Energy production in power plants comes with both high costs and turnover whereas variations in the production strategy—that is, which boilers, coolers, or generators that should be running—have big impact on the economic result. This is especially true for a combined heat and power (CHP) plant where the production of district heating and electricity is linked, thus allowing for a higher flexibility in the production strategy and potential of increasing the revenue. Previous research states that thermo-economic optimization can have a great impact on economic result of power plants, but every power plant is operating under a unique set of conditions depending on its location, operating market, load demand, construction, surrounding, and the like, and comparable studies on CHP plants in Sweden are very few. This study aims to fill this research gap by evaluating savings potential of a CHP plant in Lidköping, Sweden by utilizing thermo-economic optimization with the approach of combining actual historical data from the power plant with mass-flow equations and constraints to construct a mathematical MODEST model that is optimized by linear programming. The result demonstrates a clear theoretical potential to improve earnings and the conclusion that the studied CHP would benefit by implementing optimization procedures or software to schedule production. The result was also comparable to previous research but varied over time, which highlights how unique conditions may impact the result.

One of the great challenges facing society is to convert theglobal energy system to a sustainable process. Currently, 80%of the world´s energy is supplied through the combustionof fossil fuels. Not only are the fossil resources limited, theutilisation also increases the level of greenhouse gases in theatmosphere. The convertion to a sustainable energy system isproblematic since the technology needed to exploit mostnon-fossil energy sources is not yet fully developed, e.g.solar energy. Biofuel is an available renewable energy sourcewhich is already widely used in many countries. If an effectiveswitch-over from fossil fuels to biofuels is to be realised,biofuels must be viewed as a limited resource. Consequently, itis important that the handling, upgrading and utilisationprocesses involving biofuels are efficient so that itspotential can be fully exploited. This thesis considers efficient biofuel utilisation andupgrading within the sawmill industry. The goal has been toanalyse not only the technical opportunities for energy savingsin the sawmill industry, but also to analyse the costeffectiveness and environmental impact of studied measures. Theheat demand of the sawmill industry is almost completelycovered by its own by-products; primarily bark, sawdust andwood chips. The increased demand and improved economic value ofwoody biofuels on the market is thus an incentive for thesawmill industry to place more focus on energy issues. Thesawmill industry also has a more or less constant heat loadover the year, which is a beneficial factor for integrationwith district heating networks, biofuel upgrading plants andcombined heat and power plants. The conclusion of the study is that a variety of energyproducts such as heat, unrefined biofuel, pellets andelectricity can be efficiently produced in the sawmill industryand sold for profit to external customers. The payback periodsfor the proposed investments are moderate and both theemissions of volatile organic compounds and global CO2 aredecreased. Should the proposed measures be fully implemented atSwedish sawmills, about 2.8 TWh of biofuel could be savedannually, 0.5 TWh of waste heat could be sold as districtheating and 0.8 TWh of green electricity could be produced.Language: English Keywords:Sawmill industry, energy efficiency, heatrecovery, integration, biofuel, upgrading, district heating,fuel pellets, CHP, VOC, CO2

Green hydrogen produced with renewable electricity has gotten more attention during the last years and its different usage areas has been identified as an important part of the transition to a fossil free society. In this project the potential of a stand-alone hydrogen system and a hydrogen system integrated with a CHP, are investigated regarding technical and economic feasibility. This is done through a case study at Jönköping Energi, a municipal energy company. The main interest for Jönköping Energi is to investigate Power to Mobility, PtM, where electricity is used to produce hydrogen that is sold as fuel for vehicles. Another usage case of interest for the company is Power to Power, PtP. In PtP, electricity is used to produce hydrogen when electricity prices are low, the hydrogen is then stored and later used to produce electricity again when the prices are higher. For a PtM-system an electrolyser, and a hydrogen storage are needed components. In addition to these components, a fuel cell is needed for a PtP-system. Feasible specific technology for Jönköping Energi is recommended based on a literature review and information regarding the CHP.   The combined PtM- and PtP-system is investigated in two contexts, integrated with Jönköping Energi’s CHP and stand-alone. Electricity prices affect the profitability of the studied systems and therefore scenarios with high and low prices are used. A script was created in MATLAB to do the calculations regarding economic and technical feasibility of the integrated and stand-alone system with high and low electricity prices. This resulted in a PtM-system with a Proton exchange membrane electrolyser of 1 MW and a pressurized hydrogen storage tank of 12 MWh, as the most profitable system with a hydrogen demand of 360 kg/day. The integrated system shows slightly higher Net Present Value than the stand-alone system. With low electricity prices, within both contexts, the system is profitable, but with high prices the system is not profitable, neither stand-alone nor integrated. A PtP-system with a Proton exchange membrane fuel cell is not economically viable to include in any system or scenario with current prerequisites. For it to be profitable, more volatile electricity prices than the previous years together with additional income from electricity grid balancing services are needed. Moreover, the investment cost needs to be almost completely subsidised and higher efficiencies of the components than available today are needed as well. The prerequisites needed in order for the PtP-system to be viable is not predicted to be plausible in the near future. However, with low electricity prices, a PtM-system is potentially profitable for Jönköping Energi, both integrated with the CHP and as a stand-alone system.

Renewable energies are fluctuating and the bigger its share on the Swedish energy market, the more fluctuating are the prices. Therefore, CHP plant operators as VEAB in Växjö, are more and more struggling to be competitive. There is, hence, a need of alternative options for the use of produced electricity, rather than being dependent on such a volatile and unclear market. Hydrogen production through water electrolysis could therefore be an alternative to be decoupled from the electricity business and instead being part of a promising, future hydrogen economy. Since state-of-the-art electrolysers have efficiencies between 51% and 75%, it was assessed that some of the efficiency losses could be recuperated by implementing the excess heat in an existing District heating (DH) grid. Calculations of the base scenario electrolyser with a power input of 870 kW showed, that an increase of the overall temperatures of the returning mass flow of the DH grid from 0,05°C to 0,23°C should be achievable. The economic analysis showed, that for this size of hydrogen production unit, the minimum hydrogen selling price (MHSP) would be 6,64 €/kg, which is not competitive on today’s market. However, the sensitivity analysis showed, that by a decreased investment cost, lower electricity prices and especially by scaling up the base scenario, the MHSP could be lowered significantly. Assuming a reduction of investment costs of 20% and scaling up the electrolyser by 1000% to 8700 kW, the MHSP resulted in 1,9 €/kg, a competitive price on the market. This study revealed that hydrogen production could be part of the future business model of CHP plant operators and provides a guideline on the feasibility of such a project.

An 15 Biogas-BHKW mit und ohne Abgasreinigung (Katalysator bzw. thermische Nachverbrennung) wurden Emissionsmessungen durchgeführt, davon an drei Anlagen über einen Zeitraum von 21 Tagen. Neben der Ermittlung der Formaldehyd- und Geruchsemissionen sollten dabei auch Erkenntnisse über die Standzeit von Abgasreinigungsanlagen gewonnen werden. Die wesentlichen Ergebnisse waren: 1. Der zulässige Grenzwert für Formaldehyd (Altanlagen: 60 mg/m³, Neuanlagen: 40 mg/m³) wurde von den meisten untersuchten Anlagen eingehalten, bei einem Teil der Anlagen wurde allerdings der NOx-Grenzwert von 500 mg/m³ überschritten. 2. Mittels Katalysatoren lassen sich Formaldehydemissionen deutlich reduzieren, Methanemissionen (Schlupf) dagegen nicht. 3. Aussagen über Standzeiten von Katalysatoren sind derzeit nicht möglich. 4. Mittels thermischer Nachverbrennung sind sowohl bei Formaldehyd als auch Methan sehr niedrige Reingaswerte erreichbar, die dazu auch noch hohe Standzeiten aufweisen. 5. Ein negativer Einfluss der Abgasreinigungsanlagen auf die Geruchsemissionen war nicht festzustellen.

Traditional power plants only utilize about 30 percent of the primary energy that they consume, and the rest of the energy is usually wasted in the process of generating or transmitting electricity. On-site and near-site power generation has been considered by business, labor, and environmental groups to improve the efficiency and the reliability of power generation. Combined heat and power (CHP) systems are a promising alternative to traditional power plants because of the high efficiency and low CO2 emission achieved by recovering waste thermal energy produced during power generation. A CHP operational algorithm designed to optimize operational costs must be relatively simple to implement in practice such as to minimize the computational requirements from the hardware to be installed. This dissertation focuses on the following aspects pertaining the design of a practical CHP operational algorithm designed to minimize the operational costs: (a) real-time CHP operational strategy using a hierarchical optimization algorithm; (b) analytic solutions for cost-optimal power generation unit operation in CHP Systems; (c) modeling of reciprocating internal combustion engines for power generation and heat recovery; (d) an easy to implement, effective, and reliable hourly building load prediction algorithm.

To achieve greater economic stability, CHP plant operators such as VEAB from Växjö are motivated to search for a new business model that are compatible with their existing facilities while also contribute to increasing the overall revenue of the company. These processes include hydrogen production and biochemical products such as biopolymer and biofuels. However, these processes also produce a substantial amount of heat that needs to be taken care of. Alternatively, the extra heat storage capacity could allow the plant to be more selective of when to produce those heat to maximize profit. Therefore, it is important to investigate different approaches to achieve that, both traditional approach (e,g, convective cooling) and alternative approaches (different large scale underground heat storages). Lake source cooling is also investigated to determine whether it can replace convective cooling as a method of cooling off waste heat from the plant. The technical analysis showed that the alternative approach is certainly promising albeit with more land use (BTES requiring 36 000 m2 against 750 m2 of convectional cooling system) with some limitations that must be addressed when deciding the appropriate approach. In addition, it is found that by increasing the scale of the BTES system, the amount of heat loss per heat capacity reduces while increasing the borehole depth decreases the overall heat loss of the system. The economic analysis showed that when used solely to deal with the waste heat, the alternative approach is costs magnitude more than convective cooling, the alternative costing almost 6 times more than the convective cooling. There are certainly opportunities in the future that can make the BTES system to be a much more feasible choice if additional utilization of the BTES system could be found or potential demand may make the BTES system a more attractive choice to deal with the excess heat that comes with expanding the business of a CHP plant operator.

The Swedish energy system is changing and two major events that are taking place are the phase out of nuclear power and the increase of wind power. The associated changes affect the electricity market and the electricity producers, including combined heat and power plants. This thesis evaluates the Swedish energy system of 2025 with focus on electricity spot prices. It also investigates how a combined heat and power plant might perform in the future, given certain changes in the electricity price. Six different scenarios are developed where the electricity price is modified according to findings with regards to the influence of wind- and nuclear power. A model of a combined heat and power plant and a district heating network is created in BoFiT. The scenarios are applied to the model and results are analyzed in terms of heat production, choice of operational mode, merit order and economical performance. Major findings show a more volatile electricity price in 2025. Low price hours (<100SEK/MWh) occur throughout the year, while high price hours (>640SEK/MWh) take place mostly during winter - the season during which the heat demand is at its peak. Results show that the developed electricity prices require much more regulation from the modelled power plant and that the power plant is more adapted to handling high price hours than low price hours. The district heating network is also affected by the volatile electricity prices, and more frequent and greater variations are observed in the merit order. This suggests that in the future, the electricity prices will need to be followed more actively, and that a strategy will need to be developed, allowing for quick adaptation to the prices - communication and cooperation between the different actors in the network will be needed. / Sveriges energisystem är i förändring där avvecklingen av kärnkraft och ökad implementering av vindkraft är i fokus. Konsekvenserna av dessa förändringar kommer påverka elmarknaden och därmed elproducenterna, bland dem kraftvärmeverk. Detta examensarbete utvärderar energisystemet i Sverige 2025 med fokus på elmarknaden. Arbetet undersöker också hur ett kraftvärmeverk kan prestera i framtiden baserat på förändringar i elpriset. Sex olika scenarios har utvecklats där elpriset har modifierats baserat på analysen av vind- och kärnkraftsutvecklingen i Sverige och dess påverkan på elpriset. Ytterligare skapas en modell av ett kraftvärmeverk och ett fjärrvärmenät i BoFiT. Scenarierna implementeras i modellen och resultat extraheras och analyseras baserat på värmeproduktion, val av driftläge, körordning i systemet samt ekonomisk prestanda. Resultaten visar främst att volatiliteten i elpriset ökar till 2025. Låga elpristimmar (<100SEK/MWh) visar sig inträffa under hela året medan höga elpristimmar(>640 SEK/MWh) dominerar under vintern - säsongen där efterfrågan på värme är som högst. Resultaten visar att det förväntade elpriset kräver högre reglering av det modellerade kraftvärmeverket och att anläggningen idag är anpassad för att hantera framförallt höga elpriser men inte låga elpriser. Även fjärrvärmenätet i sig påverkas av volatilitet i elpriserna och mer frekventa och större variationer observeras i körordningen. Detta antyder att elpriserna i framtiden måste följas mer aktivt och att en strategi, som möjliggör snabb reglering för anpassning av elpriserna, måste utvecklas. Kommunikation och samarbete mellan parterna i fjärrvärmesystemet kommer därmed vara av hög betydelse.

With over one hundred years of commercial cultivation, sugar cane is one of the most valuable agricultural botanical resources in the World. This position is not only based on production of sugar from sugar cane but also it is, to a great extent, as a result of the increasing importance of sugar cane by-products and side industries. Furthermore, with the advancement of science; awareness of inharmonious growth of materials and energy consumption, and the desire to minimize the negative impacts of industrial pollutants and materials, the scope for using sugar cane is still developing rapidly. Bagasse, molasses and filtered mud are the most important by-products in the process of production of sugar from sugar cane. Among these by-products, bagasse is both a biomass resource for producing energy and is one of the most important agricultural wastes, which can be used in different side industries. Therefore, it was chosen for study in this research as it offers considerable potential as a source of energy. Bagasse is often used as a primary fuel source for sugar mills; when burned in quantity, it produces sufficient heat energy to supply all the needs of a typical sugar mill, with energy to spare. To this end, today a secondary use for this waste product is in combined heat and power plants where its use as a fuel source provides both heat and power. With a suitable energy production technology, bagasse can be used as a fuel in CHP for high efficiency energy generation. Today, with regard to the low efficiency of traditional methods, the high cost of disposal of waste materials and environmental pollution, the use of modern methods such as anaerobic digestion for the production of biogas has increased. The collected biogas from the process of anaerobic digestion provides a renewable energy source similar to natural gas, but with less methane and lower heating value, that is suitable for use in CHP plants. In this research, a comparison with different bagasse energy production technologies leads to the selection of anaerobic digestion as the most suitable for use in Iran. Then a typical biogas CHP is assumed, and the biogas system is designed. Finally, the potential for the development of biogas CHP plants with bagasse in Iran is addressed through a study of the economic and environmental aspects.

Cooling, Heating, and Power (CHP) is an emerging category of energy systems consisting of power generation equipment coupled with thermally activated components. The application of CHP systems to residential and small commercial buildings is known as micro-CHP (m-CHP). This instructional module has been developed to introduce engineering students to m-CHP. In the typical engineering curriculum, a number of courses could contain topics related to m-CHP. Thermodynamics, heat transfer, HVAC, heat and power, thermal systems design, and alternate energy systems courses are appropriate m-CHP topics. The types of material and level of analysis for this range of courses vary. In thermodynamics or heat transfer, basic problems involving a m-CHP flavor are needed, but in an alternate energy systems course much more detail and content would be required. This instructional module contains both lecture material and a compilation of problems/exercises for both m-CHP systems and components.