Last month I had a tour to Wuyuan and Sanqing Mountain of Jiangxi province. In the hotel, I watched the news of Steven Chu, Minister of US DOE, visiting China. He was prompting his white roof plan on TV. Paint white the roof, and paint light color on the road and cars, large amount of solar radiation can be reflected back, thus the greenhouse effect can be reduced, power consuming of air conditioner can be saved. California has started to carry out this plan since 2005. His another promotion, carbon tariff, is strongly against by Chinese government, as well as India, Brazil, and most European countries. It is accused as trade protectionism in the name of environment protection as it destroys the consensus of Kyoto Protocol. But I think the white roof plan should be easily accepted worldwide, although the lawmaking may take time. For example, the traditional villages I visited in Wuyuan, all have black roof tiles and white wall. It is a local architectural style and looks amazingly comfortable. I don’t hope these tiles are also painted white.
In north China, e.g. Beijing, the air is very dry. Dust will soon turn the white roof to gray roof. In Daya Bay Experiment, we paint the inner wall of the antineutrino detector with black fluor-carbon paint, to reduce the stray light, and have studied to paint the outer wall with white fluor-carbon paint to collect more light in the water Cherenkov detector. Fluor-carbon paint is a cheap wall paint. It has excellent Weather Resistance and, as most fluor material, can be self-cleaned by rain.
In Xiaoqi village, there are several water mills in the brook. At Rainbow Bridge, there is a huge one, which drives machines of a grain handling workshop. Of course they are ornaments now. People like to use more convenient electricity. However, if we install electricity generator on these mills, the cost is quite low. In general, a small diesel generator of several to 30 kW costs 1000 Yuan/kW. Save the diesel engine, the cost is only several hundreds Yuan/kW. The investment can be got back in less than 3 months. China plans to invest 4.5 trillion Yuan on clean power in the next 10 years, such as wind power, nuclear power, and solar power, etc. And the allowance to solar electricity is 1 Yuan/kWh. Comparing to the large scale investment, small ones could be more economic and more environment-friendly. 4.5 trillion is 3500 Yuan/person in average. If every Chinese invest 1000 Yuan to generate 1 kW, the total capacity will be twice of current total capacity. Household clean power looks very encouraging.
前一阵去江西婺源和三清山旅游，在旅馆中看新闻，美国能源部长朱棣文访华，再次推销他的刷白屋顶计划：将屋顶漆成白色，路面和汽车使用浅色涂装，可以大量反射太阳辐射能量，降低温室效应。同时，也可以减少空调的能源消耗。美国加州已从2005年开始逐步实施该计划。他的另一项推销——碳关税，受到中国政府，以及印度、巴西和大部分欧洲国家的强烈反对，被指为借环保之名，行贸易保护之实，颠覆了京都议定书的基础。但我想刷白屋顶计划应该是比较容易在世界范围内达成一致的，不过立法可能需要时间。我们去的婺源的传统小村庄，一律都是青瓦白墙，赏心悦目，我可不希望把徽派建筑的青瓦也统统刷成白色。
在中国的北方，例如北京，空气干燥，灰尘很快会将白屋顶变成灰屋顶。在大亚湾实验中，我们在中微子探测器内壁喷涂了黑色的氟碳漆以降低杂散光，并曾考虑在外壁喷涂白色的氟碳漆以提高宇宙线探测器的光探测效率。氟碳漆是一种廉价的外墙涂料，具有很好的化学耐候性，也具有氟材料的普遍特点：表面不粘。在自然雨水的冲洗下就能自洁。
在婺源晓起村，有几架水车在溪流里转着，看上去古色古香。在彩虹桥，有一个大型的水车，用来驱动一个谷物加工作坊。当然，现在它们都是摆设。人们当然倾向于使用更方便的电。如果给这些水车装上小的发电机，成本其实非常低。一般几千瓦到30千瓦的小型柴油发电机价格为1000元/千瓦，去掉柴油机，成本只有几百元，不到3个月就能收回投资。中国计划在10年内投资4.5万亿元发展清洁能源，如风电、核电、太阳能。目前对太阳能发电的补贴是每度1元。除了规模投资，从小的方面着手更经济，更符合环保的理念。4.5万亿相当于人均3500元。可是如果全中国每人花1000元发电1kw，已经是现在全国装机容量的两倍。化整为零，大有可为。
