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Glossary of Technical Renewable Energy Terminology

API

An Application Programming Interface is a way in which one computer program may communicate with another. In practice, an API enables different software programs to use the internet or a local network to request and exchange information.

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Arc ASCII Grid format

A specific interchange format developed for ARC/INFO rasters in ASCII format. The format consists of a header that specifies the geographic domain and resolution, followed by the actual grid cell values. Usually the file extension is .asc, but recent versions of ESRI software also recognize the extension .grd. [1]

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Assessment

In the renewable energy project development life cycle, this is the second phase. The goal of this phase is to determine if a site is viable for development and includes more in-depth analysis of power capacity estimates and long-term performance. For example, 3TIER can perform a Wind Site Climate Variability Analysis to determine the long-term wind behavior and power generation potential at a promising site.

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CMC

The Canadian Meteorological Centre (CMC) is an NWP model that is operated by Environment Canada. The global CMC model is also called the Global Environmental Multiscale (GEM) model. It is initialized twice a day at 0000 and 1200 UTC.

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CAD

Computer-Aided Design is the use of computer technology for the design of objects, real or virtual. [2]

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CSV file

A Comma-Separated Values file is used for the digital storage of data and is structured in the form of a table of lists, where each line in the file corresponds to a row in a table. Within a line, fields are separated by commas, each field belonging to one column of a table. Since it is a common and simple file format, CSV files are often used for moving tabular data between two different computer programs, for example between a database program and a spreadsheet program. [3]

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Deterministic

A prediction that has a single outcome because the model simulation that generated it does not show certainty or probability ranges in the final value. In the case of a flood forecast, it would be a sequence of hourly flow values based on a single best estimate of both the initial basin state and future weather, while ignoring the certainty and probability ranges of both.

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DIF

Diffuse Horizontal Irradiance is the amount of radiation received per unit area by a surface (not subject to any shade or shadow) that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmosphere and comes equally from all directions.

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Diurnal

Daily or pertaining to daytime, often demonstrating a periodic alteration of conditions between day and night.

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DNI

Direct Normal Irradiance is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the sun.

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ECMWF

The European Centre for Medium Range Weather Forecasts (ECMWF) is a modeling center that generates a global NWP model forecast. The forecasts are initialized twice a day at 0000 and 1200 UTC.

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EMA

An Energy Management Agreement is a legal contract typically between a large energy provider or asset owner and a third party group. Under the contract, the third party (known as the EMA provider) is commissioned to optimize energy assets for the energy provider for improved financial and/or physical performance. This can include placing and rolling hedges, selling into various physical and financial markets, managing transmission capacity, and reducing imbalance charges. An EMA takes advantage of the EMA providers' risk management and trading capabilities as well as credit.

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ENSO

El Niño / Southern Oscillation are two proven patterns with a demonstrated impact on global weather conditions. El Niño/La Niña is an interannual pattern with a clear oscillation between warm and cold surface water temperatures in the tropical, eastern Pacific Ocean near Peru. The Southern Oscillation is exhibited by a difference in air pressure between Tahiti and Darwin, Australia and is essentially a different metric than El Niño/La Niña for the same periodic, ocean-atmosphere climate system phenomenon.

ENSO has 3 states (El Niño, La Niña, and Neutral) with a recurring timeframe of 4 to 6 years and is the leading source of climate predictability in the world. ENSO does not drive climate sensitivity everywhere, but has a strong influence in many hydro-rich regions of the world, including the North American Pacific Northwest.

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Forecasting

In the renewable energy project development life cycle, this is a service that can be used during the final phases of development, including construction and project management. To get the most out of your investment, forecasting service provides the essential information to maximize the value of your project while mitigating the risks. It enables optimal energy management and can even inform decision-making during the construction of your project.

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GeoTIFF

A TIFF (Tagged Image File Format), which allows geographic (or cartographic) data to be embedded within it. The geographic data includes projections, coordinate systems, ellipsoids, datums, and everything else necessary to establish the exact spatial reference for the file. This data can be used to position the image in the correct location and geometry on the screen of a geographic information display. Any GIS, CAD, Image Processing, Desktop Mapping, or other type of system using geographic images can read GeoTIFF files created on any system to the GeoTIFF specification. Values of -9999 are 'no data' values. [4] [5]

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GFS

The Global Forecast System (GFS) is a global NWP model operated by the National Centers for Environmental Prediction (NCEP). The model is initialized at 0000, 0600, 1200, and 1800 UTC.

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GHI

Global Horizontal Irradiance is the total amount of shortwave radiation received from above by a horizontal surface. This value is of particular interest to photovoltaic installations and includes both Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DIF).

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GIS

Geographic Information Systems capture, store, analyze, manage, and present data that is linked to location. Technically, GIS is mapping software and all of its applications including: remote sensing, land surveying, aerial photography, mathematics, photogrammetry, geography, and any other tools that can be implemented with GIS software. [6]

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Horizon Time

The horizon time is the difference between the forecast creation time and the end of the forecast period of interest.

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Hub Height

The distance from the turbine platform to the rotor of an installed wind turbine, which indicates how high your turbine stands above the ground, not including the length of the turbine blades. Commercial scale turbines (greater than 1MW) are typically installed at 80 meters (262 ft) or higher, while small-scale wind turbines (approximately 10kW) are installed on shorter towers. Wind speed generally increases with the height above the ground, so to get an accurate assessment you want to choose a hub height that is close to your expected turbine height.

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KML file

A Keyhole Markup Language file is written in an XML-based language for expressing geographic annotation and visualization on web-based, two-dimensional maps and three-dimensional Earth browsers. Originally developed for use with Google Earth, KML is an international standard of the Open Geospatial Consortium. [7]

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KMZ file

A zipped KML (or Keyhole Markup Language) file is known as a KMZ with a .kmz extension. KML files are zipped for easier distribution and the contents of the KMZ are a single root KML document (notionally 'doc.kml') and optionally any overlays, images, icons, and models referenced in the KML including network-linked KML files. [7]

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MAE

Mean Absolute Error is a value regularly used to measure the accuracy of predictions against actual conditions. This statistic is determined by calculating the difference between all of the predicted values and all of the actual observed values and then finding the average of all the resulting values.

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MCP

Measure Correlate Predict is a method that models the association between wind data recorded at an observational site and data at a nearby reference site for a concurrent period of time. MCP algorithms estimate the long-term wind speed and direction distributions at an observational site using long-term data from a reference site. Thus MCP analysis results in estimations of long-term mean wind speed and wind speed distributions at an observational site.

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Mesoscale

The scale of meteorological phenomena that range in size from several kilometers to around 100 kilometers. This includes MCCs (Mesoscale Convective Complexes) such as thunderstorms that peak at night with heavy rain and flood risk, and MSCs (Mesoscale Convective Systems), such as large complexes of thunderstorms, tropical cyclones, and squall lines. Smaller phenomena are classified as microscale, while larger phenomena are classified as synoptic-scale. [8]

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Microscale Diagnostic Model

Due to the high computing cost to our clients of running NWP (Numerical Weather Prediction) models at a 90-meter resolution, 3TIER uses a microscale diagnostic model (MDM). MDM is a very fine-scale, non-linear model, which helps simplify the process of downscaling mesoscale NWP model data to a fine-scale grid, most useful for creating turbine layouts. The process is more advanced than interpolation because it takes land features into account.

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MOS

Model Output Statistics is a technique that allows on-site observational data to be incorporated into resource analysis to validate and correct modeled data. MOS uses a multi-linear regression equation to remove bias and adjust the variance of the raw model output to better match the observational data at available observation locations. The MOS equation for each observation station is trained over the observational period of record. The MOS equation is then applied for all time steps of the modeled dataset, so that corrections can be made for periods during which direct observational data are unavailable. The value of performing MOS correction is it captures the unique characteristics of a site through on-site observations and places them into the long-term historical perspective provided by modeled data.

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NAM

The North America Mesoscale (NAM) model is operated by the National Centers for Environmental Prediction (NCEP). It is a limited area model that covers the Continental US at 13 km horizontal resolution. It.s parent global model is the GFS, and is thus initialized at 0000, 0600, 1200, and 1800 UTC. The forecasts extend to 84 hours.

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NCAR/NCEP reanalysis

A dataset from the National Center for Atmospheric Research (NCAR) and the National Centers for Environmental Prediction (NCEP), which is comprised of data taken as often as 8 times daily from as early as 1948 leading up to the present. This project uses a state-of-the-art analysis and forecast system to perform data assimilation.

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NCEP-ADP network

A network of global surface observations developed by the National Centers for Environmental Prediction (NCEP). ADP is an abbreviation for Automated Data Processing. The network is made up of data taken from 1975 to the near present, including moving ship, fixed ship, and buoy (moored and drifting). The reports usually include observations of cloud and wave behavior, surface and sea level pressure, air and surface temperature, dew point temperature, precipitation, and wind direction and speed.

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Niño 3.4

The tropical Pacific Ocean has been broken into 5 different regions (Niño 1, 2, 3, 4, and 3.4) to facilitate the sampling of sea surface temperature data. Niño 3.4 is the most central of these regions located in the middle of the Pacific Ocean around the equator (120° W - 170° W and 5° N - 5° S).

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Niño 3.4 anomalies

Deviation from average sea surface temperatures within the Niño 3.4 region.

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NWP

Numerical Weather Prediction is a methodology, which inputs current weather conditions to mathematical models of the entire atmosphere to make predictions about weather. In order to make the results useful, NWP models must produce data at a fine resolution, requiring the use of some of the most powerful supercomputers in the world due of the complexity of the calculations and the size of the datasets involved. [9]

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Operations

In the renewable energy project development life cycle, this is the final phase, including construction and project management. To get the most out of your investment, forecasting service provides the essential information to maximize the value of your project while mitigating the risks. It enables optimal energy management and can even inform decision-making during the construction of your project.

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P10

The upper exceedence probability value where there is a 10% probability that the observed value will exceed this value.

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P90

The lower exceedence probability value where there is a 90% probability that the observed value will exceed this value.

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PDO

The Pacific Decadal Oscillation is a pattern of Pacific climate variability that is distinct from El Niño/Southern Oscillation (ENSO). The PDO is detected by warm or cool surface water temperatures in the Pacific Ocean north of 20° N. This shift phases on at least an inter-decadal time scale, usually about 20 to 30 years. During warm, or positive phases, the west Pacific becomes cool and part of the eastern ocean warms. During 'cool', or 'negative' phases, the opposite pattern occurs. The main characteristics that distinguish PDO from ENSO are that the climatic impact of PDO is most visible in the North Pacific and less so in the tropics (the opposite is true for ENSO), in addition, all 20th century PDO events have persisted for 20 to 30 years, while typical ENSO events persist for only 6 to 18 months. [10]

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Physically-based, fully distributed

This term indicates that 3TIER's hydrologic model contains physics based relationships and uses realistic parameters to control these relationships. In addition, our model uses these physical relationships to create estimations for thousands of different grid cells distributed over the entire land area. Due to our advanced computing capabilities, we can run the model for each discrete unit within a watershed area to determine how the water balance in any one unit affects the units around it based on real physical properties.

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Power Capacity Factor

Power capacity factor is the value that results from dividing power by available capacity and is typically shown as a percentage. Available capacity can vary depending on whether the project has all turbines online or is being curtailed for any reason.

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Power Density

A way of assessing the amount of energy available at a site for conversion by a wind turbine. Its calculation is determined by taking both wind speed and air density into account and it is measured in Watts per meter squared. Mapping analysis {% trans "showing the distribution of wind power density is often a first step in identifying possible locations for wind turbines. In the United States, the National Renewable Energy Laboratory classifies wind power density into ascending classes. The larger the wind power density at a location, the higher it is rated by class. Wind power classes 3 (300 – 400 W/m 2 at 50 m altitude) to 7 (800 – 2000 W/m 2 at 50 m altitude) are generally considered suitable for wind power development." %} [12]

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PPA

A Power Purchase Agreement is a legal contract between an electricity generator (or PPA provider) and a host site owner. In these agreements, PPA providers are able to secure funding for an energy project, which they maintain and monitor, by selling the generated electricity to the host site owner at a contractual price for the life of the contract, typically 5 to 25 years. [11]

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Probabilistic

A prediction that provides a range of forecast values on a graph. Probabilistic predictions allow risk-based decision-making.

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Project Development Life Cycle

The process of building a renewable energy project is composed of 3 main phases: prospecting, assessment, and operations, including forecasting. At 3TIER we strive to deliver solutions for each of these stages that offer the highest levels of accessibility, usability, availability, and accuracy.

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Prospecting

In the renewable energy project development life cycle, this is the initial phase, which is composed of early stage exploration of available resources for solar, wind, or hydro development. Examples of prospecting include browsing different areas on the FirstLook interface or purchasing a GIS Data Layer for further analysis.

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Pyranometer

An instrument used to measure solar irradiance on a level surface from a field of view of 180 degrees.

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Pyrheliometer

An instrument used to measure Direct Normal Irradiance (DNI), which is designed with a solar tracking system to keep the instrument aimed directly at the sun.

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R - squared

A statistical measure of how well a regression line approximates real data points and indicates how well one term predicts another term. [13]

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REST

A Representational State Transfer interface is a straightforward web convention for running software as a service over the internet. Similar to the architecture of the World Wide Web, REST allows users to type a request into their internet browser and receive an answer to their request via as a new web page. 3TIER, for example, uses REST as the interface for the API product.

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RMSE

Root Mean Squared Error is the square root of the mean square error, which makes it a more easily interpreted statistic since it shares the same units as the quantity being graphed. The mean squared error is the resulting value from measuring the distance between every data point and a simulated curve, squaring each distance, and taking the average of all the squared distance values. [14]

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SNOTEL

Snowpack telemetry (SNOTEL) is an automated system of snowpack and related climate sensors operated by the Natural Resources Conservation Service (NRCS) of the U.S. Department of Agriculture. There are over 600 SNOTEL sites in 13 states, including Alaska, which are generally located in remote high-mountain watersheds where access is often difficult or restricted. All SNOTEL sites measure snow water content, accumulated precipitation, and air temperature. Some sites also measure snow depth, wind speed, solar radiation, humidity, and atmospheric pressure. These data are used for general climate research, forecasting yearly water supplies, and predicting floods. [15]

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TAB

TAB files can be either an input or an output of WAsP, an industry standard simplified modeling software. Unlike WRG files, which provide information for each model grid point, TAB files provide data, such as wind speed and weibull distribution, for a single point. These types of files are often composed of met tower observations that have been converted to the .tab extension for use in WAsP. In WAsP these files are used to create wind maps and WRG files, which can then be imported into many other programs, such as WindPRO and WindFarmer.

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TVM

The Time-Varying Microscale (TVM) model is a microscale diagnostic model specifically designed to compute data for extremely high-resolution mapping (tens of meters to a few hundred meters) without the high computational costs of running a mesoscale NWP model such as WRF.

TVM uses high-resolution land surface data to calculate the effects of microscale terrain features, near-surface roughness features, and other terrain blocking effects typically left unresolved by coarser mesoscale NWP models. Microscale terrain features are resolved using a kinematic terrain adjustment, near-surface roughness features are resolved using a log-profile surface roughness adjustment, and a Froude number adjustment is applied to calculate terrain-blocking effects on wind flow.

All of these effects are computed at each time step in the study period and based not only on wind speed and elevation, but also on quantities such as wind direction and thermodynamic properties of the lower atmosphere, enabling a sophisticated time-varying spatial analysis.

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UTC

Coordinated Universal Time is also known as Greenwich Mean Time (GMT) or simply Z. This is the time corresponding to the prime meridian of 0 degrees longitude. This is a 24-hour clock that does not experience any daylight savings time shift.

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Watershed

The region or area drained by a river, stream, or other water resource.

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Weibull

Due to its versatility, this distribution is one of the most widely used lifetime distributions in reliability engineering and life data analysis. Weibull can mimic the behavior of other statistical distributions, such as the normal and the exponential, based on the value of the shape parameter, β. Some 3TIER reports, for example, use Weibull to show the distribution of hourly wind speeds throughout the year, giving you an idea of the wind speed range at your site and how frequently high or low wind speeds occur.

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WRF

The Weather Research and Forecasting (WRF) Model is a next-generation mesoscale NWP (Numerical Weather Prediction) system designed to serve both operational forecasting and atmospheric research needs, which is suitable for a broad spectrum of applications across scales ranging from meters to thousands of kilometers.

WRF allows researchers to conduct simulations reflecting either real data or idealized configurations and provides operational forecasters a model that is flexible and efficient computationally, while still incorporating advances in physics, numerics, and data assimilation contributed by the research community. It features multiple dynamical cores, a 3-dimensional variational (3DVAR) data assimilation system, and a software architecture allowing for computational parallelism and system extensibility. WRF has a rapidly growing population of users and is the most recent and widely accepted NWP model among the atmospheric science and research community.

WRF was developed collaboratively by numerous organizations, principally the National Center for Atmospheric Research (NCAR), the National Oceanic and Atmospheric Administration (NOAA), the National Centers for Environmental Prediction (NCEP) and the Forecast Systems Laboratory (FSL), the Air Force Weather Agency (AFWA), the Naval Research Laboratory, the University of Oklahoma, and the Federal Aviation Administration (FAA). [16]

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WRG

WAsP Resource Grid files are an output of WAsP, an industry standard simplified modeling software. These files provide information, such as wind speed and weibull distribution, for each model grid point. WRG files can be imported into many other programs, such as WindPRO and Wind Farmer.

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XLS file

An XLS (or Excel Spreadsheet) file is primarily associated with the Microsoft Excel program. It is a common spreadsheet format and the file consists of information in cells on a spreadsheet and potentially on multiple sheets. XLS files are frequently used by businesses to organize information.

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XML file

An Extensible Mark-up Language file is used for the digital storage of data with the elements of the file defined and the values given. Since it is a common and simple file format, XML files are often used for moving data between two different computer programs. For example, 3TIER forecasting clients often move data from 3TIER's forecasts to their database programs.

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These terms and definitions were compiled by 3TIER from a variety of sources. Many were defined by our own in-house experts and scientists; others are common among the broader atmosphere science and web community.

References