Aus der Einleitung: "Durch die Verwendung von Kraft-Wärme-Kopplung (KWK) kann sowohl die erzeugte elektrische als auch die anfallende thermische Energie genutzt und somit der Nutzungsgrad der eingesetzten Primärenergie deutlich gesteigert werden. Dieses Konzept wird sowohl in Blockheizkraftwerken (BHKW) wie auch in Range Extendern (RE) verwendet (Ferrari et al. 2012). Die bisher geringe Reichweite von Elektrofahrzeugen wird durch die zusätzlich vom RE bereitgestellte elektrische Energie erweitert. ..."

Master of Science / Department of Architectural Engineering and Construction Science / Fred Hasler / Data center space and power densities are increasing as today’s society becomes more dependent on computer systems for processing and storing data. Most existing data centers were designed with a power density between 40 and 70 watts per square foot (W/SF), while new facilities require up to 200W/SF. Because increased power loads, and consequently cooling loads, are unable to be met in existing facilities, new data centers need to be built. Building new data centers gives owners the opportunity to explore more energy efficient options in order to reduce costs. Fuel cells are such an option, opposed to the typical electric grid connection with UPS and generator for backup power. Fuel cells are able to supply primary power with backup power provided by generators and/or the electric grid. Secondary power could also be supplied to servers from rack mounted fuel cells. Another application that can benefit from fuel cells is the HVAC system. Steam or high-temperature water generated from the fuel cell can serve absorption chillers for a combined heat and power (CHP) system. Using the waste heat for a CHP system, the efficiency of a fuel cell system can reach up to 90%. Supplying power alone, a fuel cell is between 35 and 60% efficient. Data centers are an ideal candidate for a CHP application since they have constant power and cooling loads. Fuel cells are a relatively new technology to be applied to commercial buildings. They offer a number of advantages, such as low emissions, quiet operation, and high reliability. The drawbacks of a fuel cell system include high initial cost, limited lifetime of the fuel cell stacks, and a relatively unknown failure mode. Advances in engineering and materials used, as well as higher production levels, need to occur for prices to decrease. However, there are several incentive programs that can decrease the initial investment. With a prediction that nearly 75% of all 10 year old data centers will need to be replaced, it is recommended that electrical and HVAC designer engineers become knowledgeable about fuel cells and how they can be applied to these high demand facilities.

Achieving the reductions in carbon dioxide emissions which are necessary will require improvements in the way in which domestic space heating is supplied. Air Source Heat Pumps and micro-Combined Heat and Power units both have the potential to reduce emissions while using primary energy resources more efficiently. The performance which these technologies can achieve is fundamental to fulfilling this potential and yet it is still subject to some uncertainty. This thesis analyses the performance of Air Source Heat Pumps and micro-Combined Heat and Power units in terms of their energy and exergy requirements and in terms of the carbon dioxide emissions associated with their operation. A review of the literature identified that it was appropriate to develop a novel modelling approach. Models of many components currently exist and these are adopted and extended wherever possible within this modelling approach. However, it is the unique way in which this research combines these models and adds additional components which delivers performance data relating to a wider range of conditions at a greater level of detail than that which was previously available. The model which was developed can dynamically simulate the heating and power demands in many dwellings simultaneously, facilitating meaningful study of effects which are dependent upon the sum of their power flows. Consideration of the effect of operating conditions includes permutations of climate, control systems (including those which engage with demand side management), grid generation mixes and building properties. Efficient Air Source Heat Pumps units have the potential to make energy and carbon emissions savings at present but their performance is sensitive to the conditions studied. In particular, appropriate control of the units can yield energy savings of around 25%. Additionally, the carbon emissions intensity of the grid is an important consideration which is explored in depth. Currently, energy requirements and carbon emissions can be reduced by the use of micro-Combined Heat and Power units. Their potential to further reduce carbon emissions diminishes if the grid is predominantly decarbonised but units with high electrical efficiencies can still save energy. The effect of the control approach which is adopted is also significant and has different effects on fuel-cell based units compared to combustion-based units. The key contribution of this work is the analysis of performance data for a selection of units operating under a range of conditions, calculated with a consistent, accurate methodology. Comparison is made between the technologies and between the effects of different operating conditions. A second significant contribution of this work is the development of the model which was used to generate the performance results. These advances allow more detailed comparative analysis of performance data in a wider range of conditions than previously possible.

As in all other electrical equipments it is essential to estimate the temperature distribution in transformer components in the design stage and during the operation since temperatures above thermal limits of these components might seriously damage them. Thermal models are used to predict this vital information prior to actual operations. In this study, a three dimensional model based on the Finite Element Method (FEM) is proposed to estimate the temperature distribution in the three phase, SF6 gas insulated-cooled power transformer. This model can predict the temperature distribution at the specific discredited locations in the transformer successfully.

As in all other electrical equipments it is essential to estimate the temperature distribution in transformer components in the design stage and during the operation since temperatures above thermal limits of these components might seriously damage them. Thermal models are used to predict this vital information prior to actual operations. In this study, a three dimensional model based on the Finite Element Method (FEM) is proposed to estimate the temperature distribution in the three phase, SF6 gas insulated-cooled power transformer. This model can predict the temperature distribution at the specific discredited locations in the transformer successfully.

Global warming, in combination with increasing energy demand and higher energy prices, makes it necessary to change the energy use. To secure the energy supply and to develop sustainable societies, construction of energy-efficient systems is at the same time most vital. The aim of this thesis is therefore to identify how a local energy company, producing district heating (DH), district cooling (DC) and electricity in combined heat and power (CHP) plants, can contribute to resource-efficient energy systems and cost-effective reductions of global carbon dioxide (CO2) emissions, along with its customers. Analyses have been performed on how a local energy company can optimise their DH and DC production and what supply-side and demand-side measures can lead to energy-efficient systems in combination with economic and climate change benefits. The energy company in focus is located in Linköping, Sweden. Optimisation models, such as MODEST and reMIND, have been used for analysing the energy systems. Scenario and sensitivity analyses have also been performed for evaluation of the robustness of the energy systems studied. For all analyses a European energy system perspective was applied, where a fully deregulated European electricity market with no bottlenecks or other system failures was assumed. In this thesis it is concluded that of the DH-supply technologies studied, the biomass gasification applications and the natural gas combined cycle (NGCC) CHP are the technologies with the largest global CO2 reduction potential, while the biomass-fuelled plant that only produces heat is the investment with the smallest global CO2 reduction and savings potential. However, the global CO2 reduction potential for the biomass integrated gasification combined cycle (BIGCC) CHP and NGCC CHP, the two technologies with highest electricity efficiencies, is highly dependent on the assumptions made about marginal European electricity production. Regarding the effect on the DH system cost the gasification application integrated with production of renewable biofuels (SNG) for the transport sector is the investment option with the largest savings potential for lower electricity prices, while with increasing electricity prices the BIGCC and NGCC CHP plants are the most cost-effective investment options. The economic outcome for biomass gasification applications is, however, dependent on the level of policy instruments for biofuels and renewable electricity. Moreover, it was shown that the tradable green certificates for renewable electricity can, when applied to DH systems, contribute to investments that will not fully utilise the DH systems’ potential for global CO2 emissions reductions. Also illustrated is that conversion of industrial processes, utilising electricity and fossil fuels, to DH and DC can contribute to energy savings. Since DH is mainly used for space heating, the heat demand for DH systems is strongly outdoor temperature-dependent. By converting industrial processes, where the heat demand is often dependent on process hours instead of outdoor temperature, the heat loads in DH systems can become more evenly distributed over the year, with increased base-load heat demand and increased electricity generation in CHP plants as an outcome. This extra electricity production, in combination with the freed electricity when converting electricity-using processes to DH, can replace marginal electricity production in the European electricity market, resulting in reduced global CO2 emissions. Demonstrated in this thesis is that the local energy company, along with its customers, can contribute to reaching the European Union’s targets of reducing energy use and decreasing CO2 emissions. This can be achieved in a manner that is cost-effective to both the local energy company and the customers. / Den globala uppvärmningen i kombination med ett ökat energibehov och stigande energipriser gör det nödvändigt att förändra energianvändningen. Energieffektiva system är samtidigt en förutsättning för att kunna säkra energitillförseln och utveckla hållbara samhällen. Fjärrvärme har en viktig roll att fylla i den här omställningen. I fjärrvärmesystemen kan värmeresurser som annars kan vara svåra att nyttiggöras, som till exempel spillvärme och förbränning av avfall tas tillvara. Fjärrvärme kan även bidra till elproduktion i kraftvärmeverk där totalverkningsgraden är högre än vid separat el- respektive värmeproduktion. En omställning av energisystemet till en ökad användning av fjärrvärme och minskad användning av el genom effektiviseringar och konverteringar från olja och el till fjärrvärme kan bidra till att skapa energieffektiva system. Syftet med den här avhandlingen är att identifiera hur ett lokalt energibolag som producerar fjärrvärme, fjärrkyla och el i kraftvärmeverk kan bidra till att skapa energieffektiva system och kostnadseffektiva globala koldioxidreduktioner tillsammans med sina kunder. Det energibolag som framförallt har studerats i den här avhandlingen är Tekniska Verken i Linköping AB. För att optimera energibolagets fjärrvärme- och fjärrkylaproduktion har energisystemanalyser genomförts, där både åtgärder på tillförsel- och användarsidan har studerats. Genom att se energiförsörjningen ur ett systemperspektiv kan man undvika att ekonomiska och miljömässiga vinster vid en anläggning ersätts av förluster någon annanstans. Optimeringsmodeller, som MODEST och reMIND, har använts för energisystemanalyserna där även scenarier och känslighetsanalyser har inkluderats. För alla energisystemanalyser har ett europeiskt energisystemperspektiv använts där en totalt avreglerad europeisk elmarknad utan flaskhalsar eller andra systemfel antagits. Slutsatser från analyserna är att det lokala energibolaget kan bidra till kostnadseffektiva globala koldioxidreduktioner genom ett effektivt nyttjande av bränslen i kraftvärmeanläggningar och i bioraffinaderier. Speciellt kraftvärmeanläggningar med hög elverkningsgrad, som t.ex. biomasseförgasning- och naturgaskombianläggningar, har en betydande global koldioxidreduktionspotential. Även biomasseförgasningsanläggningar som är integrerade med produktion av förnybara drivmedel för transportsektorn har visat sig kostnadseffektiva med stor potential att reducera de globala koldioxidutsläppen. Styrmedel har dock en stor påverkan på det ekonomiska utfallet för förgasningsanläggningarna. Dessutom har studierna visat att energibesparingar kan åstadkommas genom att konvertera el och fossilbränsledrivna industriella processer till fjärrvärme och fjärrkyla. Eftersom fjärrvärme framförallt används för lokaluppvärmning är värmelasten i fjärrvärmesystem säsongsbetonad. Genom att konvertera industriella processer som inte är utetemperaturberoende till fjärrvärme kan fjärrvärmelasten bli mindre säsongsbetonad och mer jämt fördelad över året. En jämt fördelad värmelast är fördelaktig för driften av fjärrvärmeanläggningar och kan bidra till mer elproduktion i kraftvärmeanläggningar. Den extra elproduktionen, tillsammans med den el som blivit tillgänglig efter konvertering av eldrivna processer till fjärrvärme, kan ersätta europeisk marginalelsproduktion vilket kan reducera de globala koldioxidutsläppen. Det som har framkommit av dessa studier är att det lokala energibolaget, tillsammans med sina kunder, kan bidra till att uppfylla de mål den Europeiska Unionen har angående reduktionen av energianvändningen och koldioxidutsläppen. Dessutom kan detta ske på ett kostnadseffektivt sätt för både energibolaget och dess kunder.

The objective of the study is to analyse the conditions for connection of residential buildings in heat sparse areas to district heating systems in order to increase electricity production in municipal combined heat and power plants. The European electricity market has been assumed to be fully deregulated. The relation between connection of heat sparse areas, increased electricity and heat production as well as electricity prices, fuel prices and emissions rights is investigated. The results of the study show that there is potential to expand the district heating market to areas with lower heat concentrations in the cities of Gavle, Sandviken and Borlange in Sweden, with both economic and environmental benefits. The expansion provides a substantial heat demand of approximately 181 GWh/year, which results in an electricity power production of approximately 43 GWh/year. Since the detached and stand-alone houses in the studied heat sparse areas have been heated either by oil boiler or by direct electricity, connection to district heating also provides a substantial reduction in emissions of CO2. The largest reductions in CO2 emissions are found to be 211 ktonnes/year assuming coal-fired condensing power as marginal electricity production. Connection of heat sparse areas to district heating decrease the system costs and provide a profitability by approximately 22 million EURO/year for the studied municipalities if the price of electricity is at a European level, i.e. 110 EURO/MWh. Sensitivity analysis shows, among other things, that a strong relation exists between the price of electricity and the profitability of connecting heat sparse areas to district heating systems. / Original Publication:Shahnaz Amiri and Bahram Moshfegh, Possibilities and consequences of deregulation of the European electricity market for connection of heat sparse areas to district heating systems, 2010, Applied Energy, (87), 7, 2401-2410.http://dx.doi.org/10.1016/j.apenergy.2010.02.002Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com/

The goal of this work is to develop a conceptual framework and computational tools for the optimization of utility systems in the process industries. The emphasis is devoted to the development of systematic design techniques aimed at identifying modifications to the process and the associated utility-systems to jointly optimize the process and the utility system. The following contributions describe the specific results of this work: • Development of shortcut methods for modeling and optimizing steam systems and basic thermodynamic cycles with the objective of using these methods in the optimization of combined heat and power. To enable efficient mathematical programming formulations, simple yet accurate correlations have been developed for the thermodynamic properties of steam in the utility system. • Optimization of multi-level steam system for combined process requirements and power cogeneration. A general procedure is developed to determine rigorous cogeneration targets and the optimal configuration of the system with the associated design and operating variables. • Graph theory methods are also used to optimize the pipeline layout in the plant for the distributing the utilities. • Finally, because of the nonconvex nature of much of the developed optimization formulations, a global optimization method has also been suggested by using interval analysis and simulated annealing. The techniques proposed in this work are compared to previous works and their applicabilities are presented in case studies. These techniques outperform previously suggested ones in terms of the accuracy, computational efficiency and/or optimality.

Die energetische Nutzung von Biomasse ist ein wichtiger Beitrag zur Reduktion der CO2- Emissionen. Wärmeerzeugung und gekoppelte Wärme- und Stromerzeugung sind dafür die effektivsten Technologien. Dabei spielt die Erzeugung und Nutzung von Brenngasen aus Biomasse eine große Rolle. Die inzwischen weit verbreitete biologische Gaserzeugung produziert sogenanntes Biogas. Die Forschung konzentriert sich hierbei derzeit unter anderem auf Grundlagen für die Optimierung der Betriebsführung. Aber auch mit thermochemischen Verfahren („Vergasung“) wird Brenngas erzeugt. Einer der Forschungsschwerpunkte dabei ist die angemessene Reinigung des Gases von Teeren und Stäuben. Die Brenngase können dann in herkömmlichen, wenn auch angepassten Verbrennungsmotoren im Zusammenhang mit Generatoren zur Stromerzeugung genutzt werden oder nach einem weiteren Umwandlungsschritt als Erdgasersatz Verwendung finden. / The utilisation of biomass as an energy supply is an important contribution to the reduction of greenhouse emissions. Heat supplies and combined heat and power generation are the most effective technologies from an energetic point of view. In most cases, conversion of solid biomass to a gaseous fuel is an important technological step. Gas generation by biological processes (“biogas”) has been increasing rapidly in recent times. Research in this field is concentrated on improving and automating process operation. Gaseous fuel from biomass can also be generated by thermochemical processes (“gasification”). Research is here focussed on the cleaning of tars and dusts from the gas, for example. The gaseous fuels can then be used in adapted internal combustion engines in combination with electricity generators.

It is of great importance to acquire methods that has a sustainable solution for treatment and disposal of municipal solid waste (MSW). The volumes are constantly increasing and improper waste management, like open dumping and landfilling, causes environmental impacts such as groundwater contamination and greenhouse gas emissions. The rationalization of developing a sustainable solution implies in an improved way of utilizing waste resources as an energy source with highest possible efficiency. MSW incineration is by far the best available way to dispose the waste. One drawback of conventional MSW incineration plants is that when the energy recovery occurs in the steam power cycle configuration, the reachable efficiency is limited due to steam parameters. The corrosive problem limits the temperature of the superheated steam from the boiler which lowers the efficiency of the system. A suitable and relatively cheap option for improving the efficiency of the steam power cycle is the implementation of a hybrid dual-fuel cycle. This paper aims to assess the integration of an MSW incineration with a high quality fuel conversion device, in this case natural gas (NG) combustion cycle, in a hybrid cycle. The aforementioned hybrid dual-fuel configuration combines a gas turbine topping cycle (TC) and a steam turbine bottoming cycle (BC). The TC utilizes the high quality fuel NG, while the BC uses the lower quality fuel, MSW, and reaches a total power output of 50 MW.  Using a high-quality fuel in cogeneration can prove to be beneficial for improving and enhancing the overall plant profitability and efficiency while eliminating the corrosion problems with conventional MSW firing. The need for few interconnections between the different subunits in a parallel-fueled system allows for a wider range of operation modes and leaves room for service modes of the subunit. The hybrid dual-fuel cycle will be assessed for optimal cycle configuration and evaluated to how it compares to the sum of two separate single-fuel plants with optimal cycle configurations. Investigation of such aspects is a very important issue in order to be able to fully promote an implementation of hybrid combined cycle. The work presented herein also concentrates on investigating scenarios that include a full-load and part-load analysis in both condensing and combined heat and power (CHP) mode of operation. Through simulations and evaluation of obtained data, the results strengthens the fact that the electrical efficiency of hybrid configurations increases at least with 2% in condensing mode and 1,5% in CHP mode, comparing it to the sum of two separate single-fuel units of similar scale. The simulations show increased electrical efficiencies when running the BC in part-load and the TC in full load, with a higher NG to MSW ratio. The results also indicated that it is possible to extract more power output from the cycle by operating in CHP mode, due to more energy being utilized from the input fuel.