night ventilation

The interest in phase change materials (PCMs) as a solution for thermal energy storage has been growing for the last decades. It is clear that PCMs are promising for reducing the summer heat peaks without increasing the energy demand for cooling. A new modular, reversible, lightweight retrofitting system was developed and integrated in a real size experimental test cell.

The current type of construction preferred for new high energy efficient buildings in Germany, featuring highly insulated building components and an almost completely airtight building shell, raises several new challenges with regard to design, construction and use of these buildings. Cooling, in particular, is an issue that gains importance also in the residential sector, in connection with rising temperatures induced by the climate change.

With the combination of two fans and a heat exchanger in one single component there is the possibility to design a compact and highly efficient ventilation system especially for use in building modernization. One crossflow fan generates both airflows (outdoor/supply and extract/exhaust air) and simultaneously acts as counterflow heat exchanger. The space between the fan blades is filled with elements which operate as regenerative heat exchanger. The modified laboratory prototype of the so called Counterflow Heat Recovery Fan was optimized for the use as single/double room unit.

Night ventilation is used extensively as a low energy strategy to cool buildings in climates where night temperatures are suitable. It can be used for spaces utilising natural or mechanical ventilation systems as well as active refrigerant cooling. Most published work focuses on domestic and relatively simple in operation commercial buildings such as offices. This paper presents a study of the cooling benefits of night ventilation for frozen food supermarkets with high cooling demand.

An experimental analysis of the night ventilation technique for cooling in buildings, was performed in a test cell with the aim of establish the potential of this technique in two scenarios: a) when the air-stream is in poor contact with the thermal mass and b) when the air-stream is in close contact with the thermal mass of the test cell. The test cell is a small one-room building equipped with instrumentation for measurement and control the night ventilation following a strategy based in the values of indoor and outdoor temperatures.

Supermarkets are a category of non-domestic buildings with high energy use because of their operation. Recent work indicates that by improvements to the energy delivery systems through which internal environmental conditions are maintained such as thermal properties of external envelope including airtightness, HVAC systems and lighting, substantial energy savings can be achieved. Work to date has focused on typical supermarkets while the present paper examines frozen food supermarkets which include more refrigeration cabinets and therefore result in higher energy use per sales floor area.

Passive cooling by night ventilation is one of the most promising approaches to reduce cooling energy demand of office buildings in moderate climates. However, the effectiveness of this system depends on many parameters.

Night ventilation has been applied successfully to many passively-cooled or low-energy office buildings. This paper analyses the thermal comfort achievable in office buildings in Spain according to European standard EN 15251:2007. Furthermore, the comfort level is evaluated using the Degree Hours (DH) criteria and the maximum indoor temperature.

According to researchers, climate change is inevitable in the 21st century. As far as Greece is concerned, this climate change will be related to an increase in ambient surface temperature and to a decrease in annual precipitation. On the other hand wind patterns will not change significantly. Also, no significant changes are expected for global solar radiation. Regional climate models related to Greece show low uncertainties. The climate of Greece is typical Mediterranean with wet, cool winters and hot, dry summers.

As a passive cooling strategy, natural ventilation is an energy conservation technology with great developing potential. The typical technologies of natural ventilation include night ventilation and natural ventilation with heat storing materials. The factors which affect ventilation include technique parameter, climate parameter and building’s parameter. The natural ventilation in summer in a typical building in Changsha City, which locates in hot summer and cold winter area, was measured.