The interest in employing absorption refrigeration systems is usually related to electricity’s precariousness since these systems generally use thermal rejects for their activation. The application of these systems is closely linked to the concept of energy polygeneration, in which the energy demand to operate them is reduced, which represents their main advantage over the conventional vapor compression system. Currently, the solution pairs used in commercial absorption chillers are lithium bromide/water and ammonia/water. The latter pair has been used in air conditioning and industrial processes due to the ammonia operation’s low temperature. Few review papers on absorption chillers have been published, discussing the use of solar energy as the input source of the systems, the evolution of the absorption refrigeration cycles over the last decades, and promising alternatives to increase the performance of absorption refrigeration systems. There is a lack of consistent studies about designing requirements for absorption chillers, so an updated review covering recent advances and suggested solutions to improve the use and operation of those absorption refrigeration systems using different working fluids is relevant. Hence, this presents a review of the state-of-the-art of ammonia/absorbent based absorption refrigeration systems, considering the most relevant studies, describing the development of this equipment over the years. The most relevant studies in the open literature were collected to describe this equipment’s development over the years, including thermodynamic properties, commercial manufacturers, experimental and numerical studies, and the prototypes designed and tested in this area. The manuscript focuses on reviewing studies in absorption refrigeration systems that use ammonia and absorbents, such as water, lithium nitrate, and lithium nitrate plus water. As a horizon to the future, the uses of absorption systems should be rising due to the increasing values of the electricity, and the environmental impact of the synthetic refrigerant fluids used in mechanical refrigeration equipment. In this context, the idea for a new configuration absorption chiller is to be more efficient, pollutant free to the environment, activated by a heat substantiable source, such as solar, with low cost and compactness structure to attend the thermal needs (comfort thermal) for residences, private and public buildings, and even the industrial and health building sector (thermal processes). To conclude, future recommendations are presented to deal with the improvement of the refrigeration absorption chiller by using solar energy, alternative fluids, multiple-effects, and advanced and hybrid configurations to reach the best absorption chiller to attend to the thermal needs of the residential and industrial sector around the world.

This study applies the SPecific Exergy COsting (SPECO) methodology for the exergoeconomic assessment of a compact electricity-cooling cogeneration system. The system utilizes the exhaust gases from a 126 hp Otto-cycle internal combustion engine (ICE) to drive a 5 RT ammonia–water absorption refrigeration unit. Exergy destruction is higher in the ICE (67.88%), followed by the steam generator (14.46%). Considering the cost of destroyed exergy plus total cost rate of equipment, the highest values are found in the ICE, followed by the steam generator. Analysis of relative cost differences and exergoeconomic factors indicate that improvements should focus on the steam generator, evaporator, and absorber. The cost rate of the fuel consumed by the combustion engine is 12.84 USD/h, at a specific exergy cost of 25.76 USD/GJ. The engine produces power at a cost rate of 10.52 USD/h and specific exergy cost of 64.14 USD/GJ. Cooling refers to the chilled water from the evaporator at a cost rate of 0.85 USD/h and specific exergy cost of 84.74 USD/GJ. This study expands the knowledge base regarding the exergoeconomic assessment of compact combined cooling and power systems.

This study conducts a life cycle assessment and exergoenvironmental evaluation of a double-effect vapor absorption chiller (DEAC) with a cooling capacity of 352 kW, employing three different energy sources: natural gas, biomethane, and green hydrogen. The main objectives of this paper are as follows: (i) provide an exergoenvironmental model for DEAC technologies, (ii) evaluation of a case-study where a DEAC is used to cover the cooling demand of a specific university building in the Northeast of Brazil, and (iii) evaluate the scenario where the DEAC is fed by green hydrogen (GH2) and compare it with conventional energy resources (natural gas and biomethane). In order to develop the exergoenvironmental model, two methodologies are essential: a thermodynamic analysis and a Life Cycle Assessment (LCA). The thermodynamic analysis was carried out using the Engineering Equation Solver (EES: 10.998) software. The LCA has been developed through the open-source software openLCA version 1.10.3, with the Ecoinvent 3.7.1 life cycle inventory database, whereas the chosen life cycle inventory assessment (LCIA) method was the ReCiPe Endpoint LCA method (Humanitarian, medium weighting–H, A). The main results indicate that green hydrogen provides a 99.84% reduction in environmental impacts compared to natural gas during the operational phase, while biomethane reduces these impacts by 54.21% relative to natural gas. In the context of life cycle assessment (LCA), green hydrogen decreases fossil resource depletion by 18% and climate change-related emissions by 33.16% compared to natural gas. This study contributes to enhancing the understanding of the environmental and exergoenvironmental impacts of a double-effect vapor absorption chiller by varying the fuel usage during the operational phase.

The purpose of this study is to investigate articles published in the Scopus database dealing with multigeneration energy systems using biogas as fuel. This investigation was conducted by means of a bibliometric review. The free VOSviewer software was chosen to process this data, in which bibliometric networks were set up such as citations, co-authors, year of publication and keywords that listed relevant information from the articles. Based on these bibliometric networks, graphs and maps were added to this work, making it possible to infer and evaluate the results of the research field. The bibliometric review indicated that over the last two decades there has been a vertiginous growth in article production, with the last decade alone accounting for approximately 37% of all publications, even more than in the previous decade, which shows the growing interest in the subject. China leads the ranking of publications with approximately 22% of research on the subject and the top 4 countries, China, Italy, Iran and Germany, together account for approximately 60% of research. It can be concluded that these systems are increasingly studied and regarded as a promising model for energy sustainability.

Biogas, a promising fuel for present and future generations, is produced from the anaerobic digestion of organic waste generated by the condominium itself. Therefore, this work aims to evaluate the exergoeconomic performance of a biogas cogeneration unit designed to meet the electrical and thermal energy demands of a residential condominium in the city of Teresina, Piauí, Northeast Brazil. The cogeneration unit consists of an internal combustion engine (ICE) coupled to an electric generator (genset) to produce electricity, and a heat exchanger that recovers part of the exhaust-gas heat to heat water. The analysis was conducted based on the concepts of Thermodynamics and Exergoeconomics, using the SPECO (Specific Exergy Costing) methodology to define the exergetic costs of the system. The novelty of the work lies in applying the SPECO exergoeconomic analysis to a small-scale biogas cogeneration unit fueled by residential organic waste. The achieved electricity production was 167.40 kW, and the heat transfer rate at the exchange rate was 51.55 kW. The results revealed that the exergy destroyed in the internal combustion chamber (ICE) was 223.65 kW, whereas that in the heat exchanger was significantly higher at 45.67 kW. The exergy efficiency of the ICE reached 39.19%, and the heat exchanger efficiency was around 9%. In financial terms, the cost of exergy destroyed in the ICEC was USD/h 135, but in the heat exchanger, it was dramatically higher at USD/h 158.40. The cost of producing hot water (product) was considered extremely high (USD/GJ 38.98). The relative difference parameter in the heat exchanger also has a value much higher than expected (10.240). This is because the product’s cost (USD/GJ 38.98) is well above the cost of fuel (USD/GJ 3.468). This study concludes that the cogeneration unit is more justifiable by the savings generated through thermal energy production than by electricity production alone, since the cogeneration system significantly enhances performance, raising both the energetic and exergetic efficiencies to 55% and 48%, respectively, thereby confirming the added value of the simultaneous utilization of heat and power.

Nas últimas décadas, o mercado de refrigeradores e ar-condicionado dos segmentos industrial, comercial e residencial teve um crescimento muito expressivo. Para aplicações com temperaturas de evaporação extremamente baixas ou criogênicas, os ciclos de compressão de refrigeração de múltiplos estágios são preteridos porque apresentam a melhor relação entre os custos de investimento inicial da instalação e os de operação do equipamento durante o ciclo de vida. Neste contexto, a busca por maior eficiência energética na indústria de refrigeração tem impulsionado pesquisadores e fabricantes no desenvolvimento de novos fluidos refrigerantes e avanços tecnológicos em ciclos de refrigeração por compressão de vapor que promovam economia e maior sustentabilidade. Este artigo investiga a influência dos principais parâmetros operacionais no desempenho do ciclo termodinâmico de refrigeração multiestágio operando com diferentes refrigerantes naturais. O software Coolpack foi utilizado na simulação termodinâmica do ciclo de refrigeração de dois estágios com intercooler aberto para verificar a eficiência energética dos refrigerantes naturais selecionados: amônia (R717); Propano (R290); Butano (R600) ou isobutano (R600a). Os resultados da pesquisa mostram que a amônia (R717) e o butano (R600) são os refrigerantes naturais mais qualificados em termos de eficiência termodinâmica para operação no ciclo de refrigeração de dois estágios com intercooler aberto.