Wind Energy in Germany

Here are some brief considerations about the performance of German wind energy facilities. Over the past two decades the number of wind turbines installed in Germany has increased dramatically. The surge in capacity amounted to 350 % between 2000 and 2010. The growing capacity lead in turn to a growing production of electricity, 300 % up over the same period.

One question of particular interest to us was how much energy one might expect to be generated per MW installed on average. As the production of this kind of energy is highly sensitive to the availability of wind we were seeking for a model which is able to reflect the variations of the latter. The source data for our investigation were taken from both Eurostat and Bundesverband WindEnergie, the German association of wind energy producers.

We started by looking at the amount of energy produced per installed capacity (Prod/cap) measured in MWh/MW between 2001 and 2010. We may call this quantity the specific production. The result is the blue curve in the figure below showing a clearly increasing trend. It must be noted here that this graph needs to be interpreted with special care, since it is distorted by two major sources of uncertainty. The first source is the varying wind availability. The second source of uncertainty is based on the fact that the number of wind mills is constantly growing over the year as more and more turbines are constructed. The total installed capacity may go up by some 30 % and more during the course of a year. Some of the newly built turbines may take up operation in spring and others may be commissioned towards the end of the year. In each case their contribution to the entire production will be very different. Thus our model has to account for the extra capacity erected during one particular year.

Another factor coming into play is the location of the turbines. Although each of them is supposedly optimized in terms of output, there may be significant differences between various wind farms. However, as more and more turbines come into existence, the influence of individual outliers should diminish compared to the total average. We always have the big picture in mind, thus neglecting the performance of particular locations.

In theory, the specific production should exactly correspond to the amount of wind available. The latter quantitiy is represented by the red curve as a percentage over the long-term average (r.h.s. scale). As can be seen, the variations may be tremendous.

Production of wind energy in MWh/MW(installed) and comparision with wind availability.

We note that the red and the blue curve do not coincide as expected. This lack of coincidence is mainly caused by the addition of extra capacity which, in relative terms, was very large during the first part of the period in question (44 % and 37 % in 2001 and 2002, respectively, compared to the previous year).

In order to find a better agreement between the wind availablity curve and the specific production we developed a statistical model which enabled us to eliminate the distortions caused by the newly built wind mills. The result of our model calculations is shown in the green curve which nicely matches with the availability curve (red). What we got is a new quantity Prod/cap* which allows us to draw meaningful conclusions about the mean productivity of each MW of installed capacity.

Depending on the availability of wind Prod/cap* may vary considerably. At a value of 100 % availability each MW installed should produce slightly more than 1700 MWh annually. During our reference period Prod/cap* varied between a maximum of 1800 MWh and a minimum of 1250 MWh. This is a massive variation which must be taken into account when considering the energy supply stemming from wind farms.

Solar PV in Sweden – The SHEAB Project

Below is a report about the SHEAB project which is designated to harvesting solar PV in central Sweden.

The SHEAB Project

by Hans Nyhlén

In two small municipalities, Sala and Heby, located north of Västerås and West of Uppsala, is the home for Swedens first and only (?) multiple-owned economic association investing in Solar PV.

It all started in 2008, when the municipality-owned energy company Sala-Heby Energi AB (SHE) wanted, as the first energy supplier in Sweden, to offer its customers to trade with electricity from the sun. A number of options were presented to SHE´s customers in the autumn of 2008 and a specific offer was made. Solel i Sala och Heby Ekonomisk förening was then formed in the spring of 2009 as a result of this work. The first co-owned photovoltaic facility was built in Sala in September 2009 and since then, a new PV plant has been built every year. During this short period of time the specific investment cost of turnkey solar PV plants has fallen by more than 70 %!

Today the co-owned economic association has nearly 200 members, mostly private persons but also a handful of companies. The total installed PV capacity is 200 kWp, giving approximately 180 000 kWh annually. These figures are growing though, since more members are joining and some old members buy more shares. During the first five years, the association has decided to use all its incomes and membership fees to build up a palette of Solar PV plants. Thereafter, the electricity production from the PV plants will give members cheap electricity for a long time, combined with continued commissioning of new solar PV plants.

The formation of Solel i Sala and Heby ekonomisk förening shows that it is possible to take advantage of a local interest, from both private persons and companies, in solar electricity and turn it into construction of large photovoltaic systems. It also shows that it can be done in a relatively short time.

A sustainable city needs to be smart

A sustainable city needs to be SMART.

In order to reach sustainability, SPECIFIC targets need to be set and met: e.g. reaching climate neutrality within a certain time frame. Those targets need to be MEASURABLE. It is not enough to just talk about sustainability and a transition. It is very important that the targets can be quantified and that results are shown. Reaching sustainability demands a lot of effort. Therefore it is important to make a time-plan and split up the final target into small steps that can be reached more easily and which can be measured. This introduces the 3rd aspect, i.e. targets need to be ATTAINABLE. When dividing the final target into smaller steps, results of the measures taken become visible one by one. It is also important to involve local stakeholders, e.g. inhabitants, local companies, governments, etc. Each step in the plan towards final sustainability can be celebrated, giving a boost to the people involved, showing that their actions result in something positive on the way to the final target. The measures need to be REALISTIC. It is good to dream about sustainability and about the transition to a sustainable city, but it will be reached by taking one step at the time. When going too quickly, without a plan to follow, problems can be created and it may become difficult to reach the final target. The approach needs to be TIMELY. It is important to develop a good plan towards a sustainable city. This means going step by step, and choosing which step/measure to take at which moment in a smart and innovative way. Thus, use what is available at a certain time and apply this measure to the best knowledge. Furthermore, try to find ways to improve these measures to bring cities to a next, sustainable level.

There are many examples and I will name a few. On the island of Samsoe in Denmark, they reached energy neutrality in 2005 (started in 1997). Some general facts: surface is about 110 km², and about 4000 inhabitants. The energy system of the island is based on wind and solar energy for electricity, biomass (straw and wood chips) and solar energy for heat and measures are taken for the fossil fuel use of the ferries and cars on the island. Güssing, Austria, is a nice example of how a complete village and region can transition from a fossil fuel based system with high costs to a system based on renewables, keeping more of the money in the region. General facts: surface is about 50 km², and about 3700 inhabitants (region 27000). They started in 1992 with the transition. Güssing has reached a 71% self-sufficiency in 2010 (100% if industry is not taken into account) and they are working on also reaching energy autarky within the Güssing-region. The energy system is based on local available biomass (wood, grass, rapeseed), via a CHP-plant and district heating, and solar energy. I will name one other example: the work that is done in the city of Wageningen in The Netherlands to transition to a climate neutral city by 2030. Wageningen has about 36000 inhabitants on about 32 km². In this initiative the municipality involves also local stakeholders like inhabitants and companies. The targets are: 25% local renewable production, 50% energy saving, and 25% import of renewable energy. Many more examples can be mentioned.

Furthermore, a SMART sustainable city needs to include the following aspects:

A sustainable city needs to be SUSTAINABLE. When taking a measure, this has to be done in a considered, clever way. A measure has to be ecological, economical and socio-cultural. This means keeping in mind also the future perspective: think about here and there, current and future generations (UN-Brundtland commission 1987, definition Sustainable Development). A sustainable city needs to be MULTI-functional/disciplinary. It is important to use the mixture of functions to find the most efficient and effective solutions for problems in the city. The multi-functionality needs to be seen as an opportunity and not as a problem. Another important aspect is AFFLUENCE. This means that people need to be able to live good and in the way they want, but they have to be aware of the consequences of their actions. A sustainable city has to inform its inhabitants about smarter ways to reach their targets, better for both the environment and the city. Those measures have to improve the quality of life in the city. A sustainable city needs to be RENEWABLE. This is/seems logic, meaning that the use of resources should be renewable. The measures taken need to be renewable or from residual origin. It is important to divert away from the old way of thinking: it is not possible anymore to use fossil fuels/resources as we currently do and think that we can compensate for the emissions and other negative effects. A last aspect for a sustainable city is the TECHNOLOGICAL one. This implies using the available knowledge and not always throw it away immediately because it seems not worthwhile or too expensive. Those new methodologies/measures need to be given time to develop. The technologies for fossil fuel use did not come out of the blue either and needed a lot of support as well.

The following figures show results of a study applied to a municipality in the south of The Netherlands, Kerkrade.

Fig. 1: Energy demand for different urban functions

Fig. 2: Energy supply potential for the studied district (solar: PV/solar boilers; hydrogen production demands electricity which is supplied by extra wind turbines).

The results are based on research described by the author in a published paper. Available by author on request. Reports on Samsoe, Güssing or Wageningen on which results are based, on request by author.

Wouter Leduc

How Much Energy Do We Actually Need?

This posting is rather philosophical than technical. Whenever we talk about energy, we tend to think in terms of oil, gas, nuclear, electricity, and the like. But throughout the longest part of its history mankind has been living without any of these “modern” energy types. And yet, throughout its entire history humanity has been dependent on energy, even without knowing it to the degree we are aware of it.

Why is that so? Every living being needs energy, just to stay alive. From a very basic point of view, what you essentially need to keep yourself alive is food, the nutritional value of which is measured in kcal which, in turn, is a measure for energy.  So we have to supply our body with energy if we want to stay on this planet.

The basic energy need of a human being is about 2000 kcal per day. This is an average value which may vary according to age, sex, physical activity etc. Our basic value is meant to be valid for no or little physical activity. Thus, for people who are physically active it may be significantly higher (30 – 50 % or more). Since in the energy business it is rather uncommon to use kcal as a unit we may remark here that the above-mentioned 2000 kcal are equivalent to 2.33 kWh. From this we may calculate that the annual energy needs of a human being are about 1 MWh, taking into account a slight level of physical activity.

However, even for a society where technology has not yet developed to the level we are used to, the energy requirement per capita may well exceed 1 MWh per year. For the sake of simplicity let us consider a human being living in the Middle Ages. This means that the technological standard of that society is still much lower than nowadays, whereas at the same time its living standard is much more sophisticated than the one of, say, a society of Stone Age people.

In the Middle Ages, the vast majority of people were living an agricultural life. Thus, their energy needs reflected their living conditions. The technology of that time made extensive use of animals which was essential in order to produce a sufficient amount of food. Needless to say that the animals themselves had to be fed, too, and were thus energy consumers. The most important labour animals in such a society are horses and cows (oxen). Since they are, in general, bigger and doing much more labour than the humans, they also require more energy. Let us assume that, on average, we have one cow or horse per human being. A horse requires about 12000 kcal (14 kWh) per day, and the same is true for a cow (ox). This corresponds to about six times the energy requirements of a human. A largely inactive horse will need some 5 MWh per year. In case the animal is used for labour purposes this value will increase dramatically.

In our simple model, the minimum energy needs of a human being (plus his/her labour animal) may be estimated to about 6 MWh per year. In practice, this value might be considerably higher (30 % or more). Life was not easy then and certainly more physically demanding than in our times.

What we have considered so far was a very basic life mostly devoted to producing food and satisfying the elementary needs only. In some parts of the world, however, an additional factor comes into play: heating. Especially during the winter and the colder seasons, people need to keep a certain temperature for survival. In order to get an idea how much energy we need for heating purposes we may take the corresponding value from Switzerland which is about 6.5 MWh per person and year. This is a modern value. Linking it to a society several centuries back we have to take into consideration that on the one hand people living centuries ago might have been happy at a lower average temperature than today. On the other hand, however, we may also consider that then heating was not as efficient as it is in our times. Thus, taking the present day values may be a justified approach as the correcting factors go into opposite directions and may cancel each other.

Putting everything together leaves us with an energy need of about 13 MWh per person and year in an environment with present day climatic conditions in central Europe. One should not forget that all those basic energy needs (with the notable exception of heating) may be coverd by solar energy. In our model society it´s the sun which makes the crops grow which, in turn, serve as essential food for both humans and animals.

It goes without saying that the average energy requirements per person will increase with technological progress. Not only do we produce a number of goods nowadays which simply were not existing in the distant past, but we also enjoy a higher level of mobility. Thus both the production of goods other than the ones needed for satisfying elementary surviving conditions and mobility lead to additional energy requirements.

The above considerations are far from being simply of an academic nature. We may compare our estimates with present day statistical data. Let us look at some countries with different economic development. Taking the UN figures for energy per capita from 2008 reveals the following (GDI = gross domestic income per person):

Zambia    6.9 MWh   (GDI: 950 USD)

Zimbabwe 8.9 MWh   (360 USD)

Paraguay   8.1 MWh   (2110 USD)

Mongolia   13.7 MWh  (1670  USD)

Romania   21.3 MWh   (8280 USD)

Uzbekistan   21.5 MWh   (910 USD)

UK     39.5  MWh  (46040 USD)

US   87.3 MWh   (47930  USD)

There is a clear correlation between the level of industrialization and energy consumption. In addition, there is a climatic factor which must not be neglected. As we climb up the economic ladder we require more and more extra energy.

However, by using energy in a smart and efficient way we may limit the extra requirements. The average energy consumption per capita in the UK corresponds roughly to the EU value (40.8 MWh). Whereas the GDI of a US citizen is only slightly higher than the one of a UK citizen, his/her energy consumption exceeds the one of a person living in UK more than twofold. Thus, energy efficiency in the US is only half as good as it is in the UK.

Where are the limits? On the one hand we have to live with the fact that getting wealthier comes at a price in terms of energy consumption, on the other hand we want to squeeze as much wealth as we can from every MWh. As I have discussed in some of my previous posts (here, here and here) there is a clear tendency to become more energy efficient. Extrapolating those tendencies may give us a clue where we are heading to.