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21 Jun 2022

Why it is essential to strengthen the flow of hydropower

Renewable energy, climate change, energy transition
Nasi Hako

Despite accounting for 17% of the world’s population, Africa only consumes 4% of global power, while in sub-Saharan Africa alone, 579 million people have no access to electricity. Meanwhile, hydropower technology is developing at a rate that affords Africa a unique opportunity to reduce energy scarcity on the continent significantly.

Hydropower is a renewable, versatile, low-cost source of clean electricity generation and remains Africa’s primary renewable energy source with over 38GW of installed capacity. According to the International Hydropower Association (IHA), this clean energy resource accounts for over 70% of the renewable electricity share in Africa and roughly 16% of the total electricity globally. 

Still, the hydropower capacity landscape in Africa is insignificant and should be developed, says Julian Hunt, a research scholar for the Sustainable Service Systems Research group of the International Institute for Applied Systems Analysis (IIASA) Energy, Climate and Environment Programme. “At the moment, only 10% of the viable capacity for hydropower is explored in Africa. While in the US, Europe and Japan, 60-80% of the available hydropower potential is explored,” said Hunt. 

With the increasing number of African countries pledging to participate in Africa’s just energy transition, this begs the question: why has hydropower not been dominating the conversation, given the continent’s clean energy transition aspirations? 

Africa’s significant untapped hydropower potential 

Hydropower is a renewable energy source wherein power is derived from the energy generated by moving water from higher to lower elevations. Hydropower offers significant potential for carbon emissions reductions while remaining a tried and tested, price-competitive, adjustable technology. Will Henley, the IHA spokesperson, told ESI Africa: “Although blessed with abundant water resources, the continent has significant untapped hydropower potential. Moreover, the global potential hydropower capacity is four times the current installed capacity.” 

"Though hydropower requires a high initial investment, this renewable energy source also has the lowest operations and maintenance costs".

Although this clean energy’s potential capacity is underexplored, many hydropower projects are underway throughout the African continent. These projects aim to generate hydroelectricity and manage water distribution supply to meet future energy and water demands. Examples include the Grand Ethiopian Renaissance Dam, which will generate an estimated 6,450MW annually upon completion. Another is the Aswan High Dam in southern Egypt, which has a total generation capacity of 2,100MW. 

In Southern Africa, the Cahora Basa Dam in Mozambique has a combined capacity of 2,070MW and is the largest, while hundreds of small hydropower plants spread across the continent. There is the Souapiti Hydropower Station on the Konkoure River in Guinea where two units (225MW out of 450MW) became operational in November 2020.

Another is 750MW Kafue Gorge Lower hydropower project in Zambia. According to Henley, hydropower’s share of total electricity is predicted to increase to more than 23% by 2040. So as Africa’s energy demand grows twice as fast as the global average and governments look to achieve universal electricity access and a low carbon energy transition, Africa has an opportunity to adopt the latest renewable energy technologies and secure a clean energy future. 

Beyond generating electricity 

Besides being a zero-emissions renewable energy source, hydropower has many practical advantages. From a financial standpoint, hydropower is the cheapest source of electricity, costing $0.05 per kilowatt-hour on average. It also has around 90% energy conversion efficiency from water to wire, making it a sustainable choice for long-term generation. Though it requires a high initial investment, the renewable energy source also has the lowest operations and maintenance costs.

The construction of dams and hydropower plants creates thousands of jobs, contributing to GDP and overall economic growth. It creates opportunities for sustainable development, brings valuable investment in infrastructure to the countryside, increases land value in the continent’s interior, and improves the value of the land surrounding its reservoir. These reservoirs can enhance the area’s fauna and flora, cultivate fishing sports and fish farming, and be promoted as entertainment spots. “Beyond generating electricity, hydropower provides countries in Africa with vital infrastructure to manage freshwater supplies for agriculture, businesses and communities. Multipurpose hydropower facilities can be used to supply drinking water, irrigate farmland and improve waterways navigation,” said Henley. 

"Hydropower technology is evolving, and new solutions are being researched and tested to address the negative impacts of hydropower".

With extreme weather events growing in frequency, floods and droughts risk becoming an increasing threat to livelihoods across Africa. Henley recommends that there is all the more reason to carefully manage water supplies and invest in the storage reservoirs and flood defences that hydropower provides. “Hydropower is an all-around win-win solution for the economy, society and the environment,” added Hunt. 

Unfortunately, hydropower adoption has been a source of great debate as these facilities can cause environmental and social problems. For example, dams and reservoirs can reduce river flows, raise the water temperature, degrade water quality, hinder fish migration and cause sediment build-up, negatively impacting wildlife. 

However, hydropower technology is evolving, and new solutions are being researched and tested to address these hydropower setbacks. Therefore, Africa as a continent has the potential to utilise and capitalise on hydropower potential. With the help of further investment and governmental dedication, the continent’s water-rich countries can boost their economic growth and sustainable development by adopting hydroelectric projects. 

Hydropower technology is evolving

ESI Africa reached out to Emanuele Quaranta, a hydropower scientist of the European Commission, who says that new hydropower technologies can improve sustainability, flexibility and efficiency under different operating conditions. Recent technological innovations can reduce operational costs, improve environmental impacts, and maximise hydropower facilities’ effectiveness. 

Recently, there have been advancements to explore efficient tunnelling techniques, variable speed generation technology, more environmentally friendly technology and silt erosion resistive materials. However, some technological developments have proved more salient in escalating hydropower flexibility than others, such as stabiliser fins. This innovative technology is adjustable diaphragms that allow adaptability of the water flow and the opportunity to increase the operating range. 

The evolvement of technology has also seen the exploration of tools that allow hydropower turbines to operate outside of their design point. For example, the Francis turbine has previously been dubbed the most popular hydraulic turbine, given that it has the most comprehensive application range in terms of head and flow. This popularity is especially in comparison to the Pelton turbine, which needs a high head and a low flow rate, or the Kaplan turbine, which requires a high flow rate and low head.

However, according to Quaranta, the Francis turbine has only one regulation, the guide vane opening, which operates in such a way that its efficiency goes down when it operates outside of the design point. “Therefore, several improvements have been made to enhance the Francis turbine efficiency outside its design point. For example, the Deriaz turbine and X-blade turbine, and their variable rotational speed,” added Quaranta. 

Still, hydropower experts agree that energy storage mechanisms aim to compensate for the increase of variable renewable energy sources in power systems – the most talked about being pumped hydropower storage (PHS), which works like a giant battery. [Ed – read more on pumped storage hydropower in ESI Africa Issue 2 2021 on pages 50 & 51] PHS facilities store the electricity generated by other power sources, like solar, wind, and nuclear, for later use. These facilities store energy by pumping water from a reservoir at a lower elevation to a reservoir at a higher elevation. 

This technique is an especially useful tool in acquiring energy security as water is released back into the lower reservoir during periods of high electrical demand to generate electricity. While, after peeking demand, the remaining water is used to generate power to pump the bulk back to the top reservoir. It’s the perfect closed storage cycle. 

“We need storage capacity to compensate for the variability of the energy demand and the variability of wind and solar power, and we need to stabilise the electric grid. Pumped storage hydropower is the technology that allows this. This can store energy and water more efficiently than batteries on a larger scale in terms of GW of energy stored, and flexibility that can provide, and with longer lifespan,” said Quaranta. 

Similarly, Hunt agrees that, as opposed to an Impoundment facility which can alter water quality or a Run-of-River facility, which reduces river flow, PHS is the most efficient. “Storing water with seasonal pumped storage to regulate the river’s flow can require 10 to 100 times less land to store the same volume of water and reduce evaporation by 10 to 100 times,” explains Hunt. 

Hydropower’s biggest threat 

According to Hunt, the biggest threat to the hydropower sector remains the risk brought forth by climate change and the lack of cohesive literature on the politics that drive, constrain, and shape renewable energy generation and policy. Even the recent unravelling of the conflict between Russia and Ukraine has highlighted the vulnerability of oil and gas imports and exports, which hydropower facilities could have supported. 

“Climate change poses risks to all energy technologies, even renewables. In the hydropower sector, proposed and pre-existing projects must be developed and operated according to IHA’s Hydropower Sector Climate Resilience Guidelines to plan for all eventualities. At last year’s United Nations climate change conference, COP26, governments committed to ‘phase down’ coal and accelerate the shift towards renewables. The world is turning the page on coal-fired electricity generation. So, this provides a new opening for renewables like hydropower, wind and solar to fill the hole left by coal,” added Henley. 

“Frankly, however, we haven’t seen enough progress by governments since then… The IHA calls for urgent investment in sustainable hydropower to combat climate change, accelerate progress towards net zero and strengthen energy security. Commitments now need to be translated into policies, investments and tangible action ahead of COP27 in Egypt later this year,” he concludes. 

Meanwhile, the collection and processing of data to adjust the working conditions of hydropower turbines can provide advanced grid supporting services without compromising stations’ reliability and safety. According to Quaranta, it is estimated that a total 42TWh could be added to present hydro energy production by implementing hydropower digitalisation. Such an increase could lead to annual operational savings of $5 billion and a significant reduction in greenhouse gas emissions. 


This blog is authored by Nasi Hako, Editorial Assistant at ESI Africa. It is originally published on ESI Africa

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