Energy Conversion
Direct Electric Capture Technologies
https://www.osti.gov/servlets/purl/1130979
The Energy Conversion Matrix
Forms of energy are interchangeable. When gasoline is burned in an automobile engine, potential energy is first turned into heat. A portion of this heat, say 25%, is then converted into mechanical motion via pressure. The remainder of the heat is wasted and must be removed from the engine. A multitude of processes and devices have been found which make these transformations from one form of energy to another. Many of these are listed in the blocks in the image below.
Dynamic vs. Direct Energy Conversion
Our world is dominated by dynamic energy conversion, relying on transforming the energy in fuels into rotational motion through machines like engines and turbines.
Direct energy conversion allows us to convert thermal to electrical energy without the need for moving parts, opening doors to greater efficiency and reliability, especially in critical applications like space exploration and reliable long term power generation.
Direct Conversion Methods
Thermoelectricity - Harnessing Heat Differentials: Thermoelectricity, using the Seebeck effect, creates power from temperature differences across dissimilar materials. The advent of semiconductors has breathed new life into this method, allowing practical applications in power production. [pg 12]
Thermionic Conversion - Boiling Electrons for Power: This method involves extracting electrons from heated metal surfaces, using them to generate electricity. By overcoming the space charge effects with plasma, thermionic converters can efficiently transfer these electrons to produce power. [pg 16]
Magnetohydrodynamic (MHD) Conversion - Harnessing Conducting Gases: MHD conversion, distinct from thermoelectric and thermionic methods, uses high-velocity conducting fluids to generate electric potential, offering an alternative to the rotating mechanisms of dynamic systems. [pg 19]
Chemical Batteries and Fuel Cells: These devices derive their energy from the electrostatic bonds in chemical reactions. While batteries are limited by their fuel supply, fuel cells, continually fueled, offer a sustainable and efficient energy source, especially valuable in space missions. [pg 22]
Photo Voltaic Cells: Solar cells convert sunlight into electricity in semiconductor band gaps. Optimized to capture Ultraviolet photons, crucial for powering satellites and space vehicles. [pg 26] Additional band gaps for additional wavelengths of light that can be captured including the infrared or thermal energy. A Thermophotovolteic cell has achieved nearly 40% efficiency in laboratory conditions.
Ferroelectric Conversion - Harnessing Dielectric Properties for Energy Conversion: Ferroelectric conversion utilizes the unique properties of dielectric materials, such as barium titanate, which display good dielectric properties at low temperatures. When heated above 120°C, these properties rapidly deteriorate. This process involves heat absorption, leading to a realignment of molecules within the barium titanate latticework. Placing a slab of this material between the plates of an electrical condenser and charging it offers a novel method of converting heat directly into electricity. As the temperature rises above the Curie point, the condenser's capacitance significantly reduces, forcing it to discharge and move electrons through an external circuit, thus delivering useful electrical energy. This process represents a second-order transition in thermodynamics, where internal molecular rearrangements occur without a change of phase. [https://innovation.ox.ac.uk/licence-details/ferroelectric-energy-converter/]
Thermomagnetic Conversion - Magnetic Permeability and Energy Conversion: Thermomagnetic conversion is analogous to ferroelectricity, but instead uses a ferromagnetic core within an electrical inductance. When the temperature of the ferromagnetic material exceeds its Curie point, its magnetic permeability rapidly declines, causing a partial collapse of the magnetic field. This change delivers energy to an external load. Unlike ferroelectric conversion where energy is stored in an electrostatic field, in thermomagnetic conversion, it's stored in a magnetic field. Both ferroelectric and thermomagnetic conversions involve internal geometrical changes in solids, constituting second-order transitions in thermodynamics. These conversions do not involve phase changes like those in traditional heat engines using two-phase working fluids.
Thermoacoustic Stirling Generator:
Thermoacoustic conversion operates without moving parts converting heat into sound waves and then into electricity. It represents a significant advancement in energy conversion technology, combining high thermal-to-electric conversion efficiency with the reliability of a system devoid of mechanical components.
NASA and the Technical Institute of Physics and Chemistry at the Chinese Academy of Sciences demonstrated the practicality and high efficiency of this generator. The prototype showcases the potential of thermoacoustic conversion in achieving efficiencies comparable to traditional steam turbines in a long lasting package.
https://www.nextbigfuture.com/2023/11/breakthrough-thermoacoustic-stirling-generator-converts-to-energy-with-no-moving-parts.html Applications and Benefits:
Versatility: Thermoacoustic generators are adaptable to many heat sources, fission being my preferred long term choice.
Efficiency: They offer high thermal-to-electrical conversion efficiencies, making them competitive with traditional energy conversion methods.
Reliability: The lack of moving parts reduces maintenance needs and increases longevity.
Diverse Applications: Suitable for residential power systems, hybrid vehicles, refrigeration, heat pumps, and marine power systems.
Strontium 90 Nuclear Battery:
Harnessing Energy from Nuclear Radiation
Direct Use of Charged Particle Flow: Unlike solar cells which convert the kinetic energy of charged nuclear particles into electricity, this nuclear battery employs a more straightforward approach. They directly utilize the flow of charged particles as current.
In the typical design of a nuclear battery, a central rod is coated with an electron-emitting radioisotope, such as strontium-90. The high-velocity electrons emitted by this radioisotope cross a gap to a metallic sleeve, which collects and directs them to a load. These electrons possess a million times more kinetic energy than those in thermionic converters, allowing them to overcome any space charge effects that might hinder their movement. As a result, nuclear batteries, characterized by their simplicity and ruggedness, can generate microamperes of current at high voltages ranging from 10,000 to 100,000 volts.
Double Conversion Approach: A novel approach in nuclear batteries is the double conversion method. In this process, high-velocity nuclear particles are first absorbed by a phosphor, emitting visible light. These photons are then absorbed by strategically placed solar cells, which convert the light into electrical power. Although there's a loss of efficiency at each transformation step, the overall efficiency of this double conversion technique can range from 1 to 5%, making it a viable option for power supplies that require lower energy outputs, such as those in the watt and milliwatt ranges.
Increasing the Scale of Nuclear Energy
While Strontium-90 may provide small amounts of energy over long time periods powering satalittes. By using the heat generated from the radioactive decay in Plutonium we can charge a battery bank like they do on the perseverance and curiosity mars rovers. An amazing use case of nuclear fission sources of Heat & Electricity.
A Future of Direct Energy Conversion
A New Era of Efficiency and Reliability: The advancements in direct energy conversion methods promise a future where we can achieve higher efficiencies and reliability in local power generation technologies. From remote terrestrial locations to the vastness of space, these energy conversion technologies hold the key to long term sustainable energy solutions.
