Grid Energy Systems Research Articles

Optimized design and control of an off grid solar PV/hydrogen fuel cell power system for green buildings

Modelling, simulation, optimization and control strategies are used in this study to design a stand-alone solar PV/Fuel Cell/Battery/Generator hybrid power system to serve the electrical load of a commercial building. The main objective is to design an off grid energy system to meet the desired electric load of the commercial building with high renewable fraction, low emissions and low cost of energy. The goal is to manage the energy consumption of the building, reduce the associate cost and to switch from grid-tied fossil fuel power system to an off grid renewable and cleaner power system. Energy audit was performed in this study to determine the energy consumption of the building. Hourly simulations, modelling and optimization were performed to determine the performance and cost of the hybrid power configurations using different control strategies. The results show that the hybrid off grid solar PV/Fuel Cell/Generator/Battery/Inverter power system offers the best performance for the tested system architectures. From the total energy generated from the off grid hybrid power system, 73% is produced from the solar PV, 24% from the fuel cell and 3% from the backup Diesel generator. The produced power is used to meet all the AC load of the building without power shortage (<0.1%). The hybrid power system produces 18.2% excess power that can be used to serve the thermal load of the building. The proposed hybrid power system is sustainable, economically viable and environmentally friendly: High renewable fraction (66.1%), low levelized cost of energy (92 $/MWh), and low carbon dioxide emissions (24 kg CO2/MWh) are achieved.

Connecting the Last Mile: Demand Response in Smart Buildings

Demand response (DR) operates on the last mile in the smart grid that connects the building energy system with utility grid. It enables a building to actively participate in the whole grid energy system. With DR, a building may make a profit by optimizing its energy consumption while helping to achieve the overall targets of energy efficiency and emission reduction for the whole energy system. The recent US Supreme Court ruling on FERC Order 745 has reaffirmed the critical role and functions of demand response. It is expected that demand response will soon become a basic function of smart buildings. In this paper, we summarize the background of demand response, investigate promising automation technology such as OpenADR for demand response applications in smart buildings, and present an OpenADR Interface prototype demonstration for building energy management systems. We demonstrate the realization and benefits of OpenADR integration with state of art building energy management systems, which connects the last mile between the smart grids with the smart buildings.

Feasibility study for power generation using off- grid energy system from micro hydro-PV-diesel generator-battery for rural area of Ethiopia: The case of Melkey Hera village, Western Ethiopia

Electricity supply in Ethiopia is extremely antiquated. Most of the remote rural areas of Ethiopia are not yet electrified. Electrifying these remote areas by extending grid system is difficult and costly. Melkey Hera village is one of a rural community situated in western Ethiopia. In this village, extension of the grid is not yet practical. As the current international trend in rural electrification is to utilize renewable energy resources; solar, wind, biomass, and micro hydro power systems can be seen as alternatives. Therefore, the target of this paper is to investigate the viability of a micro hydro, Photo Voltaic (PV) and Diesel Generator-battery hybrid power system options to come up with the best techno-economic and optimum configuration for supplying electricity to this village. The study was performed by an assessment of the predicted village energy demand, the available renewable energy resources, and then using the software called HOMER. The best hybrid system type was described and the optimization of the system configuration was also done. Furthermore, through the simulation of different configuration of the supply system, the optimal mini-grid hybrid system design was established to combine hydro, solar PV, battery energy storage and diesel generator. This system demonstrated to be more reliable in operation, and the most cost-effective for the required level of service. The role of energy storage in system operation also demonstrated to offer additional operational advantages in-terms of reliability and cost savings. Overall, the design results show that the majority of energy obtained from hydropower, which accounts 79%, the PV module covers 20%, and diesel generator is only 1% of the total load consumption. The obtained hybrid system is cost competitive with $\$$0.133/kWh, which is somewhat good to satisfy the community needs. However, this is more than current energy price in Ethiopia which $\$$0.06/kWh. If due-merit given to the electricity deficiency of the country, it would play major role in improvement of life quality of community living in rural areas. From environmental standpoint, the renewable fraction of the project is 99%, which shows the system is environmentally friendly. Finally, this study identified that off grid hybrid micro hydro-PV-DG-battery bank energy system is cost effective and environmentally friendly in delivering power for rural areas far from the grid. Moreover, the study provides valuable information to the government and Non-government organization (NGO) about the renewable energy potential of the country for a rural electrification project in Ethiopia.

Refrigerated warehouses as intelligent hubs to integrate renewable energy in industrial food refrigeration and to enhance power grid sustainability

BackgroundIndependence from fossil fuels, energy diversification, decarbonisation and energy efficiency are key prerequisites to make a national, regional or continental economy competitive in the global marketplace. As Europe is about to generate 20% of its energy demand from Renewable Energy Sources (RES) by 2020, adequate RES integration and renewable energy storage throughout the entire food cold chain must properly be addressed. Scope and approachRefrigerated warehouses for chilled and frozen foods are large energy consumers and account for a significant portion of the global energy demand. Nevertheless, the opportunity for RES integration in the energy supply of large food storage facilities is often neglected. In situ power generation using RES permits capture of a large portion of virtually free energy, thereby reducing dramatically the running costs and carbon footprint, while enhancing the economic competitiveness. In that context, there exist promising engineering solutions to exploit various renewables in the food preservation sector, in combination with the emerging sustainability-enhancing technology of Cryogenic Energy Storage (CES). Key findings and conclusionsSubstantial research endeavours are driven by the noble objective to turn the Europe's Energy Union into the world's number one in renewable energies. Integrating RES, in synchrony with CES development and proper control, is capable of both strengthening the food refrigeration sector and improving dramatically the power grid balance and energy system sustainability. Hence, this article aims to familiarise stakeholders of the European and global food preservation industry with state-of-the-art knowledge, know-how, opportunities and professional achievements in the concerned field.

(Invited) Solution-Processable Li and Na Superionic Conductors for All-Solid-State Batteries

Recently, rechargeable batteries have been emerging as the key to large-scale energy storage devices. For electric vehicles (EVs), lithium-ion batteries (LIBs) are considered to be the most competitive because of their high operating voltage and light weight of electrode materials. For larger-scale applications than electric vehicles, energy grid or energy storage systems, the use of Na rather than Li may be more reasonable to satisfy the requirements of cost and environmental effects. This has leaded to the explosive research efforts on Na-ion batteries (NIBs). The success of LIBs and the promising results for NIBs are primarily indebted to development of novel electrode materials. However, their operation becomes possible by employment of liquid electrolytes in which the charge carriers, Li or Na ions, can move between negative and positive electrodes. Due to the high operating voltages of LIBs and NIBs, the electrolytes for them are based on organic liquid solvents. However, their intrinsic properties give rise to serious safety concerns such as flammability and leakage. Development of all-solid-state batteries employing inorganic solid electrolytes (SEs) is an ultimate solution to tackle the safety issues.1 Thin film all-solid-state lithium batteries (ASLBs) based on LiPON as SE is commercially available type of batteries, and exhibit excellent electrochemical performances. However, they are not suitable for large-scale applications for EVs or energy storage systems due to the high fabrication cost. In contrast, bulk-type all-solid-state batteries in which particulate mixtures of active materials, SEs, and conductive additives may compete with the LIBs because the powder-based manufacturing process similar to that for LIBs might be adaptable.1 To date, promising electrochemical performances of bulk-type ASLBs have been demonstrated by the use of state-of-the-art sulfide SE materials. The sulfide SE show not only extremely high conductivities which is comparable to that for liquid electrolytes but also excellent deformability which makes it possible to achieve two-dimensional contacts with active materials by pressing at room temperature. Despite the intrinsically good deformability of sulfide SEs, achieving full surface coverage of SEs on active materials has been hindered by restriction of synthesis protocols for SEs.2,3 A proof-of-concept that direct coating of SEs on active materials can effectively enhance the electrochemical performance of bulk-type ASLBs was demonstrated by using laser vapor deposition.4 The next step inspired by this approach should be developments of commercially meaningful protocols for SE coating. In this context, solution-process of SEs is of prime importance. However, only a few works on the wet chemistry of SEs, overlooking the possibility of its application to the SE coating, has been reported so far. This might be because of unavailability of solvents, considering the severe reactivity of sulfide materials with common solvents.3 By the aforementioned backgrounds, recently our group have succeeded to develop new, highly conductive (>10-4 S cm-1) Li-ion and Na-ion conductive solid electrolytes by scalable solution process using cheap and environmentally-benign solvents.5 The solution-process was directly applied for the SE-coating on active materials for ASLBs and ASNBs, demonstrating its excellence in enhancement of electrochemical performances. In this presentation, our recent results on solution-processable Li- and Na-ion SEs and their applications to all-solid-state Li- and Na-ion batteries will be presented. References Y. S. Jung, D. Y. Oh, Y. J. Nam, K. H. Park, Israel J. Chem. 55, 472 (2015).Y. J. Nam, S. J. Jo, D. Y. Oh, J. M. Im, S. Y. Kim, J. H. Song, Y. G. Lee, S. Y. Lee, Y. S. Jung, Y. S. Nano Lett. 15, 3317 (2015).D. Y. Oh, Y. J. Nam, K. H. Park, S. H. Jung, S.-J. Cho, Y. K. Cho, Y.-G. Lee, S.-Y. Lee, Y. S. Jung, Adv. Energy Mater. 5, 1500865 (2015).A. Sakuda, A. Hayashi, T. Ohtomo, S. Hama, M. Tatsumisago, Electrochem. Solid-State Lett. 13, A73 (2010).K. H. Park, D. Y. Oh, Y. E. Choi, Y. J. Nam, L. Han, J.-Y. Kim, H. Xin, F. Lin, S. M. Oh, Y. S. Jung, Adv. Mater. 28, 1874 (2016).

A study on data visualization of embedded sensors for building energy monitoring using BIM

In recent years, building energy consumption has increased in response to climate change, resulting in a worldwide reduction of energy efficiency. A strong response is required, through both the enhancement of building energy efficiency and the reduction of power usage. These objectives could be achieved by pursuing “Blackout” prevention, through developing a control unit such as that of the urban energy grid system that was used in the Energy Operation Center (EOC) for smart cities. In this context, this paper presents an optimization operation technique for Building Energy Management Systems (BEMS), using control monitor-based Building Information Modeling (BIM) for the efficient operation of the EOC. BIM is one of the approaches that can be used for the visual representation, management, and exchange of information on all aspects of a building. The EOC should be able to efficiently represent the data from the building information, and the operator maintaining it should be able to promptly acquire the data for handling it. This suggests that the control of energy consumption by a Building Automation System (BAS) to maximize building energy efficiency will lead to improved total energy performance, reduced operating costs, and reduced environmental impact.

Study of Aqueous Zinc Nickel Flow Battery with High Energy Density

The escalation of power system promotes the development of battery technologies with its huge application market. Redox flow batteries (RFBs) are very attractive to customers in the energy grid system, and their noticeable technological innovations in the past decades have driven them to gradually replace the conventional energy storage methods under certain circumstance. Portable batteries used in electronics and fully electric vehicles ought to be designed to fulfill the growing desires on supplying energy quicker and longer. Therefore, many significant improvements have been achieved on battery manufacture and mechanism optimization. Here, the first fully-flow-able zinc–nickel flow battery (ZNFB) is studied, whose performance is supposed to be suitable for various scales. Through using semi-solid fuel cell (SSFC) technology, we incorporate the beneficial features of aqueous Zn/Ni chemistry (essentially sustainable, eco-friendly and deposit-abundant) into RFB structure to make a “hybrid” flow battery system with nano-size carbon network. Basic electrochemical properties of ZNFB are reported, and its suspension and electrode characters have been studied and improved.

Copper-alloyed spinel black oxides and tandem-structured solar absorbing layers for high-temperature concentrating solar power systems

Although renewable solar power plants are rapidly proliferating, high cost and the intermittent availability of solar power are still significant barriers for its penetration into the energy grid system. Concentrating solar power (CSP) offers an attractive alternative due to its integration with cost-effective thermal energy storage systems. To further reduce the cost of CSP, it is imperative to operate the plants at higher temperatures for enhanced efficiency. One of the key components for next-generation high-temperature CSP is the solar absorbing coating materials. In this work, we have developed tandem-structured solar absorbing layers with CuFeMnO4 and CuCr2O4 black oxide nanoparticles (NPs). These tandem structures exhibited a remarkably high solar-to-thermal conversion efficiency, or figure of merit (FOM), of 0.903, under the condition of 750°C operating temperature and a solar concentration ratio of 1000. More importantly, the coating showed unprecedented durability, as demonstrated from long-term isothermal annealing at 750°C in air as well as rapid thermal cycling between room temperature and 750°C. Our results suggest that the tandem black oxide coating is suitable to meet the stringent demand of next-generation high-temperature CSP systems. The coating materials synthesis, structures, optical as well as thermal properties will be discussed.

Increasing Social Awareness of Consumer Behaviors On Smart Grids Energy Systems

The aim of this study is to increase social awareness on consumer behaviors towards smart grid energy system and find out emotional effects of power outages. In parallel to this aim, the study tries to answer the following research questions: In recent years have you ever experienced with long time power outage (energy, water, internet, etc.) that affected your daily life? What did you do when you first encounter with one of the outage? What could be the cause of the outage happened? The Power outage has created what kind of negative effects on you?

Distributed energy systems integration and demand optimization for autonomous operations and electric grid transactions

Distributed power systems in the U.S. and globally are evolving to provide reliable and clean energy to consumers. In California, existing regulations require significant increases in renewable generation, as well as identification of customer-side Distributed Energy Resources (DER) controls, communication technologies, and standards for interconnection with the electric grid systems. As DER deployment expands, customer-side DER control and optimization will be critical for system flexibility and demand response (DR) participation, which improves the economic viability of DER systems. Current DER systems integration and communication challenges include leveraging the existing DER and DR technology and systems infrastructure, and enabling optimized cost, energy and carbon choices for customers to deploy interoperable grid transactions and renewable energy systems at scale.This paper presents a cost-effective solution to these challenges by exploring communication technologies and information models for DER system integration and interoperability. This system uses open standards and optimization models for resource planning based on dynamic-pricing notifications and autonomous operations within various domains of the smart grid energy system. It identifies architectures and customer engagement strategies in dynamic DR pricing transactions to generate feedback information models for load flexibility, load profiles, and participation schedules. The models are tested at a real site in California—Fort Hunter Liggett (FHL). The results for FHL show that the model fits within the existing and new DR business models and networked systems for transactive energy concepts. Integrated energy systems, communication networks, and modeling tools that coordinate supply-side networks and DER will enable electric grid system operators to use DER for grid transactions in an integrated system.

Public policy and electrical-grid sector innovation

Purpose– This paper aims to investigate the manner in which technological innovation in the European electrical-grid sector has developed by focusing, in particular, on the effect of public policy on innovation. To achieve this aim, this paper highlights how technological innovation and development progressed from the 1960s to the 1980s, and contrasts this period with the deregulated/privatization environment.Design/methodology/approach– The paper is based on a series of in-depth multiple company case studies of grid companies, some of their suppliers and other actors in their broader business network. Empirical data were collected through 55 interviews.Findings– The authors find that a phase of mutual collaboration was encouraged in the first period, which led to strong technological innovation with a focus on product quality and the development of functionality. Buyers played a pivotal role in the development of products and posed technical requirements. In contrast, the current role of the buyer has transformed principally into one of evaluating competing bids for specific projects. Today, buyers face increasing pressure to substantially lower CO2emissions and transform the energy grid system. These goals are difficult to achieve without a new way of thinking about innovation.Research limitations/implications– Models to achieve innovation must not only focus on individual research projects; instead, the innovation should be factored into normal business dealings in the supply chain.Practical implications– We propose that policymakers and regulators need to: accommodate for innovation and address the collaborative elements of innovation when developing policies and regulations. Furthermore, regulators have the option of either developing a strategic vision for the electrical-grid network or incorporating sustainability into the evaluation of electrical grids and, thus, consumers’ willingness to pay.Originality/value– This paper makes a distinctive contribution in the area of innovation for electrical grids. Our paper shows how innovation and the development of new technology for electrical grids changed over time. Furthermore, this paper describes the energy sector in terms of a business network comprising the different actors involved in innovation and development and, thus, their role in the energy supply chain.

Preliminary study of high energy density Zn/Ni flow batteries

The escalation of power system promotes the development of energy storage technologies (ESTs). Among all of ESTs, battery technologies develop quickly and diversely because of its huge application market. Aqueous redox flow batteries (RFBs) are very attractive to customers in the energy grid system, and their noticeable technological innovations in past decades are driving them to gradually replace the conventional ESTs under certain circumstance. Here, the first fully-flow-able zinc–nickel flow battery (ZNFB) is preliminary reported in this paper, and its superior performance is supposed to be suitable for both large-scale storage need and carry-on powertrain in cars. Through using semi-solid fuel cell (SSFC) technology, we incorporates the beneficial features of Zn/Ni chemistry (essentially sustainable, eco-friendly and deposit-abundant) into RFB structure to make a “hybrid” flow battery system, which can take the advantage of both. The relationship between carbon loading and suspension conductivity is determined. Electrochemical properties of ZNFB as static test, cycling test, and fully flowing test are studied to demonstrate our design.

Privacy, technology, and norms: The case of Smart Meters

Norms shift and emerge in response to technological innovation. One such innovation is Smart Meters – components of Smart Grid energy systems capable of minute-to-minute transmission of consumer electricity use information. We integrate theory from sociological research on social norms and privacy to examine how privacy threats affect the demand for and expectations of norms that emerge in response to new technologies, using Smart Meters as a test case. Results from three vignette experiments suggest that increased threats to privacy created by Smart Meters are likely to provoke strong demand for and expectations of norms opposing the technology and that the strength of these normative rules is at least partly conditional on the context. Privacy concerns vary little with actors’ demographic characteristics. These findings contribute to theoretical understanding of norm emergence and have practical implications for implementing privacy protections that effectively address concerns of electricity users.

Smart grid opportunities and applications in Turkey

Abstract A smart grid is a system that uses information and communication technologies to integrate, in an intelligent way, all users connected to the electrical power system considering their behaviour and actions. For this purpose, information about the electrical network, such as the current, the voltage or the power, is gathered together over time so that the behaviour of suppliers and consumers can be observed and automatically coordinated. Smart grids are becoming a significant part in the configuration of future electrical power systems. A lot of research has been done on using smart grids to achieve highly efficient and user-friendly electrical power systems. Many new methods have been introduced to solve the difficulties energy providers face when transforming conventional electrical networks into smart grids. These difficulties include the integration of renewable energy and different grid systems at national and international levels due to changes in frequency, voltage and in the synchronisation mechanism. This paper provides an outline of the European smart grid projects and gives an overview of the current infrastructure and smart grid applications of the Turkish Electricity Production System Operator (EUAS), Turkish Electricity Transmission System Operator (TEIAS), and Turkish Electricity Distribution System Operator (TEDAS). In this paper the feasibility of the further steps required is described and some assessments are made and suggestions given on smart grid developments in general.

The Human in the Loop: An Approach to Individualize Smart Process Control

Electrical energy generation and its supply through electricity networks are mainly organized in a top-down, centralized manner. Energy consumption can be predicted quite accurately at a high level which enables to pre-scheduling of production by large power plants. Traditionally, only few actors are involved in the generation, trade, and transportation of electricity, but this is changing rapidly. The increasing share of decentralized renewable energy conversion in combination with new types of buyers and suppliers will drastically alter the operation of electricity infrastructure systems. It has to become smart: the Smart Grid or more general Smart Energy System. In order to minimize uncertainty in the balance between energy supply and demand it is necessary to develop realistic user demand, building and building services installations behavior and Smart Grid interaction. Monitoring the needs of individual users is necessary to predict future states of the demand for the SES (e.g. based on user behavior). The future consumer of energy can become a producer due to the decentralized renewable energy conversion. To control this dynamic and interactive prosumer process support is needed to optimize interaction between offices and Smart Grid. The article describes the first steps towards such system.

Detection and Protection Against Intrusions on Smart Grid Systems

The wide area monitoring of power systems is implemented at a central control center to coordinate the actions of local controllers. Phasor measurement units (PMUs) are used for the collection of data in real time for the smart grid energy systems. Intrusion detection and cyber security of network are important requirements for maintaining the integrity of wide area monitoring systems. The intrusion detection methods analyze the measurement data to detect any possible cyber attacks on the operation of smart grid systems. In this paper, the model-based and signal-based intrusion detection methods are investigated to detect the presence of malicious data. The chi-square test and discrete wavelet transform (DWT) have been used for anomaly-based detection. The false data injection attack (FDIA) can be detected using measurement residual. If the measurement residual is larger than expected detection threshold, then an alarm is triggered and bad data can be identified. Avoiding such alarms in the residual test is referred to as stealth attack. There are two protection strategies for stealth attack: (1) Select a subset of meters to be protected from the attacker (2) Place secure phasor measurement units in the power grid. An IEEE 14-bus system is simulated using real time digital simulator (RTDS) hardware platform for implementing attack and detection schemes.

A Methodology for Emergent Telecommunication Technology Experiments Based on Virtual Environment and AI Techniques

Advanced telecommunications technologies innovations evolve quickly and are often considered as a main component of critical and emerging applications such as Intelligent Transportation Systems (ITS) and Smart Grid (energy systems). The need of rapid deployment of these technologies requires their testing to assess their performance and if necessary seek appropriate configurations that optimize the QoS (Quality Of Service) of associated applications. Existing simulation tools for testing these technologies remain limited when it comes to appraise their innovations involving additional knowledge. We present in this paper a methodology to design and develop a tool for training and experimentation of technologies innovations such as telecommunication. Our approach is focused on the integration of virtual reality concepts based on object oriented modeling and 3 D techniques for realistic scenarios experiments. We also consider artificial intelligence techniques such as inference mechanisms to enable the integration of new knowledge of the technologies to be tested and their management.

Potential evaluation of energy supply system in grid power system, commercial, and residential sectors by minimizing energy cost

AbstractIf the economic activity in the commercial and residential sector continues to grow, improvements in energy conversion efficiencies of energy supply systems is necessary for CO2 mitigation. In recent years, the electricity driven hot water heat pump (EDHP) and the solar photovoltaic (PV) have been commercialized. The fuel cell (FC) of co‐generation system (CGS) for the commercial and residential sector will be commercialized in the future. Copyright © 2004 Wiley Periodicals, Inc.The aim is to indicate the ideal energy supply system of the users sector, which manages both the economical cost and CO2 mitigation, considering the grid power system. In this paper, cooperative Japanese energy supply systems are modeled by linear programming. It includes the grid power system and energy system of five commercial sectors and a residential sector. The demands of sectors are given by the objective term for 2005 to 2025. Twenty‐four‐hour load for each three annual seasons are considered. The energy systems are simulated to minimize the total cost of energy supply, and to mitigate the CO2 discharge. As a result, the ideal energy system at 2025 is shown. The CGS capacity grows to 30% (62 GW) of the total power system, and the EDHP capacity is 26 GW, in commercial and residential sectors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 9–19, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ eej.20361

21619 ガスエンジンの過渡応答特性に関する研究(モデリングと制御,OS.1 実システムのモデリングと制御)

Micro grid energy system is consisted of various kind of electric generator (ex: wind power system that use natural energy, gas engine, storage battery and etc.). These devices are needed to be operated in line for the electricity demand change. Fuel composition also changes in assuming biomass use in micro grid. So, it is important to understand their transient response properties for designing and managing micro grid energy system. In this study, gas engine dynamic model was built to predict transient response and it was also investigated in experiment for existent gas engine. In addition, influence of combustion duration, which was affected by fuel property, on transient response was investigated by using engine dynamic model.

Potential Evaluation of Energy Supply System in Grid Power System, Commercial, and Residential Sectors by Minimizing Energy Cost

If the economic activity in the commercial and residential sector continues to grow, improvement in energy conversion efficiencies of energy supply systems is necessary for CO2 mitigation. In recent years, the electricity driven hot water heat pump (EDHP) and the solar photo voltaic (PV) are commercialized. The fuel cell (FC) of co-generation system (CGS) for the commercial and residential sector will be commercialized in the future.The aim is to indicate the ideal energy supply system of the users sector, which both manages the economical cost and CO2 mitigation, considering the grid power system. In the paper, cooperative Japanese energy supply systems are modeled by linear-programming. It includes the grid power system and energy systems of five commercial sectors and a residential sector. The demands of sectors are given by the objective term for 2005 to 2025. 24 hours load for each 3 annual seasons are considered. The energy systems are simulated to be minimize the total cost of energy supply, and to be mitigate the CO2 discharge. As result, the ideal energy system at 2025 is shown. The CGS capacity grows to 30% (62GW) of total power system, and the EDHP capacity is 26GW, in commercial and residential sectors.