The start-up WIND my ROOF has developed an innovative wind turbine for roofs which, combined with two solar panels, can produce electricity in both winter and summer.
Imagined by two students from the Ecole des Ponts ParisTech, the WindBox – a module combining wind and solar electricity production – developed by the company WIND my ROOF is designed to be installed on the edge of flat roofs of buildings, and can produce electricity, either wind or solar, or both at the same time, when conditions permit.
Juliette Fournand, COO of WIND my ROOF, explained to Techniques de l’Ingénieur the genesis of the project and its development, from R&D to marketing, since the creation of the company in 2018.
Engineering Techniques: Tell us how the concept of a box mixing solar and wind technologies was born, today marketed by WIND my ROOF.
Juliette Fournand : WIND my ROOF is basically a project imagined by two students from the Ponts ParisTech school in 2016, based on a technical problem: how produce electricity on the roofs? They have, for this purpose developed a wind turbine functional and suitable for flat roofs of buildings, which won an innovation prize during a competition organized by Vinci Energies; with a year of incubation in the incubator set up by Vinci Energies, Leonard. It was from there that these two students, Antoine Brichot and Yanis Maacha, really launched into entrepreneurship.
Three years of research and development followed, with the problem of producing electricity from wind.
What are the key factors taken into consideration to develop the wind part of the WindBox?
The first factor to consider is the location on the roof and the drainage. vents. If we consider a classic, rectangular building, the winds rise along the facades, accelerating, then become turbulences which cannot be exploited by any type of wind turbine. Previously, the systems put in place to avoid this turbulence consisted of wind turbines placed in the middle of the roofs, high up to avoid turbulence, but these systems are not viable. Indeed, in this case, the wind turbine support pylon finds itself in turbulence, and the supports and ballasts to be put in place to reinforce the structure are too important. And the risks of tearing are too great.
The creators of WIND my ROOF opted for the placement of wind turbines at the edge of the roof, to exploit the winds which accelerate along the facade, before they become turbulence. This is what we call corner flow: the winds are stronger at the edge than on other areas of the roof, without being too high to be exploited.
And the second factor?
The tool we have put in place does not look at all like a classic wind turbine. The tests that were carried out pushed us to develop a vertical wind turbine model, but which is arranged horizontally, like a water turbine. This makes it possible to have four fixing points on the roof of the building, and to avoid pendulum effects and tearing phenomena due to winds.
During the R&D phase, we were incubated within Green Tech Innovation, in the premises of the École des Ponts, and we were able to carry out wind tunnel tests, tests in real conditions, in particular on a building located on the square of the La Défense esplanade. We also carried out tests at the CSTB wind tunnel in Nantes, with winds of 180 km/h, which validated the possibility of installing our modules throughout continental France without risks.
We were finally able to successfully validate our power curves, namely the power produced as a function of the wind force.
Where are you in terms of marketing?
It started two years ago. We systematically start with a study phase, in which we are supported by an EDF R&D laboratory, askedwhich allows us to use Code-Saturne, a tool for simulating airflow at the scale of a neighborhood, to assess the impact of the architecture of the neighborhood in question on the acceleration or deceleration of winds. This provides us with the information needed to be able to find the locations where it would make the most sense to place the WindBoxes. This is the first phase of marketing, necessary before moving on to marketing the product as such.
A year ago, we set up our first pilot project on the roof of a building in Rouen, with the current version of the WindBox, and last month, we carried out an installation for the SICAE de la Somme et du Cambresis, an electricity network manager, during a project (Chapters) supported by the FEDER and the Hauts-de-France region where various innovative technological bricks in terms of energy are being tested, including ours.
We have other projects in progress in the South of France, Belgium, Luxembourg and Germany.
The basic technology of WindBoxes is the wind turbine. Why did you add solar panels to the device?
This is a technically simple idea to implement. Two solar panels are attached to the WindBox, and this allows two things: firstly, the maximization of the energy produced in the same space, by adding very little weight on the roof. This is important because roofs are not designed to support too much weight. Also, it turns out that the roof edges are the strongest parts of the roof, so this is really where it is relevant to add energy production modules without weakening the structure.
The second reason is the seasonality of solar and wind energy sources, which is very often the opposite in France. This wind/solar mix therefore ensures stable electricity production throughout the year.
Depending on the analysis we do on a geographic site, we will recommend either solar power, wind power, or both. Everything will depend on the situation of the site and the results of the analysis that will be carried out, the objective remaining to implement the most efficient solution possible in terms of energy production.
Can WindBoxes be installed on several edges of the same roof?
Wind flows, which change depending on the geographic area, potentially make it feasible to install WindBoxes on two sides of a building’s roof. In most cases, however, we exploit the majority wind corridor.
How competitive are you today in terms of price per kWh?
Today we are more expensive in terms of production costs. We are between 20 and 25 cents per kWh for the WindBox in France, which is higher than the average for rooftop solar technologies on French territory, which is around 13 cents per kWh. We are therefore above, but our objective is to align with these prices and follow their decline subsequently, thanks to the industrialization and the R and D that we are pursuing.
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