Energy storage conundrum

It wasn’t long ago that renewable energy technology was unrealistically expensive for people living in Africa, but things are changing quickly

Anton Eberhard, from the University of Cape Town, concurs stating: “Energy from independent power producers (IPPs) used to be the most expensive way to increase capacity. However, over the last five years, renewable-energy technology has come down 80 percent in price.

“Now, some of the renewable-energy projects currently on the go in South Africa will produce energy at some of the lowest rates in the world.”

Christoph Frei of the World Energy Council Switzerland goes on to explain that, due to the decreasing cost of renewable energy technology, larger renewable-energy plants have been able to produce energy at two cents (United States dollar) per kWh over the past 18 months.

Addressing the shortfall

However, critics of renewable energy are quick to point out that the technology can be unreliable. This is complicated by the fact that, once produced, energy cannot be easily stored and must be used immediately or be lost forever.

While it’s true that there are limited hours of sunshine and the wind doesn’t always blow, there are several ways of overcoming this shortfall in the technology. The preferred method is to pair renewable-energy systems with energy storage. This enables energy to be stored in times of excess capacity and used later on when the wind slows down, or there is no sun.

In the European Union, where renewable energy has been deployed at a much faster rate, an integrated smart grid has been set up. This means that if there is no wind or sunshine in, say, Germany, utilities there can communicate with, and trade energy with another country in Europe that has excess capacity.

Another way to overcome this inherent “unreliability” is to pair the renewable-energy system with a more traditional power-generation method. For example, power from the grid may be used, or a diesel generator can be incorporated to act as a substitute, when there is a lack of renewable energy available.

Battery technology

While still expensive, the cost of energy storage will eventually come down. A report released by the International Renewable Energy Agency (IRENA) stated that the cost of battery storage for stationary applications could fall by up to 66 percent by 2030. This has made the economics of energy storage more appealing to investors, grid operators, utilities and end-users.

Research into safer, more reliable and cost-effective energy-storage solutions is ongoing. Some of this research is being undertaken locally. For example, a company called Bushveld Energy is in the process of manufacturing and testing the effectiveness of vanadium redox flow batteries (VRFB) locally.

The company explains that the technology combines the performance advantages of flow batteries with the simplicity of using just one natural element – vanadium.

Unlike prominent solid-state batteries, such as lead-acid and lithium-ion, flow batteries use a liquid electrolyte to store energy. This allows for near unlimited recharging (cycling), easy scaling by just adding more electrolyte and negligible performance deterioration over long periods of time.

Other advantages of vanadium, in particular, lie in its ability to exist in four different oxidation states and its water-solubility, allowing for a simpler battery with fewer inputs and no toxic elements. As a result, flow batteries may one day provide the most cost-effective means to store energy for daily energy storage of a few hours.

Sustainable energy

According to the United Nations, sustainable energy is defined as: “meeting the needs of the present without compromising the ability of future generations to meet their own needs”.

In South Africa, coal-fired power stations are responsible for 90 percent of power generation. Eskom, with its coal-fired power plants, is the biggest emitter of carbon emissions in Africa and contributes toward 80 percent of the carbon emissions in South Africa.

At the same time, it wasn’t long ago that South Africa begun building two of the largest coal-fired power stations in the world – Medupi and Kusile. The loans for these plants are still being paid off and, when construction has been completed, the energy coming from them will remain crucial to the economy of South Africa.

In addition, we have a number of open-cycle diesel generators, which are needed in times of peak demand.  This situation does, however, place future generations at risk as the effects of climate change become ever more apparent.

This signifies the need for cleaner technologies based on existing infrastructure and there are a number of programmes ongoing.

In South Africa, a company by the name of Clean Coal Technologies (CCT) is in the process of commercialising technology based on the Fisher Tröpsch method.

Today, the joint venture between South African and Chinese experts is at the forefront of providing viable and more environmentally friendly coal-to-liquids technology.

CCT technology can be applied to gas-to-liquid, coal-to-liquid and well as a new combined feed process. Overall, the technology offers utilities the opportunity to reduce CO₂ emissions, reduce capital outlay and lower operating expenses.

In conclusion, energy-storage technologies are viewed as the final stumbling block standing in the way of the acceptance of renewable-energy generation throughout Africa.

Reliable energy storage will facilitate the management of renewable power intermittency, demand-response services and the distribution of stable, clean and sustainable power into local or regional grids.