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Sunlight in the tank

How agile development methods help to overcome fears concerning the range of electric cars

EDAG experts develop solar powered range extender using scrum philosophy

Solar cells on roofs have become a common sight. The sunlight absorbed is converted into electrical power, and is thus able to supply an entire house with electricity. The advantages of this form of renewable energy are obvious – no annoying price fluctuations imposed by electricity suppliers, lower CO2 emissions and the sun is an inexhaustible resource. So why not also use the marvelous power of this heat and light emitting heavenly body for our cars?

Experts from EDAG and the Chinese corporate group "Hanergy" put their heads together to address this issue. The Far Eastern corporate group has been working with renewable energy since 1994. Pioneers in the field of thin-film solar cells, the Beijing-based group were last year looking for a partner in the automotive industry to combine outstanding design with a high level of engineering expertise. Their aim was to construct an electrically powered show car that would have a solar cell area of at least 6 square metres and a unique, futuristic and iconic character. In EDAG, Hanergy found what they were looking for.

Learning from software development

Volker Amelung, overall project manager, reports on the beginnings of the "Hanergy Solar Demonstrator" show car: "First of all, we had to convince Hanergy of our concept. As this was an absolutely innovative subject, it was quite clear to us that we would not be able to fall back on the classic waterfall model for project management. What we had to do was look at things from a different angle. We therefore had a look in the agile software developers' tool box, and decided to use their scrum method. A key aspect of scrum is that a project is not sequentially planned from A to Z. We therefore decided to start with a "story" on the show car, after which we divided the project into 12 "sprints". Working on one sprint after another, the product specifications were then sharpened and the show car developed."

Hanergy - the sun is an inexhaustible resource

Implementation was effected all around the world, with work on vehicle design, exterior styling and the solar cell assemblies being carried out in Fulda, interior styling and the drive concept in Gaimersheim, engine and chassis calibration at a test centre in Boxberg, and the headlights in Wolfsburg. The design and final assembly were undertaken in China, with the active support of the local EDAG office. "We clearly benefitted from our extensive and diversified expertise when it came to the 'Hanergy Solar Demonstrator' project," explains Volker Amelung. "With the support of our technical departments, for instance lighting technology, body manufacturing, but also Feynsinn, an EDAG Group brand specialising in user interface design and virtual reality, we were able to create the show car in just one year - from the initial idea to completion."

Refuel while you drive - only possible with solar power

The chief attraction of the Hanergy Solar Demonstrator is that the collectors can absorb sunlight and recharge the battery while the car is in motion. This increases the range while driving, so is in effect an integrated range extender. With up to 7 square metres of flexible gallium arsenide solar cells, the car has a very high performance grade: up to 1.5 kW under standard test conditions of 1000 W/m² and an outside temperature of 25°C. This can mean an additional range of up to 50 km if the battery is fully charged when you set off. Thanks to a high-efficiency converter developed by EDAG, the incident solar energy is effectively raised to the battery's high voltage level. This means that the battery can always be charged, regardless of whether the car is stationary or in motion.

Hanergy – solar driven vehicle

There are a number of reasons why this was such a special project for Amelung: "First of all, we had a fantastic team! Despite the pressure and stress that are always in the air when a show car is being developed and built, we had a lot of fun. And of course we couldn't wait to see the finished automobile at the end of our work. That was a great source of motivation."

The Hanergy Solar Demonstrator will be going on tour in China in the next few months, where it is expected to take various test sites by storm. As a tribute to renewable energy, the EDAG Hanergy Solar Demonstrator demonstrates how much of the potential of e-mobility still remains untapped.

A remarkable project, and one in which thinking outside the box really paid off. With the "Hanergy Solar Demonstrator", EDAG has proved that agile project management methods can be used not only for software development, but also for vehicle engineering.