Why 100% Renewables Does Not Mean Zero Carbon Emissions

Businesses, electrical vehicle charging services and electricity suppliers advertise 100% renewable electricity to demonstrate their environmental credentials. Providing more renewable electricity from solar, wind and hydro generators reduces overall carbon emissions from electricity. Using 100% renewable electricity still results in significant carbon emissions.  

Figure 1: Wind farm, Turlock, United States.

Renewable Energy

Renewable electricity sources provide varying amounts of electricity over time. Solar generators provide most power during long sunny summer days whilst wind provides most power when there are strong winds across the country and at sea. Hydroelectric generation depends on rainfall as well as snow melting. Nuclear power stations (no carbon but not renewable) have a near-constant power output that cannot be varied easily from hour to hour. The carbon-free power generated depends on the weather and the seasons and not the amount needed at a particular time.

Surpluses and Shortfalls

This mismatch between supply and demand means two things:

• Renewable (and nuclear) generators are switched off when there is surplus power generation
• Carbon intense generation (oil, gas and/or coal) is used to satisfy demand which cannot be met by renewables 

What does 100% Renewables mean?

It means that over a long time period (say a year) the amount of renewable electricity purchased matches the amount of electricity used.

What does Zero Carbon mean?

It means that all electricity consumed comes from renewables or nuclear generation.

How can Zero Carbon be achieved?

To achieve zero emissions electricity consumers need to ensure their energy consumption is matched to renewable energy generation on an hour by hour basis. This is not easily achievable in practice. https://carbonintensity.org.uk/ provides grid carbon intensity data to help consumers minimise carbon emissions from their electricity use.

Click here to find out more. 

About Pager Power

Pager Power undertakes technical assessments for developers of renewable energy projects and tall buildings. For more information about what we do, please get in touch.

Image accreditation: American Public Power Association (October 2017) on Unsplash.com. Last accessed on May 16th 2022. Available at: https://unsplash.com/photos/eIBTh5DXW9w