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Regional Energy Systems with Retrofitted Combined Heat and Power (CHP) Plants
Mälardalen University, School of Sustainable Development of Society and Technology. (BIoenergy Group)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fossil fuel depletion, economic development, urban expansion and climate change present tough challenges to municipal- and regional-scale energy systems. Regional energy system planning, including waste treatment, renewable energy supply, energy efficiency, and climate change, are considered essential to meet these challenges and move toward a sustainable society. This thesis includes studies on energy system from municipal waste, potential for a fossil fuel-independent regional energy system with increased renewable energy products using waste as one of energy sources, and the performance of biomass-fired combined heat and power (CHP) plants. A top-down method is adopted to organize the studies, from national waste-to-energy (WtE) scenarios to individual energy plants.

The first study considers the overall potential contribution of WtE to energy supply and greenhouse gas (GHG) emissions mitigation in Sweden until 2050 under several different scenarios. Depending on WtE scenario considered, the study shows that WtE can supply energy between 38 and 186 TWh and mitigate between CO2 of 1 and 12 Mt per year by 2050 based on the baseline of year 2010.

At a regional level, static and dynamic optimization models with a focus on WtE are developed for two regions in Sweden and Finland. The former is used to investigate the possibilities of optimal positioning of new energy plants, retrofitting existing energy plants and planting energy crops. The latter case study is on regional heat and power production using biogas generated from agricultural and livestock wastes. Centralized biogas production units perform better than distributed production regarding energy and carbon balance though the net energy output is negligible. However, a significant GHG emission can be reduced compared to the present status.

Retrofitting existing conventional CHP plants is another option for improving regional energy system. The study shows that integrating heat-demanded processes such as drying, bioethanol and pellet production with existing CHP plants can improve overall energy efficiency and power output, increase annual operation time and reduce production cost as well as mitigate GHG emissions.

 It is recommended that building new WtE/energy plants at optimum sites, upgrading the existing energy plants, expanding the agricultural/forestry waste/residues output (biomass) and planting more energy crops shall be taken into considerations for the future regional energy systems.

Abstract [sv]

Utarmning av fossila bränslekällor, ekonomisk utveckling, städernas utbredning och klimatförändring är svåra utmaningar för kommunala- och regionala energisystem. Planering av det regionala energisystemet, inklusive avfallshantering, förnyelsebara energikällor, energieffektivisering och hänsyn till klimatförändringar, anses avgörande för att möta dessa utmaningar och gå mot ett hållbart samhälle. Denna avhandling innehåller studier av energisystem centrerad kring hushållsavfall, potentialet för fossilbränslefria regionala energisystem som utnyttjar ökad andel förnyelsebara energiprodukter med avfall som en energikälla och prestandautvärdering av ett biomassa-eldat kraftvärmeverk. Studierna har organiserats efter storlek på system, från nationella avfall-till-energi scenarier till enskilda kraftverk.

 

Den första studien behandlar övergripande möjligheten att genom avfall-till-energi bidra till energiförsörjningen och begränsa utsläppet av växthusgaser i Sverige till 2050 under flera olika scenarier. Beroendet på avfall-till-energiscenario visar studien att genom att utnyttja avfall kan mellan 38 och 186 TWh energi levereras och dessutom kan koldioxidutsläppen reduceras med 1-12 miljoner ton till år 2050 med 2010 som basår.

 

På den regionala nivån, statiska och dynamiska optimeringsmodeller, med fokus på avfall-till-energi, är utvecklats för två regioner, en i Sverige och en i Finland. Det första modellen används för hitta den optimala placeringen av nya energianläggningar, anpassning av befintliga anläggningar och placering av odlingar av energigrödor. Den senare ingår i en fallstudie av den regionala kraft- och värmeproduktionen genom utnyttjande av biogas producerad från jordbruksavfall och djurgödsel. Centraliserade biogasanläggningar presterar bättre än decentraliserad anläggningar när det gäller energi – och kolbalanser även om i båda fallen så är skillnaden mellan konsumerad mängd bränsle, värme och el och producerad värme och el försumbar. Däremot kan en betydande mängd av växthusgasutsläppet i båda fallen undvikas jämfört med nuläget.

 

Anpassning av befintliga konventionella kraftvärmeverk är ett annat alternativ för att förbättra det regionala energisystemet. Studien visar att genom att integrera värmekrävande processer såsom torkning, bioetanol- och pelletsproduktion med befintliga kraftvärmeverk kan den totala energieffektiviten och uteffekten förbättras, öka den årliga drifftiden och minska produktionskostnaderna och utsläppen av växthusgaser.

 

Rekommendationen är att för de framtida regionala energisystemen överväga att bygga nya avfall-till-energianläggningar med optimal placering, uppgradera befintliga energianläggningar utöka insamlandet av avfall/restprodukter från jord- och skogbruk och plantera mer energigrödor.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2012. , 66 p.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 132
Keyword [en]
Combined heat and power, Waste-to-Energy (WtE), Regional energy system, Greenhouse gases (GHG), Retrofitting, Optimization
Keyword [sv]
Kraftvärme, Avfall-till-Energi, Regionala Energisystem, Växthusgaser, Uppgradering, Optimering.
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-15966ISBN: 978-91-7485-085-7 (print)OAI: oai:DiVA.org:mdh-15966DiVA: diva2:563573
Public defence
2012-12-10, Milos, Hogskolenplan 1, Vasteras, 13:30 (English)
Opponent
Supervisors
Available from: 2012-10-31 Created: 2012-10-29 Last updated: 2012-11-15Bibliographically approved
List of papers
1. Modeling and optimization of a regional waste-to-energy system: a case study in central Sweden
Open this publication in new window or tab >>Modeling and optimization of a regional waste-to-energy system: a case study in central Sweden
2011 (English)Conference paper, (Refereed)
Abstract [en]

Conversion of wastes to energy by different technologies can contribute greatly to treating waste sustainably, reducing dependency on imported fossil fuels and protecting environment. A static model of energy balance for a certain region is constructed to simulate and optimize the energy system with the purpose to minimize the total costs, including collection, transportation and conversion or treatment of wastes, distribution of energy products as well as import and export of wastes and energy products. The objective is to find optimum positions for building new energy plants and planting energy crops for two scenarios. How to achieve a regional fossil-fuel-free energy system is also analyzed through a case study of the County of Västmanland in central Sweden. The boundary conditions are assumed to be the limit of local waste generation, capacity of energy plants, and the demands of energy products.

Keyword
waste, sustainable energy system, fossil-fuel-free, optimization
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-13190 (URN)
Conference
Proceedings Sardinia 2011, Thirteenth International Waste Management and Landfill Symposium. S. Margherita di Pula, Cagliari, Italy; 3 - 7 October 2011
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2012-11-15Bibliographically approved
2. WASTE-TO-ENERGY SCENARIOS ANALYSIS BASED ON ENERGY SUPPLY AND DEMAND IN SWEDEN
Open this publication in new window or tab >>WASTE-TO-ENERGY SCENARIOS ANALYSIS BASED ON ENERGY SUPPLY AND DEMAND IN SWEDEN
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2012 (English)Conference paper, (Other academic)
Abstract [en]

Energy recovery from waste treatment is of great significance for the waste management and sustainable energy supply. Sweden has proposed an ambitious vision of zero net greenhouse gases emissions by 2050, which makes most possible use of resources that the waste represents necessary. This paper is to study how the waste-to-energy (WtE) can interact with other forms of renewable energy to affect the energy supply and demand in Sweden. Based on an assumption of waste generation-treatment balance in 2050 with two cases, power preference and motor fuels preference, are investigated under diverse WtE scenarios. The results indicate that WtE production can contribute to the primary energy supply by 38 to 186 TWh, amounting to 6% to 47% of the total. The power production can be ranged from 7 to 35 TWh and motor fuels from 2 to 34 TWh through under different WtE scenarios. Furthermore, the final mitigation of CO2 emission is estimated to be from 1 to 12 Mt in 2050 compared to base year of 2010, really depending on which WtE scenario is considered.

Keyword
waste-to-energy, scenarios, energy, waste treatment.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-15960 (URN)
Conference
International Conference on Applied Energy ICAE 2012, Jul 5-8, 2012, Suzhou, China
Note

paper ID: A10727

Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2014-12-02
3. A dynamic model to optimize a regional energy system with waste and crops as energy resources for greenhouse gases mitigation
Open this publication in new window or tab >>A dynamic model to optimize a regional energy system with waste and crops as energy resources for greenhouse gases mitigation
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2012 (English)In: Energy, ISSN 0360-5442, Vol. 46, no 1, 522-532 p.Article in journal (Other academic) Published
Abstract [en]

A dynamic model of a regional energy system has been developed to support sustainable waste treatmentwith greenhouse gases (GHG) mitigation, addressing the possibility for development towardsa regional fossil fuel-free society between 2011 and 2030. The model is based on conventional mixedinteger linear programming (MILP) techniques to minimize the total cost of regional energy systems. TheCO2 emission component in the developed model includes both fossil and biogenic origins whenconsidering waste, fossil fuels and other renewable sources for energy production. A case study for thecounty of Västmanland in central Sweden is performed to demonstrate the applicability of the developedMILP model in five distinct scenarios. The results show significant potential for mitigating CO2 emissionby gradually replacing fossil fuels with different renewable energy sources. The MILP model can be usefulfor providing strategies for treating wastes sustainably and mitigating GHG emissions in a regionalenergy system, which can function as decision bases for formulating GHG reduction policies andassessing the associated economic implications.

Keyword
Waste, Regional energy system, Dynamic, Mixed integer linear programming, Fossil-fuel-free, Sustainable
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-15961 (URN)10.1016/j.energy.2012.07.060 (DOI)000311873700053 ()2-s2.0-84867225896 (Scopus ID)
Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2014-12-02Bibliographically approved
4. Techno-economic analysis of an integrated biorefinery system for poly-generation of power, heat, pellets and bioethanol
Open this publication in new window or tab >>Techno-economic analysis of an integrated biorefinery system for poly-generation of power, heat, pellets and bioethanol
2014 (English)In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 38, no 5, 551-563 p.Article in journal (Refereed) Published
Abstract [en]

Bioethanol is an alternative to fossil fuels in the transportation sector. The use of pellet for heating is also an efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno-economic performance of a biorefinery system in which an existing combined heat and power (CHP) plant is integrated with the production of bioethanol and pellet using straw as feedstock. A two-stage acid hydrolysis process is used for bioethanol production, and two different drying technologies are applied to dry hydrolysis solid residues. A sensitivity analysis is performed on critical parameters such as the bioethanol selling price and feedstock price. The bioethanol production cost is also calculated for two cases with either 10 year or 15 year payback times. The results show that the second case is currently a more feasible economic configuration and reduces production costs by 36.4%-77.3% compared to other types of poly-generation plants that are not integrated into existing CHP plants. 

Keyword
combined heat and power, pellet, biorefinery, drying, integrated, bioethanol, straw
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-15965 (URN)10.1002/er.3039 (DOI)000332988300002 ()2-s2.0-84895924485 (Scopus ID)
Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2014-11-20Bibliographically approved
5. Annual performance analysis and comparison of pellet production integrated with an existing combined heat and power plant
Open this publication in new window or tab >>Annual performance analysis and comparison of pellet production integrated with an existing combined heat and power plant
2011 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 102, no 10, 6317-6325 p.Article in journal (Refereed) Published
Abstract [en]

Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials (wood chips and solid hydrolysis residues) are studied. The year is divided into 12 periods, and the integrated biorefinery systems are modeled and simulated for each period. The annual economic performance of three integrated biorefinery systems is analyzed based on the simulation results. The option of pellet production integrated with the existing CHP plant with the exhaust flue gas and superheated steam as drying mediums has the lowest specific pellet production cost of 105 €/tpellet, the shortest payback time of less than 2 years and the greatest CO2 reduction of the three options. An advantage in common among the three options is a dramatic increase of the total annual power production and significant CO2 reduction in spite of a small decrease of power efficiency.

Keyword
Combined heat and power, pellet, integration, overall energy efficiency
National Category
Engineering and Technology
Research subject
Biotechnology/Chemical Engineering
Identifiers
urn:nbn:se:mdh:diva-13189 (URN)10.1016/j.biortech.2011.02.042 (DOI)000291125800107 ()2-s2.0-79955021073 (Scopus ID)
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2014-01-07Bibliographically approved
6. Influence of drying process on the biomass-based polygeneration system of bioethanol, power and heat
Open this publication in new window or tab >>Influence of drying process on the biomass-based polygeneration system of bioethanol, power and heat
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 90, no 1/SI, 32-37 p.Article in journal (Refereed) Published
Abstract [en]

One of the by-products from bioethanol production using woody materials is lignin solids, which can be utilized as feedstock for combined heat and power (CHP) production. In this paper, the influence of integrating a drying process into a biomass-based polygeneration system is studied, where the exhaust flue gas is used to dry the lignin solids instead of direct condensation in the flue gas condenser (FGC). The evaporated water vapor from the lignin solids is mixed with the drying medium for consequent condensation. Thus, the exhaust flue gas after the drying still has enough humidity to produce roughly the same amount of condensation heat as direct condensation in the existing configuration. The influence of a drying process and how it interacts with the FGC in CHP production as a part of the  polygeneration system is analyzed and evaluated. If a drying process is integrated with the polygeneration system, overall energyefficiency is only increased by 3.1% for CHP plant, though the power output can be increased by 5.5% compared with the simulated system using only FGC.

Keyword
Bioethanol, lignin, drying, exhaust flue gas condenser, moisture content, polygeneration
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-13186 (URN)10.1016/j.apenergy.2011.02.019 (DOI)000297426100006 ()2-s2.0-80055041225 (Scopus ID)
Available from: 2011-10-27 Created: 2011-10-27 Last updated: 2013-12-04Bibliographically approved
7. A regional model for sustainable biogas electricity production: A case study from a Finnish province
Open this publication in new window or tab >>A regional model for sustainable biogas electricity production: A case study from a Finnish province
2013 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 102, 676-686 p.Article in journal (Other academic) Published
Abstract [en]

A regional model for sustainable biogas electricity production was formulated and tested for a Finnishprovince, North-Savo. By using the model the aim was to support decision making for reducing greenhousegas (GHG) emissions and increasing renewable energy (RE) production in the studied region inthe biogas electricity production system. The system boundary of the model included transportation ofwaste, biogas production, heat and electricity production, as well as the delivery of heat and digestateto the end users. When electricity production was maximized in the studied region, the electricity productionand GHG emissions were 20 GW h/year and 24 kt/year of CO2 equivalent, respectively. WhenGHG emissions were minimized, the electricity production and GHG emissions were 20 GW h/year and23 kt/year of CO2 equivalent, respectively. By producing electricity of 20 GW h/year, the maximumGHG reductions were roughly 74% of the theoretical maximum GHG emissions of 90 kt/year of CO2 equivalentin both cases. The regional electricity production potential of 20 GW h/year was only 21% of themaximum electricity production potential of 94 GW h/year. The locations of biogas plants, regional relativeGHG emissions, potential feedstocks and regional electricity production were optimized in bothcases in the studied region.

National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-15962 (URN)10.1016/j.apenergy.2012.08.018 (DOI)000314190800073 ()2-s2.0-84870763824 (Scopus ID)
Available from: 2012-10-29 Created: 2012-10-29 Last updated: 2014-06-16Bibliographically approved

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