281 research outputs found
A Review of Lithium-Ion Battery Models in Techno-economic Analyses of Power Systems
The penetration of the lithium-ion battery energy storage system (BESS) into
the power system environment occurs at a colossal rate worldwide. This is
mainly because it is considered as one of the major tools to decarbonize,
digitalize, and democratize the electricity grid. The economic viability and
technical reliability of projects with batteries require appropriate assessment
because of high capital expenditures, deterioration in charging/discharging
performance and uncertainty with regulatory policies. Most of the power system
economic studies employ a simple power-energy representation coupled with an
empirical description of degradation to model the lithium-ion battery. This
approach to modelling may result in violations of the safe operation and
misleading estimates of the economic benefits. Recently, the number of
publications on techno-economic analysis of BESS with more details on the
lithium-ion battery performance has increased. The aim of this review paper is
to explore these publications focused on the grid-scale BESS applications and
to discuss the impacts of using more sophisticated modelling approaches. First,
an overview of the three most popular battery models is given, followed by a
review of the applications of such models. The possible directions of future
research of employing detailed battery models in power systems' techno-economic
studies are then explored
MODELING AND ASSESSING THE SUSTAINABILITY OF DISTRIBUTED SOLAR PHOTOVOLTAICS ADOPTION
Participation of distributed solar photovoltaic (PV) generation in the organized electricity wholesale market is expected to increase under the Federal Energy Regulatory Commission Order 2222 announced in 2020. Our understanding about the technical, economic, and environmental tradeoffs and co-benefits of solar PV adoption on both building and regional scales remains limited, especially considering the complexity of varied distributed solar PV-battery system designs and operation strategies as well as the dynamic interactions of these distributed generations with the centralized grid. This dissertation therefore aims to investigate the grid load reduction, life cycle cost, and life cycle environmental (e.g., carbon, water, and energy footprints) performances of typical distributed PV systems considering their dynamic interactions with the centralized grid. This dissertation intends to examine the possible scenarios in which future adoption of PV systems can facilitate economic saving, reduce environmental footprints, relieve centralized grid stress, and supplement differential electricity demands of residential energy users on both building and city scales. To this end, a modeling framework was developed consisting of a stochastic residential electricity demand model, a system dynamics model of solar energy generation, energy balance, storage, and selling, and life cycle economic and environmental assessment model. The stochastic residential electricity demand simulation considered five typical types of household occupants and eight types of households. The generated solar energy, grid supply, and residential demand were balanced for each residential building using energy balance model. This model was further scaled up to a city level using Boston, MA as a testbed. On the building level, we found a clear tradeoff between the life cycle cost and environmental savings when sizing the PV systems differently. Moreover, installing a solar PV-battery system but without an effective control strategy can result in sub-optimized peak-load reduction, economic, and environmental outcomes. Installing solar PV-battery systems with proper controls can achieve the highest on-peak load reductions and economic benefits under the time-of-use utility rate design. However, they do not necessarily provide the highest environmental benefits, indicating a potential technical, environmental, and economic tradeoff. Our regional analysis found a large penetration of solar PV systems may result in a steeper ramp-up of the grid load during winter days, but it may provide load-shedding benefits during summer days. Large buildings may perform the best technically and environmentally when adopting solar PV systems, but they may have higher life cycle costs
MODELING AND ASSESSING THE SUSTAINABILITY OF DISTRIBUTED SOLAR PHOTOVOLTAICS ADOPTION
Participation of distributed solar photovoltaic (PV) generation in the organized electricity wholesale market is expected to increase under the Federal Energy Regulatory Commission Order 2222 announced in 2020. Our understanding about the technical, economic, and environmental tradeoffs and co-benefits of solar PV adoption on both building and regional scales remains limited, especially considering the complexity of varied distributed solar PV-battery system designs and operation strategies as well as the dynamic interactions of these distributed generations with the centralized grid. This dissertation therefore aims to investigate the grid load reduction, life cycle cost, and life cycle environmental (e.g., carbon, water, and energy footprints) performances of typical distributed PV systems considering their dynamic interactions with the centralized grid. This dissertation intends to examine the possible scenarios in which future adoption of PV systems can facilitate economic saving, reduce environmental footprints, relieve centralized grid stress, and supplement differential electricity demands of residential energy users on both building and city scales. To this end, a modeling framework was developed consisting of a stochastic residential electricity demand model, a system dynamics model of solar energy generation, energy balance, storage, and selling, and life cycle economic and environmental assessment model. The stochastic residential electricity demand simulation considered five typical types of household occupants and eight types of households. The generated solar energy, grid supply, and residential demand were balanced for each residential building using energy balance model. This model was further scaled up to a city level using Boston, MA as a testbed. On the building level, we found a clear tradeoff between the life cycle cost and environmental savings when sizing the PV systems differently. Moreover, installing a solar PV-battery system but without an effective control strategy can result in sub-optimized peak-load reduction, economic, and environmental outcomes. Installing solar PV-battery systems with proper controls can achieve the highest on-peak load reductions and economic benefits under the time-of-use utility rate design. However, they do not necessarily provide the highest environmental benefits, indicating a potential technical, environmental, and economic tradeoff. Our regional analysis found a large penetration of solar PV systems may result in a steeper ramp-up of the grid load during winter days, but it may provide load-shedding benefits during summer days. Large buildings may perform the best technically and environmentally when adopting solar PV systems, but they may have higher life cycle costs
Design and Analysis of Solar-powered E-bike Charging Stations to Support the Development of Green Campus
Currently, conventional motorcycles that utilize hazardous fossil fuels are expanding rapidly in Indonesia's major cities. Especially in campus environments, the increase in motorcycle usage has the potential to raise emissions of greenhouse gases and toxic microparticles. The green campus concept entails that campus living must implement low-emission energy efficiency, conserve resources, and enhance environmental quality by teaching its residents how to live a healthy lifestyle. However, limiting the number of motorcycles on campus is the main challenge, especially in Indonesia. To overcome this challenge, this study provides a design for the e-bike system that will be implemented at Universitas Muhammadiyah Yogyakarta (UMY). In addition, a solar power plant is integrated into the design to support the adoption of the zero-emission green energy concept on the campus. The design accommodates specifications for a 6 km radius surrounding the school, a two-day lifespan, and 100 electric bicycles. The experiment's findings indicate that the solar-powered e-bike design requires 99 solar panels with a capacity of 150 Wp, 9 SSCs with a capacity of 100 A, and three inverters with a capacity of 2,500 W. It is projected that this device will reduce exhaust emissions by 7.62 tons of CO2 per year once it is entirely operated
Interconnection of solar home systems as a path to bottom-up electrification
Solar Home Systems (SHSs) have revolutionised electricity access for off grid communities, but have a number of significant limitations. They have limited demand diversity, produce excess energy and lack a clear pathway to scale alongside growing energy demand.
Electrical interconnection of existing installed SHSs to create minigrids could offer a way to both scale up energy demand and make use of wasted energy. This bottom-up approach has the potential to be flexible to the changing needs of communities, by using SHSs as a starting point for wider electrification, rather than the end goal. Despite this potential, little analytical work has been undertaken to model SHS interconnection, particularly accounting for demand diversity and long-term system performance.
This thesis presents a time sequential stochastic model of interconnected SHSs, to investigate these systems under multi-year operational timescales at high temporal resolution. It is shown for case study systems based on real SHS topologies that there exists significant demand diversity, with small clusters of 20 houses with identical appliances exhibiting an average peak demand of less than 70% of the combined worst-case peak for individual SHSs. Excess generated energy is shown to be an average of 100 Wh a day for the smaller system types and 1000Wh a day for larger systems.
Interconnection of these systems demonstrates a significant reductions in LCOE for all system types compared to islanded operation, through more optimal dispatch of battery storage assets and use of excess energy. This resulted in a final LCOE of 0.703/kWh for a network of 12 small SHSs - a reduction of 55.23% compared to islanded operation. This informed an investigation of possible operational business models for a network of SHSs, with three approaches proposed - an Energy System Operator with direct control over all users’ systems, an Aggregator model, where the system operator facilitates an energy market and a Peer-to-Peer model with direct consumer to consumer energy trading.
This thesis provides a robust evidence base for SHS interconnection – demonstrating that the approach can lower cost of energy and facilitate demand growth for off grid energy consumers and proposes appropriate business models to deliver this affordable and clean energy.Solar Home Systems (SHSs) have revolutionised electricity access for off grid communities, but have a number of significant limitations. They have limited demand diversity, produce excess energy and lack a clear pathway to scale alongside growing energy demand.
Electrical interconnection of existing installed SHSs to create minigrids could offer a way to both scale up energy demand and make use of wasted energy. This bottom-up approach has the potential to be flexible to the changing needs of communities, by using SHSs as a starting point for wider electrification, rather than the end goal. Despite this potential, little analytical work has been undertaken to model SHS interconnection, particularly accounting for demand diversity and long-term system performance.
This thesis presents a time sequential stochastic model of interconnected SHSs, to investigate these systems under multi-year operational timescales at high temporal resolution. It is shown for case study systems based on real SHS topologies that there exists significant demand diversity, with small clusters of 20 houses with identical appliances exhibiting an average peak demand of less than 70% of the combined worst-case peak for individual SHSs. Excess generated energy is shown to be an average of 100 Wh a day for the smaller system types and 1000Wh a day for larger systems.
Interconnection of these systems demonstrates a significant reductions in LCOE for all system types compared to islanded operation, through more optimal dispatch of battery storage assets and use of excess energy. This resulted in a final LCOE of 0.703/kWh for a network of 12 small SHSs - a reduction of 55.23% compared to islanded operation. This informed an investigation of possible operational business models for a network of SHSs, with three approaches proposed - an Energy System Operator with direct control over all users’ systems, an Aggregator model, where the system operator facilitates an energy market and a Peer-to-Peer model with direct consumer to consumer energy trading.
This thesis provides a robust evidence base for SHS interconnection – demonstrating that the approach can lower cost of energy and facilitate demand growth for off grid energy consumers and proposes appropriate business models to deliver this affordable and clean energy
Optimal Energy Management Modelling Of A Grid-Connection Micro-Hydrokinetic With Pumped Hydro Storage
ThesisThe pressure on greenhouse gases (GHGs) emission reduction and energy deficit crisis are of global concern. The ever increasing energy demand due to population growth as well as industrial and commercial business developments, leads to energy deficit crisis for electric utility operators around the globe. This generates an increased probability of grid instability and blackout challenges. Hence, this promotes the requirement for the additional fossil fuel power plants, leading to electricity price increase for consumers, due to high investment cost and the rising fossil fuels prices. The exploitation of an onsite grid-connected renewable energy (RE) system may mitigate all of the above-mentioned challenges.
However, the intermittent nature of RE resources (such as solar, wind, hydro, geothermal and marine) leads to a challenge of high uncertainty output power. Hence, power demand cannot be reliably met, due to daily or seasonal weather changes. Therefore, a stand-alone RE system should comprise of an energy storage system (ESS), to store surplus energy for later use when the power demand is more than the generated output power. Additionally, a grid-interactive RE system should also comprise of the ESS, due to the variable tariff rates imposed by utility companies around the globe. The aim is to store excess energy during low-priced off-peak periods, for later use during high-priced peak periods. Hence, minimal electricity bill may be achieved by the consumers. The utility grid operator may also reap a benefit of a reduced blackout probability, especially during peak demanding periods.
Among various RE technologies, hydrokinetic is a promising RE solution to be exploited in areas with flowing water resources, such as rivers, tidal current or artificial water channels. It is easily predictable and has proved to generate electricity at flowing water speeds, ranging from 0.5 m/s and above. It has proved to generate electricity markedly better and affordable than solar and wind energy systems. Furthermore, it has proved to operate cost-effectively, if it comprises of a pumped-hydro storage (PHS) system instead of a battery-based storage system.
Rural consumers, such a farms, industries and mines situated in close proximity to flowing water resources, may make use of a grid-connected micro-hydrokinetic-pumped-hydro-storage (MHK-PHS) system to reduce electricity bills and sell the excess energy to the grid. However, a grid-connected MHK-PHS system requires a complex optimal energy management system, instead of expecting a consumer to respond to a change in real-time electricity price. The system should allow for optimal energy storage and sales, while ensuring that the consumer load demand is met at all times, by considering variable time-of-use (TOU) tariffs and load demand uncertainties that might take place in real-time context.
This work deals with optimal energy management of a grid-connected MHK-PHS system, under different demand seasons for different load demand sectors, through the consideration of variable TOU tariffs. The aim is to minimize the customer electricity bills if the proposed system is approved to be non-interactive or interactive with the utility grid. Additionally, the alternative aim is to maximize the energy sales into the grid, if the system is grid-interactive.
The results have proved that the developed optimization-based model is capable of minimizing the grid-cost, particularly during expensive peak-periods. Furthermore, the energy sales revenue has been maximized during peak-periods. Sundays have proved to lead to the largest amount of grid-power storage into the storage system, as compared to other days of the week. The industrial load profile led to the low net income, since most energy sales take place during the evening peak hours, instead of morning peak hours.
However, if the load demand uncertainty constraint is considered, the above-mentioned open-loop optimization-based model has been unable to optimize the power flow. This led to the unmet load demand difficulty, as well as the excessive supply of power. Hence, an additional control model has been developed to assist the open-loop optimization-based model, to handle the load demand uncertainty disturbance in real-time context. The control model proved to mitigate the issue of both unmet load demand and excessive supply of power through the application of a rule-based algorithm. Additionally, a higher energy savings was achieved through the successful reduction of the excessively supplied power
Sizing of stationary energy storage systems for electric vehicle charging plazas
Increasing numbers of electric vehicles (EV) and their fast charging stations might cause problems for electrical grids. These problems can be prevented by energy storage systems (ESS). Levelling the power demand of an EV charging plaza by an ESS decreases the required connection power of the plaza and smooths variations in the power it draws from the grid. In this article, a study of sizing of stationary ESSs for EV charging plazas is presented based on one year of data compiled from four direct current fast charging (DCFC) stations. Effects of the charging plaza size, grid connection power, and temporal resolution of input data on ESS requirements were studied. The ESS was controlled to reduce the connection power below certain limits which were altered from 5% to 100% with respect to the nominal power of the charging plaza. The charging plaza size ranged from 1 to 40 DCFC stations. The results show that the relative ESS power and energy requirements and the utilization rate of the ESS decrease, as the connection power and charging plaza size increase. The required connection power of an EV charging plaza can be decreased considerably by a relatively small ESS capacity. The effects of temporal resolution were studied, for the first time, by averaging the charging power time series of the charging plaza with averaging time intervals ranging from 1 s to 1 h. The temporal resolution of EV charging data had a notable effect on the results of ESS sizing: too sparse data distorts the results leading to an underestimation of ESS specifications and utilization.Peer reviewe
Spacecraft design project: Low Earth orbit communications satellite
This is the final product of the spacecraft design project completed to fulfill the academic requirements of the Spacecraft Design and Integration 2 course (AE-4871) taught at the U.S. Naval Postgraduate School. The Spacecraft Design and Integration 2 course is intended to provide students detailed design experience in selection and design of both satellite system and subsystem components, and their location and integration into a final spacecraft configuration. The design team pursued a design to support a Low Earth Orbiting (LEO) communications system (GLOBALSTAR) currently under development by the Loral Cellular Systems Corporation. Each of the 14 team members was assigned both primary and secondary duties in program management or system design. Hardware selection, spacecraft component design, analysis, and integration were accomplished within the constraints imposed by the 11 week academic schedule and the available design facilities
Techno-economic analysis of hybrid PV-CSP power plants.Advantages and disadvantages of intermediate and peak load operation
The present master thesis work deals with the techno-economic analysis of a combined PV-CSP utility scale power plant that operates to meet intermediate and peak load demand under the well-defined REIPPP price scheme in South Africa. For such analysis, a multi-objective optimization was carried out in order to find optimal plant designs for the selected market. Subsequently, the same optimization was performed for CSP alone and PV alone plants and its results used in a comparative analysis that allowed the economic feasibility of the PV-CSP combined plant to be assessed.
The study is based on a utility scale Solar Tower Power Plant (STPPP) with thermal energy storage and a PV plant models previously developed, validated and implemented in an in-house tool developed in KTH for techno-economic modelling of power plants. Such models were coupled together for combined operation and a specific dispatch strategy for intermediate and peak load operation was developed. The resulting combined model was further verified by using data gathered from real PV-CSP projects currently under development and the dispatch strategy was tested by using newly implemented indicators. Additionally, a methodology for calculating the average tariff that must be granted to ensure a desired level of profitability (fixed IRR) under a Power Purchase Agreement (PPA) contract was implemented. The resulting indicator was used in the techno-economic analysis of the plant, together with other performance indicators such as CAPEX and capacity factor.
The results of the multi-objective optimization show that, for the same dispatch strategy and tariff scheme, both the CSP alone and PV alone plants yielded lower average PPA prices and CAPEX than the PV-CSP hybrid. This was further confirmed by the fact that the PV capacity was minimized in all PV-CSP optimums, thus converging to a CSP only power plant. Furthermore, the CSP alone plant proved to be more flexible in varying its hourly and seasonal output levels on demand. PV alone optimum configurations all featured tracking systems to maximize power production during daytime and did not follow a peaking dispatch strategy due to the lack of a storage system. The PV-CSP hybrid solution scored higher values of capacity factor and performed better in meeting the dispatch strategy compared to the CSP alone and PV alone solutions, thus suggesting that the value of a combined plant can be increased when an operational strategy that maximizes capacity factors is sought (baseload), or when constraints are applied in terms of matching peak hours or meeting a fixed number operational hours per day.Outgoin
Photovoltaic potential in building façades
Tese de doutoramento, Sistemas Sustentáveis de Energia, Universidade de Lisboa, Faculdade de Ciências, 2018Consistent reductions in the costs of photovoltaic (PV) systems have prompted interest in applications with less-than-optimum inclinations and orientations. That is the case of building façades, with plenty of free area for the deployment of solar systems. Lower sun heights benefit vertical façades, whereas rooftops are favoured when the sun is near the zenith, therefore the PV potential in urban environments can increase twofold when the contribution from building façades is added to that of the rooftops. This complementarity between façades and rooftops is helpful for a better match between electricity demand and supply. This thesis focuses on: i) the modelling of façade PV potential; ii) the optimization of façade PV yields; and iii) underlining the overall role that building façades will play in future solar cities. Digital surface and solar radiation modelling methodologies were reviewed. Special focus is given to the 3D LiDAR-based model SOL and the CAD/plugin models DIVA and LadyBug. Model SOL was validated against measurements from the BIPV system in the façade of the Solar XXI building (Lisbon), and used to evaluate façade PV potential in different urban sites in Lisbon and Geneva. The plugins DIVA and LadyBug helped assessing the potential for PV glare from façade integrated photovoltaics in distinct urban blocks. Technologies for PV integration in façades were also reviewed. Alternative façade designs, including louvers, geometric forms and balconies, were explored and optimized for the maximization of annual solar irradiation using DIVA. Partial shading impacts on rooftops and façades were addressed through SOL simulations and the interconnections between PV modules were optimized using a custom Multi-Objective Genetic Algorithm. The contribution of PV façades to the solar potential of two dissimilar neighbourhoods in Lisbon was quantified using SOL, considering local electricity consumption. Cost-efficient rooftop/façade PV mixes are proposed based on combined payback times. Impacts of larger scale PV deployment on the spare capacity of power distribution transformers were studied through LadyBug and SolarAnalyst simulations. A new empirical solar factor was proposed to account for PV potential in future upgrade interventions. The combined effect of aggregating building demand, photovoltaic generation and storage on the self-consumption of PV and net load variance was analysed using irradiation results from DIVA, metered distribution transformer loads and custom optimization algorithms. SOL is shown to be an accurate LiDAR-based model (nMBE ranging from around 7% to 51%, nMAE from 20% to 58% and nRMSE from 29% to 81%), being the isotropic diffuse radiation algorithm its current main limitation. In addition, building surface material properties should be regarded when handling façades, for both irradiance simulation and PV glare evaluation. The latter appears to be negligible in comparison to glare from typical glaze/mirror skins used in high-rises. Irradiation levels in the more sunlit façades reach about 50-60% of the rooftop levels. Latitude biases the potential towards the vertical surfaces, which can be enhanced when the proportion of diffuse radiation is high. Façade PV potential can be increased in about 30% if horizontal folded louvers becomes a more common design and in another 6 to 24% if the interconnection of PV modules are optimized. In 2030, a mix of PV systems featuring around 40% façade and 60% rooftop occupation is shown to comprehend a combined financial payback time of 10 years, if conventional module efficiencies reach 20%. This will trigger large-scale PV deployment that might overwhelm current grid assets and lead to electricity grid instability. This challenge can be resolved if the placement of PV modules is optimized to increase self-sufficiency while keeping low net load variance. Aggregated storage within solar communities might help resolving the conflicting interests between prosumers and grid, although the former can achieve self-sufficiency levels above 50% with storage capacities as small as 0.25kWh/kWpv. Business models ought to adapt in order to create conditions for both parts to share the added value of peak power reduction due to optimized solar façades.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/52363/201
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