HOUSTON - The emergence of renewable energy is a positive global trend but more time is needed to develop technology and management in this field, secretary general of the International Energy Forum (IEF) Sun Xiansheng said Tuesday.

"Personally, I believe renewable and clean energy is a positive trend in the future. The only question is how fast it will grow. If all the countries work together and make more efforts, the day may come quicker," Sun told Xinhua at CERAWeek held here by the London-based information company IHS Markit.

Sun said that in the past two to three years, the cost of renewable energy has decreased significantly thanks to technological development. However, there remain huge cost challenges in this field. So, more time is needed for further improvements.

He also pointed out that in the foreseeable future, fossil fuel will still be the major source of energy worldwide.

"According to the outlooks of different energy organizations such as the International Energy Agency (IEA) and the Organization of Petroleum Exporting Countries (OPEC), fossil fuel will still account for about 57 to 79 percent of source of energy globally in 2040," said Sun.

The 72-member IEF is the neutral facilitator of informal, open, informed and continuing global energy dialogue. Accounting for around 90 percent of global supply and demand for oil and gas, it aims to foster greater mutual understanding and awareness of common energy interests among its members.

CERAWeek, which kicked off on Monday, is an annual energy meeting featuring prominent speakers from the energy, technology and finance sectors. More than 3,000 guests from over 50 countries and regions attended the meeting this year.