Fraunhofer Institute for Solar Energy Systems ISE
Fraunhofer Institute for Solar Energy Systems ISE

Medium Voltage – A Resource-Efficient Way to Interconnect

CO2 emissions must be significantly reduced by 2050. To achieve this, the electricity, heating and mobility sectors will be electrified, with the electricity grid becoming the hub for sector coupling. A reliable and cost-effective energy supply is essential.

Using today’s technology, large amounts of raw materials will be required to connect the different areas of energy provision, storage, distribution and utilization. Medium voltage technology, however, is the key to open up the resource-efficient integration of renewables in the energy system. The higher system voltages offered in the medium-voltage range enable considerable material, cost and space savings. This technology also allows new system concepts for renewable hybrid power plants whose individual components are interconnected via medium voltage.

Medium Voltage – A Resource-Efficient Way to Interconnect
Energy Provision Energy Storage Energienutzung Energy Distribution Hybrid Power Plants Hybrid Power Plants
© Fraunhofer ISE

Where will Medium Voltage be Implemented in the Future for Resource-Efficient Interconnections?

The fields of application are diverse and can be divided into the areas of energy provision, storage, distribution and utilization. These individual segments can be used as connective elements to build regenerative hybrid power plants interconnected via the medium-voltage grid, which offers various advantages from a system perspective.

Areas of Application "Medium Voltage"

Energy Provision
Energy Storage
Energy Distribution
Energy Utilization
Hybrid Power Plants

Why do we need Medium Voltage for a Resource-Efficient Energy System?

Considerable installed capacity is required to transform the German energy system to achieve greenhouse gas neutrality by 2045.

With today’s technology, large amounts of raw materials are required to connect the different areas of electricity generation, storage, distribution and utilization. Medium voltage technology, however, offers the key to the resource-efficient integration of renewables in the energy system. The higher system voltages in the medium voltage range enable considerable material, cost and space savings. This technology also allows new system concepts for renewable hybrid power plants whose individual components are interconnected via medium voltage.

Expected installed capacity required for energy generation, storage and distribution to ensure the success of the energy transition in Germany

The following table lists the installed capacities needed for the energy transition in the electricity sector. This shows that approx. 1 TW of installed electrical capacity will be required for Germany alone by 2045. This amount does not yet consider the additional demand from the mobility, heating, IT and consumption sectors, which will also have a high demand in the future.

 

TechnologY

2023
ACTUAL

2045
ISE StuDY

Photovoltaics

82 GW

430 GW

Wind onshore

61 GW

200 GW

Wind offshore

9 GW

66 GW

HVDC for offshore wind

8 GW

46 GW

HVDC and FACTS

1 GW

25 GW

Stationary batteries

8 GW

180 GW

Elektrolyzers

0 GW

83 GW

Total

169 GW

1.030 GW

 

Sources: Energy-Charts from Fraunhofer ISE; Study: "Paths to a climate-neutral energy system"

How can Medium Voltage Facilitate Resource-Efficient Interconnections?

reducing the cable cross-section
© Fraunhofer ISE
For a PV string inverter with 250 kVA, increasing the output voltage from 0.8 kV to 1.5 kV reduces the cable cross-section by 75 percent. If the voltage is increased further, correspondingly smaller cross-sections are possible.

Increasing the system voltage reduces the current in the systems. As a result, the cross-section of the cables can be greatly reduced, one of the most evident effects of the medium voltage use on resource efficiency. Doubling the output voltage, that is, halving the output current, leads to a 75 percent reduction in the cable cross-section required, which can lead to considerable savings in resources.

Furthermore, the use of higher voltages allows electricity to be transmitted over longer distances with lower losses. This not only permits energy generation sources to be used more efficiently but also allows the grid infrastructure to be optimized.

Opportunities for Resource-Efficient Interconnection through Medium Voltage

The use of higher system voltages offers a number of opportunities, which are briefly described below:

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  • The electrification of the energy system and sector integration in the energy, heating and mobility sectors is increasing the demand for raw materials required to interconnect the generation, storage, distribution and utilization of energy in the grid. By 2050, an increase of around 73 terawatts in installed photovoltaic capacity alone is expected worldwide. According to the International Energy Agency’s (IEA) report "Global Critical Minerals Outlook 2024", copper demand will exceed the available supply from 2025 on. Higher system voltages can help here, since this reduces the current flows, which can lead to considerable savings in raw materials, such as copper and aluminum in conducting cables.

  • By moving from the low to medium voltage range, the power output of subsystems in utility-scale PV power plants can be increased. For example, at the medium voltage range of 1,500 volts, only one transformer is required for 10-12 MVA power, as compared to 3-5 MVA per transformer that is common today. Thus, less transformers and switchgears are needed for power plants of the same capacity, which reduces construction and installation costs. Also, it is generally easier to lay and connect small cable cross-sections than large cables. This also leads to lower installation costs.

    For decentralized DC grids, less power electronic converters (rectifier and inverter stages) are required, since generation systems and plants (e.g. solar generators)  already supply direct current and can be connected directly to storage and consumers via the DC grid. The potential and cost benefits increase with greater grid expansion and higher outputs.

  • Energy is a significant cost factor in industry. Energy-efficient, decentralized DC grids are therefore of great importance for the factories of tomorrow. These grids can integrate the DC electricity from renewable energy sources as well as from energy storage systems. This increases the operational efficiency, as losses that would otherwise occur when converting alternating current (AC) from the power grid to direct current (DC) are avoided here.

    In addition, increasing the system voltage can lead to savings in raw materials, thus significantly increasing material efficiency.

  • The phasing out of coal-fired power generation by 2038 and the shutdown of nuclear power plants make the expansion of renewable energy capacity in the energy system unavoidable. Industry must also rethink its operational and energy generation processes in order to reduce CO2 emissions and energy consumption.

    New technologies must be integrated, and climate and environmental targets must be prioritized while maintaining productivity and competitiveness at the same time. For this to succeed, new concepts and the establishment of a sustainable circular economy are essential. Medium voltage is the key to the resource-efficient integration of renewable energies in the future electricity grid and the establishment of a sustainable and resilient energy supply.

  • In densely built-up urban areas, the cost of creating areas for new infrastructure is very high. For example, a new 70 m² underground concrete structure can easily cost €400-500,000 just for the concrete and earthworks. Therefore, there is very high interest in new technologies for the refurbishment of existing systems. The advantages are clear: On an existing area of 70 m², for example, the output of 2.5 MVA can be nearly tripled when using medium-voltage system technology. 

  • Higher system voltages enable the use of completely new system architectures for renewable hybrid power plants. When individual components are linked together in a resource-efficient way via the medium voltage, this allows system approaches for hybrid power plants and the integration of decentralized energy generation to be rethought. It enables more resilient district power supplies, charging infrastructures or even industrial operation with reduced dependence on the traditional power grid.