Military energy storage technology
The military are closely watching the emergence of new technologies, in particular, the advent of advanced batteries, microgenerators, fuel cells, solar energy sources, supercapacitors, which are designed for energy storage.
A full combat kit of soldiers weighs a lot, but combat missions now involve carrying a large number of the latest electronic devices. The use of more efficient equipment and smart energy management technologies would greatly facilitate the mass of this equipment. Therefore, it became necessary to search and explore new technological developments. In turn, in the most advanced programs of military modernization, the development and management of electricity is central.
The processes of standardization and integration into NATO are extremely complex, because there is no single NATO standard for connecting devices or voltage in the systems for ensuring the activities of a soldier. Therefore, as a rule, developers direct their main efforts to the development of distributed and centralized energy saving systems.
The distributed system is characterized by the fact that each separate part of the equipment is equipped with its own battery, and communication with the remaining parts is carried out exclusively for data transmission. The centralized system is characterized by the fact that the battery pack, which is included in it, is integrated into the backpack energy system, and is a unit with personal electronics.
Thanks to a centralized system, it is possible to reduce the burden on a person, as well as the volume of logistic operations, which is achieved by using a single rechargeable unit instead of several batteries, which is the source of energy for the equipment. To use them efficiently, it is necessary that all devices have the same voltage, or have their own power control systems, or the power management unit. The use of centralized power circuits is more suitable for use in modern technologies, in particular, in electronic fabrics and flat cable wiring.
The electricity consumer is now also becoming a small weapon. Optical sights, laser pointers, illumination devices, image intensifiers and thermal imagers are no longer a novelty. Many military also do not exclude the possibility of upgrading and upgrading weapons through the built-in data transmission and power supply. For example, the LAND 125 Australian soldier equipment upgrade program includes an improved Steyr F88 rifle, equipped with a battery pack that supplies power to additional devices.
ISSE DE&S and ABSL Power Systems have jointly developed lightweight batteries for BOWMAN ultra-short-range radios that have a longer lifespan. The batteries are based on the lithium-carbon monofluoride compound, which has recently been increasingly used.
The chemical reactions of batteries use oxygen, as a result of which electricity is generated. Lead-acid batteries, for example, oxygen is produced by electrolyte with sulfuric acid. In lithium-air batteries, oxygen is obtained from the atmosphere, thereby reducing the mass of the battery. In theory, lithium-air batteries get a higher energy density, equal to 1000W / h per 1 kilogram of cell, but in practice, batteries of this type do not yet reach this density. In addition, these batteries are not able to give a high output power, and in practice rechargeable models have not yet been implemented. In addition, there are certain problems with durability and safety, because lithium is a highly reactive substance and can explode or ignite if damaged or carelessly handled.
The British MoD is currently implementing the RBDS program, which aims to reduce the burden on the soldier to 25 kilograms. It is based on the development of personal energy saving and electronic systems. The end result should be the creation of an integrated architecture of energy and electronic systems that will rely on the main power source having an energy density of the order of 600-800 W / h per kilogram. The first prototypes were created in 2011 year, and working samples may appear in a few years.
The RBDS program provides for consideration of the application of various concepts in order to achieve step changes in the energy density of energy sources.
It must be said that scientists and industrial groups are engaged in research of various technologies, in particular, software agents who are able to perform intelligent energy saving management, as well as fuel cells, promising chemical compounds, photovoltaic arrays, energy storage, electronic fabrics and micromotors.
Thus, in one of the programs of the UK Ministry of Defense, a study is being conducted on biomechanical energy storage, which is that body movement is used to release energy, which is used to ensure the operation of a personal radio station. Research "Solar Soldier" is exploring a multi-level photovoltaic device that supplies energy to devices. In addition, there is another area of research, which is aimed at the development of rapidly deployable printed antennas, which can be worn on the body and with their help accumulate radio frequency energy. The need for high power in certain short time intervals makes us pay attention to promising supercapacitors.
A large amount of research on advanced batteries focuses on the use of lithium-air systems, which we mentioned above. Due to the fact that the use of practical lithium-air systems is irrational, in the last few years new batteries with a lithium-ion composition have appeared in the world. They are lithium-iron-phosphate safe batteries, which have high peak power and high energy density. Among the manufacturers of such batteries, the leading positions are occupied by the American company A123 Sustems and the Canadian Phostech Lithium. The peculiarity of new batteries is that they have a much greater energy density, so when recharging can provide a reduction in logistics tasks.
There is another direction in the development of batteries, which is the merger of two technologies - a capacitor and a battery. A capacitor is a pair of conductors that are separated by dielectrics. A potential difference accumulates between these conductors, which is an electrical static charge. When the positive and negative poles are connected, the capacitor discharges. Electric intensity is measured in farads, but recently there have appeared multi-capacitor capacitors, which contain a large electrical charge in a small volume, can be quickly discharged and recharged. Their disadvantage is the inability to maintain charge for a long time. Due to such characteristics, supercapacitors can supplement batteries in cases when high impulsive power is needed for a short time period.
The use of energy as a whole is very important, regardless of the type of power architecture. So far, soldiers have already learned how to use energy more rationally by controlling energy consumption by turning the equipment on and off. At the same time, automatic control systems will make it possible to extend battery life and reduce the level of workload.
Especially important is the effective management of energy consumption for soldiers in a combat situation. For example, in Afghanistan, infantrymen and communications workers who conduct two-day patrols on rough terrain can carry up to 11 a kilogram of batteries. At the same time, almost half of the mass of batteries is used for protection, while for a meter-long radio station, only 39 percent is used. The remaining 22 percentages are divided between a universal battery, a high-frequency radio station, and commercial elements.
In order to reduce the weight of the batteries, on the order of the British military, ABSL Power Systems Ltd developed a new device that can extract the remaining energy from non-rechargeable dead batteries. A device called SPC, in addition to extracting energy from batteries, can do the same with other possible sources of energy. This device can be connected to vehicle batteries and transfer the required amount of energy to a rechargeable device. In addition, the device can be connected to a solar panel, then it will turn into a battery charger.
Portable generators equipped with small internal combustion engines have long been used on the battlefield. Such generators are economical and reliable, but they are not easy to carry due to their rather big weight. This has led scientists and industry to develop miniature generators or even microgenerators. The first type of device is very close to the engines dronesand will soon be on the market. As for the second type, these are microelectromechanical systems that are manufactured using semiconductor technology.
For example, Cubewano has been developing projects aimed at creating devices that, with a small weight (on the order of 10 kilograms), would have an output power of 2 kW. Such a device could provide energy to a group of 8-12 soldiers for 72 hours. Sonic rotary engines from this company use spark ignition, and can run on different fuels.
As for MEMS internal combustion engines (microelectromechanical systems), they are still being researched to solve the problems of sealing, mixing, lubrication, ignition, engine diagnostics, heat generation control, and layout of additional systems.
MEMS rotary engines, developed at the University of Berkeley, are capable of producing about 26 milliwatts of energy. The same program exists in the University of Cambridge. In addition, Berkeley is also developing a mini-rotor engine that could produce 10-100 watts. Such engines could replace batteries.
As for fuel generators, they have long been the focus of attention of the military. This is due to the higher energy density of the fuel compared to chemical compositions. Fuel cells are capable of generating energy while air and fuel are supplied to them. For some time it seemed that such elements would press the batteries, becoming the preferred portable power sources. But in practice, this did not happen due to problems with the supply of fuel. In addition, the problem lies in supplying them with hydrogen, which is necessary for combining with oxygen and generating current. Hydrogen is very problematic to transport, because it is explosive and has a low energy density. Storing it in a liquid state is also associated with certain problems, since it requires very low temperatures and high pressure. All these characteristics make hydrogen very impractical to use, especially on the battlefield.
Fuel cells may well work on kerosene or diesel fuel, but this requires additional processing of petroleum products, and the necessary equipment is extremely expensive.
In the end, all these problems have led to the fact that at the moment the main developments of fuel cells for the military are focused on the use of alcohol fuel, in particular, ethanol and methanol.
Fuel cells are at the center of two developments of the British laboratory of defense technology and science: the RBDS-CV program to reduce the burden on the soldier and the personal energy source Personal Power Source.
Qinetiq and ABSL are involved in the development of PPS, working on the creation of two fuel cell systems: Strand A and Strand B. The first system is designed to allocate power of the order of 7,2 kW for two days. Its use is possible in power portable electronics and communication equipment, in particular, BOWMAN C4I and FIST. The weight of the source is about 1,4 kilogram, and he has an energy capacity of 250 kW per hour per kilogram.
The companies are engaged in joint development and a second source, which is a combination of battery and fuel cells. The proton exchange membrane uses solid colorless boron-nitrogen hydride as a source of hydrogen. The weight of the second source will be about 6,3 kilograms, and its energy capacity will be equal to 220 kW per hour per kilogram.
There is another promising fuel cell proposed by SFC Energy, a lightweight portable device for military use called the JENNY 600S. It uses direct methanol oxidation technology. It can be worn on the body, as well as used for the work of remote devices.
At present, it is impossible to determine which of all the listed technologies is the best. All of them are in the process of development and improvement, and it is quite possible that in the future the appearance of devices that will combine these technologies in themselves is possible.
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