Building’s Facilities for Nearly Zero Energy Consumption
by Francesco Paolo Lamacchia President of the first Italian Network of Zero-Energy Buildings and Giuseppe Perfetto Vice-President of the first Italian Network of Zero-Energy Buildings
The EU’s 2030 climate and energy framework sets three key targets for the year 2030: at least 40% cuts in greenhouse gas emissions (from 1990 levels); at least 27% share for renewable energy; and at least 27% improvement in energy efficiency. To achieve the at least 40% target, EU emissions trading system (ETS) sectors would have to cut emissions by 43%(compared to 2005) – to this end, the ETS is to be reformed and strengthened; non-ETS sectors would need to cut emissions by 30% (compared to 2005) – this needs to be translated into individual binding targets for Member States. On the basis of the Energy Efficiency Directive, the European Council has endorsed an indicative energy savings target of 27% by 2030. This target will be reviewed in 2020 having in mind a 30% target. The key sector to respect this framework is the buildings industry. The leverage to have low emissions buildings is the introduction of new technologies to define and select facilities in the building and to integrate them in its own bearing structure. The types of buildings that Europe asks for in the coming years are the nZEB buildings. The fundamental rule to build nZEBs is to maximize the exploitation of all the building envelope surfaces to make them energy-efficient through the leading photovoltaic technology. Opaque or transparent photovoltaic systems are, from now on, an integral part of the definition of a building, as it has been for the “brick” for millennia, especially in the western countries. This is the change of paradigm that every architect and builder will have to follow in the immediate future. If, in recent times, photovoltaic systems have spread widely on opaque surfaces with the juxtaposition of panels, today it is possible to make transparent surfaces able to guarantee, not only natural insulation and lighting, but also electricity production at the service of the household. Glass to Power’s transparent photovoltaic window is a virtuous example for achieving such results, especially in typical architectures of glazed façades or office buildings, as well as school buildings, where the need for lighting and therefore the extension of transparent surfaces is outstanding. Architects will have to leverage on a cost-benefit analysis of energy refurbishment to test and demonstrate the feasibility of the intervention and the economic return of the investment. In addition, among the plant systems that can be provided with the Zero Consumption Building, it is worth to point out the so-called thermo-photovoltaic system, that is the cogeneration of electricity and heat from solar power with a single device. This is because heating and domestic hot water are among the essential needs for a household. This device is a perfect symbiosis between electrical and thermal performance, which allows to save on installation time and area occupied. In general, therefore, we can consider it very valid for its high efficiency and technological innovation features both for new constructions and for retrofitting on existing buildings and especially for those with a limited usable area available. The device is a classic photovoltaic module of the standard type, that is with a glass/tedlar rear panel and aluminum frame, to which a roll bond is combined usually made of aluminum, copper or steel with ½ “ hydraulic connections. The device is then sized for the production of electricity in a conventional way through irradiation data by location, azimuth and tilt of the usable surface, while for the thermal aspect it can reach an efficiency of at least 50%. The production technology of thermo-photovoltaic modules consists in the process of installing a copper/aluminum /plastic thermal collector on the backsheet surface of the PV module (usually made of teflon) through a specific interposition layer that allows electrical insulation between the two components and the best thermal exchange efficiency, also allowing, during solar irradiation, the different thermal expansion of the components that make up the PVT Module. From a thermal point of view, the cogeneration of the same PV module (through thermal conduction) allows a rated thermal output generally higher than 45% (in the case of copper collectors generally higher than 55%). This results in a component that has a total efficiency of over 70%, making it very attractive in terms of costs and area occupied. Considering that the building has a considerable extension in terms of vertical surfaces, belonging to its envelope, but also to ancillary parts such as balconies and terraces, the possibility of integration is largely feasible especially in the Mediterranean countries, and not only, with high solar productivity.