Environmental Analysis

Every technology that is build to with a purpose of being used in a natural environment has to undergo environmental impact assessment. Therefore, in this section, our group would like to underline how previously suggested solutions might affect marine environment and also what risk could be associated with each solution.

The table below presents the results regarding environmental impact. The results reflect our individual views, which are based on various papers that concentrate on environmental matters.

Table 7: Environmental Impact of a CTV, Mother-ship and Jack-up vessel

Environmental Impact	CTV	Mothership	Jack up
CO2 Emissions (kg/day)	2238	1678	5476
Visual Intrusion	Low	Low	Low
Noise	Depends	Depends	Depends
Seabed Conditions	Low	Low	Major
Vibration	Low	Low	Low
Accidental pollution of sea caused by collisions	Depends on number of CTVs	Major	Major

 

Emissions

New environmental regulations intend to decrease the amount of emissions produced by vessels. Therefore new types of vessels are said to incorporate “energy efficient diesel-electric power generation and propulsion systems” [17]. It is also said that modern vessels will use “a number of renewable energy devices to supplement the power generation and support systems, reducing the overall carbon footprint of the vessel” [17].

In our calculations we considered a case when CTV is in a transit speed mode, and mother-ship together with jack-up were considered to be in a stand by mode. Using those assumptions it was calculated that mother-ship actually produces less CO2 emissions (kg per day) then CTV. On the other hand, even though jack-up is also considered to be in a stand by mode, it was found that this kind of vessel would produce the biggest amount of CO2 (out of those 3 vessels).

 

Visual Intrusion

Onshore wind farms draw a lot of attention and a lot of negative attitude towards wind energy. People living nearby usually present ‘Not In My Back Yard’ attitude and simply do not want wind turbines around their houses. Fortunately, discussion about visual impact of offshore wind farms is not as controversial. What is more, even the effects of offshore wind farm located near the shore do not receive negative feedback. For example, Near Shore Wind farm in the Netherlands (located 2-15 km from the shore [16]) received 94% positive feedback from people living nearby [12]. Hence, the visual impact of the infrastructure of operation and support vessels is considered as minor or negligible.  

 

Noise

Propeller produces the most amount of noise in a vessel, “except when operating at low speeds” [11]. During the wind farm lifecycle, the number of vessels operating at a site will increase. Hence the level of noise affecting marine sea-life will increase as well. However, there are not enough studies to show the effect of ‘increasing’ traffic around wind farms.

The table below presents main information regarding noise level produced by different types of vessels.

Table 8: Noises caused by different kinds of vessels, [11]

Small vessel (14 – 19 m)	<62 dB
Middle size vessel (up to 25 m)	<70 dB
Large ship (173 meters – overall length)	~192 dB
Jack up	~120 dB re 1 μpa

According to [11], the reactions of marine creatures to vessel’s noise may vary. The noise could bring positive or negative effects, however the reaction would be different depending on a kind of species. The only major concern, that would include all three types of vessel, is the assumption that operational noise connected to different types of vessels will last over a certain amount of years (i.e. operational phase of a wind farm). Hence, such actions would effect “a generation of marine wildlife. Therefore a rigorous assessment of the environmental effect from a wind farm must be made” [11].

It has been showed that risk related to underwater noise level seems to be low. Having said that different sources suggest that there has not been enough research undertaken. Hence more studies should be performed in order to find out what are the real effects of the wind farm infrastructure [11].

 

Seabed Conditions

Jack-up

It seems jack up has the biggest impact on marine seabed conditions (out of 3 solutions). In order to safely proceed with any operation, the vessel needs to be positioned properly on the seabed. It is important that all four legs are able to provide necessary support. However, jack ups cannot be used in all seabed conditions. In order to make them suitable there are methods e.g. ‘rock dumping’ or ‘swiss cheesing’, but those methods could bring even more negative environmental effects [8]. 

Another environmental issue related to jack up is when the vessel leaves the site. It could be “very difficult to extract the legs from the seabed” [8].  However, the vessels are “expected to leave the seabed as far as possible in its original form” [8], which does not mean that it actually happens every time the jack up leaves the site. The good approach is when “extensive seabed penetration” is not performed and so the effects on the seabed are not as considerable.

Hence if extra equipment is used, the effects of the vessel on the environmental could be minimal.

 

Mothership & CTV

There has not been many research performed in the subject of environmental impact of mother-ships and CTVs on seabed conditions. The only effect they could cause would be resulted by mooring lines. However there is more danger that mooring line would affect underwater cables, rather than they would cause a significant environmental damage.

 

Vibration - All 3 solutions

Unfortunately there is not enough data that could prove the effects of vibrations on marine mammals [12]. On the other hand, the research concentrated on fish shows that the vibrations are very low and so fish simply adjust to those noises  [12].

 

Accidental Pollution of Sea Caused by Collision

Based on the studies performed by Dutch and British researchers, it was concluded that the possibility of accident caused by the collision of vessels is very small. A probability of such event happening could occur “every 1.8 to 23.169 years, depending on the type of the vessel” [12]. It also seems that the risk of such even occurring is connected to the operation of fishing vessels.

Hence, it seems that the likelihood of such incident happening is small. However it has to be mentioned that such accident could bring catastrophic consequences to the marine environment [12].