The cooling demand is mostly concentrated in the period from June to October. We will therefore focus to the next simulations on this period.

The ventilation rate between the adjacent zones is set to10 ac/h.

Additional natural ventilation is set as follows:

We obtain a cooling demand with natural ventilation equal to -1465.7 kWh.

In other words, by applying natural ventilation we reduce the cooling load by 25.4%.

Simulation 3: Use of shading (25% decrease in the size of the south-facing window) to reduce cooling load

We apply a 25% decrease in the size of the window that faces south to simulate shading in additional to the usage of natural ventilation.

The window area is now 5.63m2 instead of 7.5m2.

As a result the cooling demand decreases to -1281.7kWh, which is equivalent to a further reduction of 12.6% as compared with only natural ventilation.

Note that the passive solar gains (period from June to October) have been changed to 2596.3kWh instead of 3025.4kWh, or a reduction of 14.1%.

Simulation 4: Further shading increase (50% decrease in the size of the south-facing window)

The window area has been modified now to 3.75m2.

The outcome is that the cooling demand is reduced to -1053kWh, meaning we have obtained a decrease of 27.7% on the cooling demand as compared with using only natural ventilation. Compared to the previous simulation using 25% reduction in the south-facing window, the cooling demand has dropped by 17.9%.

Note that the passive solar gains have been reduced to 2161.7 kWh for the period, or a reduction of 28.5% as compared with the initial value.

We have increased significantly the thickness and specific heat of the structure. Our purpose was to create a shell structure capable of absorbing large amounts of heat during the summer day period.

The wall U-Value has been altered from 0.122 W/m2K to 0.164 W/m2K and concrete total volume has been increased by 23.55 m3. This would mean an added thermal mass value of 56.52 tn (density d=2.4tn/m3).

This heat is then dissipated to the ambient during the night through natural ventilation. In addition a white coloured coating has been chosen for the exterior side of the wall in order to reduce the solar radiation absorbed by the structure during the day.

Simulations have been run for a basic natural ventilation regarding air quality comfort level, natural night ventilation, 25% window size reduction and 50% window size reduction. The cooling demands for the above scenarios are the following:

This is in addition to the previously applied natural ventilation and shading (simulation 4) in order to eliminate the cooling demand in Palermo.

We will simulate the use of our earth to air heat exchanger only during July, August and September since our heat exchanger has a noticeable energy consumption of about 300 kWh per hour during operation time.

The ground temperature is estimated below:

The cooling demand is now reduced from -1053kWh (using natural ventilation and 50% reduction in the window size) down to -550.5kWh, meaning a 47.7% decrease.

Scenario B: The ground duct ventilation is applied from 6h-24h

Our ground heat exchanger now functions all day except for 0am - 6am.

The cooling demand is now diminished by 65% down to -191.3kWh.

Scenario C: The ground duct ventilation is applied for 24h

This allows to a further reduction in the cooling demand from -191.3kWh to only -0.5kWh.

We therefore manage to eliminate the cooling demand in Palermo.

Conclusion:

The results upon the cooling demand reduction in Palermo are demonstrated in the following graph: