Stroom is a strategic concept vehicle that I developed for the Nuon Solar Team (based in Delft). Stroom is a solar-powered car with a revolutionary 1-2-1 passenger packaging design, which minimizes the aerodynamic drag.
The slightly overhanging roof offers 2m² of solar cells. In dutch climate, these cells can power the car for 20-80 kilometres daily (depending on the time of the year).
Stroom has three modes of use. 'Transport', in which all seats are folded down so you can do lots of groceries. 'Everyday', in which the backseat is folded down to use as a luggage compartment. And 'Taxi', in which every seat is in its upright position and the Stroom can carry four people.
Current solar cars are mostly flat shaped racing vehicles. They are uncomfortable and impractical. I started out by selecting a target group for my new solar car: owners of a second car. Research by the Brittish Automobile Association (2015) has shown that 2.5 out of 8 million second cars in the UK could be replaced by an electric car with limited range. So why not a solar car?
During my research, I've asked twenty-five second car owners about how they use their second car. I found out that most of them didn't drive more than 25 kilometres a day in their second car, and used it for shopping and picking up people (for instance their children).
The challenge of making a good solar car, I figured, is in the packaging of the functional components.
For a traditional (second) car, the packaging is pretty straightforward: the engine goes in the front, and there are two rows of seats with some luggage space in the back. For a solar car, very different aspects important. Power is limited, so the body has to be extremely aerodynamic. Also, a solar car has to provide as much space as possible for photovoltaic cells. On top of that, I wanted my solar car to be tailored for use as a second car.
With this in mind, I set out to create the perfect arrangement of components for my solar vehicle. I did this by cutting all necessary components - seats, luggage, wheels - on a scale 1:10.
Packaging of the practical solar car
Using the 'fish trap'-model, I found three different interesting design directions, which are illustrated below. After a selection process, I chose to develop the packaging of concept 'Veer' into final concept 'Stroom.'
Wind is the smallest concept vehicle. It chooses aerodynamics and low weight over space for solar cells. Wind has a bench seat suitable for 1.5 people at the front. Wind has a folding backseat, which is 80 centimetres in width, just like the front seat. The luggage space in Wind is above the rear wheels. It is accessible by a small door on the side of the car.
Veer is designed with a 1-2-1 person packaging. The driver's seat is between the front wheels, there is a folding 1.5 seater bench in the middle. In the back, there is a single backseat between the rear wheels. With both seat rows folded down, Veer can transport things up to 2 [m] in length. In a top view, Veer has a teardrop shape. It has a roof with solar cells that is slightly overhanging. Veer combines aerodynamics with flexibility in use.
Fier was designed using the 'classic' car packaging: two seats in the front and a back seat for two persons. This folding seat is 80 [cm] in width, making it suitable for one adult and a child. Fier has room for luggage in the front and in the back. Fier chooses safety and a lot of solar panels above optimal aerodynamics.
Aerodynamic flow analysis
Using 'Flow design' by Autodesk, I performed aerodynamic analysis on my concept, to be able to do calculations on the range of my electric car. I've modelled a current second car, a VW Up! as well as my 'Stroom' concept vehicle. There was significantly less aerodynamic drag in Stroom (Cw = 0.28), while it has more rooftop space for solar cells than the Up!.
Now that I'd created a solar car for use as a second car that consumers wanted (7/10 current second car owners would want to own such a car), I decided it was time to optimize its performance for racing purposes. After all, my cliënt (Nuon Solar Team) would like to win a future cruiser class race.
Adaptations in the Stroom S model include more solar cells, a slightly more overhanging roof, a carbon reinforced body, six times as much battery power (during the race you are allowed a full charge at some points) and better aerodynamics through a more rounded 'nose'.
To be able to 'feel' the curves of the design, and to be able to communicate the form of the concept vehicle, I've built a prototype of Stroom on a scale 1:10 using a CNC milling technique, some spray paint and glue.