Heat-driven snow production applying ejector and natural refrigerant

An effect of climate change is fewer cold days and less natural snow at lower elevations. This has spurred the interest in temperature independent snow (TIS) production, i.e., refrigeration technologies that can produce snow at ambient temperatures above zero. Commercially available TIS systems require a higher power consumption than conventional systems, i.e., snow lances and guns. Thus, to ensure that future snow-making sites are sustainable, it is necessary to develop solutions with a minimal environmental footprint. One possibility is to utilize surplus heat from industrial processes or from a district heating network to drive snow-making systems. Examples of heat driven refrigeration technologies fit for this purpose are absorption cooling and ejector cooling, both applying natural refrigerants. This paper evaluates a solution for heat driven ejector-based snow making systems: a vacuum ice slurry system using water (R718) as refrigerant. The required amount of driving heat and its required minimum temperature level largely depend on the ejector characteristics. Thus, to enable a proper evaluation, detailed numerical simulations of the ejector design and its efficiency were performed, at different temperature levels of driving heat and ambient temperatures. Results were used as input to estimate the overall performance, in terms of specific energy consumption (per m3 produced snow), compared to other TIS systems. The ejector-based system can be driven by low-grade heat (80 °C) and is shown to be highly efficient if cold cooling water (≤ 10°C) is available.Heat-driven snow production applying ejector and natural refrigerantacceptedVersio

Simultaneous implementation of rotary pressure exchanger and ejectors for CO2 refrigeration system

Natural refrigerant CO2 has become a viable choice for refrigeration units. The CO2 systems are working efficiently on land-based facilities, and their demand is increasing for offshore applications, e.g., cruise ships and fishing vessels, due to their environment-friendly nature and compactness. The investigated application of the CO2 system in this work is a single-stage system for air conditioning and a two-stage system for provision refrigeration at high heat rejection temperatures. The CO2 transcritical cycle allows operating in higher ambient temperatures and in a colder climate with significant heat recovery. However, the system efficiency decreases in higher ambient conditions due to the high-pressure ratio and expansion losses. Therefore, ejectors are implemented to boost the cycle efficiency at high heat rejection temperature conditions. The pressure exchanger (PX) device recently came up and claimed to be an option to recover expansion work in CO2 systems. PX is already in use for reverse osmosis (RO) desalination units to recover pressure work from the high pressure reject concentrate to low-pressure seawater. This work theoretically investigates the implementation of a CO2-PX for transcritical CO2 systems combined with ejectors and compressors. The energy efficiency of alternative system configurations is evaluated for various operating conditions.Simultaneous implementation of rotary pressure exchanger and ejectors for CO2 refrigeration systemacceptedVersio

Investigation of CO2 refrigeration system and thermal energy storage for passenger ships

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Innovative refrigeration concept for passenger ships - combining CO2 refrigerant, cold recovery and cold storage

More stringent international regulations on ship's emissions require a shift towards more climate friendly fuels, such as liquefied natural gas (LNG). On LNG-driven ships, the fuel is stored onboard at cryogenic temperature. The fuel must be vaporised before injected into the engine, implying a potential for cold recovery. Today, concepts are commercially available for utilising this surplus cold in conventional AC chiller system. This paper proposes an innovative concept where the LNG cold recovery system is integrated with a provision refrigeration system based on a CO2 booster unit and a cold thermal storage (CTES) due to the dynamic nature of loads and cold-recovery availability. The CTES is based on phase change materials (PCM) which, together with the choice of CO2 as refrigerant, ensures a compact system. The results show a potential for significant reduction in power consumption of the refrigeration systems and thereby contributing to reduced GHG emissions.Innovative refrigeration concept for passenger ships - combining CO2 refrigerant, cold recovery and cold storageacceptedVersio

Energy consumption of ammonia refrigeration system on board a fishing vessel

When assessing the carbon footprint of seafood from capture fisheries, the fuel use during fishing operation is the major contributor to overall greenhouse gas emissions. While the necessary shift towards low-carbon fuels and advancement in propulsion technology has commenced, also a more efficient use of energy is a key strategy for reduction of the emissions. Furthermore, leakage of high-GWP refrigerants contributes to emissions and a transition towards natural refrigerants (NH3, CO2) is essential. Introducing efficiency measures depends on knowledge of current performance. Due to the wide range of different fishing vessels with different on-board processing equipment and different modes of operation, the performance needs to be evaluated for each fleet segment before proper advise can be given. This paper presents energy measurement results from a research cruise conducted during autumn 2020 on a combined purse seiner/pelagic trawler. The vessel's refrigeration system was instrumented with sensors logging the electrical input to frequency converters (compressors and seawater pumps) and temperatures on the RSW side, while the vessels mode of operation and fuel consumption was logged on a regular basis during the cruise. The results provide insight on the vessel's energy flow, performance of the refrigeration system and fuel intensity of the fishing operation, which gives valuable input for design of efficiency measures.acceptedVersio

Review of environmental indices in the maritime sector – with focus on heating and cooling systems onboard cruise ships

The objective of the CruiZE project is to develop innovative, integrated and environment-friendly concepts for supplying heating and cooling needs for the hotel facilities on board cruise ships. As in other sectors, there are non-technological barriers which must be addressed to pave the way for implementation of new technology. For example, increased knowledge is needed on the environmental indices that are applied by different stakeholders to assess a ship's environmental performance. In this memo such indices are reviewed, with a focus on cruise ships, and how the heating and cooling systems are addressed. This will form a basis for further work in CruiZE, aiming at suggesting recommendations on how to modify such indices, to encourage the implementation of innovative heating and cooling technologies. Included in the review are compulsory regulatory indices issued by IMO, voluntarily indices offered by classification societies, and indices applied to offer port fee reductions. The review shows that there is a need to adapt these indices to enable a more equitable assessment of new heating and cooling technologiespublishedVersio

KLD HFC free Chiller India : environmental benefits of implementing a CO2 heat pump for combined heating and cooling at Bengaluru centralised school kitchen

Akshaya Patra Foundation is the world’s largest (not-for-profit) Mid-Day Meal Programme operating around 50 centralised kitchens supplying wholesome food to over 1.8 million children at more than 16,000 schools in 12 different states across India. In the project presented in this report, a heat pump using the natural refrigerant CO2 is proposed as an energy-efficient and climate-friendly concept for the centralised kitchen at Bengaluru. The CO2 heat pump does not only replace the HCFC units for space cooling, but also supplies hot water to the cooking process, reducing the steam boiler's fuel consumption. A cold and hot water storage is included to balance the mismatch in cooling and heating demand on a daily basis. The proposed concept offers substantial reductions in greenhouse gas (GHG) emissions from the cooling system (almost 60%). For the total system (cooking process and space cooling) the reduction in energy demand, energy cost and GHG emissions are all above 30%. This clearly shows the possibility for India to efficiently bypass the use of HFCs as temporary replacements for HCFCs, and by that avoiding significant GHG emissions and costly replacement processes. Suggestions for potential future improvements include a roof-top solar power system and a steam producing heat pump using natural refrigerants.publishedVersio

Alternative fuels and propulsion systems for fishing vessels

The main objective of CoolFish is to increase energy efficiency of the utility systems (cooling, freezing and heating) onboard fishing vessels. To achieve a full potential of efficiency and environmental benefits the ship must be considered as an engineering system, i.e. also considering the propulsion system. Stricter environmental regulations and an increased awareness of energy use and emissions force the shipping sector to adapt new fuels and/or propulsion systems to replace the conventional mechanical diesel engines. This report provides an overview on such alternatives with focus on new-built and ordered Norwegian fishing vessels. The review shows a development towards diesel-electric or hybrid propulsion systems, often with hybrid power supply (e.g. batteries). Hybrid propulsion and hybrid power supply enables several operating modes, to match speed and auxiliary requirements, enabling flexible and fuel-efficient operation. However, it also implies challenges in relation to waste heat availability and sizing of heating and cooling equipment. Alternative fuels with high technical feasibility for the fishing sector include LNG/LBG and biodiesel for all fishing vessel types, and hydrogen fuel cells for coastal fishing ships. Battery implementations for partly electrified propulsion are considered highly feasible for the whole fishing sector.publishedVersio

Implementation of natural refrigerants on cruise ships. A review of rules and regulations from two Classification Societies

This report delves into the challenge of implementing heat pumps, refrigeration systems and chillers (vapour compression systems) that use natural refrigerants, in the maritime sector. The first part gives a context, introducing the international organisations aim to reduce greenhouse gas emissions from the shipping industry, and defining the topic of refrigerant selection. The documents on safety requirements for vapour compression systems onboard, issued by the classification societies Lloyds Registers and DNV, are then summarised. The focus is on the implications for systems using natural refrigerants. It is found that a "case-to-case" evaluation of almost all these systems must be applied. In the last section the communication with the classification societies is summarised. The goal is to contribute to clearer and more standardised requirements on the use of natural refrigerants, to facilitate their safe implementation, environmental-friendly and long-term compliant maritime refrigerants.publishedVersio

Carbon footprint of fisheries - a review of standards, methods and tools

This report provides an overview of standards, methods, certification schemes, tools, and previous studies related to the carbon footprint (CF) of seafood, both in general but especially related to fishing vessels and refrigeration systems. The aim is to give various perspectives on CF estimations for fisheries, as a basis for further work in CoolFish. A few standards are specifically developed for seafood products; the British PAS2050:2 and the Norwegian NS-9418. Sustainability certifications typically evaluate harvesting pressure, fishing practices and fisheries management. Even if energy use and emissions are often built into the assessment criteria, the CF is rarely specifically addressed. Online tools are available for CF estimations of seafood products, or parts of the product chain. Data for the fishery stage are based on conventional diesel propulsion, and the refrigeration system is only addressed by default values on refrigerant leakage. Previous studies on CF assessment of captured sea-food shows that the fishing vessel's fuel consumption is generally the dominant contributor. Emissions of synthetic refrigerants can also play an important role, as can air transportation. More disaggregated data on fuel use are required to evaluate on-board measures for CF reduction. Further work in CoolFish could contribute with estimations of fuel use for propulsion and refrigeration, for different fishing vessels and operational modes.publishedVersio