Image from Kevin Williams (copyright; used with permission)
Depending on circumstance and available technology and resources, various means of power-generating technology may be used. Categories of energy source include chemical fuels, various planetary renewable sources, nuclear, solar, and matter/energy conversion devices.
Chemical power generation exploits chemical disequilibria within an environment, typically those created by an ecosystem (natural or otherwise) or mechosystem.
For those who live in the oxygen-rich atmosphere of a typical Gaian world, wood, peat, and other vegetable matter can be burned, either for direct use of the heat as in primtech cultures or for conversion to mechanical or electrical power as in Lowtech or Middletech cultures. However, even with the most efficient wood-burning devices this is only practical if the population is very small relative to the environment, and the ecosystem is robust, and so it is only done in planetary environments or in the very largest megahabs.
A somewhat more sophisticated and higher tech alternative to the burning of vegetation, widely used on less developed terraformed and partially terraformed worlds or in some midsized habs is the use of methane gases and synthetic fuels produced by decomposing or specially grown and processed plant material or animal waste. A further development of this strategy for the creation of useful fuels from biomass involves genetically modified organisms that produce the fuel directly. Even this strategy can have its drawbacks, see for instance the Algaehol Bloom Disaster. Fuels made in this way can be used to power internal combustion engines similar to those that were popular during the late Industrial and early Information age of Old Earth.
Only relatively short-lived low to middle tech industrial civilisations, such as Industrial and Information age Old Earth or some xenosophont civilizations engaged in the burning of fossil fuels. Though civilizations can grow rapidly in size and sophistication with the energy bonus from these sources, those that fail to find alternative sources before environmental effects take hold or the supply of such fossil sources runs out either go extinct or drop back to a lower level of complexity. In any case, fossil fuels such as oil, coal, and natural gas are extremely rare in the universe given the scarcity of natural garden worlds, and those few garden worlds that have been settled typically have very strict regulations regarding their use.
However it is produced, the burning of organic matter releases carbon dioxide and, without sequestration technology, can very quickly destabilize the microclimate of even quite large orbitals. On planetary surfaces the result is a greenhouse effect, since heat being trapped in the atmosphere by the accumulated carbon dioxide, which is opaque to infrared rays. Although this is welcomed on cooler partly-terraformed worlds, it is quite undesirable on Earth-type fully terraformed planets.
In an oxygen-bearing atmosphere, hydrogen fuels may be employed, usually as a Middletech to Hightech option. As for biofuels the ultimate source of the energy is typically solar power, and the hydrogen is simply a useful medium. Sources are typically self-maintaining and neumann-capable, and range from gengineered algae through neogens to advanced nanotech or synanotech organisms that form part of the local ecosystem and/or mechosystem. The resulting hydrogen is used in fuel cells or magnetohydrodynamic (MHD) turbines.
This is a very large category of energy sources that may be harvested on a planet, or in some cases on a very large hab. These relatively low impact energy sources include wind, tidal, geothermal, and temperature gradient power, on or in a planet, and for installations in orbit around a planet electromagnetic gradients may also be tapped. These natural energy sources are tapped a variety of devices, ranging in complexity from the simplest Primtech waterwheel to advanced Hightech superconductors and in size from tiny devices to power handheld equipment to megaprojects that power cities. In the Information Age, one widely used form of power generation using a renewable energy source was Ocean Thermal Energy Conversion (OTEC), using temperature gradients in the oceans of Earth-like worlds to produce power. Later ATEC devices based on thermal gradients in the atmosphere became prominent. Such usages, together with widespread use of Solar and Nuclear Fusion and the adoption of non-polluting nano/bio-technologies has long meant that the per capita effect of a late Middletech to early Hightech population on most planetary or megahab biosystems is minimal.
Nuclear power is generated through the fission or fusion of atomic nuclei.
Although uranium and thorium, two elements that can be used to generate power by fission, are much more common throughout the universe than fossil fuel, fission power is not often used in hi-tech societies. This is because of the impact on the environment from mining radioactive materials, and from the build-up of long term radioactive waste which can be harmful to bionts, sybonts, and many kinds of artificials who depend on nanotech or electronics, unless they are specifically designed to survive damage from particle radiation. Once mining, transport and disposal costs are factored in, the energy returned over energy invested (EROEI) is generally quite low. However, fission is often used as an intermediate stage during the development of a colony, especially in locations remote from populations of individuals likely to be affected. Many vec-only societies, such as the Metasoft corporate clade Shonbus Robotics in the Perseus Rift, do make extensive use of cheap and widely available fissionable materials for power generation and even short-range shuttles.
Larger power sources, mostly for large spacecraft, ships and submarines, and large energy hungry cities, are various types of fusion reactor. The plasma is confined by a magnetic bottle of various geometrical configurations. Fusion is safer than amat and is very widely used as a power source in middle and high tech polities and worlds throughout the galaxy. Most fusion reactors are supervised by superturing expert systems and AIs. Fusion power is used extensively by Hider and Backgrounder societies that live on hydrogen rich icy bodies far from the local star. Many hider habitats use a so-called 'hotpoint' to generate the energy needs of the economy by fusion.
Solar power is power harvested directly from the natural electromagnetic radiation of a star. Almost all the energy used on most planets and sunward orbital habitats is collected by orbital solar power platforms. These convert incident light into electrical energy using vast sheets of nanotech solar cells. For planets, the energy is transmitted to the surface in the form of microwave beams which are collected by rectenna arrays in sparsely populated regions, or via superconducting wires in beanstalks.
Solar power may be used to create amat or other fuels as an energy storage medium, so that the energy of the local sun can be stored and used far from the star (in an interstellar spacecraft for example) .
This covers a wide variety of energy sources that use some other method than the fusion or fission of atomic nuclei to convert matter directly to energy.
Amat is mostly produced in amat farms near stars, ultimately from the stellar energy flux, and is widely used throughout the galaxy in the form of pion-antipion, or hydrogen/antihydrogen reactions for powering spacecraft, large-scale industrial orbitals, and megastructures. Because of the danger of catastrophic explosion should the magnetic bottle collapse and all the amat interact with normal matter at once, amat power generation is generally not allowed on inhabited planetary surfaces or in populated orbitals.
Monopole Conversion works on the same principle as the conversion drive starship. While providing near limitless power, and avoiding the dangers inherent in amat storage, this method of energy generation requires access to magnetic monopoles or monopole matter (magmatter). For this reason, matter conversion requires the assistance of at least a second singularity transapient or a 'seedstock' supply of monopoles from which additional monopoles can be 'bred' to power new reactors. More details here.
Regardless of the design, the output of a conversion reactor is usually used to create a high temperature plasma from which electricity can be extracted via standard magnetohydrodynamic methods. Conversion technology can also be used for propulsion or in weapons.
Black Hole Power Generators
The energy of Hawking radiation produced by a small black hole is considerable, and a widespread industry exists dedicated to the creation of such small holes, and the extraction of energy from them. Extra mass can be added to such a hole, making them efficient mass-to energy converters. One efficient design is the 'Hawking's knot'.
Amat Farm - Text by M. Alan Kazlev, modified by Steve Bowers Vast banks of solar power collectors which power multicolliders optimally designed to produce antiparticles. The vast showers of collision products which result are sorted magnetically; antimatter particles and other useful species are collected, cooled and held in electric/magnetic traps.
Atmospheric Thermal Energy Conversion Towers - Text by AI Vin These towers come in two basic types; updraft and downdraft. The first type, the downdraft tower, makes use of the thermal energy inherent in Hadley Cell Circulation Zones. The second simply makes use of the thermal siphon/chimney effect. They first became common in the Information Age on Old Earth and are still used on a variety of natural and artificial worlds for power generation, environmental control and terraforming, or both.
Binerator - Text by M. Alan Kazlev A megascale electrical engineering device built around the interstellar plasma flow between unequal size stars in a binary system. The hollow tube like device uses charged plasma particles flowing through it to produce electricity.
Biopower - Text by Anders Sandberg In some worlds a system of living solar collectors for powering underground biospheres is employed - e.g. the Zoeific Biopolity and the Arcadians would build such systems when settling an otherwise inhospitable world. The bases are visible only as verdant green smears of shimmering electromoss, with the tunnels far below the surface.
Capacitors - Text by Stephen Inniss A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric (non-conductor). Advanced designs allow capacitors to act as potent energy storage devices.
Conversion Drive - Text by Adam Getchell, Todd Drashner, Mark Mcamuk, and Chris Shaeffer, updated by Ithuriel Conversion drives (or monopole catalyzed fusion drives, as they are more formally called) use magnetic monopoles to increase the efficiency of a standard fusion drive up to nearly 100% if so desired. These systems were first developed by Second Singularity transapients. They are currently the most commonly used drive for interplanetary or interstellar travel.
Core Breach (hardware) - Text by M. Alan Kazlev When the casing or shell or container field of a nuclear reactor or ship drive system is penetrated, resulting in melt-down, release of radiation, super-heated plasma.
Deep Well Industrial Zone - Text by Todd Drashner Heavy duty industrial and manufacturing zones are most often found in the Inner Sphere and most heavily developed areas of the Middle Regions.
Energy - Text by M. Alan Kazlev The capacity for doing work. Energy can change from one form (heat, chemical, nuclear, potential energy) to another but is always conserved. In amat, magmatter catalyzed, and nuclear reactions, mass can be converted into energy.
Fossil Fuel - Text by M. Alan Kazlev Naturally-occurring, energy-rich carbon-based substance, such as shale, petroleum, coal, or natural gas, in a Gaian Type world's crust that was formed from ancient organic material. During the Industrial, Atomic, and early Information ages on Old Earth fossil fuels were burned in a criminally negligent manner, resulting in drastic climate change and ecological crisis that was only repaired during the late Interplanetary Age.
LifeFruit - Text by John B Generates ATP (adenosine triphosphate, a basic biologic energy storage molecule), but is one of the more power-hungry forms of astragen. LifeFruit typically requires earth-type solar energy levels.
Photoelectrochemical Cell - Text by M. Alan Kazlev Generic term for a wide range of cheap and easily fabricated, flexible photovoltaic device based on nanocrystalline materials and conducting polymer films, that provide a very high efficiency ratio of conversion of sunlight to electrical power. Widely used in many space habitats and for ground-based planetary power production for remote habitats and instruments.
Q-Battery - Text by Adam Getchell and Todd Drashner High Singularity technology that allows the extraction and manipulation of the stored vacuum energy contained in depleted Q-balls.
QED Fusion Reactor - Text by M. Alan Kazlev, Inspired by an entry in the Lunar Institute of Technology The electrostatic fusion reactor first suggested by Robert Bussard of 20th century Old Earth (C.E.), uses fusion fuel confined by a spherical voltage potential well of around 100,000 volts. It makes an excellent, and fairly low tech (late Information Age / early Interplanetary Age equivalent) light power plant, that it can be used as part of a basic high thrust to weight ratio propulsion system for spacecraft and aircraft. Basic propulsion versions have a specific impulse of between 1500 and 6000 sec.
Self-Propulsive Tethers - Text by Steve Bowers Satellites which are joined by tethers orbiting any world with a magnetic field will generate electrical power by passing through the lines of magnetic force; this energy can be used to power ion thrusters for example and thereby power rotating tether systems, amongst other uses.
Sunline - Text by Todd Drashner and Steve Bowers A ring of fusion-powered illuminators inside a jovian world or orbiting a brown dwarf or dim red star, designed to focus light on various nearby planets, moons, asteroids or orbiting habitats.
Tritium - Text by M. Alan Kazlev Radioactive isotope of hydrogen with mass (nucleon) number of 3. It has a half-life of 12.5 years. The nucleus contains one proton and two neutrons. Tritium is widely used in fusion reactors and for fusion-based interplanetary ships.
Turbine Plants - Text by John Edds Various species of genetically engineered plants which produce electricity by mechanical means.