Cryogenic heat exchangers for process cooling and renewable energy storage: A review

© 2019 The cryogenic industry has experienced remarkable expansion in recent years. Cryogenic technologies are commonly used for industrial processes, such as air separation and natural gas liquefaction. Another recently proposed and tested cryogenic application is Liquid Air Energy Storage (LAES). This technology allows for large-scale long-duration storage of renewable energy in the power grid. One major advantage over alternative storage techniques is the possibility of efficient integration with important industrial processes, e.g., refrigerated warehousing of food and pharmaceuticals. Heat exchangers are among the most important components determining the energy efficiency of cryogenic systems. They also constitute the necessary interface between a LAES system and the industrial process utilizing the available cooling effect. The present review aims to familiarise energy professionals and stakeholders with the latest achievements, innovations, and trends in the field of cryogenic heat exchangers, with particular emphasis on their applications to LAES systems employing renewable energy resources. Important innovations in coil-wound and plate-fin heat exchanger design and simulation methods are reviewed among others, while special attention is given to regenerators as a prospective component of cryogenic energy storage systems. This review also reveals that the geographical spread of research and development activities has recently expanded from well-established centers of excellence to rather active emerging establishments around the globe

Energy mapping of large refrigerated warehouses co-located with renewable energy sources across Europe

Powering refrigerated warehouses by renewable energy sources (RES) turns from an extravagancy to a routine. RES intermittency requires suitable energy storage for both off-grid and on-grid applications. Cryogenic energy storage, integrated synergistically with RES and large refrigerated warehouses, is a promising environmentally friendly technology (addressed by the EU CryoHub project). Hence, studies were carried out to identify where large energy-intensive refrigerated warehouses are situated across Europe and how much power they consume. By employing diverse instruments and data sources, some 1049 warehouses were established, while 503 energy intensive ones were mapped and further co-located with 3200 solar PV and 11700 onshore wind parks to discover the best areas for RES integration across EU28. As compared with similar international surveys, the CryoHub statistics covers simultaneously warehouse capacity, geographical location and energy data, which permit a comprehensive analysis and strategic planning in both food refrigeration and energy sectors

Financial viability of liquid air energy storage applied to cold storage warehouses

Cold storage warehouses (CSWs) are large energy consumers and account for a significant portion of the global energy demand. CSWs are ideally suited for solar renewable energy, as they generally have large flat roofs and their peak demand can coincide with the sun shining. A challenge with fluctuating renewables is their variability,which means generation may not coincide with demand. Liquid air energy storage (LAES) is a technology that stores electrical energy as a cryogenic liquid. This paper presents twostrategies for using LAES at CSWs, firstly to shift the import of energy from peak to off-peak tariffs and secondly to store on site renewable energy when there is a surplus and use when not. The financial viability of these strategies is then investigated taking into account the capital cost of the LAES and the money that can be saved due to the differences in tariffs at different times

Assessment of methods to reduce the energy consumption of food cold stores

Energy is a major cost in the operation of food cold stores. Work has shown that considerable energy savings can be achieved in cold stores. Results from 38 cold store audits carried out across Europe are presented. Substantial savings could be achieved if operation of cold storage facilities were optimised in terms of heat loads on the rooms and the operation of the refrigeration system. Many improvements identified were low in cost (improved door protection, defrost optimisation, control settings and repairs). In large stores (>100 m3) most improvements identified were cost effective and had short payback times, whereas in small stores there were fewer energy saving options that had realistic payback times. The potential for large energy savings of at minimum 8% and at maximum 72% were identified by optimising usage of stores, repairing current equipment and by retrofitting of energy efficient equipment. Often these improvements had short payback times of less than 1 year. In each facility the options to reduce energy consumption varied. This indicated that to fully identify the maximum energy savings, recommendations need to be specific to a particular plant. General recommendations cannot fully exploit the energy savings available and therefore to maximise energy savings it is essential to monitor and analyse data from each facility. © 2013 Elsevier Ltd. All rights reserved

Initiatives to reduce energy use in cold stores

The cold chain is believed to be responsible for approximately 2.5% of global greenhouse gas emissions through direct and indirect (energy consumption) effects. Cold storage rooms consume considerable amounts of energy. Within cold storage facilities 60-70% of the electrical energy can be used for refrigeration. Therefore cold store users have considerable incentive to reduce energy consumption

Specific energy consumption values for various refrigerated food cold stores

Two benchmarking surveys were created to collect data on the performance of chilled, frozen and mixed (chilled and frozen stores operated from a single refrigeration system) food cold stores with the aim of identifying the major factors influencing energy consumption. The volume of the cold store was found to have the greatest relationship with energy use with none of the other factors collected having any significant impact on energy use. For chilled cold stores, 93% of the variation in energy was related to store volume. For frozen stores, 56% and for mixed stores, 67% of the variation in energy consumption was related to store volume. The results also demonstrated the large variability in performance of cold stores. This was investigated using a mathematical model to predict energy use under typical cold store construction, usage and efficiency scenarios. The model demonstrated that store shape factor (which had a major impact on surface area of the stores), usage and to a lesser degree ambient temperature all had an impact on energy consumption. The work provides an initial basis to compare energy performance of cold stores and indicates the areas where considerable energy saving are achievable in food cold stores. © 2013 Elsevier B.V

Refrigerated warehouses as intelligent hubs to integrate renewable energy in industrial food refrigeration and to enhance power grid sustainability

© 2016 Elsevier LtdBackground Independence from fossil fuels, energy diversification, decarbonisation and energy efficiency are key prerequisites to make a national, regional or continental economy competitive in the global marketplace. As Europe is about to generate 20% of its energy demand from Renewable Energy Sources (RES) by 2020, adequate RES integration and renewable energy storage throughout the entire food cold chain must properly be addressed. Scope and approach Refrigerated warehouses for chilled and frozen foods are large energy consumers and account for a significant portion of the global energy demand. Nevertheless, the opportunity for RES integration in the energy supply of large food storage facilities is often neglected. In situ power generation using RES permits capture of a large portion of virtually free energy, thereby reducing dramatically the running costs and carbon footprint, while enhancing the economic competitiveness. In that context, there exist promising engineering solutions to exploit various renewables in the food preservation sector, in combination with the emerging sustainability-enhancing technology of Cryogenic Energy Storage (CES). Key findings and conclusions Substantial research endeavours are driven by the noble objective to turn the Europe's Energy Union into the world's number one in renewable energies. Integrating RES, in synchrony with CES development and proper control, is capable of both strengthening the food refrigeration sector and improving dramatically the power grid balance and energy system sustainability. Hence, this article aims to familiarise stakeholders of the European and global food preservation industry with state-of-the-art knowledge, know-how, opportunities and professional achievements in the concerned field

Analyse thermophysique et solutions d'ingénierie vers la durabilité de la chaîne du froid

The thesis spotlights food refrigeration and cold chain for foods and perishable bioproducts. The work addresses innovative mathematical models, simulation and optimisation of unsteady-state heat transfer during chilling and freezing (warming and thawing) of foods and moisture-containing systems of various configurations. Attention is paid to enthalpy methods and variables’ transforms for solving highly non-linear heat transfer problems by numerical techniques. An improved enthalpy and Kirchhoff transform method is firstly introduced for the most common food refrigeration scenario of gradual non-isothermal phase changes. Predictive equations for the thermophysical characteristics, enthalpy and Kirchhoff function are established for unfrozen and frozen foods, which received an international recognition. A novel chilling and freezing method, named ‘hydrofluidisation’, is launched to bring together the advantages of both air fluidisation and immersion food freezing techniques by using unfreezable liquids or two-phase ice slurries as refrigerating media and fluidising agents. State-of-the-art engineering solutions for energy harvesting and conversion, enabling proper integration of multiple renewable energy sources in the refrigerated warehousing of foods, are conceptualised and systematised. A demand response strategy is tested for ‘passive’ storage of renewable energy in refrigerated warehouses to serve as ‘virtual batteries’ for power peak ‘shaving’, and electrical grid balancing and decarbonising, taking also into account the effect of temperature fluctuations and freeze-thaw cycles on the end product quality.La thèse met l'accent sur le froid alimentaire et la chaîne du froid pour les bioproduits périssables. Le travail porte sur des modèles mathématiques innovants du transfert de chaleur non-stationnaire pendant la réfrigération et congélation des aliments et des systèmes aqueux de diverses configurations. L'attention est portée sur méthodes enthalpiques et transformes de variables pour résoudre des problèmes de transfert de chaleur non-linéaires par des techniques numériques. Une méthode améliorée d'enthalpie et de transformation de Kirchhoff est introduite pour le scénario le plus courant des changements de phase graduels et non-isothermes. Equations prédictives pour les caractéristiques thermophysiques sont établies pour des aliments congelés et non-congelés et reconnu internationalement. Une nouvelle méthode d’"hydrofluidisation" est lancée pour réunir les avantages des techniques de fluidisation de l'air et de congélation par immersion (en utilisant des liquides non-congelables ou des coulis de glace biphasiques comme milieux refroidissants et agents de fluidisation). Solutions techniques de pointe pour la collecte et conversion de l'énergie, intégrant de multiples sources renouvelables dans l’entreposage frigorifique, sont conceptualisées. Une stratégie de réponse à la demande est testée pour le stockage "passif" de l'énergie renouvelable dans les entrepôts frigorifiques afin d'agir comme des "batteries virtuelles" pour l'écrêtement des pointes de consommation, et pour l'équilibrage et la décarbonisation du réseau électrique, en tenant également compte de l'effet des fluctuations de température et des cycles de congélation-décongélation sur la qualité du produit final