![]() ![]() For lifetime expectancy, they choose 30 years. For solar insolation, the researchers choose 1,700 kWh per m² per year, which is the average of sunlight in Southern Europe. However, these conclusions are dependent on some assumptions, most importantly solar insolation (the amount of sunlight that the cells receive) and lifetime expectancy. All other types and scenarios fit between these two extremes. In spite of their high efficiency, mono-crystalline silicon cells score worst, with 43 grams of CO2 in the EU, and 55 gram of CO2-equivalent in the US. ![]() ![]() In spite of their lower efficiency, they are more eco-friendly because they need less material and no aluminium frame. Thin film solar cells get the best score with 20.5 grams of CO2 in the European energy mix and 25 grams of CO2 in the American energy mix. They do that for every type of cell and for the three different scenarios. The scientists come up with figures concerning the amount of greenhouses gasses emitted per kilowatt-hour of electricity delivered by one square meter of solar cells. "The optimistic conclusions of the researchers are based on a life expectancy of 30 years and solar insolation in the Mediterranean" The researchers investigated 4 types of solar cells: multi-crystalline silicon (with an efficiency of 13%), mono-crystalline silicon (14%), ribbon silicon (11.5%), and thin-film cadmium telluride (9%). Since they use comparatively more gas and hydropower, this is the best case scenario. A third scenario uses the figures of the recent “CrystalClear” European Commission project, which investigated the real energy mix used by 11 European and American silicon and PV module manufacturing factories. One is based on the average European energy mix, another on the average American energy mix (which is about 45% more CO2-intensive) (Note: in this article, “CO2” stands for CO2-equivalents which means other greenhouse gases are included ). Therefore, the researchers bring into account 3 scenarios. The ecological burden of energy use depends on the way electricity was generated. All these processes produce air pollution and heavy metal emissions, and they consume energy - which brings about more air pollution, heavy metal emissions and also greenhouse gases. Finally, these upgraded materials have to be manufactured into solar cells, and assembled into modules. Next, these materials have to be treated, following different steps (in the case of silicon cells these are purification, crystallization and wafering). First, raw materials have to be mined: quartz sand for silicon cells, metal ore for thin film cells. Similar to computer chips, this is a dirty and energy-intensive process. Solar panels don’t come falling out of the sky – they have to be manufactured. Some recalculations (skip this article if you get annoyed by numbers) produce striking conclusions. However, they interpret them in a rather optimistic way. The researchers come up with a solid set of figures. Good news, it seems, until one reads the report itself. Producing electricity from solar cells reduces air pollutants and greenhouse gases by about 90 percent in comparison to using conventional fossil fuel technologies, claims a study called " Emissions from Photovoltaic Life Cycles", to be published this month in “Environmental Science & Technology”. In some cases, producing electricity by solar panels releases more greenhouse gases than producing electricity by gas or even coal. New research shows, albeit unintentional, that generating electricity with solar panels can also be a very bad idea. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |