Trans RINA, Vol 155, Part C1, Intl J Marine Design, Jan - Jun 2013


these impacts [10]. Its use as a design tool, as shown in Figure 3 enables the amount of energy each auxiliary item is consuming at the point of use to be determined. Identifying the most energy intensive applications over the course of a year. This energy audit diagnostic tool, helped to determine the key challenges to be addressed by a designer in


order environmental footprint. to reducing the vessels Namely refrigeration, Lighting


and HVAC systems, which were the main electrical loading applications as shown in Figure 3 . This was also the case for a 110m monohull from the the findings of Roy et al[1] shown in table 1.


Although propulsive power dominates the energy profile of most


ships, it could be improved by 20% (fuel


efficiency) through hull optimisation programs [4], but with yachts being in harbour 75% of the time (Figure 4) and auxiliaries accounting for 22% of CO2 emissions, considerable gains could be made from the reduction of auxiliary electrical loads, which are in use all year round [1]. This identifies HVAC systems and associated HECA’s (High Energy Consuming Applications) as the key design issues from the perspective of ecological designers.


Deck


Water 4%


Appliances 2%


Lighting 17%


Security 0.25%


CCTV 1%


Bow


Thrusters 15%


Navigation Equipment 13%


HVAC 27%


Kitchen Appliances 19%


The passive design philosophy avoids the use of active methods of producing energy, such as solar or wind technologies. There are two reasons for this, the first is that efficiency is cheaper than supplying demand, if the overall efficiency increases then the level of end use benefits may be maintained even as the energy input declines. Rynn [10] supported this hypothesis by stating that if all Americans were to use more efficient fridges, then the energy reduction would allow for 24 reactors to be shut down.


The second reasons is that, mechanical air handling equipment despite recent advances in efficiency includes components that adds significant initial costs to a build including: fans; filters; heating and cooling coils; vertical distribution shafts and ducts; horizontal distribution networks; dampers; reheat boxes; supply diffusers; return grilles. In addition to these mechanical systems are the electrical circuitry and sensors which control the HVAC system, all of which carry a high degree of embodied energy[13]. More particularly copper pipes and other copper parts contribute to the greatest environmental impact [13] as indicated by a life cycle analysis of heating and air conditioning systems.


Passive design on the other hand requires no active systems and completely relies on the environment to provide heating, ventilation and cooling. It is integrated into the structure and incorporated through the careful planning and


design of the structures external


morphology, thus incurring no additional construction costs and because of the minimal components, a lesser embodied energy than traditional HVAC systems.


Media 2%


3


IMPLICATIONS OF DESIGN ON THE COOLING LOAD


There is a proportional relationship between heat gain and cooling loads. The basic assumption would be to reduce heat gain in order to reduce the amount of energy consumed by the HVAC system, thus driving down its need, size and use.


Figure 3: Energy Audit of a 110ft catamaran [1].


Maximum speed, 7%


Cruise Speed, 15%


Manouve- ring, 3%


At


Anchor/in port, 75%


Sources of heat gain vary depending on geographical location. In the Logos project [2] windows, depending on their orientation were the greatest sources of heat gain. This is certainly true for solar homes in cooler climates; where the intention is to warm the interior volume through direct sun light & the transmittance of heat through conduction, convection.


radiation and consequently Figure 4: Operational profile of a Luxury yacht [2].


However, in warmer climates it is the objective to cover or reduce solar collectors such as windows, to prevent solar heat gain from adding to the cooling load within the interior. Observations of current yachts on the market indicate a design trend toward more glass in an effort to immerse the user in the marine environment. This will result in a greater cooling load. The proportionality between the amount of glass and the HVAC load is case


©2013: The Royal Institution of Naval Architects


C-27


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