Thermo-economic Assessment of Small Scale Biomass CHP: Steam Turbines vs ORC in Different Energy Demand Segments☆

AbstractThe energy performance and profitability of CHP plants, and the selection of the optimal conversion technology and size, are highly influenced by the typology of energy demand (load-duration curve, temperature of heat demand, heat and electricity load patterns). In the small scale range, where CHP can be particularly promising to match local heat and power demand, the technologies based on boilers coupled to steam turbines (ST) and bottoming Organic Rankine Cycle (ORC) can be operated in flexible mode to match the energy demand. This is particularly important when high temperature heat is required (i.e. industrial end users). In the case of solid biomass fired CHP, the boiler + ST/ORC option could be competitive with the alternatives of boiler + Stirling engine, externally fired GT or gasification + ICE. In this paper, a thermo-economic comparison of the following biomass-CHP configurations is proposed: (A) boiler + ST + bottoming ORC, (B) boiler + ST, (C) boiler + ORC and (D) configuration (A) with option to switch on or off the bottoming ORC on the basis of the heat demand available. The focus is on a 1 MWt biomass boiler, and the plants are operated to serve residential (r), tertiary (t) and industrial (i) heat and power demand. The thermodynamic cycles are modeled by Cycle-Tempo, while the energy demand is modeled through simplified indicators (temperature of heat demand, equivalent thermal demand hours). On the basis of the results of thermodynamic simulations, upfront and operational costs assessment, and Italian energy policy scenario (feed-in tariffs for biomass electricity), the global energy conversion efficiency and investment profitability is estimated, for each CHP configuration and energy demand segment. The results indicate the optimal CHP configuration for each end user and the key technical and economic factors in the Italian legislative framework

\u201cNon \ue8 diverso da te\u201d. Una proposta di sensibilizzazione degli adolescenti al tema della salute mentale

L'articolo presenta un'esperienza di formazione e sensibilizzazione di studenti delle scuole superiori al tema della salute mentale e alcuni dei risultati della ricerca condotta in parallelo con i giovani per conoscere le loro opinioni sul tema prima e dopo la partecipazione a tale attivit\ue0

Externally Fired Micro-Gas Turbine and Organic Rankine Cycle Bottoming Cycle: Optimal Biomass/Natural Gas Combined Heat and Power Generation Configuration for Residential Energy Demand

Small scale combined heat and power (CHP) plants present lower electric efficiency in comparison to large scale ones, and this is particularly true when biomass fuels are used. In most cases, the use of both heat and electricity to serve on-site energy demand is a key issue to achieve acceptable global energy efficiency and investment profitability. However, the heat demand follows a typical daily and seasonal pattern and is influenced by climatic conditions, in particular in the case of residential and tertiary end users. During low heat demand periods, a lot of heat produced by the CHP plant is discharged. In order to increase the electric conversion efficiency of small scale micro-gas turbine for heat and power cogeneration, a bottoming organic Rankine cycle (ORC) system can be coupled to the cycle, however, this option reduces the temperature and the amount of cogenerated heat available to the thermal load. In this perspective, the paper presents the results of a thermo-economic analysis of small scale CHP plants composed of a micro-gas turbine (MGT) and a bottoming ORC, serving a typical residential energy demand. For the topping cycle, three different configurations are examined: (1) a simple recuperative micro-gas turbine fuelled by natural gas (NG); (2) a dual fuel externally fired gas turbine (EFGT) cycle, fuelled by biomass and natural gas (50% share of energy input) (DF); and (3) an externally fired gas turbine (EFGT) with direct combustion of biomass (B). The bottoming ORC is a simple saturated cycle with regeneration and no superheating. The ORC cycle and the fluid selection are optimized on the basis of the available exhaust gas temperature at the turbine exit. The research assesses the influence of the thermal energy demand typology (residential demand with cold, mild, and hot climate conditions) and CHP plant operational strategies (baseload versus heat-driven versus electricity-driven operation mode) on the global energy efficiency and profitability of the following three configurations: (A) MGT with cogeneration; (B) MGTþ ORC without cogeneration; and (C) MGTþORC with cogeneration. In all cases, a back-up boiler is assumed to match the heat demand of the load (fed by natural gas or biomass). The research explores the profitability of bottoming ORC in view of the following trade-offs: (i) lower energy conversion efficiency and higher investment cost of biomass input with respect to natural gas; (ii) higher efficiency but higher costs and reduced heat available for cogeneration with the bottoming ORC; and (iii) higher primary energy savings and revenues from feed-in tariff available for biomass electricity fed into the gri

Dynamic Validation and Sensitivity Analysis of a NOx Estimation Model Based on In-Cylinder Pressure Measurement

The incoming RDE regulation and the on-board diagnostics -OBDpushes the research activity towards the set-up of a more and more efficient after treatment system. Nowadays, the most common after treatment system for NOx reduction is the selective catalytic reduction -SCR- . This system requires as an input the value of engine out NOx emission -raw- in order to control the Urea dosing strategy. In this work, an already existing grey box NOx raw emission model based on in-cylinder pressure signal (ICPS) is validated on two standard cycles: MNEDC and WLTC using an EU6 engine at the test bench. The overall results show a maximum relative error of the integrated cumulative value of 12.8% and 17.4% for MNEDC and WLTC respectively. In particular, the instantaneous value of relative error is included in the range of ± 10% in the steady state conditions while during transient conditions is less than 20% mainly. Finally, a sensitivity analysis is conducted in order to understand how the model “answers” to any air and fuel parameter deviation

Cycle configuration analysis and techno-economic sensitivity of biomass externally fired gas turbine with bottoming ORC

This paper focuses on the energy analysis of a combined cycle composed by a topping 1.3 MW Externally Fired Gas Turbine (EFGT) with direct combustion of biomass and a bottoming Organic Rankine Cycle (ORC). A non recuperative scheme is assumed for the EFGT in order to avoid the costs of the recuperator. This scheme presents lower conversion efficiency in comparison to a recuperative one, however the heat available for the bottoming cycle is at a higher temperature (about 400 °C). In the present work, evaporation pressure and superheating temperature of ORC cycle are ranged in order to examine different bottoming cycles, including supercritical ones. Different organic fluids are investigated, such as siloxanes and toluene, aiming to analyze how the fluid choice influences both the plant performance and important features for the ORC turbine design. On the basis of the results of the thermodynamic simulation, a thermo-economic assessment is proposed, to investigate the profitability of the bottoming ORC in comparison to only topping EFGT, and the most influencing techno-economic factors that influence the selection of the optimal cycle. In order to propose real case studies, the Italian bioenergy subsidy framework is assumed, and the sensitivity assessment includes the options of only electricity and CHP, at different biomass cost, thermal energy demand and heat selling price values

Parathyroid-gland ultrasonography in clinical and therapeutic evaluation of renal secondary hyperparathyroidism

This study evaluated the relationship between ultrasonographic (US) parameters of parathyroid glands (PTGs) in haemodialysis patients (HDP) and degree of secondary hyperparathyroidism (SHPT), therapeutic responsiveness and type of PTG hyperplasia (diffuse or nodular)