Electricity can be produced in two different ways: 
  photovoltaic  or  thermodynamic. Today,  only  decentralized 
  production  of  solar  electricity  can  be  envisaged as an 
  economic possibility.  For very small amounts of power (to 5 
  kW), photocells are definitely most appropriate. Beyond that 
  level,  photovoltaic  and  thermodynamic  conversion  may be 
  competitive.  While  it  is  possible  for  the situation to 
  change, it  must  be noted  that at present, solar-generated 
  electricity is often too costly.  However, photocells are an 
  ideal power  source for remote areas and for equipments that 
  require  only  little  power: school  televisions  (20-30 W), 
  Hertzian  relays (1-100 W),  air  radio - navigation systems 
  (6-400 W), railroad  signals (to 500 W), and  telephones  in 
  rural areas (0.5-60 W).
  The  production of high levels of electricity (1 MW and more) 
  may  be  justified  only  when  the  electricity produced is 
  integrated into one utility grid.  The difficulty of storing 
  energy  for  night  use may impede the isolated use of solar 
  plants.  Fortunately, solar electricity works very well as a 
  supplement to the traditional electricity sources: hydropower, 
  fuel fired and nuclear plants.  The thermodynamic conversion 
  systems  are  classic: alternative  engines (Rankine); steam 
  turbines (water  and  organic) ;  gas  turbines.  All  these 
  generation  systems  have  been  field  tested, and the only 
  problem   that  arises  is economic in nature.  However, the 
  economics of solar power production may be improved by using 
  cogeneration  techniques, providing  both thermal energy and 
  mechanical  or  electrical  power,  and  using  the normally 
  wasted  heat  properly.  A  good  deal  of research has been 
  carried out to establish the capability of solar electricity 
  (photovoltaic  or  thermal)  to  compete in the future  with 
  conventional  electricity  sources.  In the short and medium 
  term,  solar  electricity  will  be  widespread in  isolated 
  applications only.