Glossary
Glossary
AC Capacity
AC Capacity represents “Alternating Current” electric charge flow, which may alternate between flow directions. The grid and common appliances run on alternating current. DC current from solar panels must be converted to AC energy to be used.
Also Energy
Also Energy provides solar irradiance data with a horizontal spatial resolution of 1 km.
ASGEN
AsGen or “As Generated” (also sometimes referred to as Generation-Weighted and Production-Weighted) is the price of power realized by a variable generation project, such as wind and solar. It is calculated as the generation-weighted average price of power during a given time period. For example, if the period of time has 3 intervals, and the price of power was $5, $25 and $45 respectively, and generation during those same intervals was 10MW, 15MW and 5MW respectively, the AsGen price of power would be [($5*10) + ($25*15) + ($45*5)] / 3 = $216.67.
ATC Price
ATC or “Around the Clock” price means the average price of power for a given period of time. For example, if the period of time has 3 intervals, and the price of power during each interval was $5, $25 and $45 respectively, then the ATC price would be (5+25+45)/3 = $25.
Average
Average represents a mean value of some sample. That sample may consist of price, generation or revenue.
Average Strike Price
The fixed price of the contract, denominated in either $ or $/MWh.
Basis
Basis describes a project’s price difference between its node and hub, relying on which transmission lines and generators are active in the grid.
Busbar Data
Busbar data refers to generation data that directly enters the grid from the system operator.
Calculation Interval
The time granularity of price and generation data provided by the contracted energy plant.
Capacity Factor
The percentage of generation compared to total generation capacity.
COD
COD stands for “Commercial Operation Date”. This date refers to when a project becomes operational and can begin selling power.
Combined Generation
A combination of modeled and invoiced generation. Modeled generation is used when invoiced generation is not available.
Contracted Fraction
The portion of a project’s generation that is being transferred by the contract.
Curtailment
Curtailment is generation that is reduced (or dropped to zero) based on grid constraints.
DA Market
DA stands for the “Day-Ahead” market. The DA market refers to the price of power data on the day before the delivery date.
DC Capacity
DC stands for “Direct Current” electric charge flow, which flows in only one direction. Inverters are used in DC solar panels to convert from DC to AC.
ERCOT
The Electric Reliability Council of Texas: Provides hourly-level operating project generation data. Operating project generation data for the rest of the 6 American ISOs is only available at the monthly-level.
EIA
The Energy Information Administration: Provides monthly-level operating project generation data.
FVS
Fixed Volume Swap: a contractual swap of a fixed volume of power (MWh) at a fixed price ($/MWh) between two parties to hedge price risk. FVSs can have several structures, each depending on when the energy is swapped.
HRRR
NOAA High Resolution Rapid Refresh: Real-time (daily release), 3km resolution, hourly-updated atmospheric model. Data available from 2013 to present. Meteorological data including wind speeds, temperature, and air density.
Invoiced Generation
Generation values that come directly from a submitted invoice.
ISO Definition
ISOs as shown in Discover are used for defining ISOs in the API. In Discover the regions covered by NWPP, WECC, and SERC are labelled as ISOs to conveniently compare regions.
ISO Peak and Off-Peak Definitions
ISOs define on-peak and off-peak periods differently, this table summarizes on-peak and off-peak definitions by ISO:
| ISO | Time Zone | On-Peak Periods | Off-Peak Periods |
|---|---|---|---|
| ISONE | EPT | 8:00 to 23:00, Monday-Friday | 24:00 to 7:00, Monday-Friday; All-day Saturday and Sunday |
| NYISO | EPT | 8:00 to 23:00, Monday-Friday | 24:00 to 7:00, Monday-Friday; All-day Saturday and Sunday |
| PJM | EPT | 8:00 to 23:00, Monday-Friday | 24:00 to 7:00, Monday-Friday; All-day Saturday and Sunday |
| MISO | EST | 7:00 to 22:00, Monday-Friday | 23:00 to 6:00, Monday-Friday; All-day Saturday and Sunday |
| ERCOT | CPT | 7:00 to 22:00, Every Day | 23:00 to 6:00, Every day |
| SPP | CPT | 7:00 to 22:00, Monday-Friday | 23:00 to 6:00, Monday-Friday; All-day Saturday and Sunday |
| CAISO | PPT | 7:00 to 22:00, Monday-Saturday | 23:00 to 6:00, Monday-Saturday; All-day Sunday |
Some ISO’s consider NERC holidays to be entirely off-peak. NERC holidays are New Year’s Day, Memorial Day, Independence Day, Labor Day, Thanksgiving Day, and Christmas Day. These are off-peak periods for most ISOs; ERCOT treats holidays as weekend days with a weekend on-peak and off-peak period.
MERRA2
NASA Modern Era Retrospective Analysis for Research and Applications: Data spans from 1979 – Feb 2016 with a spatial resolution of ~50 km and a 1-2 month release lag.. Discover uses it for historical meteorological data, including wind speeds and temperature.
Modeled Generation
Backcast generation that results from REsurety’s proprietary calculations and research methods.
Node
A node refers to a project’s interconnection point, which is the specific price location where the project contributes power to the grid. Node assignments are made using publicly available data provided by each ISO.
p-values
P-values denote a percent likelihood of a random variable exceeding a fixed value. That random variable may be price, generation or revenue.
Examples:
- A P1 price of $40 means there is a 1% likelihood of price exceeding $40.
- A P99 price of $5 means there is a 99% likelihood of price exceeding $5.
- A P1 generation of 100 MWh means there is a 1% likelihood of generation exceeding 100 MWh.
- A P99 generation of 2 MWh means there is a 99% likelihood of generation exceeding 2 MWh.
REzones
REzones stand for “Renewable Energy Zones”. REzones are created by REsurety, and are regions that represent consistent resource value for wind and solar, determined by the generation and power prices in the area. REzones allow users to determine the value of a project within a certain zone.
RT Market
RT stands for “Real-Time” market. The RT market refers to the price of power data received in real-time, typically in ~5-minute intervals. Discover updates this data periodically.
Settlement Hub
A settlement hub is a virtual location made up of many nodes where an ISO sells its electricity. Choosing a hub in Discover specifies which hub should be used for a certain project, and the user can select a hub that is more relevant to their circumstances. Discover assigns a default hub to each project based on internal hub shape files, or the project’s ISO location (the ISO location is given preference if it differs from the shape files). Users have the option to change the default hub Discover has assigned to any project to another hub within that ISO.
Shape
Also known as capture rate (can be the $ difference from subtraction or % difference from division – but always is the relationship between AsGen and ATC)
Third Party Data Sources
- EIA
- Energy Information Administration, US government agency
- ERCOT
- Electric Reliability Council of Texas, US Corporation
- HRRR
- High Resolution Rapid Refresh
- Provided by NOAA (National Oceanic & Atmospheric Administration), US government agency
- Spatial resolution 3km
- MERRA-2
- Modern Era Retrospective Analysis for Research and Applications
- Provided by NASA (National Aeronautics and Space Administration), US government agency
- Spatial resolution 50km
- ERA5
- ECMWF RE-Analysis (European Centre for Medium-Range Weather Forecasts), Intergovernmental
- Spatial resolution ~30km
- Also Energy
- Yes Energy
- OCTGH
- Over-the-counter commodities, Global Holdings
Third Party Data Source Uses
| Data Source | Data Type | Data | Wind Projects | Solar Projects |
|---|---|---|---|---|
| EIA | project | project characteristics | x | |
| EIA | energy | plant generation | x | |
| ERCOT | energy | plant generation | x | x |
| HRRR | weather | wind speed | x | x |
| HRRR | weather | temperature | x | x |
| MERRA-2 | weather | wind speed | x | x |
| MERRA-2 | weather | temperature | x | x |
| ERA5 | weather | irradiance | x | |
| Also Energy | weather | irradiance | x | |
| Yes Energy | price | $/MWh | x | x |
| OTCGH | price | $/MWh | x | x |
TMY
TMY stands for a “Typical Meteorological Year”, and is also referred to as an “8760”, which stands for the 8,760 hours in a typical calendar year. An 8760 energy model is the expected generation for a wind or solar project at each hour of a “normal weather” year, and is used by many in the renewable energy industry. REsurety notes the dangers of using an 8760 for projecting financial performance because 8760s can lead to significant revenue modeling errors. Discover’s Compare metric allows users to examine the use of the weather-year instead of an 8760 in the As-Gen vs. 12×24 pricing structures. More details about Discover’s consideration of the 8760, and how to compare it to the weather-year in Discover can be found here: How does Discover reflect the differences between weather-year price structuring and an 8760? Additionally, see REsurety’s white paper Friends Don’t Let Friends Use 8760s for more information.
Weather-year
A weather-year describes the estimated hourly energy production of a project over the course of a year with attention to observed or projected weather specific to that year. In contrast, a typical meteorological year (TMY, or 8760) is the estimated hourly energy production calculated using average weather for a certain location. This weather distinction accounts for atypical weather years and events that have immense impacts on the price of power. Discover includes the weather-year along with concurrent prices in the As-Gen pricing structure, which accounts for the impact of renewable generation on market prices and avoids over estimation. This distinction allows Discover to produce an accurate representation of proxy generation with precision, while avoiding financial modeling errors that can result from the standard 8760 practice. More details about Discover’s consideration of the 8760 can be found here: Where are the Weather-Year vs. 8760 pricing structure differences in Discover? Additionally, see REsurety’s white paper Friends Don’t Let Friends Use 8760s for more information.
Wind Turbine Layout and Specification Data
Includes turbine location, layout, hub height, rotor diameter, air density, and more. Collected & visualized using R and Google Earth.