I cannot believe that nobody is concerned by Photovoltaic systems efficiency in shadowed zone !!
OK this topic is not a basic explanation about how a usual PV system is designed and installed.

Many European countries are already talking about it: it is a brand new technology and i am curious to know what you think yourselves: Designers & Contractors ?

Shadowed zones are due to the environment, there are many buildings within cities in such situations.

Solution is to integrate in each PV module one micro inverter instead of having only an inverter linked to the whole system of PV modules.

• Need to get more technical
  explanations ?

Lots of small companies are offering such systems:
Enphase Energy technology,
GreenRay solar,
SolarEdge,
Enecsys ...

• if you need to have a comparison between 9 offers with arguments, plus / minus ?

Last issue is a quality issue: is this new technology reliable enough ?, debate is open:

• As a contractor, are you confident ?