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Energy sources: the pros and cons

The perfect large-scale energy source does not exist, and all current power generation technologies have pros and cons.

In Africa, the biggest and longest established renewable energy source, hydroelectricity, is often seasonal or intermittent based on hydrology. Another downside of big hydro is the displacement of people by dam construction, and concerns about affecting water courses.

However, Africa has outstanding unused hydroelectric potential. Cahora Bassa in Mozambique has proven that large hydro is a very economic long-term source of electricity. Ethiopia will reap the rewards of its commitment to low cost hydroelectric power, but it also demonstrates the importance of political will in driving such projects. Grand Inga on the Congo River, at potentially 40 GW, may become Africa’s biggest hydro scheme one day, but the government of the host country, the Democratic Republic of the Congo, has a long way to go to convince potential financiers of its credibility.

Wind, while a relatively cost competitive and mature technology in its onshore incarnation, is a low density intermittent source of electricity. The prospect of flying wind power plants sounds futuristic, but may represent what’s in store for this technology.

Among the renewables, ocean energy has the advantage of good energy density, and the future may see the emergence of commercial scale options. Regions with geothermal potential have a viable option for power generation. Biogas and landfill gas have a role as distributed power generation options and to offset grid supply.

Solar photovoltaic (PV) has yet to convince it is the ideal grid connected option where cost effective alternatives exist. However, particularly taking into account large strides in cost competitiveness, PV is a great option for distributed power, and for offsetting grid use. Companies in South Africa’s agricultural sector have been undertaking PV projects to displace grid use. It is a viable option for partial displacement of expensive diesel generators. It is also ideal for rural electrification packages and for providing power in large sparsely populated countries with no significant grid infrastructure and lots of sunlight, such as the Saharan country of Mauritania.

In contrast, concentrated solar power (CSP) is a very good grid option, either hybridised or with sufficient storage on its own, but it has a long way to migrate down the cost curve before it can prove it is a viable large scale option.

Of the established base load options, modern nuclear energy is a statistically safe long-term, relatively low cost option, particularly when considered over extended plant lives. It has the highest capacity factor of any energy source. Emerging modular technology could increase nuclear energy’s viability for more distributed networks. The downside is the need for significant technical expertise, a lack of willingness by the private financial sector to provide direct finance and typically the necessity of state involvement (in South Africa it raises the spectre of Arms Deal type corruption).

Coal is the established mainstay of base load power in many countries, and the mine mouth large coal fired power station approach has worked admirably as the least cost alternative. Countries and regions that have suitable coal resources should use them. However, coal is now perceived as a dirty option, due to its emissions. Increasing global steam coal demand and the fact it is not an infinite resource impacts pricing and availability. On the plus side for coal, new plants are much more efficient than older technology and this progression moves newer coal fired generation down the emissions curve.

Gas can be the cheapest base load option, depending on the sources of the gas. As with coal, if local gas sources exist, using them to meet power demand makes sense. Unlike coal or nuclear power, gas is the natural fit for grid connected intermittent renewables, due to the ability of gas fired power stations to ramp up and down rapidly in response to changes in availability from those sources. In addition, factors such as the ability to build gas fired plants speedily and their lower carbon footprints have enhanced gas as a power source of choice.

Many gas sources have emerged or are emerging, ranging from shale gas to underground coal gasification, coal bed methane to gas flared from oil wells. However, gas resources can be more difficult to develop than other energy carriers because the necessary gas infrastructure often requires the same order of magnitude of investment as the electrical infrastructure. Nigeria’s experience can teach many lessons in this regard.

All of the options mentioned here have their benefits and should be considered. Affordable electricity access that will enhance economic growth is the key criterion for all countries in Africa.

By Antonio Ruffini, Editor, ESI Africa magazine