Rising energy prices and stricter environmental regulations are also the drivers of innovation in the electricity generation sector. As a provider of turnkey diesel power plants, MAN Diesel & Turbo is focusing not just on achieving the highest possible degree of efficiency for its engines, but also has the cost-effectiveness of the entire power plant in mind. For our customers, we seek out the best, most practicable and most economical solutions. The Diesel Combined Cycle, as it is known, is playing an increasingly important role in this.
In a diesel power plant, large-bore diesel engines generate mechanical energy that is converted into electricity by generators. When fuel is burned, however, it always generates heat, which can also be used. This waste heat is used to generate steam, which in turn powers a steam turbine. This way, the overall level of efficiency of the system can be increased significantly. In the Diesel Combined Cycle, this principle has been perfected and increases the amount of electricity generated by a power plant by up to ten per cent – with the same low amount of fuel being used. By doing this, we are improving the CO2 balance sheet of diesel power plants and also creating economic benefits for our customers. Economic and ecological interests are therefore running in the same direction thanks to this technology.
To achieve this, the Diesel Combined Cycle uses two steam drums at a different pressure level. Instead of the usual small self-consumption steam generator that previously only provided the heat energy to pre-warm the fuels, a comparatively large waste-heat heating vessel is now used.
In the first stage, it generates particularly hot steam at up to 350 degrees Celsius, with a high pressure of 20 to 25 bar. In a second stage, a further proportion of the residual heat energy is used to generate low-pressure steam at around 8 bar and a temperature of 260 degrees Celsius. This high- and low-pressure steam is fed into an optimised, multi-stage MAN steam turbine that generates up to 10 per cent additional electricity. A small proportion of steam is diverted from the low-pressure stage for the heating of the fuel – a process required for heavy fuel oil.
Two MAN power plants in Pakistan have already been equipped with this system. The higher investment costs for the Diesel Combined Cycle are recouped relatively quickly. Based on a heavy fuel oil price of around Euro 300 per tonne, savings of around Euro 1,000 per operating hour can be achieved.
The Diesel Combined Cycle is one of the product packages that we have put together for our customers in the context of the merger to MAN Diesel & Turbo SE – with diesel engines from MAN Diesel and steam turbines from MAN Turbo.