The Cistercian monastery in step with the times: energy upgrading of 1500 square meters without solar panels
Certosa di Pavia
The client's need was to redevelop the previous heating-cooling plant with diesel boiler (average seasonal yield 86%) and refrigeration unit (average seasonal coefficient EER = 2.3), respecting the architectural constraints on state property and using renewable energy.
The Robur solution chosen - reversible methane air source heat pumps with integrated condensing boilers - compared to the previous central heating plant, guarantees annually:
- 130% average winter seasonal efficiency;
- 31% economic savings;
- 27 kW of reduction in electricity consumption;
- 44,938 kWh of renewable aerothermal energy used;
- saving of 2 tons of oil equivalent;
- reduction of the emission of 13.6 tons of CO2.
The Robur solution also avoided the installation of solar systems (D.G.R. Lombardia n.8 / 8745 - Art.6.5).
The area subject to redevelopment consists of an area of 1440 square meters. The thermal power required for the heating service is 117 kW, the cooling power for summer air conditioning is 70 kW and that for the production of domestic hot water is 35 kW, with an accumulation volume of 800 liters.
For the thermal and cooling energy generation system, a system with heat pumps was thought of during the design phase, given the possibility offered by a regional law of being able to avoid installing otherwise mandatory solar systems.
This decision made it possible to reduce the construction costs of the systems and to obviate the architectural complexities typical of the installation of solar panels on the roof.
In the specific case, a solution was sought that would allow the use of high-temperature terminals and respect the Lombard DGR, obtaining an efficient system capable of using renewable energy and keeping construction costs sustainable.
The solution to the problem was found in the technology of reversible absorption heat pumps running on natural gas + Robur renewable aerothermal energy.
The generation system with four reversible natural gas absorption heat pumps + renewable energy GAHP-AR provides all the thermal power necessary for the heating system and the cooling power for the air conditioning system.
The heat pumps are flanked by an outdoor condensing boiler for domestic hot water. The regulation of the system is obtained through the electronics supplied as standard, which manages the primary circuit by modulating the power supplied and the flow rate of the heat transfer fluid and cascading the individual heat pumps. In winter, the digital control panel allows you to manage the delivery temperature of the heat transfer fluid following a climatic curve.
The heat pumps installed, operating at a medium-high temperature (60 ° C maximum) of the heat transfer fluid, have an average seasonal winter efficiency of approximately 130%.
- The amount of renewable energy used by the plant is equal to 44,938 kWh / year, despite the harsh winter temperatures of the Lombard plain and the high temperatures necessary for users to maintain comfort in the building.
- For the summer service it was possible to reduce the electrical use of the structure by 27 kW, avoiding the need for a double meter for managing the heat pumps.
- The above data thus allowed economic savings in the annual energy management of the system equal to 31% less than in the previous situation with a central heating system with oil boiler and a traditional refrigeration unit.