long term manufacturing process.