Climate change, the prospect of fossil fuels shortages and political demands to reduce CO2 emissions mean new, major demands for knowledge that can help to optimise our overall energy production and enable us to better utilise the Earth’s green energy sources. Researchers from Aarhus University have developed the most comprehensive model based on 100 percent renewable energy to date.

How many solar cells are required compared to wind turbines if you wish to reduce excess production of electricity? Or, in other words: What is the technically optimal mix of solar and wind in the fossil free energy supply of the future?

This is the question that researchers from Aarhus University have found the answer to. They have studied current European consumption in detail based on more than 70,000 hours of weather and fuel consumption data and 2,600 different geographical measurement points.

The study is one of the world’s largest time series analyses of consumption and power availability, and it provides a good starting point for predicting the requirements for energy storage, transmission and reserve capacity in the renewable energy system of the future.

The researchers have calculated how many solar cells would be required compared to wind turbines to reduce the excess production of electricity or, more specifically, the mix of solar energy and wind energy which would provide precisely the energy production that best matches the consumption pattern and, at the same time, gives the most optimal conditions for utilising the energy.

On the road to lopsided production of renewable energy
The formula for this correct mix is an important intermediate result in the planning of fossil free energy supplies. Because if we extrapolate our current production of electricity to 2020, then Denmark alone will produce a surplus of 700 GWh of renewable energy. However, with the technically optimal ratio, this surplus production would instead be 300 GWh.

This is connected to the fact that solar energy is produced in a pattern that complements wind energy well – both in relation to daily and seasonal fluctuations.

In a sustainable energy system on a continental scale, these intermediate results could save enormous amounts of surplus energy.

The optimal mix
According to the researchers, the optimal energy mix between solar and wind power is around 20 percent solar energy and 80 percent wind energy. With this mix, approximately five percent more renewable energy can be integrated into our energy system.

An optimal energy mix reduces the production of surplus energy and thus the need for energy storage, which in Denmark alone is equivalent to between a half and one million electric car batteries. Or that each and every family changed their consumer habits and did all of their hot wash laundry all year round when it was windy and there was a surplus of energy.