Keywords

1 Introduction

Batteries are used in a large number of different applications. The spectrum ranges from grid-connected stationary battery storage in the megawatt-hour range to extremely small batteries in the microwatt-hour range that can be integrated into electronic systems. Each use case places different demands on the battery. Accordingly, there are major differences between the battery technologies used, both at the level of the cells and at the battery systems level. In many applications at the system design phase, engineers select the battery technology in a tradeoff between cost and application requirements. The sweet spot in this tradeoff is different from one application to another. Scientific literature provides a set of KPIs to describe battery characteristics that allow to compare them with each other. In many cases these KPIs serve as a first orientation for which battery technology is is best suited for which application as shown in Fig. 6.1.

Fig. 6.1
A chart presents the most valuable characteristics of battery technology. It lists specific energy, specific power, energy density, power density, energy cost, power cost, lifetime, lifetime cycles, cell voltage, and efficiency of 6 different batteries.

Most valuable characteristics or KPIs for battery technology comparison [25]

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However, when the application requirements are analyzed in more detail, other aspects appear as relevant in the decision-making process, namely, cost, safety, environmental, and social, among others.

The battery market is therefore fragmented into many market segments that differ considerably not only in terms of the technology used but also in terms of market volume. The most important market segment by market size is batteries for road vehicles. Nevertheless, different market segments are described below and classified in terms of their specific requirements. These market segments are grouped into the classes stationary, mobile, and portable.

2 Stationary

Stationary battery storage systems are usually connected to an electricity grid. They provide services that serve the grid operation and decouple the generation and consumption of electricity over time. This facilitates the integration of volatile renewable power generation. In addition, they can be used to dampen peak loads and thus facilitate the integration of new consumers such as electric vehicles and heat pumps. Thus, stationary battery storage represents a key technology for the energy transition in the electricity grid. Figure 6.2 provides an overview of different storage technologies and their areas of application in the electricity grid.

Fig. 6.2
A chart marks the suitable, possible, and unsuitable applications of electrochemical, electrical, mechanical, and thermal energy storage devices. The application areas are renewable energy integrations, bulk energy, ancillary services, and energy management.

Stationary energy storage systems and their use cases [3]

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Home Storage

Home battery storage is mostly used “behind the meter” to optimize self-consumption via time-shifting of locally generated renewable energy. The most common combination is a battery home storage system with a rooftop photovoltaic system. Energy is stored during the midday hours. In the morning and evening hours, it is fed into the home grid to supply electrical appliances. The optimal storage size depends on electricity and system costs, load and generation profiles, energy consumption, and the size of the installed photovoltaic system. In addition, battery home storage systems can also be used to bridge interruptions in the power supply. The typical usable battery capacity of such storage systems is in the range of 2–15 kWh [27]. In contrast to other applications, the esthetics of the battery storage unit is also a purchase-relevant decision criterion here.

The demand for home battery storage will continue to increase in the coming years. The driving forces for market development are listed below:

  • Renewable energies and electrification: Residential buildings are increasingly being equipped with photovoltaic systems. Additionally, new electrical consumers such as heat pumps and electric vehicles are being added. Time-shifting of generated electricity behind the meter significantly increases the self-consumption rate and lowers energy supply costs.

  • Rising energy costs: Fossil greenhouse gas emissions are increasingly being factored into energy costs. Taxes and levies are designed to provide incentives to conserve energy. Political and economic crises repeatedly cause fluctuating prices on the energy markets. Home storage systems serve as enablers for personal energy cost optimization.

  • Guaranteed electricity supply: Not in every country electricity is reliably available 24/7. Blackouts or scheduled brownouts restrict the quality of life and can lead to consequential damages. Home storage systems make it possible to bridge gaps in the electricity supply.

  • Technological progress: The technology offers potential for further improvement. New battery chemistries like sodium ion promise a rapid further decrease in battery costs. Optimized software and electronics will increase round-trip efficiencies. This will improve economic efficiency. With increasing sales figures, economies of scale can be realized in production resulting in a further improvement of economic efficiency.

Industrial and Commercial Storage

The focus of industrially and commercially used battery storage systems is on peakshaving and uninterruptible power supply (UPS). Peakshaving serves to reduce the connected load, which is particularly relevant for companies in the manufacturing sector. The “behind-the-meter” battery storage system can reduce load peaks. For particularly short load peaks with steep power gradients, a combination with ultracapacitors can be useful. In UPS applications, battery storage ensures the power supply for machines and ICT systems. Especially for the operation of data centers, such UPS systems are an absolute necessity. Furthermore, the roofs of factory and office buildings are increasingly being equipped with photovoltaic systems. Even if the generation and consumption profiles usually have a considerably greater overlap here than in residential buildings, time-shifting can be used to optimize self-consumption. Comparing different companies for storage systems, the size of such battery storage systems typically ranges from 20 kWh to 2 MWh [10]. While the energy density plays a subordinate role for such applications, the price and potential energy cost savings have a major influence on the purchase decision.

The use of battery storage systems will continue to increase in industrial and commercial applications [4]. The main drivers for this are listed below:

  • Energy cost optimization: Grid connection costs are usually calculated on the basis of the maximum electrical power used. Peakshaving can reduce power peaks and thus energy costs. The same applies to optimizing self-consumption by time-shifting renewable energy production.

  • Sustainability reporting: Low greenhouse gas production and on-site generation and use of renewable energies have a positive impact on the sustainability of the company. Battery storage is an enabler for the optimal use of renewable energy. Positive sustainability reports can be used in advertising. Furthermore, sustainability reports are used by investors to analyze the company’s exposure to climate legislation. This can have an effect on the company’s cost of capital.

  • Security of supply: Power failures or voltage drops can affect technical systems. Considerable damage to plants and products can be the result. Battery storage works like an insurance against this risk. The willingness to pay is accordingly based on the amount of risk that can be avoided.

Utility Storage

Grid-integrated battery storage can provide various ancillary services listed in Fig. 6.2. The integration of battery storage systems is possible in the distribution grid as well as in the transmission grid. In the distribution grid, stationary battery storage systems primarily serve to stabilize the grid in the event of short-term fluctuations. The feed-in of fluctuating renewable energies and new consumers such as electric vehicles or heat pumps leads to an increased strain on the distribution grids. This can lead to voltage fluctuations. However, maintaining certain voltage bands (+/− 10%) is a crucial prerequisite for the reliable operation of electrical devices [16]. Grid-integrated battery storage systems can stabilize the grid voltage by feeding in or consuming active power. Via the inverter, battery systems can also provide reactive power, which also affects grid voltage. In addition, battery storage systems can have a dampening effect on voltage gradients and thus improve the voltage quality. In time-shifting and peakshaving operation, battery storage systems reduce grid load. In this way, the need for grid expansion can be reduced or delayed. In the event of a grid collapse, grid-integrated battery storage can maintain the power supply in smaller grid areas for a short time. If the grid does collapse completely, such storage systems can also be used for black-starting the grid.

When used in the transmission grid, the main focus is on providing control power. There must be a constant balance between generation and consumption in the electricity grid. If this balance is disturbed, balancing measures take effect, which are classified according to their time of provision as instantaneous reserve, primary control reserve, secondary control reserve, minute reserve, and reserve by the balancing group manager. The instantaneous reserve is the immediate compensation of power imbalances. In conventional power plants, it is provided from the energy of the rotating masses in turbines and generators. Therefore, it is also called spinning reserve. Primary control power must be activated within seconds and held for a period of minutes. In Germany, activation time is 15 s and power must be held for up to 15 min [9]. The following activation times are valid for power balancing in Germany, but there are comparable requirements in other electricity markets [24]. These requirements are similar in different electricity markets. Secondary control power must be capable of being fully activated within 5 min. The minute reserve must be fully activated within 15 min and be provided for at least 15 min. However, the provision period can also be up to several hours. If these measures are not sufficient, the balancing group manager activates further reserve capacities. Battery storage systems are able to provide all these balancing measures positively (energy injection) or negatively (energy absorption).

The demand for grid-integrated utility scale battery storage is much related to the chosen power generation mix. The continuing global trend toward the expansion of weather-dependent renewable energies indicates that the market will expand much further. However, the extent of market growth is difficult to estimate. The main influencing factors are listed below:

  • Grid relief: The integration of weather-dependent renewable energies and new electricity consumers creates major challenges, especially at distribution grid level. Grid-integrated battery storage can relieve the load on the electricity grid. In this way, grid operators can save costs and gain time for grid expansion or make it unnecessary.

  • Cost reduction: In control devices, power electronics, and battery technology, there is still great potential to further reduce the total cost of ownership. With regard to battery technology, cost reductions can be achieved through new cell chemistries such as sodium-ion batteries and possibly also second life batteries.

  • Demand side integration: It is uncertain to what extent the consumer side can be integrated into grid operation and to what extent consumers behind the meter will make their own optimizations. For example, electric vehicles have a huge storage capacity in total. However, it is uncertain to what extent the vehicle electronics, the cycle stability of vehicle batteries, and the charging infrastructure will enable the grid integration of electric vehicles.

Non-battery Stationary storage

In addition to battery systems and different cell chemistries, there are a number of other energy storage technologies that need to be mentioned here (also see Fig. 6.2) in order to compare battery technology.

  • Ultra-/Supercapacitor energy storage (SCES) is primarily suitable for very short-term, high-power electricity storage. Their use is particularly worthwhile in the case of rapid successive charging and discharging cycles. This is the case, for example, in the improvement of power quality. When electrifying applications with this requirement profile, combined systems with batteries and capacitors are increasingly being used.

  • Superconductive magnetic energy storage (SMES) can store energy in magnetic form in superconducting coils. They have a high-power density. The field of application corresponds to that of supercapacitors.

  • Compressed air energy storage (CAES) uses compressed air to store energy. Air is sucked in and compressed by a compressor and stored in a tank. Since large volumes are required, underground caverns, for example, in salt domes, are often used for storage. When energy is needed again, the compressed air can be expanded via a gas turbine. Heat recovery can significantly increase circulation efficiency. The shorter the cycle duration, the better heat can be recovered. Therefore, CAES are used as spinning reserves and for time-shifting.

  • Pumped hydro energy storage (PHS) stores electricity in positional energy. For this purpose, water is pumped into a higher basin. When energy is needed, the water is drained from the basin and passed over a turbine, which then generates electricity again. Due to its very fast reactivity, PHS is suitable for peakshaving and arbitrage trading but also for longer term energy storage.

  • Flywheel energy storage (FES) stores electricity in rotational energy. For this purpose, a heavy cylinder is rotated or decelerated by an electric motor. The energy that can be stored is comparatively limited. That is why there are only a few applications for this type of storage.

3 Mobile

Batteries are increasingly being used to power vehicles of all kinds—a domain previously primarily occupied by petrochemical fuels and internal combustion engines. However, fuels of fossil origin are not compatible with mitigating climate change. Therefore, governments around the world have taken steps to phase out internal combustion engines in the transport sector. In the European Union, for example, with a few exemptions, only zero-emission vehicles can be newly registered from 2035 [13]. Japan and China are aiming for full electrification of new car sales by 2035 [17]. Battery-electric vehicles are the most advanced technology to meet these requirements. However, the trend toward electrification is not limited to road transport. Electrification with the use of battery technology is also advancing in other areas such as micromobility, commercial vehicles, shipping, rail transport or aviation. As different as these application areas are, the suitable battery technologies are also very different. Each battery technology has its characteristic properties, just as each mobility application has its characteristic requirements. Table 6.1 shows a utility value analysis of which battery technology is suitable for which application [6].

Table 6.1 Battery technology to mobility application fit overview
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Micromobility

Micromobility includes e-bikes, electric scooters, and other small electric means of transport. They are mainly used for shorter distances in urban environments. Electric scooters in particular are offered as mobility as a service products by various providers in cities. Batteries are usually integrated into the product or can be removed and replaced completely in form of an encased battery pack. The design and size of the product is decisive for the degree of integration of the battery. Typical battery sizes range from a few 100 Wh to a few kWh [4]. Important criteria for the selection of suitable battery technologies in this market segment are cost, energy density, and charging rate.

Micromobility devices became possible due to low-cost batteries, compact and powerful electric motors, and advances in power electronics and control components. Due to the great success of e-bikes, powered scooters, powered self-balancing boards, powered skate boards, and many other devices, market diffusion is already more advanced compared to other mobile battery applications. Yet significant growth potential remains in the micromobility market, even if year-on-year growth rates are declining to single-digit percentages. The key growth drivers are listed below:

  • Growing urbanization: The global trend toward urbanization is changing mobility behavior as well. Congestion and growing environmental awareness lead to an increased use of alternative modes of transport. Battery-powered micromobility on short distances and paved surfaces in urban centers is a viable alternative to other modes of transport.

  • Convenience and accessibility: Battery-powered micromobility devices are a low-barrier complement to public transport in urban centers. For disabled people, they can facilitate access to mobility. It is also the most affordable form of motorised individual mobility.

  • Government incentives: Cities create incentives to improve air quality and decarbonize mobility. Battery-powered micromobility benefits from this.

Passenger Vehicles

This class of mobile applications represents the largest market segment in terms of market volume. Therefore, the class of passenger vehicles deserves further subdivision into motorbikes, cars, buses, and trucks.

For the application of batteries in motorcycles, the charging rate and the volumetric and gravimetric energy density are primarily relevant decision variables. The reasons for this are the limited construction space available and the narrow limits in the tolerable vehicle weight. Typical battery sizes are in the range of 5–20 KWh [4]. For less heavily motorized mopeds and scooters used in urban traffic, exchangeable batteries may also be an option. In those cases, priorities shift toward gravimetric energy density and cost. Such vehicles are typically equipped with batteries of 1–5 kilowatt-hours [4].

Battery-electric cars represent the single largest market segment. Depending on the size and weight of the vehicle as well as the intended use, different requirements for the battery technology apply (compare Table 6.1). Battery-electric cars are typically equipped with batteries from 30 to 110 KWh [14] with a growth trend. NMC cell chemistries are widely used. In cheaper vehicles with a shorter range, LFP is also used. For small vehicles with low range, the use of sodium-ion batteries may also be conceivable. For the selection of battery technologies for electric cars, the most important priorities are cost, volumetric energy density, and life cycle. Batteries are usually permanently installed in the vehicle in the form of a battery pack although some vehicle manufacturers also offer interchangeability of battery packs. These batteries are usually equipped with a conditioning system that can cool or heat the battery. Cooling is particularly necessary for fast charging. While charging, heat is generated due to the internal resistance of battery cells that must be managed in order not to endanger the thermal stability of cells. Moreover, the battery can be preheated in cold ambient temperatures to prepare it for charging and enable a higher charging rate. With regard to the integration of batteries into the vehicle, there are two opposing trends. Manufacturers like Tesla and BYD work on making the battery pack a structural part of the vehicle [28]. This saves weight and reduces the necessary installation space. Other manufacturers, above all nio, are opting for battery swap systems. This allows for greater flexibility and gentler charging. However, this greater flexibility comes at the price of disadvantages due to the standardized form factor of the battery pack and the more difficult thermal management. In addition, the construction and operation of the swapping infrastructure is associated with comparatively high costs. Therefore, vehicle-integrated battery systems are likely to be sufficient for most applications. Cars with swappable batteries primarily address the customer segment of businesspersons and travelling salespersons, since a costly battery-swapping infrastructure must be built and operated. Due to the cost premium, it is to be expected that cars with swappable batteries will initially be offered in the premium segment and purchased by people with high mobility needs and a high willingness to pay.

For buses, there are two different use cases. Most buses are used in urban public transport. This use case is characterized by frequent starts and stops as well as fixed routes. Longer stops, e.g., at terminus stations, allow for recharging of the batteries. Recharging can be done in different ways. However, automated pantograph systems are becoming increasingly popular. Depending on the route and charging opportunities, city buses are equipped with 200–500 kWh batteries [1, 7]. Due to frequent starting and stopping, there is a great potential for recuperation. For maximum utilization of the recuperation potential, batteries can also be combined with ultracapacitors. Here is also the biggest difference to coaches, since they are usually travelling at a constant speed over longer distances. In addition, there are fewer opportunities for charging breaks. For this reason, coaches are also offered with larger batteries beyond 500 kWh [1].

Battery-electric vehicles are the largest market segment for the application of batteries for the foreseeable future. More than 80 million passenger vehicles are sold globally [11]. By 2050, battery-electric vehicles will make up most of this market. In its net zero-emissions scenario, the IEA projects that by 2030 the global market share of electric vehicles will be around 60% [18]. This significant market growth is driven by several factors, which are listed below:

  • Environmental and climate regulation: In order to mitigate climate change and improve air quality in urban areas, governments are taking regulatory measures against internal combustion engine vehicles. Since this does not fundamentally change mobility behavior, battery-electric vehicles are among the beneficiaries.

  • Government incentives: In order to accelerate the market ramp-up, many governments provide substantial financial incentives for the purchase of zero-emission vehicles. In particular, countries with a strong automotive industry also directly promote the development and production of batteries.

  • Comfort: Even if charging pauses on long-distance journeys have a detrimental effect on comfort, battery-electric vehicles do offer some advantages. The interior can be designed more generously; the vehicle is significantly more quiet and less prone to wear and tear.

Commercial Vehicles

Commercial vehicles fulfill transport applications from urban delivery services to freight transport on international long-haul routes. The requirements for performance and range differ accordingly. In delivery applications, smaller vehicles below 12 t gross vehicle weight are commonly used. The requirements for these vehicles are similar to those for large cars and pickup trucks. Heavier trucks are used for short-distance transport logistics and retail deliveries. Due to the relatively short daily routes of less than 400 km, moderate battery sizes of 100 kWh to 500 kWh are mostly sufficient [26]. Long-distance road transport of goods is usually done with heavy duty long-haul trucks with larger batteries in the range of 350–1000 kWh [5, 26]. Figure 6.3 gives an overview of the frequency of the different applications and the average battery sizes installed [8]. The most common cell chemistries in commercial vehicles are NMC, LFP [20], and, coming up soon, LMFP [19]. The most important criteria for choosing the right battery technology are gravimetric energy density, life cycle, and cost. Compared to passenger vehicles, life cycle is of particular importance. Especially in long-distance traffic, mileages of more than 1000,000 kilometers must be achieved over the lifetime of the vehicle. Despite the disadvantages of batteries in terms of weight and charging time, the high degree of utilization of batteries in long-haul transport leads to unexpectedly positive cost-effectiveness.

Fig. 6.3
A graph of gross vehicle weight versus range or daily mileage. It is divided into 4 parts. The following average battery size and frequency of use cases are plotted. 228 kilowatt hour, 54.6%, 655 kilowatt hour, 23.4%, 130 kilowatt hour, 15.4% and 373 kilowatt hour, 6.5%.

Use cases for battery-electric heavy duty transport [8]

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Shipping

Shipping is a difficult field for the application of battery-electric propulsion systems. Large and heavy vessels require a lot of energy and thus also exceptionally large batteries. Nevertheless, battery-electric propulsion systems are increasingly being used in shipping. The first applications are pleasure crafts, touristic riverboats, and ferries. These applications combine relatively short routes and nearby charging opportunities. Norway is the global pioneer in the electrification of shipping. As of 2026, the country has declared its fjords to become the world’s first maritime zero-emission zone [21]. The first battery-powered ferries are already in operation. The Bastø Electric, for example, began operation in the Oslo Fjord in 2021. The ferry is 143 m long and has room for 200 cars, 24 trucks, and 600 people. Batteries with a total capacity of 4300 kWh store the energy [12]. In addition, it can be useful in regions that are less well connected to the electricity grid to set up buffer storage at piers to charge the ships’ batteries. Beyond that, battery-electric marine propulsion systems could also be used in coastal cargo shipping. A study published in 2022 concludes that the total cost of propulsion (TCP) of battery-electric vessels is competitive to internal combustion engine powered vessels up to a distance of 1000 km [22]. The authors estimate that the competitive route length will increase to around 3300 km in the near future. This is due to expected further reductions in battery costs and higher energy density as well as increasing TCP for internal combustion engine ships.

Battery-electric drives are becoming increasingly relevant in shipping. The largest number of sold propulsion systems is achieved in the segment of pleasure crafts. Passenger and container ships, however, require considerably larger batteries, so that a relevant market is emerging here as well. The most important market drivers are listed below:

  • Comfort: In the pleasure craft market segment, comfort plays a very significant role. Battery-electric drive systems are compact and low maintenance. They are also quiet and do not produce exhaust emissions. Integrated systems can also provide power for electrical devices on board. It is also possible to charge these batteries with onboard solar panels. Accordingly, a dynamically growing market is already developing here.

  • Environmental regulation: Emissions of pollutants from shipping are the subject of public debate. The example of Norway shows how states are setting regulatory frameworks that benefit battery-electric propulsion systems. Besides the Norwegian fjords, also pollutant emissions from ships on inland waterways in densely populated areas are relevant.

  • Corporate sustainability: Sustainability is becoming an increasingly strong selling point. This is especially true in tourist shipping.

  • Costs: Especially in the pleasure craft segment, there are synergy effects that justify higher costs. In commercial shipping, the economic competitiveness is much more important. The competitiveness of battery-electric propulsion depends on two opposing trends: firstly, the further cost degression of battery storage system and, secondly, cost increases of fossil fuel powered propulsion systems. Here, factoring in of the damage caused by CO2 emissions is a major cost driver.

Aviation

Aviation is one of those industries where avoiding greenhouse gas emissions is particularly difficult. One obstacle to the electrification of aviation is the very tight weight limits. Consequently, propulsion systems must provide a high energy density and, for takeoffs, also a high-power density. In addition, very strict safety requirements apply, because problems during flight can have devastating consequences. This combination of requirements poses a major challenge for new climate-friendly propulsion systems. Despite this, the use of battery-electric propulsion systems is being considered in aviation. Prototypes and demonstrators from various manufacturers have already proven the technical feasibility of battery-powered aircraft. This concerns small short-haul aircraft or vertical takeoff and landing (VTOL) devices. If batteries are to play a relevant role in aviation, however, battery technologies with significantly higher energy densities must be developed. Studies assume that at least 400 Wh/kg to 750 Wh/kg are necessary for regional air traffic. If traditional narrow-body aircraft designs are to be equipped with battery-electric propulsion systems, at least 600 Wh/kg to 820 Wh/kg will be required for commercial operation on regional routes [2]. Current lithium-ion technology cannot meet these requirements. Lithium sulfur batteries could theoretically achieve the required energy densities but are still under development. Key challenges would be higher discharge rates and a longer life cycle. Greater hope lies in the use of solid state batteries. Here, too, many challenges still need to be solved, especially to improve manufacturability. If solid state batteries with high energy density and good safety characteristics become available by the end of the 2020s, aviation will be one of the most interesting market segments for their commercial application. But the challenge of battery-electric flying is bigger than just changing the propulsion system. New aircraft designs are necessary to exploit all efficiency potentials. Decades of further development are necessary to enable widespread adaptation of battery-electric aviation in passenger transport. The first applications of this technology will be small short-haul aircraft for only a few passengers.

Aviation is a market segment in which battery-electric propulsion systems may play a role in the future. The prerequisite for this, however, is significant technological progress. Therefore, this market segment is prone to become a test field for novel high-performance batteries. Whether battery-electric designs will play a larger role in regional air traffic also depends on the progress made in the development of alternative drive technologies and synthetic fuels. The key market drivers are listed below:

  • New aviation concepts: VTOLs enable flight connections over short distances that were previously restricted to other modes of transport. Especially in densely populated areas, low noise and pollutant emissions as well as high safety standards are mandatory acceptance criteria for this technology. Electric propulsion systems with multiple rotors can meet these requirements. Various companies are developing and testing such concepts already. Another rapidly growing market segment is unmanned drones, which are being used in various fields of application. Military applications are a strong technology and market driver in this area.

  • Environmental regulations: Aviation is also experiencing increasingly stricter regulation of pollutant and greenhouse gas emissions. To some extent, it is already included in emissions trading systems. Regulatory requirements and rising costs associated with fossil fuels may improve the economic viability of battery-electric propulsion systems in aviation in the future.

Rail

Rail transport can be subdivided into light urban and tram transport, regional and long-distance passenger transport, and heavy freight transport. Overall, rail transport is already a very efficient and climate-friendly mode of transport. Nevertheless, there are use cases in the different areas where batteries should be considered. Urban rail passenger transport is already electrified to a large extent. Here, batteries can be used to make optimal use of the energy recovery potential of regenerative braking. Depending on the topology of the terrain and the dimensioning of the catenary network, the amount of energy that can be fed back into catenaries may be limited. Small batteries sometimes in combination with ultracapacitors can act as buffer storage and help to stabilize the voltage quality in the overhead contact line network. This can save up to 30% energy [15]. In addition, the construction of tram lines and catenaries in dense urban areas can lead to spatial conflicts with other infrastructures. With small batteries, trams can bridge shorter distances without catenary. This can simplify the traffic planning of intersections, for example.

Long-distance passenger transport is usually equipped with overhead lines, as long-distance routes are often at high capacity. In regional transport, the share of electrified routes is significantly lower. Here, battery-electric trains are an alternative to diesel-powered trains. This is especially true if parts of the route are electrified with catenaries. The trains’ batteries can then be recharged in these sections of the route. The first battery-electric trains are already in operation. Due to the good integration into the existing infrastructure, battery-electric regional trains are an interesting market segment. Depending on the route length, batteries with more than 300 kWh capacity are used. Due to the high total weight and the large transport capacity, the energy consumption of battery-electric trains is 3–8 kWh/km. Where there is no catenary infrastructure at all, battery-electric trains will eventually have to compete with other propulsion technologies such as hydrogen fuel cells and synthetic fuels.

In heavy freight transport, the comparatively low energy density of batteries becomes a problem especially over long distances. However, the use of battery-electric power trains would also be technically feasible here. More realistic, however, is the use of battery-electric freight locomotives in shunting operations, on factory premises, and on short regional routes.

Batteries for rail transport require a high energy density. This is particularly important when longer distances are to be covered. In addition, a high-power density is necessary to exploit the full potential of regenerative braking and quick acceleration. Another important aspect is the requirement for a very long life cycle. Trains are in continuous operation and cover several million kilometers over their lifetime. Accordingly, the battery must be able to withstand many charging cycles. In addition, there are high demands on safety and reliability. Particularly in freight transport, hazardous goods are also transported. Fire risks must therefore be avoided. Furthermore, in the event of a defect, a train may block a section of the track. This can lead to high consequential costs.

Rail transport is an interesting market segment for a relatively small number of large battery systems. Whereas in the past it was mainly hydrogen drives that were seen as a future technology here, interest is increasingly moving in the direction of battery-electric trains. The main market forces are listed below:

  • Environmental regulation: Stricter climate and environmental legislation also affects rail transport. Moreover, many railway companies around the world are partly or fully state-owned. Therefore, politics can exert more direct influence on investment decisions and accelerate the switch to more climate-friendly technologies.

  • Energy costs: Electric trains can recover energy when braking. With battery-powered trains, this is becoming possible even in areas without catenaries. Energy costs can be reduced through increased energy efficiency. The magnitude of this effect, of course, depends on the difference between electricity and fuel prices.

  • Improved performance: Compared to diesel engines, electric motors can be controlled better, and they provide full torque already at low speed. This has a positive effect on acceleration.

  • Comfort: In passenger transport, passenger comfort is also an important decision criterion. Diesel engines cause nuisance through exhaust fumes, noise, and vibrations, which have a negative impact on the passengers’ perception of comfort and quality.

4 Portable

Portable batteries have been the largest market segment in the past. This market segment covers a wide range of applications. These include consumer electronics, power tools, medical devices, and numerous other applications. The typical battery capacity is in the range of a few watt-hours. Batteries with a capacity of up to 1 kilowatt-hour are used in power tools. Portable batteries are usually directly integrated into the product. Depending on the size, energy requirements, and usage characteristics of the product, there are very different requirements for the battery technology. Accordingly, this market segment offers many small niches for manufacturers of special batteries. The various niche applications also offer interesting market entry opportunities for the first-time commercialization of new battery technologies. Due to the great diversity of battery applications, with relatively small market volumes, the individual applications are only briefly described below [4].

  • Telecommunications: The market segment is very established and the products are mature. The market is saturated and the number of smartphones sold has been declining slightly since 2017. Lithium-ion battery cells in laminated cell formats with form factors specially adapted to the product are used to a large extent. The capacity of these batteries is in the range of 4–20 Wh. This market segment is very cost-sensitive.

  • Laptops and tablets: The market for laptop and tablet batteries is saturated. Laptops reached peak demand in 2011 and tablets in 2014. Since then, sales figures have stagnated. In the past, 18,650 format round cells were more common, but in the competition for thinner and lighter laptops, many manufacturers are increasingly switching to specially designed pouch formats. Nearly all batteries used are lithium-ion.

  • Power tools: The market for power tools continues to grow dynamically. More than one million units are sold annually. The market covers a broad spectrum from low-end solutions for occasional users (6 V, 10 Wh) to powerful professional tools (36 V, > 50 Wh). Increasingly, Li-Ion batteries are prevailing over NiCd batteries. The power-tool manufacturers expect from batteries above all low prices, fast charging, and high energy density. For professional tools, an improved life cycle of more than 500 cycles is also important.

  • Medical devices: Batteries are used in medical devices such as implants, defibrillators, hearing aids, and prostheses. Particularly in the case of implants and hearing aids, extreme requirements are placed on batteries due to the small packaging space. As these requirements can be very specific, various cell chemistries are used in special cell formats. The market for medical battery applications is growing dynamically. On the one hand, this is due to the constant expansion of the product range, but also to an aging population in wealthy industrial countries.

  • Household devices: Batteries are increasingly being used in household appliances such as shavers, toothbrushes, or vacuum cleaners. The market is growing dynamically, even if there are major differences between the individual product categories. Lithium-ion batteries have replaced other cell chemistries in many product categories. The market segment is very price-sensitive. In addition, short charging times and low self-discharge are expected.

Besides the market segments mentioned, there are numerous others, such as toys, mobile video game consoles, sports equipment, smartwatches, or wearable electronics, which will not be discussed in detail. However, the large number of applications shows the great potential for smaller manufacturers of special batteries. The special requirements create the necessary conditions for the introduction of new battery technologies. For this reason, the small-scale consumer battery market cannot be neglected.