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Integration of Distributed Renewable Energy and Energy Storages in Buildings
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes. (Division of Energy Processes)ORCID iD: 0000-0001-8271-7512
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photovoltaic (PV) is a distributed renewable energy technology that is suitable for integration in buildings. PV reduces the electricity demands as well as the greenhouse gas emissions of buildings. However, the surplus electricity from PV is exported to the electricity grid, which not only lowers the economic performance of the PV but also creates operational problems in the grid. Efficient approaches should be identified to improve PV’s economic and environmental performance.

Buildings differ by their connections to energy networks. In buildings that are only connected to the electricity grid, electrical energy storages— including battery and hydrogen storage—can mitigate the mismatch between production and consumption. When a grid-connected PV system follows the conventional operation strategy, its economic performance worsens with storage. Two new operation strategies are developed. With a developed optimization framework, operation strategies and storage capacities are optimized simultaneously. Optimization results indicate that both net present value and self-sufficiency ratio are increased by storages. A comparison between battery storages and hydrogen storages shows that the hydrogen storage can compete with the battery counterpart under an optimistic hydrogen storage cost scenario. In addition, the hydrogen storage can better decrease the exported electricity.

In buildings that are connected to the electricity grid and the district heating network, additional energy conversion and storage equipment— including heat pumps, electrical heaters, and hot water tanks—can be installed to form an integrated energy system (IES). After optimal system sizing, the IES decreases the net present cost by 22%, and the self-consumption ratio increases from 43% to 61%. Moreover, the IES serves as a new flexibility measure, and the provided flexibility energy is over 36% of its electricity consumption. During system planning, the system configuration and operation cost are obtained without considering forecast errors. Through the year-round simulation of system operation that considers forecast errors, a corrected operation cost is obtained. The yearly operation cost difference between system operation and system planning is less than 4% and 6% under the high and low forecast accuracy scenarios.

Abstract [sv]

Solcellen (PV) är en distribuerad förnybar energiteknik som är lämplig att integreras i byggnader. PV minskar elförbrukning och växthusgasutsläpp från byggnader. Överskottet från PV exporteras till elnätet. Detta försämrar inte bara PV:ns ekonomiska prestanda, men skapar också operativa problem i nätet. Effektiva metoder bör därför identifieras för att förbättra PV:ns ekonomiska och miljömässiga prestanda.

Byggnader skiljer sig i hur de är anslutna till energinätet. I byggnader som endast är anslutna till elnätet, kan el-lager, inklusive batteri och vätgaslager, utjämna skillnader mellan produktion och konsumtion. Om det nätanslutna PV-systemet följer den konventionella operationsstrategin, försämras den ekonomiska prestandan med el-lager. I denna avhandling har två nya driftsstrategier utvecklats. Tillsammans med ett utvecklat ramverk för optimering, kan driftsstrategier och lagringskapaciteter optimeras samtidigt. Optimeringsresultaten indikerar att både nuvärdet (NPV) och självförsörjningsgraden (SSR) ökar när el-lager används. Jämförelsen mellan batteri och vätgaslager visar att vätgaslager kan konkurrera med batteri under ett optimistiskt kostnadsscenario för vätgaslagring. Dessutom kan vätgaslagring minska exporterad el-mängd bättre.

I byggnader som är anslutna till elnätet och fjärrvärmenätet kan flera energiomvandlings- och lagringstekniker användas, inklusive värmepumpar, direktverkande el och varmvattentankar. Dessa kan installeras för att bilda ett integrerat energisystem (IES). Genom optimering, kan IES minska kostnaden med 22% och självförbrukningsgraden ökar från 43% till 61%. Dessutom fungerar IES som en ny flexibilitetsåtgärd. Den tillhandahållna flexibilitetsenergin överstiger 36% av elförbrukningen. Under systemplanering erhålls systemkonfiguration och driftskostnad utan övervägande av prognosfel. Genom simulering av systemdrift som inkluderar prognosfel erhålls en korrigerad driftskostnad. Kostnadsskillnaden mellan drift av systemet och systemplanering är mindre än 4% och 6% vid hög och låg prognosprecision.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2019. , p. 56
Series
TRITA-CBH-FOU ; 27
Keywords [en]
Building, PV, Energy Storage, Operation, Optimization, Flexibility
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-250233ISBN: 978-91-7873-193-0 (print)OAI: oai:DiVA.org:kth-250233DiVA, id: diva2:1313606
Public defence
2019-06-04, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2019-05-08

Available from: 2019-05-08 Created: 2019-05-04 Last updated: 2019-05-08Bibliographically approved
List of papers
1. Battery sizing and rule-based operation of grid-connected photovoltaic-battery system: A case study in Sweden
Open this publication in new window or tab >>Battery sizing and rule-based operation of grid-connected photovoltaic-battery system: A case study in Sweden
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2017 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 133, p. 249-263Article in journal (Refereed) Published
Abstract [en]

The optimal components design for grid-connected photovoltaic-battery systems should be determined with consideration of system operation. This study proposes a method to simultaneously optimize the battery capacity and rule-based operation strategy. The investigated photovoltaic-battery system is modeled using single diode photovoltaic model and Improved Shepherd battery model. Three rule-based operation strategies—including the conventional operation strategy, the dynamic price load shifting strategy, and the hybrid operation strategy—are designed and evaluated. The rule-based operation strategies introduce different operation parameters to run the system operation. multi-objective Genetic Algorithm is employed to optimize the decisional variables, including battery capacity and operation parameters, towards maximizing the system's Self Sufficiency Ratio and Net Present Value. The results indicate that employing battery with the conventional operation strategy is not profitable, although it increases Self Sufficiency Ratio. The dynamic price load shifting strategy has similar performance with the conventional operation strategy because the electricity price variation is not large enough. The proposed hybrid operation strategy outperforms other investigated strategies. When the battery capacity is lower than 72 kW h, Self Sufficiency Ratio and Net Present Value increase simultaneously with the battery capacity.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Battery, Genetic algorithm, Operation strategy, Optimization, Photovoltaic
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-201938 (URN)10.1016/j.enconman.2016.11.060 (DOI)000392678900022 ()2-s2.0-85006791741 (Scopus ID)
Note

QC 20170307

Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2019-05-04Bibliographically approved
2. Comparative study of hydrogen storage and battery storage in gridconnected photovoltaic system: Storage sizing and rule-basedoperation
Open this publication in new window or tab >>Comparative study of hydrogen storage and battery storage in gridconnected photovoltaic system: Storage sizing and rule-basedoperation
2017 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118Article in journal (Refereed) In press
Abstract [en]

The paper studies grid-connected photovoltaic (PV)-hydrogen/battery systems. The storage componentcapacities and the rule-based operation strategy parameters are simultaneously optimized by theGenetic Algorithm. Three operation strategies for the hydrogen storage, namely conventional operationstrategy, peak shaving strategy and hybrid operation strategy, are compared under two scenarios basedon the pessimistic and optimistic costs. The results indicate that the hybrid operation strategy, whichcombines the conventional operation strategy and the peak shaving strategy, is advantageous in achievinghigher Net Present Value (NPV) and Self Sufficiency Ratio (SSR). Hydrogen storage is further comparedwith battery storage. Under the pessimistic cost scenario, hydrogen storage results in poorer performancein both SSR and NPV. While under the optimistic cost scenario, hydrogen storage achieves higher NPV.Moreover, when taking into account the grid power fluctuation, hydrogen storage achieves better performancein all three optimization objectives, which are NPV, SSR and GI (Grid Indicator).

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Photovoltaic; Hydrogen storage; Battery storage; Buildings; Operation strategy; Genetic algorithm
National Category
Energy Engineering
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-205206 (URN)10.1016/j.apenergy.2017.03.123 (DOI)000403416300031 ()2-s2.0-85017190863 (Scopus ID)
Note

QC 20170410

Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2019-05-04Bibliographically approved
3. Energy flexibility from the consumer: Integrating local electricity and heat supplies in a building
Open this publication in new window or tab >>Energy flexibility from the consumer: Integrating local electricity and heat supplies in a building
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2018 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 223, p. 430-442Article in journal (Refereed) Published
Abstract [en]

The increasing penetration level of renewable energy requires more flexibility measures to be implemented in future energy systems. Integrating an energy consumer's local energy supplies connects multiple energy networks (i.e., the electrical grid, the district heating network, and gas network) in a decentralized way. Such integration enhances the flexibility of energy systems. In this work, a Swedish office building is investigated as a case study. Different components, including heat pump, electrical heater, battery and hot water storage tank are integrated into the electricity and heat supply system of the building. Special focus is placed on the flexibility that the studied building can provide to the electrical grid (i.e., the building modulates the electricity consumption in response to the grid operator's requirements). The flexibility is described by two metrics including the flexibility hours and the flexibility energy. Optimization of the component capacities and the operation profiles is carried out by using Mixed Integer Linear Programming (MILP). The results show that the system fully relies on electricity for the heat demand when not considering the flexibility requirements of the electrical grid. This suggests that district heating is economically unfavorable compared with using electricity for the heat demand in the studied case. However, when flexibility requirements are added, the system turns to the district heating network for part of the heat demand. The system provides great flexibility to the electrical grid through such integration. The flexibility hours can be over 5200 h in a year, and the flexibility energy reaches more than 15.7 MWh (36% of the yearly electricity consumption). The yearly operation cost of the system slightly increases from 62,273 to 65,178 SEK when the flexibility hours increase from 304 to 5209 h. The results revealed that flexibility can be provided from the district heating network to the electrical grid via the building.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
District heating, Electrical grid, Flexibility, Optimization, Supply integration
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-228712 (URN)10.1016/j.apenergy.2018.04.041 (DOI)000433649900030 ()2-s2.0-85046664444 (Scopus ID)
Funder
EU, Horizon 2020, 646529 and No. 774309
Note

QC 20180530

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2019-05-04Bibliographically approved
4. Planning and Operation of an Integrated Energy System in a Swedish Building
Open this publication in new window or tab >>Planning and Operation of an Integrated Energy System in a Swedish Building
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The increasing capacities of variable renewable energies (VRE) require more flexibility measures. The integration of energy supplies in buildings forms integrated energy systems (IES). IESs can provide flexibility and help increase the VRE penetration level. To upgrade a current building energy system into an IES, several energy conversion and storage components need to be installed. How to decide the component capacities and operate the IES were investigated separately in studies on system planning and system operation. However, a research gap exists that the system configuration from system planning is not validated by real operation conditions in system operation. Meanwhile, studies on system operation assume that the IES configuration is predetermined. This work combines system planning and system operation. The IES configuration is determined by mixed integer linear programming in system planning. Real operation conditions and forecast errors are considered in the system operation. The operation profiles are obtained through different energy management systems. The results indicate that the system configuration from system planning can meet energy demands in real operation conditions. Among different energy management systems, the combination of robust optimization and receding horizon optimization achieves the lowest yearly operation cost. Meanwhile, two scenarios that represent high and low forecast accuracies are employed. Under the high and low forecast accuracy scenarios, the yearly operation costs are about 4% and 6% higher than those obtained from system planning.

Keywords
Building, Integrated Energy System, Planning and Operation, MILP, Robust Optimization
National Category
Engineering and Technology
Research subject
Energy Technology
Identifiers
urn:nbn:se:kth:diva-248394 (URN)
Note

QC 20190610

Available from: 2019-04-07 Created: 2019-04-07 Last updated: 2019-06-10Bibliographically approved

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The full text will be freely available from 2019-12-31 12:46
Available from 2019-12-31 12:46

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