Benjamin Hobbs

Johns Hopkins University | JHU · Environment, Energy, Sustainability and Health Institute

The presence of variable renewable energy resources with uncertain outputs in day-ahead electricity markets results in additional balancing needs in real-time. Addressing those needs cost-effectively and reliably within a competitive market with unbundled products is challenging as both the demand for and the availability of flexibility depends on...

As the role of variable renewables in electricity markets expands, new market products help system operators manage imbalances caused by uncertainty and variability. Whereas work in the last decade has focused on constructing demand curves for central procurement of those products, little attention has been paid to designing their settlement scheme...

Utilizing energy storage solutions to reduce the need for traditional transmission investments has been recognized by system planners and supported by federal policies in recent years. This work demonstrates the need for detailed reliability assessment for quantitative comparison of the reliability benefits of energy storage and traditional transmi...

Net load uncertainty in electricity spot markets is rapidly growing. There are five general approaches by which system operators and market participants can use probabilistic forecasts of wind, solar, and load to help manage this uncertainty. These include operator situation awareness, resource risk hedging, reserves procurement, definition of cont...

How can independent system operators (ISOs) take advantage of probabilistic solar forecasts to lower generation costs and improve reliability of power systems? We discuss one three-step approach for doing so, focusing on how such forecasts might help the California Independent System Operator (CAISO) prepare unexpected net load ramps, where net loa...

Ramping products have been introduced or proposed in several U.S. power markets to mitigate the impact of load and renewable uncertainties on market efficiency and reliability. Current methods often rely on historical data to estimate the requirements of ramping products and fail to take into account the effects of the latest weather conditions and...

Capacity planning models and resource adequacy assessments have often relied on averaging and sampling techniques that disregard important reasonably expected interactions of weather-based resources. We provide a method to capture the economic value of information and reliability risk from using inadequate sample data to design sustainable systems...

This paper introduces the full Low-carbon Expansion Generation Optimization (LEGO) model available on Github (https://github.com/wogrin/LEGO). LEGO is a mixed-integer quadratically constrained optimization problem and has been designed to be a multi-purpose tool, like a Swiss army knife, that can be employed to study many different aspects of the e...

This paper introduces the full Low-carbon Expansion Generation Optimization (LEGO) model available on Github (https://github.com/wogrin/LEGO). LEGO is a mixed-integer quadratically constrained optimization problem and has been designed to be a multi-purpose tool, like a Swiss army knife, that can be employed to study many different aspects of the e...

To be effective, policies addressing power sector carbon emissions in jurisdictions that are embedded in larger carbon markets must account for carbon embodied in imports and the potential for leakage. Yet analyses of alternative border carbon adjustment (BCA) policies that carefully model the impact of generation mix, net load distributions, and t...

The combination of heat waves and urban heat “island” (UHI) and “archipelago” (UHA) effects can adversely impact the health of city residents. These impacts could be amplified in the future, with low-income communities most affected, and neighborhood-scale temperature data provide essential information for adaptation. In recent years, fixed and mob...

As more variable renewable energy (VRE) and energy storage (ES) facilities are installed, accurate quantification of their contributions to system adequacy becomes crucial. We propose a definition of capacity credit (CC) for valuing adequacy contributions of these resources based on their marginal capability to reduce expected unserved energy. We s...

Extensive efforts to adaptively manage nutrient pollution rely on Chesapeake Bay Program’s (Phase 6) Watershed Model, called Chesapeake Assessment Scenario Tool (CAST), which helps decision-makers plan and track implementation of Best Management Practices (BMPs). We describe mathematical characteristics of CAST and develop a constrained nonlinear B...

Close coordination between generation and transmission operations and planning is critical to cost effective and reliable energy production and delivery; such coordination, in the presence of ownership diversity, is indeed a primary and challenging goal of regional transmission organizations in the US and similar organizations worldwide. Optimizing...

A tool for planning grid reinforcements while recognizing how supply and storage investments will respond to the changed network is presented here. The model is formulated as a mixed-integer linear program that co-optimizes transmission–generation–storage expansion; in an unbundled market context, use of such a model by transmission owners is terme...

We investigate how the effectiveness of green infrastructure (GI) to mitigate the frequency and magnitude of significant discharge events and combined sewer overflows (CSOs) depend on both climate and sewershed characteristics and propose a theoretical framework for a holistic assessment of GI's efficacy. The framework is based on the comparison of...

Due to high in-channel sedimentation rates, the Yellow River Delta of China has changed course frequently in its history, with huge socioeconomic impacts. The following questions are addressed: What is the best timing and location of deliberate avulsions? Can temporary floodways lessen the cost and flooding impacts of avulsion strategies? To addres...

Optimization methods for regional transmission planning overlook boundaries between transmission planning entities and do not account for their lack of coordination. The practical result of those boundaries is inefficient plans because one planning region may disregard the costs and benefits that its network changes impose on other regions. We deve...

Climate adaptation decisions are difficult because the future climate is deeply uncertain. Combined with uncertainties concerning the cost, lifetime, and effectiveness of adaptation measures, this implies that the net benefits of alternative adaptation strategies are ambiguous. On one hand, a simple analysis that disregards uncertainty might lead t...

Policy makers across Europe have implemented renewable support policies with several policy objectives in mind. Among these are achieving ambitious renewable energy targets at the lowest cost, reducing CO2-emissions and promoting technology improvement through learning-by-doing. Using a detailed country-level model of generation markets, we address...

Near-optimal unit commitment (UC) scheduling is a practical reality in wholesale electricity markets. This paper revisits previous work that has found that minor differences in cost among near-optimal schedules can result in a large redistribution of market payments (i.e., changes in generator profits and consumer surplus). It has been believed tha...

Electrical layout and turbine placement are key design decisions in offshore wind farm projects. Increased turbine spacing minimizes the energy losses caused by wake interactions between turbines but requires costlier cables with higher rates of failure. Simultaneous micro‐siting and electrical layout optimization are required to realize all possib...

A framework to quantify the value of model enhancements (VOMEs) in transmission planning models is proposed and applied to a case study of the large‐scale, long‐term planning of the Western Electricity Coordinating Council (WECC) system. The VOME, which is closely related to the concept of the value of information from decision analysis, quantifies...

Policy, technology, and economic uncertainties affect the net benefits of grid reinforcements, and should be considered in planning. Stochastic optimisation can improve the robustness and expected performance of transmission plans, but is computationally intensive because model size grows as more scenarios are considered. Therefore, the ability to...

We developed a watershed sediment source and delivery model for use in evaluating conservation trade‐offs in southern Minnesota, where sediment loading has been identified as a priority and there is substantial public investment in cleaner water. The model was developed in a stakeholder process and links user‐specified management options to reducti...

This article demonstrates the benefits of simultaneous cooptimization on a 312-bus network representation of the Western Interconnection power grid with emphasis on The Bonneville Power Administration’s operational area in the Pacific Northwest. While generation and transmission expansion planning has traditionally been solved sequentially, simulta...

New generation, storage, demand management, and smart grid technologies have the potential to make the grid of 2050 very different from today's power system. Can market designers keep up, and what do they need to pay attention to now? Before offering a few answers to these questions, we first give some historical perspective on the creation of mark...

Also available in the Electricity Policy Research Group (EPRG) working paper series: https://www.eprg.group.cam.ac.uk/eprg-working-paper-1840/

This research models the drivers of emissions historically to identify the factors most effective in reducing power system emissions. It estimates the average effects of wind and load on \(\hbox {CO}_{2}\) emissions from the Republic of Ireland’s electricity market. The findings suggest that wind generation and load reduction are not equally effect...

Environmental quality has a profound effect on health and the burden of disease. In the United States, the environment-related burden of disease is increasingly dominated by chronic diseases. At the local level, public health practitioners realize that many policy decisions affecting environmental quality and health transcend the authorities of tra...

Some restructured power systems rely on audited cost information instead of competitive bids for the dispatch and pricing of electricity in real time, particularly in hydro systems in Latin America. Audited costs are also substituted for bids in U.S. markets when local market power is demonstrated to be present. Regulators that favor a cost-based d...

Two desirable properties of electricity market mechanisms include: i) revenue adequacy for the market, and ii) cost recovery for all generators. Previously proposed stochastic market-clearing mechanisms satisfy both properties in expectation only, or satisfy one property by scenario and another in expectation. Consequently, market parties may perce...

Food insecurity is a complex phenomenon with biophysical, climatic, economic, and infrastructure facets. Despite this understanding, there are few stakeholder-based modelling tools that can capture these dynamics and thereby evaluate the direct and indirect impacts that climatic change, economic change, and policy interventions can have on food sec...

We propose a Topographic Filtering simulation model (Topofilter) that can be used to identify those locations that are likely to contribute most of the sediment load delivered from a watershed. The reduced complexity model links spatially distributed estimates of annual soil erosion, high-resolution topography, and observed sediment loading to dete...

In Part II of this paper, we present formulations for three two-settlement market models: baseline cost-minimization (Stoch-Opt); and two sequential market models in which an independent system operator (ISO) runs real-time (RT) balancing markets after making day-ahead (DA) generating unit commitment decisions based upon deterministic wind forecast...

Part one of this two-part paper presents new models for evaluating flexible resources in two-settlement electricity markets (day-ahead and real-time) with uncertain net loads (demand minus wind). Physical resources include wind together with fast-and slow-start demand response and thermal generators. We also model financial participants (virtual bi...

As the penetration of variable renewable energy in electricity markets grows, there is increasing need for capacity markets to account for the contribution of renewables to system adequacy. An important issue is the inconsistent industry definition of capacity credits for resources whose availability may be limited, such as renewable generation. In...

Short-term electricity markets are generally defined as markets that take place from the day-ahead stage until physical generation and consumption. These markets include day-ahead, intra-day, and real-time balancing markets. In Europe, the first two are managed by power exchanges, while the third consists of reserve procurement and imbalance settle...

Approximations made in traditional day-ahead unit commitment model formulations can result in suboptimal or even infeasible schedules for slow-start units and inaccurate predictions of actual costs and wind curtailment. With increasing wind penetration, these errors will become economically more significant. Here, we consider inaccuracies from thre...

We investigate the effects of risk aversion on optimal transmission and generation expansion planning in a competitive and complete market. To do so, we formulate a stochastic model that minimizes a weighted average of expected transmission and generation costs and their conditional value at risk (CVaR). We show that the solution of this optimizati...

The dynamic economic dispatch problem with energy storage in a smart grid scenario is studied, which aims at minimising the aggregate generation costs over multiple periods on condition that the time-varying demand is met, while physical constraints on generation and storage as well as system spinning reserve requirement are satisfied. In our model...

Due to the increased penetration of intermittent renewables, operating reserves are becoming increasingly important in electricity markets. Coordinating the sizing, allocation and activation of reserves among market zones can decrease operational costs and enhance system reliability. However, network limitations constrain reserve coordination among...

Transmission planning has traditionally followed a “generation first” or “reactive” logic, in which network reinforcements are planned to accommodate assumed generation buildouts. The emergence of renewables has revealed deficiencies in this approach, in that it ignores the interdependence of transmission and generation investments. For instance, g...

This paper presents Nash equilibrium models of perfectly competitive capacity expansion involving risk-averse participants in the presence of state uncertainty and pricing mechanisms. Existence of solutions to such models is established based on the nonlinear complementarity formulations of the models to which a general existence result is applicab...

Electricity storage plants can be used for many applications, with one of the most studied applications being arbitrage in the day-ahead market. Although the arbitrage value is related to the presence of price spreads, it also depends on the effect of (dis)charge actions on prices, as arbitrage generally reduces price spreads by increasing off-peak...

Wind turbine spacing is an important design parameter for wind farms. Placing turbines too close together reduces their power extraction because of wake effects and increases maintenance costs because of unsteady loading. Conversely, placing them further apart increases land and cabling costs, as well as electrical resistance losses. The asymptotic...

The problem of whether, where, when, and what types of transmission facilities to build in terms of minimizing costs and maximizing net economic benefits has been a challenge for the power industry from the beginning-ever since Thomas Edison debated whether to create longer dc distribution lines (with their high losses) or build new power stations...

Focusing on the neighborhood where the Village of Arts and Humanities is, we have developed, evaluated, and tested a method for incorporating community input regarding ancillary green infrastructure (GI) benefits into a multi-objective GI optimization model. The model adapts the Stormwater Investment Strategy Evaluation (StormWISE) model for use in...

Power economic studies are challenging because of growing system sizes, the advance of smart grids, and economic, technical, and policy unknowns. Consequently, system models must be simplified so that they can be solved with many scenarios of renewable output, load, and long-run uncertainties. Scenario reduction, network aggregation, and DC lineari...

We model the economic incentives for market participants to cooperate in the development of a microgrid in a small electricity network served by a regulated utility. The microgrid can provide energy, ancillary services, heat and enhanced reliability to its customers. Using the framework of cooperative game theory, assuming exchangeable utility and...

Biofuel policy is under near constant review at both the federal and state level. For example, as part of on-going implementation of the California Low Carbon Fuel Standard (LCFS), the California Air Resources Board has recently designed and is implementing a new cost containment mechanism as part of the compliance credit market embedded within the...

Inappropriate waste disposal is a serious issue in many urban neighborhoods, exacerbating environmental, rodent, and public health problems. Governments all over the world have been developing interventions to reduce inappropriate waste disposal. A system dynamics model is proposed to quantify the impacts of interventions on residential waste relat...

We present a survey of US capacity market experts with the purpose of drawing lessons for the EU. Of the respondents, 41% advised EU member states against implementing capacity markets, while the remaining were neutral or provided suggestions for improving capacity markets. Cross-border effects are currently not a concern but may become so in the f...

We investigate the effects of risk aversion on optimal transmission and generation expansion planning in a competitive and complete market. To do so, we formulate a stochastic model that minimizes a weighted average of expected transmission and generation costs and their conditional value at risk (CVaR). We show that the solution of this optimizati...

As probability elicitation becomes widely used, methods other than one-on-one interviews are being used to elicit expert probabilities. This paper considers biases that may arise when probabilities are elicited in an online or workbook setting. We develop a prescriptive model in which the elicited probability is a convex combination of the expert’s...

Renewable energy was not the initial justification for electricity markets, but it is rapidly becoming a driver for new markets and market design changes. Starting in 1982 with market reforms in Chile, competition has been introduced into wholesale electricity markets around the world. This trend is likely to accelerate with countries such as China...

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 solutio...

We propose a novel two-phase bounding and decomposition approach to compute optimal and near-optimal solutions to large-scale mixed-integer investment planning problems that have to consider a large number of operating subproblems, each of which is a convex optimization. Our motivating application is the planning of power transmission and generatio...

We use a unit commitment (UC) model to quantify the operational impacts of subsidizing wind generation when energy prices are negative. Such prices occur increasingly often in U.S. and European Union (EU) markets. Subsidies such as production tax credits, feed-in tariffs, and renewable energy credits motivate renewable generators to submit negative...

Philadelphia’s Green City Clean Waters program is an innovative plan to reduce the frequency and environmental impact of combined sewer overflows through massive, citywide implementation of green infrastructure practices. The program has been approved by regulatory agencies based on the assumption that a variety of direct benefits and co-benefits w...

The growth of demand response programs and renewable generation is changing the economics of transmission. Planners and regulators require tools to address the implications of possible technology, policy, and economic developments for the optimal configuration of transmission grids. We propose a model for economic evaluation and optimization of int...

We examine the exercise of market power in California's power market in 1998-2000, with a focus on its day-ahead energy market and its five non-utility thermal generating companies. Our goal is to assess whether the hourly bids of market participants, together with information on thermal unit characteristics and power output, suggest that the five...

Markets for ramp products (called “flexiramp” in the California ISO and “ramp capability” in the Midcontinent ISO) have been proposed to address the need for generator flexibility due to increased renewable penetration. Flexiramp is committed capacity reserved to meet unexpected ramps in net load. We evaluate flexiramp market designs by comparing s...

Increases in greenhouse gas (GHG) emissions are the major cause of climate change (global warming), which poses a huge threat to our society in the foreseeable future. Development of a low-carbon economy has become prevailing and essential. Many countries throughout the world have been making their economy more climate-friendly and less GHG emissio...

Simulations of production costs, flows, and prices are crucial inputs to generation and transmission planning studies. To calculate average system performance for many alternatives over long time periods, it is necessary to simulate large numbers of hourly combinations of renewable production and loads across large regions. As this is usually impra...

The mathematical formulation of a strategic Eurasian natural gas market model is presented. The model represents horizontal oligopolistic relationships among producers, bilateral market power between producer (Russia) and transit (Ukraine) countries, detailed transport constraints, and operations decisions over a 20 year time horizon. To demonstrat...

U.S. Independent System Operators (ISOs) are creating short-run markets for so-called “flexiramp”. The aim of these markets is to ensure that enough flexible generation capacity is on-line to manage the increasingly volatile net loads resulting from growth in renewable energy. In particular, we assume that the purpose of flexiramp is to improve the...

The ability of load to respond to short-term variations in electricity prices plays an increasingly important role in balancing short-term supply and demand, especially during peak periods and in dealing with fluctuations in renewable energy supplies. However, price responsive load has not been included in standard models for defining the optimal s...