题目

You and Me is the theme song(主题歌) of the 2008 Beijing Summer Olympics. Liu Huan and Sarah Brightman sang the song in the Opening Ceremony(开幕式) of the 2008 Beijing Olympics. Sarah is a famous British singer. The song lasts four minutes and ten seconds. It is a very simple song, but it is also a great challenge(挑战) to me. The easiest is the most difficult,” said Liu Huan. “I couldn’t believe my eyes when I got the invitation to sing the song. It is a great honor(荣誉) for me and I am very lucky,”said Sarah Brightman. You and me is quite different from all the ot安阳市是我国重要的光伏基地之一，光伏发电是利用太阳能电池在太阳照射下发电。安阳市启动了“光伏工程”示范项目，在某中学的教学楼顶安装了总功率为20kW的光伏发电系统。 （1）若一天的有效光照时间按8h计算，该光伏发电系统一天共发电多少千瓦时？ （2）该光伏发电系统一天的发电量，如果由热电转换效率为30％的热电厂来完成，需要燃烧多少千克煤？（煤的热值q煤＝3.0×107J / kg ) （3）请写出一条光伏发电的优点。