The energy market has drastically changed since Fukushima. Since the ENERGIE – WENDE and with the new awareness of gaining energy from “safe” and alternative energy sources, there has been great innovation. With the excommunication of fossil fuels, opportunities and problems became clearer how systemically renewable energies could contribute to self-sufficient energy supply. The movement led more and more to decentralized energy supply. Once through the departure from Diesel & Co and on the other hand, characterized by the desire to be priced independently of the large power supply. Renewable energies have become a business model. However, even (more or less) unforeseen problems have occurred. As a result of the fluctuations in the supply of energy – wind and sun as the best known example – the challenge with regard to grid stability first appeared. Gas power plants should do that. But increasingly the expensive systems were shut down because the growing range of technologies required the supply of power only a few days a year. Gas power plants, which could close short supply gaps once a month, have become unprofitable. With increasing “energy supply” from renewables – on a windy and sunny Sunday – and also overproduction, the need to save these energy quantities somewhere with as few losses as possible.

In the meantime, it is possible to generate from the generated electricity gas and to feed it into the municipal gas supply network in addition to the conventional storage forms (for example, pumped storage units). If necessary, electricity is generated again, with losses of perhaps 30%. Solar energy can be used to heat technical oils up to 900 ° C and be used directly or indirectly for steam generation. In the meantime, solid fuel storage for heat / cold is on the market or in semi-technical testing. Thousands of patents have been registered since then: supercapacitors as short-term storage, gravitational memory, redox-flow batteries and much more, which is to be discussed in detail in further blogs. All with the goal of ensuring an autonomous and stable power supply. The conditional political will, financial strength, innovation, education and training and “the right motivation”.

The energies of energy have become (almost) self-evident in Germany. On many roofs, we see photovoltaic systems, and large plants are found on quiet areas. These plants alone have an installed capacity of approximately 42 GW in 2016. In comparison, a nuclear power plant has about 2 GW of power and currently (2016) “only” 11.3 GW are still in operation. Even if the expansion of renewable energies can cover this “loss” – in addition to the gradual retreat of energy production from coal and other fossil fuels – the question remains of grid stability and self-sufficiency. For both, you need suitable memories, which are as cheap as possible, can store large amounts of energy quickly and can deliver them again. This affects individual households as well as industry. And all storage systems must have different requirements. For example.

The challenge to new storage systems exists worldwide – the feverish search for them as well. The best-known energy accumulators are first batteries. Also, there are already a variety of variants – from lead-acid batteries to ultra-modern vanadium- or lithium-based accumulators. They differ from their service life (charging cycles) as well as by their weight or volume and not least by the use of toxic or dangerous substances. Lead, vanadium, lithium and acids are used. Not to mention the fact that batteries are highly temperature-dependent or can also explode and burn off.
However, lead batteries can only use about 50% of their installed capacity at low prices, while the

How could a completely self-sustaining power supply system look like? First of all in a German household, a single-family house with a family of four. The demand for energy is about 4,500 kWh / year (costs approx.1.200 € / year). In order to cover this energy requirement, we would need about 6-8 kWp depending on the position and the solar radiation, roof orientation and inclination. This corresponds roughly to an area of ​​60 – 80 m² – as far as possible unshaded. Average prices have dropped from 4,500 € / kWp to 1,400 € / kWp since 2007. For an average of 7kWp, we would therefore have to expect completion costs of 9,800 €. But there is also the cost of energy storage. On average, 12 kWh is required per day. With a 30% “self sufficiency surcharge” and a price of 1,500 € / kWh, we have to be about 24.000 €. So we are, well calculated, about 30 – 35,000 € for a plant. So we need more than 20 years to make the investment pay off.

And now the bad news. There is no real autarky. This is due to the fact that no one is in the house 4 weeks a year. So the public electricity supply should be maintained, the excess sold at a possible small price to the electricity supplier. This is also useful for defects. And of course, this is all mean. But even in July we have an average of 10 regentage. These would have to be bridged and the energy storage must be dimensioned immeasurably. In Germany, self-care rates of 65% are achieved at best. Everything else does not yet cover costs and is uneconomical. And now the good news. With rising electricity prices and an annual degression of storage costs, systems with PV storage systems are now just economical. In 2020, electricity production costs of € 0.24 / kWh can be expected. And perhaps it is also a bit lower. But as this is not yet, there are numerous funding opportunities, cheap loans and tax breaks. This is not the case anywhere in the world, as we have to wait a good while. Large stores are already below 500 € / kWh and there are still some surprises waiting. AMECS has one of them ….

Credit of graphic: © Büro F – Stephan Franz

Next blog: Autarkic energy supply (2) – hugh energy storage for agriculture and industry

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