Greenbyte Documentation

Glossary

Signal Glossary

aggregation ()

The signal calculation documentation describes how signals are calculated for a single time step. To view the data for time intervals, the data needs to be aggregated. There are two aggregation methods:

Normal

For “normal” signals, aggregation is an average or a sum of the value for each time step within the requested interval. For example, the average Availability for a month is the average availability of all time steps during the month. When the device and source resolutions don’t match up exactly a resolution conversion must be done.

Resolution-dependent

Signals that are "resolution-dependent" are calculated for the specified resolution. If data is requested for a month, the calculation is done for that month.

For example, the formula for Performance Index is:

aggregating_data_example.png

But the Performance Index is not calculated per time step. It is calculated for the full month with n time steps. Therefore, the formula is:

aggregating_data_example_2.png
degradation factor ()

Photo-voltaic solar panels degrade in performance over time. This can be approximated by an annual degradation factor. The following formula is used in potential power calculations to calculate the effective degradation factor for a given timestamp, given the commissioning date and degradation factor.

DY is the metadata value (yearly) Degradation Factor set per site.

tM(t,u) gives the absolute month difference between two timestamps.

t0 is the Commisioning Date metadata value set per inverter.

degradation_factor.png
device resolution (Resolution)

Controls the resolution of the time series data for the device. Real-time data from the device will be aggregated to time steps according to the device resolution.

When the requested target resolution for data is different from the device resolution, a resolution conversion will be done.

helper signal ()

Helper signals are used as input to other signals, but are not available in the signal selector in Greenbyte and can therefore not be visualized on their own.

irradiance cut-in ()

Irradiance data is often unreliable because of cheap sensors, night-time moonlight, etc. It is not uncommon to get false irradiance values around 0.

Therefore, it is advised to set a threshold to use in the calculations with irradiance cut-in, disregarding all irradiance values below the threshold.

I is the irradiance for each timestep.

I0 is set as the Availability Irradiance Cut-In metadata value per inverter (W/m2)

irradiance_cut_in.png
resolution conversion ()

When you look at data in a different resolution than the device resolution, the data is converted to the requested resolution. This resolution conversion is always done before any aggregation of data between different devices is performed.

When averaging signals, the aggregation for a target interval is done as a weighted average:

resolution_conversion_1.png

V is the set of values overlapping with the target interval I

Wv is the weight of the value V, which is the fraction of the value's interval overlapping with the target interval.

When summing signals, the aggregation is done as a weighted sum:

resolution_conversion_2.png

Example data conversion from 15-minute resolution to 10-minute resolution

A turbine has the following 15-minute wind speed data:

resolution_conversion_3.png

The conversion to 10-minute data is done using the weighted average.

resolution_conversion_4.png

Example data convertion from 10-minute resolution to 15-minute resolution

A turbine has the following 10-minute energy export data:

resolution_conversion_5.png

The conversion to 15-minute data is done using the weighted sum.

resolution_conversion_6.png

Example data convertion from 10-minute resolution to 5-minute resolution

A turbine has the following 10-minute wind speed data:

resolution_conversion_7.png

The conversion is done using the weighted average. However, since the device resolution is divisible by the target resolution, this ersults in each value being repeated.

resolution_conversion_8.png
resolution-dependent ()

Signals that are "resolution-dependent" are calculated for the specified resolution. If data is requested for a month, the calculation is done for that month.

For example, the formula for Performance Index is:

aggregating_data_example.png

But the Performance Index is not calculated per time step. It is calculated for the full month with n time steps. Therefore, the formula is:

aggregating_data_example_2.png