Vijay Modi

Vijay Modi
Columbia University | CU · Department of Mechanical Engineering

About

151
Publications
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4,114
Citations

Publications

Publications (151)
Article
Full-text available
In presenting an irrigation detection methodology that leverages multiscale satellite imagery of vegetation abundance, this paper introduces a process to supplement limited ground-collected labels and ensure classifier applicability in an area of interest. Spatiotemporal analysis of MODIS 250 m enhanced vegetation index (EVI) timeseries characteriz...
Preprint
Full-text available
A modeling framework is presented to investigate trade-offs among decarbonization from increased low-carbon electricity generation and electrification of heating and vehicles. The model is broadly applicable but relies on high-fidelity parameterization of existing infrastructure and anticipated electrified loads; this study applies it to New York S...
Article
A modeling framework is presented to investigate trade-offs among decarbonization from increased low-carbon electricity generation and electrification of heating and vehicles. The model is broadly applicable but relies on high-fidelity parameterization of existing infrastructure and anticipated electrified loads; this study applies it to New York S...
Preprint
Full-text available
In presenting an irrigation detection methodology that leverages multiscale satellite imagery of vegetation abundance, this paper introduces a process to supplement limited ground-collected labels and ensure classifier applicability in an area of interest. Spatiotemporal analysis of MODIS 250m Enhanced Vegetation Index (EVI) timeseries characterize...
Preprint
In low-income settings, the most critical piece of information for electric utilities is the anticipated consumption of a customer. Electricity consumption assessment is difficult to do in settings where a significant fraction of households do not yet have an electricity connection. In such settings the absolute levels of anticipated consumption ca...
Article
Electric sector capacity expansion models are widely used by academic, government, and industry researchers for policy analysis and planning. Many models overlap in their capabilities, spatial and temporal resolutions, and research purposes, but yield diverse results due to both parametric and structural differences. Previous work has attempted to...
Article
Electrification of heating and transportation is poised to disrupt the electric system by increasing distribution system peaks throughout the United States. This paper adds to the literature by describing the main determinants of electric distribution costs using data reported by 101 major U.S. investor-owned utilities and a set of empirical models...
Article
“Stay-at-home” orders and other health precautions enacted during the COVID-19 pandemic have led to substantial changes in residential electricity usage. We conduct a case study to analyze data from 390 apartments in New York City to examine the impacts of two key drivers of residential electricity usage: COVID-19 case-loads and the outdoor tempera...
Article
Residential electricity load profiles and their diversity have become increasingly important to realize the benefits of Smart or Transactive Energy Networks (TENs). An important element of TENs will be practical, accurate, and implementable residential load forecasting techniques. While there have been many approaches to short-term load forecasting...
Article
We propose a scalable computational framework to examine the effects of settlement patterns on the electrification of an entire country. We first propose a data processing strategy to convert structure locations, identified from satellite imagery, to estimated household locations using census data. Then, we present a computational framework that in...
Article
While past research has shown that providing residents with feedback about their electricity usage can reduce demand and its associated environmental burdens, some questions remain regarding what makes such feedback most effective. We followed the electricity usage of 36 residents who each received 14 feedback messages over 2 months. Using approach...
Article
Full-text available
Building electricity is a major component of global energy use and its environmental impacts. Detailed data on residential electricity use have many interrelated research applications, from energy conservation to non-intrusive load monitoring, energy storage, integration of renewables, and electric vs. fossil-based heating. The dataset presented he...
Article
Pumping of water for agriculture can be a flexible component of electric demand. In this study, a framework that involves scenario based stochastic programming models is developed to examine the effect of load shifting on the renewable energy system sizing for agricultural load. With the help of this framework, alternative load shifting policies ar...
Preprint
Full-text available
To extract information at scale, researchers increasingly apply semantic segmentation techniques to remotely-sensed imagery. While fully-supervised learning enables accurate pixel-wise segmentation, compiling the exhaustive datasets required is often prohibitively expensive. As a result, many non-urban settings lack the ground-truth needed for accu...
Article
We investigate implications of building space heating decarbonization pathways across the climate-diverse United States. We compute that an “all-electric” approach could require a 70% increase in nationwide electricity system capacity. New peak loads would be highly heterogeneous (e.g., 4-fold increase in some states) with very low load factors (fe...
Article
This study evaluates generation, transmission, and storage capacity needs to achieve deep renewable energy penetration in a regional electricity grid with an average load of approximately 20 GW. Increasing renewable energy targets are analyzed to evaluate the effects of realistic regional transmission upgrade and energy storage cost assumptions on...
Article
To reduce greenhouse gas emissions, the electricity sector is going through two main transitions. First, the electric grid is integrating variable renewable generation, such as wind and solar. Second, demands are changing as heating systems are shifting from gas-based to high efficiency electric heat pumps. This paper provides a comparative analysi...
Article
Increasingly, variable renewable energy capacity will be added distant from load centers in much of the world. How such intraregional heterogeneity in variable supply and load will impact the energy system in a deep renewable penetration scenario is studied here. Heterogeneous reliability requirements imposed by such scenarios are not well understo...
Article
During the past 5 years, electrification in Kenya has grown by more than 30% due primarily to increases in grid penetration and solar home systems. This represents a way forward for governments, international finance institutions, and entrepreneurs to address some of the challenges of energy access. However, little is understood about how consumpti...
Conference Paper
Soaring electricity demand from space cooling and excellent solar photovoltaics (PV) resources are creating an opportunity for the financial viability of low-emission solutions in Qatar that can compete with existing approaches. This study examines the big picture viability of combining large utility-scale PV with decentralized building-scale ice s...
Conference Paper
This paper explores the effects of energy system flexibility on the contribution of wind generation to the New York State (NYS) electricity generation mix. First, the benefits of NYS-specific flexible hydropower are investigated. For all simulations, a mixed integer linear program minimizes net load to determine the maximum aggregate capacity facto...
Article
Transition from fossil fuels to renewable sources is inevitable. In this direction, variation and intermittency of renewables can be integrated into the grid by means of hybrid systems that operate as a combination of alternative resources, energy storage and long distance transmission lines. In this study, we propose a two-stage stochastic mixed-i...
Article
For electric grids that rely primarily on liquid fuel based power generation for energy provision, e.g. one or more diesel gensets, measures to allow a larger fraction of intermittent sources can pay-off since the displaced is high cost diesel powered generation. This paper presents a case study of Sao Vicente, located in Cape Verde where a particu...
Article
As the tropics and subtropics become increasingly urban, industrial and affluent, energy demands for thermal comfort may evolve differently than it has historically across the global North. Already, heating, ventilation and air conditioning account for 35% of total primary energy in the United States, and are expected to reach similar proportions i...
Article
This paper reports estimates of average GHG emissions factors for New York State and marginal GHG emissions factors for interventions in New York City. A multi-regional unit commitment model was developed to simulate the behavior of the grid. The parameters defining the system operation were gathered from several publicly available data sources inc...
Article
This work aims to elucidate notions concerning the ideal operation and greenhouse gas (GHG) emissions benefits of combined heat and power (CHP) systems by investigating how various metrics change as a function of the GHG emissions from the underlying electricity source, building use type and climate. Additionally, a new term entitled “CHP Attributa...
Article
Many US states have targets for vastly expanding electricity generation from renewable resources. As installed wind capacity increases, several factors can lead to the curtailment of potential wind-generated electricity. Reliably estimating wind power outputs remains a challenge given the dearth of available hub height-altitude wind speed data and...
Article
As the size of buildings and demands on large centralized heating and cooling systems increases concurrent with rapid worldwide urbanization, the energy impact of hydronic distribution systems will become increasingly important in reducing greenhouse gas emissions. Further, in the U.S., the growth in multi-family buildings and the share of resident...
Article
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 hy...
Conference Paper
Service delivery whether that of health or education, or that of electricity or water, remains a challenge in the developing world context. There are a variety of reasons this is the case much attention has been paid to the supply-side as in creating more facilities for service or developing sources such as water and energy. In this paper a nuanced...
Article
The U.S. has substantial wind power potential, but given wind’s intermittent availability and misalignment with electricity demand profiles, large-scale deployment of wind turbines could result in high electricity costs due to energy storage requirements or low utilization rates. While fuel switching and heat pumps have been proposed as greenhouse...
Article
In many low-income settings and geographies it's not immediately feasible to deploy central power generation with electric grids. In this context, off-grid approaches like solar home systems (SHS) are gaining wide acceptance. Since battery storage costs are the dominant costs, the value proposition of using a novel mini-grid with shared generation/...
Conference Paper
Full-text available
Is functionality of electricity, sanitation and water infrastructure at schools unequally distributed geographically in Nigeria? Are there significant disparities in infrastructure functionality between Northern and Southern geopolitical zones in the country as has been posited in previous studies? In this study, we answer these questions with an e...
Article
In 2007, Nigeria made history by launching the Conditional Grants Scheme (CGS), one of the world's largest poverty elimination campaigns aimed at achieving the Millennium Development Goals (MDGs) by 2015. As part of CGS, the Office of the Senior Special Assistant to the President of Nigeria on the MDGs (OSSAP-MDGs) collaborated with The Earth Insti...
Article
For many isolated regions in the developing world micro-grids which combine photovoltaic electricity generation and battery storage may represent the most reliable and least expensive form of energy service. Due to climate induced solar resource variations, achieving high reliability levels necessitates excess generation and storage capacity which...
Conference Paper
Building energy contributes approximately 40% of U.S. greenhouse gas emissions and 75% of emissions in some urban areas. Evaluating modifications to existing building stocks is essential to a proper assessment of GHG reduction policy at various levels. With deeper penetration of intermittent renewable energy resources, supply and demand effects at...
Conference Paper
As cities have begun to implement greenhouse gas initiatives, one technology that has become of interest is building level combined heat and power (CHP). In New York City, over two thirds of greenhouse gas emissions are attributed to buildings. As space heating is the major end use of building energy consumption in the Northeast, building level CHP...
Technical Report
Recently, significant reserves of natural gas have been identified in Mozambique and Tanzania. These resources may support a pathway to both economic growth and a low-carbon future. This natural gas could be used locally for a host of different applications such as cooking, power generation, transportation and fertilizer production. The aim of this...
Article
In this study, the Network Planner, a decision support tool for exploring costs of different electrification technology options in un-electrified communities, was used to model costs and other inputs for providing electricity to 2600 un-electrified communities in Ghana within a 10-year planning period. The results show that the cost-optimized optio...
Article
Combined Heat and Power (CHP) has been proven as a mature technology that can benefit both building owners and utility operators. As the economic and environmental benefits of CHP in urban centers gain recognition, regulations and policies have evolved to encourage their deployment. However, the question remains whether these policies are sufficien...
Article
This paper analyzes the optimal options for supplying electricity to national economies from both domestic and distant energy resources using high voltage lines to transmit the substantial renewable energy resources of Africa. To meet the growing demand, Africa will need to provide 5.2 GW of new generation per year through 2025. This figure represe...
Article
The provision of energy services–such as illumination, thermal comfort, cooking, communications and mobility–is critical to both social and economic good. But the use of fossil fuels in meeting these needs can also lead to higher greenhouse gases emissions, potentially becoming a threat to our well-being. Ironically, the greatest threat is to under...
Conference Paper
Full-text available
Feedback based on real-time data is increasingly important for ICT-based interventions in the developing world. Applications such as facility inventories, summarization of patient data from community health workers, etc. need processes for analyzing and aggregating datasets that update over time. In order to facilitate such processes, we have creat...
Article
We present the design and simulation of first-ever planar single-element solar lenses (modified hemispherical gradientindex structures) for concentrator photovoltaic applications, with high collection efficiency and liberal optical tolerance at averaged cell irradiance levels exceeding 1000 suns. These compact lens designs satisfy the severe constr...
Conference Paper
Reaching unelectrified populations in the developing world with distributed solar requires agressive cost optimization of generation and storage. Conventional solar generation architectures using photovoltaic panels, sealed lead acid batteries, and inverters show room for cost improvement. Using data collected from photovoltaic microgrid users and...
Article
This paper summarizes the main findings regarding household energy use from nearly 3000 households across 10 different rural agro-ecological locations in Sub-Saharan Africa. The data were collected with a baseline energy survey as part of the Millennium Villages Project, a multi-sectoral development effort. The results document the households' reli...
Article
We describe the first heuristic algorithm that selects the locations and service areas of transformers without requiring candidate solutions and simultaneously builds two-level grid network in a green-field setting. The algorithm we propose minimizes overall cost of infrastructure costs; specifically the combined costs of transformers and the two-t...
Conference Paper
The energy potential from wind is significant in many locations in the U.S., including in some areas of New York State. The intermittent availability of wind — specifically, higher wind potential at night and in the winter in New York — would require extensive storage to make use of that energy during times of peak electricity demand — during the d...
Conference Paper
Combined heat and power (CHP) has the potential to decrease greenhouse gas emissions by utilizing waste heat that is typically rejected to the environment. CHP systems have been used to satisfy loads on university and corporate campuses but there may be other clusters of mixed used buildings that are viable for a CHP system. In an urban environment...
Conference Paper
The implementation of wind power forecast technology considerably accelerates the development of wind energy utilization. However, wind power is difficult to be accurately forecasted due to its intermittency and randomness. Meanwhile, a classic prediction system usually could not provide the uncertainty of the predicted wind power so that the suspi...
Article
The design of single element planar hemispherical gradient-index solar lenses that can accommodate the constraints of realistic materials and fabrication techniques are presented, and simulated with an extended and polychromatic solar source for concentrator photovoltaics at flux concentration values exceeding 1000 suns. The planar hemispherical fa...
Article
This paper demonstrates a model for electricity delivery and revenue collection in a rural context with the potential to increase the reliability of service delivery and lower operating costs compared to traditional fixed monthly fee utilities. The microutility in this paper provides power on a pre-paid basis similar to the way cellular phone air-t...
Article
To achieve the Millennium Development Goals (MDG), all households in sub-Saharan Africa will need to have access to basic infrastructure services. The challenge in meeting this goal is in bringing this access while simultaneously driving down the costs. With an understanding of cost drivers and the implications of achieving scale it becomes possibl...
Article
Highlights ► In order to achieve the multiple objectives of the energy system transformation, implementation of a large number of systems changes would need to begin today. ► Integrated policies in aid of these objectives can have important synergies. ► Formulating a long-term vision with respect to the energy system is important, given the critica...
Article
The provision of modern energy services is recognised as a critical foundation for sustainable development, and is central to the everyday lives of people. Effective policies to dramatically expand modern energy access need to be grounded in a robust information-base. Metrics that can be used for comparative purposes and to track progress towards t...
Article
Novel solutions for realistic gradient-index (GRIN) lenses are presented, that create the possibility of nominally stationary photovoltaic concentrators capable of daylong averaged flux concentration levels of order 103. One transfers the burden of precision solar tracking from massive units on which numerous solar modules are mounted, to miniaturi...
Article
Certain classes of gradient-index lenses can achieve both perfect imaging and flux concentration at the fundamental limits. Although useful in microwave technology, eponymous Luneburg lenses have been viewed as esoteric idealizations for visible and near-infrared radiation due to the paucity of suitable materials and fabrication methods. We show th...
Article
Fundamentally new classes of spherical gradient-index lenses with imaging and concentration properties that approach the fundamental limits are derived. These analytic solutions admit severely constrained maximum and minimum refractive indices commensurate with existing manufacturable materials, for realistic optical and solar lenses.
Article
It is shown how novel solutions for realistic gradient-index lenses create the possibility of nominally stationary solar photovoltaic concentrators capable of daylong averaged flux concentration levels of order 10(3).
Article
An accurate understanding of the factors that influence farmers’ adoption of a crop is critical for effective policy promotion and technical support. Agroforestry crop adoption is a complex topic involving many factors not often addressed by tradition crop adoption models. This complexity, when applied to Jatropha (Jatropha curcas L.), an often wid...
Article
The current energy distribution infrastructure in many urban areas either cannot support anticipated future energy use or would require significant rehabilitation even if current use were maintained. Understanding the dynamics of local energy use is an important precondition of understanding how to remedy this situation. This paper builds a model t...
Article
Though many plant oils have a similar energy density to fossil diesel fuel, several properties of plant oils are considerably different from those of diesel. Engine modifications can overcome some of these differences. An engine modification kit has been designed and tested for a slow speed, stationary, indirect-injection diesel engine – the Lister...
Article
A novel approach for the design of refractive lenses is presented, where the lens is mounted on a stationary aperture and the Sun is tracked by a moving solar cell. The purpose of this work is to design a quasi-stationary concentrator by replacing the two-axis tracking of the Sun with internal motion of the miniaturized solar cell inside the module...
Article
This paper presents the results of two studies conducted to evaluate the performance and usability of household biomass cookstoves under field conditions in rural sub-Saharan Africa. Cooking tests and qualitative surveys compared improved, manufactured stove models based on the ‘rocket’ design with the traditional three-stone fire. All tests and in...
Article
Cooking tests were conducted in randomly selected school kitchens in the Sauri Millennium Villages Project site, located in Siaya District of Nyanza Province in Western Kenya. The tests compared fuel consumption measurements obtained using a traditional three-stone fire with those from newly introduced institutional stoves based on the “rocket” des...
Article
Many short-run studies point to the potential for direct fueling of compression ignition engines with plant oil fuels. There is a much smaller body of work that examines the potential for these fuels in long-run tests that illuminate engine endurance and longevity issues. Generally, longevity studies involving direct fueling of engines with straigh...
Article
This paper presents a novel approach regarding the design of stationary, non imaging, refractive lenses with high acceptance angles. A lens lies on a stationary aperture and as the sun moves throughout the day, the concentrated focal spot is tracked by a moving solar cell. The purpose of this work is to replace the 2-axis tracking of the sun with i...
Article
Lanterns that use light-emitting diodes (LEDs) powered by batteries, which are in turn charged by grid electricity or small solar panels, have emerged as a cost-competitive alternative to kerosene and other fuel-based lighting technologies, offering brighter light for longer duration at equal or lower cost over time. This paper presents lessons lea...
Article
If solar power is to provide substantial portions of our electricity needs, it will first become cost effective when it provides peak power in the daytime, without the need for storing the energy. Indeed since human electricity consumption is frequently small at night and larger when the sun is shining, there is already a natural correlation. Exist...