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07.16

Land demand for solar power

Solar energy for Germany, Europe and the world

There is a picture in the solar scene (picture 1) that probably almost everyone knows, it shows how large the surface area is when the world is switched to solar energy. It was, as far as I know, published by Mrs. Nadine May for the first time in her diploma thesis at DLR [1]:

Figure 1: Space requirements for solar power plants, according to Nadine May [1]
This image is widely used and should be checked for correctness. First of all, Algeria is the country that contains the squares for the world and Europe, and Libya, the country which possibly receives the German solar power plants, are no more colonies.

The squares have an edge length of: world 254 km, Europe 110 km and Germany only 45 km.

How big is the energy consumption in the world?

The energy consumption of the world is constantly growing (see figure 2), so it is difficult to specify the energy requirement without a reference year. Currently the demand is over 30,000 TWh (30,000,000,000,000,000 kWh) using the further processed data from the International Energy Agency (IEA). I have considered transforming factors for certain energy forms (transportation, heating) into electricity.

Figure 2: Global energy demand for electricity, transport and all other forms of demand

This energy should be converted with solar cells (PV) into electricity. There are several factors to consider, the efficiency, the irradiation in the course of a year and the necessary storage of the energy for the night.

Solar cells made of silicon achieve an efficiency of around 20% and are currently the most economical method to generate large amounts of solar energy.

The irradiation is very different in different regions of the earth, in particular one must always distinguish between direct and global irradiation. For photovoltaics (PV) only the global irradiation plays a role. Therefore, only these radiation is considered.

Figure 3: Global radiation perpendicular to the ground (source: WEC [2])
The map shows that many areas have an annual irradiation capacity of 2000 kWh per year, in particular the Sahara, but also on other continents good locations can be found; only exception is Europe.

Necessary Land Area

The necessary areas of the solar cells can now be easily calculated. For the world, we need 30,000,000,000,000,000 kWh per year, since one square meter has an incidence of 2000 kWh which would theoretically be 15,000,000,000 m� or 15,000 km�.
Now the efficiency comes into play, since only 20% is converted into electricity, we need the fivefold area, that is 75,000 km�. However, one has to be able to build the cells and needs paths and additional areas for inverters and storage, which should double the space requirement. This is 150,000 km�.
The transport and storage of energy, which is absolutely necessary, since at night the sun doesn't shine, will consume another 25% of the energy, so we are at 200,000 km�.

This corresponds to a square of 448 km of edge length, roughly twice as large as in the drawing.

Fair World

Currently, only a few people consume a lot of energy and lots of people have little energy. I am convinced that in the long term all people want at least to reach the standard of living as in Germany. For this, an energy quantity of 15,000 kWh per year and per person would be necessary. There are some countries that already have a much higher energy requirement, but we hope that energy efficiency will also save some energy.

With a world population of 8 billion people, this will yield an annual energy demand of 120,000 TWh or 120,000,000,000,000,000 kWh, or four times the current demand. This would increase the area with solar cells to a square with an edge length of 1000 km (Fig. 4).

Figure 4: Supply the world completely with solar energy in the future
Furthermore, the area of ??one million square kilometers is still small compared to the Sahara, but a serious part of the solid surface of the earth. The world has about 15 million square kilometers of sunny deserts, which means about 1/15 of this area must be used in the future for solar cells to deliver enough energy.

Storage requirements

If it is assumed that the energy must be stored for at least one day, this requires a storage capacity of 330 TWh (330,000 GWh)
Compared: Germany has pumped storage with a capacity of 0.04 TWh.
If large Gravity Storage systems with 80 GWh capacity (500 m diameter) solves the problem, a considerable number of 4000 pieces would have to be built.

Using batteries from Elon Musks Gigafactory, the gigafactory produces at a planned capacity 50 GWh per year; over 6000 years of production or 400 Gigafactories for 15 years are required. This is to provide the capacity for the first time and we have to continue production because batteries must be replaced after 15 years.

Gigantic conversion

If the global conversion to solar energy succeeds, huge buildings in the form of gigantic solar fields will be necessary. Surely the roof surfaces are never enough. Furthermore, investments are in the order of magnitude of the global gross social product of one year ($ 80,000 billion). This sounds a lot, but it will help mankind to be sustainable. Especially when one considers that afterwards energy is produced clean, without CO2 and at a low cost.

I think: we can do it!


Sources:

[1] Eco-balance of a Solar ElectricityTransmission from North Africa to Europe, Diploma Thesis of Nadine May, Braunschweig, May 2005

[2] World Energy Resources Solar 2016, World Energy Council 2017

A 186 page paper going into details is from Jakobson et.al., 100% Clean and Renewable Wind, Water, and Sunlight (WWS) AllSector Energy Roadmaps for 139 Countries of the World
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12.56

Energy Storage Demand in a Sustainable World

The global transition to renewable energy production is in progress. Last year, 2015, more renewable power capacity, like solar and wind power, was installed as conventional capacity like coal and nuclear. Beside this nice development, there is a weak spot, the installed solar and wind capacity produce only when the sun is shining or the wind is blowing. For a full change to an emission free world, we need energy storage.

How big is the storage demand on a global scale, this is hard to guess, because it depends on a lot of assumptions. I will try to make a good guess within this post.

The Global "Energiewende" 

I will not describe the "Energiewende" (change of the energy system) in Germany, I will focus on the global change. This makes sense, because we have to change the energy system on the global scale to stopp the carbon problem and limit the exhaustion of the scare fossile fuels. 

The strong growth of PV installations, about 70 GW are expected for 2016, continues the long term trend of constant fast growing installations over the last decades. 

This trend will change the energy system as we know it today within two decades, to understand this lets look into the near history.

Growth of the energy consumption and the installed renewable energy production.
Consider the logarithmic axis of the installed power. Data source BP 
The first thing is, the electric power demand has a constant annual global growth of 3%. The installation of wind and solar power combined grows every year with 22%. The result will be, that somewhere around 2025, more fluctuating renewable energy is installed as conventional power plants. 

But be careful, the produced energy of wind and sun will still not match the demand, because they only produce energy when sunlight or wind is available. Resulting in the green line, which represents the mean renewable power generation. This line hits around 2030 the demand.

The result is, the next century will be dominated by the installation of storage to match the flucuating production at any time with the global demand.

Influence to the Storage Demand

The main impact for the storage demand has the electric grid infrastructure. The reason is, that the grid is the most efficient way to transport the electric power from the source to the customer. Is the sun shining in the southern part of a country, it is efficient to bring the energy to the cloudy northern part. And similar, if the northern part has a lot of wind during the night it makes sense to bring the energy with the same grid to the customers in the southern part.

This results in a competition between grid and storage.

To find the economic optimum between power grid size and storage is complex
Theoretical, it would be possible, to span a global grid around the globe and connect this grid with all solar power plants. This would result in a perfect 24 hour solar power supply without any energy storage at all because the sun shines always at some places on our earth.

The main problem seem the high price of such a grid and the energy loss in the power line. The other extreme case is a power storage at home with a seasonal capacity (only necessary in the northern region) of 1000 kWh for every person in the house. Then we can go off grid, sufficient PV on the rooftop assumed. The price for the batteries may reach a million dollars, not affordable.

If we dive into detailed computer simulations as done by J. Tambke und L. Bremen [1] we learn, that a country like Germany needs a storage capacity of seven days after a complete conversion to wind and solar has happend and there is a perfect power grid, often called a copper plate. 

Expanding the area of the perfect grid connection to an area like Europe only two days of storage is necessary. If we are optimistic and assume a perfect grid of this semi continental scale we need only a storage capacity of two days.

Further Chances to Optimize

Beside the grid, another chance to minimise the storage demand is the so called smart grid. Whenever possible, a energy consuming element in the grid goes offline if the power price is high or goes online if the price is low.

We dont know the exact possible amount of energy demand that can be shifted to other times but a optimistic guess might be, that 50% of the demand can be shifted in a way that the storage demand is halved.

Asuming this, we need only one day of storage if a smart grid and a comtinent size grid is available.

Adding up the Numbers

The energy consumption in the world in the year 2030 will be around 4,000 GW. To store this energy over one day, we need a 24h storage system with a capacity of 96,000 GWh. Keep in mind, the Gigafactory of Elon Musk may produce 100 GWh per year. If all the storage is used for the global Energiewende, the production for this demand needs about 1000 years.

But be careful, other solutions may be available.  The energy stored in the lakes of Norway contain an astonishing amount of 80,000 GWh, although there is no pump, the stored volume can only be used once in a year and has to be refilled by natural perception.
Pumped hydro technology may be a good solution, especially the Gravity Storage system, a typical site can store about 8 GWh. We still need 10,000 Sites, but tis seems to be more within practical reach, than a bure battery solution.  


References






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11.34

World Energy Congress 2016 in Istanbul


From 9th-13th October 2016, the World Congress on Energy was held in Istanbul. It was the 23rd Congress since 1923.

The topics of the congress were distributed over the entire energy area, including the oil and gas production and renewable energies. There were many important statesmen like Russian President Vladimir Putin and the Turkish President Recep Erdogan, including many other government members from different countries, including the visit of Israeli Energy Minister Yuval Steinitz, the first official meeting after six years frozen relations between Turkey and Israel.
Side by side, Putin and Erdogan at the conference in Istanbul

Vladimir Putin talk was about the importance of energy and the price of oil, a remark about a co-operation with OPEC during the speech has moved the oil price to rise by 2 $! He was the only statesmen, who included the words "exponential growth of solar energy".

The issue of energy just brings together not only scientists and engineers, but also politicians and diplomats. The global linking of energy distribution, especialy natural gas, plays an important role and Turkey was presented as a hub between Asia, Middle East and Europe and the Mediterranean.

The world's energy

All participants have concluded, that the energy transition towards renewable energy, particularly solar and wind, is on the way. However, the completeness and how fast that arives is controversial. While I am convinced that before the end of the next decade the significant change of the energy system has been completed, Marie-Jos� Nadeau, Chair, World Energy Council believes that in 2060 the share of renewable might reach only 50% of total energy production [1] ,
Marie-Jos� Nadeau, Chair, World Energy Council

This is understandable from the perspective of the energy industry. They trade with oil, coal and natural gas. Should the change take place quickly, the oil and the coal is not any longer requested by the market. The industry worries about stranded resources. This means the oil in the ground, on which the wealth of large companies and nations is based, may become worthless.

Key issues in the energy transition in the coming decades

The importance of the Paris Convention for the CO2 reduction was repeatedly stressed. Generally, however, many see only a shift from coal to natural gas, as is well known, natural gas produces half as much CO2 when it is converted into electricity than coal! This is due to a fact that a methane molecule consists of one carbon and four hydrogen atoms, but also to the better efficiency of gas power plants.
Key finding: the phenomenal rise of solar and wind energy will continue!

Power Turntable Turkey

At the conference in Turkey, the geo- (energy-) strategic role of  Turkey was stressed by Erdogan.

Important oil and gas pipelines connect large resources of Asia with European customers, more gas and oil pipelines are planned.
Strategic position of Turkey

Finally, the construction of a new gas pipeline connecting Russian and other Asian gas fields to Europe by crossing Turkey, were one reason why Putin, but also the President of Azerbaijan, Ilham Aliyev, showed up in Istanbul.

The Importance of Hydro-Power

It's a certain irony, the most important renewable energy in the global mix, providing at least 71% of all renewable energy is hydro-power, or 6.8% of global electric energy production, is a often forgotten big player.

The importance of hydro-power may lie in a combination of solar, wind and hydro-power. At the conference solar power as named a water saver, in the form that during the day the turbines are shut down at the dam resulting in increasing water level, during the night, with redoubled turbines, water can be used for power generation. Thus normal dams are important energy storage elements for the energy transition. ot to forget pumped hydro storage or even the new technique of Gravity Storage .
A nice photoshop picture used as advertising billboard in Istanbul

There are, at least in Africa and in South America, still many untapped hydropower "reserves". However, anyone was well aware that each dam has also an enormous impact on nature and very often engages in the habitats of people! Especially in India, the water of the rivers is sacred and thus hardly the construction of dams possible as mentioned by Richard M. Taylorlearned Chief Executive, International Hydropower Association.

Africa to get electricity

While the inhabitants of the Americas and Asia are almost completely supplied with power, in Africa there are still 600 million people without electricity. This means no light, no easy way to charge a mobile phone, no fridge and no welder.

The last day of the conference was therefore devoted to Africa. In Africa, here essentially black sub-Saharan Africa was meant, you have to think about the huge areas and the still sparsely populated countries. This makes the construction of a conventional electric grid network uneconomical and therefore solar energy stand-alone systems and microgrids are very important.
The forum "Talent and Capacity Building" moderated by Samir Ibrahim from Kenya, right Sanjit 'Bunker' Roy from India, next to Andreas Spiess, Solar Kiosk , from Germany.

The practical implementation requires some knowledge of electricity and solar energy. Bunker Roy helps the people with his Barefoot College to teach this to everyone. While he teaches women worldwide (Grandmothers) to practical issues of the use of solar energy, an impressive project!

Andreas Spiess tries with his, as he stressed, commercial solution of the solarkiosk promoting the dissemination of locally adapted use of solar energy in Africa.

The Exibition

There was a international exhibition were companies and countries presented interesting ideas and investment opportunities.
Booth of Heindl Energy GmbH

The Heindl Energy GmbH has presented the "Gravity Storage" technology on its exhibition stand. Unfortunately, very few companies from Europe were represented at the fair. The booth was right next Aramco, the largest oil company in the world from Saudi Arabia. As far as I have observed, our stand had awakened almost more interest.

A 600 MW power plant on the water for emergency cases

There were of course many other interesting exhibition stands, I found the idea of ??"power ship" interesting, which is a ship with a complete power plant (up to 600MW), inclusive substation, which anchors in a port and supports the local power generation, after a natural disaster or for other reasons.

Reference:

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05.36

The Vision of China State Grid

The energy production in the future will be based on wind an solar power. Even in a carbon rich power production country, like China there is no doubt about this long term development.
At the Dii conference 2015 in Dubai, I learned in the presentation given by Han Jun, Senior Vice President, State Grid Company of China, that a global energy grid can solve the problem of intermittent power production.
State Grid China, vision of a global electricity balance

  Is a global grid possible

The idea, to have a global grid is simple, but the physical hurdles are hard to overcome. The best solution would be, we take a high temperature superconductor and span the globe with this type of grid. The only remaining problem is, we don't have the technology, and although "high temperature superconducters" (Working at -130�C not high in everyday experience) have been discovered 1986 by Georg Bednorz and K. Alex M�ller at the IBM laboratory. Till today it was not possible to construct a power line on the base of this very brittle material.

Knowing this, the only path in reality is the use of high voltage direct current connections. And it has been shown by Chinese engineering, that the power connection between the three gorges dam and the 2,600 km distant city of Shanghai works to transport 7.2 GW of electricity.

Knowing this, we can try to calculate the necessary equipment to transport the power of wind and solar energy around the globe by conventional technology. 

How much power?

The first question concerns the amount of power that has to be delivered to far apart regions and continents. Today, a conventional power fleet of 5300 GW produces electricity where the consumers live. In a renewable future, this will still be true in some part for solar and wind, but it might be necessary to transmit 10% over very far distances. This would require a power line, able to transport about 600 GW and with a length of 10,000 km. 

This assumptions are very rough, but it is helpful to start with a plausible range, additional demands are then simple multiplications of the result. If we assume that the power line has a voltage of one million Volts, the current through this line is 600,000 Ampere and we don't want to loose more than 20% of the energy within the line. 

With these assumptions, the resistance of the line has to be in the range of R=U/I = 200kV/600kA = 0,3 Ohm. Knowing this, we can lookup in the table of material properties the necessary material demand. Only cooper and aluminium seem to be sufficient, aluminium is much cheaper, so we take aluminium. The electrical resist of aluminium is 28.2 nO�m. The diameter of the 10,000,000 m wire has therefor 1 m�, quite thick, but able to transport a significant amount of our global electricity demand on a intercontinental distance.
Sources of electricity in the year 2050, estimated by China State Grid.

How expensive is that cable?

To get an idea of the price, we have to know the raw material price of aluminium. At the moment, aluminium sells for 2000 $/t, with limited deviations from that value. Our power line needs 27.000.000 tons of aluminium, because the density is 2700kg/m�. The pricetag is 14 G$, not that bad, if we consider the impact to the global power supply.
A real cable will be at last ten times as expensive as this first assumption, because we have to include an isolation, that can keep one million Volt, but even a price of 140 Billion $ is small compared to the equipment, that is necessary to produce the power.

To produce 600 GW of power, even the cheapest wind power converter at the best suitable places around the arctic circle would cost 600 Billion $.

Impact of a global Grid

A global grid would be a tremendous step to a reliable energy supply. We can compare the solution with the alternative path of large scale storage. The necessary storage for 600 GW over 10 hours needs a capacity of 6000 GWh. This could be done by ultra cheap Lithium Batteries with a price tag of 300$/kWh or 1,800 Billion $ for the required amount. Using the Hydraulic Rock Storage HRS technology, the price could be reduced to 600 G$.

A global grid would use the oceans to wire the continents. The ocean floors are a relatively save place to wire the world, as we already know from the internet fiber optic cables. Another advantage is the international law, the floor of the ocean is not under the same dispute as the land surface and it seems much easier to get a permit to roll out the cables there.

When a country like China takes the lead to interconnect the continents with electric cables, this would change the way, we think about local generation of power. But keep in mind, today, our energy supply system is intercontinental over the ocean, the supertankers distribute comparable amounts of energy over the ocean. 
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01.53

Massive Price Drop in PV Systems

The future will be solar, if the price of photostatic (PV) systems drops. There is a new research result about the future pf the PV price online, done by Fraunhofer ISE [1], that gives surprising insights. I will discuss the results in this blogpost.

Learning from past experience

The first silicon PV cell date back to 1950s and since the 1980s there is a global market and production worth mentioning. Since then, the price of PV cells was constantly dropping. The interesting thing is, there is a mathematical law, that describes this drop. To keep it short, this law tells us, that every time, the production of PV doubled, the price felt about 20%. 

The actual development is shown in the graphic:

Developement of PV module price since 1980 [1]

To understand this plot, be aware, the right axis is the accumulated produced capacity of PW measured in GW. It starts with 0.001 GW (=1 MW) and ends with 100.000 GW. To cover this very wide range, the scale is logarithmic. The first price tag dates back to 1980, were we had to pay more than 20 � per watt. The price is adjusted for inflation to the level of 2014, an exchange rate of  one Euro gives 1.25 $ is in use. The last price tag is for 2014 and is in the range of 0.5 � to 0.7 � for large scale PV power plants. 

Learning Curve

It is not surprising, that the actual price in different years is not always precise on the long term trend curve, that shows a drop of 20,9% per year, due to market effects. 

The big question is, how will this learning curve develop in the future? There are three scenarios, a very conservative one, that tells us, only 19% drop with another doubling of the installed PV base, a medium scenario with 20.9% drop and a progressive one with 23%. However, the result will always be a sharp drop of the PV panel price, if the installed base grows in the future. 

Below a price of 0.2 �/W, there seems to be another limitation by the pure raw material cost. To me�, this limitation seems a little bit artificial, because the price of this raw materials, like silicon or glass, could also drop if the production volume grows far beyond todays volume. 

It should be mentioned, that a capacity of 100.000 GW PV installation is equivalent to a surface of one million square kilometers, this is the size of a country like Egypt or Texas and California combined!

How expensive is electricity in the future?

The price of a PV panel is not the only part of the cost drivers in solar power. To break the price down to a kWh of electricity at the grid feed in, we have to include other cost drivers. 

Price of different elements for real world PV grid-scale sites. [1]

The first surprising thing is, that the PV-modules are no longer the main cost driver, as shown in the figure above. The cost of mounting, connecting and planning top already this cost. The paper from ISE does not cover "Red tape", this will hopefully drop in the future, but nobody knows.

Another significant part of the cost drivers are the inverter, they produce AC current from the DC current, generated by the PV cell. The price of this inverter follows a similar law of price drop by market volume as the PV panels.

Price per kWh

To calculate the price of a kWh of electricity itself, we have to take the solar radiation and the capital cost into account. There is a calculation method, the levelised cost of electricity (LCOE). It includes capital cost and maintenance of the PV power site. If you are a geek, you can do the math with the following formula:

Calculation of the levelised cost of electricity (LCOE). [1]

The interesting result is, that one of the main factors for electricity from PV is not only the sun, but the interest or discount rate. Today, we live in a world with very different interest rates. A strange effect is, if we look at the globe, the countries with high insolation have often very high interest rates. For example, Germany has a low insolation but also a low interest rate, Spain has a relative high insolation but a significant higher interest rate. The result is, the price of PV energy is much more similar as we first guess.


PV power price depends on cost of capital. [1]

Long term development

To look into the future beyond 2020 is very difficult, but the gathered information gives us some hints. The first thing is, PV electricity price will drop due to the learning effect resulting from the growing market. The market is growing, because PV electricity gets cheaper and is competitive to all other electric power sources. The long term price in the scenario of ISE is in the range of  2 ct/kWh. 
The share of the market will be beyond 30% in 2050. 

But there is a obstacle on the path to solar. The sun shines only at daytime and only if there are no clouds. This results in a strong request for energy storage. One solution is the new concept of Hydraulic Rock Storage (HRS) as developed by the Heindl Energy in Germany. 

Energy storage using the Hydraulic Rock Storage. [2]

Combining a cheap storage with a storage price of 3 ct/kWh and PV in the range of 2 ct/kWh gives a long term price for electricity over the whole day, only a fraction is stored, for less than 5 ct/kWh in most regions of the world.

Reference:


[1] Fraunhofer ISE (2015): Current and Future Cost of Photovoltaics. Long-term Scenarios for Market Development, System Prices and LCOE of Utility-Scale PV Systems. Study on behalf of Agora Energiewende. http://www.agora-energiewende.org/service/publications/
[2] Heindl Energy, Hydraulic Rock Storage, http://heindl-energy.com/ 
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05.53
Germany is the country with the largest relative (4%) and absolute (27 GW) share of solar energy in the grid. The reason is not the nice sunny weather in Germany, the reason is a strong subsidies policy called EEG (Renewable Energy Law). It gives the producer of photovoltaic (PV) electricity a good, fixed price over 20 years. Did this really have an impact on the growth of photovoltaic installations?
German was leading the growth rate, now the world has changed!
At the end of the 90s, the growth of PV installations grow with a rate of about 30%. This is quite a lot. With the start of the EEG in 2000, the growth rate in Germany leap jumped to more than 100%. At the same time the rest of the world has even seen a decrease in the growth rate, down to 20%. During the last two years things have changed again. The World, without Germany, has now 2011 a growth rate of 80% in PV installations, while Germany has fallen back to 40%, half of the global speed.

Why this Change?

The reason for this change lays in the price of PV-systems. During the last decade, the price declined from somewhere above 5000 $/kW down to 1000 $/kW due to the strong market in Germany. This low price makes PV economical within most of the sunny countries like Italy or India. Most countries have about double the sun radiation during the year than Germany receives.  
It seems so, that the growth of the solar installations is now market driven and therefore sustainable. But be aware, what 80% growth means, within 11 years, if the trend continues, the world may have changed to a complete solar energy driven world. Today, only 0,4% of the electricity is from solar, but in 2023 it could be near to 100%!



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08.59

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


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