What is the most efficient renewable energy source?

Aleksandar Boljevic

We’ve all heard of the numerous forms of renewable energy - solar, hydrothermal, tidal, wind, and so on. But have you ever wondered what is the most efficient of these sources?

Let’s start with what we mean by an efficient source. In physics, efficiency is defined as the ratio of useful energy (or power), such as the electricity we use daily, to the total energy (or power) output, such as the sunlight that reaches solar panels.

The coefficient of efficiency ranges from 0 to 1. Of course, these are only theoretical upper and lower bounds. No one would think up an energy source with an efficiency of 0 because then, well, that wouldn’t be an energy source. Similarly, efficiency will not equal 1 in almost all cases (matter-antimatter collisions being an exception). We do, however, strive to have the efficiency be as close to 1 as possible.

Now that we know what is meant by efficiency, let’s take a look at the renewable energy rankings.

1. Hydro energy harnesses the power of water in motion, such as water flowing over a waterfall, to generate electricity. Hydro turbines can convert as much as 90% of the energy received into electricity! That makes it the most efficient converter of energy by far.

2. Tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity. When it comes to efficiency, tidal turbines are not far behind their hydro counterparts, with 80% efficiency.

3. Biomass energy is plant or animal material. This acts as fuel in the production of electricity or heat. Examples of biomass energy are wood, energy crops, and waste from forests, yards, or farms. It is very difficult to measure efficiency when it comes to biomass. Why? Well, biomass comes in many different forms. The most common are wood, which when burnt, has 70-80% efficiency.

4. Wind energy is generated when the wind is transformed into mechanical power. It utilizes wind turbines, which turn electric generators to produce electrical power. Wind turbines typically have about 30-45% efficiency but can reach up to 50% on the windiest days. Remember, a wind turbine extracts energy from the wind’s store of kinetic energy, slowing the wind in the process. Thus, if a turbine had 100% efficiency, it would cause all wind flowing through it to cease.

5. Solar energy is radiant light and heat from the Sun that is harnessed through a range of ever-evolving technologies such as solar heating, photovoltaics, solar architecture, molten salt power plants, and artificial photosynthesis. The majority of solar panels have an efficiency of 15-20%, but some high-quality solar panels can exceed 22 or 23%! However, for most solar panels, 20% is the upper boundary.