1,720,998 research outputs found
Regulated emissions of biogas engines—on site experimental measurements and damage assessment on human health
Get PDFDespite biogas renewability, it is mandatory to experimentally assess its combustion products in order to measure their pollutants content. To this purpose, the Authors selected six in-operation biogas plants fed by different substrates and perform an on-site experimental campaign for measuring both biogas and engines exhausts composition. Firstly, biogas measured compositions are compared among them and with data available in literature. Then, biogas engines’ exhaust compositions are compared among them, with data available in literature and with measurements obtained from an engine characterised by the same design power but fuelled with natural gas. Finally, the Health Impact Assessment analysis is used to estimate the damage on human health caused by both biogas and natural gas engines emissions. Results show that biogas causes a damage on human health three times higher than the natural gas one. But, this approach does not consider biogas renewability. So, to include this important aspect, also an analysis which considers Global Warming categories is carried out. Results highlight that natural gas is twice harmful than biogas
Costs to reduce the human health toxicity of biogas engine emissions
Get PDFThe anaerobic digestion of biodegradable substrates and waste is a well-known process that can be used worldwide to produce a renewable fuel called biogas. At the time of writing, the most widespread way of using biogas is its direct usage in combined heat and power internal combustion engines (CHP-ICEs) to generate electricity and heat. However, the combustion process generates emissions, which in turn have an impact on human health. Therefore, there is a need to: (i) measure the ICE emissions (both regulated and unregulated), (ii) compute the impact on human health, (iii) identify the substances with the highest impact and (iv) calculate the avoided damage to human health per Euro of investment in technology able to abate the specific type of pollutant. To this end, the authors conducted an experimental campaign and selected as a test case a 999 kWel biogas internal combustion engine. Then, the collected data, which included both regulated and unregulated emissions, were used to calculate the harmfulness to human health and identify the more impactful compounds. Thus, combining the results of the impact analysis on human health and the outcomes of a market analysis, the avoided damage to human health per Euro of investment in an abatement technology was computed. In this manner, a single parameter, expressed in DALY e-1, provided clear information on the costs to reduce each disability-adjusted life year (DALY). The impact analysis on human health, which was performed using the Health Impact Assessment, showed that NOx was the main contributor to damage to human health (approximately 91% of the total), followed by SOx (6.5%), volatile organic compounds (1.4%) and CO (0.7%). Starting from these outcomes, the performed investigation showed that the technology that guarantees the maximum damage reduction per unit of cost is the denitrification system or the oxidizing converter, depending on whether the considered plant is already in-operation or newly built. This is an unexpected conclusion considering that the most impacting emission is the NOx
Prediction of penetration per revolution in TBM tunneling as a function of intact rock and rock mass characteristics
Get PDFA new empirical formulation is presented which can be used to estimate the penetration-per-revolution for TBM tunneling, derived from TBM monitoring data of alpine tunnels in the North-West of Italy. This formulation is easy to use and allows the contribution of both the intact rock and of the rock mass characteristics to be taken into account. The contribution of the intact rock is taken into consideration through the use of the uniaxial compression strength, while the influence of the rock mass is considered through the use of the GSI. A statistical interpretation procedure of numerous operative data from TBMs used for the excavation of tunnels in rock, and of the characterization of intact rock and of the rock mass, has been developed to determine the proposed formulation. In particular, the penetration-per-revolution (p) recorded during excavation, the forces applied to each disk (FN), the Geological Strength Index (GSI) and uniaxial compression strength of the intact rock (σc) along the stretch have been compared.The set-up formulation is simple to use and reliable for tunnels excavated in metamorphic rock, as it has successfully been compared with the TBM net advancement speed data of a well-known case history taken from the literature (the Maen tunnel in Italy). Comparisons with results obtained with the Norwegian School method (NTNU) and Barton[U+05F3]s calculation model have also led to positive result
A human health toxicity assessment of biogas engines regulated and unregulated emissions
Get PDFThe aim of the work is to evaluate the damage to human health arising from emissions of in-operation internal combustion engines fed by biogas. The need of including also unregulated emissions like polycyclic aromatic hydrocarbons (PAHs), aldehydes and dioxins and furans is twofold: (i) to cover the lack in biogas engine emissions measurements and (ii) to complete the picture on biogas harmfulness to human health by identifying the substances with the highest impact. To this purpose, an experimental campaign is conducted on six biogas engines and one fed by natural gas all characterised by an electric power of 999 kWel. Collected data are used to perform an impact analysis on human health combining the Health Impact Assessment and the Risk Assessment. Measurements show that PAHs, aldehydes and diossin and furans are almost always below the detection limit, in both biogas and natural gas exhausts. The carcinogenic risk analysis of PAHs for the two fuels established their substantial equivalence. The analysis of equivalent toxicity of dioxins and furans reveals that biogas is, on average, 10 times more toxic than natural gas. Among regulated emissions, NOx in the biogas engines exhausts are three times higher than those of natural gas. They are the main contributors to human health damage, with approximately 90% of the total. SOx ranks second and accounts for about 6% of the total damage. Therefore, (i) the contribution to human health damage of unregulated emissions is limited compared to the damage from unregulated emissions, (ii) the damage per unit of electricity of biogas engines exhausts is about three times higher than that of natural gas and it is directly linked to NOx, (iii) obtaining a good estimation of the human health damage from both biogas and natural gas engines emissions is enough of a reason to consider NOx and SOx
Analisi del Comportamento di una HAWT da 1.5 kW
Get PDFSystem dynamic modelling and simulation is becoming a powerful and essential design tool. For this reason, this Ph.D. Thesis is devoted to analyse the transient operation conditions’ effects using power plant dynamic models.
In the first part of this dissertation, the dynamic analysis is the core of a procedure developed to predict lifetime reduction on traditional power plant devices. In particular, the plant dynamic model, and its capability of evaluating the trends of
the main thermodynamic parameters, which describe the plant operation during transient conditions, is the base point to identify the most stressed plant devices.
Being fundamental the role played by combined cycle power plants in the liberalized electricity market scenario, a combined cycle power plant is selected as test case. The dynamic model of a single pressure combined cycle power unit is built and the proposed procedure is tested. The results show that the procedure can be considered as a valuable innovative tool to assist power plant designers and operators in order to improve the plant’s flexibility without excessively compromising the integrity of devices subjected to high thermo-mechanical stresses.
The second part of this work underlines the essential role played by the dynamic analysis during the design phase of innovative small-medium size waste heat recovery units on isolated grid. In particular, after a design optimization process, the dynamic behaviour of gas turbines coupled with waste heat recovery units
(ORC, SRC and ABC power units) is tested to verify the grid stability and, in the case of an ORC unit, the working fluid thermochemical stability.
In conclusion, in this dissertation, two different software tools are proposed. In both cases the core is the plant dynamic model. The first tool is able to predict the plant thermodynamic variables and compute the components lifetime reduction
caused by load changes while the second one performs a design and optimization of different waste heat recovery units for stand-alone offshore facilities. The entire plant is then dynamically analysed in order to verify the grid stability and, in the
case of ORC unit, the working fluid thermochemical stability
Impianto e Metodo per l’Accumulo di Energia e la Successiva Produzione di Energia Elettrica
No full textCorrigendum to "Dynamic behaviour analysis of a three pressure level Heat Recovery Steam Generator during transient operation" [Energy 90 (P2) (2015) 1595-1605] DOI: 10.1016/j.energy.2015.06.117
No full textPossible Ways of Extending the Biogas Plants Lifespan after the Feed-In Tariff Expiration
Get PDFEnergy production from biogas can play a pivotal role in many European countries, and specifically in Italy, for three main reasons: (i) fossil fuels are scarce, (ii) imports cover large shares of internal demand, and (iii) electricity and heat production from biogas is already a consolidated business. Nonetheless, in Italy, current legislation and incentive policies on electricity generation from biogas are causing a stagnation of the entire sector, which may lead to the shutting down of many in-operation plants in the years 2027–2028 and the consequent loss of 573 MWel over a total of 1400 MWel. This work aims to investigate the potential of revamping biogas power plants in prolonging operation until the end of the plants’ useful life, regardless of the implementation of a new government’s incentive schemes. Based on the time-series analysis of electricity prices in Italy and a case study representative of the vast set of in-operation power plants, our findings show that 700 plants will likely shut down between 2027 and 2028 unless the government adequately rewards electricity produced and fed into the grid via incentive schemes. In detail, our results show that the investment to revamp the plant exhibits a highly negative Net Present Value
Life cycle assessment of a commercially available organic Rankine cycle unit coupled with a biomass boiler
Get PDFOrganic Rankine Cycle (ORC) turbogenerators are a well-established technology to recover from medium to ultra-low grade heat and generate electricity, or heat and work as cogenerative units. High firmness, good reliability and acceptable efficiency guarantee to ORCs a large range of applications: from waste heat recovery of industrial processes to the enhancement of heat generated by renewable resources like biomass, solar or geothermal. ORC unit coupled with biomass boiler is one of the most adopted arrangements. However, despite biomass renewability, it is mandatory to evaluate the environmental impact of systems composed by boilers and ORCs taking into account the entire life cycle. To this purpose, the authors perform a life cycle assessment of a commercially available 150 kW cogenerative ORC unit coupled with a biomass boiler to assess the global environmental performance. The system is modelled in SimaPro using different approaches. Results show that the most impacting processes in terms of CO2 equivalent emissions are the ones related to biomass production and organic fluid leakages with 71% and 19% of the total. Therefore, being fluid release in the environment high impacting, a comparison among three fluids is also performed. Analysis shows that adopting a hydrofluoroolefin fluid with a low global warming potential instead of the hydrocarbon fluid as already used in the cycle guarantees a significant improvement of the environmental performance
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