1. Introduction
By analysing the global trade market one can easily notice that the maritime sector plays an important role in economic development. It is estimated that almost 80% of the global trades are transported by means of sea transportation. The sector is indeed very dynamic and has reported an annual increase of 3.2% between 2017 and 2020 [
1]. On the other hand, industry is a major pollution source, and as a result, various legislative provisions have been introduced in order to protect the ocean environment and maritime resources. On a large scale, the CO
2 emissions associated with global warming are generated by navigation between ports, while on a local level, the port activities (also known as hoteling) are the main factors that have a negative impact on the human health around the port cities. If no significant change occurs, the air quality near the coastal cities will be significantly reduced due to the large nitrogen oxides (NOx) emissions, Particulate Matter (PM) and Volatile Organic Compounds (VOCs), respectively [
2,
3]. This problem is well known and most of the major harbour areas are under constant surveillance. This is the case for the Shanghai Port [
4], Naples [
5], Los Angeles [
6] or Sydney [
7], respectively.
Cold ironing or Onshore Power Supply (OPS) is one of the methods which could be used to help reduce local air pollution and improve the air quality near the coastal areas. OPS is used to describe the process of connecting a ship to a shore-side electrical supply in order to maintain the main function of a ship (ex: heating, refrigeration, emergency systems, etc.) at berth, during which time the engines are turned off. While the concept looks promising, with almost 6% of fuel consumption of a ship being allocated to the hoteling period, at the moment, only 30 ports are using this technology. The main challenges to be tackled for the use of such technology are related to the additional port installations and are caused by the fact that most of the operating ships are not equipped with systems compatible with the use of electricity from the shore [
8]. Renewable energy sources (RES) represent an important part of the cold ironing process and their use has already been implemented at the port of Gothenburg (Sweden), which uses a shore-power source based on a local wind farm. By using this source, it is estimated that for the six weekly ships (Roll-on/Roll-off) connected to this project, an emission reduction of 80 metric tonnes for NOx, 60 metric tonnes—SOx and 2 metric tonnes for PM is expected [
9]. The port of Hamburg (Germany) is considered another important project, where a significant part of the electricity demand is covered from wind and solar sources. For an initial investment of €4.8 million, it has been estimated that for the year 2014 almost two-thirds of the power consumption has been covered from natural sources or from additional combined heat and power plant (CHP) [
10,
11]. In Kotrikla et al. [
12], the possibility of reducing the overall emissions for the port of Mytilene (Greece) was discussed. The study estimated that the total energy requirements of the operating ships could be covered by a hybrid project that included four wind turbines (rated at 1.5 MW) and a 5 MW photovoltaic system. In general, it seems that only a hybrid renewable energy system can support the activities of a port, this aspect being highlighted in Wang et al. [
13]. The onshore and offshore wind resources from the vicinity of the Cartagena Port (Spain) [
8] were also taken into account, with the main conclusions of the study being that energy consumption can be covered from a renewable project even during the winter time when the demand is much higher.
The Black Sea is one of the most polluted seas in the world and this is largely due to the emissions produced by ships, which are a significant contributor to the present situation. On a larger scale, three major air pollutant routes seem to emerge: (a) the south-western part of the Black Sea and Bosporus toward the Aegean Sea; (b) the south-eastern part of the Black Sea towards the eastern part of Turkey; and (c) the west to east area over the north of the Caucasus Peninsula. In general, the movement of the air masses over the Black Sea area is quite complicated; however, it is estimated that the eastern coast of the basin will be more affected by these emissions, taking into account the strong winds that are coming from the northern part of the sea [
14]. Coincidence or not, the north-western part of the Black Sea is transited by over 300 ships that connect the Romanian ports with the ports of Ukraine, Bulgaria and the Bosporus strait. The traffic related to this region represents almost 40% of the total traffic in the Black Sea. In addition, a significant percentage of the ships used for maritime traffic in this region (36% of ships) were built before 1990 when no emission regulations were imposed. Among Romanian ports, Constanta can be definitely mentioned as being the most significant and is on the 5th position on a European level in terms of the volume of cargo processed by the port services. In the near future, a further increase in activity can be expected for this port [
15].
The Black Sea is also known for the wind conditions that can be used to power a wind farm, especially in the western part of this basin where the resources are more significant [
16,
17]. Onea and Rusu [
16] provide a comprehensive assessment of the Romanian wind energy potential related to this coastal environment. The results of the assessment are reported at 80 m height (above sea level) and, according to their findings, the wind speed significantly increases as we go from onshore to offshore (ex: Saint George from 6 to 7.2 m/s). The best sites to develop a wind farm are located in the north (Danube Delta) and south (Vama Veche), but these areas are quite isolated and the grid-connection will be challenging. If we look at the Constanta site, we notice that a wind project may become profitable if located 20 km from shore (at least).
Some aspects related to the novelty of the present work are highlighted next. This work represents one of the first studies considering the use of the ERA5 wind data for a renewable analysis. Estimation of the wind turbines number required to support the Port of Constant’s activity represents another element of novelty, as well as the expected Levelized Cost of Energy (LCOE) values linked to a wind project that may operate in this coastal environment. Besides these particular aspects, the present work can also represent a general framework for the evaluation of how the offshore wind turbines can reduce air pollution in coastal areas, in general, and in the vicinity of the ports, in particular.
In this context, the following research questions will be addressed as part of the present work:
- (a)
What is the best site to develop a wind farm near the Constanta Port?
- (b)
How many wind turbines will be required to support a cold ironing project?
- (c)
What is the expected cost of electricity generated from an offshore wind project?
4. Discussion
The negative environmental impact caused by ship navigation and port activities is a reality. At the same time, it is estimated that almost 50% of the entire shipping and port activities costs are associated with fuel. At this moment a 100% emission-free policy is impossible to implement, and more likely with the existing technology, a 20% to 30% reduction can be achieved [
10,
15]. Motivated by the fact that some important air pollutants are released only during the port activities (also known as hoteling), the idea was to investigate what it would take to develop a cold ironing project in the port of Constanta by using the local wind energy as the main supply source. In order to make such an estimation, a first step was to identify the level of air emissions from this port, the best sources of data being found in Nicolae et al. [
22]. By using the traffic values and the fuel consumption reported for the port of Constanta, the authors developed a computational tool that can predict the air emissions for the two main activities: (a) ship navigation; and (b) port activities. These results were discussed in
Figure 4, with the main conclusion being that air emissions are expected to escalate in the near future. The port of Constanta is a major source of pollution, but there is evidence that, in fact, some other coastal areas of the Black Sea (ex: Turkey) will be more affected [
14].
The reanalysis data represents one of the best sources of wind data for the marine environment and the ones coming from the ECMWF research institute are no exception. The ERA5 is a state-of-the-art database being frequently used to assess the wind conditions from a meteorological and renewable point of view [
40,
41,
42]. From the knowledge of the authors, at this moment there are limited (or no studies) that involve the assessment of the ERA5 wind data for the Black Sea basin, which could be considered an element of novelty. In Davy et al. [
43], the ERA-Interim wind dataset (that was replaced by ERA5) was evaluated for the entire Black Sea area for the time interval located between 1979 and 2004. According to the spatial map presented in this work (
U10 parameter), the best regions to develop a wind project are located in the Azov Sea and on the north-western part of the basin. In the present work, the Azov Sea is also highlighted, but in terms of the Black Sea, the best wind resources are associated with the centre part of this basin (ex: Crimea and Sinop Peninsula).
In Onea and Rusu [
16], the wind conditions from the vicinity of the port of Constanta (
U80; ERA-Interim) were evaluated by taking into account various distances from the shore, namely: 0, 20, 40, 60 and 80 km, respectively. For these points, the wind conditions go from 5.2 m/s (0 km) up to 6.9 m/s (60 km), values that translate to the
U100 parameter are similar to 5.29 and 7.02 m/s. From the analysis of the average values presented in
Figure 6, we can notice that the Constanta site seems to reveal values that are in the same range. The Areva M5000 (Turbine C) was considered in the mentioned study, with a capacity factor that goes from 26.3% (20 km) to 29.9% (60 km), respectively. Compared to these values (that are reported at 90 m height), the present work reports values in the range of between 22.2% and 34.9%, respectively. The present paper is focused on the same target area being a continuation of Onea and Rusu [
16]. Some elements of novelty and improvements that can be highlighted are: (a) ERA5 wind data was considered instead of ERA-Interim data; (b) additional wind turbines were used; (c) an estimation of the expected wind turbines required to power the port of Constanta was made by taking into account the air pollutions; (d) the expected LCOE values are indicated. The main purpose of a wind farm is to replace the pollutant emissions associated with fossil fuels consumption. By using Equation (5), it was possible to determine how many turbines will be required to cover the total emissions coming from the port activities, as it can be noticed in
Table 5. This is a theoretical case study, since in reality, it will be impossible to cover 100% of the energy needs through natural sources, and even if this were possible at the moment there is no infrastructure or interest to implement a cold ironing project at the port of Constanta.
As expected, the number of the turbines significantly drops as we go from Turbine A to Turbine C. By looking on the current European offshore market [
40] we can notice that for the marine environment the tendency is to use large scale wind turbines, so probably that Turbines A and B will no longer be considered an attractive solution. The estimated number of turbines is quite high and by looking on the largest projects (operational/under construction) we can make a comparison, namely: London Array—175 units; Hornsea 1—174 units; Gwynt y Môr—160 units; Greater Gabbard —140 units; Chenjiagang—134 units; Rampion—116 units; Anholt and Greater Changhua—111 units [
44]. In the best case (Turbine E), it will take almost 2.2 farms similar to the London Array project to cover the electricity demand from Site S3.
Another problem that needs to be taken into account is the number of ships that increase from year to year. In
Table 6 is presented this dynamic, by taking into account as a base a turbine that operated in 2010 and a similar one reported for 2019. The values (in %) indicate the increase in the number of turbines required to cover the air pollution from the port of Constanta. For this 10-year interval, the values increase on average by 50%, being reported percentages in the range of: Turbine A (43–53.8%); Turbine B (46.8–57.4%); Turbine C (42.3–54.8%); Turbine D (44.2–56.8%); Turbine E (43.6–57.4%).
Besides the environmental aspects, the economic aspects are also important, this being revealed by the LCOE indicator. Usually a 20-year interval is required to calculate this parameter so the entire ERA5 wind data were considered (from 2000 to 2019), including the following values: CAPEX = 4500 USD/kW; OPEX = 0.048 USD/kWh; inflation = 2% per year; ageing of the systems = 1.6% per year. In the end, a cost-scaling factor was applied in order to make a difference between each site [
38].
Figure 13 presents these results, from which it can be noticed that Turbines D and E reveal similar values.
According to these results, Site S1 should be avoided taking into account that it reports much higher LCOE values (range of 0.32 and 0.39 USD/kW). The most promising sites are N3, C2 and S3 where a minimum of 0.23 USD/kW may be reported in the case of Turbines A and C, respectively. From this point of view, Turbine B (Siemens SWT 3.6) reveals much lower performances, being followed by Turbines D and E, which may report a minimum of 0.25 USD/kW and a maximum of 0.36 USD/kW near Site S1. By looking on the EU expected targets [
35] for the year 2025 (0.11 USD/kW) and for 2030 (0.08 USD/kW), we can notice that the minimum values reported at the Constanta sites are not even close to these indicators. This provides a rough estimation over the economic viability of an offshore wind farm that may operate in the western part of the Black Sea, this being one of the first analyses of this kind from the knowledge of the authors.
Finally, some considerations concerning the foundations will be provided at this point. This is because with the new generation of wind turbines (10 MW or greater) the offshore wind industry is already running into the problem that existing foundation types (piles) are reaching their limits in “workable size”. Obviously, the foundation type depends on the soil conditions and typically a foundation makes up to 30% of a wind turbine cost, even at 20 m depth. From this perspective, in order to implement wind farms in the target area, additional studies concerning the soil conditions and identification of the most appropriate solutions for foundation should be carried out. Additionally, an important issue in designing the foundation is represented by the current regime. This is because in the nearshore of the Black Sea, and especially in its western side, significant marine and nearshore currents are present [
45,
46].
5. Conclusions
In the present work, a general assessment of the wind conditions from the vicinity of the port of Constanta (Black Sea west) was carried out, by taking into account the performance of some commercial wind turbines as well. The main idea was to see how a wind farm could support a cold ironing project that may be developed in this region, taking into account that the air pollution coming from the berth activities is a reality.
First, based on the 20 years of ERA5 data, it was possible to provide a general picture of the wind conditions over the entire Black Sea area, gradually focusing on the western part and the Constanta sector. Although there are studies focused on different geographical areas, suggesting that there is no difference between onshore and nearshore wind conditions, according to these results it is clear that an offshore project will achieve better results. Apart from the performance of various wind turbines, some other important indicators were taken into account such as the CO2 emissions and LCOE.
Going back to the original research questions, the following answers can be provided:
- (a)
From the annual distribution of the AEP, we can definitely say that there is a significant gap between the nearshore sites (10 km) and the offshore ones exceeding 30 km. An offshore farm will be more recommended for larger projects since these can be assembled without disturbing the port of Constanta activities;
- (b)
The number of turbines required to cover the electricity demand from the port of Constanta (hoteling) was estimated to be between 385 and 1741 units, depending on the site and the turbine rated capacity. Even in an optimistic scenario, it will take three or four large wind projects to cover this demand, so probably a hybrid system will be more appropriate. This is only one part of the story, because, at present, it seems that every 10 years, the electricity demand of the port of Constanta increases by at least 40%;
- (c)
The best LCOE value reported for the Constanta area is close to 0.23 USD/kW, which easily exceeds the EU expectations for the near future. A renewable energy project is not a cheap solution, this being one of the reasons why most of the countries are applying a tax deduction for this type of investment. From an economical point of view, it is expected that a larger offshore project will be a better alternative to a similar one located onshore.
Looking at the current results we can mention that, in fact, the wind conditions are relatively low, this aspect is reflected by the capacity factor of the turbines (<40%) comparable to the onshore systems. Although the wind conditions are reported at 100 m height, we notice that the average wind speed can go up to 8 m/s, but even so, these conditions are below the rated wind speed of the turbines (ex: Areva M5000—12.5 m/s). This means that most of the time the wind turbines selected will not operate at full capacity, and as a consequence, the LCOE index has higher values. In order to increase the efficiency of a wind project, it will be more indicated to consider turbines defined by lower-rated speed, such as the MHI Vestas’ 10 MW turbine (Vestas, Aarhus N, Denmark) that will be defined by a rated wind speed of 10 m/s.
The cold ironing concept is emerging and slowly some major ports are taking the initiative to shift this sector to a more sustainable future. Definitely, there are a number of significant challenges that need to be overcome, including the old technological systems that need to be redesigned and the investments required to update a port infrastructure. Finally, it is difficult to predict what will happen in the future because the wind and shipping industry is evolving very fast, but certainly, a cold ironing project located on the port of Constanta will be a major gain for the entire Black Sea ecosystem.