The solar balloon is designed to trap solar energy using an inflatable plastic thin-film balloon called a solar concentrator. Half the balloon is transparent. When inflated, sunlight falls on it and focuses on a photovoltaic cell placed at its centre. This design reflects sunlight, producing 400 times the electricity that a solar cell would create without the concentrator and has been created by a company called Cool Earth. The film is abundant and cheap and does away with large expensive solar panels or costly concentrating mirrors. It can trap 500 watt to 1 kilowatt of solar energy.