Using incident solar power numbers from wikipedia, puts Europe at something like 150W/m^2 average for the year.

At 8% conversion efficiency:
150*0.8*365*24*60*60 = 378,432,000 J/(year*m^2)
For disel, 11kWh/L = 11000*60*60 = 39,600,000 J/L
So, per square metre disel equivalent yield per year:
378,432,000/39,600,000=9.6L/(year*m^2)
or 96,000L/(year*hectare)[sounds like a lot more than 3000. Do I have an extra zero??]

The EU used 494616 kTOE in 2005
In joules: 494616*1000*42e9 = 2.0774e19 J
Which, converted to diesel litres is: 5.2459e11 L
Per percent replacement: 5.4645e8 m^2
or 54645 hectares per percent replacement of 2005 fossil fuel usage.