Presentation Details
| Is IEC-61853 testing useful for predicting the energy yield of tandem solar cells? Rajiv Daxini, William E McMahon, Robert Witteck, Emily Warren. National Laboratory of the Rockies, Golden, CO, USA |
Abstract
Modeling the energy yield of tandem photovoltaics (PV) is essential for optimizing device design, fault detection, and bankability assessments. Current state-of-the-art tandem energy yield models rely on non-trivial measurements and detailed device stack information. In contrast, simple device characterization procedures exist for single-junction PV. For example, the IEC-61853 testing procedure in which performance is measured under a range of temperature and irradiance conditions. The IEC approach is complemented by models that take its output directly as an input to estimate field performance. The absence of spectral variation in the testing procedure is accounted for by spectral correction factors, but whether this is adequate for tandem devices---the performance of which depends heavily on spectral variation---requires investigation. We find that the IEC-61853 testing procedure is not useful for tandems in the context of energy yield modeling, primarily due to inadequate consideration of spectral variation. By generating IV curves for a two-terminal two-junction tandem device under 22 temperature and irradiance conditions, as suggested in IEC 6185-1, we determine that the majority of energy yield models relying on the single-diode model cannot fit the IV data. Two approaches, namely the ``ADR'' model and the Sandia-PVSyst 2025 model successfully extract parameters from the IV data, but overestimate energy yield over the course of a year by over 3% annually and, on a monthly basis, deviate by up to +24% / -8% from a baseline energy yield calculation using a full double-junction equivalent circuit model.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
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