If you are in the energy sector and working on power plants, you may have come across the term “open cycle gas turbine”. While many of you understand the meaning, some may ask what the difference is between and open cycle gas turbine and a combined one.

Open-cycle gas turbines will appeal to energy infrastructure developers and could play a role in reducing the electricity shortages in Africa in the years to come. As we are currently using open cycle gas turbine at one of our flagship projects in Tanzania, the Kinyerezi 1 Extension Project, Mike Huth, our Projects Director gives some more insights on this technical term.

“Open cycle gas turbine systems can be defined as the turbine plant that is fired using liquid or gas fuel to rotate a generator to produce electricity. At Kinyerezi 1 Extension Project, we are using natural gas. The system at Kinyerezi 1 Extension Project is an open cycle system as opposed to combined cycle. The open cycle does not utilise extra heat recovery systems and steam turbines but releases the outlet exhaust heat into the atmosphere. Within the system we are installing there are chillers which cool the turbine inlet air which increases the density and therefore the efficiency and outlet power. The turbine and generator are enclosed in a soundproof enclosure to reduce noise levels.”

As for combined-cycle gas turbines, they are widely used for electricity generation from natural gas. The gas is burnt in a high-temperature gas turbine that is coupled to a generator. The exhaust gas from the turbine is used to raise steam, which is then fed to a conventional steam turbine and a further generator.

Open cycle gas turbines are relatively small assets that can take up less space than other technologies and are more efficient from an installation and operation perspective. In the current context of an African energy market, open cycle gas turbines can be a cleaner and/or cheaper technology to install and operate depending on whether they are being compared to other types of gas turbines and other fossil-fuel-based plants.

Open cycle gas turbines can be switched on and off quickly, meaning they can be deployed into the electricity grid at short notice to cover any shortfall in supply. This remains one of the biggest advantages of using this technology. Open cycle gas turbines also remain a good option for delivering back-up electricity into the grid and for generating on-site electricity, specifically in times where other promising clean technologies such as hydrogen are still cost-prohibitive and in their relative infancy.