The growth of the renewable energy sector in the Republic may have to be constrained, the Minister for Communications, Mr Dempsey, warned yesterday.

Opening the offices of wind energy company Airtricity, the Minister said he was a big supporter of renewables but he wondered how much the electricity system could take.

He said he wanted to reach a target of over 13 per cent of energy consumption from renewable sources by 2010, but it presented major challenges.

"I fully recognise that the target is now stretching us on a number of fronts and I recognise that there are potential constraints to the pace of further development of the renewables sector. It is essential that we work together to meet these goals," he said.

Mr Dempsey's comments echo those of ESB National Grid, which operates the electricity transmission system. It has previously warned that introducing a large amount of renewable energy onto the system would require a large number of conventional plants as back-up.

"As you are aware the development of our alternative and renewable energy sources as a means of electricity production is an essential part of the Government's overall energy policy," he said.

He said these developments had not raised any technical issues for the system in the last few years, but this might be changing. "Planning for future programmes at increased penetration levels does raise significant technical issues which must be addressed in order to maintain system security for electricity customers."

He said a renewable energy development group had been established by his Department and it would look into these matters. "The group will advise on future options on policies, targets, programmes and support measures to develop the increased use of renewable energy in the electricity market to 2010 and beyond.

"I understand from my officials that Airtricity and the renewables industry in general have been most helpful in taking a full and active part in this process," he said.

Airtricity said it was developing projects at 16 sites in the US. The 16 sites would produce 1,400 megawatts of power, said chief executive Mr Eddie O'Connor. He said he welcomed the Minister's recent appointment and looked forward to working with him.

He went on to say that Ireland was over-dependent on gas and oil and was currently generating 58 per cent of electricity from these sources.

"Ireland is at the end of a very long gas pipeline. Interruption of this gas supply would have a major impact on the Irish economy," he said.

"Developing our greatest natural resource - wind energy - will reduce our dependence on gas and stabilise our fuel prices in the future."