Tariq Muneer

Energy and environmental impact analysis of double-glazed windows

Abstract The embodied energy of the four main materials used in the construction of an inert gas filled, double-glazed window, of a given size, was quantified. The four main materials considered were infill gas (argon, krypton and xenon), timber, aluminium and glass. The energy requirements of the underlying manufacturing processes are also estimated for the processing of the finished product. The total embodied energy for argon, krypton and xenon cavity filled windows (1.2 m by 1.2 m standard tilt and turn window), was found to be 1031 MJ, 1539 MJ and 5531 MJ per window, respectively. For argon filled cavities, this leads to the production of 94.7 kg of CO 2 , 1.2 kg of SO 2 and 0.4 kg of NO x per window. The results presented in this paper are initial findings in the first stages of a complete Life Cycle Analysis (LCA) of double-glazed windows for sustainable buildings.

Evaluation of sunshine and cloud cover based models for generating solar radiation data

Abstract Solar radiation models based on meteorological parameters serve as the substitute to measured irradiation and illuminance data. Models originating from sunshine or cloud cover information constitute the two main classes of meteorological radiation models. Further improvements in the accuracy of these models is under research. One such approach, attempted by Page, has resulted in the formation of a model that utilises a combination of the above mentioned variables. This article briefly discusses the new combined approach and evaluates it against other models developed by the authors: the Meteorological Radiation Model (MRM) based on sunshine fraction and the Cloud Cover Radiation Model (CRM) based on cloud cover. Results show that Page’s approach is quite successful under overcast conditions. The MRM, however appears to provide better estimates under part clear and clear sky conditions.

Modelling light-pipe performances—a natural daylighting solution

Abstract Much research has been conducted looking at the advantages of using natural daylight for illumination of both domestic and commercial buildings. As an alternative to electric lighting, natural daylight, when exploited to its maximum potential, can be beneficial both economically and environmentally. There are many different applications that have been put forward as a way to maximise natural daylight—one of the most simple is the light-pipe. To investigate the effectiveness of light-pipes, a model is proposed that will predict the light levels resulting from a pipe of given dimensions. This report describes the method of predicting the luminous flux of light-pipes and also proposes methods of calculating, for overcast skies, the illuminance resulting from a given luminous flux. All data used has been obtained from measurements in the UK throughout the year for various locations. The data is therefore the result of actual sky conditions.

Models for obtaining solar radiation from other meteorological data

The application of solar energy requires a knowledge of long-term solar radiation and daylight data. Because of the limited availability of measured data, various formulae have been derived to compute the solar irradiance using other, more commonly available, weather data. In this article two such models are presented, MRM (meteorological radiation model) and CRM (cloud-cover radiation model). MRM requires hourly data for sunshine duration, dry- and wet-bulb temperature; while CRM requires only cloud amount. Both models can generate hour-by-hour data for horizontal global, diffuse, and beam irradiance. A brief comparison of the two models is presented. Results showed that MRM has the advantage over CRM, on account of its consistency with the measured data. Both models are now available via the Internet in the form of electronic spreadsheets.

A design guide for performance assessment of solar light-pipes:

Due to an increasing demand for an improvement in environmental conditions for living and a need for energy saving, development of daylight exploitation products has accelerated. The invention of light-pipes which bring natural light indoors where sunlight cannot reach without generating excessive heat is one such example. Mathematical modelling activities aimed at predicting the daylighting performance achievable by light-pipes with various configurations under all weather conditions in the UK are being undertaken. Two models, one for straight light-pipes and the other for elbowed light-pipes are described. The models enable estimation of daylight provision of the light-pipes with a high degree of accuracy i.e., R2 values of 0.95 and 0.97 for regression between predicted and measured illuminance were respectively obtained for the above models. The maximum Mean Bias Error (MBE) and Root Mean Square Error (RMSE) were -2 lux and 27 lux. A design guide for light-pipe assessment is presented that will obviate the need for use of mathematical models.

Evaluation of an all-sky meteorological radiation model against long-term measured hourly data

Abstract With the proliferation of cheap, high performance desktop computers, the building services profession is demanding detailed (hourly or sub-hourly) weather data for simulation, optimum plant sizing and design of buildings which may use passive solar and/or natural ventilation features. Even in a developed country, such as the United Kingdom, there is a dearth of measured long-term solar radiation and daylight data. Herein, a simple and precise meteorological radiation model (MRM) is presented, which enables computation of horizontal beam and diffuse solar radiation to be accomplished, given four basic meteorological parameters—hourly dry- and wet-bulb temperatures, atmospheric pressure and bright sunshine duration. These data are available worldwide for very many locations. The present model is of a semi-general nature as demonstrated by its applicability to ten widespread locations in the United Kingdom. The model enables computation of hour-by-hour insolation. Statistical analysis of 100 station-years hourly data indicates that the MRM can compute insolation with an average error of 9% for clear skies and 25% for overcast conditions. On a monthly-averaged hourly and daily basis, this error reduces to 3%.

Life cycle assessment of a medium-sized photovoltaic facility at a high latitude location

Abstract Performance of a 160 m2photovoltaic installation at the Napier Universitys Merchiston Campus, situated 3 km from Edinburghs city centre, is presented. The alternative current and direct current electrical outputs were recorded since the installation of the facility was completed in April 2005. An analysis of the efficiency of the facility, as well as energetic, environmental, and monetary life cycle assessments, using long-term meteorological data is presented in this article.

A New Method for Correcting Shadow Band Diffuse Irradiance Data

An instrument commonly used to measure diffuse irradiance is the polar-axis shadow band pyranometer. However, the shadow band that is used to prevent the beam energy from entering the pyranometer also obscures part of sky-diffuse irradiance. A correction factor must hence be applied to obtain as accurate as possible the estimation of the true diffuse irradiance. In this article, the development of a new model based on an anisotropic sky-diffuse distribution theory is presented. The proposed model is validated using two databases from different sites with various sky conditions. Drummonds method, which is based on geometrical calculation, is also examined using the same databases. Comparison of the results obtained through application of the proposed model, with those generated by Drummonds method shows that, for the case of Bracknell, UK the proposed method gives a root mean square error (RMSE) of 12 W/m2, as compared to Drummonds figure of 16 W/m2. For the case of Beer Sheva, Israel the proposed model produces an RMSE of 17 W/m2, while Drummonds procedure results in 23 W/m2. It has been demonstrated herein that the proposed method is not site specific.

THE MEASUREMENT OF VEHICULAR DRIVING CYCLE WITHIN THE CITY OF EDINBURGH

In this paper, the development of a driving cycle for the urban area of the city of Edinburgh is presented. The driving cycle was obtained from recorded data in actual traffic conditions, using the car chase technique. A new statistical method of analysing the recorded data was developed. The proposed TRAffic Flow IndeX (TRAFIX) enables the calculation of a representative driving cycle from the various measurements undertaken during two stages of experiments. Data from the City of Edinburgh Council traffic monitoring stations were weighted in proportion to traffic flows on the constituent driving routes. A comparison between the European ECE cycle and the presently proposed Edinburgh driving cycle (EDC) has also been made.

Quality control of solar radiation and sunshine measurements – lessons learnt from processing worldwide databases:

As a result of an exponential increase in the application of solar water heating, and more recently solar PV systems, measurement of the available solar radiation resource is gaining rapid momentum. New databases are being created and many of these are being made available via Internet. Up-to-date series of these data are also being sought by architects and building services professionals for better design of buildings. However, in many instances due care is not being exercised with respect to quality control of the measured dataset. Two major activities that utilized large databases of solar radiation, sunshine and cloud-cover have recently been concluded within Europe – the European Solar Radiation Atlas and the Chartered Institution of Building Services Engineers (London) Guide on ‘Weather and Solar Data’. This article provides an account of the research undertaken towards development of robust techniques for identi” cation of erroneous data and their substitution using validated methods for generating radiation and sunshine data. Such substitutions are required to complete the time-series of data when the latter are either con” rmed as being of questionable quality or are found to be missing due to station downtimes.