Engineering the Energiewende19 June 2014
Challenges and opportunities for fossil-fuelled power plants in Germany.
For a country aiming to embrace renewables in a very big way, Germany paradoxically currently finds itself with an embarrassingly large number of big supercritical hard coal plants (all boasting efficiencies around the 46% mark) that have just entered or are about to go into commercial operation - on top of three substantial lignite units that went into operation in 2012 (Neurath F and G (RWE), 2 x 1100 MWe, and Boxberg R (Vattenfall), 1 x 670 MWe)).
The first of Germany's new wave of coal plants to be declared fully in operation was Trianel's Lünen plant (1 x 750 MWe), on 1 December, followed very shortly after by Steag's Walsum 10 (1 x 790 MWe), on 20 December.
The day before, on 19 December, the GDF Suez Wilhelmshaven plant (also 1 x 790 MWe) was connected to the grid, with commercial operation expected mid-year.
EnBW also expects its RDK8 plant (1 x 911 MWe) to be declared commercial in the first half of 2014.
Unit E of RWE's Westfalen (Hamm) plant (2 x 800 MWe) is due to enter full commercial operation in June, with unit D following six months later (having experienced problems due to a "cocktail of chemicals" entering the boiler inadvertently during commissioning).
The first unit of Vattenfall's Moorburg station (2 x 820 MWe) fed power to the grid on 28 February and full commercial operation is anticipated in autumn 2014, with the second block following a few months later.
GKM's Mannheim 9 plant (1 x 911 MWe) is expected to enter commercial operation in 2015.
And then there is E.ON's Datteln 4 (1 x 1100 MWe), seen by some as a lost cause. The plant, although at an advanced stage of construction, currently has no estimated start up date, but is now showing signs that the permitting problems it has been bogged down in for several years (see Modern Power Systems, December 2012, pp 30-32) could be moving towards some sort of resolution.
An important step has been the decision by the Ruhr Area Association to amend the regional development plan, a precondition for changing the municipal land-use plan, which in turn could allow issuance of the remaining permits required for completion. The next key milestone depends on the Datteln city council, which was expected to make a decision on the land use plan in mid May. The old Datteln units (1, 2 and 3) were closed down at the end of February 2014 and the new traction power converter at the Datteln site, which provides electricity at 16.7 Hz to DB (intended to be powered by Datteln 4, but currently being supplied from the grid) has been commissioned (at 413 MW, the most powerful such converter ever built).
All these new build hard coal and lignite projects - which are the legacy of utility planning decisions made a decade or more ago, when no-one worried much about carbon dioxide - have suffered major delays of one sort or another, most notably due to problems, now apparently resolved, with the alloy T24 (used in boilers supplied by Hitachi Power Europe and Alstom).
One project that avoided the traumas of T24 was Lünen, supplied on a turnkey basis by a consortium of Siemens and IHI, and using a slightly more conservatively designed IHI boiler not employing T24. The plant is said by Trianel to now be "a mainstay of the energy mix in the state of North-Rhine Westphalia." It also supplies the town of Lünen with district heating.
Meanwhile at Walsum 10, most of the marketable capacity of the plant has been sold on a long-term, 20 year basis, contributing to Steag's improved earnings.
For Germany as a whole, coal and lignite are still a key part of the energy mix, accounting, respectively, for 19.6% and 25.6% of electricity generated in 2013 (the corresponding figures for 2003 being 24.1% and 26.0%). And despite the significant growth in renewable generating capacity in recent years there are still days when fossil fuels account for a very large of proportion of total electricity generation.
Gas in decline
But, as elsewhere in Europe, gas generation is currently in the doldrums in Germany, particularly for electricity-only plants. Relatively cheap imported coal (attributable to reduced demand in the USA thanks to shale gas), abundant indigenous lignite, combined with must-run and heavily subsidised renewables, low and declining wholesale electricity prices, and low carbon dioxide emissions allowance prices have all conspired to make gas fired generation very uncompetitive, resulting in low load factors and mothballing of facilities.
Energy and water trade association BDEW (Bundesverband der Energie- und Wasserwirtschaft) has estimated that in the past year the use of gas in electricity-only power applications has fallen by about a third.
One way gas fired combined cycle power plants can improve their competitiveness in the German market is to provide heat as well as power. This is the hope for what is now known as the Block Fortuna combined cycle plant currently under construction for Stadtwerke Düsseldorf at Lausward in the Düsseldorf harbour area. The 595 MWe Siemens H class facility, due to start up in 2016, will provide 300 MWt for one of Germany's largest district heating systems, giving it an expected utilisation rate of 5000 hours per year, well above the profitability threshold of around 3000 h/y. In contrast many gas fired plants in Germany are operating for only 1000-2000 h/y.
Not all combined cycle plants are lucky enough to have access to a ready made district heating network, of course.
Another possibility for the hard-pressed combined cycle plant is to implement modifications to increase operational flexibility, eg allowing it to enter the market sooner and stay in it longer. This is the strategy adopted by Trianel for its 2 x 424 MW Siemens-supplied Hamm-Uentrop combined cycle plant, which started up in 2007. As explained in a presentation by T Klenwaechter and A Dibbert at O&M and Lifecycle Management for CCGT Power Plants 2014 (5 - 6 March, Birmingham, UK, organised by T. A. Cook), Trianel asked Siemens to suggest ways of increasing operational flexibility at a user group conference in 2011. A concept was proposed in 2012 and implementation was carried out over 5 days in 2013. The package of measures, which includes modifications to the feedwater control system and fitting of four thermocouples in each HRSG, increases the load gradient from 13 MW/min to 26 MW/min, and is called FLG (fast load gradient) 26. The FLG26 modification has now been implemented at eight plants, in Germany and elsewhere.
Capacity market needed
Another measure that might help beleaguered combined cycle plants is the introduction of a capacity market, which has been proposed by the coalition government and which many in the power industry see as the next key task following introduction of the new renewable energy law.
Johannes Teyssen, CEO of E.ON, which says it has shutdown 13 GW of its "conventional" generating capacity in Germany and elsewhere in Europe, describes it as "surprising" that fossil fuelled generating units are tacitly and, as a matter of course, planned for use as reserve capacity (when renewables generation is low), but without appropriate compensation being provided for them, and notes that the value of these conventional assets has been demonstrated on recent dark and windless winter days when renewables provided just 5% of Germany's power demand.
BDEW is also calling for a capacity market, "so we are prepared for possible bottlenecks in a few years time", says its chair person Hildegard Müller.
BDEW lists some 74 "firm capacity" (ie, fossil fuelled and offshore wind) plants of over 20 MW at various stages of commissioning, construction and planning in Germany, totalling about 38 GW - which would seem a healthy amount compared to most other European countries.
But according to BDEW about 32 of the planned projects may well not happen due to increasing investor uncertainty (although the outlook for offshore wind is judged to have improved thanks to progress on grid connection provisions following concerted efforts by regulators, TSOs and wind farm developers).
Based on present knowledge, Hildegard Müller says that overall firm capacity in Germany will decline by some 13 600 MW by the time nuclear power is phased out in 2022.
James Varley, group managing editor at ModernPowerSystems magazine