The design of a TWIND technology wind power generator is based on the diameter of the aerostatic balloons. The dimensions of other components and the parameters that determine its output are derived by this factor.

An example of dimensions table is visible clicking the image on the left side; the following describes the process by which sail surfaces, connecting cables and lifting mass of the prototype are determined.

 

SAIL SURFACES

The radius of the parachutes utilized is tied to the diameter of the aerostatic balloons; the parachute fabric must not cover the balloon above its diameter in order not to create wind resistance during the module’s recovery phase.

Due to this consideration, the balloons used (6 meters in diameter) can be linked to a parachute of 9.4 metres in diameter with a surface equal to 70 square metres

During the design phase of the project, the implementation of spherical balloons was considered although oblong shaped balloons represent an interesting solution in terms of a better efficiency of the system due to a superior upward lift and a larger parachute surface

 

 

CABLE LENGHT

The aerostatic module works at an altitude determined by the length of the cable. This is determined by the lifting power of the aerostatic balloons used and by their dimensions.

Each of the two balloons of a diameter of 6 metres, can hold 113 cubic metres of helium for a total of 226 cubic metres which equal to an upward lift of 252 Kg to which 60 Kg of the shell weight of both balloons must be subtracted.

As we have seen before, a balloon of 6 metres in diameter allows the implementation of a parachute with a maximum diameter of 9.4 metres involves a total weight for both parachutes of about 32 Kg (considering an average weight of parachute fabric of 0.230 Kg per square metre) which reduces upward lift to 160 Kg.

The cable used for the ground connection is the Dyneema textile cable of a diameter of 21 mm with a maximum load of 42 tons and a weight equal to 0.25 Kg per metre. This limits cable length to 448 metres.

The design has opted for a cable 350 metres long and with a weight of 88 Kg which lowers the upward lift of the aerostatic balloon to 73 Kg. Such value is more than sufficient to load the module with about 40 Kg of mechanical, electric and electronic components.

The use of a 350 metre long cable allows the aerostatic module to station at an altitude of 200 metres and allows it a run equal to 290 metres.

 

LIFTING MASS

The weight utilized during the recovery phase of the aerostatic module with closed parachutes, must be sized on the temporal duration of its recovery run and on the wind energy that strikes it during this passive phase.

Power during the passive phase was  previously measured at 1 Kw and the time necessary to complete the phase, 54 seconds, is equal to that required in the previous phase by the wind to push the module to the end of its run (290 metres, 5.48 metres per second).

In order to convert the energy of a single run into Kgm, it is necessary to multiply a value of 1 Kw by the fraction of hour (54/3600) thus obtaining a value in Kw/h. By dividing the resulting value by the conversion coefficient 0.00000272 a value of 5.515 Kgm is obtained; this can be broken down into the weight and height components.

The weight utilized in the prototype is a cube of granite, one metre long and 2700 kg heavy that accumulates the necessary energy by being lifted at a height of 2 metres.