SUN TRIP 2020 : TRACE AND SOLAR DNI


By Christophe Bayard – Sun Trip Technical manager.


Each participant in the Sun Trip wondered about the journey. The best, the shortest, the easiest, the least uneven, the most interesting, etc. Obviously, all the answers are good for this question since everyone has different motivations and interests.I propose here to explore only 4 objective criteria on this course:

No go zones
Distance
Total elevation gain
Probable solar radiation (Direct Normal Irradiation or DNI)


1. The adventurers have an obligation to avoid areas identified by the organization as too risky (or complex) in an event like the Sun Trip.

2. The minimum distance between Albertville (proper start point) and Guangzhou is about 9400 km “as the crow flies”. This distance is what is called an orthodrom( or great circle route): the shortest distance on the spherical terrestrial surface. Of course, this exact route is difficult or impossible to follow by staying on passable roads. It may, however, be interesting to look for a route approaching this shortest route.

3. The second interesting criteria to take into account is the elevation gain. It may sometimes be wise to prefer to take a few detours rather than crossing mountains. For example, when leaving France, the great circle crosses the Alps, which is certainly not the most energy efficient route. We might prefer to go a little further north to avoid the Alps. As an example, between Albertville and the north of Vienna (Austria) the difference in height on the nearest route of the great circle is about 10000 m for 1100 km distance while a road avoiding the Alps accumulates about 4500 m of altitude gain for 1200 km. It is expensive paid for a gain of only 10% on the mileage.

4. The last criteria to look at would be the potential of sun that we can hope for on the road. This criteria is a little more random because it is only sunlight statistics that can be very different from the sunshine actually encountered. Here is a map where the DNI is the amount of sun received on average by a surface always well oriented in the sun. The great circle is superimposed on the map for information. Red areas are the most exposed areas and blue are the least exposed areas.

If the solar radiation on European part is often linked to the weather conditions, this map shows two very clear trends for the Asian part:

1. The Kazakh routes and then the one across the Tibetan plateau, in China, should be able to benefit from a very good solar radiation, even if the snow can also be at there on the highest points of the course!

2. But once arrived in the plains of East China, beyond Chengdu, adventurers will face a much less favorable solar radiation, especially because they will arrive just after the monsoon season ! It will be necessary to push hard there…


Here is now in several maps a route suggestion offering the best compromise between the 3 criteria. (The first part is previous page). The length of this course is about 12700km. To your maps and good reflections.

Czech Republic / Poland / Ukraine:

Ukraina / Russia :

Russia / Kazakhstan :

China (checkpoint and final part) :

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