Batteries Must Evolve To Support Many Evolving Technologies
Battery or a group of cells converts chemical energy into electrical energy. Electricity is needed to drive almost all modern machines and gadgets and batteries are needed where electricity cannot be supplied e.g. in portable devices or as a backup when the power supply is disrupted.
Batteries are classified on the basis on their chemical composition. There are alkaline and zinc carbon batteries used in consumer electronics and toys. Lead acid batteries are cheap, rugged and used in vehicles. Nickel based batteries offer higher specific power (KW/Kg) and higher specific energy (KWhr/Kg) and are used in aircrafts and consumer electronics etc. The earlier NiCd based batteries have given way to NiMH due to toxic nature of Cadmium. But it is Lithium based systems referred to as Li-ion batteries that are at the forefront of battery innovation. They have energy densities higher than that of Nickel-based systems and hence weigh less for the same energy needs. They also have the highest number of charge-discharge cycles.
Though batteries receive less media attention, they have been responsible for wide spread acceptance of electronic devices e.g. cameras, camcorders, mobile phones, laptops, desktops etc. However, for many emerging technologies, batteries are the biggest concerns.
Renewable energy sources
As per International Energy Agency, in 2013 renewables accounted for almost 22% of global electricity generation. This share will continue to increase. Two of the biggest contributors to this will be solar power and wind energy. However, both of them have a serious drawback, the production of electricity from them depends on the vagaries of nature e.g. solar power cannot be generated in nights or is generated less efficiently on cloudy days. Similarly, wind energy cannot be generated when the air is not moving. Hence, they need batteries to store electricity when they can generate and release when it is needed. The criticality of batteries will increase as the share of renewable energy in the overall grid increases. Other renewable sources e.g. tidal power, waves etc are in infancy but will need batteries for the same reason. Currently, Lead-acid batteries are common as they are cheap but as they last for a limited number of cycles, they are giving way to Li-ion batteries. Companies e.g. Dong, GE etc offer hybrid installations which include the battery generators.
Electric Vehicles
Electric vehicles could be cars, trucks, buses, airplanes or even rickshaws or cycles. In case of rickshaws or cycles batteries only replace manual labour and current technologies support the needs. In case of airplanes, the benefits of using electricity are numerous. Fuel costs about one fifth to one-third of the operating costs of airlines, depending upon the price. Electric motors are a lot quieter, so they could allow more night flights. Of course, use of electricity will reduce pollution and maintenance as electric motors would have less moving parts. But the weight of the battery is an important consideration and current level of technologies do not support a fully electric commercial size aircraft. Nickel based batteries are used as Lithium based ones have safety concerns. Airbus, Rolls-Royce and Siemens are developing a hybrid electric engine. Norway aims for all short-haul flights to be 100% electric by 2040.
Most of the current research is focused on cars. There are various models already available in the market e.g. Nissan Leaf, BMW i3, Toyota Prius etc. Their charging times are up to 4 hrs. It seems that Tesla is the leader here. Its Model S 85 can run for 424 km on a single charge. But that adds 540 Kg to the weight of the car. Tesla has even come up with a truck called Semi while a startup, Proterra has developed electric bus. Li-ion batteries have specific energy is in a few 100 Whr/Kg while for gasoline it is 13 KWhr/Kg. From the total cost of ownership perspective, electric vehicles are more expensive than petrol or diesel ones. Battery costs are falling. Bloomberg (December 2017) says that the average EV battery costs now $209 per kWh and this needs to halve to make electric vehicles cost competitive.
Internet of Things (IoT), Wearables and mobile devices
As per Gartner, IoT (Internet of Things) will connect more than 20 billion devices by 2020 and about 500 devices in a typical home by 2022. IoT is an important use case of 5G networks. These devices will need battery power to remain connected. New wireless standards such as Bluetooth® Smart (also known as "BLE") or ZigBee reduce battery consumption and allow coin cell batteries to be used. While the current battery technologies support IoT, the numbers are overwhelming. This has led to an exploration of an alternative approach called Energy Harvesting (EH). Also called power harvesting it is a technology that aims at collecting energy from ambient external sources such as heat, light, vibrations, radio waves etc. It produces very low power levels on the order of several microwatts (10-6W) to milliwatts (10-3W) but that is enough for sensors that are battery optimized.
Wearables, or wearable technology, are devices or gadgets that a person wears on their body. Wearable devices in a variety of formats including watches, wristbands, and eyeglasses are being developed. Wearable technology related to human health tracking is gaining traction. They have almost similar battery needs like IoT devices but also need to be as small as possible. Besides Energy Harvesting, research is happening on printable batteries. Various universities are working on the same, e.g. The University of Manchester has demonstrated graphene-based batteries while University of California San Diego has demonstrated zinc based printed batteries.
Applications used on mobile devices e.g. smartphones, tablets and even laptops are getting data intensive and richer in interfaces. They need batteries that last longer and can supply more specific power.
Future
Various new technologies of batteries are under development. Lithium can hold the highest amount of charge by weight. Various variants of Li-ion are being developed e.g. Lithium-Air whose theoretical specific energy is 13 KWhr/Kg but has the smaller number of cycles, Lithium Metal and Lithium Sulfur both of which have higher specific energy than Li-ion, Solid state Lithium which is expected to be safer. Sodium ion batteries are also under development, they are cheaper and safer than Li-ion ones. Flow batteries are being researched as they have the very high capacity for load levelling applications.
Many new technologies and commercial models in renewable energy, transportation and electronics are banking on the growth of batteries. The pace of growth of battery technologies holds the key to the advertised benefits for these to actual materializes.
