Unlocking the Heat Recovery Potential of Food Retail Stores

Abstract

Due to their high energy and refrigerant use, food retail stores have attracted interest from researchers for a long time. Food retail stores use about 3-4% of the yearly produced electricity in industrialized countries and have among the highest energy uses per service area among commercial buildings. Up to 5% of the electricity is used by the refrigeration system. By leakage, the substantial amount of refrigerant used in food retail stores is also causing significant direct carbon emissions. Fluorinated carbon refrigerants are still widely in use today, but due to their high global warming potential, they are being phased out under various regulations (F-gas in the EU) and replaced with more sustainable alternatives. CO₂ as a refrigerant for commercial refrigeration is a common low-GWP choice and the CO₂ booster system is the standard for new installations in Scandinavian food retail stores today. The CO₂ system has been shown to have high technical performance and it can be modified to recover heat and provide air conditioning at efficiencies higher than, or comparable to, those of conventional heat pumps.

A CO₂ refrigeration system can consequently be modified to satisfy all thermal demands in food retail stores, and there is often a possibility to export surplus heat or air conditioning to other actors in the same or neighboring buildings. Based on field measurements, computer modeling, and simulations, this thesis evaluates the techno-economic outcome of heat recovery in a number of Swedish case studies. The Swedish Energy Performance Certificate (EPC) database is also utilized to establish a general benchmark of the heat recovery potential in Swedish food retail stores.

The results underline that food retail stores can efficiently recover all their needed heat from the refrigeration system, with seasonal heating coefficients of performance (COP) around 3-6. For an average sized food retail store, this practice can yield economic savings in operational costs of around 10 000-15 000 €/y, equivalent to 20-50% of the combined refrigeration and heating costs, compared to a district heating baseline. Under appropriate control strategies, surplus heat can also be exported outside the food retail store premises and sold to building owners, resulting in additional profits around 7-35%. On a national scale, the heat recovery potential is estimated to 670-1840 GWh annually, depending on the assumed levels of export, corresponding to 1.0-2.5% of Sweden’s space heating demand. The total heat recovery is achieved at seasonal heating COPs of 4-5.

However, empirical evidence in this thesis indicates that the theoretical heat recovery potential is not fulfilled in practice, suggesting there is a performance gap in terms of energy efficiency. This PhD thesis intends to address this gap, explore its underlying causes, and propose measures to overcome it. By mixed-method qualitative studies, based on data collection from site visits, meetings, informal interviews, and workshops, a number of significant barriers to heat recovery are identified. These include split economic incentives, a lack of access to capital, uncertainty or imperfect information, and missing accessible business models. The different case studies also reveal the wide range of conditions food retail stores have, with varying sizes, locations, technical systems, company chains and organizational structures, neighboring buildings, and lease agreement types. This thesis addresses the heterogeneity and proposes guidelines on heat recovery solutions and appropriate business models under varying conditions. These guidelines are based on what is identified as best practice in the food retail industry, following observations from the case studies.

Key identified means to overcome the barriers are standardized collaborative agreements between food retail stores and building owners, dedicated energy management practice, accessible business models, and alternative financing mechanisms, possibly by servitization. Four business models are proposed for appropriate lease structures and technical systems. The business models are analyzed both in simulations and in operational food retail stores. For example, under a typical net lease, operational costs of the property are of little interest for building owners, but a self-sufficiency business model can realize economic savings of 14 000 €/y or 49% of the combined heating and refrigeration costs for the food retail store. On the other hand, a Sell-and-Buyback business model can overcome the split incentives problem under a gross lease structure, estimated to achieve savings of 6400 €/y for the food retail store and 2300 €/y for the building owner, corresponding to 36% and 9% of energy costs, respectively.

In conclusion, this thesis sheds light on the underused potential of heat recovery in food retail stores with CO₂ systems. The information can be used case-by-case by food retailers and real estate companies to estimate achievable energy and cost savings, as well as on a wider scale for climate targets and policymakers. The proposed solutions can play a role in the energy transition through both contributing to the decarbonization of the heating and cooling sector and of the food retail industry.

Link to DiVA