DUKE: Solar Field Development for Direct Steam Generation

www.dlr.de/sf Slide 3 Why Direct Steam Generation?

www.dlr.de/sf Slide 4 Parabolic Trough Plants with Oil + Commercially applied + One-phase flow + Easily scalable - Heat exchanger batteries - T < 400 C - Efficiency/process limit reached - Hazardous to environment

www.dlr.de/sf Slide 5 Direct Steam Generation (DSG) Plants + No heat exchangers + High temperatures + High efficiency + Non-toxic fluid + Simple overall configuration - Two-phase flow - Higher control effort - Higher temperature gradients - Expensive thermal storage (so far)

www.dlr.de/sf Slide 6 A brief history of DSG development

www.dlr.de/sf Slide 7 Milestones in DSG development The very beginnings DSG was first John Ericsson New York, USA, 1870 and 1883 3.25-m2-aperture collector Driving a small 373-W engine. Shuman Collector Frank Shuman Meadi, Egypt, 1912-1913 5 collectors 62x4m driving a steam engine (~40 kw) used to pump water for irrigation Fernández-García, A., Zarza, E., Valenzuela, L., et al., 2010, "Parabolic-trough solar collectors and their applications," Renewable and Sustainable Energy Reviews, 14, pp. 1695-1721.

www.dlr.de/sf Slide 8 Milestones in DSG development DISS: EU project at PSA: 500 m/100 bar/400 C Zarza, E., Valenzuela, L., León, J., et al., 2004, "Direct steam generation in parabolic troughs: Final results and conclusions of the DISS project," Energy, 29 (5-6), pp. 635-644.1721.

www.dlr.de/sf Slide 9 Milestones in DSG development Planning of demonstration plant INDITEP - Application of design tools - 5 MWe, 410 C / 70 bar - Recirculation with decentral separators - Another 200m for DISS Zarza, E., Rojas, M. E., González, L., et al., 2006, "INDITEP: The first pre-commercial DSG solar power plant," Solar Energy, 80 (10), pp. 1270-1276.

www.dlr.de/sf Slide 10 Milestones in DSG development DSG Component tests at 500 C 2010/2011 Real-DISS test facility 112 bar / 500 C PCM storage system

www.dlr.de/sf Slide 11 Lessons learned Solar steam generation in horizontal pipes is possible Tubes do not need to be tilted, if mass flow is high enough Most robust and safe operation with recirculation mode Parallel flow distribution can be handled by controlling inlet mass flow to every loop Outlet temperature should be controlled by additional injection in superheating section Implemented in commercial plants!

www.dlr.de/sf Slide 12 Milestones in DSG development Linear Fresnel plants PE-1: 1 MW, 55 bar, saturated steam PE-2: 30 MW, 55 bar, saturated steam Both plants with Linear Fresnel technology by Novatec Solar Source: DLR

www.dlr.de/sf Slide 13 Milestones in DSG development The first parabolic trough plant with superheating TSE-1, Thailand 5 MWe 34 bar, 340 C Technology by Solarlite Source: Solarlite

www.dlr.de/sf Slide 14 DSG Status: It s commercial! Topics for industry: Higher steam parameters (up to 110 bar /500 C) Parameter Optimization Pressure and temperature vs. piping cost Improvements in plant configurations and costs Topics for R&D: Solar Field Optimization Optimized recirculation, once-through Operation Optimization Start-up, Control Thermal Energy Storage Costs, Performance Plant integration options Hybrid, TES

www.dlr.de/sf Slide 15 And now? Further solar field development

www.dlr.de/sf Slide 16 State-of-the-Art Solar Field Concepts for DSG Recirculation With central steam drum Once-Through With one or two injections With decentral steam drums Source: DLR

www.dlr.de/sf Slide 17 Concept Comparison > Sub-field Layout Recirculation (cental) Once-through About 70% less piping and less header heat losses Source: DLR

www.dlr.de/sf Slide 18 Concept Comparison > Pros and Cons Recirculation + Very robust operation + Commercially applied Once-Through + Easily scalable + Fast start-up + Lower investment + Higher efficiency - Higher investment - Slower start-up - Higher design effort - Less robust - Higher control effort - End of evaporation not fixed

www.dlr.de/sf Slide 19 Once-through mode > DUKE Project Goal: Analysis and demonstration of once-through concept under real irradiation conditions Partners: DLR (Solarlite) In cooperation with CIEMAT-PSA Tasks: Design and build test facility Test control strategies and solar field behaviour Evaluate results and potential DUKE = Durchlaufkonzept Entwicklung und Erprobung

www.dlr.de/sf Slide 20 DUKE > Demonstration at DISS Facility at PSA BOP und Control room New Solarlite 4600+ collectors (3x 100m) North

www.dlr.de/sf Slide 21 DUKE > Upgrade of DISS Test Facility

www.dlr.de/sf Slide 22 DUKE > Upgrade of DISS Test Facility Three new Solarlite collectors

www.dlr.de/sf Slide 23 DUKE > Upgrade of DISS Test Facility Relocation of inlet valves

www.dlr.de/sf Slide 24 DUKE > Upgrade of DISS Test Facility New Receivers for 125 bar / 500 C

www.dlr.de/sf Slide 25 DUKE > Upgrade of DISS Test Facility Aligning coll. 9 horizontally

www.dlr.de/sf Slide 26 DUKE > Upgrade of DISS Test Facility New ball joints and piping

www.dlr.de/sf Slide 27 DUKE > Upgrade of DISS Test Facility New steam attemperator

www.dlr.de/sf Slide 28 DUKE > Upgrade of DISS Test Facility New injection instrumentation

www.dlr.de/sf Slide 29 DUKE > Upgrade of DISS Test Facility Fast temperature measurements along end zone of evaporation (57 thermocouples in total)

www.dlr.de/sf Slide 30 DUKE > Upgrade of DISS Test Facility Adapted receivers with thermocouples in vacuum around circumference (10 along end zone of evaporation)

www.dlr.de/sf Slide 31 Upgraded DISS Facility is ready Extension to 1000 meters New design values 500 C and 112 bar at outlet New instrumentation for better once-through mode analysis Temperature measurements along end of evaporation Cross section measurements at critical locations Photo by DLR/QFly, January 2013

www.dlr.de/sf Slide 32 What will be tested in the project?

www.dlr.de/sf Slide 33 DUKE > Different Types of Tests 1. Qualification of components (Optical efficiency, heat loss ) 2. Validation of dynamic models (step response tests ) 3. Test and validation of derived control concepts Derivation of directly applicable control strategies for commercial plants

www.dlr.de/sf Slide 34 Main goal > Develop and test control strategies Control of outlet temperature Stabilization of end point of evaporation Sensitive to DNI variation Non-minimum phase system behaviour due to evaporation Bad state observability in evaporation section

www.dlr.de/sf Slide 35 Why do we need control strategies? DNI varies with time and location! Inbalance of loop Inbalance of whole field Aerial view of Andasol Plants

www.dlr.de/sf Slide 36 Outlook on control strategies (I) Use current control concepts for outlet temperature as reference Adapt controller parameters according to operation point Use temperature observation in superheating section for outlet control Use temperature observation to determine former end of evaporation Currently applicable, to be implemented in DUKE

www.dlr.de/sf Slide 37 Outlook on control strategies (II) Use prediction of DNI in evaporation section to determine future/current end of evaporation for better control results Realistic DNI prediction not yet possible METAS Local DNI Prediction

www.dlr.de/sf Slide 38 Conclusions and Outlook Direct Steam Generation in recirculation mode is commercial Next step for research: development of once-through concept More efficient and easier to scale But: not that robust and so far unclear impact of fluctuating end of evaporation Projekt DUKE to answer the remaining questions Upgrade of DISS test facility Demonstration/proof of once-through concept Evaluation of concept s potential

www.dlr.de/sf Slide 39 Questions and Contact Jan Fabian Feldhoff DLR Institute of Solar Research, Stuttgart jan.feldhoff@dlr.de By Ron Tandberg