Energy, exergy, and exergoeconomic evaluations of a micro-trigeneration system

Abstract

This study presents energy, exergy, and exergoeconomic assessments for a natural gas-fueled micro-trigeneration unit, which encompasses an internal combustion engine (ICE), an absorption refrigeration system (ammonia-water), and a heat recovery unit. The energy system is designed to meet the electricity and cooling demands of a university building, while heat is directed to a biodiesel plant located on site. The analyses comprehended energy and exergy parameters (first and second laws of thermodynamics). Then, the SPECO methodology was applied for the exergoeconomic assessment, which associates monetary values with exergy flows. The ICE presented the highest irreversibility (61.24 kW) and the highest cost of exergy destruction (21.56 BRL/h), followed by the steam generator (5.52 kW and 6.71 BRL/h, respectively). The exergoeconomic assessment indicated the components that could benefit from improvements: steam generator (cooling of exhaust gases before entry into the generator) and the heat exchanger of the absorber (substitution of the exchanger and/or pre-heating of input air). This study contributes to narrow the knowledge gap regarding the exergoeconomic assessment of compact trigeneration systems, besides making a case for the utilization of ICE as prime movers.

Exergoeconomic Assessment of a Compact Electricity-Cooling Cogeneration Unit

“…The same conclusions were obtained by Shokati et al [81,82]. As mentioned by Reference [33], such a level of knowledge on the cost-benefit assessment of improvements is provided by exergoeconomics only.…”

“…The values obtained for the ICE indicate that there are margins for improvement; however, this piece of equipment is commercially available and mass-produced, preventing interventions, and therefore, substituting the engine for another with higher efficiency has limited applicability. This approach was also followed by the authors of Reference [33], who identified that the absorber heat exchanger, steam generator, and heat recovery unit could benefit from improvements.…”

“…The results of exergoeconomic analyses can guide towards the cost-effective design and operation of energy systems. Marques et al [33] reported a detailed exergoeconomic assessment for a micro-trigeneration system, while Sharifi and Khalilarya [34] focused on a combined power and absorption-ejector refrigeration cycle. Hou et al [35] addressed a waste heat power generation project based on an Organic Rankine Cycle (ORC), and a novel ORC-based electricity-cooling cogeneration system was the focus of an exergoeconomic analysis and optimization by Kordlar and Mahmoudi [36].…”

Energy, exergy and exergoenvironmental analyses of a sugarcane bagasse power cogeneration system

“…As mentioned by Marques et al [50] , exergy-based assessments, along with their discussions, can stimulate the adoption of co- and trigeneration systems, which are more efficient. At the time of writing, the coronavirus (COVID-19) crisis is having a significant impact across the energy sector and is hindering low-carbon energy transitions.…”

Exergoeconomic and Environmental Modeling of Integrated Polygeneration Power Plant with Biomass-Based Syngas Supplemental Firing

“…In this regard, the energy access sector needs stimulus beyond the COVID-19 era. The combined energy generation systems were adjudged as veritable means to drive the energy access beyond the COVID-19 pandemic crisis, for efficient energy solutions aimed at enhancing economic competitiveness, providing more affordable energy services, and reducing environmental impact [5].…”