Renewable Energy Global Innovations features: Multiscale modeling and performance analysis of evacuated tube collectors for solar water heaters using diffuse flat reflector

Significance Statement

The deployment rate of solar water heaters (SWHs) is rapidly increasing for various domestic, industrial and commercial applications. Among stationary solar collectors, evacuated tube collectors (ETCs) have captivated more attention because of their satisfactory performance, reliability and cost-effectiveness.

However, using ETCs for various solar water heaters may endure deficits in collecting the necessary thermal energy for water heating particularly in cold seasons. This is because of the cylindrical shape of evacuated tubes which makes the upper circumference of the cylinder is directly exposed to sunrays, while the lower circumference usually misses the beam and also most of the diffuse irradiance.

This study highlights the role of installing a diffuse flat reflector (DFR) layer at the back of ETC array to improve heat capture rate. A comprehensive and generic model in computing solar thermal gain, annual fuel/electricity savings, and small-scale technology certificates (STCs) is developed. While this model is optimized for a promising energy saving compared to the conventional ETC-SWHs in four Australian solar zones, it can be custom-designed for any thermal load at any location worldwide.

This model is able to optimize the azimuth/tilt angles and be sized for the highest annual/seasonal achievable performance. The outcome of this research demonstrates a tangible techno-economic feasibility for many solar water heaters applications. 

About The Author

Dr Dia Milani is currently the energy team leader in the Laboratory for Multiscale Systems (LMS) at the University of Sydney. He obtained a M.S. degree in Environmental Engineering Management from UTS in 2006, a Graduate Certificate in Innovation & Enterprise in 2011, and PhD in Chemical Engineering in 2012 from The University of Sydney.

His research focus is at the water-energy-carbon interfaces with primary emphasis on novel technologies in renewable energy, thermal energy storage, carbon capture, CO₂ utilization, waste management, and solar-assisted power cycles.

About The Author

Associate Professor Ali Abbas received both his Bachelors and PhD in Chemical Engineering from University of Sydney, Australia. He has held academic appointments at Nanyang Technological University (NTU), and UNSW Asia in Singapore before joining, in 2007, the School of Chemical and Biomolecular Engineering at the University of Sydney. His engineering research and expertise is in the area of Process Systems Engineering with emphasis on model-based optimal operation of energy, particulate and bio-systems.

In 2008, A/Prof. Abbas was awarded the PSE Model-based innovation prize (London, UK) recognizing his work in model-based optimal process operations. He was later awarded the Australia-Harvard Fellowship in 2011 as well as the Academy of Technological Sciences and Engineering (ATSE) Fellowship (Australia-China Future Leader in Clean Coal Technologies) in 2012.

He has strong interests in engineering science education with particular focus on curriculum design and integration as well as on experiential e-learning and virtual worlds.

Journal Reference

Renewable Energy, Volume 86, 2016, Pages 360-374.

Dia Milani, Ali Abbas

School of Chemical and Biomolecular Engineering, The University of Sydney, NSW 2006, Australia

Abstract

Using evacuated tube collectors (ETCs) in solar water heaters (SWHs) may endure deficiencies (i.e. in winter season) in collecting the necessary thermal energy for water heating. This is because of the cylindrical shape of evacuated tubes which makes the upper circumference of the cylinder is directly exposed to sunrays, while the lower circumference usually misses the beam and also most of the diffuse irradiance.

In this paper, the role of using a diffuse flat reflector (DFR) at the back of ETC array to improve heat capture rate is examined. A comprehensive model to estimate the annual energy savings and small-scale technology certificates (STCs) is developed. This model is applied on four major Australian cities representing four Australian solar zones. The tilt and azimuth angles for these four zones are optimized.

This optimal setting along with DFR presence could improve the STC entitlements by 14.6% for zone 1; 20.2% for zone 2; 25.9% for zone 3; and 27.9% for zone 4, respectively. This specific-tailored model may increase the annual energy saving up to 95.8% for zone 1; 91.3% for zone 2; 81% for zone 3; and 74% for zone 4 correspondingly.

Go To Renewable Energy

 

Read more research excellence studies on: Renewable Energy Global Innovations (http://ift.tt/21cCPA4)