No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Nation-wide Transmission Overlay Design and Benefits Assessment for the U S
Abstract
A U.S. nation-wide transmission overlay is a high capacity, multi-regional transmission grid, potentially spanning all three interconnections, designed as a single integrated system to provide economic and environmental benefits to the nation. The objective of this paper is to identify benefits to building a national transmission overlay and to lay out essential elements to facilitate continued dialog on this topic. A preliminary study performed on a national scale using a long term investment planning software illustrated that a national transmission overlay, under a high renewable penetration scenario, could result in cost-reduction of between one quarter trillion and one-half trillion dollars over a 40-year period, while promising to increase infrastructure resilience and flexibility.
... Nonetheless, limited attention has been paid to developing a comprehensive methodology to determine the benefits that each network user or national/local system is expected to obtain from expansion projects, especially when said projects are part of large expansion plans. Typically, benefits and beneficiaries are assessed for the whole plan, and not for each individual project [21,22]. However, allocation of the benefits of the whole expansion plan to each of the individual projects that comprise it remains largely unexplored. ...
... If the variable leaving the basis in step k is the production of generation unit g 0 , the relative contribution of an expansion project l to the change in the production of this unit (Cgp l g 0 ) is computed according to (21). This results from dividing the total change caused by this project in the production of g 0 (Vgp l g 0 ), which is calculated according to the new AS game using (22), by the sum of the overall changes caused by every project of the plan in the production of this same unit. ...
... , respectively. The overall change in the level of the variable leaving the basis caused by each project l, Vgp l g 0 , previously computed as in(22), should be replaced, both in(21) and(22), by Vens l ...
The objective of this paper is to propose a novel methodology to compute the benefit obtained by the individual transmission network users from each of the transmission expansion projects within an expansion plan. The benefits computed should be coherent with the technical and economic principles that underlie the development of the expansion plan. Thus, this methodology is based on the idea that the benefits produced by each project of a plan should be determined considering all projects jointly, instead of individually. Some benefits obtained by users from projects evolve continuously with the deployment of the expansion plan, while others are discrete, since they occur at certain points of the deployment of this plan. A separate Aumann-Shapley game is solved to allocate continuous benefits, and each discrete one. In the second case, the standard Aumann-Shapley algorithm for the allocation of benefits is modified to cope with the fact that the function of each user’s benefits is not continuous with the size of projects deployed. Two case studies are used to compare the methodology proposed with existing ones and demonstrate its applicability to real-life decision making processes. The results show that the methodology proposed is able to overcome problems detected in other methodologies, providing more accurate and sound results. The good properties of the methodology proposed make it applicable to problems related to network expansion regulation, such as the cost allocation of new investments. Although the methodology proposed is particularized to electric power systems, its concept and fundamentals can also be applied in other energy sectors, such as gas.
... Consequently, benefits calculations for transmission expansion should consider not only fuel savings resulting from reduced transmission congestion, as is traditionally done in production costing studies, but also capital cost savings from more efficient generation investment. By modeling interactions between transmission and generation economics, cooptimization models promise solutions that are less expensive in total compared to decoupled optimization (transmission-only, generation-only, or iteration between the two) [1,2]. ...
... A complete mathematical formulation of an ACOPF-based generation and transmission planning model (ACOPF-GTEP) is presented as equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in Section A.1 of the appendix. The integer variables and non-linear constraints that render the problem a MINLP are shown in equations (2)(3)(4)(5)8). ...
... A complete mathematical formulation of an ACOPF-based generation and transmission planning model (ACOPF-GTEP) is presented as equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in Section A.1 of the appendix. The integer variables and non-linear constraints that render the problem a MINLP are shown in equations (2)(3)(4)(5)8). If a strategy for dividing the problem into investment and operating (OPF) subproblems is pursued, then the OPF is a continuous nonlinear optimization problems (NLPs). The OPF can be solved by iterative methods involving basic line-search steps [40], where an initial solution x 0 at k=0 is chosen, and then a search direction d k and an appropriate step size s k are selected to update the solution vector x k ; this search is repeated until the convergence criterion is met. ...
The recognition of transmission’s interaction with other resources has motivated the development of co-optimization methods to optimize transmission investment while simultaneously considering tradeoffs with investments in electricity supply, demand, and storage resources. For a given set of constraints, co-optimized planning models provide solutions that have lower costs than solutions obtained from decoupled optimization (transmission-only, generation-only, or iterations between them). This paper describes co-optimization and provides an overview of approaches to co-optimizing transmission options, supply-side resources, demand-side resources, and natural gas pipelines. In particular, the paper provides an up-to-date assessment of the present and potential capabilities of existing co-optimization tools, and it discusses needs and challenges for developing advanced co-optimization models.
... However, if the required capacity for ancillary services is estimated and represented in the long-term investment planning tool [71], then such devices' capacity subject to their utilization factor [139] can be considered in the overall portfolio planning. ...
... (a) National level electric (13 electric regions) and transportation (freight and personal vehicles in 48 states) portfolio planning [59] (b) Nation-wide transmission overlay design and benefit assessment (13 electric regions, no transportation) [71] • ...
... Fuel sources represented within energy sector[71] ...
... Consequently, benefits calculations for transmission expansion should consider not only fuel savings resulting from reduced transmission congestion, as is traditionally done in production costing studies, but also capital cost savings from more efficient generation investment. By modeling interactions between transmission and generation economics, cooptimization models promise solutions that are less expensive in total compared to decoupled optimization (transmission-only, generation-only, or iteration between the two) [1,2]. ...
... A complete mathematical formulation of an ACOPF-based generation and transmission planning model (ACOPF-GTEP) is presented as equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in Section A.1 of the appendix. The integer variables and non-linear constraints that render the problem a MINLP are shown in equations (2)(3)(4)(5)8). ...
... A complete mathematical formulation of an ACOPF-based generation and transmission planning model (ACOPF-GTEP) is presented as equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in Section A.1 of the appendix. The integer variables and non-linear constraints that render the problem a MINLP are shown in equations (2)(3)(4)(5)8). The convergence and computational challenges of solving that problem make it impractical to apply for real world applications [38]. ...
Under review in ENERGY SYSTEMS Journal
... A 2% yearly discount rate applied to the cost information within the optimization. Data for energy side of the national network is provided in [10,15], which includes electric network divided into 13-regions as defined by the DOE for NEMS, and the modeling details of fuel network (i.e., regional coal (production capacities and cost) and natural gas (cost and capacities of production, pipeline transportation and storage)). The cost, capacity and efficiency data used for hydrogen production, transmission and distribution network were provided in Tables 4 and 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 ...
... NETPLAN is developed to perform assessments over extended time periods, on the order of 40 or more years, in comparison to the traditional 20-30 year planning horizon required by most state and federal regulatory bodies today. NETPLAN has been applied in several studies; results of representative studies are reported in [11,12,13,14,15,16]. ...
... A 2% yearly discount rate applied to the cost information within the optimization. Data for energy side of the national network is provided in [10,15], which includes electric network divided into 13-regions as defined by the DOE for NEMS, and the modeling details of fuel network (i.e., regional coal (production capacities and cost) and natural gas (cost and capacities of production, pipeline transportation and storage)). The cost, capacity and efficiency data used for hydrogen production, transmission and distribution network were provided in Tables 4 and 5 ...
This paper assesses using hydrogen as alternative fuel in U.S light-duty vehicle (LDV) transportation system. Firstly, the paper develops the hydrogen network model consisting of multiple production pathways that eventually lead to the fuel-cell vehicles (FCVs) for passenger transportation; such that the interdependency of hydrogen network with energy system and the competition of FCVs with other LDV modes (plug-in hybrid electric vehicles and gasoline vehicles) are captured. Then, the evaluation of economics and environmental impact of large-scale hydrogen deployment in national LDV market is analyzed by simulating long-term energy and transportation infrastructure planning studies, and the factors that influence the penetration of FCVs are assessed from the national economics and sustainability standpoint. It is seen from the results that economics and sustainability of PHEV penetration is very much dependent on the availability of low cost renewables, and given a practical limit on renewable generation expansion and tighter imposition of carbon policies, FCVs do prove to be highly valuable in rendering the national LDV portfolio sustainable and resilient against petroleum related events. With improvements in FCV investment cost of about 11-19%, they can outperform PHEVs and gasoline vehicles as the economic and sustainable LDV option under high renewable power generation portfolio.
... The NET-PLAN tool will be used in this paper to simulate various long-term capacity expansion scenarios, and assess the role of biorenewables. NETPLAN in the past has been used to perform various planning studies with an intent to assess long-term cost, emissions and resilience associated with nation-wide infrastructure planning, including assessing the impact of high-speed rail (HSR) on U.S. passenger transportation [18], designing high capacity interregional transmission overlay under high renewable scenarios [19,35], designing resilient energy infrastructure against catastrophic events [36], and planning national light duty vehicle portfolio [37]. NETPLAN is written in Cþþ, and the code and the data are made public 3 . ...
... The investment cost of geothermal generation technology varies with geography due to the varying drilling depth required to reach suitable temperature underground. These investment costs and the geographically varying capacity factors for wind and solar generation (as shown in Table 9) for the 13 regions are provided in Ref. [35]. The model also considers coal, IGCC, and NGCC units with carbon capture and sequestration (CCS) installations. ...
Bio-power and biofuels are promising alternative energy resources. This paper investigates their role in the long-term U.S. national energy and transportation portfolio planning, while considering the competition among other energy options. The paper presents a systematic modeling framework for integrating biomass pathways to the energy and transportation systems, and also captures the geographical variation in the feedstock availability and cost across the U.S. The paper then presents two different case studies-energy sector planning and integrated energy & transportation sectors planning. The studies reveal long-term cost and emission savings from bio-renewables, where the bulk of benefits are observed due to biofuels (with bio-power production limited by feedstock prices). Under a 40% CO2 emissions reduction scenario over the next 40 years, penetration of bio-renewables promise up to 10-Trillion USD (2010$) savings in system costs (investments and operational). Simulations also show that the impediment with bio-renewable penetration is mostly influenced by the availability of low-cost feedstock, specifically for bio-power production. According to current estimation of long-term feedstock availability, U.S will be able to power upto 150 Billion Gallons Year (BGY) (or approx. 560*109 L per year) bio-refinery capacity around 2020s, and about 200 BGY (or approx. 750*109 L per year) by 2050.
... In [2,20], we describe three distinct paths that could be pursued to realize continentwide interregional transmission design: market driven investment, federal initiative, and interregional coordination. There are elements of each of these three approaches ongoing today. ...
The U.S. Department of Energy's national congestion study [1] indicates that electric transmission congestion has become more severe inhibiting interregional power exchange. High quality renewable resources in the U.S. are generally remote from load centers; thus, renewable growth is inhibited by insufficient transmission as electric transmission is the only way to move renewable energy. A recent report on this issue [2] concludes that a national transmission overlay, defined as high-capacity, multi-regional grid that spans all interconnections, provides economic, environmental, and system performance benefits. Such an interregional transmission grid is of increased interest when the cost of generation resources reflects high geographical variation as do renewables such as wind, solar, and geothermal. References [3]-[4] perform interconnection-wide planning studies, focusing on renewable deliverability. References [5]-[7] provide national overlay conceptual designs. These designs differ widely in terms of network topology and transmission technology. European efforts towards a similar 'supergrid' concept are well-documented [7]. The problem of designing an integrated national overlay is inherently different from transmission design that occurs in regional planning processes. First, economic justification typically requires a long planning horizon, at least 20 years but preferably longer, to account for economic value of investments having long lifetimes. Second, an integrated transmission overlay joining all interconnections is a large-scale, comprehensive addition to the existing grid, in contrast to more incremental additions that have driven the transmission planning process for decades. In this paper, we introduce a planning approach for interregional transmission design at the national or continental level, for high renewable futures, and we apply it to the U.S. system to design transmission overlays under a high-renewable future. Benefits of the designed overlay are compared to those of the same renewable penetration but with interregional transmission capacity fixed at today's levels. Associated simulation results suggest that such an overlay provides social, economic and environmental benefits, by optimizing investment and production costs, reducing carbon emissions, creating renewable-related employment opportunities and lowering overall electricity prices.
... Our literature review also found some particular research works focused on the co-planning between energy and transportation systems (Table A10 -Appendix A). A long-term investment planning model has been developed by [180] using the National Long-term Energy and Transportation Planning (NETPLAN) software focused on a 40-year planning period for both the United States energy and freight transportation systems. This research focused on identifying the possible benefits of building a national transmission overlay in the country. ...
Co-optimization for power system operation and expansion planning is reviewed.
The majority of short-term studies have grown up around energy and reserve markets.
Co-optimization might lead to less costly solutions than traditional techniques.
The need to coordinate the necessary data from multiples actors is a challenge.
Integrating supply and demand-side options has been recognized as a current need.
https://authors.elsevier.com/a/1dn7o15eif0fES
... This fact can be aggravated if in the future new massive renewable generation is located far from load centres and new overlay transmission networks or supergrids are built to distribute this energy throughout a continental area. Even though in some regions the HVDC option is now preferred [10], in others could be more convenient the HVAC traditional solution [11,12]. ...
This work tackles in a practical way the problem of short-term voltage stability at bulk power systems from the point of view of the overhead lines parameters: length and compactness. With that aim the 9-bus IEEE test system, properly modified to tailor the needs of the study, is simulated in Simulink under high load conditions for different line parameters, analysing the effects of these parameters on the severity of the instability and the recovery rate of the system under different scenarios: no FACTS, SVC and STATCOM. The main findings of the study are included in the conclusions.
... George and Banerjee (2011) do likewise for a specific Indian region. The benefits of an overlay transmis- sion grid network in the United States are outlined in Krishnan et al. (2013), who indicate that variability of renewable energy justifies investments into a resilient, flexible overlay grid. None of the mentioned studies cover the European dimension addressed specifically here in this chapter. ...
This dissertation uses three models to analyze different decarbonization strategies for combating global climate change: The cost minimizing mixed-integer model CCTS-Mod examines the economics of Carbon Capture, Transport, and Storage (CCTS) for the electricity and industry sector; the welfare maximizing quadratically constrained model ELMOD focuses on different trajectories for renewable energy sources (RES) and transmission grid expan-sions; and the equilibrium model ELCO combines the insights of the individual sectors to a combined CCTS and electricity investment and dispatch model.
Modeling results show that an investment in CCTS is beneficial for the iron and steel sector once the CO2 certificate price exceeds 50 €/t CO2. The threshold is 75 €/t CO2 for the cement industry and 100 €/t CO2 for the electricity sector. Additional revenues from using CO2 for enhanced oil recovery (CO2-EOR) lead to an earlier adoption of CCTS in the North Sea region. The lack of economies of scale results in increasing CO2 storage costs of more than 30%, while transport costs even double. Research from the last years, however, indicates that CCTS is unlikely to play an important role in decarbonizing the electricity sector. The identified reasons for this are incumbents’ resistance to structural change, wrong technology choices, over-optimistic cost estimates, a premature focus on energy projects instead of industry, and the underestimation of transport and storage issues.
Keeping global temperature rise below 2°C therefore implies the phase-out of fossil-fueled power plants and, in particular, of CO2-intensive coal power plants. The low CO2 price established by the European Emissions Trading Scheme is insufficient to induce a fuel switch in the medium term. Therefore, supplementary national measures are necessary to reduce coal-based power generation; i.a. feed-in tariffs for RES, minimum CO2 prices, or emissions performance standards. Analyses for Germany show that a coal phase-out before 2040 is possible without risking resource adequacy at any point. Enabling a smooth transition en-courages other countries to take the German Energiewende as a blueprint to combat global warming, even if this implies a coal phase-out.
... modeled as 13 regions, as defined by the U.S. Department of Energy (DOE) Energy Information Administration (EIA) for NEMS (U.S. Energy Information Administration, 2000). The average electric demand and generation mix within each region in the reference year (2009), andcapacities for the aggregated inter-regional transmission lines are provided in(Krishnan, 2013a). The annual average demand for electricity and natural gas is assumed to increase at a rate of 1.5% and 1% per year, respectively, and the annual peak electric demand is assumed to increase at 2% per year. ...
This paper presents a long-term investment planning model that co-optimizes infrastructure investments and operations across transportation and electric infrastructure systems for meeting the energy and transportation needs in the United States. The developed passenger transportation model is integrated within the modeling framework of a National Long-term Energy and Transportation Planning (NETPLAN) software, and the model is applied to investigate the impact of high-speed rail (HSR) investments on interstate passenger transportation portfolio, fuel and electricity consumption, and 40-year cost and carbon dioxide (CO2) emissions. The results show that there are feasible scenarios under which significant HSR penetration can be achieved, leading to reasonable decrease in national long-term CO2 emissions and costs. At higher HSR penetration of approximately 30% relative to no HSR in the portfolio promises a 40-year cost savings of up to $0.63 T, gasoline and jet fuel consumption reduction of up to 34% for interstate passenger trips, CO2 emissions reduction by about 0.8 billion short tons, and increased resilience against petroleum price shocks. Additionally, sensitivity studies with respect to light-duty vehicle mode share reveal that in order to realize such long-term cost and emission benefits, a change in the passenger mode choice is essential to ensure higher ridership for HSR.
... George and Banerjee (2011) do likewise for a specific Indian region. The benefits of an overlay transmission grid network in the United States are outlined in Krishnan et al. (2013), who indicate that variability of renewable energy justifies investments into a resilient, flexible overlay grid. None of the mentioned studies cover the European dimension addressed specifically here in this article. ...
This article presents a quantitative assessment of the need for electricity transmission capacity investments in Germany for 2030. Congestion is analyzed and its possible relief through appropriate grid reinforcements as those described in the Ten Year Network Development Plan (TYNDP) of the European Commission. Congestion is investigated in three scenarios which differ in the location of power resources and the line expansion projects accomplished. Results show that the TYNDP and overlay line projects proposed in 2011 are not sufficient measures to cope with the increasing demand for transmission capacity. The paper also concludes that if power generation resources are moved closer to demand centers grid bottlenecks can be partly relieved by 2030. The introduction of a high-voltage direct current (HVDC) backbone grid does not relieve congestion significantly.
Energy system models play an important role in evaluating potential pathways to a low-carbon energy system. Modeling the electrical grids within an energy system model raises the computational burden significantly. This is the reason why the grid is often reduced to a lower amount of nodes. While grid reduction is common in energy system models, the partitioning of the grid is mostly done manually. A grid reduction method is proposed that takes electrical parameters of the grid as well as other parameters, such as political borders or region-specific renewable potentials, into account. The proposed reduction method uses clustering based on electrical distance to identify regions with high electrical connectivity to minimize load flow deviations after the reduction. The method is compared against another state-of-the-art partitioning-based reduction method. The comparison shows that the partitioning plays an important role on the accuracy of line power flows when reducing grids for energy system analysis. An additional investigation is carried out on the ratio of recognized overloaded lines in the reduced grids. With respect to studied parameters, the proposed reduction method prevails. The findings can thus be used to more accurately reduce and represent electrical grids in energy system models.
Over the years, renewable energy based power generation has proven to be a cost-effective solution in stand-alone applications in the regions where grid extension is difficult. The present study focused on the development of models for optimal sizing of integrated renewable energy (IRE) system to satisfy the energy needs in different load sectors of four different zones considered in Chamarajanagar district of Karnataka state in India. The objective of the study is to minimize the total cost of generation and cost of energy using genetic algorithm (GA) based approach. Considering optimization power factor (OPF) and expected energy not supplied (EENS), optimum system feasibility has been investigated. Based on the study, it has been found that IRES is able to provide a feasible solution between 1.0 and 0.8 OPF values. However, power deficit occurs at OPF values less than 0.8 and the proposed model becomes infeasible under such conditions. Customer interruption cost (CIC) and deficit energy (DE) for all zones were also computed to quantify the reliability of the systems.
The current supply for electricity generation mostly relies on fossil fuels, which are finite and pose a great threat to the environment. Therefore, energy models that involve clean and renewable energy sources are necessary to ease the concerns about the electricity generation needed to meet the projected demand. Here, we mathematically model a hybrid energy generation and allocation system where the intermittent solar generation is supported by conventional hydropower stations and diesel generation and time variability of the sources are balanced using the water stored in the reservoirs. We develop a two-stage stochastic model to capture the effect of streamflows which present significant inter-annual variability and uncertainty. Using sample case studies from India, we determine the required hydropower generation capacity and storage along with the minimal diesel usage to support 1 GWpeak solar power generation. We compare isolated systems with the connected systems (through inter-regional transmission) to see the effects of geographic diversity on the infrastructure sizing and quantify the benefits of resource-sharing. We develop the optimal sizing relationship between solar and hydropower generation capacities given realistic cost parameters and real data and examine how this relationship would differ as the contribution of diesel is reduced. We also show that if the output of the solar power stations can be controlled (i.e. spill is allowed in our setting), operating them below their maximum energy generation levels may reduce the unit cost of the system.
This paper assesses using hydrogen as alternative fuel in U.S LDV (light-duty vehicle) transportation system. Firstly, the paper develops the hydrogen network model consisting of multiple production pathways that eventually lead to the FCVs (fuel-cell vehicles) for passenger transportation; such that the interdependency of hydrogen network with energy system and the competition of FCVs with other LDV modes (plug-in hybrid electric vehicles and gasoline vehicles) are captured. Then, the evaluation of economics and environmental impact of large-scale hydrogen deployment in national LDV market is analyzed by simulating long-term energy and transportation infrastructure planning studies, and the factors that influence the penetration of FCVs are assessed from the national economics and sustainability standpoint. It is seen from the results that economics and sustainability of PHEV (pluggable electric hybrid vehicle) penetration is very much dependent on the availability of low cost renewables, and given a practical limit on renewable generation expansion and tighter imposition of carbon policies, FCVs do prove to be highly valuable in rendering the national LDV portfolio sustainable and resilient against petroleum related events. With improvements in FCV investment cost of about 11-19%, they can outperform PHEVs and gasoline vehicles as the economic and sustainable LDV option under high renewable power generation portfolio.
There is significant interest in building transmission today all over the world, especially inter-regional transmission to interconnect the cheaper renewables which are geographically diverse to load centers. In US, the nation's most economically attractive renewable resources are located in the West and Midwest, and most electric consumption is in the East, and a national transmission seems a viable option to supply increasing demand at economical and sustainable manner. This paper presents a short survey of various major electric transmission technologies in terms of their cost and operational characteristics in the context of planning long distance bulk transmission overlay.
This paper presents a computational technique for conducting assessments of multi-area power system frequency dynamics using reachability analysis theory. To this end, a reduced-order model of the U.S. power system with high renewable penetration is derived. We investigate the control capabilities of HVDC lines to improve the frequency response of asynchronously connected regions, and to transmit the variability of renewable sources within synchronously connected areas. In this modeling framework, disturbances and parameters are treated as belonging to unknown-but-bounded sets. The analysis yields bounds that are guaranteed to contain the trajectories of all possible scenarios.
Anthropogenic carbon dioxide (CO2) emissions and the resulting influence on global climate change have motivated nations throughout the world to reconsider how we obtain, move, and utilize energy. Use of the Sankey diagrams produced annually by Lawrence Livermore National Labs (see https://flowcharts.llnl.gov) indicates that in 2011, energy harvested in the United States was converted to electricity (40%), used for transportation (28%), or used for heating and industrial processes (32%). Similarly, in 2010, energy-related CO2 emissions were due to electric conversion (40%), transportation (33%), and heating and industrial processes (27%). (Including non-CO2 greenhouse-gas emissions does not significantly change these percentages.) Because energy-related CO2 emissions come from the combustion of fossil fuels (coal, petroleum, and natural gas), there has been much emphasis on reducing reliance on these fuels or shifting some use of coal or petroleum to the use of cleaner-burning natural gas, along with reducing energy consumption via efficiency improvements and conservation.
This paper describes new investment planning software which is multi-sector (fuels, electric, and transportation), multiobjective, national, and long-term (40 years) that identifies a set of non-dominated national investment strategies. It optimizes three objectives: cost, emissions, and system resilience to major disruptions such as the Katrina and Rita hurricanes. Solutions are identified in terms of technologies (generation, transmission, fuel infrastructure, and transportation infrastructure), capacity, investment year, and geographic location. Network topology is respected. This paper focuses on modeling operational effects of growing wind generation in terms of regulation, reserves, ramping capability and capacity, and their influence on planning the future generation portfolios.
The most significant energy consuming infrastructures and the greatest contributors to greenhouse gases for any nation today are electric and freight/passenger transportation systems. Technological alternatives for producing, transporting, and converting energy for electric and transportation systems are numerous. Addressing costs, sustainability, and resiliency of electric and transpor-tation needs requires long-term assessment since these capital-intensive infrastruc-tures take years to build with lifetimes approaching a century. Yet, the advent of electrically driven transportation, including cars, trucks, and trains, creates poten-tial interdependencies between the two infrastructures that may be both problemat-ic and beneficial. We are developing modeling capability to perform long-term electric and transportation infrastructure design at a national level, accounting for their interdependencies. The approach combines network flow modeling with a multiobjective solution method. We describe and compare it to the state-of-the-art in energy planning models. An example is presented to illustrate important fea-tures of this new approach.
The transportation and electric sectors are by far the largest producers of greenhouse emissions in the United States while
they consume a significant amount of the national energy. The ever rising demand for these systems, the growing public concern
on issues like global warming or national security, along with emerging technologies that promise great synergies between
both (plug-in hybrid vehicles or electrified rail), creates the necessity for a new framework for long-term planning. This
paper presents a comprehensive methodology to investigate long-term investment portfolios of these two infrastructures and
their interdependencies. Its multiobjective nature, based on the NSGA-II evolutionary algorithm, assures the discovery of
the Pareto front of solutions in terms of cost, sustainability and resiliency. The optimization is driven by a cost-minimization
network flow program which is modified in order to explore the solution space. The modular design enables the use of metrics
to evaluate sustainability and resiliency and better characterize the objectives that the systems must meet. An index is presented
to robustly meet long-term emission reduction goals. An example of a high level representation of the continental United States
through 2050 is presented and analyzed using the present methodology.
KeywordsEnergy–Transportation–Long-term investment–Multiobjective optimization–Evolutionary programming
Renewable resources in North America are extensive and are expected to represent a growing share of total resources. Large hydro and geothermal resources are concentrated in fixed locations and can be readily dispatched. Wind and solar resources are more dispersed, remote from major load centers, and variable in their output. New electric transmission infrastructure is needed to access newly developed renewable resources. For optimal transmission development, it is essential to take a long term approach that reflects the characteristics of the sources being connected. The transmission system must have capacity to aggregate these diverse renewable sources, transport usable blocks of power to remote load centers and disperse the power to load serving entities in an efficient and reliable manner. This paper outlines strengths and complementary features of extra-high-voltage alternating current (EHV AC) and high voltage direct current (HVDC) transmission systems and advocates a hybrid approach, tailored to integrating renewable resources. Variability of generation can be moderated across larger zones, losses can be reduced through higher voltage and improved grid efficiency, reliability can be strengthened with enhanced system control, and the use of resources and rights of way can be optimized with respect to the need, economics and environment. AC systems provide flexible access to sources and loads alike. An expansive overlay of the highest practical AC voltage forms the network backbone, serving as a high capacity platform for system integration. HVDC transmission offers express, efficient delivery of large blocks of power from point to point over long distances, continuous power flow control, fault current limitation and links that can tie asynchronous AC systems. HVDC is also well suited to submarine or underground links, where AC connections are difficult or impractical. Underground HVDC can provide easier access into densely populated urban areas as a creative "-
off ramp" or extension of the grid. Combining the strengths of EHV AC and HVDC technologies can focus the effectiveness of renewable energy and extend the practical range of its reliable delivery. These technologies' particular strengths can work well together in many settings. A long term view with a broader planning scope requires coordination and recognition that the ideal system is greater than a collection of disparate projects.
Congestion analysis using National Energy Modeling National Energy Modeling System (NEMS) or NEMS-derivatives, such as LBNL-NEMS, is subject to significant caveats because the generation logic inherent in NEMS limits the extent to which interregional transmission can be utilized and intraregional transmission is not represented at all. The EMM is designed primarily to represent national energy markets therefore regional effects may be simplified in ways that make congestion analysis harder. Two ways in particular come to mind. First, NEMS underutilizes the capability of the traditional electric grid as it builds the dedicated and detached grid. Second, it also undervalues the costs of congestion by allowing more transmission than it should, due to its use of a transportation model rather than a transmission model. In order to evaluate benefits of reduced congestion using LBNL-NEMS, Berkeley Lab identified three possible solutions: (1) implement true simultaneous power flow, (2) always build new plants within EMM regions even to serve remote load, and (3) the dedicated and detached grid should be part of the known grid. Based on these findings, Berkeley Lab recommends the following next steps: (1) Change the build logic that always places new capacity where it is needed and allow the transmission grid to be expanded dynamically. (2) The dedicated and detached grid should be combined with the traditional grid. (3) Remove the bias towards gas fired combine cycle and coal generation, which are the only types of generation currently allowed out of region. (4) A power flow layer should be embedded in LBNL-NEMS to appropriately model and limit transmission.
We refer to the national infrastructure necessary to provide electric energy in the U.S. as the National Electric Energy System (NEES). It includes the three primary energy production and transportation subsystems: electric, natural gas, and coal. In order to facilitate the study of very large-scale disruptions within the NEES, we have developed a multiperiod network flow model able to simulate the movements of bulk energy flows through the network and represent large-scale disruptions on critical infrastructure. This paper describes the model with focus on special features necessary to analyze large-scale disruptions. In order to validate our approach, we have collected disruption data following the 2005 Gulf-coast Hurricanes Katrina and Rita and then incorporated these data into the model. By comparing the results with and without the hurricanes, the additional operational costs as a result of them are estimated to be $10.5 billion from September to December 2005.
Modeling Interregional Transmission Congestion in the National Energy Modeling System, LBNL 59076 A multiobjective optimization approach to the operation and investment of the national energy and transportation systems
- E Gumerman
- P Chan
- B Lesieutre
- C Marnay
- J Wang
Gumerman, E., Chan, P., Lesieutre, B., Marnay, C., Wang, J., May 2006. Modeling Interregional Transmission Congestion in the National Energy Modeling System, LBNL 59076. Available from: /http://eetd.lbl.gov/ea/emp/reports/ 59076.pdfS. Ibanez, E., May 2011. A multiobjective optimization approach to the operation and investment of the national energy and transportation systems. Ph.D. Disserta-tion, Iowa State University.
A multiobjective optimization approach to the operation and investment of the national energy and transportation systems
- E Ibanez
Ibanez, E., May 2011. A multiobjective optimization approach to the operation and
investment of the national energy and transportation systems. Ph.D. Dissertation, Iowa State University.
Order on Application for Authorization to Sell Transmission Services at Negotiated Rates
Order on Application for Authorization to Sell Transmission Services at Negotiated
Rates, March 2010. U.S. Federal Energy Regulatory Commission. Available from:
/http://www.ferc.gov/whats-new/comm-meet/2010/031810/E-12.pdfS.
- T Overbye
Overbye, T., et al., 2002. National Energy Supergrid Workshop Report. /http://
energy.ece.illinois.edu/SuperGridReportFinal.pdfS.
About the New Madrid Fault
- Charles St
- County
St. Charles County. About the New Madrid Fault. URL /www.scchealth.org/docs/
ems/docs/prepare/newmadrid.htmlS.
National Electric Transmission Congestion Study
- U S Doe
U.S. DOE, 2009. National Electric Transmission Congestion Study.
Electricity Supply & Demand Database
- Nerc
NERC, 2010. Electricity Supply & Demand Database. /www.nerc.com/page.
php?cid ¼ 4938S.