Thermo-ecological Analysis Research Articles

Thermo-ecological analysis of the power system based on renewable energy sources integrated with energy storage system

Energy systems based on Variable Renewable Energy (VRE) such as solar energy (PV, PV/T) and wind energy (wind turbine) are intermittent by weather and climate conditions. This poses challenges for managing to obtain a stable energy supply. Microgrids based on VRE must accommodate the variability using, for example, energy storage. The second options for adjustment are backup generators or sources with firm capacity cooperating with VRE. The article presents an analysis of individual RES sources PV, PV/T system, wind turbine and biogas plant indicating the advantages of individual components and the possibility of their cooperation in a microgrid. The analysis for the assumed climatic conditions (location: Katowice, Poland) showed the benefits of the combination in the energy mix sources based on solar radiation and wind energy. The analysis also covers the use of the energy stored (based on electrolyser, hydrogen store and fuel cell) and presents the possibilities of using energy storage technology in various options of the energy mix. The most advantageous was a mixed system based on renewable energy sources using solar irradiation and wind energy with the stabilizing participation of a biogas plant - in this case, the capacity of the energy storage was fully used. In the further part of the article an exergo-ecological analysis using the TEC concept (thermo-ecological cost) is presented. TEC indicators for different versions of the energy mix were presented, analysing the systems in terms of natural resource management. The thermo-ecological analysis showed that the best energy mixes in terms of assessing the efficiency of natural resource management are systems that use the advantages of each component, supporting by energy storage.

Energy prosumerism using photovoltaic power plant and hydrogen combustion engine: Energy and thermo-ecological assessment

Renewable Energy Sources (RES) represent an attractive way to save natural resources and improve the overall impact of power systems on the environment. A continuous increase of share of RES in national energy mixes is observed, and due to the energy policy of the European Union and many other countries, further increase is expected. A disadvantage of RES is their random, weather-dependent availability, which requires energy storage. A promising method of integrating RES with the energy system is the use of hydrogen as an energy carrier (e.g. coupling RES with electrolyzers in order to directly use the renewable electricity for production of hydrogen). In the present work, a simulation of cooperation of a photovoltaic power plant with a gas piston engine fueled by hydrogen was performed, with and without the presence of energy storage. The aim of the analysis is twofold. First, the “compensation losses” due to forced part-load operation of the engine coupled with RES are evaluated and compared with “storage losses” resulting from the thermodynamic imperfectness of the storage; this allows to calculate the minimum round-trip efficiency of storage required for positive energy effect. The “compensation losses” have been determined to be of the order of magnitude of 2%, and the minimum round-trip efficiency of storage to be at the level of 85%. Second, a thermo-ecological analysis was carried out to determine the impact of the source of hydrogen on the overall ecological effectiveness of the system. Contrary to the commonly used measure of “energy efficiency” describing a local balance boundary, thermo-ecological cost (TEC) evaluates the consumption of non-renewable exergy within a global balance boundary. The analysis confirmed that comparing various hydrogen production methods (especially renewable and non-renewable) in terms of local energy efficiency is inadequate, because it does not tell much about their sustainability. For a hydrogen energy system basing on the water electrolysis – hydrogen transport/storage – combustion in a gas piston engine pathway to be considered sustainable, the input electricity to the electrolysis process should be characterized by TEC lower than ∼0.15 J∗/J, a value which even some renewable energy sources fail to achieve.

Thermo-ecological analysis - The comparison of collector and PV to PV/T system

The use of solar radiation energy is one of the important elements to achieve energy transformation. This potential can be utilized by generating electricity with PV modules or heat from collectors. It is also possible to combine these elements into one system and more efficient use of solar radiation, as is the case with the Photovoltaic thermal collectors (PV/T system), which is considered in the article below. The amounts of produced electricity and heat are compared and the energy efficiency of electricity production by PV or PV/T. Local energy analysis from the point of view of resource efficiency, however, becomes insufficient, because it ignores the issue of the quality of individual energy carriers, therefore also in the rest of the article presents an exergo-ecological analysis using the TEC concept (thermo-ecological cost). It has been demonstrated that the TEC for generated carrier (electricity/heat) produced from solar radiation is lower for combined systems and depends on a few factors: the type of generated carrier and implementation of division of allocation of fuel between heat and electricity (for combined systems). Local analysis leads to conclusions other than the global one, as demonstrated by the results presented in the article.

Thermo-ecological assessment of Stirling engine with regenerator fed with cryogenic exergy of liquid natural gas (LNG)

The paper presents a thermo-ecological analysis of a liquefied natural gas regasification system equipped with a Stirling engine. The proposed system includes an alpha configuration machine, working as a cold engine with the heat sink acting as the evaporator for the LNG and the upper heat source being at ambient temperature (sea water) or moderately higher. The engines are modelled using two approaches developed by the authors, that is a CFD model and a second-order one-dimensional model. First a small engine is modelled by both CFD and the second order approach to compare results and after confirming their similarity, due to a lower computational cost a larger machine is modelled with the second order model. Due to the heat transfer conditions being crucial for a Stirling cycle machine's performance, those are investigated. It is shown that the internal, convective heat transfer coefficients are much higher in cryogenic conditions than in typical ones. The results of engine assessment are used for the Thermo-ecological cost (TEC) analysis. Within the thermo-ecological analysis, the influence of selected parameters is demonstrated. Additionally the TEC of electricity generated in cold power plant is presented for different configurations. In the case of analysed Stirling systems savings of natural gas reach the level of only 0.5%. However, when TEC of electricity is calculated, the savings are at the level of 72%. The proposed theoretical investigations are the base for the acquisition of new knowledge in the field of possible ways of converting cryogenic exergy of LNG into electricity and optimization of this cycle with strong focus on ecological effects, including the TEC.

Thermo-ecological analysis and optimization of a three-heat-reservoir absorption heat pump with two internal irreversibilities and external irreversibility

The investigations carried out in this work concern the optimization and the thermodynamic analysis of an absorption heat pump with multi-irreversibilities and provided with three-heat-reservoir mainly using the thermo-ecological criterion as objective function. The thermodynamic analysis of the first and second laws of thermodynamics and the linear law of heat-transfer allowed us to evaluate and optimize the objective functions of performance such as: the specific heating load, the coefficient of performance, the specific entropy generation rate, the ecological coefficient of performance and the heat-transfer areas of the various components. These allowed us to study the variations of these criteria according to the design parameters and the temperatures of the working fluid in the components. From this study, it follows that the optimal system implies a maximum thermo-ecological coefficient, a minimum entropy production rate corresponding to a certain value of the specific heating load, while maintaining a system which limits the losses between the condenser and the evaporator. Moreover, the consideration of the two internal irreversibilities, the external irreversibility and the losses of the heat resistances is very close to a real absorption heat pump and allows a more precise and objective study rather than in the optimization and the design of an absorption system like an endoreversible system.

Thermo-ecological analysis of industrial kilns

In this study, thermo-ecological analysis has been applied by using ecologic objective function "ECO" and ecological coefficient of performance "ECOP" to the kilns used in the firing process of the ceramic plant. Five different environmental (dead state) temperatures (between 10 °C and 30 °C) are taken into account. The irreversibility, which are the most important criteria affecting ecological performance, occurs during the heat transfer in the burners and cooling in the kiln. The irreversibility and product exergy values are compared under different environmental temperatures. The ECO and ECOP values are inversely proportional to the environment temperatures. The maximum ECO and ECOP values are determined as −2387.156 kW and 0.051, respectively, while their corresponding minimum values are −2577.394 kW and 0.026, respectively. The results obtained can be a guide for the thermo-ecological design of industrial kilns. The losses of the kiln are high. It is necessary to reduce the losses to increase the performance and ecologic indicator results. The kilns are not environmentally benign at higher ambient temperatures. The optimum working condition of the kiln can be considered as 10 °C. Better insulations are necessary for the side, bottom and top surfaces of the kilns to reduce the losses. In this regard, the waste heat recovery for the gases can be taken into account for better efficiency and environmental assessment.

Exergy-based ecological indicators: From Thermo-Economics to cumulative exergy consumption to Thermo-Ecological Cost and Extended Exergy Accounting

This paper presents a summary of the conceptual development and the practical applications of exergy-based Environmental Indicators. After a brief historical introduction, the two most popular methods are presented and discussed: the Exergo-Environmental Analysis (here TEA, as a memento of Jan Szargut's original denomination “Thermo-Ecological Analysis”, currently adopted also by Valero's school) and the Extended Exergy Accounting (EEA). Both emerged from Szargut's idea of the existence of a consumption index, the Cumulative Exergy Consumption (CExC), which can be used to quantify the consumption of primary resources “embodied” in a final product or service. The extension introduced by both methods with respect to CExC consists in the explicit inclusion in the exergy budget of one or more of the Externalities, lumped in the original CExC formulation into the exergetic material contents of the single commodities. The differences between the three formulations are obviously reflected in the numerical values of the resulting indicators. The Thermo-Ecological Cost (TEC) and the CExC differ because of the inclusion in the former of the exergetic resources that reflect the “penalty” in the use of primary non-renewable consumption caused by the anthropic intervention. The CExC index and the Extended Exergy Cost EEC differ because the latter explicitly includes in the calculation a “Labour and Capital equivalent exergy consumption” that allows for the survival of the individuals in a given region according to the respective life standards (variable in space and time). Another difference is the way the Environmental Externality is computed: while TEA takes an ex-post assessment, EEA introduces a calculation of the -ideal or real-remediation costs.

Thermoecological analysis of an oxy-fuel combustion power plant integrated with a CO2 processing unit

The paper presents a mathematical model of assessing the indices of thermoecological costs concerning an oxy-fuel combustion power plant integrated with a CO2 processing unit. Thermoecological cost is the measure of depletion of non-renewable natural resources. It expresses the cumulative consumption of exergy charging the production processes leading to the analyzed useful product. The additional consumption of exergy compensating the negative impact of harmful emissions has also been taken into account. The proposed model has been developed making use of “input–output analysis” which is an effective tool in modeling of large energy systems. The example of the analysis of thermoecological costs has been elaborated for three variants of an integrated power plant operating with oxy-fuel combustion (basic variant, ultra-supercritical steam parameters and advanced oxygen production) and one reference power plant without CO2 capture. The analysis of the degree of sustainable development has been realized in these four cases.

Thermo-ecological analysis and optimization performance of an irreversible three-heat-source absorption heat pump

Throughout present research, optimization investigations of an irreversible absorption heat pump system on the basis of a new thermo-ecological criterion. The objective functions which considered are the specific heating load, coefficient of performance (COP) and the ecological coefficient of performance (ECOP). Three objective functions of the ECOP, COP and the specific heating load are optimized simultaneously using the multi-objective optimization algorithm NSGAII. COP and ECOP are maximized and specific heating load is minimized in order to get the best performance. Decision making is done by means of three methods of LINAMP and TOPSIS and FUZZY. Finally, sensitivity analysis and error analysis was performed for the system.