Supermarkets are among the most energy intensive commercial buildings and they consume high amounts of refrigerant, thus causing significant environmental concern. Supermarkets therefore make up important targets for energy efficiency measures, one of which being heat recovery from refrigeration systems, particularly suitable for the environmentally friendly refrigerant CO<inf>2</inf>. In this work, four Swedish supermarket case studies are analyzed from a techno-economic perspective. All studied supermarkets have CO<inf>2</inf> booster systems with heat recovery and their technical efficiency are evaluated, as well as already accomplished economic savings. This study estimates the studied supermarkets are currently saving 600–6,100 € annually, which corresponds to 4–12 % of the energy costs for refrigeration and heating. Higher annual economic savings of 2,400–37,100 € (14–42 %) could be achieved if the refrigeration systems were instead controlled to cover all the heating demands in the supermarkets, or savings of 5,400–35,800 € (24–58 %) if also selling a surplus to nearby consumers. The heat recovery capacity and efficiency are parametrically explored, revealing the importance of designing systems for transcritical discharge pressures and low heating system return temperatures. The study also investigates the impact of price ratios of electricity and heat, demonstrating that recovering heat for internal use is a robust strategy under wide ranges of energy prices, while exporting surplus heat is more sensitive. Ultimately, this work shows that heat recovery solutions can significantly decrease energy costs in supermarket buildings under varying market conditions for electricity and heat, but the potential is yet to be fully realized in practice.

Supermarket refrigeration systems offer the possibility to recover significant amounts of energy. These amounts may at times be higher than what the supermarket needs. In these cases, export of heat or air conditioning to neighboring buildings is a solution for increased overall energy efficiency. However, although previous studies have demonstrated the technical viability of such systems, they are rarely implemented in practice. In this work, possible barriers to and drivers of implementation of thermal energy export from supermarkets are investigated. The empirical work consists of a mixed-method data collection and in-depth analysis of six case studies of supermarkets that are in a research collaboration project between the KTH Royal Institute of Technology in Stockholm and CIT Energy Management in Gothenburg, Sweden. The main findings indicate that several barriers, especially the split economic incentives of supermarkets and property owners and a lack of information, have significant detrimental effects on the uptake of thermal energy export solutions. Cooperative agreements between supermarkets and property owners are found to have the greatest possibility to mitigate the impact of the barriers, but standardized templates are needed to reduce their associated legal, technical, and administrative uncertainties.

Overfeeding the medium temperature level evaporators using liquid ejectors is one of the features of the modern CO2 refrigeration systems for supermarket applications, which provides higher evaporation temperature. The liquid leaving the evaporator is accumulated in a liquid receiver before the compressor and is pumped back to the main receiver before the evaporators by the liquid ejector. This paper uses field measurements of two supermarkets in Sweden. One of the supermarkets is analysed in two days where it operates under overfeed conditions at one day and under dry expansion conditions at the other, providing better understanding of the benefit of overfeeding the cabinets. The first system shows that the evaporation temperature is increased by 2 K (from -6 degrees C to -4 degrees C) while the air set point temperature inside the cabinet is kept satisfied. The second system shows that the evaporation temperature can be up to -2.5 degrees C with a small impact in the cabinets' air set point temperature satisfaction.

This study explores the capability of a supermarket to fulfill the thermal demands of neighboring buildings. The research combines field measurements analysis, obtained from a Swedish supermarket which covers the neighbors' thermal demands, with theoretical calculations, using thermodynamic models of the refrigeration system and the ground source thermal storage. In contrast to previous studies, this work is unique in its use of demonstrating a real-life built case study rather than only theoretical approach. Results demonstrate that inte-grating ground source storage in a supermarket can meet the thermal demands of neighboring buildings without requiring additional equipment. The refrigeration system accounts for 80% of the total heat demand, while the ground serves as a heat source for the rest. This approach results in 67% annual operating cost savings for the neighboring buildings. In addition, ground source subcooling provides 9% annual energy savings to supermar-ket's refrigeration system. By exporting heat to neighboring buildings, the proposed solution emits 90% less CO2 in Uppsala and 67% less in Stockholm compared to solutions in which the refrigeration system only meets the refrigeration demands. Summing up, the concept of utilizing supermarkets to meet thermal demands offers a more energy-efficient operation for both supermarkets and property owners while significantly reducing annual energy consumption and emissions.

In the Peruvian mountains, hundreds of thousands of rural households living in poverty live in cold indoor environments, close to 0 °C. Indoor cold causes thousands of respiratory diseases and excess of winter deaths. In this study, we numerically calculated the impact of simple low-cost refurbishments on discomfort time during a year. Using EnergyPlus and Python, we modelled a typical one-room hut used as bedroom built with a metal-sheet roof, adobe walls, dirt floors, and high infiltration rates. Then, 9 individual solutions were studied, and their combination resulted in 215 different hut designs. The model was calibrated with field measurements to estimate the infiltration. All the numerical calculations included an uncertainty analysis based on Monte Carlo method, and a sensitivity analysis to assess the impact of reducing infiltration on discomfort time. The base case had a discomfort time of 44% of time. The calibration of infiltration resulted in a mean hourly air exchange rate equal to 29.1 h−1 (SD = 17.0 h−1). Five different designs formed the Pareto front that optimized discomfort time and costs. The solution with the lowest discomfort time during a year, 37% of the time, was adding insulation to the roof (U = 0.83 W/m2•K) and the door (U = 1.00 W/m2•K); and its cost was 286USD. In this solution, when infiltrations were reduced to 4.1 h−1 (SD = 4.1 h−1) discomfort time decreased until 16%. These results benefit those households that nowadays invest their limited resources to improve their living conditions but without technical guidance.

This paper presents the performance analysis of a well-instrumented supermarket in Sweden where heating, air conditioning and ground storage are integrated into a booster trans-critical CO2 refrigeration system. The supermarket has applied several features of a state-of-the-art system, including overfeed evaporators, 2-stage heat recovery, and air conditioning. Two warm and two cold days operation are used for the control and the performance investigation. The heat recovery follows the theoretical control strategy, where the setpoint temperature for the discharge pressure is the forward water temperature to the heating system. The combination of low water temperature return from the space heating system and 2-stage heat recovery provides efficient operation; COP heating is estimated around 6. The warm days study shows that importance of fast fault detection which resulted in 16% energy savings in this case study. The fault drives to limitation of the air conditioning capacity and as result indoor temperature increment. The air conditioning COP is estimated around 2.5 for both warm days, with potential of 20% increase in the COP with optimized operation without thermal leakage to the ground.

This paper investigates the theoretical energy outlook of a supermarkets in Stockholm, as well as the energy efficiency of its refrigeration unit. The refrigeration unit is a CO2 trans-critical booster system with air conditioning and geothermal storage integration into the medium temperature level. This stage is operated under overfeed conditions (zero internal superheating) thanks to liquid ejectors. On the other hand, the freezers operate under direct expansion with an optimum superheat. The supermarket is heated up by reclaimed heat from the refrigeration unit. Two heat exchangers are integrated after the high-stage compressors where water is heated for tap water and space heating.

The simulation is done for a supermarket in the design stage as part of a study that will continue by collecting data from the supermarket when is in operation to evaluate its performance and compare to the results from the design phase. The cooling demand of the medium temperature level is estimated between 100-140 kW depended on the ambient conditions and around 40 kW for the freezers. The COP in the medium temperature level is expected to be up to 7.8 and 2.5 for the low temperature level. The space heating COP is expected to be up to 7.3.

With an increasing concern regarding climate change and the increasingly higher rate of urbanization worldwide, cities are expected to play a more important role in the future global energy system. Therefore, sustainable urban development projects, so-called EcoCities projects, are carried out globally. EcoCities are normally focusing on minimizing energy use and greenhouse gas emissions as well as to serve as platforms for innovation fostering. One good example is Royal Seaport in Stockholm, Sweden in which an Innovation Arena has been established by the utilization of the Triple Helix innovation model where academia, industry and the city are cooperating. Due to the fact that EcoCity projects often are focusing on Innovation creation, this study defines a multi-level perspective framework for systems innovation in such projects. Based on previous studies on systems innovation from a multi-level perspective, the framework explains the occurrence of EcoCity projects as a reaction to the change in climate and urbanization as well as how EcoCities are acting as innovation platforms by simplifying the integration of emerging technologies in the city system. This paper also presents a hypothesis that EcoCity projects enable a shortened time for vision and ideas to transform into inventions and furthermore into innovations by reaching acceptance. (C) 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

Introducing new technologies in buildings in Sweden have historically been connected with great portions of scepticism, hence influencing the speed of acceptance of new technologies. The speed is slow even though technologies are tested, evaluated, proven to make an impact, and economic efficient. In order to understand acceptance of energy efficient technologies in multifamily buildings and to identify the origin of barriers to energy efficiency this paper investigates barriers as consequences of the current system structure in the Swedish building sector. The study views the Swedish building sector as a sociotechnical system built from technical artefacts, institutions, and actors, thus often deeply embedded in our societies. The Swedish building sector is well structured, resulting in that innovation and development occurring outside of the existing sociotechnical regime might not be recognized as feasible investments. In order to identify the structures enabling barriers to energy efficiency adoption this paper aims at developing a framework for categorizing barriers depending on their structural origin. The categorization framework is inspired by theories of sustainable innovation journeys and of soft systems and distinguishes between three decision-levels for barriers to energy efficiency: Project level, Sector level and Contextual level. By implementing the proposed categorization framework it becomes obvious that problem areas in the building sector are not connected to any specific structural level. However, results in this study reveal that most barriers originate in the Contextual level, which implies that energy and sustainability are not yet key aspects when forming and transforming contextual preconditions on how to design and build multifamily buildings in Sweden. (C) 2015 The Authors. Published by Elsevier Ltd.