Even a ‘green grid’ has a carbon cost

3 August 2020 by Rachel Rose
We can’t solar panel our way out of climate change: energy demand must fall as well. And especially in the winter, when less solar energy is available! This alone is reason to construct energy-efficient buildings that need little energy for heating, and retro-fit those already built.

NZ grid emissions, predicted to 2050

Source: BRANZ Grid electricity 2018 – 2050_MBIE Scenarios 2016 (module B6).xlsx

Our grid’s carbon emissions are expected to drop, but only from 0.180 kgCO2e/kWhr currently to 0.120 kgCO2e/kWhr in 2050. That’s when New Zealand is supposed to be at carbon zero. This highlights that even a renewable grid is responsible for carbon emissions during the manufacture of the components, plus ongoing emissions arising from operations.
This plot from BRANZ is the predicted kgCO2e/kWhr of electricity for the NZ power grid based on the MBIE Electricity demand and generation scenarios report from 2016. The Ministry for the Environment have a published greenhouse gas figure as part of their corporate GHG reporting. This figure is higher, because BRANZ has include pre-combustion emissions and infrastructure (the MfE figure is combustion emissions and geothermal fugitive emissions only).
That said, we need to work on all fronts and there is ongoing research into generating solar power much efficiently and with less emissions from manufacture. This article outlines some research into a new way of making solar panels that reduces the carbon footprint. It’s a further development of perovskite solar cell technology and isn’t widely commercially available yet.
These tandem cells are producing 0.011 kgCO2e/kWhr over their lifetime, at least in the lab. That compares to the current technology (crystalline silicon cells) which produces around 0.025 kgCO2e/kWhr. (Both these figures are just for the panel itself.) Crystalline silicon cells have an energy payback of 1.5 years versus just four months for the perovskite-perovskite tandem cells.
—Jason Quinn
3 August 2020

Comments 1

  1. Anonymous comment send via email.

    I’m not sure I agree with your analysis of PV. That’s a very selective reading. There are literally hundreds of studies of the LCA of Photovoltaics and the numbers vary widely according to the a) study methodology and b) where the PV is manufactured. However I think a more commonly accepted number is 0.05kg/kWh. I know Wikipedia isn’t always right but the numbers here back up lots of studies I have read:
    And these studies almost always exclude the back-up generation or energy storage needed to make a large uptake of PV work – the fact is PV relies on the grid so you can’t exclude emissions from central infrastructure when looking at the technology.
    I think large centralised wind is a better bet. It’s cheaper per kW, has lower lifecycle emissions, and is much less intermittent (it runs at night and during the winter).

    —JEQ I agree. The 0.05kgCO2e/kWhr would be a much more consensus number and lends even more weight to the point of this post. We need to conserve as well as renewable generation. As I said ‘We can’t solar panel our way out of climate change: energy demand must fall as well.’

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