In a list, capacities of power plants, as such, do not reveal much information. However, once the list has been further completed and distributed over time and space, it will be possible to find and see patterns and tendencies. Through data analysis, it is possible to gain deeper insights into the global power sector. When analysing the data, the focus is
on identifying trends of three main types: technological trends, temporal trends and regional trends.
Technological trends focus on the development of a given technology from a global perspective over time. The identification and interpretation of technological trends provides insights regarding the maturity and competitiveness of energy technologies and energy sources within the global power sector. In the case of relatively new technologies, such as solar PV and wind, it is possible to witness the beginning of their commercial deployments. For the well-established technologies, the trends in installation can reveal, for example, how their presence changes over time. Specific details about these trends are presented in Chapter 3.
Temporal trends focus on the local development of the mix of technologies over time. It takes into account all the technologies in use within a country. The identification of local temporal trends provides information on the transition state and how the technologies interact with each other within the same geographic region. For example, Figure 8 clearly illustrates a shift in the power generation technologies of Japan over time. In the 1960s and early 1970s, oil-fired capacities were dominant. During the 1970s, 1980s and early 1990s, nuclear-based capacities were the majority, while from the 1990s and the 2000s gas-fired capacities were dominant. From 2008 onwards, solar PV and wind capacities have the largest share of the installations. From before the 1940s and during this transition process, hydropower capacities maintained a quasi-stable share of installations.
Regional trends provide a wider regional perspective of the temporal evolution. Larger regions or clusters of adjacent countries also provide unique information. Adjacent territories considered as a group tend to have access to similar resources, renewable and non-renewable. However, across borders, the structure of the power sectors can be very different. Larger regions can also generate and trade electricity across borders, making a broader view more representative of the wider power sector infrastructure in play. As an example, Figure 9 shows the profile of installations of the European continent. The European continent is highly grid interconnected. Therefore, neighbouring countries, which have quite different profiles of their power capacities, can still import, export and use energy generated in other country. In this way, for instance the energy generated by hydropower in Norway, the wind farms of Denmark, or the solar PV plants of Germany can ultimately be used for example in France or Belgium, two countries that currently greatly rely on nuclear capacities.
Figure 9: Yearly power plant installation profile of the European continent as an example for regional analysis.
From Figure 9, a regional analysis reveals the rise and fall of installations of coal (from the late 1950s to the early 1990s) and nuclear power (from the early 1970s until the early 1990s), while depicting an ongoing dramatic growth of wind (from the mid-1990s), solar PV (from the mid-2000s) and bioenergy (from the late 1990s). Gas-fired installations seem to be on the rise, particularly noticeably from the 1990s onwards, while hydropower installations maintain a significant level of commissioning over the years.
Detailed data analysis facilitates not only the understanding of historical developments, but also provides a solid foundation for modelling projections of how it may evolve, as presented for instance in Bogdanov et al., (2019) and Publications V, VI and VI.
Moreover, data analysis can be performed in a multitude of ways, defining different distribution groups. For example, Publication VII explored the influence of thermal power plants on water bodies through cooling and linked thermal power plants to major rivers. Therefore, the data available can and have been used in the past for new analytic and modelling methods, facilitating power-sector-related research.
3 Trends of the power generation technologies
In this chapter, a short analysis of each generation technology present by 2014 is conducted to reveal the development and historical deployment of these technologies. A short summary of their history and background is also presented. Moreover, some technologies are grouped based on their historical trends, particularly those that seem to be on the rise and those that present no clear trends.
3.1
Hydropower: Old, yet forever youngHydropower presents a unique feature. Hydropower stations tend to be endlessly refurbished, as dams and power stations of over 100 years old still operate nowadays. In fact, 4.2% of the currently operating hydropower capacities were initially commissioned in and before 1940, as shown in Figure 10. It may seem low, but the share of capacity operating before 1940 for hydropower is higher than any other technology by a factor of over 400. Although all the capacities commissioned before 1940, hydropower or other, have naturally gone through several rounds of refurbishment and updates, it is not a coincidence that hydropower capacities are kept in operation for longer than others.
According to IRENA (2012), the costs of electrical and mechanical componentsneed the most maintenance and renovation, which constitute only around 30% of the total capital investment. In this study, hydropower capacities are divided into three categories:
reservoir-based, RoR and pumped-storage. The latter is not a generation technology per se; however, this information was provided by the original source, and therefore, an analysis was possible and thus carried out. In addition, pumped-storage hydropower is structurally very similar to reservoir-based hydropower. Together, all hydropower capacities represent roughly 20% of the global installed power capacities by 2014.
Figure 10: Development of hydropower installations over time from 1940 to 2014.
Reservoir-based hydropower has several advantages: it is extremely flexible in its operation and highly scalable, it can be continuously renovated to work for over 100 years, which drives the energy production cost down, and it requires low maintenance and operates on a carbon neutral basis (even though there are carbon emissions associated with the construction and commissioning). The world’s largest power stations are hydropower plants, with the Three Gorges Hydropower Station in China being the largest of them all with 22.5 GW of installed capacity. This is 3.2% of the global installed reservoir-based hydropower capacities by 2014 in a single power station, which speaks for the scalability of the technology. China has 25% of the total capacity installed by 2014, and the top eight countries have 63.5% of the total. As almost 40% of the capacity is distributed over the rest of the world, it can be seen that the use of the resource is quite widespread.
However, with the advantages come several disadvantages. These disadvantages can be of financial, social, environmental or logistic nature. For example, it is widely shown that hydro reservoirs affect the hydrological systems of the river, adding barriers to the nutrients and migratory fish species. From the financial perspective, Sovacool et al.
(2014) found, after a survey of over 400 hydroelectric projects, that reservoir-based dams surpass by an average of 60% of the original estimated time for construction and generate around 40% excess cost. Additionally, as it is a geographically localised resource, it often requires hundreds or even thousands of kilometres of transmission lines, generating extra expenses and losses.
Naturally, the social challenges of hydropower are not minor. For example, Tilt and Gerkey (2016) highlight the extent of the issue for China. China hosts about half of the world’s large dams, and as a consequence, has been forced to deal with around 15 million involuntary displacements of people. Worldwide, this number is estimated historically to be as high as 80 million involuntary displacements by the end of the year 2000 (WCD, 2000).
However, the impact of hydropower depends on the mode of operation of the power plant.
Basically, there are two main modes of operation for hydropower production: reservoir-based and RoR. Pumped-hydro stations are, in a way, reservoir-reservoir-based hydro stations with the capability of reverse operation and are an energy storage infrastructure rather than power generation power plants.
3.1.1 Reservoir-based hydropower
Reservoir-based hydropower plants, as the name implies, consist of a large physical barrier or dam, creating large artificial water reservoirs in order to gain head height (and thus power) and to regulate the operation of the power station. Reservoir-based hydropower has several advantages. Water reservoirs, in general, have played an important role long before hydropower was an option. In fact, hydropower reservoirs
often serve additional (and sometimes several other) purposes, such as agricultural irrigation, recreation, municipal water source or fishing. From the power production perspective, reservoirs allow a quite high degree of flexibility. Despite this, the historically perceived low cost of operation of a hydropower station often meant
“baseload” operation in the past. Nowadays, with the increase in fluctuating renewable power sources, reservoir-based hydropower starts to shift to a balancing role.
These advantages, among others, explain the high prevalence of reservoir-based hydropower among the hydropower technologies, accounting for almost 70% of the capacities by 2014 (shown including the pumped-hydro in Figure 10). However, the most severe cases of environmental and social impacts are associated with reservoirs. Artificial water reservoirs, by default, are meant to cover land areas, whether those areas previously served some human-related purposes (e.g. habitation, agriculture or industry) or as natural reserves. These land losses are sources of social issues in the case of land in human-related use, and environmental impacts in the case of loss of natural reserves. In addition, as mentioned previously, the physical barrier that the dam creates has a negative impact both on the hydrological system and the paths for migratory fish species. Because of these and other negative impacts, new large hydropower reservoirs can be quite controversial, as further detailed in Publication IV.
In Publication IV, modelling of the energy sector of Sub-Saharan Africa showed that distributed renewable energy sources would produce a noticeable reduction to the cost of electricity while allowing more efficient electrification of the continent. Moreover, significant environmental drawbacks can be avoided by choosing not to tamper with the Congo river basin.
3.1.2 Run-of-River hydropower
RoR hydropower uses a different strategy for power production. RoR implies taking advantage of the water flow in the rivers, by diverting a fraction of the flow of a river through a weir into the turbine. Often, there is a middle step of a small reservoir in order to stabilise the flow into the turbine and reduce the amount of sediments going into the turbine. Thus, RoR, by not directly interrupting the water flow of a river and not flooding large areas, causes relatively low environmental and social impacts when compared with reservoir-based hydropower.
As shown in Figure 10, RoR hydro accounts for approximately 30% of the global hydropower capacities, highlighting the importance of RoR in the global power system.
However, it also has some disadvantages. Because it depends on the concurrent flow of the river, it is susceptible to seasonal changes and thus operates for lower full load hours than reservoir-based hydropower. In addition, the small reservoir of water is normally capable of storing between two hours and two days of water for turbine operation at best, and thus, its operation is of uncontrollable fluctuating nature in contrast to the flexibility of reservoir-based hydropower.