Dipl.-Ing. Holger Derlien 1,2,4 Jan Thiedau, M.Sc. 3,4 Prof. Dr. Marc Steinbach 3,4 Prof. Dr.-Ing. Joachim Müller-Kirchenbauer 1,2,4 1

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1 Power to Compression: Electric and Gas Driven Compressor Optimization for Energy Cost Reduction and Renewable Electricity Storage in the Natural Gas Infrastructure Dipl.-Ing. Holger Derlien 1,2,4 Jan Thiedau, M.Sc. 3,4 Prof. Dr. Marc Steinbach 3,4 Prof. Dr.-Ing. Joachim Müller-Kirchenbauer 1,2,4 1 Technische Universität Clausthal, Department Gas Supply Systems at the Institute of Petroleum Engineering 2 Energie-Forschungszentrum Niedersachsen, Research Department Energy Infrastructures 3 Gottfried Wilhelm Leibniz Universität, Institute for Applied Mathematics 4 Niedersächsische Technische Hochschule (NTH) Copenhagen, September 17 th, 2014 Photo: Gascade

2 Structure Motivation and background The underlying theory Case study results Conclusions and Outlook 2

3 Motivation and Background Increasing demand for (long term) renewable power storage, indicated by periods with low power prices Gas turbines for compressor drives are among the least efficient natural gas appliances High economic cost for compressor fuel gas in gas importing countries Increasing import pipeline capacity demand for final customers CO 2 emissions certificate costs, and tightening air quality standards for gas turbines Reliable gearless high speed electric drives >25 MW have become available EU regulation requires efficiency audit for gas supply infrastructure by mid-2015 Research questions: Can pipeline transportation cost be reduced with a combination of gas and electrically driven compressor units by switching between these units increasing pipeline pressure at times with available capacity and very low power prices? Are there other economic and ecologic benefits associated with this concept? Will the gas supply still be reliable with pipelines partially operated by electric motors? 3

4 The hourly power price fluctuates with demand, and availability of renewable electricity, indicating power storage demand Source: Mayer, Burger (Fraunhofer ISE), Data: EEX, Entso-E 4

5 Switching from gas turbine to electric motor compressor drives: Functionally equivalent to Power to Gas long term energy storage η Electric drive 0,9 incl. auxiliaries η Gas turbine 0,2 (old) to 0.43 (new with heat recovery) Power grid with wind and solar energy production 1 MWh 1 MWh M GT Power to Compression Reduced fuel gas offtake during electric drive operation 2 4.5MWh Natural Gas pipeline Power to Gas Electrolyzer (+ Sabatier Methanization Reactor) MWh Comparison with direct/electrolytic Power to Gas + Considerably higher efficiency + Lower investment cost + No hydrogen injection issues + No CO 2 sourcing/ Methane emission issues for Sabatier methanization option Limited potential: Only possible at compressor locations Only possible at times with compression demand 5

6 The mathematical model for nonstationary optimization Gas network represented as directed graph Set of variables Abstract problem Mathematical problem too complex to solve Acceptable simplifications: Discretization of Euler equations with Finite Differences box scheme Compressor stations: Piecewise constant control Nonlinear optimization problem with smooth objective and constraints that can be handled with solver Ipopt 3.11 (Wächter, Biegler 2006) 6

7 00:00 03:45 07:30 11:15 15:00 18:45 22:30 1\02:15 1\06:00 1\09:45 1\13:30 1\17:15 1\21:00 2\00:45 2\04:30 2\08:15 2\12:00 2\15:45 2\19:30 2\23:15 3\03:00 3\06:45 3\10:30 3\14:15 3\18:00 3\21:45 4\01:30 4\05:15 4\09:00 4\12:45 4\16:30 4\20:15 5\00:00 5\03:45 5\07:30 5\11:15 5\15:00 5\18:45 5\22:30 6\02:15 6\06:00 6\09:45 6\13:30 6\17:15 6\21:00 7\00:45 7\04:30 Plausibility check, and comparison of optimization results with SIMONE simulation software 16,00 14,00 12,00 MW 10,00 8,00 Hannover Data Simone Data 6,00 4,00 2,00 0,00

8 Case study: OPAL/GAZELA, and NEL onshore pipeline extensions of the Baltic Sea pipeline Nord Stream NEL MOP 100 bar OPAL MOP 100 bar CS Radeland (2+1)*32MW gas turbine driven GAZELA MOP 85 bar (Czech Republic) 8

9 ,00 /MWh 150,00 Case study input data: German hourly day-ahead power market price during the gas year 2012/ ,00 50,00 0,00-50,00-100,00-150,00-200,00 Representative week for subsequent graphical display of case study results -250,00 Source: EEX 9

10 OPAL/GAZELA pressure profile with hypothetical electric drives in Radeland Inlet from Nordstream at 100 bar Radeland CS with electric drives instead of gas turbines German/Czech border contractual p min 75 bar Outlet to MEGAL CS in Germany 10

11 OPAL/GAZELA pressure profile for addition of two booster compressor units with electric drives Inlet from Nordstream at 100 bar Uckermark CS 1*25MW with electric drive Radeland CS with gas turbines as is Olbernhau CS 1*25MW with electric drive MEGAL Waidhaus CS in Germany 11

12 Case study results and findings summary Basic case study OPAL (compressor drive replacement in Radeland) Extensive use of available linepack for cost optimization Cost savings can not justify the necessary investment for electric drives Higher compressor energy demand at Radeland compressor station, but energy savings at MEGAL inlet compressor station Extended case study (MEGAL CS considerated) Considerable cost savings by increased average pressure, and additional linepack flexibility, may justify addition of one or two booster units with electric drives Additional savings by increasing the GAZELA MOP, if possible Cost savings compensation scheme between OPAL, GAZELA, and MEGAL pipeline companies necessary Case study NEL capacity extension (hybrid gas/electric CS with German gas/power grid fees and taxes considered) Almost no operation of electric drive unit even at very low, or negative power prices Joint effort of the pipeline companies with regulatory and legislative bodies necessary to achieve lowest gas transport cost solution 12

13 Taxes of power and natural gas in Germany (main components) Taxes in /MWh 90 Power-/natural gas tax ratio Power tax Renewables investment power tax CHP power tax Natural gas tax Power vs. gas taxes ratio Stromsteuer EEG KWK Erdgassteuer Verhältnis 13

14 Conclusions and Outlook Significant cost reductions possible with electric compressor energy market prices, but national legal issues have to be considered Additional cost reductions by using available linepack for Demand Side Management ( price-induced pack & draft ) Positive effects on adjacent gas transport infrastructure possible Electric compressor drives power consumption may reduce power system bottlenecks Reliability can be maintained with gas driven compressor units during power outages Optimum compressor layout must be determined on project-to-project basis Reduction of Power to Gas investment, and efficiency losses possible Outlook Refining the mathematical model (compressor maps, switching costs, ) Joint optimization of storage, and pipeline compressors in complex grid structures Optimizing the legal details (taxes, regulation) for maximum economic efficiency Integrate power market signals into day-to-day dispatching operations Investigation of current international pipeline projects Trans Adriatic Pipeline from turkish-greek border to Italy South Stream onshore? 14

15 Thank you for your attention. Contact details for questions and comments: Paper will be available via after the conference Disclaimer: The research project Power to Compression is funded by the German federal state of Lower Saxony. The authors would like to thank the participants of an industry expert workshop for valuable comments and suggestions. 15