1. Introduction

Electricity is also the source of energy which moves one of the general purpose technologies, the electric engine. On the concept of general purpose technology, see Lipsey ( 1998).

About 885 million TWh of solar energy is received by the Earth every year. This could lead to 400 thousand TWh/year, which represent about 3000 times the current annual world primary energy consumption. In a clear day, with the sun being close to its zenith, solar radiation would reach ~1 kW/m ². This is partly direct solar radiation (solar rays impacting directly from the sun) but also partly solar radiation disseminated by the atmosphere. Any place in the planet has daylight half of the year, although its monthly share can be very different according to the latitude and the weather (at a local level). Therefore, the solar energy which reaches the surface is maximum in the arid tropics (up to 2300 kWh/m ² and year), descending to half in the temperate regions of the north (Alaska, Scandinavia, Siberia) and the south (Tierra del Fuego, New Zealand’s South Island).

Concentrating solar power uses the heat power of the solar light in order to generate steam and, thus, move a turbine and a generator connected to this one. There are also other options. One of this is direct solar thermal power generation using thermophotovoltaic cells, which convert the heat into electricity. This energy transformation, whose origins go back to the 1960s, has several technical variations, all of them in the conceptual design or laboratory experiment stages. See Andrews and Jelly ( 2007: 157–159) and Deng and Liu ( 2009).