There’s heated debate on how green renewable energies really are. Depending on the source of information that you choose, renewables can be depicted from world-savers to wolves- dressed-as-a-sheep.
Wind farms can be also known as bird-and-bats-killers that generate devastation in Inner Mongolia where the rare-earth metals required for their turbine magnets are mined; Hydroelectricity can turn into a concrete monster, that alters river flows, destroys fluvial ecosystems and creates an important source of methane; not to mention Biomass, which can be another word for deforestation. And even solar is no exception to the controversy as many claim that the solar panels that now ornament European and American rooftops have left behind a legacy of toxic pollution in Chinese villages and farmlands. Amongst all the criticism, how can one make an educated choice on which energy source to support? Are all these renewable energies, in particular Solar Photovoltaics (PV), truly better for the environment than simply burning fossil fuels?
I gave myself the task of answering this last question excluding, to the extent possible, any information bias. This meant disregarding in my research any newspaper articles, ecologist magazines, opinion reports, and even Google. I stuck to scientific papers to try to get an educated yet simple answer. And what did I find?
My first finding is that to date, no energy source is 100% green. Even if a given energy production method is virtually emission free (as it is for solar PV), there is always a point in the lifecycle, upstream or downstream, where an impact from emissions can be measured. Therefore, the key to address this question is to assess how better off are we if we decide to use energy from a PV system vs. relying on other energy sources. There are a few methodologies to do this comparison, I selected three that I will be exposing here in three parts:
- Part I – Carbon footprint: the sum of the CO2 emissions during the lifecycle of an energy source, from the extraction of raw materials (cradle) to its disposal (grave) or recycling (cradle)
- Part II – Energy payback time (EPBT): the time it takes for the system to generate the same amount of energy it took to be produced, transported, installed and recycled
- Part III – End-of-life management (EOLM), i.e. how to dispose or recycle the components of the system once it’s obsolete ensuring minimal harm to the environment
Part I – Carbon footprint
When measuring the Carbon footprint of a PV system, it is important to take the direct and indirect impacts throughout the entire product lifecycle, from material sourcing, through manufacturing, transportation, construction, operation, dismantling and recycling. This is often expressed in terms of the amount CO2, and its equivalent of other GHG’s, emitted during the PV system lifetime divided by the number of kilowatt-hour (kWh) produced.
As far as CO2 emissions are concerned, while PV systems have no direct CO2 emissions into air during operation, their indirect emissions are mainly linked to the energy required for both its manufacturing and recycling processes. Most of the emissions (~60%) originate from the production of module itself, ~30% by its auxiliary components and another ~10% from the recycling process.
On another hand, the amount of electricity produced will depend on the lifetime and the conversion efficiency of the PV system, the system design and its orientation, in addition to the solar irradiation where the relevant system is installed. In gross, it can range from approx. 800 kWh/m² in Northern Germany to up to 2500 kWh/m² in the “Sunbelt area” (i.e. North Africa, South of the USA, the Middle-East, Australia).
So how better is the Carbon Footprint of a PV vs. that of a fossil-fueled plant? The carbon footprint of PV systems – assuming a location in southern Europe – ranges from 16 to 32 gCO2 eq. per kWh compared to between 300 and 1000 g CO2 eq. per kWh when produced from fossil fuels. In another words, a solar system generates 3 to 5% of the emissions of a coal or gas plant, which is definitely not perfect but also not negligible as a saving. The low carbon footprint of a PV system is only beaten by hydroelectricity, and to be fair we are talking of two technologies that are 200 years apart in terms of maturity. It’s quite amazing to see that the carbon footprint of PV has decreased by approximately 50% in the last 10 years thanks to performance improvements, raw material savings and manufacturing process improvements. So the race is not yet lost for Solar PV fellows!
(to be continued)
Kemp, K.K., Almakhlooq, R. (2016). Photovoltaic: Life Cycle Analysis and End of Life Management for Materials Reuse and Waste Recycling
Alsema, E.A., de Wild-Scholten, M.J., Fthenakis, V.M. (2006) Environmental impacts of PV electricity generation – a critical comparisom of energy supply options
de Wild-Scholten, M.J. (2010). Life Cycle Assessment of Photovoltaics: from cradle to cradle