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You say you have changed your mind about solar energy. Can you tell us more about why and how? I would be interested.

Thank you and happy new year!
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@Epi With pleasure. It was built on an old, reclaimed open-cast mining area. In my opinion, such plants are perhaps still justifiable here, as land is used on which the agricultural produce was probably used for the biogas plant rather than for food production. (In some cases, the topsoil/humus layer here is not even 20 cm).

The aim was to achieve a total output of X on a total area of over 500 hectares.

The area used would not even replace half of a modern coal-fired power plant located nearby.

An area of around 1,300 hectares of land would be needed to replace the coal-fired power plant in the region, at least as far as electricity generation is concerned, and that's not even taking district heating into account. And that is a favorable calculation.

The solar modules from $JKS, which come from China, are also not of very high quality. The bonding on almost every module has weak points such as air pockets. The cold-heat cycle will reduce the service life here. From -20°C to +35°C (plus heat on the solar module, another 30°C) we also have some of the greatest temperature fluctuations in our latitudes, which always makes structural tasks more difficult anyway. So this is also a huge weak point for poorly processed solar modules.

A service life of more than 30 years was desired for this project so that profits could be generated in the end, but I am not the only one who considers this to be unrealistic due to the circumstances. In addition, there are other location factors and environmental influences such as weather (hail, ice, snow) as well as wild animals and birds as risk factors that can influence the performance and service life of the system. Summarized as briefly and concisely as possible without going into too much detail. 😄
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@MontyMaulwurf I also wanted to ask this question and thank you for the explanation. Interesting in view of the fact that I might want to work in the solar/wind sector again this year.
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@MontyMaulwurf Interesting! Would you say that these are all feasible hurdles or are they all fundamentally against solar power in Germany?
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@Epi Based on the experience I have gained, I think the hurdles are too high.

Better processed modules cost more money, but do not offer more performance at the same time.
Of course, this also reduces the return on investment.

In addition, the construction and maintenance costs here in Germany / Central Europe are naturally much higher. A costly part is still the workforce, which cannot be replaced. There are already very sophisticated mounting systems that can be used to mount a large number of solar modules in a short space of time (and change them if necessary), so I don't see any great development progress in terms of saving costs here either.

What's more, companies from abroad are already being brought in for this purpose, as German companies are a few euros more expensive - the shortage of skilled workers and human resources is also a cost-intensive issue here. The minimum construction wage is also certainly a cost-driving factor in relation to Germany as a business location.

How worthwhile a system is in the end, I think can ultimately be summarized in 4 major factors

1. construction costs and maintenance
(Germany is a very cost-intensive location)

2. output of the solar modules
Currently, approx. 575 watts per module are suitable for such projects in terms of cost-benefit factor and size/dimensions. As far as I know, there are already modules up to 800 watts, but these have larger dimensions to achieve this output and are also more cost-intensive. Here you would have to consider the watts per area and adapt the mounting systems to the structural design.

3. service life of the solar modules
An increase in quality is equivalent to an increase in costs. In addition, solar modules lose power over time, which is why they become increasingly uneconomical at some point and then have to be replaced. After 20 years, the output should still be approx. 80-85% of the nominal output, and the modules should last at least 30 years. With the quality of workmanship and the Central European climate conditions due to temperature fluctuations, this is certainly a challenge. The power loss is much more significant in an industrial system than in a private PV system for a residential unit, as many more solar modules are connected together. As solar modules are connected in series per inverter, all solar modules feed in the same power.
Simply put, this means as an example: I have 130 solar modules per inverter. These should generate a nominal output of 600 watts. If even just 1 module generates only 580 watts, this 'throttles' the other 129 modules down to an output of 580 watts / module, so I have a real loss of nominal output.

4. weather

Nobody can influence anything here. If you have fewer hours of sunshine per year than you originally calculated, the system naturally generates less. Especially in the first few years, when the modules are still at full capacity, this can have a massive impact on the yield.