Globally, there are vast amounts of low-grade heat sources from industrial waste and renewables that can be converted into electricity through advanced thermodynamic power cycles and appropriate working fluids. In this thesis, experimental research was conducted to investigate the performance of a small-scale Organic Rankine Cycle (ORC) system under different operating conditions. The experimental setup consisted of typical ORC system components, such as a turboexpander with a high speed generator, a scroll expander, a finned-tube condenser, an ORC pump, a plate evaporator and a shell and tube evaporator. R245fa was selected as the working fluid, on account of its appropriate thermophysical properties for the ORC system and its low ozone depletion potential (ODP). The test rig was fully instrumented and extensive experiments carried out to examine the influences of several important parameters, including heat source temperature, ORC pump speed, heat sink flow velocity, different evaporators and with or without a recuperator on overall R245fa ORC performances. In addition, in terms of the working fluid’s environmental impact, temperature match of the cycle heat processes and system compactness, CO2 transcritical power cycles (T-CO2) were deemed more applicable for converting low-grade heat to power. However, the system thermal efficiency of T-CO2 requires further improvement. Subsequently, a test rig of a small-scale power generation system with T-CO2 power cycles was developed with essential components connected; these included a plate CO2 supercritical heater, a CO2 transcritical turbine, a plate recuperator, an air-cooled finned-tube CO2 condenser and a CO2 liquid pump. Various preliminary test results from the system measurements are demonstrated in this thesis. At the end, a theoretical study was conducted to investigate and compare the performance of T-CO2 and R245fa ORCs using low-grade thermal energy to produce useful shaft or electrical power. The thermodynamic models of both cycles were developed and applied to calculate and compare the cycle thermal and exergy efficiencies at different operating conditions and control strategies. In this thesis, the main results showed that the thermal efficiency of the tested ORC system could be improved with an increased heat source temperature in the system with or without recuperator. When the heat source temperature increased from 145 oC to 155 oC for the system without recuperator, the percentage increase rates of turbine power output and system thermal efficiency were 13.6% and 14% respectively while when the temperature increased from 154 oC to 166 oC for the system with recuperator, the percentage increase rates were 31.2% and 61.97% respectively. In addition, the ORC with recuperator required a relative higher heat source temperature, which is comparable to a system without recuperator. On the other hand, at constant heat source temperatures, the working fluid pump speed could be optimised to maximise system thermal efficiency for ORC both with and without recuperator. The pressure ratio is a key factor impacting the efficiencies and power generation of the turbine and scroll expander. Maximum electrical power outputs of 1556.24W and 750W of the scroll expander and turbine were observed at pressure ratio points of 3.3 and 2.57 respectively. For the T-CO2 system, the main results showing that the CO2 mass flow rate could be directly controlled by varying the CO2 liquid pump speeds. The CO2 pressures at the turbine inlet and outlet and turbine power generation all increased with higher CO2 mass flow rates. When CO2 mass flow rate increased from 0.2 kg/s to 0.26kg/s, the maximum percentage increase rates of measured turbine power generation was 116.9%. However, the heat source flow rate was found to have almost negligible impact on system performance. When the thermal oil flow rate increased from 0.364kg/s to 0.463kg/s, the maximum percentage increase rate of measured turbine power generation was only 14.8%. For the thermodynamic analysis, with the same operating conditions and heat transfer assumptions, the thermal and exergy efficiencies of R245fa ORCs are both slightly higher than those of T-CO2. However, the efficiencies of both cycles can be enhanced by installing a recuperator at under specific operating conditions. The experiment and simulation results can thus inform further design and operation optimisations of both the systems and their components.

Le but principal de ce projet doctoral est de déterminer le potentiel d'amélioration de l'efficacité énergétique du système de captage de carbone dans les stations thermiques de production d'électricité, par l'intégration optimale des éjecteurs monophasiques. Il s'agit du système de captage postcombustion du dioxyde de carbone (CO2) par absorption/désorption utilisant la monoéthanolamine (MEA). Les éjecteurs intégrés utilisent des rejets thermiques de 100 °C qu'on retrouve dans les stations thermiques de production d'électricité. La revalorisation de ces rejets permet la substitution partielle de vapeur de turbine à coût élevé, qui serait autrement prise de la centrale thermique. Le deuxième objectif de la thèse est d'évaluer expérimentalement la performance d'un éjecteur à vapeur où le fluide secondaire de l'éjecteur est un mélange de vapeur d'eau et d'un gaz non-condensable, dans le cas présent, le CO2. Deux tuyères d'éjecteur à vapeur, d'un diamètre de 4.60 mm et 4.23 mm, ont été évaluées sur une plage de niveaux de CO2 dans le fluide secondaire, jusqu'à environ 40% en masse. La pression primaire était maintenue à 450 kPa avec une surchauffe à 10 °C et la pression secondaire était de 70 kPa. On a constaté que la pression critique ne changeait pas à mesure que la fraction massique de CO2 dans le fluide secondaire augmentait. Cependant, le rapport d'entraînement a augmenté de façon linéaire sur la plage expérimentale. Une amélioration de 23% du rapport d'entraînement par rapport à la vapeur pure a été observée lorsque le fluide secondaire contient 42% de CO2 par masse. Ce comportement contraste nettement avec le comportement observé expérimentalement d'un éjecteur à vapeur pure, où une augmentation du rapport d'entraînement se produit au détriment d'une diminution de la pression critique. Trois articles détaillés ont été publiés sur divers scénarios d'intégration d'un éjecteur à vapeur dans un procédé de captage d'absorption/désorption. Le solvant de référence était de 20% en masse de monoéthanolamine (MEA). Trois configurations principales ont été étudiées, selon le choix du fluide utilisé pour produire la vapeur secondaire : éjecteur sur condensat, éjecteur sur pauvre ou éjecteur sur riche. La première publication de revue scientifique a porté sur le procédé de désorption et a présenté une méthode de raccourci basée sur les propriétés du mélange CO2-MEA-H2O à l'équilibre. Les simulations ont révélé des réductions dans la quantité requise d'énergie de haute qualité, de 10 à 25%. Un simulateur de procédé commercial, Aspen Plus, a été utilisé pour les deux autres publications. Dans la deuxième publication de revue scientifique, le module cinétique rate-based a été utilisé, au lieu du module d'équilibre, pour la modélisation de l'absorbeur et du désorbeur, permettant des évaluations énergétiques plus près des valeurs qu'on retrouve dans la littérature courante. Une étude a été réalisée pour comparer un scénario de préchauffage de la vapeur primaire par des rejets thermiques externes avec un scénario d'intégration de la chaleur interne. Cette deuxième publication a montré des économies d'énergie de haute qualité, de 10 à 14%, les scénarios avantageux ayant été «éjecteur sur condensat» et «éjecteur sur pauvre». / Abstract : The main goal of the doctoral project is to determine to what extent the optimal integration of single-phase ejectors might reduce the large amount of energy required to capture carbon dioxide from electric power generation facilities. More specifically, the objective is to determine if ejectors can be advantageously integrated into a post-combustion absorption/desorption carbon dioxide (CO2) capture process using monoethanolamine (MEA). The integrated ejectors will use waste heat of 100 °C from the electric power plant. The upgraded waste heat can partially replace valuable turbine steam that would otherwise be taken from the power plant. The second objective of the thesis is to experimentally evaluate the performance of a steam ejector where the ejector secondary fluid is a mixture of steam and a non-condensable gas, in this case CO2. Two steam ejector nozzles, of 4.60 mm and 4.23 mm diameter, were evaluated over a range of secondary fluid CO2 levels, up to 42% by mass. The primary pressure was maintained at 450 kPa with 10 °C superheat and the secondary pressure was 70 kPa. It was found that the critical exit pressure did not change as the mass fraction of CO2 in the secondary fluid increased. The entrainment ratio, however, increased approximately linearly over the experimental range. An improvement of 23% in the entrainment ratio, as compared with pure steam, was found when the secondary fluid contains 42% CO2 by mass. This behaviour is in sharp contrast to the experimentally observed behaviour of a pure steam ejector, where an increase in entrainment ratio comes at the expense of a decrease in the ejector exit critical pressure. Three published papers investigated various scenarios for the integration of a steam injector into an absorption/desorption post-combustion capture process. The reference solvent was 20% weight monoethanolamine (MEA). Three principal configurations were studied, according to the choice for the liquid flow used to produce the ejector secondary steam: ejector on condensate, ejector on lean or ejector on rich. The first journal publication focused on the desorption process and presented a shortcut method based on CO2-MEA-H2O equilibrium vapour liquid data. The simulations revealed reductions in the required amount of valuable energy from 10 to 25%. A commercial process simulator, Aspen Plus, was used for two other publications. In the second journal publication, the kinetic rate-based module was employed to model the absorber and desorber, providing energy evaluations closer to values in the open literature. A study was included comparing preheating the primary steam with waste heat or by heat integration. The rate-based simulation found valuable energy savings of 10 to 14%, with the "ejector on condensate" and "ejector on lean" again being the advantageous scenarios.

Industrial waste heat has been around for hundreds of years and has long been assumed to be only a by-product of industrial activities. The purpose of the study was to contribute knowledge about the potential of waste heat energy as a resource from an economic and environmental perspective and to identify what important problems can be found in decision-making regarding the implementation of waste heat recovery systems. The study was conducted in the form of a case study with the engineering company Epiroc Drilling Tools AB in Fagersta as a study object. The waste heat survey showed that optimal recovery potential existed in the heat treatment furnaces' flares in the form of flue gases. The total waste heat energy available to be recycled in all 24 industrial furnaces of the workshop was estimated at between 1.63 to 1.92 GWh per year. The engineering company had a district heating demand of about 2.3 GWh in 2018. Investment in the waste heat recovery system would mean that the company can cover up to 83% of the plant's district heating needs. The engineering company aimed to, over a three-year period, among other things, reduce its total energy use by 20% and a recovery of the available waste heat energy could contribute 4.2 to 5.0% of the company's energy efficiency projects. A recovery of the waste heat was estimated to result in capital savings between SEK 900,000 to SEK 1,100,000 excluding VAT annually. The basic investment cost of the recycling system was estimated SEK 3,500,000 with an operating cost of SEK 220,000. The payback time was estimated to be about 4 years for the engineering company to fully repay the investment cost of the recycling system. Primary and secondary data collection resulted in answering what problems and obstacles could arise in decision making regarding investment and implementation of waste heat recovery systems. / Industriell spillvärme har funnits sedan flera hundra år tillbaka och har länge bara antagits vara en biprodukt från industriella aktiviteter. Syftet med studien var att bidra med kunskap om spillvärmeenergins potential som resurs ur ett ekonomiskt och miljömässigt perspektiv samt identifiera vilken betydelsefull problematik som kan finnas vid beslutsfattande om implementering av spillvärmeåtervinningssystem. Studien genomfördes i form av en fallstudie med verkstadsföretaget Epiroc Drilling Tools AB i Fagersta som studieobjekt. Spillvärmekartläggningen visade att optimal återvinningspotential fanns vid värmebehandlingsugnarnas avfacklingar i form av rökgaser. Den totala spillvärmeenergin som fanns tillgänglig att återvinna i verkstadens alla 24 industriella ugnar, uppskattades till mellan 1,63 till 1,92 GWh per år. Verkstadsföretaget hade 2018 ett fjärrvärmebehov på ca 2,3 GWh. Investering i spillvärmeåtervinningssystemet skulle innebära att företaget kan täcka upp till 83% anläggningens fjärrvärmebehov. Verkstadsföretaget hade som mål att under en treårsperiod, bland annat sänka sin totala energianvändning med 20% och en återvinning av den tillgängliga spillvärmeenergin skulle kunna bidra med 4,2 till 5,0% av företagets energieffektiveringsprojekt. En återvinning av spillvärmen uppskattades resultera i kapitala besparingar mellan 900 000 till 1 100 000 SEK exklusive moms årligen. Grundinvesteringskostnaden för återvinningssystemet uppskattades till 3 500 000 SEK med en driftkostnad på 220 000 SEK. Payback-tiden uppskattades till ca 4 år för verkstadsföretaget att helt återbetala investeringskostnaden för återvinningssystemet. Primär- och sekundärdatainsamling resulterade i att besvara vilken problematik och vilka hinder som kunde uppstå vid beslutsfattande gällande investering och implementering av spillvärmeåtervinningssystem.

Today many processes generate a lot of waste heat, for example industries or cars. One way to make this thermal energy useful is to transform it into electrical energy with a thermoelectric generator (TEG) or thermoelectric cooler (TEC). This technology is not used in any large scale today, but a lot of research is being done on the subject. The technology is based on the Seebeck effect and uses a temperature difference between two sides of an element to generate an electrical current. The reason that the research has gained more attention in recent years is because of the increasing electricity prices and the diminishing natural resources. Other benefits are that they run quietly and do not demand much maintenance.Another area where this technology could be useful is in off-grid cabins where it is easy to generate a lot of thermal energy by burning wood, but electrical energy is in high demand.In this thesis two different types of TEGs and one type of TEC are tested to investigate how much power they generate at different temperature differences, how well they meet the specified values in their respective data sheet and what their power per euro value is. For this, an experimental setup was made with:- An induction plate to increase the temperature on the hot side.- A CPU-fan, to reduce the temperature on the cold side.- Two temperature sensors (one for measuring the hot temperature and one for the cold one).- An electric circuit featuring a voltmeter, an amperemeter and an adjustable resistor (rheostat).The results show that, for this experiment the highest received power (6,38 W) comes from the medium-priced element but the highest power per euro comes from the lowest priced element (1,16 W/€). A quality problem for the lowest priced element was that parts of the solder melted when the temperature exceeded 225 °C. Another problem was that the induction plate was unable to provide enough heat for the most expensive of the elements to reach the temperature for which the retailer supplies their measured data.

The main goal of this Master's thesis was to design heat recovery steam boiler for cogenera-tion unit of a biogas plant while flue gas was flowing from an engine exhaust. Its temperature and required pressure of a steam were assigned. The thesis contains thermal, aerodynamic, hyd-raulic calculations and verification of wall thicknesses for pressure parts of the boiler. Follow-up results of these calculations served for making of projection drawings as well as equipment needed for reliable boiler operation.

This diploma thesis introduces the reader to the design of the new cooling circuit and its modernization. Part of this is the calculation of the heat exchanger and the design of other parts, such as pumps or cooling towers. It also deals with the possibility of using waste heat for specific conditions.

The purpose of the thesis is to draw up a model of the energy and material balance using technical and technological analysis of the current state of production of waste heat in the process of distillation. Using these results, subsequently evaluate the energy potential of individual streams and propose optimal energy savings using waste heat. Emphasis is placed on the modelling of the process and the various proposed savings options. The result is also an evaluation of the potential of the proposed savings based on the results of the calculation.

This master’s thesis deals with the design of heat recovery system from melting furnace waste gases. The first part is devoted to a brief description of heat exchangers, with the special importance being placed on the shell-and-tube heat exchanger. The second part contains a calculation of stoichiometric combustion, design of geometrical dimensions, calculation of pressure drops and power. At the end of the thesis there are various possibilities of utilization of the obtained waste heat and their basic economic assessment.

This thesis deals with the possibilities of using waste heat for power generation with a focusing on biogas plants (BGS). The produced biogas is mainly used for combustion in cogeneration units with internal combustion piston engines. The first part this paper describes the biogas plants. The division of BGS and the biogas processing is mentioned there. Another part is focused on the combined production of electricity and heat. The principles and description various types of cogeneration technologies are presented here. The following are specific options for waste heat utilization for biogas plants. The last section contains proposals to increase electricity production by the BGS with the steam engine and economic evaluation of these proposals is made.

This master’s thesis deals with the issue of design heat recovery steam generator. In the first part is realized calculation of stoichiometry and further the thermal balance of the boiler. The boiler was divided on the basis of thermal analysis in two heating surfaces that have been designed separately. The thesis also includes structural design and drawings of evaporator, economizer and their compilation.