The main challenge regarding an architectural intervention on Poveglia is definitely its remoteness to the mainland. It requires additional efforts compared to conventional settings. Such efforts include first of all infrastructural measures to connect the island to water and electricity supply, sewage and IT systems besides the transport of construction material by boat and the necessity for extra strong piled foundations. It is of high importance to consider strategies that ensure a certain degree of self-sufficiency. In this way, initial high investment can be amortised by low expenditures during the life-cycle of the project. Our major concern is the energetical matter which constitutes one of the most important factors. We set high standard for all buildings to attain excellent performance.
Self-sufficiency does not imply, however, that the island should stand on its own. Quite the contrary; it should be connected as much as possible so that the island can provide benefits far beyond its own boundaries. To utilise the full potential of the island it is necessary to feed the grid with the energy surpluses especially during summer. In this way Poveglia becomes a productive part of the lagoon and can be role model for other islands that enter into the grid in the future. The decentralisation of the energy production is commonly referred to as ‘smart grid’. This term highlights the manifold positive implications of having variety of operational and energy measures including smart meters, smart appliances and renewable energy sources. The direct benefits are among others the quicker restoration of electricity after power disturbances, the reduced operations and management costs for utilities, and ultimately lower power costs for consumers.1
The general approach to the energy concept can be divided in two main parts:
(1) the reduction of the demand side by high performance of components and
(2) the onsite generation of energy from renewable sources. For the first we designed the buildings to meet good volume-surface ratios and low energy trasmittance, for the second we implemented a groundwater heatpump system. This system uses the temperature difference between earth (highly saturated with water) and the liquid in the heating/cooling system. To cover the energy demand during most of the year photovoltaic panels have been installed on the roofs of the Tent type which features the biggest available flat surface.
Poveglia’s energy model provides us with an overall picture of results from different aspects: heating and cooling simulations of each building (both in real and fractional values), calculations of energy needed for electricity, equipments and Domestic Hot Water (DHW) and predictions of energy supply by photo-voltaic systems.
The visualised data highlights three main observations:
1. in general the project has a low value of energy demand (47 kWh/year x m2) which in many EU building codes fulfills high performance criteria;
2. the energy demand of heating is much higher than the cooling;
3. annually speaking the energy supply on-site by renewable sources (1.8 Mio. kWh/year) is greater than the energy demand (0.65 Mio. kWh/year).
The positive result from the first observation shows the competitiveness of Poveglia project, especially considering that we are dealing with preservation. The project benefits from climate conditions and high performance buildings. Venice lies in Mediterranean climate zone which implies relatively dry summers and mild winters. Well-designed building envelopes and well-sought materials result in low thermal transmittance. The absolute energy needed for heating or cooling is consequently low (between 11kWh/ year x m2 and 32kWh/ year x m2). Additional measures help to improve the energy performance. The campus is closed during the hottest month (August) and is optimised with usage schedules (as low occupancy would be detected/predicted the facility manager closes some of the rooms). The second observation has surely many causes. Regarding the Cave and Hut types (see Fig. 76/77) the percentage of heating energy has a much bigger share in the overall energy demand. This can be traced back to high opacity in the case of Hut (given by the auditorium function). In the case of Cave the existing building works as a second skin and reduces solar heat gain.