Optimization of Commercial Linear Fresnel Product Using Numerical SimulationsTing Chi1; Guangdong Zhu, PhD2;

1The Pennsylvania State University, 2The National Renewable Energy Laboratory

This work was supported by the U.S Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

Introduction

A comprehensive survey was carried out to explore the state-of-the-art technologies. Four linear Fresnel products were selected for comparison and investigation.

Survey State-of-the-Art Technologies

Results and Discussion

Conclusion: This study indicates that non-uniform mirror spacing leads to better performance in linear Fresnel collectors. There is more room for efficiency improvement when the mirror rows are divided into more zones for non-uniform mirror spacing design.

Future work: Future work will focus on optimizing annual efficiency by developing a third scenario, which will use 8 dividing zones. Further, codes will also be updated on Matlab so that the evaluation process will be faster and more accurate.

Conclusions & Future work

Background

Concentrated Solar Power (CSP) has rapidly developed in recent years. Linear Fresnel is one viable technologies of CSP, and has great potential to become the most popular CSP technologies due to:

• Efficient land occupancy• Potential lower cost of energy• Direct steam generation• High modularity

Performance basicsOptical performance varies with incidence angle due to cosine loss, shading, blocking. Factors including geometry and optics of the collector and sun shape can affect optical efficiency.

Project goal

Methodology to Optimize Collector

NREL is a national laboratory of the U. S. Department of Energy, Office of Energy Efficiencyand Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

This project is focused on using a newly developed analytical approach (First OPTIC) to simulate a selected commercial linear Fresnel product and redesign the product with non-uniform mirror spacing to reach higher optical efficiency.

Establish baseline

Reproduce product performance

Update codes

Optimize model

IMPORT WEATHER DATA FROM ANY

LOCATION

CONVERT SUN POSITION TO

INCIDENCE ANGLE

WRITE CODES FOR CALCULATING

ANNUAL EFFICIENCY

Reason for selection: Fresdemo collector was selected due to the completeness of its product information and high optical performance.

Technical data summary:

Uniform Mirror spacing 0.85 m Receiver height 8 mNumber of mirror rows 25 Individual mirror width 0.6 mSecondary aperture width 0.3 m Collector filed width 21 m

Figure1. schematics of linear Fresnel collector [1]

Figure 3. Existing linear Fresnel products, name of the products from left to right are: Nova-1, Industrial solar LF-11, Fresdemo, Augustine.

Figure 4. Simulated product model, left: longitudinal, right: transversal

First scenario: divides the left side of collector mirror rows into 2 zones. With fixed total zone length, each zone was assigned new mirror spacing that was either increased or decreased compared to the original.

-8 -6 -4 -2 0 2 4 6 8x (m)

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Linear Fresnel Collector Collector Geometry

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-8 -6 -4 -2 0 2 4 6 8x (m)

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Linear Fresnel Collector Collector Geometry

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Second scenario: divides the left side of collector mirror rows into 4 zones. The most optimal fixed total zone length was derived from first scenario. Second scenario repeated the same methodology twice.

Absorber

Mirror Spacing

Origin

Zone 1 Zone 2 Zone 3 Zone 4

Data interpretationComparison of two scenarios1. Most non-uniform mirror

spacing showed higher annual efficiency than original uniform spacing.

2. Scenario 2 with 4 zones had better performance than first scenario.

3. Peak performance showed improvement by 0.3% when compared to original design.

4. Large mirror spacing decreased performance.

Figure 5. Annual optical efficiency vs changes to mirror spacing

AcknowledgementI would first like to thank Dr. Zhu Guangdong for designing this research project and his guidance to achieve project goal. Furthermore, I would also like to thank NREL education program for providing and organizing this internship program.

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Zone #New mirror spacing

Zone 1 0.96 mZone 2 0.84 m

Zone 3 0.86 mZone 4 0.74 m

New product

Figure 6. New product’s mirror spacing geometry

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[1] IEA. Technology roadmap – concentrating solar power. 2010;

Figure 2. Factors affecting optical performance Equation used