• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.41-51
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• 2012

Heliostat field is the most important subsystem in the tower type solar thermal power plant since its optical performance affects the total system efficiency most significantly while the construction cost of it is the major part of total construction cost in such a power plant. Thus a well designed heliostat field to maximize the optical efficiency as well as to minimize the land usage is very important. This work presents methodology, procedures and result of heliostat filed design for 200kW solar thermal power plant built recently in Daegu, Korea. A $2{\times}2(m)$ rectangular shaped receiver located at 43(m) high and tilted $28^{\circ}$ toward heliostat field, 450 of heliostats of which the reflective surface is formed by 4 of $1{\times}1(m)$ flat plate mirror facet, and the land area having about $140{\times}120(m)$ size are used to form the heliostat field. A procedure to deploy 450 heliostats in radial staggered nonblocking formation is developed. Also the procedures to compute the cosine effect, intercept ratio, blocking and shading ratio in the field are developed. Finally the heliostat filed is designed by finding the optimal radial distance and azimuthal spacing in radial staggered nonblocking formation such that the designed heliostat field optical efficiency could be maximized. The designed heliostat field has 77% of annual average optical efficiency, which is obtained by annually averaging the optical efficiencies computed between the time of where sun elevation angle becomes $10^{\circ}$ after sunrise and the time of where sun elevation angle becomes $10^{\circ}$ before sunset in each day.

• 한국태양에너지학회 논문집
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• 제34권3호
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• pp.21-29
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• 2014

Heliostat field control algorithm is the logics to operate the heliostat field of tower type solar thermal power plant and it could include various methodologies of how to control the heliostat field so as to optimize the energy collection efficiency as well as to reduce the system operating cost. This work, as the first part of the consecutive works, presents heliostat aiming mint allocation scheme which will be used in the heliostat field control algorithm for 200kW solar thermal power plant built in Daegu, Korea. We first discuss the structure of heliostat field control system required for the implementation of aiming scheme developed in this work. Then the methodologies to allocate the heliostat aiming points on the receiver are discussed. The simulated results show that the heliostat aiming point allocation scheme proposed in this work reduces the magnitude of peak heat flux on the receiver more than 40% from the case of which all the heliostats in the field aim at the center of receiver simultaneously. Also it shows that, when the proposed scheme is used, the degradation of heliostat field optical efficiency is relatively small from the maximal optical efficiency the heliostat field could have.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.33-41
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• 2014

Heliostat field in a tower type solar thermal power plant is the sun tracking mirror system which affects the overall efficiency of solar thermal power plant most significantly while consumes a large amount of energy to operate it. Thus optimal operation of it is very crucial for maximizing the energy collection and, at the same time, for minimizing the operating cost. Heliostat field operational algorithm is the logics to control the heliostat field efficiently so as to optimize the heliostat field optical efficiency and to protect the system from damage as well as to reduce the energy consumption required to operate the field. This work presents the heliostat field operational algorithm developed for the heliostat field of 200kW solar thermal power plant built in Daegu, Korea. We first review the structure of heliostat field control system proposed in the previous work to provide the conceptual framework of how the algorithm developed in this work could be implemented. Then the methodologies to operate the heliostat field properly and efficiently, by defining and explaining the various operation modes, are discussed. A simulation, showing the heat flux distribution collected by the heliostat field at the receiver, is used to show the usefulness of proposed heliostat field operational algorithm.

• 한국태양에너지학회 논문집
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• 제31권3호
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• pp.80-88
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• 2011

Heliostat in the tower type solar thermal power plant is a sun tracking mirror system to reflect the solar energy to the receiver and the optical performance of it affects to the efficiency of whole power plant most significantly. Thus a solid understanding of heliostat's energy concentration characteristics is the most important step in designing of the heliostat field and the whole power plant. The work presented here is the analysis of energy concentration characteristics of heliostat used in 200kW solar thermal power plant, where the receiver located at 43m high in tower has $2{\times}2$m rectangular shape. The heliostat reflective surface is formed by 4 of $1{\times}1$m flat plate mirror facet and the mirror facet is mounted on the spherical frame. The direct normal incident radiation models in vernal equinox, summer solstice, autumnal equinox and winter solstice are first derived from the actually measured data. Then the intercept ratio, heat flux distribution and total energy collected at the receiver for the heliostats located in the various places of the heliostat field are investigated. Finally the effect of mirror facet installation error on the optical performance of the heliostat is analyzed.