An error propagation model of a heliostat.

Zheng, Xiao (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Concentrating solar power plants are becoming a viable option to produce renewable electricity. However, these plants are still a relative new technology and are more expensive than traditional coal fired power plants. Currently many research groups are looking into ways that will make these plants more efficient and cheaper. A concentrating solar power plant type that seems promising at the moment, is the central tower with receiver type. This type of plant consists of a field of thousands of mirrors or heliostats that reflect solar rays onto the central receiver. The heliostat field is expensive and a lot of effort is going into reducing its cost. Heliostats have to reflect solar rays onto the central receiver with great accuracy. Most heliostats are controlled in an open-loop fashion, which requires a very accurate and calibrated model of each heliostat. There is a need to better understand the relationship between calibration errors and tracking accuracy. Such an understanding can help engineers to focus on those aspects of the heliostat that most affect the tracking accuracy. This work uses a common heliostat model that consists of eight parameters. It applies the error propagation law to the model in order to derive an error model of a heliostat. With the error model, it is possible analyses the relationship between calibration errors and tracking accuracy.

AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag aanlegte is besig om ’n lewensvatbare opsie te word om hernubare elektrisiteit op te wek. Tog is hierdie aanlegte nog steeds ’n relatief nuwe tegnologie en is duurder as tradisionele steenkoolkragstasies. Tans is daar verskeie navorsingsgroepe wat maniere ondersoek om hierdie aanlegte meer doeltreffend en goedkoper te maak. ’n Gekonsentreerde sonkrag aanleg tipe wat op die oomblik belowend is, is die sentrale toring met ontvanger tipe. Hierdie tipe aanleg bestaan ??uit ’n veld van duisende spieëls of heliostate wat son strale na die sentrale ontvanger weerkaars. Die heliostaat veld is duur en ’n baie moeite gaan daarin om dit goedkoper te maak. Heliostate moet son strale na die sentrale ontvanger weerkaats met hoë akkuraatheid. Die meeste heliostate word beheer in ’n oop-lus, wat dit nodig maak vir ’n baie akkurate en gekalibreer model van elke heliostaat. Daar is ’n behoefte om beter te verstaan wat ??die verhouding is tussen kalibrasie foute en volgingsakkuraatheid. ’n Beter begrip hiervan kan ingenieurs help om te fokus op daardie aspekte van die heliostaat wat die meeste invloed het op die volgingsakkuraatheid. Hierdie werk maak gebruik van ’n algemene heliostaat model wat bestaan uit agt parameters. Dit pas die fout voortplantingswet op die model toe om ’n foutmodel van ’n heliostaat af te lei. Met die foutmodel, is dit moontlik om die verhouding tussen kalibrasie foute en volgingsakkuraatheid te analiseer.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101249
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