| 1. |
- Abdi, Amir, et al.
(författare)
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Heat recovery investigation of a supermarket refrigeration system using carbon dioxide as refrigerant
- 2014
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Ingår i: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants. - : International Institute of Refrigeration. - 9782362150043 ; , s. 277-285
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Konferensbidrag (refereegranskat)abstract
- This study investigates the heat reclaim of trans-critical CO2-booster refrigeration unit in a supermarket in Sweden. The aim is to compare the control strategy for heat recovery in real supermarket installation to the optimum control strategy.The optimum control strategy based on theoretical analysis is explained. By analyzing field measurement of a supermarket, heat recovery in the refrigeration system is studied and compared to the optimum case. To investigate the potential of higher heat recovery rate, a computer model is developed based on the optimum control strategy. The model is also used to calculate the boundary conditions at which the system should run for highest COP.The results show that heat can be recovered at heating COP of 3-4.5. The theoretical analysis shows that the amount of heat that can be recovered from the refrigeration system is about 1.3 times (130 %) the cooling demand in the system. However the analysis of the field measurements shows that only between 30-60 % of the available heat to be recovered is utilized, the rest is released to outdoors. The analysis in this study shows that there is a potential to recover much more heat from the refrigeration system at relatively high heating COP compared to heat pump.
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| 2. |
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| 3. |
- Arnaudo, Monica, et al.
(författare)
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Heat recovery and power-to-heat in district heating networks – Atechno-economic and environmental scenario analysis
- 2021
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 185, s. 116388-
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Tidskriftsartikel (refereegranskat)abstract
- Heat recovery from local resources is shown to be a promising solution to reduce the carbon footprint of district heating. Supermarkets equipped with a CO2 refrigeration system and a geothermal storage offer a larger heating capacity, compared to traditional solutions. While district heat could benefit from this higher heat recovery availability, supermarkets could generate an income from a capacity that would be otherwise unused. For the first time, this study applies a detailed modelling approach considering both sides of such a synergy. The objective is to assess the techno-economic and environmental impact of a coordinated control strategy. Since the heat recovery from the supermarket consumes additional electricity, power-to-heat is implemented as a solution to reduce the overall CO2 emissions. This is demonstrated by scenarios simulated for a district in Stockholm. Hourly electricity CO2 intensity and prices are implemented as signals to prioritize either the district heating central supply or heat recovery. By boosting the use of electricity when cleaner, a CO2 intensity-driven control show the potential of reducing the carbon footprint of the district (−9.4%). A control based on prices, instead, is more convenient economically both for the district (−1.4% heat cost) and for the supermarket (−32% operational cost).
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| 4. |
- Duarte, Willian M., et al.
(författare)
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Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water
- 2019
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 184:May, s. 527-538
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Tidskriftsartikel (refereegranskat)abstract
- An important step during a project of a heat pump system is choosing a more suitable refrigerant. This paper presents a comparative study among refrigerants for a small direct expansion solar assisted heat pump (DX-SAHP). The mathematical model used in this study is presented in detail and validated from an experimental setup. The R134a is the reference and the refrigerants with low GWP are R290, R600a, R744 and R1234yf. The results show that R290 has better COP than others refrigerants for solar radiation between 300 W/m2 and 700 W/m2, as well as for environment temperature between 10 C and 35 C. On the other hand, for solar radiation less than 50 W/m2, the R134a has better COP than R290. TEWI (Total Equivalent Warming Impact) analysis indicates that the indirect emission is the most important effect, and then, the TEWI results almost followed the COP outcome. A parametric analysis was conducted to evaluate the influence of the CO2 emission factor for producing electricity. In countries with higher emission factor, the refrigerant with the best COP has the best TEWI. The influence of wind speed and ambient temperature in COP of a DX-SAHP using R290 were more relevant in low solar radiation
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| 5. |
- Giunta, Fabio, et al.
(författare)
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Techno-economic analysis of heat recovery from supermarket's CO2 refrigeration systems to district heating networks
- 2021
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the opportunity of utilizing the spare heating capacity of CO2 refrigeration systems in supermarkets to produce heat to be sold to district heating network operators. A comprehensive description and assessment of two control strategies that could be implemented to enable the heat export function are presented. To maximise the heating capacity during the coldest moments of the year, the integration of geothermal storage with the CO2 system was investigated as an additional scenario. The BIN method was used to perform annual energy calculations. Furthermore, a sensitivity analysis was carried out on the most critical parameters, namely the heating demand, price ratio and temperature levels of the district heating network. For the assumed prices and energy demands, the supermarket could make profits corresponding to up to 16% (10,000 (sic)/year) of the annual energy cost by selling part of the heat recovered to the district heating network operator. Furthermore, the heat exported could save up to 18% of the annual CO2 emissions of the supermarket compared to the baseline. Finally, the sensitivity analysis showed that the economics of this solution is the more profitable, the lower return temperature of the heating network where the installation is connected.
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| 6. |
- Karampour, Mazyar, et al.
(författare)
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Comparison of State-of-the-art CO2 and Alternative Refrigeration Systems for Supermarkets
- 2018
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Ingår i: 13th IIR Gustav Lorentzen Conference on Natural Refrigerants. - Valencia, Spain. - 9782362150265 ; , s. 1298-1306
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the state-of-the art features of CO2 trans-critical booster systems. The performance of various modified features have been compared to the standard CO2 booster system. Subsequently, the performance of the defined state-of-the-art CO2 system is compared to natural refrigerant-based cascade, HFC/HFO-based DX and indirect refrigeration solutions, and propane water-cooled plug-ins operating in cold and warm climates. The results indicate that flooded evaporation and parallel compression are the most promising features of the state-of-the-art CO2 system. This compact and environmentally friendly system is the most energy efficient solution in cold climates, and is also an efficient solution in warm climates, with comparable efficiency to cascade and HFC/HFO DX systems, but with no existing or potential limitations.
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| 7. |
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| 8. |
- Karampour, Mazyar, et al.
(författare)
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Energy Efficiency Evaluation of Integrated CO2 Trans-critical System in Supermarkets : A Field Measurements and Modelling Analysis
- 2017
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Ingår i: International journal of refrigeration. - : Elsevier. - 0140-7007 .- 1879-2081. ; 82, s. 470-486
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates energy efficiency of an integrated CO2 trans-critical booster system installed in a supermarket in Sweden. The supermarket has applied several features to improve energy efficiency including space and tap water heating, air conditioning (AC), and parallel compression. Using field measurements data, the system performance is evaluated in a warm and a cold month. Furthermore, this integrated energy system concept is modelled and compared with stand-alone HFC-based energy systems. The results show that the system provides the entire AC demands and recovers a great share of the available heat, both with high COP values. The comparative analysis shows that integrated CO2 system uses about 11% less electricity than stand-alone HFC solutions for refrigeration (i.e. indirect HFC), heating and AC in North of Europe.Energy efficiency analysis of the integrated CO2 system proves that this system is an environmentally friendly all-in-one energy efficient solution suitable for cold climate supermarkets.
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| 9. |
- Karampour, Mazyar, et al.
(författare)
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Field Measurements and Performance Evaluation of CO2 Supermarket Refrigeration Systems
- 2013
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Ingår i: 2nd IIR International Conference on Sustainability and the Cold Chain. Proceedings. - 9782913149977
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Konferensbidrag (refereegranskat)abstract
- This paper studies field measurements and performance analysis of eight supermarkets in Sweden amongwhich five supermarkets use CO2 and three use HFC as the refrigerant. The differences in system design arediscussed and detailed performance evaluation of one of the systems is presented. The performances of allthe supermarkets are compared and the reasons for higher or lower energy efficiency are discussed. Somekey components of CO2 systems are evaluated, as well.According to the results, the older CO2 systems have lower COP than the reference systems. High vapourfraction in low temperature cabinets inlet, relatively high amount of internal and external superheating and10-15% lower overall efficiency of low temperature compressors compared to the other systems are some ofthe main reasons for this lower COP. But, the newer CO2 systems proved to have higher efficiency, or atleast, as energy-efficient as the conventional systems. This originates from the modification in the systemdesign and more efficient components. System design modification includes two-stage expansion by receiverand flash gas by-pass. The newer CO2 components have higher efficiency; medium temperature levelcompressors have 5-10% higher overall efficiency compared to HFC and older CO2 compressors and thecabinets run with lower superheating so the system can be controlled to run at higher evaporationtemperatures.This study shows that CO2 systems have comparable COP to advanced conventional systems applied in Sweden.
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| 10. |
- Karampour, Mazyar, et al.
(författare)
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Geothermal Storage Integration into a Supermarket’s CO2 Refrigeration System
- 2019
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Ingår i: International journal of refrigeration. - : Elsevier. - 0140-7007 .- 1879-2081. ; 106, s. 492-505
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the integration of geothermal storage into state-of-the-art CO2 trans-critical boostersystems. The objective is to evaluate the impact of this integration on energy efficiency. Three scenarios of integration are studied including stand-alone and integrated supermarket building systems. The results show that for a stand-alone average size supermarket, heat recovery from the CO2 system should be prioritized over a separate ground source heat pump. Extracting heat from the ground by an extra evaporator in the CO2 system has also little impact on this supermarket annual energy use. However, in the case of supermarket integration with a neighbouring building where the supermarket provides heat to the neighbour, geothermal storage integration can reduce the total annual running cost of the two non-integrated buildings by 20-30% with a payback time of less than 3.5 years. The results also show there is no need for a separate ground source heat pump.
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