Study on thermo-electric-hydrogen conversion mechanisms and synergistic operation on hydrogen fuel cell and electrochemical battery in energy flexible buildings

Quantification on fuel cell degradation and techno-economic analysis of a hydrogen-based grid-interactive residential energy sharing network with fuel-cell-powered vehicles

A framework to formulate and aggregate performance indicators to quantify building energy flexibility

<p>New Zealand’s energy and electricity system is likely to undergo serious changes with climate change and the decarbonisation of the grid playing a significant role. Research in New Zealand around flexibly managing the electricity grid using buildings has focused on thermoelectric appliances in the residential sector while there has been limited research and quantification of the energy flexibility offered by commercial buildings. Despite this, managing the grid using energy flexible commercial buildings represents an opportunity to achieve meaningful reductions in electricity demand from buildings that are far less numerous than residential buildings. The aim of this thesis was to establish whether energy flexible commercial buildings in New Zealand can maintain the current quality of indoor thermal comfort and achieve reductions in demand that are sufficiently large that grid operators consider them significant contributors to grid management. By understanding the contribution, we can understand whether energy flexible commercial buildings are worth further investigation. In this thesis, energy flexibility means the ability for a building to manage its demand and generation according to user needs, grid needs, and local climate conditions. Energy flexibility in commercial buildings could then support the integration of more variable renewable energy sources and increase demand response capability which is a cost-effective way to manage network constraints and reduce non-renewable electricity generation. Case studies of New Zealand commercial buildings represented as Building Energy Models (BEMs) were simulated under energy flexible operation in a building performance simulation software (EnergyPlus). The selected case studies were small commercial buildings less than 1,499m² in size and which all contained heat pumps. The buildings were of office, retail, and mixed-use types. Two simple energy flexibility strategies were simulated in the buildings and the results from each building were then aggregated and extrapolated across the New Zealand commercial building stock. The strategies simply shifted and shed heating electricity demand. This was done to test whether implementing basic energy flexibility strategies have the potential to reduce electricity demand by a meaningful magnitude. At best the commercial building stock’s peak demand could reduce by 177MW by energy flexibly operating 45% of the commercial building stock, this was equivalent to around 11,700 buildings. In this scenario heating was shifted to start 150 minutes earlier in the morning. The study concluded that there is energy flexibility potential in New Zealand commercial buildings that results in demand reductions sufficiently large enough for grid operators to consider significant for grid management. This could be achieved without seriously jeopardising the current quality of indoor thermal comfort and warrants further investigation into energy flexible commercial buildings. This thesis also presented a refined methodology and energy modelling practice that could be used by other researchers to model and evaluate energy flexible buildings without the need to recreate the same methodology.</p>

<p>New Zealand’s energy and electricity system is likely to undergo serious changes with climate change and the decarbonisation of the grid playing a significant role. Research in New Zealand around flexibly managing the electricity grid using buildings has focused on thermoelectric appliances in the residential sector while there has been limited research and quantification of the energy flexibility offered by commercial buildings. Despite this, managing the grid using energy flexible commercial buildings represents an opportunity to achieve meaningful reductions in electricity demand from buildings that are far less numerous than residential buildings. The aim of this thesis was to establish whether energy flexible commercial buildings in New Zealand can maintain the current quality of indoor thermal comfort and achieve reductions in demand that are sufficiently large that grid operators consider them significant contributors to grid management. By understanding the contribution, we can understand whether energy flexible commercial buildings are worth further investigation. In this thesis, energy flexibility means the ability for a building to manage its demand and generation according to user needs, grid needs, and local climate conditions. Energy flexibility in commercial buildings could then support the integration of more variable renewable energy sources and increase demand response capability which is a cost-effective way to manage network constraints and reduce non-renewable electricity generation. Case studies of New Zealand commercial buildings represented as Building Energy Models (BEMs) were simulated under energy flexible operation in a building performance simulation software (EnergyPlus). The selected case studies were small commercial buildings less than 1,499m² in size and which all contained heat pumps. The buildings were of office, retail, and mixed-use types. Two simple energy flexibility strategies were simulated in the buildings and the results from each building were then aggregated and extrapolated across the New Zealand commercial building stock. The strategies simply shifted and shed heating electricity demand. This was done to test whether implementing basic energy flexibility strategies have the potential to reduce electricity demand by a meaningful magnitude. At best the commercial building stock’s peak demand could reduce by 177MW by energy flexibly operating 45% of the commercial building stock, this was equivalent to around 11,700 buildings. In this scenario heating was shifted to start 150 minutes earlier in the morning. The study concluded that there is energy flexibility potential in New Zealand commercial buildings that results in demand reductions sufficiently large enough for grid operators to consider significant for grid management. This could be achieved without seriously jeopardising the current quality of indoor thermal comfort and warrants further investigation into energy flexible commercial buildings. This thesis also presented a refined methodology and energy modelling practice that could be used by other researchers to model and evaluate energy flexible buildings without the need to recreate the same methodology.</p>

• EFOnt, a semantic ontology for building energy flexibility applications, is introduced. • EFOnt is designed to work with other building energy data tools as part of an ecosystem • EFOnt standardizes energy flexibility definition, characterization, and quantification. • One measurement-based and one simulation-based use case of EFOnt are given. • The future development and potential use cases of EFOnt are discussed. Energy flexibility of buildings can be an essential resource for a sustainable and reliable power grid with the growing variable renewable energy shares and the trend to electrify and decarbonize buildings. Traditional demand-side management technologies, advanced building controls, and emerging distributed energy resources (including electric vehicle, energy storage, and on-site power generation) enable the transition of the building stock to grid-interactive efficient buildings (GEBs) that operate efficiently to meet service needs and are responsive to grid pricing or carbon signals to achieve energy and carbon neutrality. Although energy flexibility has received growing attention from industry and the research community, there remains a lack of common ground for energy flexibility terminologies, characterization, and quantification methods. This paper presents a semantic ontology—EFOnt (Energy Flexibility Ontology)—that extends existing terminologies, ontologies, and schemas for building energy flexibility applications. EFOnt aims to serve as a standardized tool for knowledge co-development and streamlining energy flexibility related applications. We demonstrate potential use cases of EFOnt via two examples: ( 1 ) energy flexibility analytics with measured data from a residential smart thermostat dataset and a commercial building, and ( 2 ) modeling and simulation to evaluate energy flexibility of buildings. The compatibility of EFOnt with existing ontologies and the outlook of EFOnt's role in the building energy data tool ecosystem are discussed.

Building energy flexibility plays a critical role in demand-side management for reducing utility costs for building owners and sustainable, reliable, and smart grids. Realizing building energy flexibility in tropical regions requires solar photovoltaics and energy storage systems. However, quantifying the energy flexibility of buildings utilizing such technologies in tropical regions has yet to be explored, and a robust control sequence is needed for this scenario. Hence, this work presents a case study to evaluate the building energy flexibility controls and operations of a net-zero energy office building in Singapore. The case study utilizes a data-driven energy flexibility quantification workflow and employs a novel data-driven model predictive control (MPC) framework based on the physically consistent neural network (PCNN) model to optimize the building energy flexibility. To the best of our knowledge, this is the first instance that PCNN is applied to a mathematical MPC setting, and the stability of the system is formally proved. Three scenarios are evaluated and compared: the default regulated flat tariff, a real-time pricing mechanism, and an on-site battery energy storage system (BESS). Our findings indicate that incorporating real-time pricing into the MPC framework could be more beneficial to leverage building energy flexibility for control decisions than the flat-rate approach. Moreover, adding BESS to the on-site PV generation improved the building self-sufficiency and the PV self-consumption by 17% and 20%, respectively. This integration also addresses model mismatch issues within the MPC framework, thus ensuring a more reliable local energy supply. Future research can leverage the proposed PCNN-MPC framework for different data-driven energy flexibility quantification types.

Chapter 2 - Building energy flexibility: definitions, sources, indicators, and quantification methods

• Studies on energy flexibility of residential buildings have been reviewed. • Energy flexibility technologies by types, purposes, and scopes are summarized. • Modeling techniques, tools, and characterization of flexible resources are presented. • Quantification methods and metrics of energy flexibility are analyzed. • Research trends, open questions, and future research opportunities are identified. With building electric demand becoming increasingly dynamic, and a growing percentage of intermittent renewable power generation from solar photovoltaics and wind turbines, the power grid is facing increasing challenge to manage the real time balance between the supply and demand. With advancements in smart sensing and metering, smart appliances, electric vehicles, and energy storage technologies, demand side management of residential buildings can help the grid to improve stability by optimizing flexible loads. This paper reviews recent studies on residential building demand side management, with a focus on characterization and quantification of energy flexibility covering various types of flexible loads, metrics, methods, and applications. The reviewed studies showed four levels of applications: building level (45%), district or community level (29%), system level (19%), and building sector level (7%). Shifting loads is the dominant flexibility type in 60% of applications, followed by shedding (19%), generation (16%), and modulating (6%). Depending on the technology and application scope, flexible operations have a wide range of performance, with peak power reductions of 1%~65%, energy savings up to 60%, operational cost reduction of 1%~48%, and greenhouse gas emission reductions of up to29%. More than half (51%) of the studies employed control strategies to achieve flexibility; among those 72% used optimal controls, while 28% used rule-based controls. About 58% of the studies used mathematical formulation to quantify energy flexibility. Most studies were based on simulation, while less than 15% of the studies had measurements from experiments or field tests. The review reveals research opportunities to address significant gaps in the existing literature: (1) establishing a common definition and performance metrics for energy flexibility of buildings that are technology and application agnostic, (2) developing an ontology to standardize representation of flexibility resources for interoperability, (3) integrating occupant impacts into the quantification and optimization of energy flexibility, and (4) developing requirements and credits of energy flexibility in building energy codes and standards. Findings from the review can inform future research and development of energy flexible buildings which are essential to a reliable and resilient power grid.

Energy flexibility quantification of grid-responsive buildings: Energy flexibility index and assessment of their effectiveness for applications

Occupant behaviour has a substantial impact on the prediction of building energy performance. To capture this impact, co-simulation is considered an effective approach. It is still a new method in need of more development. In this study, a co-simulation framework is established to couple EnergyPlus with Java via Functional Mock-up Interface (FMI) using the EnergyPlusToFMU software package. This method is applied to a case study of a single occupant office with control of lighting, plug load and thermostat. Two control scenarios are studied. These are occupancy and occupant behaviour based control (OC), and sensor based control (SBC) triggered by dynamic electricity price under demand side management (DSM) program. The building energy performance in the OC scenario is then used as reference to evaluate the building energy (cost) saving and energy flexibility. This is an improvement of current studies on DSM and building energy flexibility, in which predefined user schedules are commonly used.

Building automation enables the possibility of energy flexibility in buildings. To investigate the motivation and barriers for the energy flexibility in buildings, this study develops a conceptual framework of the readiness for energy flexible buildings by conducting interviews with building automation suppliers, electricity supplier, district heating supplier, distribution system operator, energy service companies, experts in energy and buildings, building managers, and occupants. The two main parts of the framework are building preparation, grid and market conditions following the impacts of regulation and policies, stakeholder collaboration and integrated building automation. A case study of campus buildings is conducted to demonstrate the framework. The result of the case study shows that the main barriers for buildings to provide energy flexibility are 1) many buildings are too old and need to be refurbished, 2) the benefit of providing energy flexibility to the grid is not sufficient, 3) building management systems need to be either installed or upgraded to response to the demand from the grid. Building managers believe that buildings can provide energy flexibility by building automation and distributed energy resources, but they consider energy efficiency to be more important than providing flexibility to the grid. Meanwhile, occupants have different opinions regarding the comfort level of indoor air quality and control, and the differences are based on various factors, e.g. location, room type, and building ages.

Energy flexible buildings: An evaluation of definitions and quantification methodologies applied to thermal storage

Demand side energy flexibility is increasingly being viewed as an essential enabler for the swift transition to a low-carbon energy system that displaces conventional fossil fuels with renewable energy sources while maintaining, if not improving, the operation of the energy system. Building energy flexibility may address several challenges facing energy systems and electricity consumers as society transitions to a low-carbon energy system characterized by distributed and intermittent energy resources. For example, by changing the timing and amount of building energy consumption through advanced building technologies, electricity demand and supply balance can be improved to enable greater integration of variable renewable energy. Although the benefits of utilizing energy flexibility from the built environment are generally recognized, solutions that reflect diversity in building stocks, customer behavior, and market rules and regulations need to be developed for successful implementation. In this paper, we pose and answer ten questions covering technological, social, commercial, and regulatory aspects to enable the utilization of energy flexibility of buildings in practice. In particular, we provide a critical overview of techniques and methods for quantifying and harnessing energy flexibility. We discuss the concepts of resilience and multi-carrier energy systems and their relation to energy flexibility. We argue the importance of balancing stakeholder engagement and technology deployment. Finally, we highlight the crucial roles of standardization, regulation, and policy in advancing the deployment of energy flexible buildings. • Energy flexibility characterization methodologies are needed at the aggregated level. • There is a trend toward decentralized and distributed architectures to harness energy flexibility. • Buildings with/within multicarrier energy systems offer higher levels of flexibility. • Multidisciplinary approaches are needed to address various aspects of the topic. • Supportive policies are key to enable opportunities and incentivize stakeholders.

Chapter 3 - Building energy flexibility: modeling and optimization

Retail buildings has an important role for demand side energy flexibility because of their high energy consumption, variety of energy flexibility resources, and centralized control via building control systems. Energy flexibility requires agreements and collaborations among different actors. However, the stakeholders' reaction to energy flexibility have not been fully investigated. Therefore, this paper aims to investigate the stakeholder involvement in energy flexibility by applying the business ecosystem concept (including actors, relationships, value alliances, and influential factors), with the discussion of the stakeholders' roles and their interrelation in delivering energy flexibility with the influential factors to the actual implementation of energy flexible operation of their buildings. Based on a literature analysis, the results cover stakeholders' types and roles, perceptions (drivers, barriers, and benefits), energy management activities and technology adoptions, and the stakeholders' interaction for the energy flexibility in retail buildings.