Geothermal and solar pv are future energy sources, as both these renewables draw energy from natural heat sources i.e. the Earth and the Sun. While geothermal energy utilizes Earth’s heat for power generation and for direct applications, like space cooling and dehydration, solar energy captures the Sun’s energy and converts the energy to electricity through solar pv cells. The quartz required to manufacture solar cells that can generate 1 MWe weighs about 10 tons, and the manufacture of pv cells involves two important stages: metallurgical grade silicon (MGS) and electronic grade silicon (EGS). In the first stage an amount of 1756 × 10⁶ kg of CO₂ is released, and a similar amount of CO₂ is released during the conversion of EGS to ingots. The total CO₂ emissions during the lifecycle of a solar pv cell are about 3312 × 10⁶ kg. This is far higher than a geothermal energy source, which emits about 450 g/kWh. According to the International Energy Agency (IEA), under the sustainable development policy proposed for adoption to mitigate CO₂ emissions, nearly 54 × 10⁹ cells are required to meet the generation target of 14,139 TWh. Of solar pv and geothermal energy sources, geothermal energy is the best option under this policy scenario to mitigate CO₂ emissions and to control global temperatures. In addition to the emissions related to the manufacture of solar pv cells, solar panels and solar cell waste management are of great concern. Globally the generation of solar panel waste will be of the order of 78 million tons (Weckend et al. 2016). Countries involved in the manufacture of solar pv cells will emit considerable amounts of CO₂ from this source in addition to coal-based thermal power plants. Solar pv cells may not emit CO₂ during the generation of electricity, but during their life time emissions are considerable. Therefore, solar pv cannot be considered a zero-emission source.

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可再生能源产生的CO 2排放量：太阳能光伏，水热和EGS来源

地热和太阳能光伏是未来的能源，因为这两种可再生能源均从自然热能（即地球和太阳）中获取能量。地热能利用地球的热量来发电和直接应用，例如空间冷却和脱水，而太阳能则捕获太阳的能量，并通过太阳能光伏电池将其转化为电能。制造可产生1 MWe的太阳能电池所需的石英重约10吨，而PV电池的制造涉及两个重要阶段：冶金级硅（MGS）和电子级硅（EGS）。在第一阶段，释放出1756×10 ⁶  kg的CO ₂，在EGS转化为铸锭的过程中释放出相似量的CO ₂。总CO太阳能光伏电池生命周期中的₂排放量约为3312×10 ⁶ 公斤。这远远高于地热能源，后者的排放量约为450 g / kWh。根据国际能源机构（IEA）的建议，在为减少CO ₂排放而采用的可持续发展政策下，需要近54×10 ^9个电池才能达到14,139 TWh的发电目标。在太阳能光伏和地热能源中，在此政策方案下，地热能是缓解CO ₂的最佳选择排放并控制全球温度。除了与太阳能光伏电池制造相关的排放外，太阳能电池板和太阳能电池废物管理也受到极大关注。在全球范围内，太阳能电池板废物的产生量将约为7800万吨（Weckend等，2016）。参与太阳能光伏电池制造的国家除了以煤为燃料的热电厂外，还将从该来源排放大量的CO ₂。太阳能光伏电池在发电过程中可能不会释放出CO ₂，但在其生命周期中的排放却相当可观。因此，太阳能光伏不能视为零排放源。