PR2013

Utilizing a cool roof is an efficient way to reduce the cooling energy use of a building. Cool roofs, however, may increase heating energy use in winter. In cold climates, during the winter the sun angle is lower, days are shorter, sky is cloudy, and most heating occur during early morning or evening hours when the solar intensity is low. In addition, the roof may be covered with snow for most of the heating season. All these lead to a lower (than what is commonly thought) winter time heating penalties for cool roofs. 

The nighttime ventilation strategy uses the outdoor cold air during the night to cool the building mass. The cooled building mass then is used as a heat sink during the next hot day. Mechanical nighttime ventilation requires a fan for the outside air ventilation. The energy use by the fan reduces the potential cooling energy savings. Higher nighttime ventilation flow rate and its duration decrease required cooling energy during next hot day in the building, also they increase fan energy consumption.

This research aims to investigate, analyse and characterize the relation between the economic crisis and energy consumption in Greece. A survey held in the spring and summer of 2012 collected data of the heating energy consumption for 2010-2011 and 2011-2012, from 598 households via a questionnaire. Comparing the 2010-11 winter to the harsher winter of 2011-12 showed that inhabitants consumed less energy during the winter of 2011- 12 because of the rapid economic degradation.

The present paper deals with the application of 4500 square meters of reflective pavements in an urban park in the greater Athens area. The aim was to improve thermal comfort conditions, reduce the strength of heat island and improve the global environmental quality in the considered area. It was estimated that the use of cool pavements contributes to decrease the peak ambient temperature during a typical summer day, up to 1.9 C. In parallel, the surface temperature in the park was reduced up to 12 C while comfort conditions have been improved considerably.

Heat island phenomenon rises the temperature of cities, increases the energy demand for cooling and deteriorates comfort conditions in the urban environment. To counterbalance the impact of the phenomenon, important mitigation techniques have been proposed and developed. The use of cool pavements presenting substantially lower surface temperature and reduced sensible heat flux to the atmosphere, appears to be one of the most important proposed mitigation solutions. The present paper investigates and describes the actual state of the art on the field of cool pavements.

Urban heat island (UHI) phenomenon has been observed in many populated cities located in cold regions (e.g., Montreal in Canada) during summer. One of the well-known strategies to mitigate the temperature rise of urban areas is increasing their albedo. Roofs cover about 25% of urban areas and increasing their reflectivity would have significant effect on the total energy budget of a city. Changing the surface energy budget can directly affect the air temperature near ground and the vertical wind speed.

Rejection of solar gains is the aim of passive cooling strategies in any type of building and any climatic region. The extent of cool materials usefulness is dependent on the severity of external conditions and internal heat gains. The aim of the present paper is to underline the contribution of an innovative cool fluorocarbon coating in the reduction of energy demand for cooling in an industrial building with increased heat gains under temperate climatic conditions. The material is tested using accelerated weathering procedures and its optical properties, i.e.

We have developed a new evaluation method of “thermal radiative power” (TRP) for investigating the impact of building surface material albedo on urban environment. The simulation system ENVI-met is used. This system is a 3D computer model which analyzes micro-scale thermal interactions within urban environments. It simulates urban-scale environmental conditions such as roofs, exterior wall, and ground surface temperatures. Focuses of this research are on the climate change in urban and community scale in cold climates.

The present study deals with the feasibility of Flywheel Energy Storage Systems (FESS) in several RES-based stand-alone electricity production systems. Energy buffering is necessary in any RES-based off-grid system, however conventional energy storage systems (batteries, hydrogen etc.) suffer from limited equipment lifetime, high initial costs, and negative environmental impact during their operation as well as after their life-cycle.

Fuel cells are highly efficient energy conversion systems that have recently gained significant interest in terms of both science and applications. Exergy analysis is adopted here for a power plant involving SOFC with external steam reforming that is fuelled by modeled biogas/steam mixtures. The electrical efficiency has been estimated and the effect of various operational parameters on the process efficiency has been investigated.