- Embodied carbon is the carbon footprint to make a product
- Solar photovoltaics (PV) can have a high embodied carbon footprint, particularly for crystalline PV
- Solar panels generate electricity to reduce carbon emissions each year, through avoided electricity generation from the national grid
- However, the UK is rapidly decarbonising its grid electricity
- The burning question is therefore, does solar PV still payback its embodied carbon footprint. If so after how many years?
- Or is solar now the elephant in the room?
- What does this mean for net zero carbon?
Embodied carbon is the carbon footprint to make a product. It arises throughout the supply chain and cuts across geographies. It therefore gives us a true picture of the carbon intensity to manufacture a product.
When it comes to Solar Photovoltaics (PV), it is well established that they can have a high embodied carbon footprint. However, this has traditionally been offset by the savings in electricity from the national grid.
Historically the carbon emissions of generating electricity have been high in the UK. In the not too distant past, gas and coal based power stations were the dominant technologies. Fast forward to today and it has rapidly changed. There has been a quick rise in electricity from renewables, particularly wind and biomass. This has transformed the carbon footprint from UK electricity.
In fact, the carbon emissions of a kWh of UK electricity have reduced by a whopping 45% in just 4 years, between 2015 and 2019. The carbon emissions are also continuing to reduce, or decarbonise as it is called. It is expected for electricity to make a significant contribution to the UK's aspiration to be net zero carbon.
The burning question is therefore, in the modern landscape does solar PV still payback the high embodied carbon footprint?
Or is solar PV now the elephant in the room?
With the rise of net zero carbon buildings, this is now a prominent question.
Embodied Carbon Payback Time of Monocrystalline Solar PV
We have estimated this for monocrystalline PV in the UK, which is one of the most popular photovoltaic technologies. The embodied carbon was compared against the annual savings in electricity generated. It was projected with grid decarbonisation rates from the National Grid’s Future Energy Scenarios (FES).
Due to the rapid rate of decarbonisation in the UK, the system install date is surprisingly important.
According to the International Energy Agency (IEA), the average expected output from a solar PV system in urban areas of the UK is 920 kWh / kWp per year.
This has been used to give the embodied carbon payback results below:
Here are some insights for monocrystalline PV:
- The estimated embodied carbon payback for the system installed in 2020 is over 20 years
- This means it would be 2040 before the system has saved more carbon than its initial embodied carbon of production – well beyond a 2030 net zero carbon target
- Sometime in the year 2023, that same system would not be carbon positive until around 2050, bringing targets for net zero carbon by 2050 now into question
- A system installed in 2025 has an estimated embodied carbon payback of 30 years – which is roughly the lifetime a PV system
- Beyond an install date of 2025 the embodied carbon may not payback at all, for many systems
Discussion - Implications for Solar PV and Net Zero Carbon
It also presents a strong case study for considering embodied carbon through whole life carbon assessments as part of net zero carbon. Net zero should really mean net zero, no matter where in the world the (supply chain) emissions arise.
In the context of the UK, it is clear that the embodied carbon of solar PV is now an important parameter. At the same time, as the electricity from the UK national grid becomes cleaner the embodied carbon of photovoltaics will only become even more prominent.
How About Wind Turbines?
In short, no they don’t. The embodied carbon of a large wind turbine, such as used on a wind farm, can be expected to payback in around 1 year. Over such a short timescale grid decarbonisation is not a factor.
To raise another important question, aren’t renewables part of the UK’s national grid mix anyway? Which gives rise to the decarbonising electricity grid.
Well yes, they are - but solar PV is not a particularly large contributor on a national scale. Between 2015 and 2019 the UK reduced the carbon intensity of electricity by 45% per kWh. This was predominantly driven by wind and biomass, combined with a reduction in reliance on coal. Solar PV had a smaller part to play in that decarbonisation.
What Next for Solar PV?
According to the IEA (2015) a cadmium-telluride, CdTe, based PV system would have an embodied carbon 60% lower than a monocrystalline PV system for each kWp.
For whatever reasons, CdTe based PV haven’t really taken off in the UK, but perhaps it’s time to investigate the feasibility of other types of solar PV. As a side note, the element cadmium is known to be highly toxic. There are studies that show cadmium-telluride is less toxic than the cadmium in isolation. PV laminates are also encapsulated. That said, it offers a good example of why true sustainability is difficult to achieve and requires trade-offs to balance one issue with another.
It would be expected that some manufacturers produce lower embodied carbon monocrystalline PV panels. The embodied carbon of any product varies between different producers. However, there is a chronic lack of embodied carbon data from the producers themselves. Considering the size of the solar sector around the world, we would have expected to find some Environmental Product Declarations, such as EN 15804, or detailed life cycle assessments (LCA). Until manufacturers produce detailed embodied carbon footprints of their products, procuring a lower embodied carbon crystalline PV panels becomes a challenge.
It leaves some burning questions, will other types of PV take over, or will crystalline PV clean up its act? Who knows, for now we know that the embodied carbon of PV needs to be taken seriously and warrants further research. This should be taken to avoid serious carbon leakage, especially in the context of net zero carbon.
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