Halloween party ideas 2015
Tampilkan postingan dengan label desert. Tampilkan semua postingan
Tweet Share Share Share Share Share

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
Baca selengkapnya »
Tweet Share Share Share Share Share

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. 
Baca selengkapnya »
Langganan: Postingan (Atom)
Diberdayakan oleh Blogger.