Vijay Jayaraj
Although solar and wind technologies are touted as next-generation energy sources, they have only been shoehorned into the grid through government decrees and subsidies. The reason they have not been freely adopted by investors and consumers is that solar panels and wind turbines have woefully low energy densities.
Energy density is defined as the amount of energy stored in a given unit of mass or volume – this metric is critical in determining the feasibility of an energy source. Usually Joules per kilogram (J/kg) is used as the unit of mass, or Joules per cubic meter (J/m3) is used as the unit of volume. Typically, this expression is expressed in units of million joules or megajoules (MJ).
The energy density of wood, which was widely used before the advent of coal, was only 16 MJ/kg. Society is willing to adopt fossil fuels because of their significantly higher energy concentrations: coal has about 24 MJ/kg; oil, 45 MJ/kg; and natural gas, 55 MJ/kg. In a completely different league, nuclear fuel (depending on the type) has an energy density of about 4 million MJ/kg and is sure to be widely used as society advances in the 21st century.Yingshi century and into the next.
Lithium-ion batteries are considered important for making up for the abysmal reliability of wind and solar power. However, most commercial-scale batteries have energy densities below 1 MJ/kg, orders of magnitude lower than wood.
Hydrogen is considered a future fuel with only one-third the energy density of wood.
As one would expect, solar and wind fall short in terms of power density, a measure of energy production. In terms of land use, natural gas power plants generate 1,000 watts per square meter, while solar and wind power generate 5-20 and 2-3 watts per square meter.
The remarkable efficacy of fossil fuels has enabled a quantum leap in human productivity, fundamentally changing the trajectory of civilization. This property enables the creation of compact, portable and efficient energy systems to power equipment ranging from small engines to large manufacturing complexes. It can be adapted to industrial processes that require a large amount of heat or a large amount of electricity in a short period of time.
Transportation, manufacturing, agriculture—almost every aspect of modern life—have changed. Cities are becoming larger and more complex, global trade is growing exponentially, and technological innovation is accelerating at an unprecedented rate. Ultimately, the ability to generate large amounts of electricity on demand, combined with the development of extensive distribution grids, brought electricity to billions of people and greatly improved living standards around the world.
Fossil fuels are particularly important for energy-intensive industries such as steel and cement production. These sectors not only require large amounts of heat but also the specific chemical properties provided by fossil fuels.
Energy and power density don't tell the whole story. Relative abundance and ease of extraction and processing are important factors that make fossil fuels superior to other sources.
Another is the power plant's capacity factor, or the ratio of its actual output to its potential output if it were to operate continuously at full nameplate capacity. The capacity coefficient of coal-fired power plants is close to 50%, and that of natural gas combined cycle power plants exceeds 55%. The average capacity factor of nuclear power plants reaches an astonishing 93%.
However, due to the dependence of wind and solar energy on weather conditions and the amount of sunshine, their capacity factors are lower than 35% and 25% respectively. This means that wind and solar power cannot be turned on whenever energy is needed. They also can't quickly adjust output as demand changes. In other words, they generate energy when resources are available rather than when they are needed.
Fossil fuels are vital, not only in helping developing countries scale up rapidly, but also in wealthy countries that need to sustain economic growth and continue to provide energy to industry and households at affordable prices. Even Tesla’s Musk uses petroleum-derived fuel—rocket-grade kerosene—for SpaceX’s Falcon rockets.
Calls to abandon coal, oil and gas would set society back hundreds of years, while human nature is to move forward – and even upward toward other worlds. It’s simply not in our genes to succumb to this nonsense.
This review was first published on BizPac Reviews July 16, 2024.
Vijay Jayaraj is a researcher at the CO2 Alliance, Arlington, VA. He holds a master's degree in environmental science from the University of East Anglia, UK, and a postgraduate degree in energy management from Robert Gordon University, UK
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