Geothermal heat pumps in the Maltese Parliament in Valletta
Overview
The Valletta City Gate in Malta, is the so-called entrance to the country's capital. Due to destruction back in World War 2, the city gate was subject to reconstruction and reorganisation. Over a timespan of six years (2009-2015), the city gate itself and the close-by city walls were reconstructed, as well as an open-air theatre, designed by Renzo Piano, a new parliament building was built and landscaping of the ditch. In 2015, after several delays, the project has been completed. The 40,000 square meters are under UNESCO heritage protection and required a total investment of €82 million. Amongst the total budget, € 38,829,049 went into the Parliament Building, which is of particular interest to this article.
Indeed, the new parliament buildings, consisting of two blocks and a central courtyard, was designed with particular attention to energy and environmental implications of the construction and the building itself. Thanks to its new design, the building reaches high energy efficiency standards above the legal requirements. The stone facade heats up less and allows natural ventilation. In addition, irregularities on the façade create shadows, reducing the surface temperature. Thus, by combining passive design with the use of on-site renewable energy sources, the House of Parliament is a nearly zero-energy building.
The geothermal system
To generate its heating and cooling, the building relies on geothermal energy and photovoltaic panels. There are 40 geothermal boreholes with depths of 140 meters, 100 meters below sea-level. Together with the photovoltaic panels, the geothermal installation provides 80% of the required energy for heating in winter and 60% for cooling in summer. Additionally, thanks to the photovoltaic panels, the geothermal heat pump runs with renewable energy.
Concretely, the building's cooling system extracts heat from the building during summer and stores it in the geothermal wells below the building. Then, during winter, the heat is extracted again and provides the parliamentary building with heat. Therefore, the heating and cooling energy consumption has been reduced from almost 80 MWh/year to 50MWh/year, which is approximately 40% less than a traditional heating and cooling system.
Summary
Type of system: geothermal heat pumps combined with solar panels
Borehole depth: 140 meters (100 meters below sea level)
Number of boreholes: 40
Energy demand covered by the geothermal heat pump system: 100% of heating and 80% of cooling