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Spain shows the way

From a Madrid contact:

At this moment, Spain has about 150 MW of thermo electric plants connected to the grid; some 750 MW are under construction and some 14 GW of these types of plants have requested license and have established the required bonds by the Spanish government. There are basically three types of plants:

Mirrors with 2-axis trackers pointing to a boiler in a tower, with 10 and 20 MW models, producing high temperature.

Parabolic through mirrors with a tube in the longitudinal axis, collecting a fluid (synthetic oil at 400 Celsius) to a heat exchanger, usually molten salts coming from Chile, able to keep the system operating for at least 7 hours with this molten salt energy buffer, if clouds or similar appear. In the other side of the heat exchanger, steam is generated and a turbine is powered with it. If the lack of sun last longer, they connect the gas or fuel combined heating ystem. This is the most common system being installed and in operation today.

A typical plant of 50 MW takes some 1,200 m*1,200 m and needs a water flow of 6 liters per second to refrigerate, which sometimes is a problem for the licenses in places where water is already very scarce, although they are studying some more complex alternatives with air refrigeration.

Some of the plants do not have the heat exchanger and they just inject into the grid, when there is salt. The Spanish regulator has issued norms and strict regulations for these operators, to inform and predict the network operator and regulatory body of the energy generation forecasts every day in advance and every hour in advance, so that they are heavily penalized if they deviate ±5% from forecasts. However, they can modify in advance their forecasts and report the changes to the regulator, one day in advance for every next day and one hour in advance for every hour forecast. A number of companies has speciallized in
wheater forecast, with thousands of sensors throughout the country and in the neighbouring countries, so that they know, when a storm is in the Atlantic, how much energy they will generate in a wind field (17 GW installed poweer and 12% national eelectricty consumption) 6 hours in advance. And for the sun, they have plenty of sensors throughout the
country (pyranometers and others), so they know if the air is clear or not and if radiation will be in a zone at the level of 800 W/m2 or 570 W/m2 well in advance.

This is not marketing. This is a reality. Spain today is generating 17% of its electricty (some 340 TWh/year) by hydropower (a relatively dry country), 12% by wind and already 1% of solar power, going fast to 3-4% of solar power. Besides, there are other generations considered under
"special regime" which are based in renewables, like waste burning and other biomass. And there is a strong a live debate on whether to shut down Garoña nuclear power plant (1% of the national electricity), after having reached to its life cycle or to extend another 10 years, with two
strong groups debating in all media. The nuclear power contributes with 20% to the national consumption (8 nuclear power reactors in 6 sites)

The other big debate is how much a grid like the Spanish grid (almost an island, with small interconnections with France, Portugal and Morocco) could afford in renewables with intermitant generation. And if there are technical limits to the renewable systems. A couple of Portuguese
institutions (now about 2,8 GW installed wind power) have mentioned that a probable peak in wind power for Portugal in suitable sites is in the range of 6 to 8,000 MW. Being Portugal four times smaller than Spain, we may guess that a level of 30,000 MW installed wind power (precisely the
levels forecasted by 2020) may be close to wind fields classes (6 or 5) which make feasible now the installations. Promoters are struggling for fields with 2,000 hours nominal, as all other better fields are almost covered or not feasible (i.e. national parks, etc.) As for how much a
grid like ours, with daily consumption peaks of 40,000 MW and night consumption valleys of 20,000 MW can afford in renewable penetration, there are many debates. The base load is already about 20,000 MW (the total night valley consumption) which can hardly be regulated (as it is
supplied with nuclear and coal and working round the clock, with difficult regulation levels). So, when a day is very windy during the night, most of the 17,000 MW of wind power have to be automatically disconnected, with the frustration of the promoters of wind farms, which delay their return on investment. So a conventional fossil fuel back up is always necessary, but is working sometimes against the wind power.

Pump up energy storage systems from dam to another upper dam are used, but only cover about 1.8 percent of the total national electricity and experts in the electric utilities doubt that could increase to significant levels, even we have a mountainous country with over 90% of the big river basins already occupied by dams.

Solar is much more in line with daily consumption of electric energy, but is taking a big portion of agricultural lands (6 Ha per MW with trackers and 3 Ha/MW in fixed systems) and creating protests in the officials in the Ministry of Agriculture and some environmentalists,
starting to see that renewables are sometimes not as "clean" as expected. Rooftop installations are not progressing, when talking in volume. Fixes are much more complex. Volumes on the ground make much more competitive tha in rooftop configurations. Legal problems also count. And the roofs are in most of the cases not well oriented or with plenty of shadows in urban environments, a critical issue for a system
very much in the edge of energy and financial efficiency, even it is heavily subsidized by premium tariffs (at present level at 0,30€/kWh and coming down faster than technology improvements can match, because lack of financial resources, coming from a fossil fuel State and fossil fuelled society)