Mittwoch, 20. Dezember 2017

The demand for pumped storage facilities in central Europe

The demand for pumped storage facilities in central Europe 

IIn the year 2017 I was at two pump storage plant meetings,"Pumpspeicherwerke" in Essen on July 10,2017 and on November 29/30 at the 3rd International Pump Storage Conference in Salzburg, the results are somewhat contradictory and I want to discuss them in this blog post.

(This article about pumped storage was first posted in German language and was translated with the help of deepl.com)

International distribution of pumped storage power plants.

Pumped storage in Germany

The German pumped storage facilities have a capacity of 40 gigawatt-hours and a connected load of 6 GB,  these are enormous figures but in relation to the electricity system they are rather small, the power capacity is about one-tenth of the German electricity consumption and the energy capacity could supply Germany with electricity for less than an hour (if the power capacity were sufficient).

The task of the pumped storage plants in their original function, however, was not to supply Germany with electricity overnight if the sun doesn't shine, but to manage failures of nuclear power plants or to cover peak loads during the lunchtime period, which were caused by switching on many electric cookers in earlier days.

Rene Kühne on the development of the spot price, the peak at noon has disappeared. (Slides)

Today the picture has changed massively. During the day, the high number of photovoltaic systems, with around 40 GB of installed capacity in Germany, makes a significant contribution to the reduction of electricity demand peaks. Although not always, especially in the winter when it is very cloudy and only a few hundred megawatts are generated by photovoltaics. As a result, the price of electricity no longer fluctuates as much as in the past, which is precisely why pumped storage operators have a major problem financing their systems.

It is now the case that even finished plants can hardly generate the revenues to maintain operation. At the meeting in Essen, for example, some spokespersons stated that in the event of a major overhaul, such as the replacement of a turbine, the power plant would actually have to be shut down for economic reasons.

This would, of course, have considerable consequences for the electricity grid, because the pumped storage facilities are also used to stabilize the grid and are supposed to buffer solar and wind power in the future in order to provide the corresponding energy at other times of demand.

A new building is therefore practically unthinkable in Germany, which also meant that the well-known Atdorf project in the southern Black Forest was stopped, although 60 million euros have already been spent on planning.


Expansion of the pumped storage power plants has almost come to a standstill, shown as yellow circles, Reinhard Fritzer, ILF (Slides)

Pumpspeicher in ÖsterreichPumped storage in Austria

The situation is different in Austria, where there are considerably more pumped storage power plants, especially in terms of storage capacity. This comes from the large slopes in the Alps around the much larger dams and thus reservoirs.

Professor Helmut Jaberg's famous plant of the Illwerke was presented at the International Pumped Storage Storage Conference in Salzburg. A pumped storage tank with a drop height of more than 800 m and over one gigawatt of power.


The ratio of stored energy to turbine power is larger in Austria and Switzerland, which means that its energy can be stored for longer periods.
Due to the large storage energy capacity, surpluses such as those from longer periods of strong wind can also be absorbed if the lines are sufficient. In times of calm, the energy can then be called off and sold at higher prices.

This is often misleadingly portrayed in the media as if Germany is giving electricity away abroad and reimporting it at great expense. No, there is a service in between that the energy is stored and delivered exactly when we need it!

Storage revenue sources

The very flat price curve for electricity cannot currently finance storage facilities, but there are other sources of revenue for storage facilities, such as balancing the grid. Energy is provided or absorbed at short notice to stabilize the grid.

Control energy is another source of revenue for pumped storage.

In the lecture of the consulting firm BET from Aachen, additional sources of income were presented.

The problem, however, is often the legal regulations, which make it very difficult to treat all markets fairly. This often shows that our energy laws are still too much dominated by the way of thinking in the old energy system. In addition, the transport of energy is not shown, all prices are valid for Germany, although there may be a surplus in Northern Germany and a shortage of electricity in Southern Germany.

The load gradients have been growing in recent years, so fast control power is required.
An alternative to storage is the expansion of the grid, but unfortunately, this is progressing very slowly, so that in the long term a lot of energy coming from wind and sun does not reach the consumer.
Network expansion, only 3% are completed in 2016, Slide Team Consult.

Conclusion

Considering pumped storage alone in a power system does not make sense. In the future, all components of a modern power grid will have to work together. Wind, offshore and onshore, PV, power lines, storage facilities in Germany but also across the border and with fair rules for everyone involved.


Dienstag, 4. April 2017

How much land area does a 100% solar powered world need?

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; the 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 m² or 15,000 km².
Now the efficiency comes into play since only 20% is converted into electricity, we need the fivefold area, that is 75,000 km². 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 km².
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 km².

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 afterward 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