Energy storage systems have a key role to play in smoothing electricity consumption in South Africa because such systems can reduce peak demand, enable broader and more efficient use of alternative energy and renewable-energy systems, as well as enable more efficient use of existing capacity.
This is the view of several experts from the public and private sectors, who note that energy storage technologies have a role to play at residential, commercial, industrial and utility levels.
The profile of energy storage has risen markedly in recent months after Tesla, led by serial entrepreneur Elon Musk, unveiled its Powerwall home battery solution. But energy storage is a far broader subject, incorporating various solutions, from pumped storage and concentrated solar power to battery technologies.
In addition, experts stress that consideration also needs to be given to managing the electricity grid in an increasingly complex and heterogeneous energy ecosystem.
In fact, Council for Scientific and Industrial Research materials science and manufacturing energy materials manager Dr Mkhulu Mathe stresses that there are a number of components to potentially unlocking energy storage and ensuring it plays its role in stabilising and strengthening the network.
“Key considerations to unlock the complexity of the topic are the applications of energy storage systems and the functions that each would fulfil. Significantly, these link directly to the accessibility of energy in these storage systems – how fast the energy can be recovered from the storage medium and how fast it can be charged.”
For example, utility-scale energy storage systems, typically pumped-storage schemes, which are hydromechanical storage systems, can be used to manage power over hours and even days. However, residential and commercial systems – comprising, for example, redox flow, lithium-ion and advanced lead acid batteries, as well as super capacitors – must be able to provide energy within a much shorter time- frame, such as minutes or seconds, he explains.
Worldwide, the percentage of energy that can be stored is only 1% of energy generated, of which 98% is through pumped-storage hydro- electricity, according to the January 2015 edition of scientific journal Nature Chemistry.
Energy storage systems will be necessary to enable sustainable power networks linking variable and diverse generation capacity, including regional power trading. Thus, the generation, storage and dispatch of energy are key to enabling this, says Mathe.
South African National Energy Development Institute (Sanedi) energy and mobility senior manager Carel Snyman notes that, with sufficient energy storage systems, the current gene- ration capacity of South Africa would meet its energy needs.
“It is peak consumption at specific times that is the main contributor to grid instability, specifically during the mornings and evenings, and managing these periods through energy storage systems, will enable more efficient use of existing and new generation, including variable generation such as renewable-energy generation systems.”
Further, energy storage systems can reduce wasted energy generated from nonvariable sources, for example, during the late nights and early mornings, as well as the absolute size of generation required to sustain the grid. Currently, peak demand drives demand to almost three times the average requirement of the grid, which highlights the significant importance and impact of load-shifting and peak-demand management.
“Once energy storage systems are used broadly enough, the aggregated size of their impact becomes significant for municipal or national grids,” says Snyman.
Similarly, sufficiently broadly used residential or commercial energy storage systems would collectively provide sufficient capacity for maintaining generation assets without the need for load-shedding, he highlights.
Further, the scale of various systems can have a broad collective impact on peak demand, reducing the need to build more generation capacity while enabling energy-intensive businesses, such as mining and manufacturing, to continue unaffected by peak demand periods.
Energy storage – as a significant component of the grid – would also enable more businesses, especially smaller businesses that cannot afford standalone generators or energy storage systems, to be connected to the grid without impacting on its stability. Such storage would also mitigate revenue lost because of load-shedding, Snyman adds.
South African lithium battery systems manufacturer Freedom Won cofounder Antony English notes that suitably structured tariffs with higher cost energy at peak times and low cost at off-peak times will provide a strong incentive and business case for individual energy users to install energy storage systems.
The company reports average return-on-investment horizons of between three and five years, while the energy storage systems have a life cycle of 15 to 20 years.
“By installing energy storage systems, electrical energy users will not only reduce the impact of load-shedding on their lives or businesses, but can also help stabilise the grid by using their stored energy during peak times. Combined with solar power, they will also reduce their electricity costs, even within the current framework of tariff structures,” he notes.
Research and Applications
Mathe notes that the maturity of the technology, specifically for utility-scale use, is important, as the maintenance, management and control of energy storage systems are critical to enable load-shifting, bulk power management, asset management and maintenance.
He says significant research is being done locally and abroad to define, typify and understand the uses, risks and benefits of various energy storage technologies. This will allow for accurately assessing energy storage systems’ capability to improve efficiencies, with due consideration to future adaptability of the systems, Mathe adds.
“Energy storage will complement the accelerated development of renewable energy in various forms, and providing highly detailed standards in line with the [South African National Standards] grid codes will enable storage to be used linked to renewable generation, which would be a key differentiator for the adoption and use of such systems,” says Mathe, referencing the Australian Clean Energy Council Energy Storage Roadmap, published in April.
Meanwhile, several utility-scale energy storage pilot programmes are being conducted in South Africa to determine their role and use. Snyman notes that several technologies are available that can be used to provide utility- scale energy storage, such as nickel-iron battery technologies, lead acid batteries (both of which are big and heavy, but potentially commercially viable) and sodium nickel chlorine battery technologies, originally conceptualised in South Africa.
However, managing a complex energy ecosystem will require a layer of communications to schedule and synchronise the charge or discharge of energy management systems at grid level – a smart grid, notes Snyman.
A smart grid will have to manage and compensate for the variability of the system, but the visibility of demand and the ability to communicate instructions to various automated components to manage demand, including automatically switching off household or commercial systems, will allow for much broader management of energy dispatching, consumption and grid stability, he explains.
English, however, notes that a smart grid is not necessary for energy storage technologies to significantly benefit end-users and the national grid, noting that automated time-of-use energy storage systems, linked directly to and incentivised by time-of-use tariff structures, can provide the aggregated scale required to reduce pressure on the grid.
“If you set up the energy storage system at your business, factory or home to charge only once the time-of-use electricity tariff is below a threshold, and then use the stored energy once the tariff rises above a threshold, there is no need for a smart grid to realise the benefits of saving money on electricity costs and commensurately reducing pressure on the grid,” he argues.
Meanwhile, Freedom Won reports significant demand for its lithium battery systems at a residential scale, between 5 kWh and 30 kWh, mainly linked to solar renewable generation capacity and at commercial scale, from 40 kWh to 80 kWh for smaller businesses and from 150 kWh to 200 kWh for larger businesses.
English notes that the company has also received requests to provide quotes for much larger systems, such as factory-scale energy storage systems ranging from 500 kWh to 4 000 kWh.
“Our calculations, which rely on information we sourced from various industry surveys, indicate that the energy storage market will grow by about 50% a year, which indicates significant demand and potential for our energy storage technology.”
Advanced energy storage solutions such as the lithium-based batteries as produced by Freedom Won, are becoming increasingly commercially attractive, as they compete well against grid energy costs and outperform on-site generators and lead acid batteries in terms of total cost of ownership.
Mathe notes that, while a heterogeneous energy system represents risks, there are also significant drivers, such as reducing the requirement to wheel energy across electricity networks by enabling greater generation close to points of consumption.
However, Mathe and English concur that grid independence should not be the end goal for energy storage and distributed generation systems, but rather that these technologies should enable more efficient use of energy generation and different forms of energy generation to be added to the grid without destabilising it or impacting on existing energy generation companies, public and private.