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Process and Energy Systems Process and Energy Systems

Engineering LaboratoryEngineering Laboratory



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

Programmable Power Plants Flexibility

Recoding of Combined Cycles Power Plants

Power Plants vs Large Energy Systems Modelling

Conclusions

Agenda Sustainable Combustion

& Processes Laboratory





Growth of flexibility requirement from conventional power plants





Flexibility: a new asset in the value chain of power generation

MILAN, May 18 2016 In the last two Sundays, Germany has covered almost 100% of electrical energy needs by means of renewables.





Flexibility from power generation

IEA – Energy Technology Perspectives 2012

• 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

Start-up time [hours] Ramp rate [% per min] Time from 0 to full rate [hour] Minimum stable load factor [%]





Flexibility paid with efficiency loss

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.

SCC5-4000F Siemens Combined Cycle single shaft – 50 Hz

Gross power 424 MW SGT 5-4000F(4) 278 MW + SST 5-3000 146 MW

135 MW/5 min ≈ 27 MW/min load gradient* from fully warm plant *retrofit by SIEMENS FLEX POWER SERVICESTM

KA26-1 SS Alstom Combined Cycle single shaft – 50 Hz

Gross power 500 MW GT26 345 MW + ST 155 MW

350 MW/15 min ≈ 23 MW/min load gradient from Low Load Operation (LLO)





Supercritical CO2 Power Cycles S-CO2 CCGT Cycle with CO2 rich Gas Turbine

+ Alstom GT26 Concept ENEA ALBA Concept

Economic Assessment - G. Di Lorenzo

Thermodynamic Assessment - G. Messina

Supercritical CO2 Power Cycles S-CO2 Peculiarities Sustainable Combustion






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)

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 – 56.75 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

Supercritical CO2 Power Cycles Bottoming S-CO2 Closed Cycle

Cycle 2nd pressure level: 3’ (62 °C – 56.75 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

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.

Cycle Efficiency: 40.58%





Supercritical CO2 Power Cycles S-CO2 CCGT Cycle with CO2-rich Gas Turbine

+AlstomAlstom GT26 ConceptGT26 Concept ENEA ALBA ConceptENEA ALBA Concept

+AlstomAlstom GT26 ConceptGT26 Concept ENEA ALBA ConceptENEA ALBA Concept

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





Power Plants vs Energy Systems Modelling

8 hours of continuative running





Turbec T100 mGT Modelling

• 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

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 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






Test T100 February 23 2016







Unstable behavior = ‘fast dynamic’





• G has Power dimensions


‘static’ component ‘dynamic’ component






Test T100 May 30 2013






• ∆𝑉 ∙ 𝐼 It is the product of the of the DC-link voltage change to the current.

‘static’ component ‘dynamic’ component






Test T100 30 Maggio 2013






Test T100 May 30 2013






• 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





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.

Grazie per la cortese attenzione

www.enea.it

[email protected]

Sustainable Combustion


mailto:[email protected]




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