English

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.

Heat island which is the most documented phenomenon of climatic change is related to the increase of urban temperatures compared to the suburban. Among the various urban heat island mitigation techniques, green and cool roofs are the most promising since they simultaneously contribute to buildings’ energy efficiency. The aim of the present paper is to study the mitigation potential of green and cool roofs by performing a comparative analysis under diverse boundary conditions defining their climatic, optical, thermal and hydrological conditions.

The need for more energy efficient Heating Ventilation and Air Conditioning systems led to a search for new systems for heating, cooling and ventilation of buildings. Strong reduction of energy consumption within the built environment is necessary because of the growing effects of depletion of fossil fuel and global warming. This lead to a almost standard concept of energy efficient office buildings in the Netherlands. That concept exists of heat pumps and  LTES aquifers combined with thermally activated building systems (TABS).

In a Dutch project the double façade became an integral part of the ventilation concepts aa well as the heating system by trying to optimize the heat gain within the cavity during spring and autumn. The study shows how variable facade parameters influence the energy flows coming through the facade, in order to optimize the indoor environment for the comfort of the individual occupant. How can the facade make optimal use of the free incoming energy flows to maximize the comfort level of the individual building occupant at minimal energy use?

The aim of this paper is to experimentally investigate and analyze the thermal and optical behavior of a Green Roof System (GRS) installed in the 10000 m2 roof of a fully insulated, bioclimatic office building in Peania. More specifically, during the experimental procedure, measurements of the outdoor temperature and relative humidity have been performed, as well as of the air temperature inside the building and the surface temperature of the ceiling.

Cool roof coatings remain cooler than absorptive roofs and thus predominantly are used in buildings that require the reduction of the indoor temperature and the cooling loads. Cool roofs can also reduce the ambient temperature. A currently contentious aspect of solar reflective cool coatings is the extent to which an initially high solar reflectance decreases with time.

An urban park located in a densely built area of  Western Athens, Greece is monitored. Temperature data from 15 urban and suburban stations are also used to perform comparative analysis at the city level. The park presents an important temperature inhomogeneity during day and night due to the variable radiative cooling capacity and shading potential between its various zones. Average nocturnal Cool Island Intensities (CII) against the reference urban stations varied between – 0.7 K to – 2.8 K while during the daytime the maximum CII was between -0.2 to -2.6 K.

Τhe present article deals with the development and testing of photovoltaic pavement for heat island mitigation. The scope of this study is to evaluate its contribution to the balance of the Urban Heat Island phenomenon. For this reason, we made a photovoltaic pavement for purely experimental reasons (dimensions 3.5x1.3m) that consists of two different voltage polycrystalline photovoltaic panels. On top of them, a triplex security glass with a nonslip silk screen, PVB standard 1.14 mm was placed.

The present article deals with the energy classification and the environmental evaluation of the school buildings in Greece. The energy performance of the school buildings, in relation to the normalized annual consumption for heating regarding floor area and climatic conditions, was rated using clustering technique (K-means algorithm) and an energy classification tool developed. The audited school buildings were classified into five energy categories.

The improvement of the urban microclimate combined with the reduction of the energy loads is a highly important target that requires the research and development of innovative solutions with advanced thermal and optical properties. Color changing thermochromic coatings being reflective in summertime and absorptive in wintertime can address to the demand of lower surface temperatures and lower cooling loads. The interaction though with the solar radiation results in the breaking of the chemical bonds and the degradation of their performance.