How do renewable energies work?

2 min read

Renewable energies are sources that regenerate naturally and do not run out, unlike oil, gas, and coal. They transform natural phenomena into electricity or heat [1].

The fundamental principle

All renewables convert a natural phenomenon into usable energy:

The two large families

1. Intermittent sources (weather-dependent)

• Solar: produces only during the day and in good weather
• Wind: produces only when there is wind

Problem: it is not possible to control when they produce. Solution: batteries, pumped-storage hydroelectricity, interconnections.

2. Programmable sources

• Hydroelectric: controlled by opening/closing the floodgates
• Geothermal: produces 24/7
• Biomass: produced when needed

How each one works

Photovoltaic

Light hits the silicon in the panel → electrons move → electrical current. No moving parts.

Wind

The wind turns the blades → a generator transforms the rotation into electricity.

Hydroelectric

Water descends from a dam → hits a turbine → the generator produces electricity. It is the most efficient (90%).

Geothermal

Drilling is done down to hot rocks → the steam turns a turbine. In Italy, we were the first in the world (Larderello, 1904).

Biomass

Wood, agricultural waste, or organic waste are burned or fermented → heat or biogas.

Why are they important?

1. Zero (or near zero) CO2 emissions during operation
2. They do not run out
3. Energy independence
4. Falling costs: photovoltaics are now the cheapest source

The main limitation

Intermittency: sun and wind are not always present. Storage (batteries, pumping), smart grids, and a mix of sources are needed.

In Italy, renewables today cover about 35-40% of electricity production.