Sonntag, 8. November 2015

Intercontinental Energy Grid

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, the 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 superconductor" (Working at -130°C not high in everyday experience) have been discovered 1986 by Georg Bednorz and K. Alex Müller 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. 

These 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 lose 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 aluminum seem to be sufficient, aluminum is much cheaper, so we take aluminum. The electrical resistance of aluminum is 28.2 nΩ·m. The diameter of the 10,000,000 m wire has therefor 1 m², quite thick, but able to transport a significant amount of our global electricity demand on an 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 aluminum. At the moment, aluminum sells for 2000 $/t, with limited deviations from that value. Our power line needs 27.000.000 tons of aluminum because the density is 2700kg/m³. The price tag is 14 G$, not that bad if we consider the impact on 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 safe 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 for 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 the 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. 

Freitag, 10. Juli 2015

The End of Fire

The End of the Fire Era

About half a million years ago, mankind started to manage the energy of fire. The first use of open fire was for heat production and cooking. Since three thousand years fire could be kept in a stove to use the energy more efficiently. During the 17 Century, the incredible story of mechanical energy production by the use of fire within steam engines and internal combustion machines began.
This glorious historical period will come to an end, very soon!

What is wrong with fire

There are at least three big problems when we use fire to generate useful energy.
  1. The fuel is expensive and not sustainable
  2. The conversion into useful energy is dirty and has high losses
  3. The atmosphere can't absorb infinite amounts of carbon
All these disadvantages are a good reason to extinguish the fire forever. But is this possible and is this part of a long-term trend?

Have a look at the flames. 

To ignite a fire without tools is one of the most demanding tasks man can solve and only very few of us did this ever complete. On the other side, it is the process that happens more often than any medium scale process we can think about. After some calculation* we find:

 mankind ignites 7 Billion  fires every second 

With other words, for every person on the planet earth, we ignite every second a fire and extinguish it within a fraction of a second again. And none of this fires is seen because it happens within the engines of our cars.
Other fires burn in large power plants and in the heating system of our home, we don't see them even. The fire has lost its visibility. And this might be the first signal, that fire is disappearing.
Another place where flames appeared was the ignition of cigarettes, even this type of fire seems to disappear, no smoking in restaurants, in an office building, in airplanes and only some lost desperadoes at the entrance of some buildings remind us of the old days.

Why fire

All the little and large fires in our engines have only one reason, they should generate mechanical energy and this energy is sometimes converted to electrical energy. This is possible due to the thermodynamic law of physics. But this law tells us, that the efficiency is always low and needs always a cold reservoir like a river or fresh air. This is the reason, that most of the energy is lost in heat, leaving the car through the exhaust pipe or the radiator. The situation in large conventional power plants is similar.
The famous Durango Silverton narrow gauge steam train.
Since Benjamin Franklins work in the 19. Century, we are aware, that electricity is the ultimate useful medium for energy. We can convert electricity in just any service we can imagine. About 60% of the electrical energy ends up in an electric motor to move people, cool air, transport stuff and cut wood.
Not one of this tasks requests a fire, but we had no other solution till now, so we used a fire to solve the problem.

Fire is Unhealthy

There is just no single technology that produces many unhealthy substances as fire. There exist people who inhale the smoke intentional, but most of us try hard to avoid the smoke. We have these smoke detectors on the ceiling and we have different filters in our cars and in coal power plants.
Smoke detector, we try to avoid smoke
When we look to China, a day in Peking is like smoking a packet of cigarettes. But even if we live in modern industrialized countries we have to inhale nanoparticles of all kind due to the burning of gas, oil, and coal. To give an exact value of lost lives due to fire is very difficult, but it surpasses nuclear power by many orders of magnitude.

No fire no harm

If we extinguish all the fires and even the nuclear type of fire that feeds less than three percent of our global energy demand, we can save the planet and the people.
World energy consumption
World energy consumption, only hydro and renewables
don't burn and generate smoke of different kinds. Source Wikimedia

Although it seems impossible to expand the small renewable branch in the picture above, it could get real, because this branch is growing exponential:
growth of PV
The blue dots show the installed PV in the world, the dotted line is a 25% growth
Exponential means, the growth rate is constant and the growth rate of PV is about 25% per year. If this continues for another 15 years, the whole earth can be powered by solar energy. Today we have installed 5000 GW of fire powered power stations, within 20 years we have more than 10000 GW of PV on earth. Read this: Is 100% PV possible?

A second trend is, that electricity is stored in batteries. We are used to mobile phones which need every night a charging. Many of our appliances like screwdriver and toothbrush use batteries.
The next big step is the electric car, the definite way to extinguish the fire. The visionary Elon Musk built a car with batteries from the laptop. Today Tesla sells the Model S at an ever-growing rate.
More batteries will come. As far as I know, no other factory-type expands faster than the battery production plants with the Giga Factory on top. Read also: Storage Maters.
Largest production site ever for a small product! Source TESLA
More than 50 GWh of batteries should leave the Giga Factory every year. But this is not sufficient to meet the demand of 90 000 GWh of storage for a clean future. Complete new technologies like the Hydraulic Rock Storage are invented, which can store many GWh in one site with very low environmental impact.

Will fire stay  

We will never extinguish the fire forever because people like fire.
We love fire

But hidden fire for old machinery invented in the 19. Century will go forever, even hydrogen. It was a fun time of smoking stem engines and high factory chimneys. A world of dark snow in the winter and dirty ash.

Have a clean time.

Samstag, 16. Mai 2015

Is 100% Photovoltaic possible?

The World powered by the Sun

Today, photovoltaic electricity is only a small fraction of the global electricity production. The volume seems to be one percent in the year 2015. If we do a very simple extrapolation and imagine, that all these PV modules were installed in 2014 and we continue this installation speed, then we need another 99 years, to have a 100% emission free PV world. But this is simply not the way the world goes round.
I will try to extrapolate the situation, based on data from the MIT report "The Future of Solar Energy" [1]

Analyse the past of Photovoltaic

If we wont to understand the future, it is very useful, to look into the past, not only to understand the development but also to understand the error which occurred by predicting the future. 
The Energy Information Administration (EIA) and the International Energy Agency (IEA) predict since 10 years the global PV installations in a published outlook. The first outlook from 2006 predicted for the year 2030 a global installation of 100 GW. This volume was already matched in the year 2011, only five years after the report was published! Ok, one wrong shot can be excused.
In the year 2011, the EIA predicted 150 GW until 2020. Again a failure, already in 2014 we have reached 180 GW of solar. 
The MIT analyzed all predictions and compiled them to a very nice picture:
Figure 1: Different predictions and the reality, source MIT [1] page 137
In the early time, the predictions of the IEA had an exponential growth, that is a good guess, because most of the time, new products grow in that type. The only problem was at that time, the growth factor was too small, for example, see IEA 2008 prediction in figure 1. Today things have gone worse with the prediction from the IEA. Not only is the factor to small, the prediction includes a reduction of the production of PV itself. This seems hard to understand. (An in-depth analysis was done by Christian Breyer, paper PDF)
Things got even more strange when we look at the price predictions of PV. The EIA predicted the development of the PV price till the year 2030. It should be mentioned, that it is a very difficult task to predict a price of any product for more than 20 years. But this failure is very illuminating.
Figure 2: Price prediction by EIA IEO 2009 of PV and observed results. [1] page 137
The EIA IEO 2009 outlook predicted, that the capital cost of PV in the year 2030 will drop to 4$/W.
Actually, the price even for residential systems dropped to this value already in the year 2014. It should be noted, that the price for residential PV systems in Germany was at the same time at 2$/W.
The price for utility PV systems reached only two years after the report was published the predicted value for 2030, 4$/W. 
All this information should be available to the EIA today. It irritates me, why the EIA does not change the prediction about the deployment of PV although they can observe the rapid price drop obviously. (I am thankful for any helpful hint)

Is there enough material for a large rollout of PV 

One possible reason, to be pessimistic about the global rollout of PV might be the scare elements used in PV systems. Today almost all PV systems use Silicon to convert sunlight into electricity. The MIT analyzed the production of different raw materials, essential for the production of SI-PV-modules. 
To set up a PV system we need concrete and steel to mount the panel in the direction of the sun. Glass, aluminum and plastic are necessary to protect the silicon cell, copper and more plastic are necessary to transport the power away.
Figure 3: Commodity materials required for PV. [1] page 131
Today, all these commodities are produced in a volume, that no real bottleneck will occur. In figure 3, we can see, that the steel production of 9 days is sufficient, to mount all PV panels for 5% of the global electricity production, within half a year, the steel production is sufficient for a 100% conversion to PV.
The least available material in this consideration is glass. For a 100% PV world, we need the glass production of 20 years. But glass production is in no way a limiting factor. The necessary raw material is sand, an endless resource.
The solar cell itself consists of a silicon wafer and some silver, are they rare?
Figure 4: The annual production and requirement for a solar future. [1] page 135
In figure 4 we see, that silver might get a little problem because we need an amount of silver that is produced within 30 years. It should be mentioned that new technologies of production can reduce the necessary mass of silver very strong. Other elements, like Ga, are only necessary if we would use GsAs cells in our PV systems what is not widely the case. 
We conclude the raw material is no show stopper for a PV future.

My prediction of PV growth

Compiling all this information, I come to a quite different prediction than the IEA. My simple, but till today best guess is, that the exponential growth will continue, but at a lower rate. 
Figure 5: Long-term trend of PV installation.
In figure 5 we see the global installation of PV shown as a black curve in this logarithmic plot. In the year 1992, we had only 100 MW of PV installed, ten years later, in 2002 it was 1000 MW, Today it is about 200 000 MW!
Update to Figure 5 including the growing power demand, wind, and the latest figures available 2016.
If the growth rate continues at 25%, as seen within the last three years, we will reach 100% PV not long after the year 2030. Remember, today we have a global power plant pool of 5300 000 MW, sufficient to power half the world. Even if we expect, that the future is fair to all people, we need "only" 10 000 000 MW to bring electricity in every home on this planet, long before 2050.  

One problem remains: Storage

Without an affordable storage system, PV can only bring electricity during sunny daytime. For a complete conversion, we need about 90 000 GWh of storage [2].
One solution for residential systems may be the power wall from Tesla, but I am not convinced, that this makes sense on a large scale. For large scale, I recommend the Gravity Storage!


[1] The Future of Solar Energy, 2015 Massachusetts Institute of Technology, ISBN (978-0-928008-9-8)
[2] Elon Musk predicts (minute 18) during the presentation of the power wall 90 000 GWh of required storage.

Samstag, 28. Februar 2015

PV Price in the Future

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 of the PV price online, done by Fraunhofer ISE [1], that gives surprising insights. I will discuss the results in this blog post.

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 fell about 20%. 

The actual development is shown in the graphic:

Development 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, where 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 of the pure raw material cost. To me´, this limitation seems a little bit artificial, because of the price of this raw materials, like silicon or glass, could also drop if the production volume grows far beyond today's 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 levelized 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 levelized 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 significantly higher interest rate. The result is, the price of PV energy is much more similar as we first guess.

PV power price depends on the 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 with 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 an 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.


[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.
[2] Heindl Energy, Hydraulic Rock Storage,