Use of composite materials in Renewables
The use of fibre-reinforced polymers (FRPs) in wind turbines is an important technical element. Components must exhibit excellent fatigue strength, resist random loading and corrosion, require minimal maintenance and serve for 30+ years. Uncertainties over the performance of initial experiments with steel and aluminium have been overcome with the use of composite members, on which production is now almost entirely based. The blades are the main components, predominantly manufactured from glass-fibre, and the performance of the turbine is ultimately dictated by their efficiency. The use of lighter weight FRP materials means that the turbines can produce more power per unit volume, minimising impact on the landscape.
To reduce the cost of energy from wind turbines to levels competitive with coal- and gas-fired electricity production, producers have raised tower heights to place turbines in stronger winds and lengthened blades to capture more wind. As this strategy reaches the upper limits of practicality, designers are now exploring the use of carbon-fibre as a means to further push the design envelope and decrease the cost of energy.
Compared to conventional all-glass-fibre designs, composites that replace some of the glass with carbon-fibre reinforcements can produce the same blade using less fibre and resin, while increasing blade stiffness, improving aerodynamics and decreasing the loads imposed by the blades on the tower and hub. A design that incorporates carbon fibre also can make power input from the blades more predictable.
Offshore wind farms are a relatively recent, high impact development. FRP materials will be instrumental in the success of offshore programmes due to their proven performance in corrosive and hostile environments, which will maintain efficiency of the structures under increased locational loads.
Due to their inherent properties FRP composites work well as marine turbine blades as they do not rust. Epoxy resin is less susceptible to water penetration and is generally, but not always, used as the matrix in an underwater composite. Excellent fatigue performance means that the turbine do not need to be constantly maintained.
As natural insulators with high dielectric strength, glass-fibre composites revolutionised the handling of electricity when they first replaced wood and metal in 1959. Today, utility companies are working with composite suppliers to take advantage of composites for both power transmission towers and distribution poles, cables, cross-arms - traditionally the province of wood and steel - and the aluminium conductor cables they support. Pultruded and filament-wound composite utility poles and cross-arms have begun to overcome buyer resistance as electric power companies employ them primarily as replacements for aging wood poles in remote and/or extremely humid locations. Composite-reinforced aluminium conductor cables (CRAC) replace traditional steel-strength members in cables with a pultruded continuous-fibre core, which is expected to reduce weight and to increase power-transmission efficiency by an estimated 200%. If successful in upcoming tests and demonstration projects, CRAC technologies may find application in infrastructure modernisation projects. CRAC cable developers claim that power needs will actually increase, by as much as 19 percent, in the next 10 years, making CRAC cabling an attractive alternative for upgrading powerlines on the existing grid, without erecting new towers or obtaining additional rights-of-way.
Composite materials are likely candidates for the eventual materials of choice used to make the bipolar plates, end plates, fuel tanks and other components in fuel cell systems. Fuel cell technologies of several types offer a "clean" (near-zero VOC) means to convert hydrogen to electrical power in automotive and stationary power systems. Due to their conductivity, corrosion resistance, dimensional stability and flame retardancy, vinyl-ester-based bulk moulding compounds (BMCs) with carbon-fibre reinforcement have already been selected in a least one commercially available stationary unit.