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RESEARCH PAPERS

Dual Receiver Concept for Solar Towers up to $100MW$

[+] Author and Article Information
M. Eck, R. Buck, M. Wittmann

German Aerospace Center (DLR), Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

In case of the sliding pressure mode load changes cause pressure changes and thus changes of the evaporation pressure and temperature. Accordingly, during transients the evaporator tubes have to be heated up or cooled down.

Since no detailed information on the recirculation rate forth he dual receiver is available yet, a recirculation rate of 50% is assumed for both cases. Since the air outlet temperature of the reference plant is higher than that of the dual receiver, its recirculation losses are higher.

J. Sol. Energy Eng 128(3), 293-301 (Oct 24, 2005) (9 pages) doi:10.1115/1.2210501 History: Received May 23, 2005; Revised October 24, 2005

Abstract

The dual receiver concept presented in this paper improves the adaptation of the central receiver to the steam cycle in a solar thermal power plant. By combination of an open volumetric air heater and a tubular evaporator the dual receiver concept profits from the advantages of these two concepts while their characteristic problems are avoided. The water is evaporated directly in the tubular steam generator; preheating and superheating are done in heat exchangers by using the hot air from the volumetric receiver. This paper presents a concept study that extends previous work on the $10MWel$ level (Buck, 2004, “Dual Receiver Concept for Solar Towers  ,” Proc. 12th Solar PACES Int. Symposium, Oct. 6–8, Oaxaca, Mexico) to a level of $100MWel$, which is the expected power range of future plants. The results confirm the benefits of the new concept, resulting from higher thermal efficiency of the receiver and lower parasitic power consumption. The annual mean efficiency is increased from 13% to 16%. Advantageous are also the reduced thermal loads in the receiver components.

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Figures

Figure 1

Schematic of dual-receiver concept; combination of volumetric air heater and tubular evaporator

Figure 2

Course of temperatures during transfer of heat from air to water for dual receiver concept

Figure 3

Figure 4

Ratio of ηrec and Q̇tub* as a function of the heat flux density for different maximum temperatures of the volumetric receiver (γ=0.3)

Figure 5

ηrec and Q̇tub* as a function of the heat flux density for different surface ratios (Tvol=700°C)

Figure 6

h-s-diagram for different operation modes

Figure 7

Critical heat flux density at the inner surface of the absorber tube as a function of the steam quality with the evaporation path of the evaporation section. p=110bar, outer diameter do=50mm, wall thickness s=5mm.

Figure 8

Heat balance of the dual receiver plant with regulation stage

Figure 9

Heat balance of the reference plant applying a volumetric receiver (here with regulation stage)

Figure 10

Part load net efficiencies of all investigated systems (receiver and Rankine cycle, without heliostat field)

Figure 11

Yearly energy flows of the dual receiver concept (left) and the reference plant (right) with nozzle section (all values in GWh/a)

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