Exergy analysis

Energy performance of mechanical ventilation systems in modern low energy and passive buildings is a crucial factor influencing overall energy performance of building. Energy balance is commonly used tool in evaluation of mechanical ventilation systems. In the case of low energy and passive buildings that tool might be insufficient and should be replaced by exergy analysis taking into account the first and the second Law of Thermodynamics. The paper presents principles of exergy evaluation of mechanical ventilation systems and case study calculations for an office building.

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.

Photovoltaic-thermal (PV/T) systems integrate photovoltaic and solar thermal technologies into onesingle system with dual production of electricity and heat energy. There are alternative designs to suitdifferent applications. For a given collector surface area, the overall system energy performance ishigher than the conventional "side-by-side" PV and solar thermal systems. This helps to promote PVsince the economic payback period of PV/T is much shorter. In this paper, the various water-basedPV/T systems and products are reviewed.

It is often claimed that energy is consumed, not only in everyday conversation but also in scientificdiscussions associated with energy and environmental issues. This claim conflicts with the first law ofthermodynamics stating that the total amount of energy is conserved, even though forms of energymay change from one to another.

There is an obvious and indisputable need for an increase in the efficiency of energy utilisation inbuildings. Until now, so-called energy saving measures and analyses of energy flows in buildings havecommonly been based on the energy conservation principle, the first law of thermodynamics.