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Overview

The aim of the project is to provide the metrological infrastructure, techniques and guidance to accelerate time-to-market for emerging photovoltaics (PV) technologies, which have the potential to significantly reduce the cost of photovoltaic energy.
The project has two main objectives: Firstly, to improve the PV energy rating standards and secondly, to improve the measurement equipment and methodologies to enable precise measurements of the parameters required for the energy rating.


Need

According to the United Nations Framework Convention on Climate Change COP 21 in Paris, anthropogenic greenhouse gas emissions must be reduced drastically [1]. As direct combustion of fossil fuels is reduced, renewable energy sources will cover the energy needs to the greatest extent – directly in individual sectors such as heating or in the form of renewable electricity, particularly from wind and solar energy. It is estimated that by 2050, electricity will cover roughly 50 %f of all our energy needs – compared with around 25 % today. Renewable electricity will increasingly be used to drive cars, generate heat and produce goods in factories, and in doing so primarily use technologies that replace a large amount of fuel with a small amount of renewable electricity [2]. To minimise costs of energy storage, around one third of the renewable energy will be produced by photovoltaics.
Currently PV modules are optimised, selected and sold on the basis of power produced under standard test conditions (STC). However, this metric does not always reflect real-world conditions as location-dependent variations in ambient temperature, irradiance, angle-of-incidence, spectrum and wind-speed cause deviations in annually-averaged module efficiencies of up to 20 %. This impedes the uptake of emerging and innovative technologies, such as modules optimised for specific climates.
A new set of standards, IEC 61853, provides a framework for energy rating of PV, including measurement, modelling and reference meteorological data. The recent Opens external link in new windowEMRP ENG55 PhotoClass project has been instrumental in completing these standards and has provided:

  • An enhanced European infrastructure for traceable energy rating: Improved measurement accuracy, development of new reference devices, and devised new techniques to reduce costs
  • An improved framework for energy rating and yield calculations including open-access meteorological datasets and models for evaluating energy rating and uncertainty
  • Final decisions or completed drafts for all four parts of the energy rating standard. IEC 61853-2 has already been published and IEC 618532-3 and IEC 618532-4 are at the committee draft (CD) stage.

These outcomes have made a great first step towards universal energy rating of PV modules. In the meantime, stakeholders have identified a number of remaining challenges arising from emerging technologies and market trends:

  • Bifacial modules – these claim to increase energy yields by 10 % - 20 % by harvesting light from the rear of the panel, yet investors are nervous about the lack of standard tests and rating methods
  • PV modules on buildings – differences in operating conditions compared to ground-mounted PV are not reflected in the current standards
  • Module characterisation – to improve uptake of energy rating, there is demand to make use of new technology (such as LED simulators) for fast and accurate characterisation at the module scale and harmonise handling of test data

To achieve the target increase in photovoltaics as a source of electricity requires a large Europe-wide increase of PV installations by several 100 GW, with an associated investment cost of several 100 billion Euro. Thus, every percent measurement uncertainty in energy yield estimation leads to a financial uncertainty of several billion Euros. The most commonly used efficiency and peak power characterisation under STC does not allow for differentiation according to the most relevant parameter in the marketplace which is energy production under specific climatic conditions. This is particularly relevant in Europe where PV systems of different technologies are operated over a wide range of climatic conditions. Thus, we need a precise metrology and realistic, representative standards for PV as one of the most important future energy sources.