Theoni Karlessi

A surface heat island study of Athens using high-resolution satellite imagery and measurements of the optical and thermal properties of commonly used building and paving materials

High-spatial resolution multispectral satellite images collected over the metropolitan Athens area in Greece were used to generate (a) a shortwave albedo map depicting the albedo spatial variations across the metropolitan area, (b) a fractional vegetation cover map showing the spatial distribution of urban vegetation and (c) a daytime and night-time land surface temperature (LST) map depicting the spatial variations of the surface temperature across the city. From LST maps, cooling and heating regions were identified and analysed to reveal relationships between surface heat islands and urban surface characteristics. Based on the data acquired with the use of satellite images and in order to better define the heat island problem and the mitigation measures that need to be taken, the most common building and paving materials used in the urban fabric of Athens were examined. Their optical properties were measured using a UV/VIS/NIR spectrophotometer fitted with an integrating sphere, an emissometer and their thermal performance was evaluated. Furthermore, measurements of the spectral reflectance help explore the possibility of increasing the near-infrared reflectance of materials in order to increase their total solar reflectance. The solar reflectance index of the samples was calculated in order to characterise them as ‘cool’ or ‘warm’. Cool materials, with high albedo and thermal emittance values, attain lower surface temperatures when exposed to solar radiation, reducing the transference of heat to the environmental air.

Passive Solar Architecture

A building’s energy consumption is a major source of greenhouse gas emission and one of the main causes of climatic change. Passive solar architecture relies on the use of techniques for solar and heat control, heat amortization, and heat dissipation. Solar and heat protection or exploitation techniques may involve thermal improvement by the use of outdoor and semi-outdoor spaces, layout and external finishing, solar control and shading of building surfaces, thermal insulation, control of internal gains, and so on. The aim of this chapter is to present an overview of solar architecture starting from its history and provide a short description of the solar architecture basics, followed by an account of the state-of-the-art developments regarding the building fabric, cool materials, and intelligent control techniques. The future research trends are revealed and discussed here.

Performance prediction and design optimisation of an integrated light pipe and artificial lighting system

This paper describes recent research on the prediction of the performance of light pipes and the ways to optimise their design, in order to house artificial lighting, able to supplement daylight in a space. The research has resulted in an algorithm, for the easy and quick calculation of the interior illuminance provided by light pipes, and in a procedure for the calculation of the power of the necessary artificial lighting (light emitting diodes [LEDs]) and the energy savings for lighting, due to the daylight provided by the light pipes and the daylight linked controls of the LEDs.