Ca l’Alier demonstrated the feasibility of a Nearly Zero Site Energy Use through a combination of photovoltaic power (85kWp), a connection to the district heating and cooling (DHC) network that recovers heat from urban solid waste treatment plant, and the installation of an energy management system that is capable of optimising consumption as well as forecasting the building load.
The existing DHC network in 22@District, DISTRICLIMA, satisfies the heating and cooling demands of the building while the building’s rooftop is equipped with a photovoltaic installation.The conventional grid connection is carried out in three-phases, with the inverters feeding each phase. An energy meter is installed at the entrance of the photovoltaic system in order to deduct any energy generated which could be consumed by the conventional grid.
At the design stage, installed power for cooling and heating is planned at 202kW and 126kW, respectively. The distribution network for heating & cooling is installed beneath the street adjacent to the building. A room in the building’s basement enables the system to be connected to the primary circuit of the Districlima network. This room includes the building-owned substations and the secondary circuit. The installation is composed of four pipes and the pumps will be able to perform at variable flowrates.
The local utility Districlima has a DHC network in Barcelona with a total cooling capacity of 31 MW and heating capacity of 20 MW. The vast majority of heat and cold production is based on the use of the steam produced from the incineration of municipal waste (MSW) in the nearby treatment plant TERSA.The remaining cooling production is carried out in electric chiller machines cooled by seawater. Consequently, high yields are reached and the installation of cooling towers is avoided (eliminating the risk of Legionnaires' disease). This water is collected from the nearby Port Fòrum and is returned to the sea through a manifold, with virtually no environmental impact.
The system is completed by a buffer tank of cold water of 5,000 m3 which stores cold overnight and disperses it throughout the day. Hot water is supplied at temperatures over 90ºC and returns at 60ºC, while cold water is supplied at a temperature between 4 and 5°C and returns at about 14°C.