Increasingly, more people are accepting that we desperately need more climate-conscious ways to generate and store electricity. Wind turbines and various solar-power systems have become popular, affordable and accessible. But because they do not produce electricity constantly, they need to be linked to some kind of battery to store power for use when the system is not generating.

‘Battery’ can be a confusing term in this context. Yes, the chemical batteries we use in our cars, home solar-power systems and wireless devices are part of this definition, and a lot of research and development are being devoted to improving the capacity and usable life of chemical batteries, while at the same time reducing the environmental harm caused by their manufacture and disposal. Many have yet to advance beyond the prototype stage, but there are promising developments in chemical batteries using metals like sodium, zinc, manganese and iron instead of lithium, as well as more complex synthesised materials.

But there are also several other types of batteries – or energy storage technologies – that exist already and are undergoing intensive research and development. The entire sector offers both individual and business investors the chance to invest in green technologies with the potential for sustained long-term growth. In this blog, we’ll explore some of the most promising energy storage options.
  

Green hydrogen

Green hydrogen is efficient and 100% sustainable. Hydrogen is a light, highly reactive gas that can produce electricity in hydrogen fuel cells and emit nothing but pure water. It’s the most abundant chemical element in nature and easy to harvest from seawater by electrolysis – global demand for the gas as an energy source has tripled since 1975.

Hydrogen offers several advantages. It is 100 % sustainable and does not emit pollutants during production or combustion. Hydrogen can be stored for use when needed, and it’s versatile – it can be used as a gas to generate electricity or converted to synthetic liquid fuels for internal-combustion engines.

Hydrogen also has some disadvantages, however. It is currently expensive to obtain and so is the technology that it fuels. The production of hydrogen in general – and green hydrogen in particular – requires more energy than other fuels right now. And because hydrogen is highly volatile and flammable, extensive safety measures are required to prevent leakage and explosions. However, as with solar photovoltaic (PV) panels, further development in the technologies to harvest and use hydrogen, as well as increased early-adopter uptake, could reduce the costs and drawbacks steadily.

Despite the challenges, hydrogen is already used in many countries for applications such as electricity generation and energy storage in tanks. These are lighter and thus easier to handle than lithium-ion batteries.
  

Gravity batteries

This new field of energy storage technology relies on gravity. When green energy is plentiful, it is used to haul a colossal weight to a predetermined height. When renewables are limited, the load is released, geared to descend very slowly under gravity while turning a generator much faster. Engineers developing the technology are focusing their attention on decommissioned mine shafts deep enough to house a full-sized gravity battery installation – about 300m.

A subterranean prototype should be functioning by 2024 in Europe. While South Africa has plenty of disused mine sites, one of the challenges of using mine shafts for this technology is constructing a superstructure that can support several thousand tonnes of weight without collapsing the shaft.

Other developments in the field are above ground, with prototype buildings in Europe standing 20 storeys tall. In one such prototype, when green power supply exceeds demand, AI-controlled cranes lift a pair of 30-tonne blocks upwards. When demand outstrips supply, the blocks go back down, generating enough energy for thousands of homes. Storage capacity of 100MWh in these installations can power around 25,000 homes for a day.

Gravity batteries have significant advantages for large-scale energy storage over more popular, more cost-effective (for now) conventional battery types like lithium-ion. Building bigger chemical batteries of this kind increases the lifetime cost of the system – from the cost of mining lithium or other elements for new chemical battery types, to the cost of disposing of used batteries without harming the environment. Gravity batteries, on the other hand, are entirely mechanical – so unlike chemical batteries, they don’t lose their ability to be recharged over time. Breakdowns are their most serious threat, but individual components can be replaced. Gravity batteries could last as long as 50 years, and they have no negative environmental consequences.
  

Pumped-storage hydroelectricity

This technology uses the gravitational potential energy of water, pumped from storage at a lower level to a reservoir at a higher elevation. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Pumped-storage hydroelectricity (PSH) allows you to store excess solar and wind energy for periods of higher demand. The reservoirs used are quite small, compared to conventional hydroelectric dams of similar power, and generating periods are often less than half a day. PSH has the largest capacity of any sustainable grid-energy solution available, accounting for around 95% of all active tracked storage installations worldwide.

The main disadvantage of PSH is that it can only be constructed on a site that combines both geographical height changes and water availability. Suitable sites are likely to be in hilly or mountainous regions, potentially in areas of natural beauty, so PSH is susceptible to social and ecological objections.

Capital costs for pumped-storage plants are relatively high, although this is somewhat mitigated by their proven long service life of decades: about 3 to 5 times longer than utility-scale batteries. Small or micro applications for pumped storage could be built on streams and within infrastructures like a stormwater basin.

These are just 3 of the energy storage alternatives currently being researched and improved all the time. Vast reserves of human innovation are being applied to this sector as the world finally wakes up to the climate crisis and our need to wean our societies off fossil fuels, so we can probably expect even more ingenious solutions to arise in the future. When we look back in 50 years, our current cutting-edge energy solutions might look as old-fashioned as vinyl records do to a generation raised on music streamed through their cellphones.

Nedbank has already demonstrated our firm commitment to funding green initiatives. It’s a sector well worth exploring for long-term investment options – whether you simply want to buy shares in renewable-energy and energy-storage operations that look set for sustained growth, or you want to make a significant capital investment and launch your own renewable-energy or energy storage start-up.