Solar irradiance forecasting is critical to balancing solar energy production and energy consumpt... more Solar irradiance forecasting is critical to balancing solar energy production and energy consumption in the electric grid; however, solar irradiance forecasting is dependent on meteorological conditions and, in particular, cloud cover, which are captured in satellite imagery. In this paper we present a method for short-term solar irradiance forecasting using gridded global horizontal irradiance (GHI) data estimated from satellite images. We use this data to first create a simple linear regression model with a single predictor variable. We then discuss various methods to extend and improve the model. We found that adding predictor variables and partitioning the data to create multiple models both reduced prediction errors under certain circumstances. However, both these techniques were outperformed by applying a data transformation before training the linear regression model.
Hawaii is blessed with abundant natural wind and solar resources and like mainland utilities are ... more Hawaii is blessed with abundant natural wind and solar resources and like mainland utilities are contending with challenges of managing variability but on small, islanded grids. Meeting Hawaii’s future energy needs will take a variety of actions including: • Managing and maintaining existing infrastructure including existing renewable projects • Reliably adding more renewables • Greening existing utility power plants • Encourage energy conservation and efficiency Like fitting a square peg into a round hole there are fundamental challenge for integrating variable resources onto the electric grid. What are the integration challenges? How does it impact our island grids and existing infrastructure? What can be done to reliably accommodate renewables? Come learn more about innovative actions and strategies that Hawaiian Electric is investigating to manage utility resources and reliably accommodate renewable resources onto the grid.
Strategic Value Analysis - Economics of Wind Energy in California
This paper was prepared as the result of work by a member of the staff of the California Energy C... more This paper was prepared as the result of work by a member of the staff of the California Energy Commission. It does not necessarily represent the views of the Energy Commission, its employees, or the State of California. The Energy Commission, the State of California, its employees, contractors and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this paper; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This paper has not been approved or disapproved by the California Energy Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this paper.
Solar irradiance forecasting is critical to balancing solar energy production and energy consumpt... more Solar irradiance forecasting is critical to balancing solar energy production and energy consumption in the electric grid; however, solar irradiance forecasting is dependent on meteorological conditions and, in particular, cloud cover, which are captured in satellite imagery. In this paper we present a method for short-term solar irradiance forecasting using gridded global horizontal irradiance (GHI) data estimated from satellite images. We use this data to first create a simple linear regression model with a single predictor variable. We then discuss various methods to extend and improve the model. We found that adding predictor variables and partitioning the data to create multiple models both reduced prediction errors under certain circumstances. However, both these techniques were outperformed by applying a data transformation before training the linear regression model.
A realistic irradiance-based voltage flicker analysis of PV applied to Hawaii distribution feeders
2012 IEEE Power and Energy Society General Meeting, 2012
ABSTRACT Voltage Flicker caused by distributed generation is widely discussed during System Impac... more ABSTRACT Voltage Flicker caused by distributed generation is widely discussed during System Impact or Interconnection Studies. Misrepresentation of voltage flicker can often delay or create barriers to entry for renewable energy projects. The simplest voltage flicker analysis for photovoltaic (PV) generation is based on perceived instantaneous irradiance dips, of approximately 80 to 90%. These post-transient simulations often do not account for time variance and stability of other dynamic system components. Analysis is presented detailing an integrated inverter model and irradiance based analysis. Representative short time scale periods of 60 seconds are collected from multiple irradiance sensors to model different levels of cloud cover. Irradiance data feeds into a multiple inverter network with voltage changes calculated over the analysis time. Ongoing utility data collection at the distribution and sub-transmission levels can be used to validate performance and true flicker related impact of PV. The value and validity of using high fidelity, realistic time-based, irradiance data is presented versus assuming an instantaneous power drop.
Tools used for handling variable generation in the Hawaii Electric Light Co. control center
2012 IEEE Power and Energy Society General Meeting, 2012
ABSTRACT Hawaii Electric Light Co. operates an autonomous power system on the island of Hawaii wi... more ABSTRACT Hawaii Electric Light Co. operates an autonomous power system on the island of Hawaii with a diverse mix of generating resources. The installed wind capacity is about 20% of the typical day peak, and with a high capacity factor, it is not unusual for instantaneous penetration to exceed 20%. There is an installed capacity of 11.5 MW distributed solar photovoltaic (PV) generation, representing 6.7% and with the planned projects in the near term, distributed PV capacity will exceed 10% of a typical day peak. The variable generation from wind generation and, more recently, distributed solar photovoltaic generation has markedly affected system operation. This report will describe the operational challenges created by the variable generation resources, the existing operational techniques and tools, shortcomings and needs not addressed by the present methodologies and tools, and new tools under development in response to present needs.
Appendix I1-2 to Wind HUI Initiative 1: Field Campaign Report
This report is an appendix to the Hawaii WindHUI efforts to dev elop and operationalize short-ter... more This report is an appendix to the Hawaii WindHUI efforts to dev elop and operationalize short-term wind forecasting and wind ramp event forecasting capabilities. The report summarizes the WindNET field campaign deployment experiences and challenges. As part of the WindNET project on the Big Island of Hawaii, AWS Truepower (AWST) conducted a field campaign to assess the viability of deploying
Load Control for Turbine Blades: A Non-Traditional Microtab Approach
ASME 2002 Wind Energy Symposium, 2002
ABSTRACT Active flow control and load mitigation concepts developed for traditional aeronautical ... more ABSTRACT Active flow control and load mitigation concepts developed for traditional aeronautical applications have potential to decrease torque, bending and fatigue loads on wind turbine blades and to help increase turbine life. Much of the early work in flow control focused on steady aerodynamic benefits. More recent technologies have focused on unsteady flow control techniques which require a deeper understanding of the underlying flow physics as well as sensors to record the various time-dependent aerodynamic phenomena and fast actuators for control. This paper identifies some developmental control concepts for load mitigation along with a new translational microfabricated tab concept available for active flow and load control on lifting surfaces and explores their applicability for wind turbine rotor blades. Specifically, this paper focuses on experimental results based on an innovative microtab approach for unsteady, active load control. Previous papers on this effort by Yen et al. focused on the multi-disciplinary design methodology and the significant lift enhancement achieved using these micro-scale devices. The current research extends the effort to include dynamic results with discontinuous tab effects, effects on drag, and lower (pressure side) and upper surface (suction side) tab deployment effects for the prototype airfoil as well as for the S809, a representative wind turbine airfoil. Results show that the microtab concept can provide macro-scale load changes and is capable of offering active control of lift and drag forces for load alleviation.
Active Load Control Using a Nontraditional MEMs Approach
An active load control concept using micro-electro-mechanical (MEM) translational tabs has been u... more An active load control concept using micro-electro-mechanical (MEM) translational tabs has been undergoing testing and development at the University of California at Davis. The concept utilizes microfabricated sliding components to retract and extend small tabs located near the trailing edge of a lifting surface. The tab assembly, referred to as a microtab, extends approximately normal to the surface and has a maximum deployment height on the order of the boundary-layer thickness. Deployment of these retractable devices on either the suction or pressure side of a lifting surface effectively modifies the camber distribution and changes the lift and moments generated. On the pressure side, the effect of the microtabs on lift is shown to be as powerful as conventional flap-like control surfaces resulting in positive DCl changes of 30conventional control surfaces which typically occupy 20of the lifting surface, these large-scale load changes are achieved using microtabs with heights of ...
The 2011 International Joint Conference on Neural Networks, 2011
This paper presents a new probabilistic approach of the real-time state estimation on the micro-g... more This paper presents a new probabilistic approach of the real-time state estimation on the micro-grid. The grid is modeled as a factor graph which can characterize the linear correlations among the state variables. The factor functions are defined for both the circuit elements and the renewable energy generation. With the stochastic model, the linear state estimator conducts the Belief Propagation algorithm on the factor graph utilizing real-time measurements from the smart metering devices. The result of the statistical inference presents the optimal estimates of the system state. The new algorithm can work with sparse measurements by delivering the optimal statistical estimates rather than the solutions. In addition, the proposed graphical model can integrate new models for solar/wind correlation that will help with the integration study of renewable energy. Our state-of-art approach provides a robust foundation for the smart grid design and renewable integration applications.
(ANL) reviewed FY02 plans and presented status reports. DOE representatives Sid Diamond and Jules... more (ANL) reviewed FY02 plans and presented status reports. DOE representatives Sid Diamond and Jules Routbort were in attendance and provided an update on the budget situation. Industrial representative Skip Yeakel from Volvo attended and gave a presentation that provided the industrial perspective.
“Back-to-basics”: Operationalizing data mining and visualization techniques for utilities
The 2011 International Joint Conference on Neural Networks, 2011
ABSTRACT Today, the family of Hawaiian Electric utilities, consisting of Hawaii Electric Light Co... more ABSTRACT Today, the family of Hawaiian Electric utilities, consisting of Hawaii Electric Light Company (HELCO) on the Big Island of Hawaii, Maui Electric Company (MECO) on the islands of Maui, Molokai and Lanai and Hawaiian Electric Company (HECO) on the island of Oahu, are contending with PV penetrations in excess of 20 percent during high electricity demand days (e.g. weekdays) and over 60 percent penetration during light load demand days (e.g. weekends) on certain distribution circuits. With the emergence of more, low-cost photovoltaic (PV) systems and consumer self-generation programs, such as net energy metering and feed-in-tariffs, today's utilities are facing a fundamental shift towards a need to get more visibility to customer-sited, distributed generating resources (DG). The Hawaiian utilities are among an emerging set of utilities around the world leading the nation in contending with high levels of renewable penetration on their distribution systems. Hawaiian Electric Utilities are pursuing efforts to gather, evaluate and target (GET) relevant resource datasets in conjunction with time synchronized system data to enable planning, forecasting and operations with high penetration of variable, distributed renewable resources.
A computational design and analysis of a microtab based aerodynamic loads control system is prese... more A computational design and analysis of a microtab based aerodynamic loads control system is presented. The microtab consists of a small tab that emerges from a wing approximately perpendicular to its surface in the vicinity of its trailing edge. Tab deployment on the upper side of the wing causes a decrease in the lift generation whereas deployment on the pressure side causes an increase. The computational methods applied in the development of this concept solve the governing Reynolds-averaged Navier-Stokes equations on structured, overset grids. The application of these methods to simulate the flows over lifting surface including the tabs has been paramount in the development of these devices. The numerical results demonstrate the effectiveness of the microtab and that it is possible to carry out a sensitivity analysis on the positioning and sizing of the tabs before they are implemented in successfully controlling the aerodynamic loads.
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Papers by Dora Nakafuji