Data-driven key performance indicators and datasets for building energy flexibility: A review and perspectives

• 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.

Chapter 11 - Energy flexibility in grid-interactive and net/nearly zero energy buildings

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

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.

This research explores socio-technical perspectives of the demand-side management strategy of using the built environment for short term thermal energy storage. Here conceptualised as a niche innovation within the Danish socio-technical district heating landscapes, the research explores potentials and limitations of this building energy flexibility strategy from the perspective of district heating sector professionals, actors at the centre of the low-carbon energy transitions. Results of the mixed-methods abductive research enquiry suggest that this energy flexibility strategy facilitates (I) solving local network congestion challenges in smaller parts of existing networks and (II) reduces needed network capacity in new heat supply areas. Sector professionals assess this (III) energy flexibility strategy as most practicable in large-scale/commercial buildings and industries. Challenges include hardware balancing, service and maintenance, and the sometimes counterproductive incentive structures among stakeholders involved. Research evidence suggests that business models appealing to environmental values and priorities may incentivise sustainable heat-use behaviours more than economic benefit alone among some groups of end users. Building energy flexibility and demand-side management strategies may become integral to future ‘smart’ energy systems throughout the world. However, their successful implementation necessitates understanding the local socio-technical dynamics involved. Multidisciplinary research approaches as the one taken here facilitate these necessary insights.

<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>

Improving energy flexibility of a net-zero energy house using a solar-assisted air conditioning system with thermal energy storage and demand-side management

Investigation of design strategies and quantification of energy flexibility in buildings: A case-study in southern Italy

Optimal storage capacity for building photovoltaic-energy storage systems considering energy flexibility management

Conventional key performance indicators (KPI) assessed in building simulation lack specific measures of how the building interacts with the grid and its energy flexibility. This paper aims to provide an overview of specific energy flexibility performance indicators, together with supporting control strategies. If applied correctly, the indicators help improving the building performance in terms of energy flexibility and can enable minimization of operational energy costs. Price-based load shifting, self-generation and self-consumption are among the most commonly used performance indicators that quantify energy flexibility and grid interaction. It has been found that the majority of performance indicators, specific to energy flexibility, are combined with rule-based control. Only a limited amount of specific energy flexibility KPIs are used in combination with optimal control or model predictive control. Both of these advanced control approaches often have a couple of economic or comfort objectives that do not take into account an energy flexibility KPI. There is evidence that recent model predictive control approaches incorporate some aspects of building energy flexibility to minimize operational cost in conjunction with time varying pricing.

• 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.

Empirical exploration of zone-by-zone energy flexibility: A non-intrusive load disaggregation approach for commercial buildings

Electricity peak shaving for commercial buildings using machine learning and vehicle to building (V2B) system

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