MORE EFFICIENCY, LOWER EMISSIONS

In Europe, energy efficiency is supposed to increase by 27% and CO₂ emissions to decrease by 40% by 2030. To reach these ambitious goals, Germany must work hard and is counting on highly efficient technologies.

Only three months after the celebrated and acclaimed Paris Climate Agreement, German climate protectors received bad news: CO₂ emissions in Germany had once again increased in 2015. High electricity exports, cold weather and lower fuel costs had once again caused more greenhouse gases to reach the atmosphere. 

Germany’s energy policy, thus, is facing a dilemma. Since the turn of the century, Germany has pushed for a low-carbon energy environment. Renewable energies as part of current electricity consumption have doubled since 2010. By now they account for nearly 33%. In the same time frame, CO₂ emissions only decreased by 4%. That is a big challenge for Germany. By 2020, emissions are supposed to decrease by 40% in comparison with 1990. However, so far they have only decreased by about 27%. The energy efficiency goals are a long way off. 

That is why the federal government is working on new concepts. One key scenario is the exit from coal power. Especially older plants with low efficiencies are supposed be taken off the grid in a timely fashion. But that is not enough. “If we want to reach the previously set climate protection goals, we have to reach climate neutrality by the middle of the century.

Fossil fuels producing high emissions, like coal, can no longer be used for power generation in this scenario,” says Matthias Zelinger, speaker for energy policy of the Verband Deutscher Maschinen- und Anlagenbau (VDMA). A scenario that seems quite drastic given that coal still accounts for 40% of the German power-generation mix. 

WHO WILL CLOSE THE POWER-GENERATION GAP?

Renewable energies alone cannot replace the large amount of coal-generated power. Wind turbines and solar panels only produce when the wind is blowing or the sun is shining, respectively. That means that, in the future, power stations are needed that can generate electricity instantly and are able to balance out fluctuations in renewable energies. “We will need flexible gas power plants for the foreseeable future as complementary technology supplemented by storage and demand management,” says energy expert Matthias Zelinger. “These power plants have to have the midterm potential to be operable with greenhouse-gas-neutral fuels.” That means that fuel sources will shift more toward renewables and gas. 

CHP (combined heat and power) is an important building block for Sigmar Gabriel, Germany’s Minister for Economic Affairs and Technology. He calls it an important “efficiency technology.” CHP plants generate electricity and heat at the same time and utilize the respective fuels optimally.

“We can reach overall efficiency factors of up to 95%,” says Tilman Tütken, Vice President MAN Diesel & Turbo and European sales manager for the power plant division. The share of CHP in German electricity generation is supposed to increase to 18% by 2020. Additional motivation may come from the EU’s goals to increase efficiency. 

Which means Germany would be catching up to the leaders in Europe when it comes to CHP utilization. Denmark is ahead of the pack, having already reached the highest development standard, with more than 50%. 

OVERALL EFFICIENCY FACTOR UP TO 95%

The German government aims to replace coal fired plants with gas fired cogeneration technologies that are low in CO₂ emissions. This is an area where MAN can draw on considerable experience. Early in 2016 the corporation equipped a CHP power plant with four gas turbines of the MGT series for the SAIC Volkswagen Automotive Company Ltd (SVW) in Shanghai. Each of the four turbines not only delivers electrical energy, but also enables the use of waste heat for the production of process steam. This way the power plant reaches an overall efficiency factor of over 80%. “The inauguration of this cogeneration system is a milestone for our automobile production in China. The plant delivers steam and electricity for our Car Plant 3 here at SAIC Volkswagen and replaces all coal fired plants. That means an annual reduction in CO₂ emissions by 59,000 metric tons,” explains Prof. Dr. Jochen Heizmann, president and CEO of the Volkswagen Group China. 

As early as 2014, MAN Diesel & Turbo put a gas engine power plant into operation at the VW location in Braunschweig, Germany. This allows the car manufacturer to generate highly efficient heat and power and emits 30,000 metric tons less CO₂ per year. Even greater savings will be achieved by the energy provider EnBW with their combined heat and power 30 megawatt gas engine plant. The gas engine power plant that is currently planned for a Stuttgart Gaisburg location will take the place of a primarily coal fired plant to generate district heat and will thereby reduce CO₂ emissions by up to 60,000 metric tons per year. 

ENGINE OR TURBINE

Gas engine power plants are still a fairly young technology in European markets compared with the well established and widespread CHP facilities powered by gas turbines. “After the Energiewende,” the German turnaround in energy policy, “and increasing renewable energy generation, gas engine technology is just starting to gain ground,” explains Tütken. The big advantage is the flexibility. MAN’s engine power plants are built based on a modular system that is scalable from seven megawatts to any desired size.

This modular building method allows for the load-based addition or removal of individual power units. Engines can reach their full performance within only minutes. “That is a factor that makes gas engine power plants highly flexible.

And this flexibility is necessary when the future generation of renewable energy in the power grid grows and the required remaining residual energy fluctuates,” describes Tütken. Cogeneration plants allow customers to respond quickly to price signals from the market. “With these engines it is worth revving up the plant for 15 minutes when the prices are high,” explains Tütken. This allows for revenues in the area of balancing energy, which serves as a reserve and compensates for power grid fluctuations. 

Are gas engines the superior technology? Tütken does not want to leave this as a blanket statement. “This is the question most often asked by clients,” he says. “But there just is no definitive answer. It depends on each case individually. What is the purpose of the plant? For example, in the case where process steam needs to be generated, turbines are almost always the better solution since the exhaust heat has a higher initial temperature. In contrast, gas engine plants are usually advantageous as a district heating solution.” That is the conclusion of a recent study carried out by the University of Duisburg-Essen.

In comparison with a conventional gas-turbine combined-cycle power plant with a large gas turbine, the two versions of gas engines arranged in combined power plants showed higher energy and economic efficiency. 

Only a direct discussion with the client can clarify which technology is the right one for power and heat producers. MAN Diesel & Turbo is one of the few enterprises that produces both engines as well as turbines and can consult with their clients without any bias toward one or the other technology. “We have the most comprehensive CHP production portfolio in the market and can consult with our clients with full neutrality,” says Tütken.