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Journal Paper Accepted: The need for holistic enterprise control assessment methods for the future electricity grid
The LIINES is happy to announce the publication of the journal article “The need for holistic enterprise control assessment methods for the future electricity grid”, by Prof. Amro M. Farid (Dartmouth), Bo Jiang (MIT), Aramazd Muzhikyan (Dartmouth), and Prof. Kamal Youcef-Toumi (MIT) in the journal Renewable and Sustainable Energy Reviews.
In this comprehensive literature-based study, the LIINES presents a logical case for integrating power grid assessment methods into a holistic enterprise control framework. Such a framework is explicitly techno-economic and merges methods power systems engineering and economics. To support the argument, the LIINES has conducted the most comprehensive review of renewable energy integration studies completed to date.
The paper discusses the need for change in the assessment of the electricity grid as a result of five driving forces. The driving forces are identified as: decarbonization, growth of electricity demand, transportation electrification, electric power deregulation, and increasing numbers of responsive (“smart”) consumers. These five drivers require the steadily increasing penetration of solar and wind generation as well as evolving capabilities to support demand side management for the tremendous diversity of loads that connect to the electrical grid. The integration of these three new grid technologies of renewable energy, electric vehicles, and demand side resources ultimately imposes fundamental changes to the grid’s structure and behavior.
The paper argues that the future electric grid’s needs for reliability, cost efficiency and sustainability necessitates a holistic assessment approach. Figure 1 shows a guiding structure that leads to five techno-economic control objectives. This work also uses five lifecycle properties to integrate rather than decompose the engineering design. The lifecycle properties core to the power grid are dispatchability, flexibility, forecastability, stability, and resilience. The use of these five properties avoids overlap in function of solutions.
Using such a holistic paradigm for techno-economic assessment, the journal paper conducts the most comprehensive review of renewable energy studies completed to date. It found several limitations to the existing renewable energy integration studies. Firstly, in order to address the holistic nature of the power grid, the real potential of demand side resources needs to be included. Additionally, for power grid balancing, validated simulations rather than statistical methods based on questionable assumptions need to be used. Furthermore, the consistency between future development of the real market structure and modeling methods needs to be assured. Finally, the investment costs related to the support of the future power grid need to be considered in simulation.
Thus, the paper concludes based on the defined model requirements and the assessment of the current literature, that a framework for holistic power grid enterprise control assessment needs to satisfy the following requirements:
- Allows for an evolving mixture of generation and demand as dispatchable energy resources
- Allows for an evolving mixture of generation and demand as variable energy resources
- Allows for the simultaneous study of transmission and distribution systems
- Allows for the time domain simulation of the convolution of relevant grid enterprise control functions
- Allows for the time domain simulation of power grid topology reconfiguration in operation time scale
- Specifically addresses the holistic dynamic properties of dispatchability, flexibility, forecastability, stability, and resilience
- Represents potential changes in enterprise grid control functions and technologies as impacts on these dynamic properties
- Accounts for the consequent changes in operating cost and the required investment costs.
These requirements have been realized in a power grid enterprise control simulator that was used for an extensive study of renewable energy integration in the power grid [Link 1], [Link 2]. The simulator includes the physical electrical grid layer and incorporates primary, secondary, and tertiary control functions. This model fits the requirements of the holistic enterprise control method as defined previously.
LIINES Website: http://engineering.dartmouth.edu/liines
Journal Paper Accepted: Relative Merits of Load Following Reserves & Energy Storage Market Integration Towards Power System Imbalances
We are happy to announce that our recent paper entitled: “Relative Merits of Load Following Reserves & Energy Storage Market Integration Towards Power System Imbalances”, has been published in the International Journal of Electrical Power & Energy Systems (IJEPES). This study comes as a result of collaboration between three universities; Masdar Institute, Dartmouth, and MIT. The work is authored by Aramazd Muzhikyan (Masdar Institute), Prof. Amro M. Farid (Dartmouth) and Prof. Kamal Youcef-Toumi (MIT).
The existing energy storage resource (ESR) studies bound their discussion to a single timescale of power system operations, such as day-ahead scheduling or real-time balancing. As a result, these studies are only able to capture the impact of the ESR integration on the associated timescale, while any effects that may span across adjacent timescales are omitted. Recently, power grid enterprise control has been developed that integrates different timescales of balancing operations into a multi-layer control hierarchy. The benefits of such holistic power system modeling have been demonstrated for studies on renewable energy integration, the determination of the power system imbalances and the assessment of reserve requirements.
This paper integrates ESRs into the power system enterprise control for the first time. While the ESR integration is expected to mainly affect its associated timescale, such methodology also allows capturing the potential impact on adjacent timescales. If such coupling of timescales exists, it can be exploited to reduce the system resource requirements. This methodology is also used to demonstrate the differences in imbalance mitigation performance of ESRs and load following reserves. While both these resources can be used for balancing the system, the enterprise control methodology unveils their differences and relative merits for different balancing scenarios. The notion of ‘‘utilization efficiency’’ of a given resource is introduced here which is defined as the amount of that resource required to mitigate 1MW of imbalance.
A novel ESR scheduling method has also been developed in this paper that beneficially exploits the coupling between different timescales. Since the day-ahead market has hourly time step, the obtained generation schedule has a stair-like profile with constant values for each hourly interval. However, such stair-like profile does not capture the intra-hour variations of the demand, leading to higher load following reserve requirement. Taking advantage of the timescale coupling, a sub-hourly ESR profile is designed based on the day-ahead market output that, in addition to the traditional benefits of shaving the peak load and reducing the operating cost, also simultaneously reduces the load following reserves requirement. The newly designed ESR schedule is based on piecewise linear harmonic functions and resembles the smooth demand profile within hourly intervals.
The results show that the ESR and the load following reserves have different performances and are better suited for applications in different circumstances. While the utilization efficiency is nearly constant for the load following reserves, the performance of the ESR significantly depends on the temporal characteristics, namely the net load variability and the day-ahead market time step. Higher variability and smaller day-ahead market time step result in better ESR utilization efficiency. The results also show that the generation schedule of the system without ESR has a stair-like form, while the total generation+ESR schedule of the system with ESR integration has a much smoother form and more closely resembles the actual demand profile. This difference defines the actual load following reserve requirement for each system. The results show that the load following reserve requirement of the system with ESR integration is significantly lower compared to the traditional system without ESR.
The comparison of the schedules for a system without ESR and a system with ESR scheduled according to the proposed method
The difference of load following reserve requirements for systems without and with ESR.
In depth materials on LIINES smart power grid research can be found on the LIINES website.
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Journal Paper Accepted: Opportunities for energy-water nexus management in the Middle East and North Africa
by Brian Keare
We are happy to announce that our paper “Opportunities for Energy-Water Nexus management in the Middle East and North Africa”, has been accepted for publication by the academic journal Elementa: Science of the Anthropocene. This study was the result of collaboration between William N. Lubega (Illinois at Urbana-Champaign) and Prof. Amro M. Farid and William W. Hickman (Dartmouth).
Electric power is required to produce, treat, distribute, and recycle water while water is required to generate and consume electricity. Naturally, this energy-water nexus is most evident in multi-utilities that provide electricity and water but still exists when the nexus has distinct organizations as owners and operators. Therefore, the sustainability question that arises from energy-water trade-offs and synergies is very much tied to the potential for economies of scope.
Furthermore, in the Middle East and North Africa (MENA) region, multi-utilities are not only common, but also the nexus is particularly exacerbated by the high energy intensity of the water supply due to limited fresh water resources. Several accelerating trends are increasingly stressing the existing supply systems of MENA countries: Increased demand due to population and economic growth, a more extreme and unpredictable climate mostly affecting water supply and power demand, and multiple drivers for more electricity-intensive water and more water-intensive electricity including aging infrastructure and certain regulations and standards. This paper identifies and motivates several opportunities for enhanced integrated operations management and planning in the energy-water nexus in multi-utilities in the MENA.
From the discussion of the coupling points between the energy and water systems and operations management strategies to optimize these coupling points, several policy implementations can be drawn. First, the existing approaches to dispatch of the individual products of power and water could be replaced by integrated energy-water dispatch. Second, existing fixed power and water purchase agreements can be replaced with a seamlessly integrated energy-water dispatch. As in liberalized power systems, multiple time horizon markets with their respective clearing mechanisms would be required so as to provide dynamic incentives for greater cost and resource efficiency. Fourth, the energy-water nexus also presents coupling points that engage the demand side of both power and water. Carefully designed demand-side management schemes, perhaps in the form of public-private partnerships, could present a vehicle for coordinating these coupling points in a cost-effective fashion.
The report also leads to several central policy implications. First, if water consumption and withdrawal of power generation were monetized, the investment case for renewable energy would inevitably be a stronger one. Next, while reverse osmosis desalination plants limit the energy-intensity of water production, from an integrated systems perspective, multi-stage flash plants provide a coproduction functionality that may be preferred over individual reverse osmosis and power generation facilities. Third, while many water utilities across the region have made extensive efforts towards reducing water leakages, such efforts could be strengthened by considering the embedded energy and the associated economic and environmental cost of these leakages. Lastly, there exists both a necessity and opportunity to reduce the energy footprint of water supply in MENA countries through increased water recycling. Utilizing a decentralized treatment system providing multiple water qualities and treatment levels will allow more opportunities for recycled water use in industry, agriculture, and other areas.
In all, the integrated energy-water nexus planning models and optimization programs presented and cited in this work provide deeper perspectives than their single product alternatives found in the existing literature. Their application in the policy domain has a high potential for future work and extension in the MENA region. Furthermore, these techniques have the potential for use in regions of similar climate (e.g. South-West United States & Australia) or other electricity-water utilities around the globe.
In depth materials on LIINES energy-water nexus research can be found on the LIINES websitte.
Journal Paper Accepted: An A Priori Analytical Method for the Determination of Operating Reserve Requirements
We are happy to announce that our recent paper entitled: “An A Priori Analytical Method for the Determination of Operating Reserve Requirements”, has been accepted at the International Journal of Electrical Power & Energy Systems (IJEPES). This study comes as a result of collaboration between three universities; Masdar Institute, Dartmouth, and MIT. The work is authored by Aramazd Muzhikyan (Masdar Institute), Prof. Amro M. Farid (Dartmouth) and Prof. Kamal Youcef-Toumi (MIT).
As renewable energy becomes an ever present resource in power systems, so called “operating reserves” become increasingly important instruments for reliable power grid operations. One can think of operating reserves as additional generation capacity scheduled to compensate for real-time power supply and demand imbalances due to the existing uncertainties in forecasting not just demand but also renewable energy. On the one hand, the amount of operating reserves should be sufficient to successfully mitigate the real-time imbalances and maintain power system reliable operations. On the other hand, operating reserves are a costly commodity and they should not exceed the minimum required amount to avoid unnecessary expense. This makes accurate assessment of the operating reserve requirements vital for reliable, economic, and environmentally friendly operation of the power grid.
Currently, the necessary amount of the operating reserves is assessed based upon the power system operator experiences and the assumption that the circumstances of power system operations remain relatively unchanged. However, growing integration of renewable energy sources (RES), implementation of demand side management and transportation electrification alter the overall structure and the dynamics of the power grid. High penetration of RES brings new levels of variability and uncertainty to the grid which challenges the established practices of power system operations and the operating reserve requirement assessment methods. This newly published article provides closed-form analytical formulae that tells grid planners how much reserves to procure as they plan for more renewable energy without sacrificing economics or reliability.
While RES integration can potentially reduce the grid’s CO2 emissions and operating costs, it also brings new challenges that power grid operators need to address in order to maintain reliable operations. Wind power, for example, is known to have high intermittency; that is, the output power of a wind turbine may vary uncontrollably in a wide range. This, combined with comparably low wind forecasting accuracy, requires careful scheduling of traditional power plants and their operating reserves. Integration of solar power, on the other hand, has its own challenges. As shown in the figure below, the net load profile (the power demand minus the solar generation) of a system with integrated solar generation has a distinctive profile. It is often called the “Duck Curve” for its resemblance to the side-profile of a duck. The figure presents the net load profiles of the California Independent System Operator (CAISO) for the day of March 31 for forecasted from 2014 to 2020. The “belly” of the curve corresponds to the day time when the solar generation is at its maximum and is expected to grow with new solar power installations. With an estimated demand of 22,000MW in the year 2020, the solar generation accounts for 10,000MW or 45%; leaving only 12,000MW for the traditional generation. This situation increases the risk of overgeneration and solar generation curtailment. Another challenge is the steep jump of the net load around 6pm as solar generation wanes with the sunset and demand picks up for evening home life. Such severe variations of the net load require more careful consideration of the ramping capabilities of the scheduled generation.
The CAISO duck chart (source: P. Denholm, M. O’Connell, G. Brinkman, and J. Jorgenson, “Overgeneration from Solar Energy in California: A Field Guide to the Duck Chart,” National Renewable Energy Laboratory, Nov. 2015)
This publication has developed analytical formulae for calculation of the requirements for each type of operating reserves; namely, load following, ramping and regulation. The derivations show that the operating reserve requirements are effectively defined by a set of dimensionless parameters related to the RES characteristics and the operations of the power grid. Those parameters are the penetration level, renewable energy capacity factor, variability, day-ahead and short-term forecast errors of the integrated RES, and the power grid day-ahead scheduling and real-time balancing time steps. Such analytical expressions reveal how the requirements of each type of reserve will change when, for instance, more renewable energy is integrated, renewable energy forecasting accuracy is improved, and the day-ahead scheduling time step is reduced. This study show that higher RES variability significantly increases the requirements of all three types of reserves. Also, while the impact of the RES forecast error on the ramping reserve requirement is negligible, its impact on the load following and regulation reserve requirements can dominate that of the variability. On the other hand, reducing the day-ahead scheduling time step can mitigate the impact of the variability on the load following reserve requirement while having negligible impact on the ramping and regulation reserve requirements. Also, changing the balancing time step has no noticeable impact on the load following reserve requirement, it has opposing impacts on the ramping and regulation reserve requirements. Reducing the balancing time step reduces the regulation reserve requirement but increases the ramping reserve requirement.
These formulae can be used for renewable energy integration studies, such as those conducted in NE-ISO and PJM-ISO, to assess the required amount of reserves for the planned RES installation. They can also be adapted by the state and federal standards organizations to establish reserve procurement standards that reflect the evolution of the power grid.
In depth materials on LIINES smart power grid research can be found on the LIINES website.
Prof. Amro M. Farid contributes to World Wind Energy Association Report
The World Wind Energy Association (WWEA) technical committee has recently published a report entitled “Wind Energy 2050: On the shape of near 100% RE grid”, which studies the challenges of wind energy integration into the power grid and discusses some of the solutions to address these challenges. Chapters 5 and 6 of this report are based upon the work of Dr. Amro M. Farid and discuss the evolution the power grid as it accommodates increasing capacities of wind energy.
Wind and solar energy have already become mainstream energy sources in some regions of the world. While the integration of wind energy has numerous benefits, it also creates new challenges for power system operations. Wind energy is inherently variable and, in order to successfully accommodate it, the power system has to undergo a dramatic change. Furthermore, and in contrast to the traditional thermal generation units, wind energy sources are non-dispatchable in the traditional sense, meaning their outputs cannot be set to the desired value. As a result, the integration of wind energy requires new approaches to power grid planning and management, including investments into improved wind forecasting techniques and reconsidering operating reserve requirements.
A conventional power system consists of relatively few centralized and dispatchable generation units, and a large number of distributed and stochastic (but accurately forecastable) loads. The electricity is delivered from the centralized and predominantly thermal power plants to the distributed electrical loads. During many decades of operations, power system operators and utilities have developed improved methods for performing their tasks. Generation scheduling and dispatch, reserve management and control technologies have matured. Load forecasting accuracy has improved significantly, reducing forecast errors to as low as a few percent. Power system security and reliability standards have also evolved accordingly.
Six key drivers currently govern the evolution of the grid, namely environment protection, reliability concerns, renewable energy integration, transportation electrification, consumer participation and power market deregulation. This evolution will lead to a diversification of the power grid energy portfolio to include more solar, wind, energy storage and demand-side resources. Thus, the newly emerging operation procedures will not only engage with generators but also with consumers and other ancillary units. As a result, the already existing control technologies and procedures will expand significantly in both number and type. This will challenge the basic assumptions of power system design and operations. Therefore, the question is not how to mitigate wind variability, but rather how the power grid should evolve to successfully accommodate a high penetration of wind energy.
Governed by these drivers, power system generation and consumption will evolve towards more equal roles in grid operations. First, from the perspective of dispatchability, wind energy sources resemble traditional consumption in that they are non-dispatchable and forecasted. On the other hand, the introduction of demand response creates makes some portion of the energy consumption dispatchable much like traditional power generation facilities. These two trends change the balance of dispatchability and forecastability as shown in Table 1. Second, the integration of wind energy, like most renewable energy sources, changes the spatial distribution of the generation. Wind energy sources can vary from several kWs to hundreds of MWs. While larger facilities will continue to be installed centrally into the transmission system, the smaller facilities will be installed at the power grid periphery as distributed generation. (See Figure 2). This creates the potential for upstream flow in the distribution system, which was not generally allowed before, and requires the redesign of the protection system accordingly.
Table 1: Future grid generation and demand portfolio
Figure 2: Graphic representation of the evolving power grid structure
While many power grid phenomena overlap, the literature has traditionally treated them strictly separately. The evolution of the power grid necessitates reconsidering the distinction between timescales. It also requires revisiting the distinction between the transmission and distribution systems. In advocating for power grid enterprise control, our work encourages holistic approaches that work across time scales as well as the fully supply chain of electricity including both the transmission as well as the distribution system.
This work also moves away from the traditional classification of technical and economic control objectives and utilizes the concept of integrated enterprise control as a strategy for enabling holistic techno-economic performance of wind integration. As shown in Figure 3, the power system is modeled as a cyber-physical system, where the physical integration of wind energy and demand-side resources must be assessed in the context of the control, automation, and information technologies. The horizontal axis represents the energy value chain from the generation to the consumption. Finally, the third axis classifies both the generation and the consumption into dispatchable as well as stochastic units. This graph represents the scope of the power system that must address a complex mix of technological, system and societal objectives.
Figure 3: Electrical power grid as a cyber-physical system
This work also moves away from the traditional classification of technical and economic control objectives and utilizes the concept of integrated enterprise control as a strategy for enabling holistic techno-economic performance of wind integration. As shown in Figure 3, the power system is modeled as a cyber-physical system, where the physical integration of wind energy and demand-side resources must be assessed in the context of the control, automation, and information technologies. The horizontal axis represents the energy value chain from the generation to the consumption. Finally, the third axis classifies both the generation and the consumption into dispatchable as well as stochastic units. This graph represents the scope of the power system that must address a complex mix of technological, system and societal objectives.
In depth materials on LIINES smart power grid research can be found on the LIINES website.
Prof. Amro M. Farid gives invited lecture at ITE 2016 Northeastern Annual Meeting
On May 11, 2016, Prof. Amro M. Farid gave an invited lecture at the Institute for Transportation Engineers 2016 Northeastern Annual Meeting held in Portsmouth, NH. The presentation entitled: “Intelligent Transportation-Energy Systems for Massively Electrified Transportation Infrastructure” featured many of the LIINES’ research on electrified transportation systems.
The presentation advocated the concept of “Intelligent Transportation Energy Systems” which has been the subject of several recent blogposts. (See here, here, and here). Electrified modes of transportation: vehicles, buses and trains fundamentally couple the transportation and power grids. This coupling presents new challenges in the operation of each system which would not have existed if each was operated independently. At its core, the ITES requires a new transportation electrification assessment methodology that draws upon microscopic traffic simulation, power grid dynamics, and Big Data-Driven use case modeling. Such an ITES would come to include coupled operations management decisions including: vehicle dispatching, charging queue management, coordinated charging, and vehicle-to-grid ancillary services. The presentation concludes with simulation results from the first full scale electric vehicle integration study which was recently conducted for a taxi-fleet use case in Abu Dhabi.
In depth materials on LIINES electrified transportation system research can be found on the LIINES website.
Journal Paper Accepted at Renewable & Sustainable Energy Reviews – Job Creation Potentials and Skill Requirements in PV, CSP, Wind, Water-to-Energy and Energy Efficiency Value Chains
Job creation is a significant outcome of the development and deployment of renewable energy (RE) and energy efficiency (EE) technologies. With the complicated dynamics related to job creation in RE and EE technologies, this paper considers direct, indirect as well as induced employment opportunities resulting from various sustainable energy sectors.
This paper explores the factors affecting job creation, existing techniques for establishing the job creation potentials, and the required skill sets in the sustainable energy sectors namely; solar PV power, Concentrated Solar Power (CSP), wind power, waste-to-energy, and energy efficiency measures. In addition, it provides case studies showcasing the variation of job creation in Germany, Spain, the United States, and the Middle Eastern region.
Figure 1: This figure represents available jobs within various renewable energy sectors. The figure was prepared by the International Renewable Energy Agency (IRENA) for the Renewable Energy and Jobs Annual Review 2015 IRENA Policy Day 9 June, 2015. Note that Solar Photovoltaic is the leading employer in the renewable energy sector.
For the RE sector, the study shows that available jobs and required skill sets heavily rely on the technology value chains of the specific industry. A further breakdown of the value chains allows for categorization of these jobs on account of their stability and permanency. On the other hand, jobs within the EE sector fall within educational awareness programs, energy efficient policies and regulations, and energy efficiency retrofitting which includes conducting energy audits and re-designing buildings to apply the necessary energy efficient measures.
The Input-Output matrix and Employment factor methods are considered in assessing the gross and net employment impacts of renewable energy deployment. The paper shows that employment factors vary widely based on the region studied, the size of the RE project, and the decomposition of the value chain. In this paper, employment potential is measured based on capacity installed, money invested or number of temporary and permanent jobs created per year.
The paper also provides a breakdown of skill types and levels required within the various sustainable energy sectors. Additionally, it outlines reasons for skill gaps within these RE sectors and provides recommendations on how to bridge such gaps. It observes that skill shortages or surpluses occur mainly due to poor coordination between RE development initiatives and skill providers such as educational institutions. Planning ahead within the RE and EE sectors to ensure better coordination is therefore, highly recommended.
As for the case studies, it is clear that the PV solar industry is at the forefront of job creation in the RE sector. This article shows the high growth potential of the solar PV industry and thus it’s greater opportunity for job creation. In the United States, energy efficiency strategies are predicted to create more than 4-billion job-years by 2030. Given the renewable energy targets and plans set forth by several countries in the Middle Eastern region, a lot of direct and indirect job opportunities are expected to be created in the coming years.
In analyzing the potential of job creation within the RE sectors, the article recognizes that indirect job losses resulting from phasing out fossil fuels, and the increasing electricity prices play a significant role in determining the actual net employment potential of the RE sector. On the other hand, this paper predicts the continued growth in job creation within the EE sector especially given the necessity for energy efficient measures to aid in curbing climate change.
Energy-Water-Food Nexus Research Integral to the IEEE Smart Cities Conference
- The presentation entitled “Extending the Energy-Water Nexus Reference Architecture to the Sustainable Development of Agriculture, Industry & Commerce.” provided a high level overview of the types of couplings that exist not just within the energy and water infrastructure but also within end-uses in the agricultural, industrial, commercial, and residential sectors. Water and energy balance principles were used to systematically highlight the existence of trade-off decisions with the energy-water nexus.
- The presentation entitled “Extending the Utility Analysis and Integration Model at the Energy Water Nexus” featured LIINES research done in collaboration with the Water Environment Foundation (WEF). This work argued the need for integrated enterprise management systems within the water utility sector to support sustainable decision-making.
- The presentation entitled “The Role of Resource Efficient Decentralized Wastewater Treatment in Smart Cities” featured LIINES research done in collaboration with the German startup Ecoglobe. This work argued the need for resource-efficient decentralized wastewater treatment facilities as a key enabling technology in the energy-water-food nexus. It then presented Ecoglobe’s WaterbaseTM as such a technology.
A full reference list of energy-water nexus research at the LIINES can be found on the LIINES publication page: http://engineering.dartmouth.edu/liines
LIINES Website: http://engineering.dartmouth.edu/liines
IEEE Smart Cities Conference Establishes Itself as Premier Conference
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