Introduction

Introduction

This page will introduce and show why offshore wind is needed and why offshore accommodation is required alongside the increase in offshore wind.

 

Why Offshore Wind?

Over the last few years we have seen a ‘rapid’ increase in offshore wind energy. And that’s not  surprise, as according to [5] wind efficiency can increase significantly the further we go from the coast. For example, wind efficiency measured at offshore locations near the coast could be about 40-50%, but at far offshore locations that efficiency would increase to 60-70% [5].

Offshore wind has finally been identified as a competitive source of energy and therefore a lot of investment has been made over the last ten years. According to EWEA, by the beginning of 2013, there were 1,662 offshore turbines with total installed capacity of 5 GW (across 55 wind farms in Europe) [1], as shown in the Figure 1 below.

Figure 1: Annual and cumulative installations of offshore wind in Europe (MW),[1]

Moreover, EWEA forecast states that by 2020 “40GW offshore wind capacity could be operational in European waters, producing 148TWh annually” [1]. It also means that by using offshore wind energy, we could “avoid producing 102 million tonnes of co2 emissions annually” [2].

 

Why Offshore Accommodation?

As discussed above, offshore wind energy is becoming more and more ‘popular’, and also becoming a ‘competitive’ alternative to other energy sources. Therefore, in Europe there a lot of wind farms that are under construction, and still a lot more in the planning stage. As presented in Figure 2., more and more wind farms are moving further away from the shore. Building a wind farm further from the coastline does not mean that the water depth would definitely increase. And that’s what Figure 2 presents.

Figure 2: Distance and depth of online, consented and under construction offshore wind farms, [3]

It is shown in Figure 2 that the distance is gradually increasing even though the water depth does not increase so rapidly as one could imagine. What is important to mention here, is the fact that newly planned wind farms are expected to be built even further then 100 km from the shore.

Therefore as the distance increases, the access to the wind farm becomes more difficult. Also, the travel time to the wind farm will increase as well. Hence, less time would be ‘dedicated’ to perform repair or other maintenance tasks at the wind farm. Also considering weather conditions, at some points that ‘available work window’ would become even smaller as more time would have to be spent travelling to and from the wind farm. Moreover, depending on the size of the wind farm if there is a need to repair more than one wind turbine, it could be expensive for operator to send technicians in CTVs to perform maintenance tasks. It could be possible that operator has to send few CTVs in order to fix the fault and make sure that maintenance tasked could be performed in the same day. However, again, sending more CTV just to make sure more technicians could perform the tasks in a small time window could be very expensive. Especially when such a situation happens often, as presented in Figure 3.

Figure 3: A bar chart presenting how effective working time (red) is reduced by the travel time (blue)

Due to the fact that CTVs are not made for withstanding big wave heights, and that they could only carry 12 technicians, they do not appear as the best solution for far offshore projects. Therefore our group decided to consider another two solutions: mothership and jack-up.

Hence, one out of those three solutions (CTVS i.e. no offshore accommodation, Mothership and Jack-Up) would be chosen depending on the size of wind farm and its location.

Therefore it is obvious that the further the distance, the bigger the need for offshore accommodation.

 

Benefits of Offshore Accommodation

  • Less time spent on travelling to the wind turbines

  • More time available to perform maintenance

  • Better performance of a wind farm

  • Comfortable solution for technicians/workers

  • Sea sickness could be minimized as more stable living accommodation i.e. improved performance of technicians

  • Reduction of preventive and corrective costs

  • Wind turbine’s downtime decreased