How Much CO2e per kWh?
After 16 months, our solar plant has generated 18 000 kWh of electricity. I expect the savings to be more than €3 000 for 2022.
As I'm obsessed with global heating and avoiding CO2e emissions, I'm interested in how much CO2e we have avoided. Let's dig into the numbers:
According to Sungrow - 1 kg CO2e per kWh
The Inverter producer (Sungrow) compares the electricity generation with coal-burning electricity. Combining 1 kg Coal gives ~3.7 kg carbon dioxide and gives up to 9 kWh. If the thermic energy is converted to electricity with 33% efficiency, one kWh will generate 1.2 kg CO2e.
That would cancel the emissions from my entire family's personal consumption, if that number would reflect our savings. But it doesn't.
Averaging to the Swedish Electricity Mix ~13 g CO2e per kWh
Luckily, the electricity production in Sweden is almost coal-free. Most of the electricity is generated from wind and water, and also extracted from nuclear nucular power. What is the CO2e cost from that?
With the Swedish power mix, we have some 20 g CO2e per kWh. That is less than half of the 41 g CO2e per kWh that comes from residential PV facilities. Does this mean that I INCREASED greenhouse gas emissions in Sweden by installing solar cells? Probably not.
Margin Production to the Swedish Electricity Mix ~ 200 up to 300 g CO2e per kWh
It is more relevant to measure how our contribution to the supply/demand will affect the emissions from the power grid, and to understand that, we need to look at the margin production and also the pricing mechanisms of electricity in Sweden (here, I need to underline that this blog reflects my learning curve in this subject. I have a M Sc degree in Physics and I do understand the basics of energy flows, but I'm not an expert on price models).
The Electricity Market
The price for electricity is based on a market that is organized by Nord Pool and Nasdaq, where producers and "customers" place orders for electricity (amount of electricity they want to sell and buy at different price levels). The price level where the supply meets the demand will be the spot price for that particular hour and area. If you can provide electricity with a lower margin cost than the spot price - congratulations!
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| This is the energy mix on a windy day. The higher the bars are, the costlier they are for the supplier. The wider they are, the more power they provide. The price and volume is set where the demand curve (black) meets one of the bars. In this case, no fossil company will deliver electricity - the price is too low. The white area above wind, solar and hydro are earnings. |
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| This is the energy mix when the wind isn't blowing. The demand is as above. Now, the price is so high that it makes sense to activate oil plants. Even a tiny increase of the demand will increase the supply with a corresponding unit of oil and Greenhouse gas emissions. The earnings from renewables are very high in this case. |
These graph show that sources such as wind and solar will generate electricity regardless of the spot price. The best I can do as is to keep my solar cells up and running as much as possible.
For hydro, it is possible to adjust the output, for example if the water levels are getting too low.
For nuclear, the margin cost is low, and it is possible (but a bit tricky) to reduce the output.
For fossil fuels, it is easy to control the output.
The margin production will generally be fossil fuels, either in Sweden or in the countries Sweden trade with.
Even if the overall CO2e emissions are low for electricity generation in Sweden, the margin emissions (the extra emissions from one extra kWh) can be high.
Tidsstegen
The Swedish Environmental Institute has introduced a model for estimating the climate impact of electricity and one of their reports came in May this year. The method "Tidsstegen" will analyze how a marginal change in electricity consumption will affect the emissions in the European power grid, for different scenarios and different years (2020, 2025, 2030, 2035 and 2040).
The four scenarios spans from "low ambitions/Very Conservative", "Conservative", "Climate Neutral Nordics" to "Ambitious Europe", where the latter scenario represents very high ambitions.
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| The rows: Price for CO2e, Attitude to Solar/Wind, Demand for electrofuels Whether Nordic grids will be climate neutral in 2050 |
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| The red bars represents "Climate neutral Nordics". Interpolating between 2020 and 2025 gives roughly 500 g CO2e per kWh in 2022, falling quickly until 2025. |
I'll use that figure for estimating the consequenses of my electricity production and consumption.
Further reading:
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