7 Mar 2018 9:47 (GMT+1)
Transmission technology increase energy transfer
Innovative grid connection will cut offshore energy costs
Whether it is remote offshore wind power or deep-water oil and gas production, energy resources far out to sea require cost effective, cutting-edge technology to achieve their full potential.
The only feasible way to transmit power efficiently to and from production platforms that are more than 80 kilometres (50 miles) offshore is by direct current (DC) technology. As the market leader in grid access solutions - with four platforms in operation using innovative high-voltage direct current (HVDC) technology - Siemens has been busy developing the next generation of DC grid-access technology for offshore wind farms.
Now the multinational engineering and electronics conglomerate has unveiled a new direct current technology solution which will provide a simplified, cost-efficient grid connection for offshore wind power plants in remote locations far from the coastline.
The new platform housing Siemens' pioneering new transmission technology will be considerably smaller and more compact than the conventional large central converter platforms which, until now, have been used to connect offshore wind turbines to the grid. Over time, it's expected that numerous smaller offshore converter platforms will replace the separate alternating current (AC) substations and HVDC platforms used by offshore wind farms.
According to Siemens, the new grid connection will achieve 30 per cent cost savings compared with the existing options. The new transmission technology will also be capable of transferring 33 per cent more capacity than current converter platforms and also reduce transmission losses from 20 per cent to about three per cent. The new energy-conversion technology is based on encapsulated high-voltage electrical equipment which uses diode rectifier units (DRUs) instead of conventional air-insulated transistor modules.
Siemens is now further developing the transmission technology in preparation for the building of a large number of much smaller, more cost and energy-efficient conversion platforms. The energy transmission solution enables a DC cable to connect several platforms sequentially in a wind farm and then route them to an onshore transformer sub-station.
The compact design is modular and flexible, making installation easier. Developers say the size of the platform is reduced by four-fifths with the structure's weight also down by two thirds - key factors in lowering overall costs by more than 30 per cent. This is described as a major step towards significantly reducing the cost of offshore wind power. It could make the offshore wind industry more competitive in comparison with conventionally-generated electricity.
The diode rectifier units (DRUs) are the core feature of the transmission technology solution.
ach DRU has a transmission capacity of 200MW and is the core of the new transmission technology which also features a transformer, smoothing reactor and rectifier - all combined in one tank. The use of DRUs and encapsulated direct current compact switchgear (DCCS) decreases installation space by more than 80 per cent compared with air-insulated technology.
Biodegradable ester liquids are being used for the first time to insulate high voltage DC equipment. As well as being more environmentally-friendly than mineral oils, they are also flame-resistant. DRUs are designed for continuous operation over many years with minimal maintenance requirements.
"We have already successfully commissioned four offshore direct current connection projects. Now we are applying our experience directly to the next generation of direct current grid connections," says Jan Mrosik, chief executive officer at Siemens Energy Management Division. "Our new solution will play a major role in decreasing the cost of offshore wind power below ten cents per kilowatt hour by 2020. This is how we plan to make the direct current technology used in Germany more interesting to other markets too."
Siemens launched its new transmission technology at the National Maritime Conference held last week in Bremerhaven, Germany. The company expects work on the new system to be complete by June next year. Offshore energy developers in Germany and the UK are keeping a close eye on its progress.