[MUSIC] Hello, this session is an introduction to the basic calculation of hydropower resources. This will help to understand which countries or regions, have a high potential for hydroelectric production. We have seen that the water cycle which take place in the atmosphere, allows the huge amounts of water to be transported each year, from the sea to the top of the mountains. Such water mass, which is deposited by the rain at high altitude, leads to a significant amount of potential energy. This potential energy is written as a product of water mass M, times gravity, G times the altitude delta Z, relative to the sea level. This mass of water can be estimated from the height of the annual precipitation times, the surface area of the region considered. However, not all the rainfall can be used on a given surface, indeed, a fraction of the rain will be evaporated very quickly and another will be absorbed by the vegetation. Therefore the useful fraction that will flow and accumulate in lakes or river, is given by the runoff coefficient. This runoff coefficient varies according to the nature of the terrain, whether it is mainly rocky or composed of meadows or forests. Thus depending on the nature of the region, this coefficient can vary from 20 to 45%. For instance, in France, the National Weather Service provides accurate maps of the average annual precipitation expressed here, in millimeter of rainfall received per square meter. If we compare this rainfall map with a topographic map, there is a strong special correlation between average rainfall and terrain elevation. The four areas where the rainfall exceeds 1,500 correspond to the four mountainous area, which are the Pyrenees, the Massif Central, the Alps, and Corsica. Here, we recover thermodynamic behavior of the water cycle. Mountains, for the air parcels pushed by the wind to rise in altitude, hence, the temperature of the air parcels decrease, which increase water vapor condensation, and local precipitation. Other areas of moderate precipitation are also found on Brittany, and kowtow. These areas are directly impacted by the western terrain of oceanic storms, but here the topography is low and the accumulation of potential energy will therefore be negligible. If now, we try to estimate very roughly the hydraulic potential of the Alps, we consider an annual rainfall of 1.5 meter, and an area of about 38,000 kilometer square. And, an average altitude of 1,500 meter, by taking a mean one of coefficient of 40%, we obtain an annual potential energy of about 100 terawatt hour, about 9,000 tons of oil equivalent. If we compare this first estimate, which is very simplified with a more complete calculation on the hydro program resource in France, we get the correct order of magnitude. Indeed, the complete calculation for the global hydropower gives 260 terawatt hour. It is higher than 100 terawatt hour because it includes in addition to the alps, the Massif Central, and half of the Pyrenees. Thus, this simple calculation of the potential energy, give the first estimate of the maximum amount of hydropower energy. To have a more relevant estimate, it is necessary to take into account the efficiency of hydroelectric power plants, which are about 75 to 85%. It is then necessary to take into account the technical constraints related to the environment. You cannot install a dam on each lake, and on all the river and all streams. Thus, if we take into account what is technically feasible and realistic, we obtain a maximum hydroelectric potential of 100 terawatt hour, for the whole France. And today French hydroelectric production is around 70 terawatt hour, which is about 70% of what is technically feasible. This corresponds to 12.5% of the French electricity production, that we must compare to the 71% of the total electricity generated by nuclear power plants. The rest of the electricity mix comes from thermal power plants 7%, and then from all the other renewable energies, wind, solar and biomass. Hydropower therefore remains the leading renewable energy source in the French energy mix for many years to come. Although not huge, the development of hydroelectric facilities is not negligible. We consider that we could still install some new hydroelectric power plants, or improve the old ones in order to gain about 10 terawatt hour, of production. If now we look at the world hydroelectric production China is in the lead, accounting for nearly 30% of the world production. Then there are Canada, Brazil, the United States, the Russian Federation Norway and India, wait a minute, Norway, why Norway? Which is a small country is between Russia and India for hydroelectric production, is there a mistake? Let's take a closer look, Looking at the annual rainfall map in Europe, Norway is the region with high rains. If we look now at the topographic map, we can see that most of the country is a mountainous region. Norway tests combine heavy rainfall, and a strong oceanic weather with a large mountainous area. The hydroelectric potential of the country is therefore tremendous. This makes Norway the world champion of renewable energy, with almost 99% of its electricity production coming from hydropower. Let us now have a look at the global distribution of the hydroelectric capacity and production for each continent. They are indicated by the large blue and dark green disk on this map, respectively. The Asia Pacific and Central Asia regions, are in the lead with a very high potential for further developments. North and South America are also regions with a strong potential in hydropower development. In comparison, Europe which has a slightly larger capacities than North America with a surface area half as small, is much better equipped with hydraulic installations. We have seen that a simple calculation allows to estimate the order of magnitude of the annual hydroelectric resource for a given region. However, this resource can vary from one year to another, and even evolve on a time scale of several decades. I invite you to follow the next sessions to discover the causes of these inter annual variations, thank you. [MUSIC]
