Introduced in this document is a combination of research published by our university cluster. It outlines the requirements for an ultra-fast response system to correct generation/load imbalances on timescales that could be considered virtual inertia. Much of the research is based on real power system measurements and lab experiments, supplemented by computational models. The work has been tailored to the Irish power system that is facing a low inertia threshold, limiting the utilization of renewable generation. Ireland is taken as a test case for the necessary road other power system will need to take as they integrate converter interfaced renewable generation. At present Ireland has the objective to decarbonize its power system by 2050; as anyone who has read the IPCC 2018 summary will appreciate, this is far too late and if preparatory research is not undertaken, projects may be rushed.
Electric sector emissions represent a large and growing fraction of anthropogenic emissions and should be a strong focus for environmental policy measures. In electric grids with significant penetrations of renewables, the emissions intensity of electricity varies in space and time. To encourage and guide decarbonization efforts, we need better tools to monitor the emissions embodied in electricity consumption, production and exchanges. Previous efforts resulted in a dataset for 2016 electricity and emissions at the hourly and balancing – area levels in the US electricity system. We now provide tools to make such datasets available much faster, by using a n approximation for released emissions and an algorithm to automate data cleaning. A s an example of how this type of new, detailed information on the electricity system can be used, we assess the current impacts of high penetrations of renewables on other grid components in the US. We demonstrate how dispatchable generation and electricity exchanges play an essential role in integrating fluctuating wind and solar generation.
This paper evaluates data from 10 centrifugal pumps in a large wastewater treatment facility to illustrate the impact of pump design, selection, maintenance, and operation on system efficiency. The paper explores the efficiency impact of several interventions and qualitatively presents trade-offs to implementation. Of the interventions explored, energy savings up to 3% were identified representing 239,000 kWh annually.
For the past five years, the Department of Energy’s Co-Optima program has explored biomass-derived blendstocks with fuel properties that boost the efficiency of engines, seeking to enable technology for fuel-engine co-optimization. Past analysis quantified benefits of introducing co-optimized fuels and engines for light-duty vehicles with the core assumption that efficiency gains would be the same for vehicles with and without hybridized power trains. Vehicles with hybridized powertrains, however, could experience a different energy efficiency change than conventional vehicles, which could be a decrease, if the blended fuel is not tailored for their operation, or an increase, if the hybrid engine’s operational conditions take better advantage of the blended fuel. Therefore, this study examines opportunities to reduce the environmental effects of light-duty transportation when fuel properties are tailored to the unique needs of hybrid electric and plug-in hybrid electric (HEV, PHEV) vehicles to improve their engine efficiency. The analysis tracks greenhouse gas emissions reductions on a well-to-wheels basis when co-designed fuels and engines for vehicles with hybridized power trains are introduced into the market. Engine efficiency gains and incremental vehicle cost are key parameters in the analysis as we seek fuel-engine technology that will significantly boost overall vehicle efficiency at a price point that is commercially viable. Twelve co-deployment scenarios were generated based on 3 different levels of engine efficiency improvement (8% ,10% and 12%) and 4 level incremental costs ($100, $250, $500 and $1000) and the corresponding environmental effects are tracked as the technologies gain market adoption. The preliminary results show that the effect of incremental cost and efficiency gain on vehicle sales indicates that adoption of co-optimized HEV, and PHEVs are relatively insensitive to incremental vehicle purchase costs up to $250. In addition, the results indicate higher adoption of co-optimized HEVs at $100 and $250 price increase and 12% efficiency gain while the adoption of HEVs and PHEVs across other scenarios remain consistent. From the best-case scenario ($100, vehicle price increase and 12% engine efficiency increase), the result shows that using biofuels with tailored properties and advanced engines to achieve an increase hybridized engine efficiency could translate to 17.5% reduction in greenhouse gas emissions from the light duty vehicle fleet including non-hybridized vehicles in 2050.
Modern active distribution grids are characterized by the increasing penetration of distributed energy resources (DERs). The proper coordination and scheduling of a large numbers of these small-scale and spatially distributed DERs can only be achieved at the nexus of new technological approaches and policies. As such, this paper presents a distributed optimal power flow formulation for the distribution grid, applied to the problem of Volt-VAR optimization (VVO). First, we propose a convex model to describe the power physics of distribution grids of meshed topology and unbalanced structure, based on current injection and McCormick Envelopes. Second, we employ the distributed proximal atomic coordination (PAC) algorithm, which has several advantages over other distributed algorithms, including reduced local computational effort and improved privacy. We implement VVO by optimally coordinating DERs including PV smart inverters and demand response. Results from the IEEE-34 bus network are presented, under different DER penetration scenarios and using different VVO objective functions. Our results show the need for DER coordination to achieve desired grid performance. Finally, we discuss the extension of such an optimal power flow formulation to the development of market derivatives to provide financial compensation to DERs providing grid services such as reactive power support and voltage support, within a local retail market framework.
Liquid fossil fuels (1) enable transportation and (2) provide energy for mobile work platforms and (3) supply dispatchable energy to highly variable demand (seasonal heating and peak electricity). We describe a system to replace liquid fossil fuels with drop-in biofuels including gasoline, diesel and jet fuel. Because growing biomass removes carbon dioxide from the air, there is no net addition of carbon dioxide to the atmosphere from burning biofuels. In addition, with proper management, biofuel systems can sequester large quantities of carbon as soil organic matter, improving soil fertility and providing other environmental services. In the United States liquid biofuels can potentially replace all liquid fossil fuels. The required system has two key features. First, the heat and hydrogen for conversion of biomass into high-quality liquid fuels is provided by external low-carbon energy sources–nuclear energy or fossil fuels with carbon capture and sequestration. The potential quantities of liquid biofuels are much smaller if biomass is used as (1) the carbon feedstock and (2) the source of energy for the conversion process. Using external energy inputs can almost double the energy content of the liquid fuel per unit of biomass feedstock by fully converting the carbon in biomass into a hydrocarbon fuel. Second, competing effectively with fossil fuels requires very large biorefineries—the equivalent of a 250,000 barrel per day oil refinery. This requires commercializing methods for converting local biomass into high-density storable feedstocks that can be economically shipped to large-scale biorefineries. Large-scale biorefineries also enable efficient coupling of nuclear reactors to the biorefinery.
Growing interest in greenhouse gas mitigation strategies to address global climate change has resulted in the rapid expansion of renewable electricity sources. Increasing energy generation from variable renewable electricity sources, such as solar photovoltaics and wind turbines, has made balancing electricity supply and demand across the power grid more challenging. Some grid management challenges include sharp ramp up needs when the sun goes down, and the overgeneration of renewables when demand is low. In absence of cost-effective, utility-scale batteries, demand response strategies that leverage flexibility in electricity consumption have gained interest as readily available resources to address the temporal mismatch between renewable energy availability and high energy demand periods. The water industry (i.e., water supply and wastewater systems) includes industrial customers that are particularly attractive in terms of demand response potential as they can offer flexibility through large water storage capacities, large interruptible pumping loads, and energy generation opportunities. This study highlights an illustrative case in California to demonstrate the emissions benefits of load shifting in the water industry, followed by discussions regarding potential flexibility opportunities based on the recent literature and directions for future research opportunities to support the implementation of flexibility measures.
Due to the environmental impacts brought by current energy schemes, the energy transition, a new paradigm-shift from fossil fuels to renewable energy, has been widely accepted and is being realized through collective international and local efforts. Electricity, as the most direct and effective use of renewable energy sources (RES), plays a key role in the energy transition. In this paper, we first discuss a viable pathway to energy transition through the electricity triangle, highlighting the role of RES in electricity generation. Further, we propose methodologies for the planning of wind and solar PV, as well as how to address their uncertainty in generation expansion problems. Finally, by using a web-based tool, “RES-PLAT” 1 , we demonstrate the scheme in a case study of the North Africa, which evaluates the impacts and benefits of a large-scale RES expansion.
In order to reveal the supersonic condensation characteristics of carbon dioxide (CO2) in natural gas under low temperature condition, the mathematical models and numerical schemes for the CH4-CO2 mixture gas under supersonic flow condition were established, and the influence of inlet CO2 concentration on the CO2 removal efficiency of Laval nozzle was investigated. The results show that with the increase of CO2 concentration at nozzle inlet, the initial nucleation position is closer to nozzle throat, the maximum nucleation rate and the droplet number decrease but the droplet radius increases significantly, which eventually leads to an increase in liquefaction rate. When the inlet CO2 mole fraction is lower (less than 10%), the CO2 fraction in gas phase is almost 0, which indicates that low-temperature separation technology is practicable for the removal of CO2 from natural gas.
Liquid droplet radiator (LDR) is characterized by the compact arrangement and the low mass per unit power. It is a promising cooling system for the high-power spacecraft. The characteristics of the droplet layer in LDR determine the performance of the heat dissipation. Thus, the study of the droplet radiation heat transfer mechanism is vitally important for the optimal design of the whole LDR system. In the present paper, the radiation heat transfer characteristics of a sparse LDR system are studied from the aspects of the single droplet. The results reveal that the smaller the droplet radius is, the higher the droplet radiation energy per unit mass is. The slower the initial emission speed is, the higher the radiation energy per unit mass is. The higher the initial temperature of the droplet, the higher energy of radiation power per unit mass of the droplet is. Meanwhile, the radiation heat transfer characteristics of different working mediums are also given. These conclusions can provide basis for the optimal design of the sparse droplet radiators and provide guidance for the subsequent research on LDR.