DUKE: Solar Field Development for Direct Steam · PDF fileDUKE: Solar Field Development for...


Why Direct Steam Generation?


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


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)


A brief history of DSG development…


Milestones in DSG developmentThe very beginnings – DSG was first

John Ericsson• New York, USA, 1870 and 1883• 3.25-m2-aperture collector• Driving a small 373-W engine.

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.

Shuman Collector


Milestones in DSG developmentDISS: 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.


Milestones in DSG developmentPlanning 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.


Milestones in DSG developmentDSG Component tests at 500 °C

2010/2011Real-DISS test facility112 bar / 500 °C

PCM storagesystem


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!


Milestones in DSG developmentLinear Fresnel plants

PE-1: 1 MW, 55 bar, saturated steamPE-2: 30 MW, 55 bar, saturated steamBoth plants with Linear Fresnel technology by Novatec Solar Source: DLR


Milestones in DSG developmentThe first parabolic trough plant with superheating

Source: Solarlite

TSE-1, Thailand5 MWe34 bar, 340 °CTechnology by Solarlite


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


And now? Further solar field development…


State-of-the-Art Solar Field Concepts for DSG

• With central steam drum

• With decentral steam drums

• With one or two injectionsRecirculation Once-Through

Source: DLR


Concept Comparison > Sub-field Layout

Recirculation (cental) Once-through

Source: DLR

About 70% less piping and less header heat losses


Concept Comparison > Pros and Cons

+ Very robust operation+ Commercially applied

- Higher investment

- Slower start-up

- Higher design effort

+ Easily scalable+ Fast start-up+ Lower investment+ Higher efficiency

- Less robust

- Higher control effort

- End of evaporation not fixed

Recirculation Once-Through


Goal:• Analysis and demonstration of once-through concept

under real irradiation conditionsPartners:

• DLR• (Solarlite)• In cooperation with CIEMAT-PSA

Tasks:• Design and build test facility• Test control strategies and

solar field behaviour• Evaluate results and potential

Once-through mode > DUKE Project

DUKE = Durchlaufkonzept – Entwicklung und Erprobung


DUKE > Demonstration at DISS Facility at PSA

BOP und Control room

New Solarlite 4600+ collectors (3x 100m)

North


DUKE > Upgrade of DISS Test Facility



Three new Solarlite collectors



Relocation of inlet valves



New Receivers for 125 bar / 500°C



Aligning coll. 9 horizontally



New ball joints and piping



New steamattemperator



New injection instrumentation



Fast temperature measurements along end zone of evaporation

(57 thermocouples in total)



Adapted receivers with thermocouples in vacuum around circumference

(10 along end zone of evaporation)


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


What will be tested in the project?


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 derivedcontrol concepts

Derivation of directly applicable control strategies for commercial plants


Main goal > Develop and test control strategies

• Control of outlet temperature• Stabilization of end point of evaporation

• Sensitive to DNI variation

• Non-minimum phasesystem behaviour due toevaporation

• Bad state observability in evaporation section


Why do we need control strategies?

• DNI varies with timeand location!

Inbalance of loop Inbalance of whole field

Aerial view of Andasol Plants


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


Outlook on control strategies (II)

• Use prediction of DNI in evaporation section to determinefuture/current end of evaporation for better control results

Realistic DNI prediction not yet possible METAS

Local DNI Prediction


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


Questions and Contact…

Jan Fabian FeldhoffDLR Institute of Solar Research, [email protected]

By Ron Tandberg

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