Donnerstag, 19. Juli 2012

Storage Maters


Fuel is Stored Solar Energy

We live in a world, where the energy we consume was stored eons ago by nature. The conversion efficiency of solar energy into oil was really lousy, only a fraction of the solar radiation was converted to biological mater, only a fraction was laid down into the ground and only a fraction is now available. If we do the math, we find, that less than one billionth (10E-9) of the solar energy, which reached the earth within the last 100 million years, is stored in our fuel resources. This leads to the idea that we can do better than nature!Using solar radiation energy conversion systems like photovoltaic or concentrated solar power, we end up near 20% conversion rate, which is sufficient for economic land use and by a factor of 100 better than plants, who only convert 0.1% of the energy in usable fibers or sugar. It should be mentioned, plants need water and solar cells love deserts! Resulting in no competition of land use if we are smart and don’t plant for energy but plant for food.

The Storage Problem Remains

There remains a problem, storage! Storage was never an easy business, but if solved it changed the world. Inventing hey for example was necessary to conquer the north hemisphere, where in winter time is no food for the livestock. Storing information in books was the breakthrough for the industrial age and unlimited computer storage capacity is essential for our information age.   

The upcoming renewable power age lacks of efficient and cheap storage capacity for electricity. Knowing this, we could visit the known technologies and there potential to solve the problem if further developed. Best known to the public are batteries. This is by the way a big problem, because our politicians, driven by their simple mind and the public, believe in batteries. Batteries are fine for mobile applications like cell phone and laptop. Cars using batteries are still expensive, but it may be within the reach of our technology to power them by batteries. Things get much more difficult, if we want to use batteries for grid scale applications.

Batteries are expensive, and need some more or less rare and expensive metals, they use processes which are not perfect rechargeable, this is the reason that batteries run out of business after a few thousand charging cycles. All this does not matter, if we use a mobile phone, live time is limited, the price of the battery is not the main value of the device and we don’t care to much on the environmental impact on the small scale that is involved.

Grid Scale Storage is Different

If we need storage for large scale, and grid technology is always about GW and TWh, values, which are trillion (10E12) times above the mobile phone and laptop scale. This is by the way easy to guess, as long as billions of consumers are out there. There are three different questions, how expensive is the storage capacity, how many times can we recharge it, and how efficient is the process. The reason why price matters is we can only earn a limited amount of money on every charging cycle. If the battery lifetime is already finished, before we have earned enough money to pay for the battery itself, it is useless to buy the battery at all.  The situation for the efficiency is in some way similar. If we have to pay more for the energy to charge the battery as we earn during discharge, the system doesn´t work either. The problem of efficiency is not the core problem of batteries, but of many other storage concepts. Batteries suffer from the price per storage capacity. 

Why Batteries don´t Work

Price of storage capacity for many batteries is above 200$/kWh, even for the very simple and widely used lead acid battery. Lithium based systems are often above 1000$/kWh although prices were dropping during the last two decades. Let´s do a simple calculation; our battery should be charged every day, as it makes sense in solar power systems. During nighttime the price of power should be 10ct/kWh more expensive as at daytime. If we discharge the battery, we earn 10ct every day and within six years we have a return of our investment into the lead acid battery. But this does not hold due to the fact, that our battery dies after about 1000 cycles. Using the Lithium system, things are even worse, we have to wait about 30 years for the return of our invest without any interest rate, this does not attract many investors.

More Storage Technologies

We visit other techniques of storage in the next blog posts

  • Methane
  • Pumped Hydro
  • Hydraulic Hydro Storage


1 Kommentar:

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