Power generator rental group Aggreko has announced that its new chief executive took up his position on Friday.Aggreko said Chris Weston, formerly the managing director of Centrica's international downstream business, had replaced interim chief executive Ken Hanna, who would return to his role as non-executive chairman.Aggreko said Weston would spend his first few months travelling around the company, meeting staff and other key stakeholders, to understand the business and its fundamentals.Weston said: "Aggreko is a fascinating business with a great product, fantastic culture and attractive markets and I look forward to working with the management team to develop the company further in the coming years."