Assessment and modelling of energy use and indoor environment towards conservation in historical art gallery buildings

Abstract

This PhD study presents a set of non-invasive methods developed to assess and model the indoor environmental conditions and the building energy use in the National Galleries of Scotland (NGS). This was to meet three intentions, firstly, to provide a detailed and efficient guidance to the facility managers of such building type on the building’s indoor environmental performance with respect to artwork conservation standards, and energy performance with respect to benchmarks from official standards such as CIBSE. Secondly, to provide good practice guidance on latent energy investment towards maintaining indoor moisture conditions relative to conservation specifications. Motivation behind this moisture control was found to be the parameter which is the most critical to artwork conservation, and previous studies revealing the significant amount of energy costs associated to meet the demands of maintaining the adequate indoor moisture specifications. And thirdly, to provide a robust tool which can mimic the complex, non linear building system and provide forecasting with high speed and accuracy. This model also enables the building management to test various optimisation options, while attempting to reduce energy consumption in the building while adhering to artwork conservation standards. The assessment methods were developed following a large-scale refurbishment event in the NGS, and involved a post-renovation impact study. The latent energy investment was analysed with the help of a new weather feature variable, developed as a part of this study. This was named as ‘Humidity-Day’ (HD) concept, analogous to the Degree Day concept. Artificial Intelligence (AI) was employed to model the complex NGS building system and predict indoor temperature, RH and building energy consumption – Gas and Electricity. This directly catered to the need to test optimisation strategies to cut down energy costs without jeopardising the healthy conditions of delicate artworks housed in the building. The positive effects of refurbishment in the NGS were highlighted by performance indicators. An overall indoor environment improvement of 16% was observed, out of which maintenance of indoor RH improved by 4% and the same for temperature by 12%. Winters experienced the maximum overall indoor environmental improvement of 59%. The indoor stability assessed by newly developed fluctuation parameters for both hourly and daily cases highlighted that the NGS experienced stable indoor temperature and RH, especially after the refurbishment. In addition to the benefits to indoor environment, the refurbishment regime brought a cut-down in NGS gas consumption by 27%. The Humidity Day Concept was developed and applied as a global climatic indicator focusing on moisture extremes relative to conservation specifications. Next, the HD based humidification estimates were employed as a good practice indicator and the humidification action of the NGS in the year 2015 was checked for over-consumption periods in a year. It was observed that 33% of the time, there was overconsumption related to humidification, especially during the winter months. Maximum overconsumption was experienced during October and November, where the NGS humidifier load exceeded the good practice mark by up to two times. The system identification model of the NGS was tested with excellent accuracies of up to 99% correlation between predicted results and the actual recorded data. It is also concluded that ANNs are able to work with limited amount of building systems data (real data) readily available from the building management. The study further reinstates that the ANN based SI model can prove to be an ideal platform to investigate various optimisation strategies of the building operation in future, especially in the case of restrictive traditional building types where any retrofit solution needs a strong scientific backing of guaranteed success before practical implementation. In future, work will be done to further strengthen the Humidity Day concept and test the case of dehumidification by further working on some of the assumptions. Furthermore, sub-metering at the NGS will provide accurate data to help validate the findings, especially, the energy consumed by chillers and humidifiers during the winter months will give a required justification for the dehumidification figures obtained.