Elsevier

Applied Energy

Volume 104, April 2013, Pages 538-553
Applied Energy

A review of solar collectors and thermal energy storage in solar thermal applications

https://doi.org/10.1016/j.apenergy.2012.11.051Get rights and content

Abstract

Thermal applications are drawing increasing attention in the solar energy research field, due to their high performance in energy storage density and energy conversion efficiency. In these applications, solar collectors and thermal energy storage systems are the two core components. This paper focuses on the latest developments and advances in solar thermal applications, providing a review of solar collectors and thermal energy storage systems. Various types of solar collectors are reviewed and discussed, including both non-concentrating collectors (low temperature applications) and concentrating collectors (high temperature applications). These are studied in terms of optical optimisation, heat loss reduction, heat recuperation enhancement and different sun-tracking mechanisms. Various types of thermal energy storage systems are also reviewed and discussed, including sensible heat storage, latent heat storage, chemical storage and cascaded storage. They are studied in terms of design criteria, material selection and different heat transfer enhancement technologies. Last but not least, existing and future solar power stations are overviewed.

Highlights

► The latest developments in solar thermal applications are reviewed. ► Various types of solar collectors are summarised. ► Thermal energy storage approaches and systems are discussed. ► The current status of existing solar power stations is reviewed.

Introduction

CO2-induced global warming has become a pressing issue, and needs to be tackled. Efficient utilisation of renewable energy resources, especially solar energy, is increasingly being considered as a promising solution to global warming and a means of achieving a sustainable development for human beings. The Sun releases an enormous amount of radiation energy to its surroundings: 174 PW (1 PW = 1015 W) at the upper atmosphere of the Earth [1]. When the energy arrives at the surface of the Earth, it has been attenuated twice by both the atmosphere (6% by reflection and 16% by absorption [1]) and the clouds (20% by reflection and 3% by absorption [1]), as shown in Fig. 1 [2]. Another 51% (89 PW) of the total incoming solar radiation reaches the land and the oceans [1]. It is evident that, despite the attenuation, the total amount of solar energy available on the Earth is still of an enormous amount, but because it is of low-density and intermittency, it needs to be collected and stored efficiently.

Solar collectors and thermal energy storage components are the two kernel subsystems in solar thermal applications. Solar collectors need to have good optical performance (absorbing as much heat as possible) [3], whilst the thermal storage subsystems require high thermal storage density (small volume and low construction cost), excellent heat transfer rate (absorb and release heat at the required speed) and good long-term durability [4], [5]. In 2004, Kalogirou [6] reviewed several different types of solar thermal collectors that were in common use, and provided relative thermal analyses and practical applications of each type. However, the technologies involved in solar collectors have been much improved since that review was published, so that some of the latest collectors, such as PVT (Photovoltaic-Thermal) collectors, were not available in time for inclusion in [6]. These latest technologies are described in Section 2 of the present paper. In addition, most of existing review-type literature on thermal energy storage has been mainly restricted to low-temperature applications [4], [5], [7], [8], [9]. There are only a few papers addressing high-temperature thermal energy storage applications. These include Kenisarin [10], who reviewed a group of potential phase change materials (PCMs) used from 120 °C to 1000 °C, and provided their thermal properties and Gil et al. [11], who reviewed the high-temperature thermal storage systems especially for power generation; they also listed desirable materials and thermal models that can be used. Updates of the latest developments in high-temperature thermal storage technologies are given in Section 3 of the present paper.

This paper provides a review of various solar collectors and thermal storage methods, and is organised as follows:

  • Solar collectors: non-concentrating collectors; concentrating collectors.

  • High-temperature thermal energy storage: design criteria; materials, heat transfer enhancement technologies.

  • An overview of existing and future solar power stations.

Section snippets

Solar collectors

A solar collector, the special energy exchanger, converts solar irradiation energy either to the thermal energy of the working fluid in solar thermal applications, or to the electric energy directly in PV (Photovoltaic) applications. For solar thermal applications, solar irradiation is absorbed by a solar collector as heat which is then transferred to its working fluid (air, water or oil). The heat carried by the working fluid can be used to either provide domestic hot water/heating, or to

Solar thermal energy storage

After the thermal energy is collected by solar collectors, it needs to be efficiently stored when later needed for a release. Thus, it becomes of great importance to design an efficient energy storage system. Section 3 of the present paper focuses on the solar thermal energy storage, discussing its design criteria, desirable materials and emerging technologies for heat transfer enhancement.

Existing solar power stations

Spain has the most solar thermal power installations in the World, with the U.S. ranked the second. As shown in Table 7, most of existing solar power stations (71.0%) use parabolic troughs to harvest solar energy, as it is a relatively mature technology compared to other technologies discussed in Section 2.2, such as central solar towers (12.9%), parabolic dishes (3.2%) and Fresnel reflectors (12.9%). The installed capacity for each power station ranges from 0.25 MW to 354 MW, and the overall

Conclusions

This paper has reviewed the state of the art on solar thermal applications, with the focus on the two core subsystems: solar collectors and thermal energy storage subsystems.

A variety of solar collectors have been discussed, including non-concentrating types and concentrating types. Among non-concentrating collectors, the PVT solar collectors show the best overall performance. Sun-tracking concentrating solar collectors have also been examined, in terms of optical optimisation, heat loss

Acknowledgments

This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC Grant No: EP/F061439/1), National Basic Research Programme of China (973 Project: 2013CB228303) and the National Natural Science Foundation of China (NSFC Grant No: 51176110). The authors also gratefully acknowledge the valuable support by Professor Keith Richard Godfrey from University of Warwick in United Kingdom.

References (161)

  • P. Konttinen et al.

    Mechanically manufactured selective solar absorber surfaces

    Sol Energy Mat Sol C

    (2003)
  • M. Slaman et al.

    Solar collector overheating protection

    Sol Energy

    (2009)
  • A.A. Lambert et al.

    Enhanced heat transfer using oscillatory flows in solar collectors

    Sol Energy

    (2006)
  • C.D. Ho et al.

    Heat-transfer enhancement in double-pass flat-plate solar air heaters with recycle

    Energy

    (2005)
  • K. Sopian et al.

    Evaluation of thermal efficiency of double-pass solar collector with porous–nonporous media

    Renew Energy

    (2009)
  • G. Martinopoulos et al.

    CFD modeling of a polymer solar collector

    Renew Energy

    (2010)
  • Y. Tian et al.

    A numerical investigation of heat transfer in phase change materials (PCMs) embedded in porous metals

    Energy

    (2011)
  • C.Y. Zhao et al.

    Heat transfer enhancement for thermal energy storage using metal foams embedded within phase change materials (PCMs)

    Sol Energy

    (2010)
  • S.K. Saha et al.

    Thermodynamic optimization of solar flat-plate collector

    Renew Energy

    (2001)
  • S. Farahat et al.

    Exergetic optimization of flat plate solar collectors

    Renew Energy

    (2009)
  • M. Selmi et al.

    Validation of CFD simulation for flat plate solar energy collector

    Renew Energy

    (2008)
  • N. Aste et al.

    Design, development and performance monitoring of a photovoltaic-thermal (PVT) air collector

    Renew Energy

    (2008)
  • T. Bergene et al.

    Model calculations on a flat-plate solar heat collector with integrated solar cells

    Sol Energy

    (1995)
  • S.A. Kalogirou

    Use of TRNSYS for modelling and simulation of a hybrid PV-thermal solar system for Cyprus

    Renew Energy

    (2001)
  • J. Prakash

    Transient analysis of a photovoltaic thermal solar collector for co-generation of electricity and hot air water

    Energy Convers Manage

    (1994)
  • R.K. Agarwal et al.

    Study of a photovoltaic thermal system––thermosyphonic solar water heater combined with solar cells

    Energy Convers Manage

    (1994)
  • J.K. Tonui et al.

    Improved PV/T solar collectors with heat extraction by forced or natural air circulation

    Renew Energy

    (2007)
  • A.A. Hegazy

    Comparative study of the performances of four photovoltaic/thermal solar air collectors

    Energy Convers Manage

    (2000)
  • H.P. Garg et al.

    Conventional hybrid photovoltaic/thermal (PV/T) air heating collectors: steady-state simulation

    Renew Energy

    (1997)
  • T. Fujisawa et al.

    Annual exergy evaluation on photovoltaic–thermal hybrid collector

    Sol Energy Mat Sol C

    (1997)
  • B.J. Huang et al.

    Performance evaluation of solar photovoltaic/thermal systems

    Sol Energy

    (2001)
  • H.A. Zondag et al.

    The thermal and electrical yield of a PV-thermal collector

    Sol Energy

    (2002)
  • A.S. Joshi et al.

    Energy and exergy efficiencies of a hybrid photovoltaic–thermal (PV/T) air collector

    Renew Energy

    (2007)
  • G.M. Tina et al.

    Optical and thermal behavior of submerged photovoltaic solar panel: SP2

    Energy

    (2012)
  • B. Robles-Ocampo et al.

    Photovoltaic/thermal solar hybrid system with bifacial PV module and transparent plane collector

    Sol Energy Mat Sol C

    (2007)
  • X.D. Wei et al.

    A new method for the design of the heliostat field layout for solar tower power plant

    Renew Energy

    (2010)
  • M. Medrano et al.

    State of the art on high-temperature thermal energy storage for power generation. Part 2—Case studies

    Renew Sust Energy Rev

    (2010)
  • A.R. Tavakolpour et al.

    Simulation, construction and testing of a two-cylinder solar Stirling engine powered by a flat-plate solar collector without regenerator

    Renew Energy

    (2008)
  • Y. Zhang et al.

    Optimum performance characteristics of an irreversible solar-driven Brayton heat engine at the maximum overall efficiency

    Renew Energy

    (2007)
  • G.C. Bakos

    Design and construction of a two-axis Sun tracking system for parabolic trough collector (PTC) efficiency improvement

    Renew Energy

    (2006)
  • S. Abdallah

    The effect of using sun tracking systems on the voltage–current characteristics and power generation of flat plate photovoltaics

    Energy Convers Manage

    (2004)
  • M. Kacira et al.

    Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey

    Renew Energy

    (2004)
  • J.D. Mondol et al.

    The impact of array inclination and orientation on the performance of a grid-connected photovoltaic system

    Renew Energy

    (2007)
  • C.Y. Zhao et al.

    Thermal property characterization of a low melting-temperature ternary nitrate salt mixture for thermal energy storage systems

    Sol Energy Mat Sol C

    (2011)
  • T. Wang et al.

    Novel low melting point quaternary eutectic system for solar thermal energy storage

    Appl Energy

    (2013)
  • A. Steinfeld et al.

    Design aspects of solar thermochemical engineering – a case study: two-step water splitting cycle using Fe3O4/FeO re-dox system

    Sol Energy

    (1999)
  • E.S. Mettawee et al.

    Thermal conductivity enhancement in a Latent Heat Storage System

    Sol Energy

    (2007)
  • U. Stritih

    An experimental study of enhanced heat transfer in rectangular PCM thermal storage

    Int J Heat Mass Trans

    (2004)
  • X. Py et al.

    Paraffin/porous-graphite-matrix composite as a high and constant power thermal storage material

    Int J Heat Mass Trans

    (2001)
  • K. Nakaso et al.

    Extension of heat transfer area using carbon fiber cloths in latent heat thermal energy storage tanks

    Chem Eng Process: Process Intensif

    (2008)
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