The paper discusses the possibility of applying the trigeneration energy concept (cogeneration + absorption cooling) on diesel-powered refrigerated ships, based on systematic analyses of variable energy loads during the estimated life of the ship on a predefined navigation route. From a methodological point of view, mathematical modeling of predictable energy interactions of a ship with a realistic environment yields corresponding models of simultaneously occurring energy loads (propulsion, electrical and thermal), as well as the preferred trigenerational thermal effect (cooling and heating). Special emphasis is placed on the assessment of the upcoming total heat loads (refrigeration and heating) in live cargo air conditioning systems (unfrozen fruits and vegetables) as in ship accommodations. The obtained results indicate beneficiary energy, economic and environmental effects of the application of diesel engine trigeneration systems on ships intended for cargo transport whose storage temperatures range from −25 to 15 °C. Further analysis of trigeneration system application to the passenger ship air conditioning system indicates even greater achievable savings.

The article defines and discusses techno-economic models of CCHP system based on a power system with an internal combustion engine or a gas turbine with electric power of 0,2-1 MW including an absorption or vapour-compression refrigeration unit. The thermodynamic, ecological and economical features of the CCHP system under different load situations are analysed in relation to the basic model of energy generation with boiler and vapour-compression refrigeration unit. Based on the data of the equipment manufacturer, functional dependency curves of individual components are created in dependency to the load, which enables the construction of a system model composed of a power system (internal combustion engine or a gas turbine), single-stage or two-stage absorption refrigeration unit and boiler. A program solution has been developed applying the object-oriented programming language Modelica that enables the insight into the behaviour and techno-economic validity of usage of the analysed systems in transformable operating conditions. The article examines various energetic models, defining for the influential parameters (electric energy and fuel prices, investment costs and the level of heat recovery) the value of total energy efficiency, the return period on investment costs and the environmental impact concerns.

Original scientific paper The system of separate production of heat energy from a boiler and cooling energy from a compression refrigeration unit powered with electrical energy from an external network can be replaced with a CCHP system based on the operation of a gas turbine and absorption refrigeration unit. For this purpose, models of the system were derived through the use of the object-oriented programming language Modelica, on the basis of which steady-state simulations were carried out, as well as technical-economic and the sensitivity analysis of the system, in relation to the changes of influential parameters such as coefficient of performance, the boiler efficiency, the ratio of the electric load, costs of electrical energy, fuel prices and investment costs. Developed system model is intended to be used in further research for dynamic simulations with implemented dynamic boundary conditions. Keywords: absorption refrigeration unit; CCHP; compression refrigeration unit; micro-turbine; Modelica; sensitivity analysis; SimulationXTehno-ekonomska opravdanost zamjene sustava odvojene proizvodnje toplinske/rashladne i električne energije CCHP sustavom s mikroturbinom i apsorpcijskim rashladnim uređajem Izvorni znanstveni članak Sustav odvojene proizvodnje toplinske energije iz kotla, energije za hlađenje iz kompresijskoga rashladnog uređaja i električne energije iz vanjske mreže može se zamijeniti CCHP sustavom koji se temelji na radu plinske turbine i apsorpcijskoga rashladnog uređaja. Za tu su namjenu napravljeni su modeli sustava primjenom objektno orijentiranog programskoga jezika Modelica, na temelju kojih su vršene simulacije za stacionarna stanja i izvedena tehnoekonomska analiza te analiza osjetljivosti sustava u ovisnosti o promjeni parametara kao što je faktor hlađenja, stupanj iskoristivosti kotla, omjer električnog opterećenja, cijena električne energije, cijena goriva i trošak investicije. Razvijeni model sustava koristiti će se u istraživanjima koja slijede za dinamičke simulacije s uvedenim dinamičkim rubnim uvjetima.

This paper presents three approaches for isentropic, energy, and exergy evaluations of a low-duty liquid natural gas (LNG) vapor turbo compressor during exploitation on a conventional LNG carrier. The evaluation was conducted on the measured performance parameters under 22 various turbo compressor operating regimes. The turbo compressor performance was evaluated in the temperature span from −69 to −105 °C and during changes in the rpm of the main propulsion turbine and, consequently, the main boiler load. The results show that the highest measured turbo compressor isentropic efficiency is in agreement with the manufacturer specifications, equaling 75.23% at a main propulsion turbine rpm of 53.5. At the highest measured loads and rpm, the turbo compressor energy and exergy efficiencies reach the highest values of 57.81% and 28.51%, respectively. In each observed operating regime, the influence of the ambient temperature change on the turbo compressor exergy efficiency was investigated. At the lowest and the highest measured loads, turbo compressor energy and exergy flow streams are presented in a Sankey diagram. Techniques for cargo temperature maintenance during the ship voyage are presented, as the results show that low suction gas temperatures influence turbo compressor efficiency.

The paper deals with the topic of refrigerants, their historical evolution, applied legislation and trends in maritime affairs. Regarding the Environmental care paper considers the impact of refrigerants of refrigeration systems, both on stationary plants on land and on plants on board. New regulations of the European Union, and IMO maritime organization, require the reduction and complete abolition of harmful synthetic refrigerants and the introduction of new refrigerants that will have a significant economic and environmental impact. The trend is the introduction of natural refrigerants as a replacement for existing environmentally unacceptable ones. On-board refrigeration systems introduce natural refrigerants such as ammonia and carbon dioxide into applications that require lower refrigeration temperatures. Absorption cooling plants are introduced into air conditioning applications on board the ship. They work with water/lithium bromide (H2O/LiBr) mixtures, thus increasing the efficiency of the plant and reducing the impact on the environment.