The energy requirements for any soldier in the field of battle are a major factor in the decision to arm and equip and military unit. The reliable supply of power is a need for any soldier, whether front line assault troop or rear echelon supply units. Soldiers need power to use weapons, armour and wargear, as well as for heating, food and light. With the most common weapon produced in the entire Imperium being the Lasgun, the need for cheap and powerful supplies of energy were vital, which is why this essay is as relevant today as it was in the age of the Great Crusade.
There are many power sources available to military units from the individual micro cells used in short range communication beads to the might Plasma Reactors used in Titans and the ships of the Imperial Battlefleets. Each source has its own virtues and drawback which we will discuss in this article.
Power Cells.
The requirement for high voltage, lightweight, rechargeable and cheap batteries has always been an issue. For millennia batteries relied upon crude chemical reactions to create low voltages but in M27, according to the most ancient histories available, the gift of the Achlmahdian crystal was given to humanity by the Emperor himself. This synthetic crystal has the ability to store power in its unique atomic structure. As energy is added to the crystal the bonds between the atoms distort and absorb the energy. This can be release by passing a small current through the crystal (often done using the peizoelectric affect). The Crystal has incredible energy storage capacity, being able to store in the order of 10^6 Joules per cubic cm of crystal. This incredible energy density allows the use of high wattage equipment such as Las and Melta weapons. It also allows the creation of micro-cells that can be used in the smallest items of wargear used by the Imperium such as digital weapons and bionic eyes.
Achlmahdian crystals are easy to recharge. They can have charge added to them mechanically (by exerting great pressure on them) or thermally (simply throwing them into a fire), though both of these carry a reasonably high rate of catastrophic failure causing the crystals to explode (note, using your power cell as an improvised grenade in combat is seen as destruction of Imperial property in the Guard regiments and thus carries the death penalty). More conventional recharging techniques require the application of an alternating current whose frequency matches the harmonic frequency of the crystal. This recharges the unit with near 90% efficiency, but as different size crystals have different harmonics users must first ‘tune’ their recharging pack.
For all their advantages Power Cells are only useful up to a point. Multiple cells can not be arranged, either in series or parallel, to provide higher outputs as there is a risk of harmonic feedback that could critical cell failure. As the physical size of the cell increases so does its costs. Crystals have to be absolutely flawless and the process that grows them is not perfect, crystals larger than a few cubic cm are almost impossible to create in an industrial quantity. As a result of this limiting factor there is a maximum wattage that these cells can provide and a corresponding maximum energy storage potential.
Hybrid Ionic Combustion Engine.
Many items of equipment have higher power needs than those that can be caters for using Energy Cells but are not larger enough to carry the combustion/turbine engines used in vehicles. This includes many Adeptus Asartes items including Power and Terminator armour, Land Speeders and Dreadnaughts. To meet the needs of these energy hungry items the Hybrid Ionic Combustion Unit (HICE, pronounced ‘hike’) is used. By using specially prepared solid fuels (usually in powder or granule form), mixed with its own oxidizer and salted with semi-stable radioactive elements the HICE can generate a powerful and reliable energy supply in a small and relatively light unit that does not require too much fuel. Before combustion the HICE ionizes the fuel and separates the electrons from the mixture. The ionized fuel is then mixed with the oxidizer and bombarded with electrons at the same time. The high temperature and energetic electrons are enough to cause the radioactive fuel element to decay, adding even more energy to the mix. The hot exhaust gasses are then passed through a turbine which is attached to a conventional generator, creating power. In some units thermionic capacitors are also used to generate power directly from the heat of the exhaust gasses.
HICE systems generate large amounts of power but give of toxic and slightly radioactive exhaust gasses (which can be visible as black smoke if the unit is operating under non-optimal efficiency). These fumes are a danger to all those nearby unless they have some form of radiological and environment protection. HICE systems give an excellent power to weight ratio but are difficult and expensive to maintain meaning that if a unit can use an alternative power supply it normally will. As they come with their own oxidizer they can operate under water or in a vacuum with no reduction in output and their fuel efficient is excellent, a suit of Power Armour can operate on less than 5kg of fuel/oxidizer for a full week and most Marines carry equipment to manufacture more fuel in the field from common elements (though the radioactive elements may not be manufactured in the field, the unit uses such a small quantity that most Marines carry a spare supply of up to 6 months worth as a precaution). As the fuel and oxidizer only become reactive once ionized there is no danger of a catastrophic failure due to fuel supply damage unless the user is in a highly ionized area.
Conventional Combustion Units and Turbines.
Internal combustion engines are a technology that predate all Imperial historical records. They are one of the oldest technologies in use in the galaxy, their discovery has been estimated to be shortly into the Industrial Age of humanity (as found when looking at primitive Human settlements that have been cut off from the Imperium and lost all technology). A variety of types of fuel is combusted in a pressurized container and the mechanical energy of the expanding exhaust gases is used to power the system. In more advanced systems a turbine is used, the fuel is used to create a powerful jet which is passed over a series of fans which are forced to turn. In either case the unit creates mechanical energy which can be used to drive a vehicle or create electricity through a generator.
This technology is millennia old but is always being refined due to progresses in fuel development. One of the most significant discoveries was made during the Great Crusade, an STC pattern for a multifuel engine that could run from an amazingly wide selection of combustible materials, from refined hydrocarbons to ethanol to promethium. Most Imperial engines are designed to use a version of Promethium, a much lighter and less viscous form of the fluid often seen in flamer units. This high octane fuel can be hard to supply reliably on the battlefront so it is vital that engines can run off other, local supplies such as petroleum, liquid propane gas and ethanol.
One of the most common non-frontline vehicles is the ‘RUM’ (refinery unit, mobile). This is essentially a large still fitted to into a Chimera chassis. Using genetically engineered micro-organisms any biological matter can be broken down into a variety of combustable components (including various alcohols and gasses such as methane and hydrogen). The incredible appetite of these micro-organisms allows the unit to create several tonnes of fuel per day in very high concentrations that would normally be toxic to regular bacteria. The range of materials that can be used in a RUM unit is outstanding, from wood (which has led to the myth that a Leman Russ can be fueled by wood, only partially true as its fuel can be created from wood) to food scraps and corpses (infact many Guard regiments do away with morgues and burials, allowing the troops to continue to be used in the Emperor’s service even after death).
The process which creates this ethanol fuel has some negative side affects though. Many Guardsmen have been seen siphoning this high octane moonshine for personal consumption. It seems that the common soldier considers it a mark of respect to toast a former comrade with super-strength hooch made from the dearly departed’s own biomass. Many Imperial Engineers have tried to stop this practice by adding highly toxic Promethium additives to the fuel once it has finished its distillation cycle. This has proven to be fatally toxic to Humans but allegedly adds a flavour which Ogryns are very partial to.
Combustion engines, although they have a relatively poor output/mass ratio, are cheap, reliable and can provide high power outputs making them popular for the Imperial Guard armoured regiments. Adeptus Astartes vehicles generally use the previously mentioned HICE units due to their better power/weight ratios.
Plasma Reactors.
In terms of both output and power to weight ratios the Plasma Reactor is one of the most versatile units in the Imperium. It is used in many war-machines, from the Shadowsword Titan hunter all the way to the Ramilies class Starfort.
A Plasma Reactor has, at its core, a magnetic chamber. Fuel is added to this chamber and suspended in the centre with the magnets. A Melta unit then superheats the fuel whilst it is being compressed by the magnets until the temperature and pressure are sufficient enough to start a controlled fusion reaction. This creates a vast supply of energy and, if required, plasma (for weapons and propulsion purposes) though bleeding plasma out of the reactor can temporarily reduce its power output.
Plasma Reactors are normally fueled using a mixture of Hydrogen, Deuterium and Tritium though other elements can be used though the efficiency is considerably reduced (and the required temperature and pressure for fusion is increased, increasing both the probability and severity of failure). The reactor builds up deposits of fused material over time, slowly decreasing output. The Reactor has to be purged systematically, a process which requires a full shut down and can take between hours and days, depending on the age of the reactor and the fuel used.
The main disadvantage of Plasma Reactors (other than their obvious size, weight and cost) is the risk of catastrophic containment failure or ‘meltdown’. If the control interfaces on the magnetic field are damaged then the plasma contained in will breach containment in a catastrophic plasma explosion which will almost certainly destroy the war machine with the reactor and cause substantial damage to any assets nearby.
Xenos Power Supplies.
A short mention must be made of some of the Xenos technologies that may be encountered on the battlefield.
Orks tend to use a mixture of power supplies, favouring crude internal combustion engines, steam power and in some cases highly unstable fission reactors (Orks seem nearly immune to the affects of hard radiation). Ork Gargants are generally seen as steam powered, in a way this is true, they generally used a pressurized reactor system with unstable nuclear elements to generate super high pressure steam which is then used either for mechanical energy or to power a generator.
Tau energy systems appear to use a variety of similar techniques to our own but in general are more efficient. It has been noted that many Tau power units are actually compatible with Imperial systems, it appears that the Tau have done this for trading reasons. As possession of unregistered Xenos technology is considered a capitol offence by the Inquisition there are very few instances of Imperial forces using these Tau units though some independent organizations have been spotted using them.
The Eldar have perhaps the least conventional system for creating energy. It appears that they can bleed energy directly from the Warp as and when then need. This is an obviously dangerous activity and many have argued that it is just another stone in the mountain of evidence of their treachery and love of all things Daemonic though captured Eldar wargear seemed to be very well warded against Daemonic possession.
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