Flessibilità ed Efficienza nella Generazione Elettrica da Combustibili Fossili

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1 Flessibilità ed Efficienza nella Generazione Elettrica da Combustibili Fossili Giuseppe Messina Secondo Workshop Nazionale Simulazione del sistema energetico e della sua sostenibilità Roma 5-6 Luglio 2016

2 Sustainable Combustion & Processes Laboratory Agenda Programmable Power Plants Flexibility Recoding of Combined Cycles Power Plants Power Plants vs Large Energy Systems Modelling Conclusions

3 Growth of flexibility requirement from conventional power plants

4 Flexibility: a new asset in the value chain of power generation MILAN, May In the last two Sundays, Germany has covered almost 100% of electrical energy needs by means of renewables.

5 Flexibility from power generation Start-up time [hours] Ramp rate [% per min] Time from 0 to full rate [hour] Minimum stable load factor [%] Hydro generation can respond more quickly than other technologies, but the resource is geographically limited Open Cycle Gas Turbines are therefore very often considered For the traditional base load power plants, a change in operation would translate into reduced load factors, while maintenance cost increase and thus lower financial revenue IEA Energy Technology Perspectives 2012

6 Flexibility paid with efficiency loss Process and Energy Systems KA26-1 SS Alstom Combined Cycle single shaft 50 Hz Gross power 500 MW GT MW + ST 155 MW 350 MW/15 min 23 MW/min load gradient from Low Load Operation (LLO) SCC5-4000F Siemens Combined Cycle single shaft 50 Hz Gross power 424 MW SGT F(4) 278 MW + SST MW 135 MW/5 min 27 MW/min load gradient* from fully warm plant *retrofit by SIEMENS FLEX POWER SERVICESTM The majority of 1 to 1 installed combined cycles can reach roughly a MAX load gradient of 27 MW/min, after complete start-up time or from Low Load Operation (LLO). Flexibility and efficiency are not coupled. Nominal point efficiency, in flexible generation is a chimera. In current power plants, more flexibility implies less efficiency and, consequently, more emissions and more costs.

7 Supercritical CO 2 Power Cycles S-CO 2 CCGT Cycle with CO 2 rich Gas Turbine + Alstom GT26 Concept ENEA ALBA Concept Economic Assessment - G. Di Lorenzo Thermodynamic Assessment - G. Messina

8 Sustainable Combustion & Processes Laboratory Supercritical CO 2 Power Cycles S-CO 2 Peculiarities

9 Supercritical CO2 Power Cycles Process and Energy Systems Bottoming S-CO2 Closed Cycle Cycle 1st pressure level: 1 (600 C 250 bar) to 2 (428 C 58 bar): HT Expansion 2 to 3 (65 C 57 bar): HTR output heat transfer 3 to 7 (217 C 263 bar): Re-compression 3 (62 C bar) to 4 (18 C 55.1 bar): Cooling & Condensing 4 to 5 (51 C 268 bar): 1st level pumping 5 to 8 (252 C 263 bar): LTR input heat transfer 8 to 1: heat transfer input from heat source Cycle 2nd pressure level: 3 (62 C bar) to 4 (18 C 55.1 bar): Cooling & Condensing 4 to 6 (55 C 300 bar): 2nd level pumping 6 to 9 (416 C 294 bar): HTR input heat transfer 9 to 10 (251 C 58 bar): LT expansion 10 to 3: LTR output heat transfer Cycle Efficiency: 40.58% ENEA works continuously at Advanced Liquid Compression BrAyton (ALBA) concept as a category of closed and semi-closed S-CO2 cycles with phase-balanced compression to increase both efficiency and compactness of fossil fuel power plants. Messina G., Giacomazzi E.: Modelling of a 48 MWt Supercritical CO2 Power Cycle Powered by the ISOTHERM PWR Loop Technical Report RdS/2013/298 Electric System Research ENEA - Italian Ministry of Economic Development - Program Agreement, 2013 (in Italian)

10 Supercritical CO2 Power Cycles Process and Energy Systems S-CO2 CCGT Cycle with CO2-rich Gas Turbine Project rationale CO2-rich GT Cycles can play a role in emission reduction (NOx) Sequential combustion could work better than conventional combustion with CO2-rich GT working fluid Sequential combustion could be a key parameter to reduce the parking load Higher content of CO2 in working fluid requires higher GT pressure ratio to obtain an attractive thermodynamic efficiency The joint effects of high pressure ratio and re-heat result in higher TOT and higher power density of the GT Cycle The joint effects of GT power density, very high power density of the bottom S-CO2 Cycle and heat recovery in a single phase (only supercritical no evaporation) could result in a more responsive power plant In a mid-term vision, CO2-rich GT Cycles can contribute to a cost-effective application of CCS, due to both the higher CO2 partial pressure in exhausts and the reduction of the mass flow treated by capture facilities GT 26 fully meets the project rationale and was chosen as base case + Alstom GT26 Concept ENEA ALBA Concept

11 Power Plants vs Energy Systems Modelling 8 hours of continuative running

12 Turbec T100 mgt Modelling On the basis of both the acquired knowledge and observation of the experimental data it has assumed the shape of the 'electrical power' function implemented in the gas turbine control system All the variables involved in the expression are observable and measurable Derive the explicit form of the function requires a large number of experiments hardly executable for the inability to individually control all the variables involved

13 Turbec T100 mgt Modelling All variables are representative of many significant speed in the field of turbomachinery C is a dimensionless group of three speeds The expression is simple and easy to handle A single dimensionless group allows to fully characterize the MGT generator

14 Turbec T100 mgt Modelling Test T100 February

15 Turbec T100 mgt Modelling Test T100 February Unstable behavior = fast dynamic

16 Turbec T100 mgt Modelling Test T100 February

17 Turbec T100 mgt Modelling static component dynamic component G has Power dimensions

18 Turbec T100 mgt Modelling Test T100 May

19 Turbec T100 mgt Modelling static component dynamic component V I It is the product of the of the DC-link voltage change to the current.

20 Turbec T100 mgt Modelling Test T Maggio 2013

21 Turbec T100 mgt Modelling Test T100 May

22 Turbec T100 mgt Modelling

23 Turbec T100 mgt Modelling The approach has been validated with a large number of experimental data, in unstable operation conditions of the machine, on machines that expose very different dynamic response. The approach includes both the scalability and generality requirements, derived from the expression of C : 1. Turbine a gas di dimensione e potenza diversa 2. Turbine a gas operanti con fluidi di lavoro diversi dall aria

24 Conclusions The increasing penetration of renewable require ever greater flexibility from programmable power generation Large-scale energy systems modelling must include the correct encoding of the power plant flexibility as a technical-economic variable of the model The coupling of large scale system models with power plant models, with reasonable computational resources, requires a "light" power plants encoding: to look to the control systems instead of physical systems could be a solution.

25 Sustainable Combustion & Processes Laboratory Grazie per la cortese attenzione