Energy Sources, Conversion, and Storage: A Comprehensive Analysis

Posted on Jan 14, 2025 in Geology

Energy Perspectives

Energy: The property of matter and radiation which is manifest as the capacity to perform work.

Primary energy: Energy in the form that it is first accounted for in a statistical energy balance, before any transformation to secondary or tertiary forms of energy. For example, coal can be converted to synthetic gas, which can be converted to electricity: in this example, coal is primary energy, synthetic gas is secondary energy, and electricity is tertiary energy.

System: A part of the universe under consideration, separated from the rest of the universe (surroundings) with a well-defined boundary.

Energy Sources and Demand

  • Available forms of energy:
    • Mechanical: wind, water
    • Chemical: fossil fuels
    • Internal: geothermal
    • Nuclear: fissile materials
    • Radiation
  • Required forms of energy:
    • Mechanical: transport, work
    • Electrical: electronics
    • Internal: heating

Efficiency

  • Mechanical energy:
    • Into electricity: generators
    • Into internal energy: dissipation
  • Electrical energy:
    • Into mechanical energy: electric motor
    • Into internal energy: resistor
  • Chemical energy:
    • Into electric energy: limited – fuel cells
    • Into internal energy: combustion
  • Nuclear energy:
    • Into internal energy: fission, fusion
  • Internal energy:
    • Into mechanical energy: e.g., turbine

World Energy Resources and Perspectives

1) The Net Zero Scenario: Assumes that the policy in Rapid are added and reinforced by significant shifts in societal behavior and preferences, which will accelerate the reduction of CO2 emissions. Global carbon emissions from energy use fall by 95% by 2050, limiting the rise of global temperature up to 1.5 degrees Celsius.

2) The Rapid Transition Scenario (Rapid): Posts a series of policy measures, led by a significant increase in carbon prices and supported by more-targeted sector-specific measures, which cause carbon emissions from energy use to fall by around 70% by 2050.

3) The Business-as-usual Scenario (BAU): Assumes that government policies, technologies, and social preferences continue to evolve in a manner and speed seen over the recent past. A continuation of that progress, albeit relatively slow, means carbon emissions peak in the mid-2020s. Despite this peaking, little headway is made in terms of reducing carbon emissions from energy use, with emissions in 2050 less than 10% below 2018 levels. Primary energy demand increases by around 10% in Rapid and Net Zero and 25% in BAU.

Fuel Resources

Coal: The biggest reserves and usage of coal are in Asia Pacific and North America (USA), (proved reserves of coal USA 23%, Russia 15%, Australia 14%, China 13%).

Oil: The biggest reserves compared to production of oil is in South and Central America (Venezuela 17.5%) and in the Middle East (Saudi Arabia 17.2%). The biggest consumption is in North America and Asia Pacific.

Gas: The biggest reserves to production of gas is in the Middle East (Iran, Qatar), Russia. Biggest consumption in North America, the Middle East, Russia.

Nuclear: U-233, U-235, Pu-239, Pu-241 – U-235 is the only one we can get by natural resources, the rest are made in the lab. The biggest consumption of nuclear is in Europe and North America.

Renewable Energy Sources (RES): Current demand is around 6*10^20. Hydroelectricity consumption is biggest in Asia Pacific. Renewable consumption is biggest in Europe and Asia Pacific, smallest in Africa. Wind is the most popular, then solar and others. Biofuels: North America biggest, Asia Pacific smallest consumption.

Chemical Energy

Power plant: Industrial facility whose goal is the production of electricity from other forms of energy.

Thermal power station: Power station which needs heat to generate electricity. To obtain this energy, organic fuels are burned or nuclear fuels are broken.

Types of Thermal Power Stations

1) Steam turbine plant: Fuels used: coal-fired, nuclear, concentrated solar power, biomass, oil, gas turbine plant. Division of turbine by work character: 1) Condensing, 2) Back pressure, 3) Extracting. A pulverized coal-fired boiler is an industrial or utility boiler that generates thermal energy by burning pulverized coal that is blown into the firebox. Then the heat of exhaust gases is used to generate the steam.

Condenser: To condense exhaust steam of the turbine into the water.

Ejector condenser: Ejects air to maintain vacuum state inside vacuum steam condenser by using steam and condenser which condense and re-circulate used steam.

Cooling tower: Big chimney structure where the cooling water that comes from the condenser is cooled down using air.

Generator: Is the primary power conversion component of the power plant. Its function is to convert the thermal energy of the steam from the steam generator to electrical energy.

2) Combined Cycle (CC) plant: Heat recovery steam generator – mostly a heat exchanger where the waste heat is recovered, mostly used in CCGT where gas exhaust gases heat produces steam used in the steam part of CCGT.

3) Gas Turbine (GT) plant

4) Internal Combustion Engine (ICE) power plant: The prime mover is an ICE which has one or more cylinders in which the process of combustion takes place, converting energy released from the rapid burning of a fuel-air mixture into mechanical energy.

Bed gasifier: In moving-bed gasifiers, also referred to as ‘fixed-bed’ gasifiers, oxidant and steam are introduced in the lower part of the gasifier and flow vertically upward, while feedstock is introduced at the top of the gasifier. The feedstock is heated by up-flowing hot syngas.

Fluidized-bed gasifiers: They suspend feedstock particles in an oxygen-rich gas so the resulting bed within the gasifier acts as a fluid. These gasifiers employ back-mixing and efficiently mix feed coal particles with coal particles already undergoing gasification.

GE gasification: Produces synthesis gas from coal/water slurry and oxygen. Feedstock is pumped to an injector at the top of the gasifier. Coal reacts exothermically and forms syngas and slag. Syngas that leaves the gasifier is cooled by a radiant, convective heat exchanger or direct quench system. Slag is quenched in a water pool at the bottom of the reactor vessel and removed through a lock hopper. Radiant Cooling Operation Mode: absorbing the heat radiated from the surrounding. Quench Operation Mode: rapid cooling, as by immersion in oil or water, of a metal object from the high temperature at which it has been shaped.

Allothermal gasifier: This process means heating of biomass from an external source, i.e., by band heaters and heating elements. In coal gasification, coal is heated by an external heat source, is an example of allothermal gasification.

Underground Coal Gasification.

Fuel cells: Work like batteries, but they don’t run down or need recharging. They produce electricity and heat as long as fuel is supplied. They consist of two electrodes: a negative one (anode) and a positive one (cathode).

PEMFC (Proton Exchange Membrane): A type of fuel cell being developed mainly for transport, stationary fuel-cell, and portable fuel-cell applications. They have lower temperature/pressure ranges and a special proton-conducting polymer electrolyte membrane.

DMFC (Direct Methanol): Are a subcategory of proton-exchange fuel cells in which methanol is used as the fuel. Their main advantage is the ease of transport of methanol, an energy-dense yet reasonably stable liquid at all environmental conditions.

AFC (Alkaline): Is one of the most developed fuel cell technologies. They consume hydrogen and oxygen, to produce potable water, heat, and electricity.

PAFC (Phosphoric Acid): Uses liquid phosphoric acid as an electrolyte. First fuel cells to be commercialized. Such characteristics have made the PAFC a good candidate for early stationary applications.

MCFC (Molten Carbonate): High-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic matrix of beta-alumina solid electrolyte (BASE).

Nuclear Energy

Nuclear technologies. Advantages: Low share of variable cost in operation, very limited environmental footprint, no harmful gas emissions, fuel can be purchased at stable countries, high reliability. Disadvantages: Investment cost, expensive and cumbersome decommissioning, social problems, low flexibility, waste issue not fully resolved.

Reactor Classification

Neutrons Energy

1) Thermal neutron reactors: Energy below 0.1eV, needs moderator.

2) Fast reactors: Energy above 0.1 MeV, heavy coolants required, fuel breeding capability.

Moderator

1) Graphite (C). Advantages: Easy to obtain and process, resistant to high temperature (allows to increase efficiency). Disadvantages: Combustible, relatively high atomic mass.

2) Heavy water (D2O): Advantages: Allows to use natural uranium, low neutron absorption, not combustible. Disadvantages: Deuterium has higher atomic mass than hydrogen, cumbersome technology.

3) Light water (H2O). Advantages: Easy to get, lowest possible atomic mass of hydrogen, allows to use the same volume of water as moderator and coolant, low chemical activity. Disadvantages: Requires enriched fuel, low boiling point at limited pressure – limits temperature in loop-type reactors.

4) Other: Research reactors with other moderators or combination.

Coolant:

Air: Early research and in military reactors.

CO2: AGR, GCR. Advantages: Allows to increase core operating temperature. Disadvantages: Low specific heat capacity, high power consumption in blowers, over 700˚C chemically active.

Helium: GT-MHR, HTGR. Advantages: Allows to reach very high temperatures, chemically inactive. Disadvantages: Cost, low specific heat capacity, high energy consumption by blowers/compressors.

Heavy water: PHWR/CANDU. Advantages: Allows to use natural uranium fuel, high specific heat capacity, low power consumption by pumps. Disadvantages: Operating temperature limited by boiling point, cost.

Light water: PWR, BWR, VVER, RBMK, ACR. Advantages: Cheap, high specific heat capacity, low power consumption by pumps. Disadvantages: Operating temperature limited by boiling point, absorbs neutrons – results with higher required uranium enrichment level.

Liquid metal: FBR

Reactor Types

GCR. Specs: Coolant: CO2, Moderator: graphite, Fuel: natural uranium, Two-circuit system. Advantages: Simple design, can be cooled down by natural convection, on-line refueling. Disadvantages: High own power consumption, temperature restricted by fuel cladding material, no safety containment, low fuel burnup.

AGR. Specs: Tank reactor, Coolant: CO2, Moderator: graphite, Fuel: slightly enriched uranium, Two-circuit system. Advantages: Simple design, online refueling, high parameters of live steam, high gross efficiency. Disadvantages: Large own energy consumption, low burnup of fuel.

HTR: Specs: Tank reactor (concrete or steel tank), Coolant: Helium, Moderator: graphite, Fuel: uranium or thorium in fuel balls, Two-circuit system.

PMBR Specs: Tank reactor, Coolant: Helium, Moderator: graphite, Fuel: uranium or thorium in fuel balls, Single-circuit system: gas cycle with gas turbine, possibility of reloading fuel during operation and constant core characteristics, possibility of cooling the core by natural convection.

GT-MHR. Specs: Tank-channel reactor, Coolant: Helium, Moderator: graphite, Fuel: uranium balls in graphite prisms, Single-circuit system: gas cycle with gas turbine.

HTR Advantages: Online refueling, high efficiency, high parameters of live steam, online refueling, high flexibility + small units – not only baseload. Disadvantages: Operational problems: water leaks, corrosion.

PWR/VVER. Advantages: High reliability, common technology, reaction shuts down at LOCA. Disadvantages: Low efficiency, possibility of corrosion due to boric acid use.

BWR Specs: Steel tank, Coolant: H2O. Moderator: H2O. Fuel: enriched uranium. Single-circuit system. Production of saturated steam. Efficiency: approx. 33%. Start-up and shutdown: control rods: recirculation pumps. Regulation of campaign reactivity: control rods. Advantages: High reliability, simple design, no risk of corrosion (no boric acid), common and well-proven technology, chain reaction ends at LOCA, lower reactor pressure than in PWR. Disadvantages: Low efficiency, contaminated steam in the turbine, lower power density than in PWR, steam separator inside.

PHWR/CANDU. Specs: Steel tank, Coolant: D2O, Moderator: D2O, Fuel: natural or slightly enriched uranium, Two-circuit system. Advantages: Low pressure & temperature in calandria, radioactive isotope production capability, online refueling, low fuel enrichment. Disadvantages: Low efficiency, large core volume, high number of pressurized connections, necessity to produce heavy water.

LWGR/RBMK. Advantages: Easy to build, theoretical possibility of producing superheated steam in single-circuit, online refueling. Disadvantages: High positive void coefficient, graphite operating temperature above its flash point in the air, low efficiency, large core volume, no containment, insufficient safety systems.

FBR Specs: Pool or tank reactor, Coolant: liquid Sodium, Moderator: none, Fuel: MOX – PuO2 + UO2, Three-circuit system, Primary circuit, liquid metal, active, Indirect circuit, liquid metal, inactive, Secondary circuit, water and steam, steam turbine, very high power density in the core, fuel multiplication. Advantages: Fuel breeding, high steam parameters, high efficiency. Disadvantages: High melting point of coolant, Sodium-H2O heat exchanger.

Integral Modern Salt Reactor 2016, Terrestrial Energy engaged in a pre-licensing design review for the IMSR with the Canadian Nuclear Safety Commission and entered the second phase of this process in October 2018 after successfully completing the first stage in late 2017.

Magnetic Confinement Fusion: The toroid vacuum chamber contains gas at low pressure. It is the secondary winding of the pulse transformer. The current induced in the plasma heats it, and the associated magnetic field, together with the magnetic field generated by the coil winding wound on the chamber, protects and keeps the plasma away from the walls of the structure. The problem is the stability of the plasma.

Renewable Energy Sources (RES)

Energy from renewable sources: Energy from renewable non-fossil fuels: wind, solar, aerothermal, geothermal, hydrothermal and ocean energy, hydropower, biomass, landfill gas, sewage treatment plant gas, and biogases.

Non-renewable: Limited. Power depending on consumption rate, flexibility to shape the way of use, and low efficiency results. 1) Fossil fuels 2) Nuclear fuels: Uranium, Thorium, Hydrogen.

Renewable: Unlimited resources. The way of use dictated by natural conditions and low efficiency does not cause irreversible losses. Solar, wind, water, biofuels, geothermal.

Sun as energy source: It is a product of nuclear fusion. The amount of solar energy reaching the Earth’s surface depends on: latitude, season, the amount of clouds, time of day, air pollution.

Terminology: 1-Solar irradiance: power received from the Sun per unit area. 2-Insolation: sum of solar energy received per unit area in unit of time. 3-Annual sunshine: sum of hours when the sun really shines. 4-Hemispherical radiation: is the radiation reaching to hemisphere, consist with direct radiation received from angle related with solar disc, diffuse radiation and reflected radiation. 5-Diffuse radiation: sun radiation scattered by the atmosphere and surroundings. 6-Reflected radiation: radiation reflected from surroundings.

Solar thermal collector: Device that uses solar energy to obtain heat. Types: 1-Flat plate parts: absorber, transparent cover, thermal insulation, pipes with fluid, housing. 2- Evacuated tube: used for domestic heat water and heating rooms.

Solar collectors systems: Thermosyphon system and indirect system.

Photoelectric effect: Incident protons interact with atoms. Energy absorption causes emission of electrons.

Photovoltaic effect: Electrons absorb the energy of photons but emission does not occur. Solar cell types: 1-Monocrystalline Silicon: made from a single pure silicon crystal, expensive. 2-Multi-junction: efficient and expensive.

Off-grid system: Installations not connected to the electricity grid.

On-grid systems 1) Small scale. 2) Large scale: Solar thermal power plant: solar radiation is used to generate electricity.

Conventional hydroelectricity plants: Harness the energy produced by flowing water, using simple mechanics to convert the energy into electricity: 1) Hydroelectric dam: Most used water turbine: Pelton, Turgo, Francis, Dropeller, Kaplan. 2) Tides mechanism: Tides are very long-period waves that move through the ocean in response to the forces exerted by the moon and sun. They originate in the ocean and progress toward the coastlines where they appear as the regular rise and fall of the sea surface. 3) Ocean thermal energy: a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters. 4) Gravitation water vortex power plants: The water behind a hydroelectric dam stores gravitational potential energy and when water falls it is converted into kinetic energy, which turns turbines to generate electricity.

Wind power: The energy of wind originates from solar radiation energy. Wind turbines: Classification by application: Domestic (for individual users), Industrial (high-power devices). Classification by power: Micro (up to 100 W), Small (100 W-50 kW), Large (more than 50 kW). Classification by location: on-shore, off-shore. Classification by the axis of rotation orientation: vertical, horizontal.

Vertical: Advantages: Efficiency independent of wind direction, simple mechanical design, no noise, wind resistance, lack of vibrations, maintenance-free operation of generator set. Disadvantages: Low efficiency, small rotational speed it needs reentrant generator or gearbox.

Horizontal: Advantages: Higher efficiency than vertical, multi-blade has a tail which can automatically direct the blades to the wind, good with weak winds. Disadvantages: They require rpm reduction mechanism, require wind direction following mechanism, multi-blade system less effective.

Darrieus type wind turbines: It utilizes the “lift” aerodynamic force to rotate. By flowing around the structure, the wind creates a suction on the front side of the turbine, driving the wings to rotate. Disadvantages: Highly prone to mechanical damage, they need an external drive to start. Advantages: Much easier access than conventional wind turbines.

H-rotor type turbines: The rotor is a variation of the Darrieus rotor.

Savonius turbines: It uses mainly the power of wind pressure, often used as a drive in water pumps, the higher the ratio of height to diameter the greater the efficiency. Disadvantages: Low efficiency, sensitive to strong winds. Advantages: Simple structure, high warm-up torque, very quiet operation.

Drill wind turbines: Thanks to the helical twist of blades they can operate at a full range of wind speeds. Quiet and stable operation.

Geothermal energy: Deposits can be classified based on the type of the energy carrier:

1) Deposits of geothermal waters: May be classified depending on the pressure, reservoir shape, and surface morphology as: 1) artesian deposits, 2) subartesian deposits, 3) gravitational deposits.

2) Deposits of superheated steam: Passage of steam through dried rock produces superheating, after initial vaporization of water, the decrease in pressure produces increased boiling, with heavy exploitation, boiling extends deeper into hotter rock and the temperature increases.

3) Deposits of hot dry rocks: Extremely abundant source that is difficult to access.

Usage of geothermal energy: It can heat, cool, and generate electricity: It can be used in different ways depending on the resource and technology chosen. District heating: Heat networks supply heat from a central source to consumers, via a network of underground pipes carrying hot water. Heat networks can cover a large area or even an entire city.

Water geothermal power plants:

1) Dry steam: Plants use hydrothermal fluids that are already mostly steam, steam is drawn directly to a turbine, which drives a generator that produces electricity, condensed steam is reinjected into the reservoir.

2) Flash steam: Take high-pressure hot water from deep inside the ground and convert it to steam that drives generator turbines, when steam cools and condenses to water is injected back into the ground to be used again.

3) Binary geothermal power plants: Used where geothermal resources are not sufficiently hot to produce steam or where the source contains minerals or chemical impurities to allow flashing, here a geothermal liquid is passed through a heat exchanger.

Energy Storage

Thermal Energy Storage

Types: Tank water heat storage, ground heat storage, phase changed materials, molten salts heat storage, hot oil storage, thermochemical heat storage.

Mechanical Energy Storage

Types: Gravitational potential energy storage with solid masses, flywheels, pumped-storage hydroelectricity, compressed air energy storage. Advantages: Low maintenance and long lifespan, almost no carbon emissions, fast response times, non-toxic components. Disadvantages: Low storage capacity, high self-discharge.

Hydro storage (Pumped Storage): Efficiency: 70-80%, high flexibility of energy source; 100% of its power is reached in 10-30 s, limited locations, pumped storage is the only well-established energy storage concept that is available in a large scale; installed capacity 184 GW; 95% of energy storage installations worldwide. Advantages: Mature technology, capable of storing huge amounts of energy, high overall efficiency, fast response times, inexpensive way to store energy. Disadvantages: Few potential sites, huge environmental impacts, requires a significant huge water source.

Compressed Air Energy Storage: Advantages: Capable of storing huge amounts of energy, great efficiency, fast response times, inexpensive way to store energy. Disadvantages: Required sealed storage caverns, economical only up to a day of storage, not yet fully developed.

Electrochemical Energy Storage

Types: Rechargeable batteries, flow batteries, supercapacitors. Sodium-sulfur batteries: Advantages: Common technology, high potential for improvements. Disadvantages: Low energy densities, limited life cycles, require a lot of resources for production. Lithium-ion rechargeable battery charge mechanism. Superconducting magnetic energy storage: Advantages: Fast respond times, capable of partial and deep discharges, no environmental hazard. Disadvantages: High energy losses, very expensive in production and maintenance, reduced efficiency due to the required cooling process.

Electrical Energy Storage. Advantages: Fast response times, capable of partial and deep discharge, environmentally friendly. Disadvantages: High energy losses, expensive production and maintenance, reduced efficiency due to cooling.

Hydrogen Production

1) Based on coal and hydrocarbons: Steam reforming, dry reforming of methane, coal gasification, biomass gasification, coal or biomass pyrolysis, hydrocarbons thermolysis, partial hydrocarbons of hydrocarbons.

2) Based on water split: Electrolysis, photoelectrolysis, photobiological processes, thermolysis of water.

3) Other: Thermochemical cycles, methane hydrates, thermochemical split of hydrogen sulfide.

Steam Reforming 1) Feed Pre-Treatment. 2) Reforming & Steam Generation. 3) High Temperature Conversion. 4) Heat Exchanger Unit. 5) Purification Unit * optional, depending on reformer design a either heat exchanger for low-pressure reformer or compression to 1 bar for high-pressure reformer Flow Chart of a Steam Reformer.

Electrolysis 1) With water electrolyte 2) With replaceable cationic membrane 3) With oxygen electrolyte (steam) 4) In high-temperature electrolysers

Thermochemical Cycles The Photolytic Sulfur Ammonia cycle was presented as a four-step hybrid thermochemical cycle designed to make selective use of the solar spectrum with long wavelength spectral composition used to drive thermal processes and short wavelength spectral composition used to drive the hydrogen producing oxidation step using photolysis. The photolysis was carried out in the presence of a cadmium sulfide photocatalyst doped (or alloyed).

Alternative Energy Sources

Stirling engine: Heat engine that converts heat energy into mechanical work through the cyclic compression and expansion of a working fluid, operating on the temperature difference between hot and cold heat exchangers.

Micro-CHP is used for: ICE, Stirling engines, micro-turbines, fuel cells, and ORC.

Osmotic power generation: Harnesses energy from the movement of water molecules across a semipermeable membrane, driven by the osmotic pressure difference between salty and fresh water, to generate electricity.

Setur turbine.

Thermoelectric generators: Convert heat differences into electrical energy.

Wearable energy harvesters: Devices integrated into clothing or accessories that capture and convert ambient energy, such as movement, heat, or light, into electrical power to charge or supplement the power of wearable electronic devices.

Piezoelectric generation: Converts mechanical energy into electrical energy using materials with piezoelectric properties, which generate an electric charge in response to mechanical stress or vibrations.

MHD generator: Which can be open or closed.

Hall generator: A semiconductor device that produces a voltage proportional to a magnetic field perpendicular to the current flow, based on the Hall effect.

Montardy’s generator.

Disc generator: Electrical generator where the rotational motion of a disc-shaped rotor is utilized to generate electricity through electromagnetic induction.

Airborne turbines.

Bladeless wind power: Wind turbine which utilizes oscillating or vibrating structures, to capture wind energy and generate electricity.

Algae: To create Biodiesel, Biobutanol, Biogasoline, Methane, Ethanol, Green diesel, Jet fuel. Techniques for producing energy: closed loop, photobioreactors, open bond, turf scrubber.

Magma power.

Space-based solar.