1st Wind Farm Siting Challenge - Assessment part 1
To determine the best technical and economic area several datasets are needed that inform us about the options to develop offshore wind turbines. Datasets were searched to support the following objectives:
- An economical and viable development needs a market for the electricity it produces. This means the presence of cities, ports or large industrial sites. Alternatively high voltage connection points can also be used to reach a market. Currently existing connection points are often located near cities, ports, large industrial sites and power stations (conventional/nuclear/etc.);
- Developing offshore wind energy also requires facilities like ports, quays and cranes to support the activities of building, operating and maintaining the turbines and the supporting infrastructure of cables and transformer platforms. On-shore this also means that availability of motorways, railways and airports are necessary, e.g. to allow specialized persons or replacement parts quick access to the area.
A search has been done to identify locations that satisfy objectives 1 and 2. The results are bundled together Table 1 and figure 1.
Table 1 Locations represention both market and presence of infrastructure in relation to offshore wind energy development (data from a.o. Wikipedia and other websites of municipalities and ports). Suitabillity or presence of infrastructure is indicated as follows: 0 absent/unsuitable; 1 present/suitable; 2 with limitations.
|Name||Inhabitants||Port Maint||Port Cons||Heavy Ind||Grid Connect||Railroad||Motorway||Airport||Country|
Figure 1 Map of the Norwegian Sea and Barents Sea, showing the locations from the table above. Yellow-to-orange colours indicates the identified area suitable for offshore wind farm development, darker colours signify higher mean wind strength.
Next two further datasets become important:
- Bathymetry (water depth, metres) (GEBCO 2014 gridded bathymetry 0.0083 degrees)
This helps to inform where suitable water depths occur that are compatible with either a fixed or a floating offshore wind turbine.
- Wind strength (m/s) (Copernicus Marine Environmental Monitoring Services or CMEMS)
CMEMS has a set of satellite-derived datasets (with global coverage 0.25 degrees ) available that covers six recent years, with monthly wind climatology for 59 months (from 72 months, so a few are missing). Too ease the analysis an average wind resource was calculated and used.
Please note that the instrument on the satellite, a scatterometer, comes with its own limitations. One of these is that a scatterometer cannot determine windspeeds over land or over an ice-covered sea. Thus the average wind resource dataset has no data where sea ice has prevented observations during the observation period.
More on this separately, but this is not a severe problem given the current technology.
The available wind resource for the Norwegian Sea is comparable and possibly somewhat larger than in the North Sea. Where data is available the same holds true for the Barents Sea. As such there is sufficient wind resource available.
The resolution of this dataset is used also for the analysis.
A third important dataset has been derived based on the data from points 1 and 2, in combination with a geographical dataset of the coastlines (Arctic countries coastlines)
- Distance to port and market
This is useful to determine how far – by sea – it is to a possible site to develop an offshore wind farm. This distance is an important economical factor as it determines many costs, such as length of the HV-cables bring the generated power to market, travel time when building, operating and maintaining the wind farm.
Assessment Part 1
To properly interpret the datasets outlined above some realistic assumptions about offshore wind technology options are needed.
- How far from port and market is it economic to attempt to develop OWE?
The maximum distance within the North Sea, currently one of the best developed OWE areas, is a little over 200 km (close to the centre, on the Doggerbank). For the purpose of this study the upper limit has been set at 250 km.
- How does water depth interact with offshore wind turbine technology?
- Fixed OWT can be built to water depths to about 50 m. deep, with several construction options including monopoles, tripod, jacket and gravity-based (concrete) foundations structures. This choice more or less follows the current state of technology in the North Sea
- Floating turbines can be built in water depths starting from ca. 100 m. to ca. 500 m. deep. These numbers match with pilot installation s and early wind farm developments for turbines such as the HyWind (SPAR-type) and WindFloat (floating jacket). This technology is still young and not many such turbines are current in operation.
Data assembled by the EU-project ACCESS on a.o. SPAR-type platforms (D 4.21) shows that these are reasonable assumptions
- Sea ice and offshore wind turbines
Offshore wind parks have not yet ventured in to (sub-)Arctic waters, thus also staying clear of waters where sea ice (or larger ice floes) can occur. Technically it is possible to build wind turbines strong enough to withstand the forces exerted by sea ice. It adds cost and the economics of offshore wind turbines does not allow for such additional costs. Based on that conclusion the pragmatic choice made for this study to not suggest OWE development in ice covered waters also has a based in economics. Pragmatic as the scatterometer data do not allow for collection of wind speed data (by way of a satellite) over ice-covered sea areas.
Please note that technology options to construct ice-resisting OWT do exist and some of those can be gleaned from the reports of ACCESS.
When considering the development of OWE in these waters, icing of the turbines blades can form one more complication that requires both technical attention and may impact the economics. This is an active field of research within wind turbine development.