Trans RINA, Vol 155, Part C1, Intl J Marine Design, Jan -Jun 2013
specific, but in some cases large amount of glass can have a physical effects on the interior, as shown in Figure 5 .
rates. In addition a number surrounded by glass.
of these areas were
Having identified the relationship between these design factors and cooling loads, design guidelines could be embedded within the design workflow to help inform design decisions at a very early stage. Design guidelines would also need to convey the idiosyncrasies of the relationship between the interior and the exterior to support
the 4. Figure 5: Observed interior blistering [2]. development of a homeostatic
THE POTENTIAL BENEFITS OF PASSIVE DESIGN OVER CONVENTIONAL HVAC SYSTEMS
Passive design has resulted in the creation of Net Zero Energy buildings, in some cases demonstrating the complete elimination of air conditioning systems. Given the similarity of large interior volume between yacht and commercial buildings, passive design ventilation could be effectively implemented
user
environment. This could be achieved through a best practice passive design process [15].
and natural within
Figure 6: Analysis of 3D by a virtual sun [2].
Using a virtual sun to analyse the response of the internal and external morphologies in relation to the sun can be explored through CAD software. An analysis of a 3D model inside the Google-Sketchup software, is shown in Figure 8, being interrogated by a virtual sun at different times of the day. Including the winter and summer solstice at Barbados and around the South East coast of America. This operational site specific analysis is critical to achieve effective PD implementation, given the potential variation in location and orientation of a vessel. This analysis can be used to identify potential high heat gain areas and thus inform the design process to either compensate through adjusting the exterior design through louvers and overhangs or by ensuring that materials with high thermal inertia are not present or well insulated [2].
Otherwise the interior is at risk of experiencing high heat gains during the afternoon, forcing the occupant to turn on the Air conditioning with a high cooling load [14].
The CAD based analysis of catamaran interiors with a virtual sun [2] has indicated that in some cases materials with a high degree of thermal inertia were placed next to windows which were slanted inwardly, allowing for the surface to be fully exposed to the sun (Figure 6). Identifying
the need for design compensation
marine platforms. A proposed configuration of a naturally ventilated multihull using a solar chimney roof composed of ETFE cushions is shown in Figure 7. It has a well-insulated black body roof, which acts as a solar collector heating the air trapped between the roof and the ETFE cushions. This heated air rises due to the buoyancy effect and escapes through the chimney (the mast), which keeps the air warm until it escapes through the top of the mast.
The basic equation used to establish the impact of the stack effect (Equation 2), indicates that the effects of air movement is dependent on the difference in height and temperature [12]. The morphology of the catamaran with its large surface area available on the roof and the tall mast means that this method of ventilation could be potentially very successful, as the catamaran structure lends itself to passive solar cooling.
as
previously discussed. Kvilums [2] in the benchmarking analysis of sailing multi-hulls using a virtual sun, reported that in some cases galleys and high heat appliances were placed in areas with high occupancy
Figure 7: Proposed catamaran natural ventilation system using a solar collector on the roof [2].
∆ = ∙ ∙
− ∙ ∙∆ℎ ...(2)
Po= Reference pressure at (kg/m3) To= Reference temperature (K)
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©2013: The Royal Institution of Naval Architects
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