24 Hour Solar Power

This is for all those that say Solar can’t be base load power.

Spain has opened for the first base-load, 24-hour industrial scale solar thermal plant.

The concept is very different from what most people think of as solar power.  Most people think of solar panels.  These produce electricity by exciting a compound with sunlight and that excited compound causes electrons to flow, producing electricity.  This is called photovoltaics.

Solar thermal is very different.  Concentrating the sunlight reflecting off of thousands of mirrors onto a small area results in that area getting very, very hot.  If you can capture and store that heat, then you can use it to boil water, producing steam and generating electricity using standard steam turbines.

This has several advantages over photovoltaics.  The first is simplicity.  Steam driven turbines are a well understood technology, so people trained in energy production from other sources (coal, gas, and nuclear) can transfer their skills.  Also, there sunlight part is only mirrors, not solar panels or other high-tech system, just plain old mirrors.

Second, the system generates a lot of heat.  In reality, every energy system in use today is based around capturing the work done by flowing heat energy.  Basically, heat moves from hot things to cold things until they are the same temperature.  We can capture that flow of heat and transform some of it (usually around 30%) into a different form of energy (electricity or the motion of cars).  The greater the temperature difference, the better it is for capturing the energy.

Third, it is possible to store heat.  That is the real trick to this system.  It uses a salt (not salt, a salt) that is heated to the melting point by the solar mirrors.  The salt is the heat source.  Since the salts used (Potassium Nitrate and Sodium Nitrate) melt between 304°C and 334°C (that is 579°F 633°F) they can turn water into very high pressure steam easily.

These salts also retain that heat very well.  This Spanish system is rated for electricity production for 15 hours even without any sunlight.  It retains up to 99% of its heat after 24 hours if not used for electricity.  They call this system a battery, even though it’s not really a ‘battery’.

This system is expected to have a capacity factor equivalent to nuclear power systems.

This is the ‘solar tower’ concept you may have heard about.  Simply thousands of mirrors, constantly adjusting their angle, keep several acres worth of sunlight focused on that molten salt.

Tubes run through the salt with water in them.  The heat transfers from the 600°F salt to the water, which flashes into steam.  The steam, at a very high pressure, is used to drive a steam turbine.  This power plant is rated at almost 20 Megawatts and can provide power 24/7 under ideal conditions*.

The disadvantages, well, you do need lots of space and a constant supply of sunlight.  Deserts, plains, etc are great places for these kinds of power plants.

Well, there you go, 24/7 solar.  To all the naysayers out there, I just have this to say.

nyah, nyah, nyah


* remember that no power plant can operate under all conditions, witness the two Texas power plants that had to shut down after their water intakes froze.

This entry was posted in climate, Education, Environment, Ideas, renewable energy, Science, Technology and tagged , , , , , , . Bookmark the permalink.

1 Response to 24 Hour Solar Power

  1. Pingback: 24 Hour Solar Power | Γονείς σε Δράση

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