It's something we all do dozens of times a day without thinking, yet opening and closing doors can generate electricity - and four Hong Kong students have invented a device to capture this energy. Electdoor - the creation of Ho Wai-tat, 18, of Chan Sui Ki (La Salle) College, and his team members - stores the energy and converts it to power electrical devices, such as doorbells. 'The idea is to create a new form of renewable energy, while reducing the amount of resources wasted,' Wai-tat said yesterday. The teenager and his colleagues - Lau Sui-lun, 19, Yiu Kwun-chuen, 17, and Man Chun-wai, 17 - have won a prize for their creation at the Joint School Science Exhibition. The exhibits are on display at the Central Library in Causeway Bay until Thursday. 'One may argue that the energy produced by our device might be insignificant, but the fact is, the energy produced is considerable as we open and close doors many times a day,' Wai-tat said. Sui-lun added: 'We can gather the energy produced each time and it becomes a big sum.' The team cited research showing the mainland consumed up to 8 billion batteries a year and discarded so many, it was causing serious pollution. They estimated that everyone opened a door 20 times each day. With 7 million people in the city, the Electdoor could save 364,000 batteries a year. Speaking at the opening ceremony yesterday, Environment Secretary Edward Yau Tang-wah said the invention by the young scientists 'vividly shows how together, we can draw ever-growing benefits from science, including the enhancement of our environment'. He said he would invite the Electrical and Mechanical Services Department to examine the product and see if it could be applied to government departments. 'Certainly we still have room to improve our energy efficiency target,' Mr Yau said. Chief Executive Donald Tsang Yam-kuen revealed in March last year that two blocks of government buildings were undergoing an audit and that an energy saving target of 1.5 per cent had been set. Last October, the European Union passed a law to involve people in helping to cut the EU's energy consumption by 20 per cent by 2020.