Progress in heliostat development

Abstract

Strong efforts are being made to drive heliostat cost down. These efforts are summarised to give an update on heliostat technology comprising: determination of wind loads, heliostat dimensioning, solutions for the different sub-functions of a heliostat, a review of commercially available and prototype heliostat designs, canting, manufacturing, qualification, heliostat field layout, and mirror cleaning. There is evidence that commercial heliostat costs have dropped significantly in the past few years, with commercial suppliers of heliostat technologies now claiming heliostat field costs around 100 USD/m 2. With new approaches even target cost of 75$/m² seem to be realistic.

A concise overview of heliostat fields-solar thermal collectors: Current state of art and future perspective

“…Currently, mirror cost per unit area is approximately 150 to 200 US$/ m 2. Nevertheless, it is targeted to abate the mirror cost per unit area to 75 US$/ m 2 in order to have a more economically competitive renewable energy system . Blackmon recommended to target reducing the expenses which do not dependent on the mirror size including the controller and position sensor.…”

“…Mirrors' orientations are constantly re‐adjusted by determining and minimizing the deviations from the intended target based on sun's position. The conventional controlling systems involve calibration and open‐loop control whereas use of sensors in closed‐loop control systems is the more recent approach . It should be noted that closed‐loop control systems are able to more accurately control the mirror position and reduce tracking errors which leads to lower spillage losses and a better distributed flux on the receiver aperture …”

“…It is estimated that approximately 7% of the total capital investment required for a heliostat field is associated with the control and power wiring expenses. As a result, wireless control system has been proposed which will have a considerable economic advantage . The only drawback of using wireless control system is the higher error probability due to limitation in bandwidth .…”

Optimization of a Heliostat Field Layout on Annual Basis Using a Hybrid Algorithm Combining Particle Swarm Optimization Algorithm and Genetic Algorithm

“…In Ref. [35], it pointed out that the cost of the heliostat mirror is between 150 USD/m 2 to 200 USD/m 2 in 2013, and the cost will gradually decline and may reach 75 USD/m 2 in the future. Thus, the effects of the cost of heliostat mirror collector on the heliostat field when the cost varies from 75 USD/m 2 to 175 USD/m 2 are discussed.…”

SCADA-Based Heliostat Control System with a Fuzzy Logic Controller for the Heliostat Orientation

“…However, due to the limited bandwidth in wireless communication, it is difficult to control the orientation of each heliostat from the central control with a high update rate, which increases the possibility of errors. Therefore, every local control must calculate the sun position and the aim point in order to move the heliostat to the desired position, reducing the network traffic between the central and the local control, and increasing its autonomy [14]. A SCADA system integrates the information received from the local controllers (also called remote terminal units), by using a supervisory unit (SU) embedded into a computer, in order to analyze the data, supervise the process, and make decisions by using a human-machine interface [1].…”