How high is de wind pressure on a Heliostat?

In order to design a heliostat we have to understand the forces that will act on the structure. During a storm it’s more than likely cloudy so the heliostat only has to work in low wind-speeds. Wind-speeds in m/s x 3.6 gives the wind-speed in km/h, 20m/s = 72 km/h. which gives a pressure of 0.5 X 1.25 x 20² = 250 N/m².

Wind speed (m/s) Wind pressure (N/m2)
Lower limit Upper limit Upper limit
0 0.2 0.03
0.3 1.5 1.4
1.6 3.3 6.8
3.4 5.4 18
5.5 7.9 39
8 10.7 72
10.8 13.8 119
13.9 17.1 183
17.2 20.7 268
20.8 24.4 372
24.5 28.4 504
28.5 32.5 660
32.6 > 660
The wind pressure can be approximated by: Pressure = ½ x (density of air) x (wind speed)² x (shape factor)

  • The density of air is about 1.25 kg/m³.
  • The shape factor (drag coefficient) depends on the shape of the body. It has order of magnitude 1 and is dimension less.
  • The wind speed must be expressed in m/s. In that case the pressure has units kg/m/s², i.e. N/m².

Probably the most important environmental design criterion that must be met by a heliostat design is the wind condition. Typical requirements may be for the heliostat to meet its operating requirements in a 12 m/s wind, to survive a 22 m/s wind, and to continue to operate or move to the stow position in a 40 m/s wind (a position usually horizontal with mirrors face-up or face-down). Also, the ability to survive hail is important for any flat surface exposed to the elements. A typical hail survival criterion is 19 mm diameter hailstones impinging at 20 m/s. source: the power of the sun

One of the ten little test mirros 30×30 cm


About Egidius Kuhlmann

Reading about peak-oil, overpopulation, “Terra Preta” and biochar in 2009 and after making batches biochar for soil improvement from garden residue, I thought, why not make biochar from corpses. Deeply worried about the unsustainable path 'we' as humanity have taken, I see a future where fossil fuels are scarce, the western economic growth model in tatters, the global temperature rises due to the CO2 concentration in the atmosphere with an growing population reaching billions more humans than is sustainable? Thinking along those paths, the question “how can we dispose so efficiently and with the least amount of energy of human remains” became the starting point.
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