Research Papers

Evaluation of Annual Performance of 2-Tank and Thermocline Thermal Storage Systems for Trough Plants

[+] Author and Article Information
Gregory J. Kolb

 Distinguished Member of Technical Staff, Sandia National Laboratories, MS1127, Albuquerque, NM 87185gjkolb@sandia.gov

The hourly DNI values were used at each 3-min time step. No interpolation was performed.

Andasol is predicted to operate 3589 full load hours with 12% from fossil. Thus, solar-only performance = 0.88 × 49.9 MWe  × 3589 = 157.6 GWh.

A small salt thermocline (2.3 MWh) was also tested at Sandia [9]. However, the dimensions of the Solar One tank are more representative of a commercial system.

J. Sol. Energy Eng 133(3), 031023 (Aug 17, 2011) (5 pages) doi:10.1115/1.4004239 History: Received January 03, 2011; Revised April 07, 2011; Published August 17, 2011; Online August 17, 2011

A study was performed to compare the annual performance of 50 MWe Andasol-like trough plants that employ either a 2-tank or a thermocline-type molten-salt thermal storage system. trnsys software was used to create the plant models and to perform the annual simulations. The annual performance of each plant was found to be nearly identical in the base-case comparison. The reason that the thermocline exhibited nearly the same performance is primarily due to the ability of many trough power blocks to operate at a temperature that is significantly below the design point. However, if temperatures close to the design point are required, the performance of the 2-tank plant would be significantly better than the thermocline.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Andasol-type parabolic trough plant

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Figure 2

TRNSYS model of an Andasol-type power plant with 2-tank storage

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Figure 3

Empirical model of a 50 MWe steam-Rankine power block

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Figure 4

Andasol-type plant with a 1000 MWh thermocline storage system. The single tank is 12.2 m tall and 46.3 m diameter.

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Figure 5

TRNSYS model of thermocline storage system. The void fraction of the tank is assumed to be 24% based on experience at the Solar One thermocline tank. The density of the rock is 1940 kg/m3 and the specific heat is 880 J/kg-C.

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Figure 6

Prediction of temperature profile throughout the thermocline tank on days near the summer solstice. Node N23 is at the bottom of the tank and node N4 is near the top.




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