Natural gas – the future of sustainable power generation

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To overcome the disruptive and costly impact of load shedding, South African business operations are being placed under increasing pressure to adopt more reliable sources of power. Although diesel generator sets (gensets) are most commonly-used, the cost of diesel fuel for continuous use makes diesel power generation very costly.

Natural gas powered gensets, available locally through Cummins, are a more sustainable solution to industry- standard diesel. Natural gas is a methane-rich, naturally-occurring gas found on-shore or off-shore. It is more cost-effective than other alternative energy sources such as wind and solar power.

Cummins Africa Power Generation Director Kenny Gaynor states that the main mechanical difference between the two genset options lies in the ignition.

“A natural gas genset uses spark ignition to start, while a diesel genset uses a compression ignition, which achieves ignition by placing the fuel mixture under pressure.”

Although the capital cost of a natural gas genset can be up to two that of a diesel one, Gaynor points out that the operational cost is substantially lower over a five to ten-year period. “While the upfront cost is considerably higher, the financing costs of the higher capital expenditure amount is small in comparison to that of the operating costs with diesel fuel, which is more expensive and prone to more cost fluctuations than natural gas.”

This ultimately results in a significantly lower kilowatt-hour (kWh) cost, when compared to diesel. An added benefit of natural gas gensets is waste heat recovery, a process whereby generated heat can be recycled and reused for industrial processes and temperature conversion. “Waste heat as high as 500oC can be reused for a number of processes such as boilers for laundry operations in a hospital or any other process that requires heat. Furthermore, the heat can be trapped and converted for use in air conditioning and cooling for data centres andoffice space. The major advantage of waste heat recovery is becoming more energy-efficient,” Gaynor explains.

Despite the advantages of natural gas, Gaynor admits that the gensets are not ideally-suited to provide instantaneous back-up power. “In the event of a power failure, a standard diesel genset would kick in approximately 10 to 12 seconds after the power cut. A natural gas genset can take up to 50 seconds to pick up the required load. In this timeframe, power would be completely lost, and production would have to be entirely restarted, resulting in delays.” Alternative equipment can though be used to bridge the supply take-up gap.

The Cummins range of natural gas gensets are designed and manufactured according to the highest quality standards at various plants around the globe. Says Gaynor, the natural gensets have been available in the local African market for a number of years and Cummins product and solutions have been well-received.

“Industries have come to the realisation that natural gas is a sustainable source of power generation. This type of technology is, however, still in its infancy stages – with natural gas accounting for around four percent of power generation in Africa, compared to the international average of 21%,” he adds.

Gaynor attributes this to the fact that natural gas is not as freely available in Africa, due to pipeline infrastructure constraints. In South Africa, for example, most of the existing natural gas pipeline infrastructure was built over 30 years ago, with little investment being spent in upgrades and new infrastructure.

Mozambique boasts abundant natural gas reserves, however there is only one privately-owned pipeline that limits regional supply. Gaynor believes that investment should be placed into a second pipeline.

“Natural gas supply to South Africa needs to increase from a wholesale point-of-view, while old regional infrastructure is replaced.”

Gaynor indicates that the natural gas markets in Nigeria and Tanzania are experiencing steady growth and, if more investment is placed in distributing this fuel locally, natural gas will become a more viable power generation option across the continent.

“Cummins has certainly experienced a considerable uptake in queries on natural gas gensets over the past two years. The interest in natural gas is there, it is now just a matter of making it more readily-available and cost-effective through infrastructure upgrades,” he concludes.