Energy Scheduling and Flexibility Quantification in Buildings

The eleven papers in this special section focus on new trends in residential and home energy management. As an important branch of power demand side management, residential energy management plays an important role in reducing the emission and enhancing the energy efficiency in the energy delivery side. Recent technical advances bring significant transformations to energy end-users. First, increasing penetrations of residential renewable energy source, electric vehicle, and residential energy storage system have been transforming residential energy consumers to be “Energy Prosumers (Producer and Consumer. Second, the two-way communication infrastructure enables residential energy entities interact and exchange information flows with the external environment. Third, recent advances in ubiquitous sensing and metering technologies, such as Internet of Things, nonintrusive load monitoring, and advanced metering infrastructure, enable the deep understanding on behaviors of energy end-users and related environments. These technical advances consequently drive residential energy entities to become complex cyber-physical-social systems, which require newsolutions for coordinating, managing, and optimizing residential energy resources with the active participations of end users.

Traditional power system operations rely on controllable fossil fuel-based generators to meet unanticipated changes in electricity demand and contingencies. However, high penetration of Renewable Energy Sources (RES), especially solar and wind, increases randomness in the netload. This intermittency leads to inaccurate netload prediction and loadgeneration imbalances. Power systems with a high share ofRES require additional operational flexibility to cope with supplydemand mismatches. While flexibility can be enhanced using various measures, system operators need to quantify its requirements and availability in the system to ensure smooth real-time operations. Recent literature presents various methods for flexibility quantification. To consolidate various works presented in the domain, this paper presents a detailed literature review on flexibility quantification methods. Based on the mathematical formulation, the literature is classified into 1) Deterministic and 2) Probabilistic approaches. Further, the work highlights the challenges of each quantification method. Finally, this paper highlights the impact of flexible resource failure on power system operations and emphasizes the need to consider reliability of resources in the quantification methods.

Existing grids have been designed with traditional large centralized generation in mind; however, with the ever-increasing utilization of renewable distributed energy resources, the challenges of proper grid management have intensified. Demand-side energy flexibility is seen as one potential way to alleviate these challenges. Presently, residential demand-side energy flexibility has remained a largely untapped resource since individual prosumers are too small to provide enough capacity, thus necessitating the need for an aggregator. In view of the aforementioned, this paper conducts a literature review on the aggregated residential demand-side energy flexibility. The paper gives an overview of characterization methods of energy flexibility. The sources of residential energy flexibility are identified and categorized based on their flexibility characteristics. In addition, the quantification methods and parameters of energy flexibility are analyzed. Moreover, the forecasting methods of energy flexibility in the context of different flexibility sources are outlined. Additionally, an overview of existing markets and potential new emerging flexibility markets is given. The challenges and barriers faced by the aggregators attempting to enter flexibility markets are examined. Finally, the paper is concluded by providing a discussion of the key findings that summarize the current research directions and highlight the gaps for future development of aggregated energy flexibility.

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

It is expected to install a large amount of generation from renewable energy sources such as wind power generation and photovoltaic generation into power systems. However, a large penetration of such renewable energy sources causes some problems in power systems, e.g. frequency fluctuation. In this paper, a number of Heat Pump Water Heaters (HPWHs), one of the energy efficient-use customers' appliances and Battery Energy Storage System (BESS) are considered as controllable equipment for frequency control. An HPWH is considered as a controllable load because the power consumption can be changed during water heating as long as the heating is finished when the customer would like to use. This paper proposes an effective control of HPWHs installed in the power system with a large penetration of renewable energy sources on the assumption of a two-way communication network. The control period is determined based on the statistical information of the HPWHs.

Optimization of a wind powered desalination and pumped hydro storage system

Characterizing energy flexibility of buildings with electric vehicles and shiftable appliances on single building level and aggregated level

Generic characterization method for energy flexibility: Applied to structural thermal storage in residential buildings

Flexibility can be defined as the power system's ability to respond to both expected and unexpected changes, either in demand or on the supply side. This concept contributes to improving the grid's stability allowing a higher penetration of renewable energy sources (RESs). A real-time flexibility utilization system can be viewed as a cyber-physical system where the communication component is cyber, whereas the control components have physical effects. In this chapter, we discuss security properties and challenges that must be considered in the flexibility utilization of energy districts.

Energy storage system (ESS) plays a prominent role in renewable energy (RE) to overcome the intermittent of RE energy condition and improve energy utilization in the power system. However, ESS for residential applications requires specific and different configuration. Hence, this review paper aims to provide information for system builders to decide the best setup configuration of ESS for residential application. In this paper, the aim is to provide an insight into the critical elements of the energy storage technology for residential application. The update on ESS technology, battery chemistry, battery charging, and monitoring system and power inverter technology are reviewed. Then, the operation, the pro, and cons of each variant of these technologies are comprehensively studied. This paper suggested that the ESS for residential ESS requires NMC battery chemistry because it delivers an all-rounded performance as compared to other battery chemistries. The four-stages constant current (FCC) charging technique is recommended because of the fast charging capability and safer than other charging techniques reviewed. Next, the battery management system (BMS) is recommended to adapt in advance machine learning method to estimate the state of charge (SOC), state of health (SOH) and internal temperature (IT) to increase the safety and prolong the lifespan of the batteries. Finally, these recommendations and solutions aimed to improve the utilization of RE energy in power system, especially in residential ESS application and offer the best option that is available on the shelf for the residential ESS application in the future.

Flexibility quantification and enhancement of flexible electric energy systems in buildings

In recent years, the penetration of Renewable energy sources (RES) has increased considerably in power systems. Besides, fossil fuel vehicles are gradually replaced with electric ones. Increasing the penetration of RES on the supply side and the penetration of Plug-in electric vehicles (PEVs) on the demand side, intermittency of the power system increases. This paper proposes a novel structure for Virtual storage plants (VSP) to integrate the storage potentials of the PEVs into power systems. The suggested VSP is comprised of smart charging stations, Parking lot aggregator (PLA), Local service provider (LSP), and Global service provider (GSP). The PLA coordinates the charging/discharging strategies of the PEVs based on the flexibility requirements of the supply side. The LSP aims to mitigate congestion in weak lines of the power network. The GSP provides up-/down-regulation for the wholesale electricity market when a power shortage/excess occurs in the power systems. On the supply side, the electricity market is comprised of three trading floors, including the day-ahead, intraday, and balancing markets. The VSP integrates the storage potentials of the PEVs to the three market floors hierarchically on long, mid, and short advance notices. The electricity price data are extracted from the Danish electricity market. The suggested approach is examined on the IEEE 14-bus system. The results show that the suggested VSP provides local and global energy security for the power system during critical hours.

In this paper, the power system with penetration of renewable energy sources is represented as a multi-machine interconnected system. The power system comprises of conventional synchronous generators and renewable energy sources via rectifier-inverters. A novel controller has been proposed for the inverter that connects the renewable source to the grid while each conventional synchronous generator is equipped with an automatic voltage regulator (AVR) that can be accompanied by a power system stabilizer (PSS). The proposed inverter controller utilizes a dynamically varying gain such that the dynamics of the renewable power source is similar to that of the conventional synchronous generators. Subsequently, stability of the power system is achieved by employing a conventional damping controller. Simulation results on the IEEE 14-bus power system with the proposed renewable energy source controller are provided to show the effectiveness of the approach in damping oscillations that occur after disturbances are removed. The end result is a feedback controller that makes possible for power systems with penetration of renewable energy sources the application of conventional multi-machine stabilizing techniques such as PSS.

When considering issues such as power shortage, environmental pollution, and dependence on petroleum, a battery energy storage system (ESS) is one of the promising options to overcome these problems. This paper deals with a 3 kW residential battery ESS that consists of a buck/boost power conversion unit, a DC/AC bidirectional conversion unit, and a Li-ion battery pack with a battery management system. In order to connect an ESS to the grid, the system needs to meet requirements such as having a bidirectional power flow, low THD, and anti-islanding. This paper presents an operation scheme and the implementation of a residential ESS. The scheme was experimentally verified on a prototype.

The operations of electricity and natural gas transmission networks in the U.S. are increasingly interdependent, due to the growing number of installations of gas fired generators and the penetration of renewable energy sources. This development suggests the need for closer communication and coordination between gas and power transmission system operators in order to improve the efficiency and reliability of the combined energy system. In this paper, we present a co-simulation platform for examining the interdependence between natural gas and electricity transmission networks based on a direct current unit-commitment and economic dispatch model for the power system and a transient hydraulic gas model for the gas system. We analyze the value of day-ahead coordination of power and natural gas network operations and show the importance of considering gas system constraints when analyzing power systems operation with high penetration of gas generators and renewable energy sources. Results show that day-ahead coordination contributes to a reduction in curtailed gas during high stress periods (e.g., large gas offtake ramps) and a reduction in energy consumption of gas compressor stations.