Papers

Next steps in the footprint project: A feasibility study of installing solar panels on Bath Abbey

Matthew J. Smiles, Adam M. Law, Adam N. Urwick, Luke Thomas, Lewis A. D. Irvine, Matthew T. Pilot, Alan R. Bowman, Alison B. Walker

Energy Sci Eng. 2022;10:892–902.

Published 20 January 2022

See the press release here

Reduction of the carbon footprint of historic buildings is urgent, given their exceptionally large energy demand. In this study, the performance and cost of a roof mounted photovoltaic system has been simulated for Bath Abbey, a grade I listed building, to test the financial viability of installing such a system. The electrical output of the panels was generated by the software package PVsyst with inputs such as the known dimensions of the Abbey, historical weather data, the orientation of the Abbey’s roof, module azimuthal and tilt angles and shading by the spire and roof features. An important result is that even though the roof is not shadowed by other buildings, shading causes a 19% loss of peak power. This model was used to determine a recommended configuration comprising 164 solar panels, separated into two subsystems located on two parts of the roof, each with an inverter. Its predicted electrical output, 45 ± 2 MWh generated in the first year of operation, formed the basis of a cost–benefit analysis. This system will become profitable after 13.3 ± 0.6 years and provide a profit of £139,000 ± £12,000 over its 25-year lifetime. Financial stress tests were performed for key assumptions to ensure that this result was true in all likely scenarios. This result shows that it is likely to make financial sense to install a photovoltaic system on a historic grade I listed building.

Quantifying polaronic effects on charge-carrier scattering and mobility in lead–halide perovskites

Lewis A. D. Irvine, Alison B. Walker, and Matthew J. Wolf

Phys. Rev. B 103, L220305

Published 25 June 2021

The formation of polarons due to the interaction between charge carriers and lattice ions has been proposed to have wide-ranging effects on charge carrier dynamics in lead halide perovskites. The hypothesis underlying many of those proposals is that charge carriers are ‘protected’ from scattering by their incorporation into large polarons. Following the approach of Kadanoff for scattering due to polar optical phonons, we derive expressions for the rates of scattering of polarons by acoustic phonons and ionized impurities, and compute the energy and angular dependent rates for electrons and holes in MAPbI3, MAPbBr3, and CsPbI3. We then use the ensemble Monte Carlo method to compute polaron distribution functions which satisfy a Boltzmann transport equation incorporating the same three scattering mechanisms, from which we extract mobilities for temperatures in the range 50–500 K. A comparison of the results with those of analogous calculations for bare band carriers indicates that polaronic effects on the scattering and mobilities of charge carriers in lead halide perovskites are more limited than has been suggested in some parts of the recent literature.