World’s First Unmanned HVDC Offshore Platform Installed At World’s Largest Offshore Wind Farm
The title of this post, is the same as that of this news item from the Dogger Bank wind farm web site.
These are the two bullet points.
- Dogger Bank Wind Farm will be first UK High Voltage Direct Current (HVDC) connected offshore wind farm
- 70% reduction in topside weight per MW for offshore platforms
These are my thoughts.
High Voltage Direct Current
Wikipedia has an excellent entry on high voltage direct current, which is commonly referred to as HVDC.
The news item says this about how the electricity is brought ashore from the Dogger Bank wind farm.
The innovative offshore platform has a lean design and is the first unmanned HVDC platform which will be operated from shore and accessed only by a Service Operations Vessel. The platform will receive 1.2GW of AC power from Dogger Bank A’s 95 offshore wind turbines and convert it to DC, which will then be sent ashore to an onshore convertor station near Beverley in East Riding of Yorkshire.
Fitted with Hitachi Energy’s latest generation HVDC converter technology, Dogger Bank will be the first offshore wind project in the UK to use this technology to transmit the electricity produced back to shore, ensuring that the electricity is transmitted efficiently over long distances while minimising losses.
Note.
- Wind turbines generate AC.
- There will be conversion to DC on the substation and conversion back to AC onshore.
- It should also be noted, that large undersea interconnectors are generally built around HVDC technology.
Wikipedia says this about the advantages of DC transmission.
A long-distance, point-to-point HVDC transmission scheme generally has lower overall investment cost and lower losses than an equivalent AC transmission scheme. HVDC conversion equipment at the terminal stations is costly, but the total DC transmission-line costs over long distances are lower than for an AC line of the same distance. HVDC requires less conductor per unit distance than an AC line, as there is no need to support three phases and there is no skin effect.
Depending on voltage level and construction details, HVDC transmission losses are quoted at 3.5% per 1,000 km (620 mi), about 50% less than AC (6.7%) lines at the same voltage. This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power.
It looks like cost is a big factor.
My knowledge of grid systems and AC power is limited, as I was more of a Control Engineering and Electronics student at university.
But could HVDC-connected wind farms have advantages, when it comes to providing a reactive power capability to the grid, as I wrote about in Dogger Bank C In UK Offshore Wind First To Provide Reactive Power Capability.
Extra income is another good reason to choose something.
Lightweight Platforms
I’ve always been a fan of lightweight structures and it does seen that the engineers of the Dogger Bank Wind Farm have gone down that route.
This is a paragraph from the news item.
The platform will be controlled from shore and by removing the need for personnel to stay on the platform meant it has been possible to eliminate elements such as the living quarters, helideck and sewage systems, resulting in a 70% reduction in weight (per megawatt) of the topside compared to previous platforms installed, and cost savings of hundreds of millions of pounds.
Again costs are being reduced and profits increased.
We should never rule out the importance of the finances of a project. Once by simulating a chemical process on the computer for ICI, I knocked ten metres off the height of a chemical plant. I got a nice little bonus for that!
If they have made a substantial reduction in substation weight, this surely means that the supporting structure can probably be smaller and less costly.
Conclusion
I suspect, a lot more wind farms will follow the Dogger Bank example.
No comments yet.
The Anonymous Widower 
Leave a Reply