Cement production is energy intensive and highly sensitive to power interruptions. Kilns operate continuously, and sudden shutdowns disrupt production and increase costs. In many African markets, however, limited access to grid power and volatile energy prices leave many cement producers with no other choices but to invest in power generation capabilities on site.

In this context, the question facing the cement industry is no longer whether to generate their own power, they often must, but which technology provides the most practical and resilient solution to do so.

The technological options typically envisaged include open-cycle gas turbines, reciprocating gas engines and sometimes even coal-fired steam turbines. But only one of these technologies offers the optimal balance of flexibility, reliability and affordability suited to highly demanding cement operations.

Flexibility in matching industrial power demand

An essential factor to take into consideration when assessing options is the way power demand fluctuates within cement plants. Although production processes often run continuously, electricity demand varies depending on grinding operations, maintenance cycles and seasonal production patterns.

By design, engine power plants are highly effective at adapting to these changing demand profiles since plant operators can simply change power output from each engine between 10% and 100% within minutes. Because they are composed of multiple engines operating in parallel, independent units can even be switched on or off to match real-time demand.

More importantly, flexible engines can operate stably at very low loads while maintaining high efficiency, giving operators a responsive tool for managing fluctuating power requirements. This capability allows the power plant to maintain very high electrical efficiency across a wide range of output levels.

This operational flexibility is also of paramount importance to support the integration of intermittent renewable energy in microgrids. As the cement industry increasingly turns to solar and wind to lower their carbon emission footprint, matching them with flexible engine capacity will provide the critical dispatch dependability needed in hybrid power plant configurations.

Open-cycle gas turbines, on the other hand, significantly lose efficiency when operating below full capacity. For industrial users that rarely operate at a constant full load, this translates into higher long-term fuel consumption, offsetting the turbines’ lower up-front cost. In a sector where energy costs represent a significant share of operating expenses, differences in efficiency over time will outweigh any initial capital cost advantages.

Unlike engines that can be turned on and off multiple times during a day and require no minimum up and down time, turbines need to operate constantly to avoid thermal stresses and therefore increased maintenance costs. This lack of operational flexibility will significantly undermine the efficiency, but also severely limit the performance of renewables in hybrid microgrid configurations. 

Reliability and scalability as baseline requirements

For cement plants, electricity supply must be dependable above all else. Reciprocating engine power plants typically achieve availability rates over 98 percent, making them well suited to industrial environments where access to energy must always be dependable.

One reason for this reliability lies in the modular nature of engine-based plants. Unlike turbine power plants, their configuration allows individual units to be serviced without shutting down the entire plant. Servicing can be planned and carried out on site while the remaining engines continue to operate. Spare parts planning, local technical support and straightforward servicing procedures also help keep downtime to a minimum.

The modular structure of engine power plants also allows for new generation capacity to be expanded gradually. As cement plants increase production, additional generating units can be installed without redesigning the entire power system, whilst avoiding the need for oversized plants. This structural flexibility reduces investment risk, allowing power infrastructure to grow alongside industrial demand.

In this regard, engine power plants offer a degree of adaptability that is difficult to achieve with other generation technologies.

Coal, a cheap option with considerable downsides

Coal-fired power plants are sometimes considered as an alternative for captive power in certain countries, particularly where cheap coal resources are locally available. However, coal-based generation presents its own set of challenges for industrial users.

Much like open-cycle gas turbines, coal plants are designed primarily for steady, continuous operation and are less suited to environments where power output must adjust frequently and rapidly. Startup times can extend to many hours, and maintenance often requires large sections of the plant to be taken offline. This lack of flexibility negatively impacts project economics.

Environmental considerations also represent a major downside for coal. Financing institutions, investors and owners are paying closer attention to emissions profiles and long-term climate risks. As a result, coal-based power plants can encounter significant barriers to financing.

Preparing for an evolving energy landscape

Energy systems across Africa are evolving, with new gas infrastructure, renewable energy projects and volatile fuel markets reshaping the landscape. Industrial power solutions therefore need to be able to accommodate these transformations.

Of course, no single power technology is universally optimal. Yet, when, sustainability, scalability, reliability, operational flexibility and long-term efficiency are considered together, engine-based power plants present a compelling option for many cement producers across the continent.

By Krzysztof Lokaj, Africa Development Manager, Wärtsilä Energy