Lignite-fired power plants in Germany under criticism

Author: Dr. Klaus Hassmann, Cluster Energy Technology (As of August 2016) Lignite is a domestic primary energy source and also the cheapest fuel for power plant operation; lignite is extracted in opencast mining and feeds the plants built in the immediate vicinity. Accordingly, lignite is a domestic economic factor; the employment effect must be taken into account.

Among electricity generation technologies, lignite-fired power plants are the target of emotions. People use this technology to ward off the power grids planned by the grid operators to the south; the lignite areas are located in the west and east of the republic. The planned power lines from north to south, primarily dedicated to transporting wind power, do not run too far away. The dirty electricity, i.e., electricity polluted with large amounts of CO2, could reach the south of the republic with the lines; other pollutants such as dust and NOx are subject to emission limits that all power plants must comply with. The argument "lignite is bad for the environment" is understood by the citizen; this can be used to build up a front of prevention against the electricity highways. Pollutant emissions from electricity generation are usually attributed to the on-site balance; however, there are stakeholders who allocate CO2 emissions according to the consumer principle when electricity is distributed through power lines.

Electricity generation from lignite since the start of the energy transition in 2011

The power plant lists of the Federal Network Agency of 16. 7. 2014 and those of 10. 5. 2016 were evaluated. Data were also taken from the evaluation tables for the energy balance of Germany of the Arbeitsgemeinschaft Energiebilanzen e V and various documents available to the author.

Table 1: Development of lignite-fired power plants from 2011

Table 1 shows important data on the development of the lignite-fired power plant fleet; it is to be updated in this form in the portal over the years. As announced several times, the German government intends to have more lignite-fired power plants decommissioned against the resistance of the affected federal states. From 2011 to 2014, a total of 1764 MW of power plant capacity was taken off the grid; in terms of the value of power plants in operation, this is about 8%; it is also interesting to note that almost all of the shutdowns were carried out in NRW. See below for an attempt to explain this. A good start, no question; the "but..." refers to 2015 and 2016, when only 111 MW of additional power plant capacity was shut down. Table 1 also shows that by far the most lignite-fired power plants are in operation in NRW; ranked behind them are Brandenburg and Saxony, each with half the capacity.

Unfortunately, the efficiency ratings of the plants are not published by the agencies responsible for the energy transition  nor are they included in the power plant lists cited above. In general, the older the plants are, the lower the efficiency, the more CO2 is released. In power plant technology, new developments that increase efficiency have been used over time; these include, for example, an improved design of the overall power plant as well as the components through new materials and an optimized mode of operation tailored to this. Accordingly, age or operating time is a revealing indicator of efficiency. The average performance-related age of the power plants is 33 years in NRW, 28 years in Brandenburg, 22 years in Saxony-Anhalt and 17 years in Saxony.

Interesting is the evaluation according to the ability of the power plants to extract heat, which has a strong efficiency-increasing effect in all plants. Thus in North Rhine-Westphalia only approx. 35%, in the new Lands of the Federal Republic however nearly 100% of the power station achievement with warmth Auskopplung are operated. It can be deduced from this that both parameters, the higher operating age (54 years on average) as well as the insufficient heat extraction, were the reason why almost exclusively NRW has been affected by the decommissioning of lignite-fired power plants since 2011; this will probably remain the case in the coming years. As a supplement, it should be mentioned that in the German lignite-fired power plant fleet, 260 MW are listed under provisionally decommissioned.

One more key figure to conclude the statistics: the energy balance for 2013 shows a value for primary energy of 1474 peta joules (1 PJ is 10 15 J) for electricity generation by lignite. In terms of total electricity generation, primary energy consumption by lignite is a high 30%. In addition, two assumptions:

1. The 1474 PJ of primary energy are burned in the lignite-fired power plants in the power plant list.
2. In Germany, the electrical efficiency of the coal-fired power plants still in operation is about 38%. The age of the coal-fired power plant fleet is about the same as that of lignite-fired power plants. At approximately the same stage of development, the efficiency of lignite-fired power plants is several percentage points lower than that for hard coal. If an average efficiency of 35% is assumed for the lignite fleet, the lignite-fired power plants ran for about 7000 full load hours in 2013! This is a surprisingly high value. This is unlikely to have changed much in recent years until 2016.

Conclusion

The gap that arises when the sun does not shine and/or the wind does not blow or only weakly, is filled by electric power  generated from conventional power plants. The energy turnaround has changed electricity trading via the stock exchange quite decisively; stock exchange prices have fallen to an almost historically low level for the kWh. Only the electricity consumer does not feel much of this; the escalating costs for the expansion of renewable energies, those for grid expansion at various voltage levels, and various other charges lead to an increase in kWh prices for the consumer at regular intervals. It is already a Sisyphean task to adjust the individual contributions to the customer end price again and again in such a way that its main contributors - these include the Renewable Energy Sources Act (EEG), everything that is charged via the grid fee and the stock exchange price - are made as balanced as possible; the success of the energy turnaround must not be called into question. That seems to succeed the Federal Government with various adjustments.

Incentives for the building of new power plants, whatever kind, are missing; under the rules valid today at the power exchange, electricity from not written off fossil power plants is not in the money. Depreciated, meaning old, power plants are on the move today.

Transport networks from north to south will be delayed. New dispatchable power generation capacity (means fossil-fired power plants) will be needed with the shutdown of nuclear power plants located in supply-critical regions, especially in the south. Tenders are being prepared. Cheap and flexible plants will win the race as "bridging power generators." Coal-fired power plants will not be among them.

Back to lignite: the age of the fleet of power plants in operation, especially those without heat extraction, is relatively high. The question arises: are these aged power plants up to the demands of the energy transition, or can they complement this complex system in a technically sensible way with a still significantly increasing expansion of fluctuating renewables feeding into the grid? Major doubts are warranted; their efficiency is modest, their CO2 emissions high. As one hears and reads, other important features, such as controllability with the necessary steep gradients into partial load (this is usually associated with further efficiency losses) or short start-up times from the cold state of the power plant are unsatisfactory to impossible. This also applies to plants with heat extraction.

The balance of economic efficiency, security of supply and environmental compatibility comes out of equilibrium at the expense of the latter because of CO2. The plants should be taken off the grid step by step. Here's an idea: a kind of Technical Monitoring Association (TÜV) for power plants would be installed, specifying the requirements of the energy transition and issuing a license to the power plants that are (still) suitable for operation after inspection; this license would grant the operators the right to bid on the power exchange. The "operational readiness" would have to be reviewed every few years. Then, as with the car, a new "badge" would be issued for a certain period of time.