In my opinion I would choose what I used in my article, a Darrieus straight blade with a second set of blades added to it.

at what speed this type of Darrius start ?

Savoniuos I think.. 

Darrieus with adjustable angles of blades during rotation.

Turbines with pitch control are recommended, however, the complexity of their design lead to higher cost and not always feasible. In this case, combined Darrieus-Savonius hybrid turbines may be suitable alternatives, have the advantage of low wind start-up and acceptable peak performance.

Hi Bushra,

While technically you can use VAWT in urban areas, in reality the performance is so much diminished due to lower wind speeds (because of z factor), that it might not be economically feasible to generate a reasonable amount of energy. 

http://aip.scitation.org/doi/abs/10.1063/1.4952209?journalCode=apc

https://www.windpowerengineering.com/design/vertical-axis-wind-turbines/

http://ieeexplore.ieee.org/document/7280957/

https://commons.clarku.edu/cgi/viewcontent.cgi?article=1158&context=idce_masters_papers