Energy storage: How far are we from a clean and green future

The world demands more power, preferably in a frame that’s clean and renewable. Our energy storage maneuverings are currently shaped by lithium-ion batteries, which unquestionably fall short for some applications, what can we look forward to in years to come?

 Let’s begin with some battery basics. A battery is an energy storing device with pack of multiple cells, each cell has a cathode (positive electrode), an anode (negative electrode), a separator, and an electrolyte. Using different chemistry outcomes and materials affects the properties of the battery – the amount of energy it can store and output, power it can provide, or the number of times it can be discharged and recharged (also called cycling capacity).

Scientists around the world are working on multiple energy storage technologies that could one day meet the energy requirements of mega-cities at just one tap. Here are some cutting edge discoveries involving diamond, radioactive materials, and organic molecules.

Diamond-based Nuclear Batteries: Newer and better approach towards energy storage

Researchers have been working on ways to turn radioactive material into an electric current that lasts for years. These batteries, called nuclear batteries, work on a principle called betavoltaics and they are powered by beta decay of radioactive material. Beta particles are just high energy electrons and setting up beta emitting material next to a semiconductor is theoretically meets the requirements to get an electric current in motion.

These batteries have power outputs in very low ranges but they last until the material completely decays. Radioactive materials are known to have half-lives of centuries to millennia and this is what makes these batteries last for decades without any significant power loss.

Betavoltaic are different from the Radioisotope Thermoelectric Generators (RTGs) used by NASA for space missions. RTGs are powered by the heat of radioactive materials like plutonium instead of beta particles directly and are sometimes referred to as Nuclear Batteries. But Beta Voltaics promises a greater lifetime than so-called nuclear batteries. The first betavoltaic battery was developed by the Radio Corporation of America, in 1954, when it was considered a big leap in energy solutions. RCA imagined them being used in a wristwatch, hearing aids, and radios.

A magazine from 1954 mentioned this invention as revolutionary for energy storage and compared to that of the light bulb by Edison. While light bulbs are everywhere but a device running on an atomic battery is rarely found in general use.

Today betavoltaics have found main applications in deep space explorations and military affairs which is nowhere close to average consumers. Multiple factors are responsible for the non-ubiquity of these batteries but the major one is safety. Apparently, betavoltaics is safer than other nuclear power systems, but some materials can prove to be a serious threat, RC’s prototype from 1954, for instance, needed Strontium-90, exposure to which causes Leukemia.

Coating the battery with radiation blocking materials was not enough to hand off to markets and consumers. Nevertheless, in recent years several research teams looking for a way to safely harness the power from radioactive materials. Scientists from the University of Bristol have discovered a promising method to harness this energy.

Unlike the majority of electricity-generation technologies, which use energy to move a magnet through a coil of wire to generate a current, the man-made diamond is able to produce a charge simply by being placed in close vicinity to a radioactive source. Researchers have come up with a new prototype based on Carbon-14, a naturally occurring radioisotope found in the atmosphere and all life forms. It is also a waste material from a nuclear power plant. Their aim is not only to dispose such waste but recycle it to produce energy.

Also, Carbon-14 is not really hazardous radioisotope as in other elements have a rapidly disintegrating nucleus. This team isolated Carbon-14 and carried out processes to synthesize diamonds. Now this diamond is radioactive and could produce an electric current. Batteries based on such radioactive diamond would not produce enough energy to charge phones but enough to power smoke detectors, emergency signs, IoT Devices, jet engine sensors, deep-sea cable sensors and last for decades without being replaced. As diamond is very hard solid, the radiations are now wide-ranged and hence makes it safer.

Perhaps, the most impactful applications of this battery are for medical implants. Today we largely rely on Lithium-ion batteries, but those have limitations. The pacemakers installed after heart surgeries work on such batteries. With such innovation, we leap a step closer to a one-stop energy solution.

Vanadium Flow Batteries: Redefining ways of energy storage

Scientists aim at sustainably powering entire cities, and what makes us a step closer to making that happen is liquid-based redox flow batteries; capable of energy storage of lots and lots of kilowatts.

Innovations in energy sciences, these days, are so promising that harnessing energy from renewable sources like solar and wind power will be efficient and cheap. When It’s dark and not so windy, or the demand for power exceeds the output then we will have to return to the fossil fuels. What if we could store this energy in such a way that can be retrieved when needed in an efficient manner? Batteries seem to the solution to meet energy needs.

There are different battery types and all have their own strengths and weaknesses. The best battery type that might be capable of such efficiency is the one that uses flowing liquids called a redox flow battery. A redox flow battery is seen as a hybrid between a battery and a fuel cell. It consists of two tanks of an electrolyte: a positive and negative each. In between the tanks is a cell stack, where the positive and negative solutions are pumped and are separated by a membrane. Inside the cell stack, the ions in the negatively charged solution give up an electron, a process called oxidation.

Released electrons are picked up by an electrode in the cell stack that travels through the device connected to be charged before arriving another electrode on the other side of the membrane. Reduction takes place on the other side of the membrane where the ions in solution pick up the electrons. The positively charged hydrogen ions are set free and travel back across the membrane and maintain the charge balance. This is all that happens while some device is being run through such a battery, and the reverse of the above process takes place while charging.

But why is this technology being spoken when Lithium-ion batteries are here to run our small scale devices. Apparently, Li-ion batteries do not prove to be good for supplying power to the entire city and this is why redox flow batteries are trying to make its way for large energy needs. Lithium is not an abundant metal, so as to build a large battery. Other setbacks like degradation with time, and loss in capacity to hold charge also count for its inapplicability.

On the other hand, flow cell batteries have qualities that make them perfect for such large scale power storage. The scalability of such cells can be simply increased by using larger tanks of electrolytes. Degradation of the cell, in this case, is not as significant because the electrolyte can last for more than 5000 charge cycles. The only thing that is stopping us from using these is rise and sustainability. The most widely used metal used in flow batteries is Vanadium because it charges and discharges reliably for thousands of cycles. Again, Vanadium is not very abundant in the Earth’s crust and if these batteries come in the mainstream, the prices would reach the sky.

Researchers have tried replacing Vanadium with organic molecules, but those tend to decay and need replacement every few months. If the solutions in the cell used are very acidic or basic then it poses damage to the pumps and leads to hazards leaks. But scientists are undeterred can continue to find a solution until they found one. Recently, scientists at USC claim to have discovered organic water-based redox batteries that last for 15 years and costs one-tenth of a Li-ion battery. The battery that they have made is enough for the basic electricity demands of a single house, but their goal is to make electricity available at one tap for the entire mega-city.

One day in the near future we would see more promising discoveries playing a vital role in running green energy grids around the world.

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