I added a comment of the preprint:
The central heating wire mentioned in the preprint looks to be a suitable solution to keep large balloons in the air even without lift by Magnus effect when there is no wind. Indeed a minimal rise in temperature is necessary, especially if the cover is made of ripstop which is a lightweight fabric used for hot air balloons, kites, sails, para-gliders etc.
The centrifugal force due to the rotation could perhaps have a positive effect if the hotter air comes from the central heating wire, pushing the colder air against the walls, insulating the hotter air in the middle next to the heating wire.
Some calculations for various balloon dimensions. U-value is the “thermal performance” mentioned on https://www.birdair.com/files/brochures/Birdair_ETFE_6pg_WEB.pdf . Formula: "U-Value (W/m² K)". The value of 3 looks to be a realistic U-value. To simplify 0 degrees Celsius corresponding to 273.15 degrees Kelvin, rounded to 273 degrees K.
The table (in French) on https://www.thermexcel.com/french/tables/massair.htm was used for the air mass versus temperature.
The cylindrical balloon of 690,800 m² (200,000 m² for the Magnus effect), 1 km long, 200 m in diameter, 3,1400,000 m³, would require approximately 3.454 MW for an elevation of temperature from 273 K outside to 278 K inside, i.e. a gain of 0.021 kg/ m³, or 659 tons in total, for a mass of 100 tons. With U-value of 3, this would give 10.362 MW, which is still little compared to the average power developed with a wind of 10 m/s (80 MW). With 273 K exterior and 275 K interior we would have 0.009 kg/m³, or 306 tons in total for (690800 x 275) minus (690800 x 273) = 1.3816 MW and 4.1448 MW with U-value of 3, which is very little while we remain well above the mass of 100 tons. With 273 K exterior and 274 K interior we would have 0.004 kg/m³, and 125.6 tons in total, which is fair, and this for (690800 x 274) minus (690800 x 273) = 0.6908 MW, and 2.0724 MW with U-value of 3, which is minimal. If you take into account the centrifugal force, the U-value would perhaps be a little lower. The centrifugal force is higher as the diameter becomes smaller and the angular velocity higher. The larger the balloon, the less power required for its aerostatic lift in relation to the power developed.
Cylindrical balloon 100 m in diameter and 500 m long, 172,700 m² (50,000 m²), mass 25 tons, volume 3925,000 m³, average power 20 MW with wind speed of 10 m/s. (172700 x 278) minus (172700 x 273) = 0.8635 MW and 2.5905 MW with U-value of 3, for a gain of 0.021 kg/m³ (see above), or 82,425 tons. With (172700 x 275) less (172700 x 273) = 0.3454 MW and 1.0362 MW with U-value of 3, for 0.009 kg/m³ therefore 35.325 tons, which is still above the mass, for an expenditure of low energy.
Cylindrical balloon 50 m in diameter and 250 m long, 43175 m² (12500 m²), mass 6.25 tons, volume 490625 m³, average power 5 MW with wind 10 m/s. (43175 x 278) minus (43175 x 273) = 0.215875 MW and 0.647625 MW with U-value of 3, for 0.021 kg/m³, or 10.303125 tons, which is well above the mass, for an expenditure of reasonable energy.
Cylindrical balloon 20 m in diameter by 100 m long, 6908 m², 31400 m³, heating from 273 K to 278 K requiring 34.54 kW, and 103.62 kW with U-value of 3 for a gain of 659 kg. Mass of the balloon (0.1 kg/m² and heating wire) 1000 kg: this is therefore too little. With 50° we would have a gain of 6280 kg, for (6908 x 323) minus (6908 x 273) = 0.3454 MW and 1.0362 MW with U-value of 3. With +27° (300 K) and 0.116 kg/m³, i.e. 3642 kg in total, it would be necessary (6908 x 300) less (6908 x 273) = 0.1865 MW and 0.5595 MW with U-value of 3. With + 10° (283 K) and 0.1247 kg/m³ we would have 0.045 kg/m³, or 1413 kg in total, which is sufficient, and for (6908 x 283) minus (6908 x 273) = 69.08 kW, and 207,240 kW with U-value of 3. This remains a lot but still acceptable compared to the power developed (0.8 MW with a wind of 10 m/s).
A cylindrical balloon 2 m in diameter by 10 m long, 31.4 m³, 69.08 m², mass 10 kg with the heating wire and 0.1 kg/m² of fabric or plastic, would require approximately 345 W (U-value = 1 ) for a gain of 0.021 kg/m³ for heating from 273 K outside to 278 K inside, i.e. 0.659 kg in total. With an increase of 50 degrees from 0 degrees, we would have 0.2 kg/m³, or 6.28 kg in total, it is still insufficient. With an increase of 85° from 0° we would have 0.306 kg/m³, and this is just below the equilibrium point. You would need air at 100 degrees which weighs (dry) 0.946 kg/m³, or a gain of 0.346 kg/m³, or 10.86 kg, which is slightly above. The heating power would then be (69 x 373) minus (69 x 273) = 6900 W (U-value = 1) and 20700 W (U-value = 3). As the centrifugal force would be much greater, we can assume that the U-value would be lower. This is still too much compared to the power developed (8 kW) with a wind of 10 m/s.
The 90 g/m² double-layer aerofabrix ® fabric (https://ultramagic.com/hot-air-balloons/eco-magic/) would be a good insulator, although not very useful due to the very small temperature differences between the outside and the inside (around 2 degrees) for the two largest balloons, and the centrifugal force becomes increasingly important as the dimensions decrease. Silver ripstop would be sufficient, less heavy and less expensive.