Previous attempts to reduce greenhouse gas emissions haven’t been successful, and if we consider the current situation it’s worth pointing out that emissions stabilization won’t lead to a stable concentration of carbon dioxide in the atmosphere. To reach that goal we should reduce emissions steadily, and therefore we need to think of alternative solutions that could compensate with the required reductions in the use of fossil fuels. These sources have been so central in our life throughout the twentieth century that we are now hardly able to think of energy by referring to other sources.
Let’s make an effort and try to think different. With the exception of geothermal energy and tidal energy, all the other renewable forms we can think of come from the sun: wind power is solar because the winds are driven by the sun’s heat, the same way winds drive the waves that generates wave power.
Generally speaking, natural energy sources like the one generated by solar panels or wind turbines are hugely criticised because they depend on local weather conditions, and therefore it’s difficult to produce the same amount of energy that we can get through the combustion of fossil fuels.
However, an important step forward has been done to solve this problem: solar power plant able to generate electricity for 24 hours a day, 7 days a week.
The first utility-scale commercial baseload solar power plant has been realised in Spain (province of Andalucia) and it was first launched last May.
Gemasolar, this is the name of the solar plant, differs from the most famous photovoltaic panels. This system is based on the concept of storage. In fact, the plant is made of two tanks of molten salt thermal energy storage (MSES) which allow the solar plant to generate energy during the night or even during cloudy or rainy days. MSES is made of a combination of potassium nitrate and sodium nitrate that, thanks to their properties, allow the plant to lose only 1% of its heat energy a day.
This system is expected to produce about 6,400 hours per year, a capacity factor of 75% which is more than the 50% reached by the Three Gorges Dam in China.
Looking closer to the solar field, we can see that it’s made of a series of glass heliostats positioned all around a central tower. Each single heliostat needs to be moved in the right position in order to catch as much sunlight as possible and reflect it on a central receiver on top of the tower.
Sodium and potassium nitrate salts from the cold tank are pumped up to the receiver where they absorb the solar thermal energy that can usually reach up to 565°C, then the heated salts are pumped down to the hot tank were they can be stored or used to generate electricity by the heat engine. The energy gathered by the 2,650 heliostats is considered to be able to power 25,000 homes, but only if they are properly inclined.
The International Energy Agency (IEA) considers that solar power energy can contribute to satisfy up to 11% of the electricity demand by 2050.
If we think of either the reduced availability of oil and its rising price, we are likely to think that this system will become an efficient response to the increasing demand of clean and cheap energy in the future.