Energy Sources: Conventional, Alternative, and Mineral Resources
Energy: The Ability to Do Work
Energy is the ability to do work. 99% of the energy used on Earth comes directly or indirectly from the sun. Energy can appear in many forms: calorific value, electromagnetic, mechanical, potential, nuclear, etc. However, we primarily use conventional energies such as those derived from fossil fuels, nuclear fission from uranium, and hydropower.
Energy Use
Quality of Energy
Higher-quality energy is more concentrated, while lower-quality energy is dispersed over large volumes. Even if present in large quantities, low-quality energy has limited practical utility.
Profitability
Profitability is crucial for using an energy source and depends on its accessibility, ease of operation, and transportation. The price of an energy source significantly influences its profitability.
Energy Systems
An energy system encompasses all processes performed on energy from its source to its end use. The phases are as follows:
- Capture or extraction of primary energy
- Transformation into secondary energy
- Transportation of energy resources
- End-use energy consumption
A converter is a system component that transforms energy from one form to another for easier transport or use. Each conversion process involves some energy loss.
Energy Efficiency
System performance, or energy efficiency, is the ratio of energy output to energy input, expressed as a percentage.
Energy Cost
Energy cost refers to the price paid for end-use energy. However, hidden costs are associated with equipment and facilities throughout the energy process.
Conventional Energy
Fossil fuels remain the dominant energy source. However, this reliance is unsustainable as many fossil fuels are finite.
Fossil Fuels
Fossil fuel use refers to the estimated total amount present in the Earth’s crust. Reserves are the discovered amount of a fossil fuel that is economically recoverable. Currently, 79.6% of commercial energy used worldwide comes from burning fossil fuels. The solution is to gradually transition to alternative energy sources with lower environmental impacts.
Coal
Coal formed from accumulated plant remains at the bottom of swamps, lagoons, or deltas. In the absence of oxygen, these remains underwent fermentation. Coal has high calorific value and is abundant (estimated reserves for 220 years at current consumption rates). However, it is also the dirtiest fuel due to its high sulfur content. Burning coal releases large amounts of SO2, a major contributor to acid rain. Coal is primarily burned in power stations to generate electricity. While eliminating thermal power is currently impossible, strategies exist to minimize its impacts:
- Substituting coal with fuels containing less sulfur
- Pre-processing fuel
- Designing more efficient thermal power stations
Oil
Oil originated from the mass death of marine plankton due to temperature or salinity changes. Sedimentation with silt and sand formed sapropel muds. The organic matter transformed into oil, while the silt and sand became bedrock. Oil is transported through pipelines or, more commonly, large tankers, which pose a high risk of accidents. Crude oil, a mixture of hydrocarbon gases, liquids, and solids, requires fractional distillation to separate the different fractions based on their boiling points. Further treatments are necessary to make the oil suitable for consumption.
Natural Gas
Like oil, natural gas formed from the fermentation of organic matter within accumulated sediments. Its extraction is cost-effective as the pressure from the sediments forces the gas to flow naturally. Natural gas is transported mainly through pipelines and used directly in homes, industries, and thermal power plants, where it is replacing coal. Natural gas is an ideal fuel for the transition to renewable energy sources.
Nuclear Energy: Fission
Initially seen as a solution to global energy problems, nuclear power is now considered dangerous and inappropriate.
Operation of a Nuclear Reactor
Nuclear reactors work by bombarding uranium-235 nuclei with neutrons, causing them to split into lighter nuclei. This process releases energy and more neutrons, creating a chain reaction. Moderators control the reaction rate by absorbing neutrons. The primary circuit, in contact with radioactive material, is confined within the reactor vessel. A secondary cooling circuit cools the steam from the primary circuit. A third circuit liquefies the steam produced in the secondary circuit.
Hydropower
Hydropower harnesses the potential energy of water flowing from mountains to the sea. Reservoirs capture the water, and opening floodgates releases energy to drive turbines. Hydroelectric power is low-cost, requires minimal maintenance, and produces no pollution. However, it negatively impacts biodiversity, fish migration, river flow, and water eutrophication. It also poses geological risks by accelerating erosion and sedimentation.
Alternative Energy
Factors to consider when assessing the viability of alternative energy sources include their availability, cost, and the infrastructure required for their use.
Energy from the Sun
The sun is our planet’s primary energy source, but Earth intercepts only a fraction of its energy, which is of low concentration.
Passive Architectural Systems
Bioclimatic architecture focuses on designing energy-efficient buildings that are passively heated or cooled, such as those with well-insulated walls and roofs.
Solar Thermal Power
Solar thermal power plants use concentrated sunlight to produce electricity. Collectors, such as parabolic dishes, parabolic troughs, or flat mirrors, capture and concentrate sunlight.
Photovoltaic Solar Power Plants
Photovoltaic solar power plants directly convert sunlight into electricity using monocrystalline silicon cells. These plants generate pollution-free electricity with no noise or moving parts and require minimal maintenance and no water. However, they require significant space, have a visual impact, and their energy production is variable.
Biomass Energy
Biomass, derived from forestry, animal waste, or garbage, is a renewable, cheap, and clean energy source. However, transporting biomass is expensive, and its renewability depends on sustainable practices.
- Municipal waste increasingly contains combustible components. The high cost of modern waste incineration has led to exploring energy recovery from combustion.
- Organic waste can be transformed into liquid or gaseous biofuels. Ethanol is produced from the fermentation and distillation of grain. Other biofuels include methanol and bio-oils.
Wind Energy
Wind energy uses wind turbines to convert wind energy into electricity. While wind energy is pollution-free, it has a visual impact, can harm birds, and may increase erosion.
Energy Independent of Solar Energy
Tidal Energy
Tidal energy harnesses the variations in sea level caused by the gravitational interactions of the Earth, moon, and sun. Dams built across bays capture the tidal flow to generate electricity, similar to hydroelectric dams.
Geothermal Energy
Geothermal energy utilizes the Earth’s internal heat. Geothermal plants pump cold water underground, where it is heated by the Earth’s heat. The resulting steam or hot water is used for electricity generation or heating. While geothermal energy is clean, it is not renewable as the thermal energy of wells lasts only about 15 years.
Hydrogen Fuel
Hydrogen, the most abundant element in the universe, is considered a potential eternal fuel source. The Kyoto Protocol promotes decarbonization and clean energy, increasing the importance of hydrogen as a fuel. Electrolysis, using electricity to split water into hydrogen and oxygen, is a promising production method. Another method, still in early development, uses sunlight to split water molecules (photosynthesis).
Nuclear Fusion Energy
Nuclear fusion involves fusing light nuclei to create heavier ones, releasing enormous energy. This reaction requires extremely high temperatures to create plasma, the fourth state of matter. As no material can contain plasma, magnetic confinement is used in experimental reactors.
Efficient Use of Energy
Energy conservation is crucial. Cogeneration, the combined production of two useful forms of energy, is one energy-saving mechanism. Specific measures for efficient energy use include:
- Increasing efficiency in the electric grid
- Implementing negative savings systems, where power companies financially support consumers who purchase energy-efficient appliances
- Evaluating the real and hidden costs of energy consumption
- Reducing consumption in various sectors, such as the automotive industry producing more fuel-efficient vehicles
- Implementing personal saving measures, such as using public transport, buying energy-efficient appliances, and increasing recycling
Mineral Resources
Our society relies heavily on a continuous flow of raw materials. Mineral resources have been extensively exploited throughout history, with extraction techniques evolving alongside technological advancements.
Metallic Mineral Resources
Metallic minerals are used for metal extraction and energy production. Minerals are extracted from deposits, areas with high concentrations of specific elements. Economically viable deposits, called mines, contain a high proportion of a particular metal. Mined metals are rarely found in pure form and require processing. Ores are classified as abundant or scarce based on their availability. The operation of a mine depends on the economic demand for the metal it contains. Technological advancements can transform previously uneconomical mineral resources into reserves.
The steel industry extracts iron from ore. The resulting iron’s carbon content determines whether it becomes cast iron or stainless steel.
Mining
Mining significantly impacts the environment, including:
- Impacts on the atmosphere
- Impacts on water resources
- Impacts on the ground and soil
- Impacts on flora and fauna
- Impacts on landscape morphology
- Socio-cultural impacts
Non-Metallic Mineral Resources
Minerals Used as Fertilizer
Essential minerals for fertilizers include phosphorus, nitrogen, and potassium.
Rocks Used in Construction
Various rock types are used in construction, including:
- Stone blocks, used for building and monuments since ancient times
- Rockery, crushed rock used for road surfaces, railroads, and concrete
- Sand and gravel, extracted from gravel pits
- Cement, a mixture of limestone and clay heated to high temperatures
- Concrete, a mixture of cement, sand, and gravel
- Plaster, made from calcined gypsum rock
- Clays, used as building materials since ancient times
- Glass, made by melting and rapidly cooling readily available raw materials