Hydronic System - Multifunction
Requalification of thermal and frigorific plant
to save energy and respect the environment
Built between 1748 and 1772 by the architect Giorgio Massari, Palazzo Grassi is the latest noble residence built in Canal Grande before the end of the Venice Republic.
The building has three floors and a surface of around 5.000 m². Thanks to the energetic refurbishment intervention and the use of three Clivet multifunction units; the annual energy saving is of 604.800 kWh (almost 30% of the bill).
The requalification of thermal and frigorific plant of Palazzo Grassi, made in 2016, has represented a big challenge for several reasons: the short execution time, the very narrow technical room and the lagoon water used as a thermal exchange source for Clivet heat pumps to produce hot and refrigerated water, even simultaneously thanks to the recovery operation.
The lagoon water, directly available because the building is built on the Venetian lagoon, needs to be filtered and treated to eliminate the impurities and avoid working problems to the units and components. The old thermal plant was dismantled in order to leave space to the new heat pumps, inertia tanks, filters, exchangers, pumps and pipes.
The air conditioning system
Double basket devices filter the lagoon water and another filter, internally covered by rubber, makes the second filtration step (grade 2,5 mm) before the water goes through the last auto cleaning filter that assures a filtration grade equal to 250 μm. Than the lagoon, water leaves or takes heat, depending on the operation mode, to the glycolic circuit, through titanium heat exchangers.
The heart of the plant are three Clivet multifunction units (WSHN-XEE2 MF 100.2 4T GEO) working with the glycolic fluid as source for heating and/or cooling the air conditioning plant circuits of Palazzo Grassi, with the relative distribution.
The plant is competed by two storage tanks (cold and warm) necessary for a correct unit management, avoiding continuous starting cycles and deterioration, by a treating and softening water system and by electronic pumps for hot and cold fluid supply to the distribution system.
- Heating: 283 kW/each - Total 849 kW (40/45°C and 3/0°C)
- Cooling: 315 kW/each - Total 945 kW (12/7°C and 30/35°C)
Conditions in recovery operation:
- Cooling: 267 kW/each - Total 801 kW (12/7°C and 40/45°C)
- Heating: 347 kW/each - Total 1.041 kW (12/7°C and 40/45°C).
The solution assures a high energetic efficiency thanks to the thermal exchange with lagoon water: the COP and EER of the heat pumps are higher and more favorable than those of similar air-cooled units. The advantage of the recovery operation optimizes the efficiency with values higher than 7.6.
The units positioning was studied and designed to adapt to the small space of the technological plant.
Clivet units are managed by a supervision system that controls the temperature of the supply water, the serial or alternative starts of the units and the filter dirtying level in order to calculate a proper maintenance.
The heat pumps allow the exploitation of the renewable energy contained in the lagoon water and represent a solution with no local pollutant emissions, allowing to reduce the environment impact.
In this way, the prestigious Palazzo Grassi has been requalified not only as far as energy is concerned, but also under and ecological point of view.
The comparison has been done using the electrical energy bills of the years 2015 (old plant) and 2017.
The electrical energy annual saving is of 604.800 kWh, almost 30% of the bill (exactly 28,5%). The annual consumption has changed from 2.122.400 kWh/year to a 1.517.600 kWh/year.
Invesotr: Palazzo Grassi, Venice
Plant designer: NT ENGINEERING srl, Guanzate (CO) – Tarcisio Guffanti
Plant installer: SIRAM SpA