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Production Planning of CHP plants in transition towards energy systems with high share of renewables
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0001-7576-760x
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The global energy system is undergoing a transformative change towards renewable energies. The share of Renewable Energy Sources (RES) and bioenergy in the world’s primary energy use has increased in the recent years. Based on the EU Roadmap 2050 energy plan, the share of renewables in final energy use in Europe will reach at least 55%, a 45% increase from its share today.

Due to the intermittent energy supply from renewables, their high penetration in energy systems can jeopardize the system flexibility, in terms of the balance between energy demand and supply. Lack of system flexibility could cause energy curtailments, increase system costs, or make renewables unreliable sources of energy. Moreover, the expansion of the renewable energy supply could influence the operational strategy of existing energy systems like Combined Heat and Power (CHP) plants. Therefore, the current study focuses on increasing system flexibility of a CHP-dominated regional energy system with increased renewable power supply. Two flexibility options, including a polygeneration strategy and large-scale energy storage using power-to-gas technology, were modelled. The system is then optimized using a Mixed Integer Linear Programming (MILP) method to investigate the production planning of CHP plants in a renewable-based energy system with higher level of flexibility. Different technical and market factors could influence the results of the optimization model, and thereby system flexibility. Thus, the study is carried out under various scenarios for better understanding of the future challenges regarding energy supply, market prices, and climate change.

The investigation provides an increased knowledge of production planning for the existing CHP plants with increased interaction with renewables. Based on the overall observations of this thesis, the proposed power storage system contributes to the increased system flexibility. However, the study suggests polygeneration and integration strategy as the optimal pathway to increase RES penetration and to support system flexibility, considering future energy developments and changes in energy demand and supply.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2021.
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 335
National Category
Energy Systems Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-54037ISBN: 978-91-7485-507-4 (print)OAI: oai:DiVA.org:mdh-54037DiVA, id: diva2:1548103
Public defence
2021-06-18, Delta + digitalt via Zoom, Mälardalens högskola, Västerås, 09:00 (English)
Opponent
Supervisors
Available from: 2021-04-29 Created: 2021-04-29 Last updated: 2021-07-01Bibliographically approved
List of papers
1. Optimization of a regional energy system including CHP plants and local PV system and hydropower: Scenarios for the County of Västmanland in Sweden
Open this publication in new window or tab >>Optimization of a regional energy system including CHP plants and local PV system and hydropower: Scenarios for the County of Västmanland in Sweden
2019 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 230, p. 1111-1127Article in journal (Refereed) Published
Abstract [en]

Providing the energy needs of the cumulatively increasing population has become a challenge for the regional energy systems in the world. The most critical challenge is to supply enough energy in the forms of heat and power during the cold and warm periods of the year with the lowest production cost and minimum environmental impacts. A solution is to increase the green energy supply from renewable energy resources such as solar, wind power, and hydropower. In order to apply this solution in the real energy system, potentials for clean energy supply in an optimized manner should be evaluated. In this study, an optimization model is developed for a regional energy system in the central part of Sweden. The studied system consists of Combined Heat and Power (CHP)plants and heat water boilers together with renewable energy supply from rooftop Photo Voltaic (PV)- solar collectors and regional hydropower plants. The General Algebraic Modeling System (GAMS)is used to create the model based on the Mixed Integer Linear Programming (MILP)method. The goal is to evaluate the influence of local renewable energy systems on the production planning of CHP plants in a region. Two different scenarios are investigated based on the extremes in energy supply and demand concerning the increased use of Electrical Vehicles (EVs)and more application of Heat Pumps (HPs)in the system. The results show that installation of rooftop PV systems has the potential to reduce the electricity import to the region; however, it will at the same time reduce the operation time of the CHP plans during the summer period. With increased use of HPs for heating, the shut off time for CHP plants is further increased. Increase in electric passenger cars penetration in the system has no impacts on the production profiles of the plants. The regional electricity demand grows significantly by more utilization of EVs and increased application of heat pumps in the studied system. The high electricity demand will mainly be satisfied by importing electricity from outside the region together with low production from CHP plants and the power generated by the rooftop PV systems and regional hydropower. The developed optimization model with studied scenarios can be applied to other energy systems to increase the knowledge of production planning and feasibility of a fossil fuel free energy system.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Electrical vehicle, Heat pump, Optimization, Production planning, Renewable energy resource, Algebra, Cogeneration plants, Economics, Electric power utilization, Energy policy, Environmental impact, Fossil fuels, Free energy, Heat pump systems, Hydroelectric power, Hydroelectric power plants, Integer programming, Planning, Power generation, Production control, Pumps, Renewable energy resources, Wind power, Clean energy supplies, Combined heat and power, Electrical vehicles, Heat pumps, Mixed-integer linear programming, Optimization modeling, Regional energy systems, Electric power system interconnection
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-43876 (URN)10.1016/j.jclepro.2019.05.086 (DOI)000474676300098 ()2-s2.0-85065879762 (Scopus ID)
Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2021-11-30Bibliographically approved
2. Power-to-hydrogen storage integrated with rooftop photovoltaic systems and combined heat and power plants
Open this publication in new window or tab >>Power-to-hydrogen storage integrated with rooftop photovoltaic systems and combined heat and power plants
2020 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 276, article id 115499Article in journal (Refereed) Published
Abstract [en]

The growing share of intermittent renewable energy sources for power generation indicates an increasing demand for flexibility in the energy system. Energy storage technologies ensure a balance between demand and supply and increase the system flexibility. This study investigates increased application of renewable energy resources at a regional scale. Power-to-gas storage that interacts with a large-scale rooftop photovoltaic system is added to a regional energy system dominated by combined heat and power plants. The study addresses the influence of the storage system on the production planning of the combined heat and power plants and the system flexibility. The system is modeled and the product costs are optimized using the Mixed Integer Linear Programming method, as well as considering the effects on CO2 emissions and power import into the regional system. The optimization model is investigated by developing different scenarios for the capacity and cost of the storage system. The results indicate that the proposed storage system increases the system flexibility and can reduce power imports and the marginal emissions by around 53%, compared with the current energy system. There is a potential to convert a large amount of excess power to hydrogen and store it in the system. However, because of low efficiency, a fuel cell cannot significantly contribute to power regeneration from the stored hydrogen. Therefore, for about 70% of the year, the power is imported to the optimized system to compensate the power shortfalls rather than to use the fuel cell. 

Place, publisher, year, edition, pages
Oxford: Elsevier Ltd, 2020
Keywords
Flexibility, Hydrogen, Optimization, Power-to-gas, Production planning, Renewable energy sources, Cogeneration plants, Fuel cells, Hydrogen storage, Integer programming, Photovoltaic cells, Production control, Renewable energy resources, Energy storage technologies, Mixed integer linear programming, Optimization modeling, Regional energy systems, Renewable energy source, Rooftop photovoltaic systems, System flexibility, Electric power system interconnection, alternative energy, combined heat and power, energy resource, energy storage, fuel cell, photovoltaic system, power generation
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-49483 (URN)10.1016/j.apenergy.2020.115499 (DOI)000571786500002 ()2-s2.0-85088401042 (Scopus ID)
Available from: 2020-08-06 Created: 2020-08-06 Last updated: 2021-04-29Bibliographically approved
3. Evaluation of biofuel production integrated with existing CHP plants and the impacts on production planning of the system – A case study
Open this publication in new window or tab >>Evaluation of biofuel production integrated with existing CHP plants and the impacts on production planning of the system – A case study
2019 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 252, article id 113461Article in journal (Refereed) Published
Abstract [en]

The increasing atmospheric CO2 concentration has caused a transformative shift in global energy systems, which is contributing to an increased use of renewables. Sweden is among the countries trying to shift to a fossil-fuel-free system in all energy sectors. This paper addresses the fuel demand and supply in the transportation sector in the county of Västmanland in Sweden. A Mixed Integer Linear Programming optimization model is developed to minimize cost in the studied system. The model is further used to investigate the influence of three different scenarios on production planning of regional Combined Heat and Power (CHP) plants: (1) straw-based biofuel production integrated with existing CHP plants to fuel combustion engine vehicles, (2) use of electric vehicles, and (3) use of hybrid vehicles fueled by both electricity and bioethanol. Potential solar power generation from rooftop solar cells is also included in the model. The energy system in scenario 2 is found to have the highest overall system efficiency; however, a large amount of power needs to be imported to the system. Hybrid vehicles can potentially reduce the electricity import and CO2 emissions compared to the current situation. Electricity production from rooftop solar collectors could provide the energy needs of the vehicles during summer, while regionally produced straw-based bioethanol integrated with CHP plants can satisfy the fuel needs of the vehicles in winter. This approach could affect the production planning of CHP plants, result in less fuel use and increase the share of renewable resources in the regional transportation system. 

Keywords
Electric vehicles, Energy systems, Mixed Integer Linear Programming, Optimization, Straw-based bioethanol, Transportation sector
National Category
Energy Engineering
Identifiers
urn:nbn:se:mdh:diva-44658 (URN)10.1016/j.apenergy.2019.113461 (DOI)000497968000059 ()2-s2.0-85067284871 (Scopus ID)
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2021-11-30Bibliographically approved
4. Impacts of integrating pyrolysis with existing CHP plants and onsite renewable-based hydrogen supply on the system flexibility
Open this publication in new window or tab >>Impacts of integrating pyrolysis with existing CHP plants and onsite renewable-based hydrogen supply on the system flexibility
Show others...
2021 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 43, article id 114407Article in journal (Other academic) Published
Abstract [en]

The share of renewable energy sources in the primary energy use is increasing worldwide. Given the intermittency of the energy supply from renewables, it is important to increase flexibility in the system to respond to the imbalances between energy demand and supply. Several flexibility options such as power storage and energy integration are currently in use, mostly at small scales. The increased energy supply from renewables and the flexibility solutions can influence the production planning of existing thermal energy conversion plants. In this study, integration of energy technologies including a hydrotreated pyrolysis oil production integrated with existing CHP plants is investigated as a flexibility solution. The system interacts with potential power generation from rooftop PV systems integrated with power-to-hydrogen storage. A cost-optimization model is developed using MILP method. The study focuses on the system flexibility and operational strategy of the existing CHP plants considering market trends, climate changes, and future energy developments with increased penetration of heat pumps and electric vehicles but less fossil fuels use. The results indicate that the suggested integrated system can increase the local energy supply by 33 GWh. Moreover, the power-to-hydrogen storage and onsite hydrogen use can increase the share of renewables in energy supply by 6%. Optimization of the developed scenarios for future energy-related changes indicates that the market trends could significantly reduce the performance of the system by 21% but increase the penetration of renewables in the system by 8%. Overall, scenario analysis shows the potential of using such a polygeneration system for flexible energy supply including existing CHP plants. 

National Category
Energy Engineering Energy Systems
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-54036 (URN)10.1016/j.enconman.2021.114407 (DOI)000679381500008 ()2-s2.0-85108584322 (Scopus ID)
Available from: 2021-04-29 Created: 2021-04-29 Last updated: 2022-11-25Bibliographically approved
5. A multi-criteria analysis to assess the optimal flexibility pathway for regional energy systems with high share of renewables
Open this publication in new window or tab >>A multi-criteria analysis to assess the optimal flexibility pathway for regional energy systems with high share of renewables
2021 (English)Conference paper, Oral presentation only (Refereed)
National Category
Energy Systems Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-54035 (URN)
Conference
International Conference on Applied Energy, ICAE 12th
Available from: 2021-04-29 Created: 2021-04-29 Last updated: 2023-09-25Bibliographically approved

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