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From Combined Heat and Power to Polygeneration
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In order to reach targets on reducing greenhouse gas emissions from fossil resources it is necessary to reduce energy losses in production processes. In polygeneration, several processes are combined to complement each other to avoid sub-optimization of the standalone processes. This thesis addresses polygeneration with focus on Combined Heat and Power (CHP) production integrated with other processes. Biomass-fired CHP plants are commonly dimensioned to have surplus heat production capacity during periods with lower heat demand. At the same time, production of biomass based vehicle fuels and fuel upgrading are heat demanding processes. The opportunity to combine CHP with ethanol production from lignocellulosic feedstock and torrefaction with the aim of replacing fossil fuels are used as cases during the evaluation of polygeneration. Simulation models are used to investigate the performance of CHP integrated with production of ethanol and torrefaction. Measured data from commercial CHP plants have been used to reflect the operation boundaries. The findings show that polygeneration can compete with stand-alone production in both energy and economic performance. Polygeneration offers a wider operating range where reduced minimum load gives increased annual operating time. Therefore, under limited heat demand more renewable electricity production is possible due to increased operating hours and steam extraction from the turbine during part-load operation. Resource availability and fluctuations in fuel price have the largest impact on the profit of polygeneration. Other aspects that have substantial effects on the economy in polygeneration are the electricity spot price and subsidies. Furthermore, it has been proven that the yield of each product in a multiproduct process plant, the size of the plant and the heat demand have a large impact on the economy. Polygeneration turns by-products into buy-products.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2015.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 181
National Category
Mechanical Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-28442ISBN: 978-91-7485-221-9 (print)OAI: oai:DiVA.org:mdh-28442DiVA: diva2:825067
Public defence
2015-09-02, Paros, Mälardalens högskola, Västerås, 13:15 (English)
Opponent
Supervisors
Available from: 2015-07-06 Created: 2015-06-23 Last updated: 2015-08-24Bibliographically approved
List of papers
1. Case study of energy systems with gas turbine cogeneration technology for an eco-industrial park
Open this publication in new window or tab >>Case study of energy systems with gas turbine cogeneration technology for an eco-industrial park
2008 (English)In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 32, no 12, 1128-1135 p.Article in journal (Refereed) Published
Abstract [en]

Eco-industrial parks (EIP) are clusters of industry corporations that collaborate with reusing waste and energy-efficient use of resources with no or minor impact on the environment. This paper presents a case study that examines the feasibility of using gas turbine technology in one industrial park, located in the Dongguan city of the Guangdong province in China. A model of a gas turbine-based combined heat and power (CHP) plant with a heat recovery steam generator for absorption cooling was developed and simulated. A steam-injected gas turbine has been selected in the system to increase electricity production and to generate steam. The study includes performance analysis of the cogeneration plant in terms of thermal efficiency, cost estimation, and greenhouse gas emission. The gas turbine-based cogeneration system has been compared with a baseline reference case that is defined as if all the energy to the industrial park is supplied from the local electricity grid. The results show that the gas turbine-based cogeneration system can reach a total efficiency of 58% and reduce CO2 emissions with 12 700 tons per year. A sensitivity analysis on the costs of the system has also been made based on fuel costs and the interest rate, which shows that the investigated system is economically profitable at natural gas prices below 4.4 RMB m-3 with fixed electricity prices and at electricity prices above 736 RMB MWh-1 with fixed natural gas prices. The sensitivity analysis based on the interest rate showed that the proposed system is economically feasible with interest rates up to 16%.

Keyword
eco-industrial park • EIP • gas turbine, cogeneration, efficiency improvement, steam injection gas turbine
National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-4518 (URN)10.1002/er.1450 (DOI)000260190400007 ()2-s2.0-55949133547 (Scopus ID)
Available from: 2008-12-15 Created: 2008-12-15 Last updated: 2015-07-06Bibliographically approved
2. Integration of torrefaction in CHP plants - A case study
Open this publication in new window or tab >>Integration of torrefaction in CHP plants - A case study
2015 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 90, 427-435 p.Article in journal (Refereed) Published
Abstract [en]

Torrefied biomass shows characteristics that resemble those of coal. Therefore, torrefied biomass can be co-combusted with coal in existing coal mills and burners. This paper presents simulation results of a case study where a torrefaction reactor was integrated in an existing combined heat and power plant and sized to replace 25%, 50%, 75% or 100% of the fossil coal in one of the boilers. The simulations show that a torrefaction reactor can be integrated with existing plants without compromising heat or electricity production. Economic and sensitivity analysis show that the additional cost for integrating a torrefaction reactor is low which means that with an emission allowance cost of 37 €/ton CO2, the proposed integrated system can be profitable and use 100% renewable fuels. The development of subsidies will affect the process economy. The determinant parameters are electricity and fuel prices.

Keyword
Biomass, Combined heat and power (CHP), District heating, Polygeneration, Torrefaction, Carbon dioxide, Coal, Cost benefit analysis, Costs, Sensitivity analysis, Additional costs, Combined heat and power, Combined heat and power plants, Electricity production, Emission allowances, Integrated systems, Poly-generation, Cogeneration plants
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-26943 (URN)10.1016/j.enconman.2014.11.019 (DOI)000348886800040 ()2-s2.0-84915745084 (Scopus ID)
Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2017-12-05Bibliographically approved
3. Performance evaluation of adding ethanol production into an existing combined heat and power plant
Open this publication in new window or tab >>Performance evaluation of adding ethanol production into an existing combined heat and power plant
2009 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 101, no 2, 613-618 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, the configuration and performance of a polygeneration system are studied by modelling the integration of a lignocellulosic wood-to-ethanol process with an existing combined heat and power (CHP) plant. Data from actual plants are applied to validate the simulation models. The integrated polygeneration system reaches a total efficiency of 50%, meeting the heating load in the district heating system. Excess heat from the ethanol production plant supplies 7.9MWto the district heating system, accounting for 17.5% of the heat supply at full heating load. The simulation results show that the production of ethanol from woody biomass is more efficient when integrated with a CHP plant compared to a stand-alone production plant. The total biomass consumption is reduced by 13.9% while producing the same amounts of heat, electricity and ethanol fuel as in the stand-alone configurations. The results showed that another feature of the integrated polygeneration system is the longer annual operating period compared to existing cogeneration. Thus, the renewable electricity production is increased by 2.7% per year.

Keyword
Polygeneration, Combined heat and power, Bio-ethanol, Efficiency improvement, Bioenergy
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-6828 (URN)10.1016/j.biortech.2009.07.087 (DOI)000271165700024 ()2-s2.0-70349417698 (Scopus ID)
Projects
Polygeneration
Available from: 2009-09-16 Created: 2009-09-16 Last updated: 2017-12-13Bibliographically approved
4. The impact of lignocellulosic ethanol yields in polygeneration with district heating: A case study
Open this publication in new window or tab >>The impact of lignocellulosic ethanol yields in polygeneration with district heating: A case study
Show others...
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 92, 791-799 p.Article in journal (Refereed) Published
Abstract [en]

The development towards high energy efficiency and low environmental impact from human interactions

has led to changes at many levels of society. As a result of the introduction of penalties on carbon

dioxide emissions and other economic instruments, the energy industry is striving to improve energy

efficiency and climate mitigation by switching from fossil fuels to renewable fuels. Biomass-based combined

heat and power (CHP) plants connected to district heating networks have a need to find uses for the

excess heat they produce in summer when the heat demand is low. On the other hand, the transport sector

makes a substantial contribution to the increasing CO

2

emissions, which have to be reduced. One

promising alternative to address these challenging issues is the integration of vehicle fuel production

with biomass-based CHP plants. This paper presents the configuration and operating profits in terms

of electricity, heat and ethanol fuel from cellulosic biomass. A case study of a commercial small scale

CHP plant was conducted using simulation and modeling tools. The results clearly show that electricity

production can be increased when CHP production is integrated with cellulosic ethanol production. The

findings also show that the economic benefits of the energy system can be realized with near-term commercially

available technology, and that the benefits do not rely solely on ethanol yields.

National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-13297 (URN)10.1016/j.apenergy.2011.08.031 (DOI)000300463800085 ()2-s2.0-84855257802 (Scopus ID)
Available from: 2011-11-17 Created: 2011-11-17 Last updated: 2017-12-08Bibliographically approved
5. Optimal location of lignocellulosic ethanol refineries with polygeneration in Sweden
Open this publication in new window or tab >>Optimal location of lignocellulosic ethanol refineries with polygeneration in Sweden
Show others...
2010 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 35, no 6, 2709-2716 p.Article in journal (Refereed) Published
Abstract [en]

The integration of ethanol production with combined heat and power plants is considered in this paper. An energy balance process model has been used to generate data for the production of ethanol, electricity, heat and biogas. The geographical position of such plants becomes of importance when using local biomass and delivering transportation fuel and heat. An optimization model has thus been used to determine the optimal locations for such plants in Sweden. The entire energy supply and demand chain from biomass outtake to gas stations filling is included in the optimization. Input parameters have been studied for their influence on both the final ethanol cost and the optimal locations of the plants. The results show that the biomass cost, biomass availability and district heating price are crucial for the positioning of the plant and the ethanol to be competitive against imported ethanol. The optimal location to set up polygeneration plants is demonstrated to be in areas where the biomass cost is competitive and in the vicinity of small to medium size cities. Carbon tax does not influence the ethanol cost, but solicits the production of ethanol in Sweden, and changes thus the geography of the plant locations.

Identifiers
urn:nbn:se:mdh:diva-10358 (URN)10.1016/j.energy.2009.07.018 (DOI)000278506400040 ()2-s2.0-77953138345 (Scopus ID)
Available from: 2010-10-04 Created: 2010-10-04 Last updated: 2017-12-12Bibliographically approved

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