The recently developed MARC-R steam turbine produces a constant supply of clean electricity for over 27,000 households
Any weaknesses of one technology are offset by the strengths of the other: Hybrid technology is the latest trend – not just in the automotive industry. A combined thermosolar and biomass power plant has started commercial operation in Les Borges Blanques in Spain for the first time. At the heart of the arrangement of Spanish partner companies, ABANTIA and COMSA EMTE lies a highly efficient MAN Diesel & Turbo SE (MDT) turbo generator train, in which the latest MARC-R steam turbine from the Hamburg site celebrates its premiere.
Built on an area equivalent to 100 soccer pitches (70 hectares), the power plant, which is capable of producing an electricity output of 25 megawatts (MW), feeds 22.5 megawatts into the national grid, not including the electricity it needs for its own use. This is enough to supply more than 27,000 Spanish households with environmentally friendly, renewable energy. MDT has designed and supplied not only the entire turbo generator but also the steam bypass and condensing systems.
The special feature of the hybrid power plant is the arrangement’s ability to operate continuously, whatever the weather. This dispenses with the need to use complex, expensive solar-energy storage techniques.
Installed on two fields, parabolic troughs track the sun’s position during the day, bundling the sun’s rays in their focal lines through which absorber tubes run. Circulating around the absorber tubes is a thermal fluid that is thereby heated to a temperature of 400 °C, and then conveyed to the power plant block. Whenever there is not enough direct sunlight or at night when there is none at all, the biomass block is used instead, where a boiler fueled by timber, agricultural waste, and energy-producing plants generates the steam. These natural fuels only emit as much carbon dioxide (CO2) into the atmosphere as they extracted previously when growing.
The heat recovered is then used in a steam generator in order to provide steam at a high pressure and temperature. It is the steam that drives the MARC-R high-pressure steam turbine. Once the steam pressure and temperature have dropped due to expansion, the steam is reheated, before being conveyed to the low-pressure steam turbine. This extracts almost all the usable energy from the steam before it is once more condensed into water in the condenser.
“The MARC-R is an interim heating turbine with two casings,” explains sales engineer Simon Radermacher. Constructed out of two repeatedly tried-and tested machines, a MARC 2 backpressure turbine and a MARC 6 condenser turbine, the MARC-R forms part of the MARC, short for Modular Arrangement Concept. “The construction increases thermodynamic efficiency, thereby enabling us to enhance the overall efficiency of the power plant considerably,” says Radermacher.
As a result, the arrangement achieves an annual saving of around 24,500 tons of the greenhouse gas CO2, which would have been released if fossil fuels had been used for generation. “Theoretically, any thermosolar power plant can be combined in this way,” according to Simon Radermacher. Hence the hybrid technology achieves precisely its aim, that is, ensuring operational stability by means of renewable energy sources: These are available permanently and do not fluctuate.
Once again MAN Diesel & Turbo is playing a leading role in the use of a technology that has been continually developed over decades of environmentally friendly applications. MAN steam turbines are proving their potential in the progress toward a decentralized electricity supply in many biomass power plants. A MAN 50-MW turbo generator in the nearby “Andasol 3” power plant situated in the town of Granada in southern Spain, operates reliably round the clock. Currently the largest power plant of this type in the world, “Shams 1” in Abu Dhabi, which achieves a 100-MW output, also trusts in MDT turbine technology.
The latest ABANTIA/COMSA EMTE order underlines MDT’s claim to be driving the turnaround in energy policy forward, by using cutting-edge technology. “The project had an extremely ambitious time schedule,” explains Christian Borelli, who supervised the construction and commissioning of the turbine train, and celebrated 25 years of working for MAN Diesel & Turbo this year. “It was on November 30 2012 that our MARC-R turbine powered the generator for the first time, which was then synchronized with the European network at 23:30, enabling its electricity output to be fed in,” he reports. “The resulting sense of jubilation and relief in the control room were such as I have rarely experienced in my professional career,” admits Borelli with a smile.