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Task 46


The objectives shall be achieved through the following four subtasks, with proposed subtask
leaders and activities indicated:

Subtask A: Solar Resource Applications for High Penetration of Solar Technologies
(SUNY/Albany, USA: Richard Perez)

This Subtask will develop the necessary data sets to allow system planners and utility operators to understand short-term resource variability characteristics, in particular up and down ramp rates, to better manage large penetrations of solar technologies in the grid system. Although this work is primarily focused toward PV systems, which react almost instantaneously to cloud passages over individual panels, the information is also useful for solar thermal and CSP systems where intermittence resources can impact their ability to meet load demands.

The following activities will be undertaken to assure that the objectives of this task are met:

Activity A-1: Solar variability, and specifically ramp rates, for particular systems (lead: Hans Georg Beyer). Specific high-frequency (10-min or less) solar data sets will be obtained through third party sources and will be analyzed to provide statistical characteristics of solar ramp rates for solar systems of various sizes.

Activity A-2: Spatial and temporal characterization of intermittency (lead: Richard Perez). In this activity, the combination of spatial and temporal variability of solar resources will be evaluated either from ground networks or from high spatial-resolution 15-minute satellite data (downscaled to 1-minute sampling rates). This will improve our understanding of cloud decorrelation characteristics and the effects of dispersed solar systems on aggregate system
output under various cloud climates.

Activity A-3: Integration of solar with other RE technologies (lead: Lourdes Ramirez Santigosa). Although hybrid systems are often considered for optimal renewable energy electricity production, hybrid systems can also be used for heating in combisystems such as
using biomass with solar heating. Technical requirements for grid integration depend on grid conditions, which will also be addressed in this activity. Ultimately this activity could include microgrids, but not at the start of the task. The focus of this activity is on weather data and irradiance data.

Activity A-4: Spatial and Temporal Balancing Studies of the Solar and Wind Energy Resource. This Activity includes the following elements: 1) The evaluation of the spatial balancing of the solar resource (both GHI and DNI)) across various distance scales; 2) The evaluation of the spatial and temporal balancing of both the solar and wind resources across various distance scales, and 3) Based on the eventual existence of a spatial balancing, the eventual improvement of the solar radiation forecasting associated with this balancing.

Subtask B: Standardization and Integration Procedures for Data Bankability
(lead: DLR, Germany, Carsten Hoyer-Klick)

Activity B-1: Measurement best practices. Manuals on best practices for obtaining measured data sets that provide “bankable” data for financial institutions will be prepared.

Activity B-2: Integration of data sources. This activity explores procedures of combining different data sets, such as short-term ground measurements with long-term satellite-derived data, for extrapolating quality ground data to longer-term climatic data sets, allowing for longterm cash flow analyses of projects.

Activity B-3: Evaluation of the use of TMY data. In this activity, the historical use of TMY data will be evaluated in the context of current best practices for simulating solar system design and output. Recommendations for alternative approaches to TMY data will be made, given that TMY data sets do not allow for evaluation of extreme high= and low-resource events.

Activity B-4: Data uncertainties over various time frames. This activity documents the importance of data uncertainty for data sets representing various time frames in ways that the risk in financing a project can be quantified.

Activity B-5: Gap-filling, QC, and Flagging. This activity documents best practices in filling missing data gaps, conducting data quality control, and flagging potentially erroneous data values when creating an archive of a database.

Subtask C: Solar Irradiance Forecasting
(Elke Lorenz, U. of Oldenburg, Germany)

Activity C-1: Short-term forecasting (up to 3-days ahead): co-leads: U of Oldenburg (Elke
Lorenz) and SUNY/Albany (Richard Perez). This activity tests and benchmarks forecasting
procedures covering three distinct time scales:

  • Forecasting from observations (0-6-hours):
  • NWP and mesoscale models (1-3-day ahead)
  • Integration of measurements with models for 0-24-hour ahead

Activity C-2: Integration of solar forecasts into operations (Lead: CENER, Lourdes Ramirez Santigosa). This activity examines the important issue of how solar forecasts are used in utility operations. A critical aspect of this task is to seek input from utility operators on the specific types of irradiance or power output forecasts they would like to have in order to improve system operations and reduce the overall cost of energy and maximize the use of renewable energy within the system. Another important point of this activity is related to the knowledge of the different electricity markets and to improve understanding of the influence of forecast in the final energy sale.

Activity C-3: Long-term variability and impact of climate change of solar resources (Lead: NASA, Paul Stackhouse). In this activity, studies of long-term solar data sets, both observed as well as satellite derived, will continue to asses episodes of “global dimming” and “global brightening”, important for evaluating potential long-term cash flow implications from solar systems. Efforts will be undertaken to link the results of IPCC climate change scenarios to predictions of future solar resource variations.

Subtask D: Advanced Resource Modeling
(NREL: Manajit Sengupta)

Activity D-1: Improvements to existing solar radiation retrieval methods (Lead: GEOModel, Tomás Cebecauer). A number of input parameters and modeling approaches to development of satellite-derived solar resource data sets will be examined, including:

  • Direct/diffuse irradiance (Aerosol Optical Depth, or AOD, is important here)
  • Spectrally-resolved irradiance
  • Angular distribution of irradiance
  • Atmospheric parameters (AOD)
  • Enhanced cloud parameters, including 3-D cloud characterization

Activity D-2: New modeling approaches (Lead: NREL, Manajit Sengupta) This task will evaluate the latest products coming out of the U.S. National Oceanic and Atmospheric Administration, such as the GOES Surface Irradiance Product, which offers a promising solution for providing near real-time irradiance values throughout the western hemisphere at 4-km resolution.

Activity D-3: Development of global solar resource data sets for integrated assessment of global and regional RE scenarios modeling, with a special focus on CSP and solar heating technologies (Lead: DLR, Carsten Hoyer-Klick). This task examines approaches for determining global renewable energy potentials, in particular global potentials, for use in renewable energy scenario modeling. The Activity also looks at the impact of up scaling fineresolution data into courser global grids, to see if the removal of subgrid variability introduces biases to the answers.


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International Energy Agency Solar Heating and Cooling Programme