The Environmental Impact of Offshore Wind Farms Part 1

The Environmental Impact of Offshore Wind Farms Environmental Studies 70 Final Research Paper 2009 1 Research Assignment December 16, 2009 ENST 70: Senior Seminar The Environmental Impact of Offshore Wind Farms I. Introduction It has long been acknowledged that humanity is constrained in its available resources; maximizing the profitability of such resources is essential for long term survival. While the burning of fossil fuels has existed as the main form of energy generation for a number of centuries, there have been recent calls to switch to sustainable options, with wind being a leading choice. The earth’s wind resource is not only unlimited, it is entirely free. The past two decades have seen the use of wind power escalate by a significant amount – less than 10,000 megawatts (MW) installed worldwide in 1984 to over 90,000 MW installed in 2007 – to reduce electricity production costs and promote clean energy use (Earth Policy Institute, 2007). Land-based wind turbines have made very useful contributions to the sustainable energy movement, but at the same time there has been a push to move offshore and utilize the largely untapped wind resource at sea. Offshore wind power has several marked advantages that have led supporters to make a seaward drive. The advantages can be broken down into divisions: increased power, efficient transportation, and superior design. In terms of power, offshore winds are generally stronger, less turbulent, and more constant than onshore winds. As a result, turbines are expected to operate for a larger share of time than onshore. Because the constancy of wind speed reduces wear on the turbine, the need for other sources of electricity to serve as backups is effectively reduced (Snyder and Kaiser, 2009). In addition, the increased wind speed offshore leads to a 150% increase in electricity production as compared to onshore wind, and an increase in the capacity factor (the ratio of the actual output of the wind farm over a period of time and its output if it had 2 operated at full capacity for the entire period) of the wind farm from about 25 to 40% (Vattenfall, 2007, Junginger et al., 2004). It is critical to investigate how the farms are constructed at sea, as it is easier to imagine the effects that the turbines have on marine and avian life with a mental image. When a suitable place for the farm has been found, piles (deep foundations) are driven into the seabed, usually complete with erosion protection to prevent damage to the sea floor. The top of the foundation is typically painted a bright color to make it visible to boaters and commercial ships (BWEA). The turbine itself is comprised of three blades and a nacelle, a small cover housing that holds the blades in place – some nacelles are equipped with sensors to detect the direction of optimum wind speeds to maximize energy output (BWEA). Wind causes the blades to rotate, which, via gearbox, transfers energy to cables within the turbine’s shaft (structure held up by the piles), and then on to power a generator at the base. Subsea cables take the power to an offshore transformer, which converts the electricity to high voltage before running it back to a grid onshore (BWEA). A wind energy system transforms the kinetic energy of wind into mechanical or electrical energy that can be harnessed for practical use. The power generated by turbines is typically measured using kilowatts (KW), megawatts (MW) or gigawatts (GW); in some cases, the term ‘kilowatt-hour’ is used to indicate the amount of electricity produced or consumed in one hour (American Wind Energy Association, 2009). To clarify, the average U.S. household uses about 10,655 kWh of electricity each year, and one MW of wind energy can generate from 2.4 to more than 3 million kWh annually (American Wind Energy Association, 2009). Therefore, a MW of wind generates about as much electricity as 225 to 300 households use (American Wind Energy Association, 2009). The given output of a turbine is dependent upon its height and blade size, as well as the speed of the local wind; larger turbines placed at distances far offshore will produce 3 more in a given period of time than smaller ones. An understanding of these relationships is useful, as it makes clear the amount of energy being created (and in many cases, saved) through the use of wind turbines. The methods with which offshore wind farms are constructed also play to the advantages of the industry. Marine transportation cranes are capable of handling larger equipment than onshore cranes, allowing for larger turbines to be erected at sea (Snyder and Kaiser, 2009). The size of onshore turbines is limited by the ability to transport enormous turbine components, while these constraints are not an issue in the water – many offshore turbines already exceed 5 MW and may eventually exceed 10 MW (Snyder and Kaiser, 2009). Transportation costs can also vary with increased distance from shore and with water depth; the currently proposed Cape Wind project near Cape Cod is widely regarded as the strongest plan for the first United States offshore farm due in part to the presence of shallow waters and therefore relatively low transportation and construction costs. Lastly, in the way of design, offshore wind projects tackle the problem of noise, an issue during both the construction and operation phases. In general, the sounds emitted by modern wind turbines are usually masked by other natural sounds in the area (OEERE, 2005; WRA, 2005). Turbine noise is an oft-cited criticism made by opponents to onshore wind power, but the offshore industry generally focuses on locations far enough from shore to provide an effective solution for those bothered by rotational blade sound. To date, Europe stands ahead of the United States in offshore wind turbine construction – there are 28 offshore farms currently operating in European seas, and although the United States has several proposals in waiting, the United States has yet to open its first offshore farm (EWEA 2009). Although the cost of wind itself is zero, the construction, operation, and maintenance of wind turbines carry substantial ecological and economic implications. The aim of the following 4 section is to examine the ecological effects of offshore wind farms in selected areas throughout Europe, with a focus on Germany, Denmark, and the United Kingdom. In order to prepare for a more successful offshore wind movement in the United States, it is valuable to analyze the ways in which the ecological community has been affected (and will be affected) by the presence of offshore wind farms in Europe. II. Environmental effects on avian life A. Collision risk During yearly migration periods, several hundred million birds of over 250 species cross the North and Baltic Seas on their journeys between their breeding grounds in northern Asia, North America, Scandinavia and their winter quarters (Dierschke et al., 2003). Both seas are situated at the center of a global network of migration routes, and they both serve as premier sites for molting, feeding, and resting grounds for internationally significant numbers of water birds (Garthe, 2003). It is for this reason that the Offshore Installations Ordinance has stated that licensing will not be given if the obstacles presented by the construction of offshore wind turbines jeopardize bird migration (Huppop et al., 2006). These areas of the world are notorious for their large number of bird populations, and it seems clear that the introduction of wind turbines would have some measurable consequences for avian life. Furthermore, it is important to stress that wind turbine planners are concerned for all types of birds living in project vicinity because of the largely unknown effects that turbine presence can have over extended periods of time. 5 European evidence for the main effects on birds, which include collision, barrier effects, displacement due to disturbance and habitat loss, has shed some light on the ecological cost of offshore wind farms (Drewitt and Langston, 2006). In order to be effective, wind farms must be sited in open, exposed areas with high wind speeds – typically areas that provide habitats for avian breeding, wintering, and migration. However, the effects of a wind farm on birds are highly variable and depend on a wide range of factors, which gives further reason to investigate the specification of the development, the habitats affected, and the number and species of birds present (Drewitt and Langston, 2006). A large number of studies have been conducted in areas throughout Europe and have yielded some interesting results. As mentioned above, a leading issue surrounding avian life and wind turbines is the possibility of collision mortality. In the past, bird collisions with non-natural structures have been a well-documented phenomenon. Some of the popular collision incidents have occurred at lighthouses (Hansen, 1954, Jones and Francis, 2003), communication masts (Avery et al., 1977), and plate glass windows (Erickson et al., 2001). The effect of bird collisions is likely to be more pronounced at sea then on land because there are few, if any suitable resting places at sea for terrestrial birds (Huppop et al., 2006). This means that terrestrial birds will typically spend their time flying while they are not on land, thereby increasing the probability of collision. In order to measure these collisions, Huppop (2006) and his colleagues monitored bird migration across the German Bight by installing an illuminated platform with two ship radars, a thermal imaging camera, a video camera, and a directional microphone beginning in 2003. The system, known as ‘FINO 1’, served to detect dense migration traffic as well as adverse weather conditions. The radar data derived from FINO 1 helped shed some light on the flight patterns of migratory birds, as almost half of the birds detected in the study were observed to fly at ‘dangerous’ altitudes 6 (Huppop et al., 2006). This study is important because it showed that migratory birds are under some increased risk if they fly often and at altitudes that could eventually contain large steel structures. More generally, direct mortality or severe injury can result not only from collisions with turbine blades, but also with towers, nacelles and associated structures such as cables, power lines, and meteorological masts (Drewitt and Langston, 2006). In addition, there is a possibility for birds to be forced downward by the vortex created by the moving rotors (Winkelman, 1992). Although turbines pose a constant risk to birds, relatively low mortality levels have been recorded – this could be attributable to the fact that many records are solely based on located corpses, and do not account for bodies that are overlooked or removed by scavengers (Langston & Pullan, 2003). It is difficult to account for all avian death, but published studies generally agree that overall collision risk is low. Until collision risk is zero, however, it will continue to be relevant in the offshore debate, particularly among environmental specialist groups. Examining additional variables that increase collision risk is necessary to find the optimal location and layout for an offshore farm. One important factor that could increase collision risk is impaired vision (Duchamp, 2003). The eyes of most birds are located on each side of the head, and their eyes can cover a field of vision nearing 360 degrees in order to detect predators coming from any angle. On the other hand, their quality of perception is mediocre at the limit of 180 degrees covered by each eye. Put another way, a bird typically has poor vision of areas directly in front, right behind, right above, and right below itself (Duchamp, 2003). Risk is also significantly influenced by weather patterns, as areas with a tendency towards dense fog and heavy rain are likely to impair visibility of large structures (Drewitt and Langston, 2006, 7 Erickson et al., 2001). Thus, it is expected that birds could accidentally travel on the trajectory of a turbine blade when visibility is hindered by bad weather. The consequences of impaired vision are also important in analyzing the threat that offshore turbines present for birds. First, the risk is amplified at sea, as offshore turbines are typically taller and have longer rotor blades; simply put, the offshore turbines take up more space. Also influencing risk are the number and behavior of a particular bird species, as well as the specific nature of the wind farm itself (Drewitt and Langston, 2006). Risk is clearly increased if there are large numbers of birds feeding, roosting or mating in a particular area, or if the area of the wind farm is in the middle of a popular migratory flyway (Drewitt and Langston, 2006). Larger birds are also likely to have relatively poor maneuverability, while species that typically fly at dawn or dusk are less likely to successfully avoid turbines (Brown et al., 1992, Larsen & Clausen, 2002). Collision risk is augmented further because of the natural noises that are generated from wind and waves at sea, and the ability to hear while in flight is a vital detection mechanism for avian life. Although avian death statistics are somewhat limited for offshore wind farms, several coastal projects in Northwest Europe have yielded relevant information. Studies at selected sites have shown varied results - for instance, in the Netherlands, the yearly average collision rate ranges from 0.01 to 1.2 birds killed per turbine per year; at Blyth, a famous wind farm in Northumberland, England, 6 birds are killed per turbine per year; and at three study sites in Flanders, Belgium, between 4 and 23 birds were found to be killed per turbine per year (Painter et al., 1999). At Blyth in particular, in Northern England, there was observed a greater level of bird death by the Common Eider (Somateria mollissima) by about 0.5 – 1.5%. The Eider, a large sea duck, is particularly common in coastal areas where it can regularly breed and dive for food. 8 A possible influence of increased collision rate could be the Eider’s characteristic wide body, which also increases the probability of an accident. Due to their large colonies, (there are about 2 million Eiders in North America and Europe) it seems probable that simple space constraints while in flight could lead to the incidence of collisions. There is also a possibility that flying in large groups or flocks may increase the percentage of casualty. Another phenomenon that has stemmed from the presence of turbines in European waters is the barrier effect, or the result of birds altering their migration flyways or local flight paths to avoid a wind farm. Observations at Nysted offshore wind farm in Denmark have introduced more detailed information on flight paths that could also influence observed collision risk. Radar and thermal imaging studies suggest that most birds can divert their flight paths up to three kilometers away in daytime and up to one kilometer at night, in their efforts to avoid the turbines altogether (Desholm, 2005). In the light of day, birds can clearly see the turbines, although the chance of flying through the turbine cluster is greater because they can more accurately judge the space between turbines. Conversely, birds are more likely to fly around the clusters at night presumably as a result of limited detection. Birds (the Eider, in particular) have the ability to adapt to the farms almost completely when the turbines are visible, but experience a much greater risk as night falls due to a loss of spatial awareness. In addition, from one single Thermal Animal Detection System sequence (TADS), it has been discovered that passerines (songbirds) have exhibited the ability to stop still in space in very close proximity to the turbine rotor sweep and avoid collision by flying away from the danger area (Desholm, 2003, 2005). There is still some concern for species that forage and travel at night; the good news, however, is that there is evidence of adaptation. The ability for birds to learn is advantageous to offshore wind supporters, as learning will allow seafaring as well as 9 terrestrial birds to protect themselves from man-made structures. Evidence from 2003 studies at Horns Rev and Nysted in Denmark suggested that Common Scoters on migratory fights avoided the wind farm and its immediate vicinity, although changes in their flight distribution were “likely not solely caused by the presence of the wind farm” (Exo et al., 2003). A major contributing factor is the distance between turbines; at Nysted, the Common Eider routinely flies in between turbines that are 480 meters apart (Christensen et al, 2004). Dierschke and his colleagues (2003) hypothesized that an overall increase of the existing adult mortality rate by 0.5 – 5% for the 250 bird species regularly migrating across German seas will occur due to the presence of turbines (with some variation depending on the individual species). It has also been observed that a wind farm in the German Exclusive Economic Zone (EEZ) has had a barrier effect on migrating birds, which forces them into energy consuming evasive action. In other words, birds must expend energy while going out of their intended flight path to avoid the turbines. These forced detours can lead either to direct loss of individuals or the reduction of reproduction rates, and hence have a negative impact on the population or development of some species. (Koeller et al., 2006) In determining the energetic cost to birds as they fly around and through wind farms, it is necessary to use pre- and post- construction data, in an attempt to quantify the level of avoidance shown amongst bird flight paths that occur following turbine implementation (Desholm and Kahlert, 2005). Avoidance of turbines by migrating birds is likely to be low in energetic terms, as avoidance of present scale wind farms consisting of 80-100 turbines would result in additional flight costs of about 20 km in order to completely avoid the turbines (Fox, et al., 2006). On the local level, a small extension to a migration flight of several hundred kilometers is likely to contribute little to total energy expenditure in comparison to flying through strong and 10 unfavorable winds (Fox, et al., 2006). Under these circumstances, at the local offshore wind farm level, the additional energetic costs are likely to be insignificant (Fox, et al., 2006). However, this may not be the case for birds commuting on a daily basis between feeding other areas used in routine activities. For example, the Common Scoter (species of large sea duck) and Long-tailed Ducks (Clangula hyemalis), move daily between feeding and roosting areas on their wintering grounds. On a greater spatial scale, construction of offshore wind farms along a migration corridor of a long-distance water bird (such as the Scoter or Long-tailed Duck) may begin to have a greater cumulative energetic cost (Fox, et al., 2006). In this situation, it becomes necessary to account for additional barrier effects when modeling total avian flying and energetic costs. If offshore wind farms are viewed as significant barriers to avian movement, some comparative judgment can be made when considering the effects of offshore wind farms versus other forms of environmentally impactful human activities. The lasting consequences of barrier effects are largely unknown but are the subject of several current research projects. Thus far it is reasonable to conclude that birds have shown the ability to avoid wind turbines, but this response varies within and between species (Hotker et al., 2006). Birds such as the Eider were able to adjust their flight trajectories to avoid the wind farm area postconstruction at Nysted, which shows a learned response to the presence of turbines. The additional distance that Eiders typically have to travel in order to avoid the farm is trivial in comparison to their migratory distance. Studies have also indicated that the cumulative effect of many similar wind farms could impact a population; that is, if birds are constantly forced to avoid turbines, they will expend an amount of energy significantly greater than if the turbines did not exist (Masden et al., 2009). Regardless of the existing gaps in knowledge, some mitigation measures can be 11 recommended for the spatial planning of offshore farms. These measures include, but are not limited to: abandonment of wind farms in zones with dense migration, alignment of the turbines in rows parallel to the main migratory direction, free migration corridors of several kilometers between turbines, avoidance of construction of wind farms between resting and foraging grounds, turning off turbines on nights predicted to have adverse weather and high migration intensity, refraining from large scale continuous illumination, and taking measures to make wind turbines more recognizable to birds (Huppop et al., 2006). As Denmark, the UK, and Germany have all displayed a desire to monitor bird safety, in addition to the fact that birds are highly migratory, it has become clear that successful mitigation will require an international approach. The point of the preceding section is that the construction of offshore wind turbines can have some effects on some bird species, although on the overall the wind farms themselves do not present serious population risks. Bird mortality as a result of collisions does evidently occur, albeit in small numbers. In some studies, it is uncertain as to whether or not bird mortality increased simply because the turbines are there, or if mortality was a result of one or more other factors. A bird may have crashed into a turbine because it was sick or dying, under the pressure of a predator, or traveling in unfavorable weather conditions. It would be interesting to conduct a study that encompassed both observational and experimental elements, in which a site was observed before and after construction, and the experimenter was able to control for variables such as weather. For environmentalists, the goal is to minimize the probability of collision, considering that it is certainly possible that turbines do in fact raise the probability of collision at a minimal rate. Taken together, collision risk among seafaring and terrestrial birds as a result of offshore wind turbines should be viewed as relatively low. 12 B. Habitat loss and displacement Apart from collision risk and the barrier effect, avian life is also susceptible to long-term habitat loss and displacement. Habitat loss involves resident birds simply being directly or indirectly pushed out of the areas in which they live due to the presence of wind turbines. Studies of two Danish wind farms at Tuno Knob and Horns Rev provide examples of such avian disturbance: at the two sites, a decrease in the number of Common Eiders and Common Scoters was observed following turbine construction. This initial decrease was followed by a more than full recovery of Eiders, but only a partial increase of Scoters (Guillemette, et al. 1998). It may have been the case that Eiders were more suited to adapt to the changed landscape, and were better prepared to tolerate the increased noise disturbance. A different explanation could be that the construction led to a dampened “reef effect” in which the base of the wind turbines became temporary habitats for mollusks; as Eiders prefer mussels as a source of food, it seems likely that an increase in the Eider population would follow as a result. Besides species-specific differences in disturbance avoidance, the degree to which birds are able to live in offshore wind farm locations also depends on several factors, which include the availability of alternative habitats (especially roosting and feeding areas), time of year, flock size, and the layout of the wind farm (Exo et al., 2003). If a bird is a specialist species, that is, it can only survive under particular habitat conditions, habitat displacement is an even more serious threat. Habitat loss of birds that nest in coastal waters is also linked to a number of other factors. During the construction phase, considerable acoustic emissions are common during foundation implantation – species of birds in the North and Baltic Sea are typically displaced, contingent on noise intensity and frequency range. In addition, the Baltic Sea remains one of the busiest 13 transportation waterways in the world. According to the Helsinki Commission, around 2000 ships are normally at sea at any time on the Baltic, and cargo and container traffic is expected to triple and oil transportation is estimated to increase by 40% by 2017 (B.S. 2020). As the Baltic contains a large number of islands, narrow straits, and difficult-to-navigate routes that are ice covered in the winter, the Sea is an area of high risk for accidents. Collisions of ships with offshore turbines could occur, causing irreparable damage to the surrounding avian habitat. The degree to which a specific ecosystem is affected, however, is highly dependent on the layout of the wind farm and the biodiversity at that location. Essentially, birds like the Eider have demonstrated the tendency to colonize in large numbers in centralized locations; the introduction of offshore wind turbines could potentially lead to a flurry of other issues, and leave the species without a reasonable or accessible alternative habitat. The objective in combating habitat loss, as mentioned above, is to assess the degree of territory loss for a given population of birds that results from the creation of an offshore wind farm. This assessment should be based on as large a sample gathered during as many baseline years (a year occurring before the farm had been constructed) as possible to account for year to year variation in bird abundance and distribution (Camphuysen et al., 2004). The estimation of habitat loss is costly and time consuming, however, as it is difficult to physically measure out sections of water or land that are no longer in use by birds. In addition, it is difficult to determine whether or not wind farms are the causal factor for bird displacement. As a result, effective and actual habitat loss can be measured using bird densities as a proxy measure for bird habitat area (Fox et al., 2006). To date, little concrete information is known of the effects of wind farms on bird populations because of a lack of pre- and post-construction studies that show change over a period of time. 14 The call for longitudinal studies has obviously been prevalent in the offshore wind farm conversation. It is imperative to stress the need for adequate baseline and post-construction sampling. A baseline period must be long enough to show some degree of natural variation in bird habitat pre-construction, matched by a similar period of variation after the turbines have been built (Fox, et al., 2006). In Germany, for example, a minimum of 2 years were proposed for baseline studies, with a minimum of 3 to 5 year monitoring post-construction (Huppop et al., 2002). 5 year monitoring is undoubtedly costly (and more than likely, quite tedious) but a lengthy timeframe is invaluable to account for the natural variability in bird abundance in a given area (Fox et al., 2006). For instance, in the case of the Long-tailed Duck distribution at Nysted, using data from only 2 baseline years in 2001 and 2002, a significant and dramatic bird displacement of almost 15 km had been detected (Fox et al., 2006). Essentially, without studies that take place for long periods of time, it is difficult to accurately state whether or not the movement of a bird or bird species is due to natural variation or the presence of offshore wind turbines. Avian concerns have played a significant role in the construction of offshore wind farms in Europe to date, although the extent to which avian populations will be affected over time by is largely unknown. At this juncture, it is apparent that the risk of avian death is heightened by factors that include, but are not limited to: a lack of light (that is, the birds cannot physically see the turbines), construction acoustics, natural noise of wind and water, turbines that are placed too close together so as to prevent birds from flying between them, habitat-specific characteristics (such as human presence), and species-specific differences (i.e., a particular bird has a relatively larger body than other birds in the area, and may be less likely to maneuver its way through a row of turbines). It is obviously important to consider these factors in the selection of offshore 15 locations, and scientists and designers have only been able to use the limited, short-run information that they have about avian death to make long-term decisions about turbine placement. That said, current evidence is yet to show that any of the aforementioned factors is certain to pose significant long term implications for the offshore wind industry. This section serves as a thorough assessment of the potential risks and risk factors that are related to a variety of avian life forms in Europe. While the avian ecology is surely different in the United States, an analysis of bird behavior in response to offshore wind turbines in Europe can be used as a valuable learning instrument. 16