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Planning and Operation of an Integrated Energy System in a Swedish Building
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
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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 [en]
Building, Integrated Energy System, Planning and Operation, MILP, Robust Optimization
National Category
Engineering and Technology
Research subject
Energy Technology
Identifiers
URN: urn:nbn:se:kth:diva-248394OAI: oai:DiVA.org:kth-248394DiVA, id: diva2:1302877
Note

QC 20190610

Available from: 2019-04-07 Created: 2019-04-07 Last updated: 2019-06-10Bibliographically approved
In thesis
1. Integration of Distributed Renewable Energy and Energy Storages in Buildings
Open this publication in new window or tab >>Integration of Distributed Renewable Energy and Energy Storages in Buildings
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
Building, PV, Energy Storage, Operation, Optimization, Flexibility
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-250233 (URN)978-91-7873-193-0 (ISBN)
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

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