| 1. |
- Fischer, D., et al.
(författare)
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Smart meter enabled control for variable speed heat pumps to increase PV self-consumption
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 4049-4056
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Konferensbidrag (refereegranskat)abstract
- In the last five years the costs of photovoltaic systems have decreased considerably making it economically attractive to generate electricity locally. In many countries, self-consumption is the most attractive option to make use of the generated electricity. Variable speed heat pumps - if controlled properly - can take a share of the PV electricity to decrease costs and CO2 emissions for heat generation and increase PV self-consumption. This paper discusses a control strategy that uses real-time smart meter readings and adjusts the compressor speed to adapt heat pump electricity consumption depending on the available PV power. The approach is tested in a detailed building simulation. Self-consumption can be increased by 6% compared to a heat driven control. For the chosen PV size of 10kWp in a German multi-family house, an increase of storage size shows only little possibility for a further increase in self-consumption.
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| 2. |
- Fischer, David, et al.
(författare)
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Test cases for hardware in the loop testing of air to water heat pump systems in a smart grid context
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 3666-3673
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Konferensbidrag (refereegranskat)abstract
- Heat Pumps for heating and cooling purposes could play an important role in the future energy system. Combined with a thermal storage they offer the possibility for demand side management applications in a smart grid. Optimized utilization of local solar resources can be achieved by increasingly sophisticated control strategies. Smart gird integration and the use of solar resources will bring new challenges to heat pump system design and operation. However standardized testing procedures to compare HP-systems and controllers in a dynamic and possibly smart grid environment are currently lacking. In this work a method to extract representative test days from energy data, to be used in a Hardware In The Loop test is presented. The resulting sequence of 12 test days is compared to the one year data set and tested in building simulation. Yearly heat generation and SPF can be reproduced with an accuracy of above 94% using the test days.
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| 3. |
- Ignatowicz, Monika, et al.
(författare)
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Ethyl and isopropyl alcohol blends as alternative secondary fluids
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 2224-2231
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Konferensbidrag (refereegranskat)abstract
- Methyl and ethyl alcohol based secondary fluids are commonly used in different indirect refrigeration systems due to relatively good thermophysical properties. Methyl alcohol is considered toxic and not permitted for use as secondary fluid in most of Europe. Ethyl alcohol based secondary fluids are commonly used in Sweden due to their low toxicity and good properties. Commercially available ethyl alcohol based fluids contain up to 10 wt-% denaturing agents in form of propyl alcohol (2-propanol, isopropanol) and nbutyl alcohol (n-butanol). Results show that presence of propyl alcohol in the ethyl alcohol based secondary fluid improves its thermophysical properties such as specific heat capacity, thermal conductivity and dynamic viscosity when added in small concentration. The aim of this paper is to investigate the thermophysical properties of various ethyl and isopropyl alcohol blends in order to find the most optimal blend as well as to evaluate if this blend could become a competitive alternative secondary fluid.
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| 4. |
- Karampour, Mazyar, et al.
(författare)
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Theoretical analysis of CO2 trans-critical system with parallel compression for heat recovery and air conditioning in supermarkets
- 2015
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Ingår i: Refrigeration Science and Technology. - Yokohama, Japan : International Institute of Refrigeration. - 9782362150128 ; , s. 2321-2328
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Konferensbidrag (refereegranskat)abstract
- This paper theoretically analyses a CO2 trans-critical booster system in which parallel compression, heat recovery and air conditioning are integrated. The performance of the system is studied in various running modes using flash gas by-pass (FGBP) or parallel compression (PC). These running modes include summer cases with/without air conditioning and winter case with heat recovery. The results show that parallel compression is more efficient than flash gas by-pass in summer cases; the increase in COPtot is up to 14% comparing the best cases for PC and FGBP. The increase in COPtot in winter heat recovery mode is marginal, less than 4-6% and hardly-feasible in practice. Comparing the AC function of the CO2 system with a conventional HFC air conditioning system, it has been found that CO2 system is more efficient in moderate ambient temperatures lower than 20-25°C. The CO2 system's AC performance is less efficient than HFC solution in ambient temperatures higher than 25°C. To conclude, an integrated CO2 trans-critical booster system can to provide the entire supermarket's refrigeration and air conditioning demands for cold-mild climates with comparable or higher energy efficiency than the HFC solutions.
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| 5. |
- Lundqvist, Per
(författare)
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The role of heat pumps in the smart energy systems
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 90-94
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Konferensbidrag (refereegranskat)abstract
- Heat pumps are needed in the future energy system to save primary energy, increase the share of renewable energy and thus to reduce climate impact. This is manifested in most recent future scenarios for low carbon energy systems that acknowledge the importance of efficient and reliable heat pump system. The role of heat pumps will change and broaden as the energy system becomes smarter. Information and smart controls in heat pumps coupled to storage possibilities will stabilize the electric energy system when the amount of flowing energy sources such as wind and solar energy increases. A stronger focus on resource efficiency and reduction of primary energy will put pressure on required seasonal performance factors for heat pump system. Increased system efficiency and high energy coverage are thus important challenges for heat pump system design. Hybrid systems where heat pumps are coupled to solar thermal energy and solar PV systems are likely to emerge on the market.
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| 6. |
- Madani, Hatef
(författare)
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Smart fault detection and diagnosis for heat pump systems
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 3703-3710
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a holistic approach to develop a Smart Fault Detection and Diagnosis (SFDD) system which can be integrated and widely used in both old and new heat pump systems worldwide. A SFDD acts as the heart of smart heat pump system. It is able to minimize the installation and control errors, couple or decouple the renewable energy sources, make load-shifting possible, detect the performance degradation during operation, avoid unnecessary visual inspections and components replacement, and reduce the maintenance cost and down-time of the system. In order to determine the most important faults in the heat pump system, a comprehensive study is done on the faults reported to both OEMs and a main insurance company in Sweden and the results are briefly presented. The paper also discusses how a knowledge-based Smart Fault Detection and Diagnosis unit should be designed to support the heat pump systems at commissioning, operation, and maintenance phases.
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| 7. |
- Makhnatch, Pavel, et al.
(författare)
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Applicability of global temperature change potential (GTP) metric to replace GWP in TEWI environmental analysis of heat pump systems
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 324-329
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Konferensbidrag (refereegranskat)abstract
- Recent legislative measures promote use of environmentally friendly refrigerants to mitigate global warming. Different environmental metrics are used to facilitate decision-making process of selection of refrigerant with low environmental impact. Total equivalent warming impact (TEWI) methodology is able to reflect the effect of heat pump or refrigeration system to global warming by accounting for both direct and indirect emissions associated with the refrigeration system. This paper extends TEWI methodology by using Global Temperature change Potential (GTP) metric instead of Global Warming Potential (GWP) one, which conventionally used to put different emissions on single CO2 scale. The analysis is done for the simple vapour compression heat pump system, where a number of refrigerants are compared. The study concludes with the analysis of applicability of modified TEWI analysis for further refrigerating system environmental assessment studies.
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| 8. |
- Makhnatch, Pavel, et al.
(författare)
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Evaluation of Cycle performance of R448A and R449A as R404A replacements in supermarket refrigeration systems
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 - 9781479954421 ; , s. 437-444
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Konferensbidrag (refereegranskat)abstract
- According to the requirements of the European regulation on fluorinated greenhouse gases, refrigeration equipment that contain high Global Warming Potential (GWP) refrigerants that have GWP equal or greater than 2500, with some exceptions, will be prohibited from placing on the European market from 1st January 2020. Moreover, the use of such fluorinated greenhouse gases to service or maintain refrigeration equipment with a charge size of 40 tonnes of CO2 equivalent or more will be prohibited as well. The greatest impact of the Regulation in the nearest time will be therefore on users of R404A refrigerant, which is the most popular refrigerant for supermarket refrigeration systems. Equipment users and manufacturers are therefore looking for the alternative refrigerants to replace R404A in new and existing equipment. R448A and R449A are potential R404A replacements. Both are non-toxic and non-flammable refrigerant blends that closely match the properties of R404A and have GWPs significantly lower than R404A. Cycle performance of a supermarket refrigeration system, operated with R448A, R449A and R404A is modelled in this study.
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| 9. |
- Melinder, Åke, et al.
(författare)
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Ice slurry properties of seawater
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 2098-2105
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Konferensbidrag (refereegranskat)abstract
- Ice generating machines are more and more used on fishing vessels to produce ice slurry from seawater. Because slurry with up to 60% ice can be handled and poured over the catch, there is excellent potential for long preservation of the catch on board and during transport, improving seafood quality for the end user. A literature search has been made to establish physical property data of seawater as a function of salinity and temperature. Ice slurry properties of seawater have been generated and are presented by means of an enthalpy phase diagram and related diagrams giving ice concentration, enthalpy change, density and viscosity of fine crystalline ice slurry. These studies also confirm that an initial salt content of 2-3% will give optimal performance. Seawater is known to be corrosive and a brief discussion of corrosion factors and problems, use of corrosion inhibitors and choice of materials is included in the paper.
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| 10. |
- Melinder, Åke, et al.
(författare)
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IIR handbook on indirect refrigeration and heat pump systems
- 2015
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Ingår i: Refrigeration Science and Technology. - : International Institute of Refrigeration. - 9782362150128 ; , s. 2240-2247
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Konferensbidrag (refereegranskat)abstract
- Indirect systems with secondary (working) fluid circuits are often used where there are many places to be cooled or where long pipes are required. Examples of systems with many places to be cooled are slaughter houses, dairies and breweries. Long pipes are common in air conditioning plants, artificial ice rinks and ground source heat pumps with long collector tubes in the ground. Indirect systems have often replaced systems with direct expansion within supermarket refrigeration, where the secondary fluid transports heat from cooling rooms or cabinets to achieve the right temperature of the products. Indirect systems are nowadays also used in freezer applications but more often with carbon-dioxide as phase changing secondary working media. Indirect systems have come in focus as requirements for tighter constructions are sharpened in order to minimize leakage of refrigerants from plants as well as the adjusted legislation to secure the phasing out of certain refrigerants. A Handbook on indirect systems was published in Swedish in 2010 in cooperation with over twenty companies and experts and an English translation has now been prepared to be published by the IIR. The chapters deal with the following topics: 1. Direct and indirect systems, 2. Indirect system solutions, 3. Components, 4. Secondary fluids, 5. Corrosion, 6. Environmental aspects, 7. Projecting and dimensioning, 8. Design and control of system, 9. System construction and installation and 10. Optimization of indirect systems. An expectation of all involved in producing the Handbook is that it will help to better understand and work with indirect systems. This paper is intended to give hints on what is covered in the Handbook!
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