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1

Exergetic performance coefficient analysis of direct methanol fuel cell

Guo Xinjia, Lu Zhanghao, Ma Zheshu, Song Hanling, Wang Yuting

Archives of Thermodynamics

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2024

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Vol. 45, no. 3

185--195

EN

In order to improve the output performance of direct methanol fuel cell, the finite-time thermodynamic model of direct methanol fuel cell is developed in this paper. Then, mathematical expressions for energy efficiency, power density, exergy efficiency and exergy coefficient of performance are derived. In addition, the effects of operating temperature, inlet pressure and membrane thickness on the performance of direct methanol fuel cells are considered. The results show that the exergetic performance coefficient not only considers the exergy loss rate to minimize the loss, but also the power density of the direct methanol fuel cell to maximize its power density and improve its efficiency. Therefore, the exergetic performance coefficient is a better performance criterion than conventional power and efficiency. In addition, increasing the inlet pressure and decreasing the membrane thickness can significantly improve the exergetic performance coefficient and energy efficiency.

2

Energy and exergy evaluation of tri-generation system based on natural gas fired micro-turbine - a case study

Gąsiorowski Piotr, Mróz Tomasz

Instal

|

2023

|

nr 11

9--13

EN

The need of significant reduction of energy supply to building sector joined with new European Union regulations, known as Green Deal, requires application of energy and exergy efficient solutions of energy production and distribution. One of the feasible options is use of co-generation and tri-generation energy systems in the small scale. The article presents the study on application of natural gas fired tri-generation system based on gas fired micro-turbine. The system consists of natural gas fired micro-turbine and heat exchanger which produces heat for space heating and ventilation and for cooling energy production in single stage absorption water chiller. The system operates whole year providing fixed electricity production - electrical power NEl, and heating/cooling energy production varying depending on building requirements. As a case study small office building of 1632 m2 useable area has been chosen. Energy and exergy models of evaluated system have been presented. It has been found that annual average energy and exergy efficiencies of the system are low - 0,339 and 0,247 respectively. It is due to the limited utilization of enthalpy and exergy of flue gas in heat exchanger.

PL

Konieczność znaczącego ograniczenia potrzeb energetycznych budynków związana z najnowszą strategią Unii Europejskiej znaną jako Zielony Ład, wymaga stosowania efektywnych energetycznie rozwiązań w zakresie produkcji i dystrybucji energii. Jedną z możliwych do realizacji opcji jest wykorzystanie systemów ko-generacyjnych i tri-generacyjnych małej mocy. W artykule przedstawiono studium zastosowania układu tri-generacyjnego małej mocy opartego o mikroturbinę gazową. Układ składa się z mikroturbiny gazowej z wymiennikiem ciepła dostarczającym ciepło do układu ogrzewania i wentylacji budynku oraz absorpcyjnej jednostopniowej wytwornicy wody lodowej. Układ pracuje przez cały rok zapewniając stałą produkcję mocy elektrycznej - NEl, i produkcję mocy cieplnej/chłodniczej zależną od potrzeb budynku. Jako studium przypadku przyjęto mały budynek biurowy o powierzchni użytkowej 1632 m2. Dla potrzeb analizy stworzone zostały modele energetyczny i egzergetyczny układu. Wyniki analizy wykazały niską średnioroczną sprawność energetyczną i egzergetyczną układu - odpowiednio 0,339 i 0,247. Jest to związane z ograniczonym wykorzystaniem entalpii i egzergii spalin przepływających przez wymiennik ciepła.

3

Thermodynamic assessment of thermochemical cycle for hydrogen production based on water decomposition with binary copper chlorine couple

Benbrika Omar, Bensenouci Ahmed, Tegar Mohamed, Ismail Kamal R. A.

Archives of Thermodynamics

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2022

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Vol. 43, no. 4

109--133

EN

The present study aims at investigating and simulating the hydrogen cycle production at low temperatures using thermochemical reactions. The cycle used in this work is based on the dissociation of water molecules depending on a copper chlorine couple. Furthermore, the proposed method uses mainly thermal energy provided by a solar thermal field. This proposed cycle differs from what is found in the literature. However, most of the thermochemical cycles for hydrogen production work at quite high temperatures which is a technical challenge. Therefore, the maximum temperature used in the present cycle is limited to 500°C. A thermodynamic analysis based on both the first and second laws is performed to evaluate the energy, exergy and efficiency of each reaction as well as the overall exergetic efficiency of the system. Furthermore, a parametric study is conducted to figure out the impact of the surrounding temperatures on the overall exergetic efficiency using commercial energy simulation software. The results show that the cycle can achieve an exergy efficiency of 30.5%.

4

Performance of a combined cycle power plant due to auxiliary heating from the combustion chamber of the gas turbine topping cycle

Khan Mohammad Nadeem

Archives of Thermodynamics

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2021

|

Vol. 42, no. 1

147--162

EN

Energy demand is increasing exponentially in the last decade. To meet such demand there is an urgent need to enhance the power generation capacity of the electrical power generation system worldwide. A combined-cycle gas turbines power plant is an alternative to replace the existing steam/gas electric power plants. The present study is an attempt to investigate the effect of different parameters to optimize the performance of the combined cycle power plant. The input physical parameters such as pressure ratio, air fuel ratio and a fraction of combustible product to heat recovery heat exchanger via gas turbine were varied to determine the work output, thermal efficiency, and exergy destruction. The result of the present study shows that for maximum work output, thermal efficiency as well as total exergy destruction, extraction of combustible gases from the passage of the combustion chamber and gas turbine for heat recovery steam generator is not favorable. Work output and thermal efficiency increase with an increase in pressure ratio and decrease in air fuel ratio but for minimum total exergy destruction, the pressure ratio should be minimum and air fuel ratio should be maximum.

5

Exergetic sustainability indicators of a polymer electrolyte membrane fuel cell at variable operating conditions

Xu Bing, Chen Yan, Ma Zheshu

Archives of Thermodynamics

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2021

|

Vol. 42, no. 1

183--204

EN

Based on the exergetic sustainability indicators of polymer electrolyte membrane (PEM) fuel cell, this paper studied the effects of irreversibility of thermodynamics on some exergetic sustainability indicators of PEM fuel cell under changing operating temperature, operating pressure and current density. Some conclusions are drawn by analyzing the curves. As the operating temperature increases, the negative impact of PEM fuel cell on various parameters due to irreversibility decreases; As the operating pressure increases, the negative impact of PEM fuel cell on various parameters due to irreversibility decreases; On the other hand, with the increase of current density, the negative impact of the PEM fuel cell on various parameters due to irreversibility increases.

6

An experimental study of solar air heater using arc shaped wire rib roughness based on energy and exergy analysis

Ghritlahre Harish Kumar

Archives of Thermodynamics

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2021

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Vol. 42, no. 3

115--139

EN

In the present study, energy and exergy analysis has been evaluated for roughened solar air heater (SAH) using arc shaped wire ribs. To achieve this aim, two different types of flow arrangement have been considered. These arrangements are: apex upstream flow and apex downstream flo. In addition to this, a smooth duct SAH has been used for comparative study. The experiments were performed using the mass flow rate of 0.007– 0.022 kg/s on outdoor condition at Jamshedpur city of India. The absorber plate roughness geometry has been designed with relative roughness height 0.0395, rib size 2.5 mm, relative roughness pitch 10 and arc angle 60◦ . The energetic and exergetic performances have been examined on the basis of the first and second law of thermodynamics. According to the results, there is observed to be the maximum thermal efficiency and exergy efficiency as 73.2% and 2.64%, respectively, for apex upstream flow SAH at 0.022 kg/s, while, at same mass flow rate the maximum thermal efficiency and exergy efficiency is obtained as 69.4% and 1.89%, respectively, for apex downstream flow SAH. In addition to this, results reported that the maximum outlet temperature and temperature difference observed at lower mass flow rate. Also examined the outlet air temperature of SAH with various mass flow rates is very important for both analysis.

7

Exergy life cycle assessment indicators in Colombian gold mining sector

Cano Natalia A., Hasenstab Christian, Velásquez Héctor I.

Journal of Sustainable Mining

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2020

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Vol. 19, iss. 3

151--165

EN

Thermodynamic methods, such as exergy analysis allow the assessment of environmental load (environmental impacts), by calculating the entropy generated or exergy destroyed due to the use of renewable and non-renewable resources along the entire production chain. In this research, exergy analysis will be approached as an extension of LCA to ExLCA (Exergy Life Cycle Assessment), as complementary tools, for sustainability assessment of two gold mining systems in Colombia: open-pit and alluvial mining. It is quantified exergy life cycle efficiencies; Cumulative Energy/ Exergy Demand, by distinguishing between renewable and non-renewable resources used in the process. The energy contained in renewable and non-renewable resources, interpreted as a measure of its utility potential, and which inefficient use generates waste streams with an exergy content that may be a measure of its potential to cause environmental damage. For open-pit mining 53% of exergy consumed comes from fossil energy, and 26% of energetic use of water, while in alluvial mining, 94% of exergy flow comes from water as a resource used within process activities. In order to reduce the environmental impact associated with gold generation life cycle described in this study, four strategies should be implemented; 1) Increasing efficiency, by reducing the exergy required in tails and extraction stages in open-pit mining process and, casting and molding stage in alluvial mining process, where large exergy supplies are required. 2) Increasing efficiency through the reduction of exergy emissions and residues in casting and molding stage in alluvial mining, and stripping stage in open-pit mining. 3) Using external exergy resources, such as renewable resources from nature (solar, wind, hydraulic). 4) Applying the concept of circular economy, which implies the reduction in consumption of resources.

8

Exergy-based control strategy in a dwelling ventilation system with heat recovery

Voloshchuk Volodymyr, Polishchuk Mariya

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2020

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T. 10, nr 2

44--47

EN

The paper presents energy and exergy analysis of a typical dwelling ventilation system with heat recovery for Ukrainian climatic conditions using a quasi-steady state approach over 24-hour time-steps. Evaluation of such systems on the base of the first law of thermodynamics demonstrates that heat recovery is beneficial for the whole variety of operational modes. Such methodology identifies as a thermodynamic inefficiency only energy losses to the surroundings with the exhaust air. The exergy-based analysis can detect additional inefficiencies due to irreversibilities within the components of the system. As a result the exergetic investigations show that for the ventilation systems there are operating conditions for which heat recovery increases exergy of fuel expended to provide the ventilation air compared to cases without bringing any recovery of heat and additional power consumption to drive the air flow by the fans. For the specified system, in case of switching ventilation unit to the operation mode of lower values of spent fuel exergy it is possible to provide annual saving of the primary energy sources from 5 to 15%.

PL

W pracy przedstawiono analizę energetyczną i egzergetyczną typowego systemu wentylacji mieszkań z odzyskiem ciepła dla ukraińskich warunków klimatycznych z zastosowaniem podejścia quasi-stabilnego w 24-godzinnych krokach czasowych. Ocena takich systemów w oparciu o pierwsze prawo termodynamiki wykazuje, że odzysk ciepła jest korzystny dla całego szeregu trybów pracy. Taka metodologia identyfikuje jako nieefektywne termodynamicznie tylko straty energii do otoczenia wraz z powietrzem wylotowym. Analiza egzergetyczna może wykryć dodatkowe nieefektywności wynikające z nieodwracalności elementów systemu. W rezultacie badania egzergetyczne wykazują, że w systemach wentylacyjnych występują warunki pracy, dla których odzysk ciepła zwiększa egzergię paliwa zużytego do dostarczenia powietrza wentylacyjnego w porównaniu do przypadków, w których nie występuje żaden odzysk ciepła i dodatkowe zużycie energii elektrycznej do napędzania przepływu powietrza przez wentylatory. Dla określonego systemu, w przypadku przełączenia urządzenia wentylacyjnego na tryb pracy o niższych wartościach egzergii zużytego paliwa możliwe jest zapewnienie rocznych oszczędności pierwotnych źródeł energii od 5 do 15%.

9

A comprehensive review on energy and exergy analysis of solar air heaters

Ghritlahre Harish Kumar, Sahu Piyush Kumar

Archives of Thermodynamics

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2020

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Vol. 41, no. 3

183--222

EN

For economic growth of nation, the energy plays an important role. The excessive use of fossil fuels results the increase in global warming and depleting the resources. Due to this reason, the renewable energy sources are creating more attraction for researchers. In renewable energy sector, solar energy is the most abundant and clean source of energy. In solar thermal systems, solar air heater (SAH) is the main system which is used for heating of air. As it is simple in construction and cheaper in cost, it is of main interest for the researchers. The concept of first law and second law of thermodynamics is used for the study of the energy and exergy analysis respectively. The energy analysis is of great importance for the study of process effectiveness while the exergetic analysis is another significant concept to examine the actual behavior of process involving various energy losses and internal irreversibility. For efficient utilization of solar energy, the exergy analysis is very important tool for optimal design of solar air heaters. The aim of the present work is to review the works related to energy and exergy analysis of various types of solar air heaters and to find out the research gap for future work.

10

Exergetic, environmental and economic assessment of sugarcane first-generation biorefineries

Silva Ortiz Pablo A., Flórez-Orrego Daniel, Oliveira, Jr Silvio de, Maréchal François, Maciel Filho Rubens

Journal of Power Technologies

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2019

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Vol. 99, nr 2

67--81

EN

First generation ethanol (1G) contributes to the majority of the ethanol produced worldwide, predominantly centered on corn and sugarcane. Nevertheless, several issues are regularly highlighted concerning the long-term sustainability of this technology, including its intensive water and land use, potential contamination of soils through the distillation residues, as well as the balance between fuel and food crops. Accordingly, in this study, a process design approach for biomass to ethanol production (1G ethanol technology) from sugarcane was performed by using Aspen Plus® software, based on the autonomous distillery (AUT, ethanol production) and the annexed plant (ANX, joint ethanol and sugar production) configurations. In addition, a performance comparison in respect to the exergy efficiency and the irreversibility as quality indicators of the conversion processes is carried out to identify potential improvements in the production facilities. Hence, the shortcomings of the techno-economic assessment of ethanol production can be overcome by using exergy efficiency as a suitable indicator for process performance. Moreover, the technical/sustainability aspects related to the process design of the sugarcane biorefineries are discussed in light of the renewability exergy index (λ). In general, the ANX plant has a saving in the process irreversibility rate of about 6%, whereas the average unitary exergy cost is 10% lower (AUEC= 2.41 kJ/kJ), in contrast to the AUT distillery. Moreover, a techno-economic analysis was carried out to assess the annexed plant and the autonomous distillery systems, considering the estimated capital expenditure. The results indicated that the ANX biorefinery has higher capex than the AUT distillery. It is noted that the higher investments are associated with sugarcane reception, ethanol production (juice extraction) and the combined heat and power sub-systems. Concerning system performance, the ANX plant presented a better overall exergy efficiency, with 41.39 %. Although this multi-criteria analysis is applied to 1G ethanol technology; it may be well-matched for various biorefineries/bioprocesses as a methodology to support decision-making as concerns potential improvement, well ahead of detailed process design.

11

Simplified exergy analysis of ship heating systems with different heat carriers and with the recovery of waste heat

Zeńczak Wojciech

Archives of Thermodynamics

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2019

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Vol. 40, no. 3

211-228

EN

The application of waste heat from exhaust gas of ship’s main engines has become widely practiced as early as in the 1930s. Thus the increase of ship’s overall efficiency was improved. Nowadays all newly built ships of the 400 gross tonnage and above must have specified energy efficiency design index, which is a measure for CO2 emissions of the ship and its impact on the environment. Therefore, the design of waste heat recovery systems requires special attention. The use of these systems is one of the basic ways to reduce CO2 emissions and to improve the ship’s energy efficiency. The paper describes the ship’s heating systems designed for the use of waste heat contained in the exhaust gas of self-ignition engines, in which the heat carriers are respectively water vapor, water or thermal oil. Selected results of comparative exergy analysis of simplified steam, water and oil heating systems have been presented. The results indicate that the oil heating system is comparable to the water system in terms of internal exergy losses. However, larger losses of exergy occur in the case of a steam system. In the steam system, a significant loss is caused by the need to cool the condensate to avoid cavitation in boiler feed pumps. This loss can in many cases cause the negative heat balance of ship during sea voyage while using only the exhaust gas boilers.

12

Exergetic Analysis of Hybrid Photovoltaic - Thermal Solar Collectors Coupled to Organic Rankine Cycles

Pinto C., Mady C. E.

Civil and Environmental Engineering Reports

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2018

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Vol. 28, no. 4

1--12

EN

In this work, the application of hybrid solar modules that combine photovoltaic panels and solar thermal collectors coupled with a low-temperature thermal cycle such as the Organic Rankine Cycle is discussed, their main purpose being an increase in the total electric power production per available area. This work will study the thermal and electrical power production efficiency of the hybrid system, the increase in the PV module electric conversion efficiency due to their cooling through heat transfer to the thermal cycle and the total exergetic efficiency of the system. A simplified simulation of the system in steady state conditions based on a thermal efficiency model will be performed with the aid of the EES (Engineering Equation Solver) software using climate data from Campinas, São Paulo, Brazil. The study shows that while the PV/T+ORC system does fulfill the purpose of increasing the electrical power generation both from the generator coupled to the thermal cycle and from the increase in the PV module efficiency due to its cooling. Thus, there is an increase the overall exergy efficiency of the system compared to uncoupled PV/T collectors.

PL

W pracy omówiono zastosowanie hybrydowych modułów słonecznych łączących panele fotowoltaiczne z kolektorami słonecznymi w połączeniu z niskotemperaturowym cyklem termicznym, takim jak cykl organiczny Rankine'a, którego głównym celem jest zwiększenie całkowitej produkcji energii elektrycznej. W pracy zbadano wydajność produkcji energii cieplnej i elektrycznej w systemie hybrydowym, wzrost sprawności konwersji energii modułu fotowoltaicznego ze względu na ich chłodzenie poprzez przeniesienie ciepła do cyklu termicznego i całkowitą efektywność energetyczną układu. Uproszczona symulacja systemu w warunkach stanu ustalonego w oparciu o model sprawności cieplnej została przeprowadzona za pomocą oprogramowania EES (Engineering Equation Solver) wykorzystującego dane klimatyczne z Campinas, São Paulo, Brazylia. Badania wykazały, że system PV/T + ORC spełnia cel zwiększenia wytwarzania energii elektrycznej zarówno z generatora połączonego z cyklem termicznym, jak i ze wzrostu sprawności modułu PV ze względu na jego chłodzenie. W ten sposób zwiększa się ogólna efektywność egzergii systemu w porównaniu z niezwiązanymi kolektorami PV/T.

13

Zagospodarowanie ciepła odpadowego z biogazowych agregatów kogeneracyjnych w oczyszczalni ścieków

Bajor M., Wajs J., Mikielewicz D.

Rynek Energii

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2016

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Nr 4

22--30

PL

W pracy opisano koncepcję współpracy biogazowych modułów kogeneracyjnych z niskotemperaturowym obiegiem parowym. Proponowana modernizacja pozwoliłaby na wykorzystanie entalpii fizycznej spalin, tym samym zwiększając sprawność urządzeń wytwarzających ciepło i energię elektryczną. Tego typu rozwiązanie umożliwiłoby częściowe pokrycie zapotrzebowania własnego na energię elektryczną, generując oszczędności w przedsiębiorstwie. W artykule przedstawiono koncepcję wykorzystania ciepła odpadowego w obiegu Clausiusa Rankine'a z turbiną kondensacyjną. Dodatkowo jako alternatywną formę zagospodarowania ciepła odpadowego rozważono zastosowanie organicznego obiegu Rankine'a (ORC), w którym jako czynnik roboczy zaproponowano alkohol etylowy. Dla przedstawionego rozwiązania wykonano analizę termodynamiczną i egzergetyczną oraz zaprezentowano wstępną ocenę ekonomiczną i ekologiczną proponowanej modernizacji.

EN

In the paper the idea of combined operation of the biogas CHP module with the low-temperature cycle is presented. The proposed modernization would allow utilization of exhaust gases enthalpy to increase efficiency of thermal and electrical energy production. This solution allows partial covering of the local electricity demand and at the same time causes savings and unloads the electrical power system. The article presents the concept of the waste heat utilization in Rankine cycle with a condensing turbine. Additionally, Organic Rankine Cycle (ORC) with ethanol as a working fluid was considered as an alternative form of waste heat. For the modernization thermodynamic and exergy analyses were carried out. Some basic economical and ecological indicators were also discussed.

14

Performance analysis of multipurpose refrigeration system (MRS) on fishing vessel

Ust Y., Karakurt A., Gunes U.

Polish Maritime Research

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2016

|

nr 2

48--56

EN

The use of efficient refrigerator/freezers helps considerably to reduce the amount of the emitted greenhouse gas. A two-circuit refrigerator-freezer cycle (RF) reveals a higher energy saving potential than a conventional cycle with a single loop of serial evaporators, owing to pressure drop in each evaporator during refrigeration operation and low compression ratio. Therefore, several industrial applications and fish storage systems have been utilized by using multipurpose refrigeration cycle. That is why a theoretical performance analysis based on the exergetic performance coefficient, coefficient of performance (COP), exergy efficiency and exergy destruction ratio criteria, has been carried out for a multipurpose refrigeration system by using different refrigerants in serial and parallel operation conditions. The exergetic performance coefficient criterion is defined as the ratio of exergy output to the total exergy destruction rate (or loss rate of availability). According to the results of the study, the refrigerant R32 shows the best performance in terms of exergetic performance coefficient, COP, exergy efficiency, and exergy destruction ratio from among the other refrigerants (R1234yf, R1234ze, R404A, R407C, R410A, R143A and R502). The effects of the condenser, freezerevaporator and refrigerator-evaporator temperatures on the exergetic performance coefficient, COP, exergy efficiency and exergy destruction ratios have been fully analyzed for the refrigerant R32.

15

Układy gazowo-parowe z CO2 jako czynnikiem roboczym

Lepszy S., Chmielniak T.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2015

|

z. 87 [291], nr 2

127--134

PL

W procesie rozwoju technologii energetycznych istotne miejsce zajmują technologie wykorzystania ciepła odpadowego i technologie wykorzystania ciepła niskotemperaturowego. Jednym z najpopularniejszych obiegów wykorzystywanych w tym celu jest obieg Rankine’a. Wykorzystanie dwutlenku węgla jako czynnika roboczego zarówno w obiegach o ciśnieniu nadkrytycznym, jak i obiegach transkrytycznych cechuje się wieloma zaletami w porównaniu z tradycyjnymi obiegami wykorzystującymi parę wodną. Najistotniejsze z nich są związane z rozmiarami maszyn i urządzeń. Dwutlenek węgla jest również czynnikiem dostępnym, o małym potencjale wpływu na warstwę ozonową w porównaniu z innymi czynnikami organicznymi. W pracy przedstawiono analizę układu gazowo-parowego z CO2 jako czynnikiem roboczym. W szczególności określono podstawowe parametry energetyczne oraz straty egzergii w wymiennikach ciepła.

EN

In the process of the development of energy systems, waste heat recovery and low temperature technologies occupy an important place. One of the most common system used for this purpose is the Rankine cycle. The use of carbon dioxide as the working medium in both the superand sub critical pressure cycles has several advantages compared to traditional steam cycles. The most important advantages are associated with dimensions of machines and equipment. Carbon dioxide is also a common medium, with a low potential impact on the ozone layer as compared to other organic mediums. The paper presents an analysis of different configurations of the gas-steam cycles with CO2 as the working fluid. In particular, the basic parameters of the energy analysis were determined and exergy losses are specified.

16

Analiza egzergetyczna suszenia próżniowego

Skoneczna-Łuczków J., Ciesielczyk W.

Przemysł Chemiczny

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2015

|

T. 94, nr 3

400-404

PL

Zaprezentowano wyniki teoretyczno-doświadczalnej analizy suszenia zrębek leszczyny pospolitej w suszarce próżniowej pod kątem minimalizacji nakładów energetycznych. Zastosowano bilansowanie egzergetyczne, które pozwoliło wykazać, jak parametry procesowe wpływają na efektywność suszenia. Wyższe sprawności uzyskano przy wymianie powietrza, dla wyższych wartości podciśnienia w komorze, przy większej masie próbki i dla wyższych nastaw temperatur.

EN

Hazel wood chips (sample mass 120–325 g) were dried in air under lab. conditions at 40–60°C and vacuum 0.05–0.07 MPa for 400 min to det. the exergy efficiency of the process. The efficiency increased with increasing the sample mass, temp., and vacuum. The air exchange during drzing resulted also in increasing the exergy efficiency.

17

Review of hydrogen production technologies for auto-motive sector – thermodynamic analysis of energy and exergy losses

Kowalczyk T., Badur J.

Logistyka

|

2015

|

nr 4

9232--9237, CD3

EN

Few recent years has shown that hydrogen technology has a good chance to replace petroleum technology in automotive sector. However, hydrogen in pure form practically does not occur on Earth. That is why H2 form is used only as an energy carrier and it must be produced using another source of energy form water or hydrocarbon fuels. In this paper short overview of hydrogen production technology has been presented, with energy and exergy analysis of four chosen technologies. Water and steam splitting using PEM as efficient and technically the simplest methods, SOEC as an industrial high effective thermoelectric process and thermochemical decomposition as non-electric alternative.

PL

W ciągu kilku ostatnich lat udowodniono, że w sektorze motoryzacyjnym technologia wodorowa ma realne szanse zastąpić ropie naftową. Jednakże wodór w stanie wolnym praktycznie nie występuje na Ziemi. Z tego powodu wodór w postaci cząsteczkowej może być traktowany jedynie jako nośnik, a nie źródło energii i musi być wytworzony używając innego źródła energii z wody lub paliw hydrowodorowych. W niniejszej pracy pokrótce zostały przedstawione technologie produkcji wodoru z analizą energetyczną i egzergetyczną czterech z nich. Hydrolizy wody i pary wodnej metodą PEM jako efektywnej i technicznie najprostszej metody, SOFC jako efektywnego procesu termoelektrycznego w skali przemysłowej i termochemicznego rozkładu wody jako alternatywy dla metod wykorzystujących zjawisko elektrolizy.

18

Complex exergy analysis of an integrated oxy-fuel combustion power plant with CO2 transport and storage

Gładysz P., Ziębik A.

Journal of Power Technologies

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2015

|

Vol. 95, spec.

23--31

EN

The paper presents a method of the complex system exergy analysis, as well as an example of application in the case of an integrated oxy-fuel combustion (OFC) power plant with CO2 transport and storage. Complex exergy analysis consist of (a) local exergy losses, (b) cumulative exergy consumption, (c) cumulative exergy losses and (d) cumulative degree of thermodynamic perfection. The algorithms of the complex system exergy analysis are based on "input-output method" of the direct energy and material consumption. In the structure of the balance we distinguished main products (e.g. electricity), by-products (e.g. nitrogen) and external supplies (e.g. hard coal). The considered system (OFC power plant with CO2 transport and storage infrastructure) consists of seven interconnected modules, viz. boiler island, steam cycle, air separation unit, cooling water and water treatment module, flue gas quality control module, CO2 processing unit and CO2 transport and storage module, among which there also exist feedback relations.

19

Thermal analysis of heat and power plant with high temperature reactor and intermediate steam cycle

Fic A., Składzień J., Gabriel M.

Archives of Thermodynamics

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2015

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Vol. 36, no. 1

3--18

EN

Thermal analysis of a heat and power plant with a high temperature gas cooled nuclear reactor is presented. The main aim of the considered system is to supply a technological process with the heat at suitably high temperature level. The considered unit is also used to produce electricity. The high temperature helium cooled nuclear reactor is the primary heat source in the system, which consists of: the reactor cooling cycle, the steam cycle and the gas heat pump cycle. Helium used as a carrier in the first cycle (classic Brayton cycle), which includes the reactor, delivers heat in a steam generator to produce superheated steam with required parameters of the intermediate cycle. The intermediate cycle is provided to transport energy from the reactor installation to the process installation requiring a high temperature heat. The distance between reactor and the process installation is assumed short and negligable, or alternatively equal to 1 km in the analysis. The system is also equipped with a high temperature argon heat pump to obtain the temperature level of a heat carrier required by a high temperature process. Thus, the steam of the intermediate cycle supplies a lower heat exchanger of the heat pump, a process heat exchanger at the medium temperature level and a classical steam turbine system (Rankine cycle). The main purpose of the research was to evaluate the effectiveness of the system considered and to assess whether such a three cycle cogeneration system is reasonable. Multivariant calculations have been carried out employing the developed mathematical model. The results have been presented in a form of the energy efficiency and exergy efficiency of the system as a function of the temperature drop in the high temperature process heat exchanger and the reactor pressure.

20

Exergy analysis of the Szewalski cycle with a waste heat recovery system

Kowalczyk T., Ziółkowski P., Badur J.

Archives of Thermodynamics

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2015

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Vol. 36, no. 3

25--48

EN

The conversion of a waste heat energy to electricity is now becoming one of the key points to improve the energy efficiency in a process engineering. However, large losses of a low-temperature thermal energy are also present in power engineering. One of such sources of waste heat in power plants are exhaust gases at the outlet of boilers. Through usage of a waste heat regeneration system it is possible to attain a heat rate of approximately 200 MWth, under about 90°C, for a supercritical power block of 900 MWel fuelled by a lignite. In the article, we propose to use the waste heat to improve thermal efficiency of the Szewalski binary vapour cycle. The Szewalski binary vapour cycle provides steam as the working fluid in a high temperature part of the cycle, while another fluid – organic working fluid – as the working substance substituting conventional steam over the temperature range represented by the low pressure steam expansion. In order to define in detail the efficiency of energy conversion at various stages of the proposed cycle the exergy analysis was performed. The steam cycle for reference conditions, the Szewalski binary vapour cycle as well as the Szewalski hierarchic vapour cycle cooperating with a system of waste heat recovery have been comprised.