Jul 2016
Electricity Distribution
Solar PV Forecasting Phase 2
Jul 2016
Jul 2018
National Grid Electricity System Operator
Andrew Richards
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Network Innovation Allowance
ED - Network improvements and system operability
Carbon Emission Reduction Technologies, Distributed Generation and Modelling
The scope of this project is both to understand the variability of solar generation and to improve solar PV generation forecasting in the medium and short term.

Analysis of solar generation will be focused on both regional and GB-aggregated solar PV generation and load factors. Historical assessment will consider 34 years with a resolution of 1 hour and above

At short timescales radar and satellite data and solar generation data driven statistical methods will be utilised to improve solar forecasts derived from NWP models, this work is distinct from, though intended to complement, prior activity that NGET have commissioned to access real time PV generation.

The variability of GB-aggregated solar generation will be assessed based on a newly derived long term dataset (described in work package1); this will have an hourly resolution and run for at least 34 years. This data will be analysed to quantify the magnitude and frequency of a range of solar generation events.

The analysis will focus on two types of low probability events of particular interest:

  • Persistent generation, where the combined solar and wind generation remains above/below a certain threshold for a prolonged period.

  • Transition and ramping events, where the solar generation is rapidly changing.

The purpose of this project is

  • To derive datasets and specific knowledge of characteristics of solar PV generation in terms of variability, ramping and persistence, and the joint characteristics of how the solar resource interacts with the wind resource,  that will inform planning decisions and procurement of balancing services within NGET.
  • To develop new models for converting solar irradiance into generated solar PV power.  This will improve the accuracy of both solar generation and transmission demand forecasts and hence expenditure on constraint management and reserves.
  • To improve short term solar generation forecasts

  The objectives of this project can be considered in the following specific areas.

Variability of solar irradiance and its correlations with other meteorological variables

As part of work package 1, NGET will be provided with a 34-year time-series of synthetic GB-aggregated solar irradiance, wind speed and temperature and an accompanying report. This will provide details of the variability in solar irradiance and frequency and duration of extreme and unusual events over a range of time scales; including decadal, annual and seasonal. In addition it will highlight the frequency and magnitude of ramping events. This will allow current events to be placed in historical context and enable a better insight of the potential impacts of solar PV generation on the power system. The data also could be used in combination with data provided in a previous NIA project (NIA_NGET0016: UK-wide wind power resource: Extremes and variability), to consider extreme events associated with combined wind and solar generation.  This information could be harnessed for operational planning or for investigating future energy scenarios.

Develop improved transfer model for solar power generation;  determine characteristics of solar generation and interaction with wind generation and demand variability
The objective of work package 2 is to provide NGET with improved models for converting solar irradiance into solar generation power. This will improve the solar generation forecasts and the transmission demand forecasts. Using the results from Work Package 1 a joint time series of solar load factors, wind load factors and demand at regional and aggregated GB levels will be provided. A report will be presented detailing statistical characteristics, both individually and jointly of the renewable resources, focussing on variability, ramping and persistence.  A library of extreme or difficult events on the transmission network will be included.

Assess the possible improvements in  short term solar radiation forecasts
On completion of work package 3, a report will be presented to NGET detailing the use of remote sensing techniques and statistical techniques driven by near-real time solar generation data in improving short term solar forecasts.

This project will provide knowledge that; (1) enables a better insight of the potential impacts of solar PV generation on the power system, at planning time scales and also for assessing tools needed within balancing services (2) improves medium and short term solar generation forecasts and hence demand forecasts . This activity will contribute to cost reduction in an area of high strategic significance. However, the full attribution of constraint and balancing costs is highly complex, rendering any estimate of direct cost benefit misleading at best. Success of this project will be evidenced by availability of solar generation information within the operational planning process. This information can be aligned to three main objectives; (1) Greater awareness and use across NGET of impact of solar generation variability and its interaction with wind generation and demand variability for use in network and commercial planning [WP 1 and 2] (2) Improved medium term solar generation forecasting for use in operational and commercial decision making [WP 2] (3) Improvements in short term solar radiation forecasts to improve operational decision making [WP 3].