Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

Eboh, Francis Chinweuba; Ahlström, Peter; Richards, Tobias

doi:10.3390/en10020165

Cited by 26 publications

(22 citation statements)

References 83 publications

(107 reference statements)

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“…The EE indicates how efficiently all physical energy inputs to the process are converted to products and services. However, this metric ignores the range of quality and values among energy sources 52, 53 ; instead, it treats biorefinery product outputs as additive properties with the same relative value. In practice, biorefinery products are not interchangeable because they cannot be converted from one to another.…”

Section: Discussionsupporting

confidence: 88%

Green proteins: An energy‐efficient solution for increased self‐sufficiency in protein in Europe

Djomo

Knudsen

Martinsen

et al. 2020

Biofuels Bioprod Bioref

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The heavy reliance of the livestock industry of the European Union (EU) on feed protein imports has initiated a transition to alternative protein sources such as grass proteins. Green biorefineries (which process grass into protein and other related bio-products) are gaining interest in the EU as the EU searches for ways to cut its import of feed proteins, to reduce its reliance on fossil fuels, and to combat climate change. However, the vulnerability of green biorefineries to fossil energy constraints has not been studied. We estimated the energy conversion efficiencies (EE) and the energy return on investment (EROI) of bio-products from standalone (SGBR) and integrated grass refinery (IGBR) systems using scenario and energy analysis. The base scenario assumes an SGBR that processes grass into protein, fiber, and brown juice. The three IGBR scenarios assume that grass is processed into protein, fiber, and biomethane (Scenario 1); into protein, fiber, heat, and electricity (Scenario 2); or into protein, fiber, heat, and biomethane (Scenario 3). We found that the EE of the IGBR (83%-85%) largely exceeded that of the SGBR (77%) in all cases. Energy returns on investment were lower for grass than for clover-grass because of the high fertilizer needs of the former. The standard EROIs (EROI std ) for grass protein ranged from 1.6 to 5.4 over the various feedstocks and scenarios evaluated. The EROI std decreased when the system boundary was expanded to the point of use (EROI pou ), or when they were adjusted for quality (EROI qly ). Other bioproducts from both SGBR and IGBR also had high EROI std , and showed similar patterns to that of grass protein (i.e., EROI std > EROI pou > EROI qly ). Although Scenario 1 had a high EE relative to the base scenario, its heavy reliance on auxiliary energy inputs reduced the EROIs of its products. Our analysis showed the strong impacts of brown-juice recycling in the energy performance of green biorefinery. It thus deserves close attention when designing and implementing a green biorefinery in a given region. 606S Njakou Djomo et al.Modeling and Analysis: Energy Balance of Green Protein With favorable economic conditions, green biorefineries could contribute to the reduction of food and energy insecurity in Europe in a sustainable way.

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Section: Discussionsupporting

confidence: 88%

Green proteins: An energy‐efficient solution for increased self‐sufficiency in protein in Europe

Djomo

Knudsen

Martinsen

et al. 2020

Biofuels Bioprod Bioref

View full text Add to dashboard Cite

show abstract

“…The exergy efficiency of the system (η ex ) was assumed as the ratio between the useful exergy it provides (i.e., the exergy content of the thermal energy demanded by the industrial processes and also the net power output from cogeneration) and the total exergy fed to the boiler (Equation (8)) [37]. Eboh et al [13] agree that η ex is the most suitable parameter for evaluating the thermal system performance:…”

Section: Ex E (4)mentioning

confidence: 99%

“…These conclusions help explain the decrease of boiler exergy destruction in high-pressure cogeneration systems. All these options can reduce losses in terms of convection and radiation, which occur both in the pressure vessel and pipes [13,72]. According to Oliveira Jr. [44], an increase of the steam's working pressure, combined with the concept currently adopted for construction of high-pressure boilers, would also reduce energy losses and irreversibility.…”

Section: Thermodynamic Analysismentioning

confidence: 99%

Thermodynamic and Environmental Analysis of Scaling up Cogeneration Units Driven by Sugarcane Biomass to Enhance Power Exports

et al. 2018

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When manual harvesting of sugarcane was discontinued in many regions of Brazil, interest in power generation by burning the bagasse and straw in cogeneration units rose. Exergy analysis is often applied to increase the thermodynamic yield of these plants by identifying irreversibility and work availability. Conversely, pressure for adopting clean energy requires these systems to be evaluated for suitable environmental performance. This study identified and discussed the thermodynamic and environmental effects of scaling up systems that operate according Rankine cycle with reheating. Ten scenarios have been designed considering different levels of steam pressure and addition rates of straw remaining in the sugarcane cultivation. The thermodynamic analysis revealed a 37% improvement in the exergy efficiency and 63% of increasing in power generation to raise the steam pressure from 20 to 100 bar. Moreover, the use of 50% of residual straw into units operating at 100 bar can more than double the amount of electricity exported. If addressed considering a life cycle perspective, the use of straw improves the environmental performance of the cogeneration for Climate Change and Particle Matter Formation but provides additional impacts in terms of Water and Fossil resources depletions.

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“…This additional consumption is linked to the maintenance and operation of abatement installations as well as from the necessity of compensation of other losses in the environment. Under these assumptions the index of operational TEC can be determined by solving the set of thermo-ecological cost balance equations which general form is presented by Equation (18). The detailed description of the balance method with relevant examples is given in references [29,30,42]:…”

Section: Thermoeconomic and Thermoecological Analysismentioning

confidence: 99%

“…Moreover, it takes into account the quality difference between work and heat and/or cold at different temperatures [17]. Using the exergetic efficiency as the optimization criterion provide a direction for improving the overall efficiency of a power plant [18].…”

Section: Introductionmentioning

confidence: 99%

Exergo-Ecological Assessment of Waste to Energy Plants Supported by Solar Energy

et al. 2018

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Hybridization of Waste to Energy (WtE) plants with solar facilities can take competing energy technologies and make them complementary. However, realizing the benefits of the solar integration requires careful consideration of its efficiency. To analyse such systems from the point of view of resource efficiency, the pure energy analysis is not sufficient since the quality of particular energy carriers is not evaluated. This work applies the exergo-ecological analysis using the concepts of thermoecological cost (TEC) and exergy cost for the performance evaluation of an integrated Solar-Waste to Energy plant scheme, where solar energy is used for steam superheating. Different plant layouts, considering several design steam parameters as well as different solar system configurations, in terms of area of heliostats and size of the thermal storage tank, were studied. The results for the solar integrated plant scheme were compared with the scenarios where superheating is performed fully by a non-renewable energy source. The presented results of exergy cost analysis indicate that the most favorable system is the one supported by non-renewable energy. Such an analysis does not consider the advantage of the use of renewable energy sources. By extending the system boundary to the level of natural resource and applying the thermoecological cost analysis, an opposite result was obtained.

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Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review

Cited by 26 publications

References 83 publications

Green proteins: An energy‐efficient solution for increased self‐sufficiency in protein in Europe

Green proteins: An energy‐efficient solution for increased self‐sufficiency in protein in Europe

Thermodynamic and Environmental Analysis of Scaling up Cogeneration Units Driven by Sugarcane Biomass to Enhance Power Exports

Exergo-Ecological Assessment of Waste to Energy Plants Supported by Solar Energy

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