Fossil fuels still account for the vast majority of the world’s energy consumption, but the search for pollution-free, sustainable alternatives is stepping up considerably. In the transport sector, where environmental pressures are high, a number of alternatives to petrol and diesel are in development and testing. One of these is solar power, and numerous projects demonstrating the potential of solar powered vehicles are underway.
In addition to solar powered cars, planes and boats are now also getting in on the act. These craft rely on composites to achieve the lightweight, high strength construction necessary to reduce power useage and to take into account the extra weight of the solar technology and batteries on board.
This July, the Solar Impulse aircraft completed its first night flight, powered only by solar energy stored during the day. As the first solar aircraft able to fly day and night, the next challenge for Solar Impulse is to fly around the world without using any fuel or producing any pollution.
Solar Impulse has a wingspan of 64 m and is powered by 12 000 solar cells. The aircraft is constructed around a skeleton of carbon fibre/honeycomb composites in a sandwich assembly. The upper wing surface is covered with a skin of encapsulated solar cells and the underside with lightweight flexible film. Between these two surfaces, 120 carbon fibre ribs at 50 cm intervals profile these two layers and give the wing its aerodynamic shape.
The PlanetSolar solar powered catamaran plans a similar around-the-world journey next year. This 31 m long, 15 m wide craft is fitted with more than 500 m2 of solar modules and uses lithium-ion batteries, which weigh around 11 tonnes in total, to store the solar power. Lightweight carbon fibre composite construction was used throughout the boat to minimise consumption of energy as the craft travels along.
While these solar projects are a long way from commercialisation, they serve to highlight the potential of composites in these challenging applications.