With the imminent application of the European Directives 2010/31/EU and 2012/27/EU on energy efficiency of buildings, from the end of 2020, all new homes and new offices will be required to be virtually self-sufficient in terms of energy. The deadline has been brought forward to the end of 2018 for all new public buildings. And Italy too will also play its part, and has already implemented the EU guidelines by including them in the country’s Energy Efficiency Action Plan announced in July 2014.
New homes, new offices and new industrial buildings will be built to consume as little energy as possible and will have to produce the energy they consume directly. This will be achieved essentially by eliminating the heat loss from walls and making all forms of domestic consumption more efficient, from air conditioning and heating to all household appliances. But the most important factor in this small domestic revolution will be to equip every building for the production of energy from renewable sources. The problem is solved easily in detached buildings, small houses and buildings by installing a sufficient number of traditional silicon-based solar panels on south-facing roofs; they need to be installed on supports that allow the panels to be oriented towards the south and with the right inclination.
However, the problem is not so straightforward for larger buildings. In fact, the potential production of electricity is proportional to the number of solar panels installed on the roof; therefore it is directly proportional to the available surface roof space. But the energy consumption of a building is proportional to the number of people who live or work there; i.e. in relation to the entire volume of living space available under a single roof. In other words, in single-family homes or even terraced houses, an increase in the number of families that live there corresponds to an increase in the roof surface; so the number of solar panels available for each unit remains constant. But if we consider multi-storey buildings, it is clear that the number of inhabitants – and therefore consumption – will increase with the number of floors, while the available roof will remain the same. Consequently, it can be calculated that for a building with more than three or four floors, solar panels placed on the roof will not be sufficient to produce enough electricity for all people who live or work in that building.
But the problem can be solved. Indeed, it must be resolved, and soon, given the time available before new the regulations come into force. The Eni Research Centre for Renewable Energy and the Environment has developed, tested and developed two technologies that can provide a solution (Two? Actually, Three, Continue Reading) to this problem. We have already talked about organic solar cells, called Organic PhotoVoltaics (OPV), which are thin and flexible solar cells made up of special inks printed on a range of different supports. Among the benefits of these silicon-free cells is extreme versatility. Indeed, there is no need to install them on trellises mounted on roofs, as they can be printed directly onto roof tiles, bricks, wall tiles and directly into many of the constituent parts of a building. Unlike silicon panels, OPVs also work in diffused light conditions: i.e. at dawn, at sunset, when it is cloudy or there is fog. This is why they do not need to be positioned facing south or at a precise angle, but can be installed on all surfaces of the building, including vertical walls.
Another technological innovation developed at the Eni Research Centre for Renewable Energy and the Environment is the luminescent solar concentrator. Luminescent Solar Concentrators (LSC), that we have also mentioned, are special transparent and coloured windows that can produce energy and adjust the brightness and temperature of the environment in which they are mounted. This not only generates electricity but can save on heating and air conditioning costs.
One solution, two technologies
On a building, in addition to the silicon-based solar panels fitted on a south-facing roof, a combination of these two technologies can be installed, i.e. OPVs on walls and on all opaque surfaces and LSCs in windows, skylights and all transparent surfaces. In both cases, you can use all the exposed walls on all cardinal points to place OPV cells, while the windows on all sides can be equipped with LSC technology. The combination of these and other technologies applied not to the buildings but directly to the structural elements of the buildings is a possible application of Building Integrated PhotoVoltaics (or BIPV).
But what happens at night? Well, when it is dark the new OPVs and LSC windows will not produce energy, but to achieve energy self-sufficiency in every building, you can always have an exchange contract with the company that manages the electricity grid and buy energy when such devices do not produce enough and sell it when they produce more than we consume. But if this is not economically viable, or if the house is isolated and is a long way from the electricity grid, then systems for storing electricity will become decisive. Eni is also working on this. We have also already written mentioned that Eni Research Centre for Renewable Energy and the Environment is developing new flow batteries with virtually no energy loss and with capacity and power that can be regulated at will. Finally, the new European regulations pose a great challenge in research into new ways of producing renewable energy, but they will also be decisive in driving the development of the next-generation photovoltaic technologies.