Akritas, P;
(2007)
A comparison of daylight measurement using radiance.
Doctoral thesis , UCL (University College London).
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Abstract
This dissertation compares the daylight coefficient approach for predicting time varying illuminance to a new method formulated by Peter J. Raynham based on the sunlight and daylight factors. The accuracy of the daylight coefficient derived illuminance predictions was verified by John Mardaljevic using the BRE-IDMP validation datasheet. The prediction tool used for all the work described here is the Radiance lighting simulation system. Hourly predictions of daylight illuminance over a period of one year under variable sky and sun conditions were carried out for a full-size office space using both methods. The total annual klux-hours were then calculated, providing a simple metric to compare the two methods. It has been demonstrated that Raynham's method and that of Mardaljevic diverge in terms of their results, with the difference becoming much more significant further away from the windows. It can therefore be deduced that Raynham's method can not be used to predict hourly internal illuminance levels. Raynham's source of error is that he assumes an overcast sky to determine the diffuse component which has a dark horizon and brighter zenith with ratio of about 1 to 3. Thus, his method puts a lot of light higher in the sky as opposed to the ground as is the case of a clear sky. It is impractical to also assume that the daylight coefficient approach is the ideal standard by which any potential method for predicting time varying illuminance should be compared against. The accuracy of this method is based on one set of results, and there are various sources of imprecision which could prove to be significant when the daylight coefficient approach is examined for a different locale.
| Type: | Thesis (Doctoral) |
|---|---|
| Title: | A comparison of daylight measurement using radiance |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1566877 |
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