Michael J Tierney

Low-energy dwellings: the contribution of behaviours to actual performance

The UK Governments Building a Greener Future: Policy Statement (2007) announced that all new homes must be zero carbon from 2016. To date, a number of housing sites around the UK have strived to reduce carbon emissions by following sustainable design principles and utilizing renewable technologies. On paper, these sites exceed regulatory compliance and are regarded as high-performance buildings. However, their actual performance is seldom validated from the perspective of either the design engineer or the occupants. Findings are presented from an on-going post-occupancy evaluation of a UK EcoHomes site with an ‘excellent’ rating (the highest rating of the predecessor to the current standard, the Code for Sustainable Homes). The detailed post-occupancy evaluation investigated the energy performance of the buildings (as well as water consumption) and the comfort and satisfaction of users. A bespoke behavioural survey and interview were developed and implemented to distinguish between and quantify frugal and profligate patterns of consumption. Results indicate that energy-efficiency behaviours account for 51%, 37%, and 11% of the variance in heat, electricity, and water consumption, respectively, between dwellings. Human factor issues need to be addressed more adequately as standard practice in low-energy/carbon design. La déclaration de principe du Gouvernement Britannique intitulée Building a Greener Future: Policy Statement (Construire un Avenir Plus Vert: Déclaration de Principe) (2007) annonçait que tous les nouveaux logements devraient être zéro carbone à compter de 2016. A ce jour, un certain nombre d’ensembles d’habitation à travers le Royaume-Uni se sont efforcés de réduire les émissions de carbone en suivant des principes de conception durable et en utilisant des technologies renouvelables. Sur le papier, ces ensembles d’habitation vont au-delà des obligations réglementaires à respecter et sont considérés comme des bâtiments à hautes performances énergétiques. Néanmoins, leurs performances réelles sont rarement confirmées du point de vue de l’ingénieur concepteur ou des occupants. Sont présentés les résultats d’une étude en cours relative à l’évaluation après occupation d’un ensemble d’habitation britannique EcoHomes classé « excellent » (la notation la plus élevée prévue par la norme antérieure à la norme actuelle, Le Code pour des Logements Durables). Cette évaluation détaillée après occupation a examiné les performances énergétiques des bâtiments (aussi bien que la consommation d’eau), ainsi que le confort et la satisfaction des utilisateurs. Il a été élaboré et procédé à une enquête comportementale sur mesure, avec entretien, afin de pouvoir faire la distinction entre les habitudes de consommation économes et dépensières et de les quantifier. Les résultats indiquent que les comportements éco-énergétiques représentent respectivement 51 %, 37 % et 11 % des différences de consommation de chauffage, d’électricité et d’eau entre les logements. Dans une conception basse énergie/bas carbone, il est nécessaire qu’un traitement plus adapté des questions liées aux facteurs humains devienne pratique courante. Mots clés: performances des bâtiments, évaluation de la consommation, logement, bâtiment basse énergie, comportement des occupants, évaluation après occupation, théorie des comportements planifiés

Analysis of a Finned Heat Exchanger Working in an Adsorption Refrigeration System Using Zeolite and Methanol

A new refrigeration system that uses a specially designed finned plate heat exchanger and works with zeolite and methanol is proposed. The integration of heat transfer and adsorption via a finned surface coated with zeolite CBV 901 and the use of a connected, twin active bed system to enable heat recuperation are novel features. The thermophysical properties of zeolite and methanol were first studied with the intention of designing a high performance heat exchanger (generator) for the adsorption refrigeration system. Here, the major problem is related to poor conductivity at the interface between the heat exchanger and the zeolite. The adsorbent must be heated (desorption phase) and then cooled (adsorption phase) back to ambient temperature in order to complete a thermodynamic cycle. To manufacture a sufficiently small system, there must be high rates of heat transfer in and out of the adsorbent. Therefore, the surface of the heat exchanger is finned in order to increase the heat transfer area (the fins are coated with 2 mm layer of specially prepared zeolite paste). The following characteristics were estimated from initial calculation: heating temperature, 120°C; outside tube temperature, 119.6°C; middle fin temperature, 117°C; and coated layer of zeolite paste temperature, 115.3°C. The mathematical code developed to calculate the effects of operating conditions and the Coefficient of Performance (COP) was presented at HPC 2001 in Paris. It is based on the Dubinin-Astakhov equation and thermodynamic analyses. The results obtained shows that 0.535 is the COP for a single bed and 0.925 for a double bed.

Calorimetric Assessment of Rates of Desorption

This paper concerns the further testing of a new double calorimeter. We earlier reported initial development of the calorimeter and thereafter inferred rates coefficients for adsorption of moisture under a “large pressure jump.” (The test materials were silica gel type A and water.) The paper presents a further check on the calorimeter by demonstrating that measured desorption and adsorption rates were compatible. A disappointing aspect was an unintended near step change in condenser pressure at the start of the experiment. The condenser design was deficient, and better drainage is needed in the future to maintain vapor in immediate contact with cold surfaces. Notwithstanding the lower than intended pressure driving force, the heat addition to the silica gel was measurable, following an exponential pattern against time with regression coefficient better than 99%. The rate coefficients that fitted each data set were broadly in line with coefficients reported for adsorption (within the limits of experimental error).

A photovoltaic panel modelling method for flexible implementation in Matlab/Simulink using datasheet quantities

This paper presents a detailed method for creating an embedded Matlab model in Simulink for any solar photovoltaic panel starting with its datasheet values. It links extrinsic functions to the Simulink embedded model to provide fast and simple iterative solving of non-linear equations. It also provides a method sufficiently flexible to produce a model output based on panel current or voltage such that it can be cascaded with different Simulink elements.

An assessment of the containment performance of a ventilated enclosure in the pharmaceuticals industry using experimental and predictive techniques

Due to guidelines issued by government health bodies, concerns over personnel safety, and a desire to maintain the quality of manufactured products, containment is becoming increasingly important in a growing number of different industrial contexts. By isolating hazardous materials, a containment system should reduce to acceptably low levels the potential dangers posed to human health and the surrounding environment. During manufacturing processes, it should also assist in the protection of these materials from outside contamination. In this paper, a ventilated containment booth at a pharmaceuticals plant is analysed. This booth is used to contain active powders whilst they are tipped into a reactor for drug manufacture. Experimental data regarding the air flows within the system is compared with numerical predictions generated using computational fluid dynamics (CFD). The agreement is good and the predictions highlight the flow dynamics of the system. The use of CFD is then extended to provide indicators of containment performance for a range of different operational characteristics. These indicators, based on the ventilation performance of the system, and on the ability of the air flow at the hatch face to isolate hazardous materials from the working environment, clearly show the deficiencies associated with the current system. However, they also indicate that certain modifications to the location of the extraction ducting and the rate of air extraction could yield substantial benefi ts in terms of the overall containment performance of the device.