The future of the power supply will be DC
13 June, 2018 by
The future of the power supply will be DC
CMC Klebetechnik GmbH

A provocative and still visionary statement - at the beginning of 2018. But the first steps in this direction have already been taken several years ago.

A provocative and still visionary statement - at the beginning of 2018. But the first steps in this direction have already been taken several years ago. And those benefits are slowly spurring the restrained market participants.

The electrical energy supply system is historically divided into central energy suppliers and decentralized consumers. Power from a high voltage level is hierarchically provided via high-voltage roads throughout Germany and Europe, to be distributed over a medium-voltage rail until the usual 230VAC / 400VAC voltage levels reach the consumer.

Renewable energy producers such as water, wind, solar energy and biomass change this traditional network structure. More and more decentralized input entries burden the distribution network much higher than ever before (in 2016, the amount of renewable energies in the electricity mix was 31.7%).

In order to ensure high availability in such a heterogeneous environment and to be prepared for future requirements (e-mobility, for example), new, intelligent solutions are needed.

As the term "Industry 4.0" describes a change towards a continuous digitalization of the manufacturing process in the industry, the term "Smart Grid" stands for an intelligent, networked cooperation of as many energy producers, consumers and storage units as possible.

To avoid a dependency on coal and oil to provide the so-called base load supply in the long term, the intelligent network needs new approaches in terms of ensuring network quality. Because the classical sources of regenerative energy are wind power and solar energy – and both techniques are not baseload capable. Especially the changes in the contribution to power generation, which are hardly predictable due to the weather, must therefore be intercepted in other ways.

Various committees - inter alia the VDE, ZVEI, VDMA, NPE, IEC as well as national political level, are working on solutions to this fundamental problem.

And there are now (in the meantime) first partial solutions that can even bring different industries together:

Solution approach 1:

Lithium-ion batteries have been on the market for over three decades now. The production is still complex, but a completely controlled process.

This battery type represents currently the optimal combination of capacity / volume. The developments in electric mobility and in the self-supply of houses by solar power have made a significant contribution for making battery modules more and more affordable. Extremely dramatic is the drop in prices over the last 5 years, in which the cell prices got double digit cheaper every year.

By now there are several megawatt power plants based on lithium-ion battery technology in Germany (e.g. in Chemnitz 10 MW, Schwerin 10 MW, Duisburg 30 MW), which are used by the energy suppliers to improve the network quality (primary control power) and to be able to take action in case of need (e.g. peak power demand).

With the increasing networking, started by decentralized energy storage systems (lithium-ion batteries in solar systems), smart electricity meters, uninterruptible power supplies, up to megawatt storage and e-mobility, a completely new network topography will emerge. Additional e-mobility batteries can store and release energy for years in their "second life", so that the valuable resources for producing the LION batteries can be effectively protected (example: Nissan Leaf batteries in the Amsterdam Arena).

The contribution of CMC Klebetechnik:

All of these components require electrical insulation and thermal management measures, which can be archieved with films, adhesive tapes and stamped parts by CMC Klebetechnik.

CMC Klebetechnik works closely with several battery manufacturers, which use the expertise of the company and the variety of available films and tapes. The keywords therefore are "isolate, protect, dissipate heat, mark, bundle, fire protection or heat". Particularly in case of aged cells and increasing charging powers, passive protection systems will become more important.

Thermal Runaway or also the simple increase in cooling demand because of the higher internal resistance are important keywords.

Solution approach 2:

Due to the fluctuating provision of electricity through renewable energies (geothermal energy will not play a role in Germany although it would baseload capable), the electrical generated energy must somehow be stored.

- Solutions such as storage hydropower plants fail in densely populated Germany because of the high admission restrictions.

- Compressed air storage in abandoned mines can lead to ground subsidence.

- Flywheel mass storage systems are unsuitable for large energy quantities.

One of the most promising approaches is the conversion of electrical into chemical energy (power-to-gas, powert-to-chemicals), into oxygen and hydrogen to be exact. Hydrogen can be added to natural gas. Thereby it is available in the extensive and well-developed gas distribution network with an enormous storage capacity.

Of course, the transformation from electrical to chemical and finally back to electrical has a very high loss factor. But this storage and recovery process makes an invaluable environmental contribution by conserving the finite resources of the primary energy sources like coal, oil and gas and makes an important contribution for the decrease of the raising global warming.

The contribution of CMC Klebetechnik

Several companies are working on the process of electrolysis and catalysis to improve and optimize it. Even in this environment, CMC Klebetechnik offers films and adhesive tapes that can be used in the core components, the so-called "stack" (stack of individual fuel cells).

In particular, the so-called proton-electron exchange membrane (PEM) technology is capable of converting highly efficient chemically stored energy back into electricity with little effort in terms of the process technology (operation at a maximum of about 100 ° C).

CMC Klebetechnik provides therefore hydrolysis-resistant, low-shrink and chemically neutral adhesive tapes that are used in the immediate vicinity of the MEA (Membrane Electrode Assembly). They do not affect the functionality of the exchange membrane and withstand the high hydrolysis load very well, which leads to degradation of the polymer matrix in many other plastics.

A considerable number of PEM fuel cells already demonstrate the functionality of the adhesive films from CMC Klebetechnik even in long-term operation.

The future role of DC voltage in the energy supply:

Both suggested solutions have one important thing in common: they are based on DC voltage. More than 100 years after the "victory" of Tesla's AC over DC, a new era is beginning.

In many devices the currently available AC current is converted back into DC at the end and this is linked with significant energy losses.

To be able to feed the direct current, produced by fuel cells, megawatt LION stores or solar plants, into the current AC grid, a DC / AC transformation is required. In the devices, which are very often operated with direct current (LED lighting, battery storage systems, electronic devices), the AC voltage is rectified again (AC / DC converter). There are also significant energy losses.

Energy sources such as small hydropower plants and wind turbines also convert the produced AC voltage into DC voltage in a DC link. The DC voltage is usually converted by the pulse width modulation method (PWM) - again with energy losses - into a line-compatible AC voltage.

In many devices, the power conversion losses account for 40-80% of the total power and are accountable for up to 50% of the manufacturing cost.

All of these transformer losses (DC-AC-DC) can be reduced by a Low Voltage Direct Current (LVDC) network below the large distribution AC-grid.

Households, industrial companies, municipalities and large institutions such as congress halls and hotels consume a large proportion of the electrical energy in the form of DC voltage (e.g. hall lighting). In these cases, converter losses can be significantly reduced, if the electrical energy from DC sources can be used without the detour via the AC grids.

A DC network, which integrates many different voltage sources, also helps to reduce the significant over-dimensioning of traditional power grids where a few large power plants have to provide each other with the lack of capacity in case of a failure. In future there will be a distribution of such a load to many sources. Additionally DC voltage can reduce reactive power losses in alternating current networks, and this in turn, reduces the network load. DC also requires a smaller cable diameter by having the same current, existing lines can still be used in the LVDC network unchanged.

Standardization as a guarantee for success:

The German Institute for Standardization (DIN), the German Commission for Electrical Engineering (DKE), the European Standardization Organization CEN and CENELEC and the International Standardization Organizations such as ISO and IEC are - together with research institutes and the relevant industry (EV automobiles, solar plants, energy suppliers) - intensively developing standards to pave the way to success for such an LVDC Grid. Because the number of DC power sources and DC consumers will explode in the upcoming years.

Especially the integration of electric vehicles (48VDC ... .900VDC) in the smart home infrastructure extends the future possibilities of energy storage. Standardized networking of the information and communication networks (IKT) inside and outside the home network is a prerequisite for a successful integration. An example for the need of standardization is the still very large inconsistency of the payment systems at e-mobile charging stations. Who drives further routes, should have payment cards of several providers.

The contribution of CMC Klebetechnik :

For the necessary standardization, which is essential for cross-border and continental distribution systems, CMC Klebetechnik participates in various standardization bodies.

CMC Klebetechnik products are already being used in smart meters, battery storage, AC / DC converters, DC / DC converters (Flux converter, resonant converter or fly back converter) and frequency converters. They significantly isolate, connect, protect and improve the longevity of electrical and electronic components.

Especially Power electronics technology will become a key technology for the energy transition. Higher switching frequencies, higher voltage levels, cheaper components and increasing miniaturization allow higher energy density by decreasing (falling) prices at the same time (EV inverter 1995: approx. 80 € / kVA, 2020: approx. 4 € / kVA). To achieve a greater acceptance of e-mobility, it requires the High Power Charging technology, which means short charging times with enormous amounts of energy (up to 1 MW for 5 minutes charging time for 400 km range). A DC network avoids converter losses in the OBC (on-board charging system), which are unavoidable during the AC supply.

Take advantage of the competence and quality of a leading manufacturer of special adhesive tapes in Germany. CMC Klebetechnik provides solutions based on joint developments of adhesive films made out of various materials and contributes to the optimization of future DC technology in the "exciting" market as a replacement for expensive AC-DC or AC-DC-AC conversion technology.

The future of the power supply will be DC
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