Industrialised, Integrated, Intelligent sustainable Construction - I3con

HANDBOOK 2 SUSTAINABLE CONSTRUCTION
Ventilation
A ventilation unit contains three components that play an important role in the provision of fresh and
conditioned air: an air to air heat exchanger (number 2 in Fig. 1), two fans (numbers 3 in Fig. 1) and a
stack of PCM (Phase Change Material) plates with a phase change temperature range of 20-22°C
(number 1 in Fig. 1). Fresh air is drawn directly from outside, preheated by the heat exchanger and
then forced through the PCM plates before being distributed into the indoor environment. Stale air is
drawn from the indoor environment at the top end of the ventilation unit, forced through the heat
exchanger where thermal energy is exchanged with the incoming outdoor air, before being discharged
to the outside.
Users are given the option to manually open the window for additional ventilation, providing the
psychological advantage of being able to control their immediate environment.
Light
The part of the façade above the ventilation units is almost fully transparent. This is beneficial for two
reasons: 1. provision of daylight which reduces the need for additional artificial lighting, and 2. the
reduction of glare caused by large luminosity differences between transparent and non-transparent
parts of the facade.
To prevent potential overheating in summer, the façade should be equipped with high quality shading.
In theory, any shading device can be used, as long as its performance is able to match the performance
criteria set in this paper.
Heat/Cold
The acclimatisation of the indoor temperature works in a number of ways: first of all, the façade is
supposed to be well insulated and air tight. This way, the façade can use indoor heat loads (people,
equipment and lighting) in combination with controlled ventilation to create a comfortable indoor
environment for almost 80% of the year.
The ventilation air exchanges thermal energy with the PCM plates by flowing along the surface of the
plates. Since the plates have a relatively constant temperature of 20-22°C, the air flowing along the
plates is either heated or cooled, depending on the outdoor temperatures.
The PCM has both a heating and cooling task, depending on the outdoor temperature. In summer, the
PCM cools fresh outdoor air down to roughly 22 degrees during the day to use for ventilation and
cooling, while using night ventilation to regenerate its cooling capacity during the night. In winter, the
PCM heats up the incoming ventilation air during the day, while at night, when necessary, electric
heating coils or Peltier elements (TEC – thermal electric cooling, can also be used for heating)
regenerate the PCM’s heating capacity, using lower priced night electricity and shaving off peak
daytime demand.
As such, the façade is able to function using nothing but electricity, which could be generated using
photovoltaic panels at the bottom part of the façade. Even though energetically and exergetically the
use of electricity for resistive heating might not be the optimal solution, it simplifies both the design
and the connections of the façade to the building to a great extent.
Simulation and operation
To obtain an indication of how the façade performs, it is simulated using the Mathworks programme
Simulink [2]. It should be noted that the performance of the façade is attached to an office room that
is 5.4 m deep and is surrounded by other rooms, i.e. the only side that exchanges thermal energy with
the outdoor climate is the façade and is simulated with the Dutch climate in mind, using the weather
file for 1995, which had a very warm summer.
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