This work deals with the main control problems found in solar power systems and the solutions proposed in literature. The paper first describes the main solar power technologies, its development status and then describes the main challenges encountered when controlling solar power systems. While in other power generating processes, the main source of energy can be manipulated, in solar energy systems, the main source of power which is solar radiation cannot be manipulated and furthermore it changes in a seasonal and on a daily base acting as a disturbance when considering it from a control point of view. Solar plants have all the characteristics needed for using industrial electronics and advanced control strategies able to cope with changing dynamics, nonlinearities and uncertainties.

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This paper studies the impact of the information and communication technologies (ICT) on economic growth in Spain using a dynamic general equilibrium approach. Contrary to previous works, we use a production function with six different capital inputs, three of them corresponding to ICT assets. Calibration of the model suggests that the contribution of ICT to Spanish productivity growth is very relevant, whereas the contribution of non-ICT capital has been even negative. Additionally, over the sample period 1995-2002, we find a negative TFP and productivity growth. These results together aim at the hypothesis that the Spanish economy could be placed within the productivity paradox.

a b s t r a c tThis paper studies the impact of information and communication technologies (ICT) on US economic growth using a dynamic general equilibrium approach. A production function with six different capital inputs is used, three of them corresponding to ICT assets and the other three to non-ICT assets. The technological change embedded in hardware equipment is found to be the main leading non-neutral force in US productivity growth, accounting for about one quarter of total growth during the period 1980-2004. As a whole, ICTspecific technological change accounts for about 35% of total growth in labor productivity.

This paper investigates the implications of vertical fiscal externalities for the optimal federal tax and the sign of fiscal gap in the presence of ad valorem taxation. It is shown that the federal government can always achieve the secondbest optimum for public good provision. The sign of the fiscal gap is, in general, ambiguous. The consequence of this is that a precise evaluation of the fiscal gap requires an explicit consideration of the underlying fundamentals of the federal economy.