We rely on coal, oil and fossil fuels for over 80 percent of our current (1) 能源消耗 (B4U7) -a situation which shows little sign of changing over quite a long period of time. On top of this (2) 能源需求 (B4U7A) is expected to see a (3) 直线增长 (B4U7A) by almost half over the next two decades. Undoubtedly, this will be causing an (4) 能源危机 (B4U7A) and the fear that our (5) 看似充足 (B4U7A) energy resources are starting to run out. Energy shortages will (6) 严重打击 (B4U7B) the global economy and global quality of life. The potential for (7) 大规模短缺 (B4U7B) is very real if we run out of energy. However, it is still possible to find (8) 可行的替代品 (B4U7A). Scientists have recently turned their attention to natural sources of (9) 可再生能源 (B4U7A): the sun, the sea, the wind and hot springs. They are (10) 对环境有利 (B4U7A) but some of them have (11) 成本太高的缺陷 (B4U7A) to be a workable alternative to non-renewable energy. Ultimately, (12) 无限供应 (B4U7A) of renewable energy sources should ensure that the world does not fall short of its energy needs.