Non-Fossil Electric Energy

W. Addy Majewski

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• Introduction
• Nuclear Power
• Hydroelectric Power
• Wind & Solar Power

Introduction

The key power generation technologies that are not based on the combustion of fossil fuels include nuclear power and several renewable power technologies:

• Hydroelectric power generation utilizes a water turbine to harness the kinetic and potential energy of flowing water. Hydropower is by far the largest source of renewable and low carbon electricity—in 2018, hydro provided 16% of the world’s electricity, ahead of nuclear power (10%) and wind power, solar PV, and other renewables [4389].
• Wind turbines convert the kinetic energy of wind into electricity. Commercial wind power generation has been increasingly employed since the beginning of the 21^st century.
• Solar photovoltaic (PV) cells are semiconductor devices that absorb sun energy and convert it into electricity using the photovoltaic effect. Wide-scale commercial application of solar generation has accelerated in the 21^st century, alongside wind power.
• Geothermal power utilizes natural underground reservoirs of steam or hot water. These heat resources, accessed by drilling deep wells, are used to drive turbines. Geothermal generation plays a limited role, as it is viable only in certain geographies, particularly in volcanic regions. The United States has the largest installed geothermal generation capacity, with most plants located in California and Nevada. Regions with large geothermal potential also include Indonesia and other countries on the Pacific ‘Ring of Fire’.
• Biomass such as wood can be used as fuel in thermal power plants. Whether biomass resources are renewable or not depends on the scale of exploitation. There have been several instances, historical and contemporary, of forests being depleted within just a few decades.
• Other renewable power technologies include ocean tidal energy, ocean wave power, and concentrating solar. Commercial application of these technologies remains very limited.

While renewable power generation utilizes renewable (and in most cases free of charge) fuels, the hardware and machinery to harvest renewable energy is not renewable and often not even recyclable. Renewable power installations—such as wind turbines and solar panels—have high resource demands, including several metals and minerals, which presents one of the barriers in their wide adoption [6317]. Renewable power plants also have a high fossil fuel footprint—from coal used to manufacture the steel and concrete structures to diesel fuel used throughout the entire supply chain during construction, operation and maintenance of renewable power infrastructure.

In some respect, renewable energy is a ‘smart’ use of fossil fuels that maximizes the amount of energy that can be extracted. For instance, the manufacture of polysilicon—a key material used in solar PV cells—has been concentrated in the Xinjiang region in China, which is the global hub for solar panel production. The solar-grade polysilicon is produced using local coal energy. Converting coal to solar panels can be seen as an ingenious way to increase the energy benefit of the otherwise stranded and costly to transport Xinjiang coal resources.

Different types of non-fossil power play different roles in the electrical grid. Nuclear power plants produce baseload electricity, which is essential for grid stability. Hydropower can provide dispatchable energy that can be quickly adjusted to balance power supply and demand in real time. Wind and solar generation, on the other hand, provide intermittent electricity that changes with weather, atmospheric conditions, and the time of the day. Wind and solar power are not dispatchable and cannot be used as baseload power. Hence, as their share of generation increases, intermittent renewables can create grid stability challenges. To ensure reliable power supply, wind and solar power require dispatchable fossil fuel backup or energy storage, such as pumped hydro or grid-scale batteries.

Figure 1 shows the global share of non-fossil power generation technologies. In the 1990s, non-fossil generation produced about 36% of global electricity supply. This percentage decreased to 31-32% during 2007-2013. Since then, the contribution of non-fossil electric energy has been increasing to reach 41% in 2024. Among the particular technologies, hydro remains the largest source of non-fossil power (14.2% of global power generation in 2024), followed by nuclear, wind, and solar.

As electric energy represents about 20% of the total primary energy supply, the contribution of renewable sources to primary energy consumption remains limited. In 2024, hydro provided 2.7% of the global primary energy supply, wind 1.5%, and solar PV 1.3%.

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