Review on system and materials requirements for high temperature thermal energy storage. Part 1: General requirements

High temperature thermal energy storage offers a huge energy saving potential in industrial applications such as solar energy, automotive, heating and cooling, and industrial waste heat recovery. However, certain requirements need to be faced in order to ensure an optimal performance, and to further achieve widespread deployment. In the present review, these requirements are identified for high temperature (>150 °C) thermal energy storage systems and materials (both sensible and latent), and the scientific studies carried out meeting them are reviewed. Currently, there is a lack of data in the literature analysing thermal energy storage from both the systems and materials point of view. In the part 1 of this review more than 25 requirements have been found and classified into chemical, kinetic, physical and thermal (from the material point of view), and environmental, economic and technologic (form both the material and system point of view). The enhancements focused on the thermal conductivity are addressed in the Part 2 of this review due to their research significance and extension.The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R, ENE2011-22722 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement No. PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2016FI_B 00047)

Estimating the industrial waste heat recovery potential based on CO2 emissions in the European non-metallic mineral industry

Industrial waste heat (IWH) is a key strategy to improve energy efficiency and reduce CO2 emissions in the industry. But its potential for different countries remains unclear due to a non-existent or inconsistent data basis. The objective of this paper is to assess the IWH potential of the European non-metallic mineral industry, using databases which comprise CO2 emissions of more than 400 industrial sites as well as country- and sector-specific parameters. This sector is selected because of its homogenous nature, meaning that most sites carry out similar or the same processes, which facilitates site-level modelling with subsector-level assumptions. The bottom-up approach is employed to derive the IWH potential for this industry over the period 2007–2012. Average results in this period show an IWH potential per site of 0.33 PJ/a and a potential for the whole sector of 134 PJ/a. The countries with the largest IWH potentials are Germany, Italy, France and Spain with yearly average potentials of 23, 19, 17 and 16 PJ, respectively. The subsector with the most IWH potential is cement. Further work should focus on the improvement of methodologies to assess the IWH potential, in particular through a techno-economic assessment of links between IWH sources and potential sinks.The work is partially funded by the Spanish Government (ENE2015-64117-C5-1-R (MINECO/FEDER)). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant Agreement No PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 657466 (INPATH-TES)

Methodologies to estimate industrial waste heat potential by transferring key figures: a case study for Spain

In the current European energy context, the use of recovered industrial waste heat provides an attractive opportunity to substitute primary energy consumption by a low-emission and low-cost energy carrier. In the case of industrial waste heat, this potential is currently not only largely untapped, but also unaccounted for. In order to achieve a widespread use of recovered industrial waste heat, assessments with a large scope and high spatial resolution are needed. Three methods published in the period 2002–2010 have been found in the literature, which are potentially transferable to other regions. These three methods are based on either the energy consumption of each manufacturing sector or the individual site CO2 emissions. The scope of this analysis is, first, to investigate in how far a transfer of the figures to different countries or regions is sensible in comparison to former studies in the literature. In the process, some uncertainties when transferring methods were identified (different definitions of industry, different standard industrial activities classifications or no standard at all, etc.). The second goal is, once the methodology is accepted, to apply it to a case study, in this case the industrial sector in Spain and two of its counties (Catalonia and the Basque Country) for the years 2001, 2009, 2010 and 2013. In this period, and based on the different approaches employed, the Spanish annual industrial waste heat potential ranges from 54.3 to 151.1 PJ, Catalonia from 8.6 to 29.7 PJ, and from 7.2 to 11.9 PJ for the Basque Country. The methods are considered highly transferable but uncertainties inevitably arise in the case that the source and destination industrial sectors are very different.The work is partially funded by the Spanish government (ENE2011-22722 and ULLE10-4E-1305) and by BMWi Federal Ministry for Economic Affairs and Energy in Germany (Project FKZ 0327383B Mobile Sorption Heat Storage). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement N°PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861)

Materials and system requirements of high temperature thermal energy storage systems: A review. Part 2: thermal conductivity enhancement techniques

This review is focused on the study of the requirement of high thermal conductivity of thermal energy storage (TES) materials and the techniques used to enhance it as this is one of the main obstacles to achieve full deployment of TES systems. Numerical and experimental studies involving different thermal conductivity enhancement techniques at high temperature (>150 °C) are reviewed and classified. This article complements Part 1, which reviews the different requirements that TES materials and systems should consider for being used for high temperature purposes and the approaches to satisfy them. The enhancements identified for this temperature range are the addition of extended surfaces like fins or heat pipes and the combination of highly conductive materials with TES material like graphite or metal foam composites and nanomaterials. Moreover the techniques presented are classified and discussed taking into account their research evolution in terms of maturity and publications.The work is partially funded by the Spanish Government (ENE2011-22722 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). The research leading to these results has received funding from the European Union׳s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861)

Industrial waste heat: mapping, estimations and recovery by means of TES

En l’actual context energètic, l'ús de la calor residual industrial (CRI) representa una oportunitat atractiva de substituir el consum d'energia primària per un mitjà amb baix nivell d'emissions i baix cost. Aquesta calor es pot recuperar i reutilitzar en altres processos, ser transformada en electricitat o calor.Tot i el seu prometedor potencial, aquest CRI no s’utilitza. L'objectiu d'aquesta tesi doctoral és el de superar algunes de les barreres tecnològiques i d'informació actuals que dificulten l’ús d’aquesta fot d’energia. En primer lloc, s’ha identificat el potencial mundial actual de CRI a escala de. En segon lloc, es va generar noves avaluacions d’estimació del potencial de CRI: a la indústria de la manufactura espanyola i en la indústria de minerals no metàl•lics Europea. Finalment, es va tractar la recuperació i reutilització d'aquesta calor mitjançant l’emmagatzematge d’energia tèrmica i es va avaluar exhaustivament els casos pràctics on aquesta tecnologia ha estat implementada.En el actual contexto energético, el uso del calor residual industrial (CRI) representa una oportunidad atractiva de sustituir el consumo de energía primaria por un medio de bajo nivel de emisiones y de bajo coste. Este calor se puede recuperar y reutilizar en otros procesos, ser transformado en electricidad o en calor. A pesar de su prometedor potencial, este CRI está actualmente en desuso. El objetivo de esta tesis doctoral es el de superar algunas de las barreras tecnológicas y de información que existen actualmente en la utilización de esta fuente de energía. En primer lugar, se ha identificado el potencial mundial actual de CRI a escala de país. En segundo lugar, se generaron nuevas evaluaciones de estimación del potencial de CRI: en la industria de la manufactura española y en la industria de minerales no metálicos Europea. Finalmente, se trató la recuperación y reutilización de este calor mediante almacenamiento de energía térmica y se evaluó exhaustivamente los casos prácticos donde esta tecnología ha sido implementada.In the current energy context, the use of industrial waste heat (IWH) provides an attractive opportunity to substitute primary energy consumption by a low-emission and low-cost energy carrier. Despite its potential, IWH is largely untapped. This heat can be recovered and reused in other processes, transformed into electricity or heat. The aim of this PhD is to overcome some of the current technological and information barriers and to provide the literature and the researchers with more knowledge of the topic and supporting its widespread development. First, current IWH potential worldwide at country scale was identified. Second, new assessments to estimate the regional IWH potential were generated: in the Spanish manufacture industry as well as in the European non-metallic mineral industry. Finally, its reuse by means of thermal energy storage (TES) was analysed and an exhaustive research of current case studies was performed

Temperature distribution and heat losses in molten salts tanks for CSP plants

Solar power plants have been deployed in the last 20 years, so the interest in evaluating their performance is growing more and more. In these facilities, thermal energy storage is used to increase dispatchability of power. The two-tank molten salts storage system with “solar salt” (60 wt.% NaNO3 and 40 wt.% KNO3) is the one commercially used today. To be able to achieve a deep understanding of the two-tank solar storage systems with molten salts, in 2008 a pilot plant was built at the University of Lleida (Spain) and the experimental evaluation of the temperature distribution inside the tanks and their heat losses are presented in this paper. Therefore, this pilot plant is equipped with several temperature sensors inside the tank as well as in the different layers of external insulation. As expected, temperature is lower at the external part of the tank (near the cover, at the bottom and near the walls) and no stratification is seen. It is found that the influencing parameters in the temperature distribution of the salts inside the tank are: insulation, and the existence of different electrical resistances and the orientation and surroundings of the tank. Heat losses were measured and compared both with a simulated 1-D steady state model and previous literature. Measured heat losses were from 61 W/m2 through the bottom to 80 W/m2 through the walls (with 73 W/m2 through the cover).The research leading to these results has received funding from Spanish goverment (Fondo tecnológico IDI-20090393, ConSOLida CENIT 2008-1005) and from Abengoa Solar NT. The work is partially funded by the Spanish government (ENE2008-06687-C02-01/CON, ENE2011-22722, ENE2015-64117-C5-1-R, and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement N° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861)