1. Introduction
In recent times, with the growing interest in renewable energy and the decarbonisation of electrical energy systems, the revival and upscaling of energy storage systems (ESS) has become indispensable. On its own, renewable energy (e.g., wind and solar) is often unpredictable and lacks load-following flexibility, and it cannot be turned on when needed (Barbour et al., 2016). The more widely known ESS in electricity production portfolios include pumped hydro energy storage (PHES) (Guezgouz et al., 2019), compressed air energy storage (CAES) (Budt et al., 2016), hydrogen storage systems (Karellas and Tzouganatos, 2014), lead batteries (May et al., 2018), flywheels (Mousavi G et al., 2017) and supercapacitor energy storage (Kadri et al., 2020). Pumped hydro energy storage and CAES are most common in off-grid and remote electrification applications. Nevertheless, PHES is considered the most promising system for handling large electricity networks, and worldwide, hundreds of PHES plants were installed in 2018 with capacities of approximately 160.3 GW (an increase of 1.9 GW from 2017) (IHA, 2018a).
Typically, PHES comprises one upper and one lower reservoir (closed-loop system) or one upper reservoir and a river, sea lake or other body of water as a lower reservoir (open-loop system). It assists with energy time-shifting and is characterised by a long lifespan (50–100 years) (Guittet et al., 2016), high trip efficiency (70–87%) (Rehman et al., 2015) and low maintenance costs (Mahmoud et al., 2020). Initially, PHES was introduced in the alpine regions of Europe in the 1890s (Javed et al., 2020), and a cumulative interest in its development was seen after World War II, due to the increasing demands for electricity by the post-war population during the period of economic recovery. However, most PHES systems were built between the 1960s and 1980s (Deane et al., 2010), and by 2005, over 200 PHES schemes had been installed and were operating globally (Chen et al., 2009). Later, the development of these systems was slowed, following concerns by environmental consortiums, which repelled the major investments. However, ESS, including PHES, have recently been resurrected for numerous reasons, such as increasing demand for electricity due to rapid urbanisation; the growing inclusion of renewables in energy portfolios (Katsanevakis et al., 2017), especially wind and solar; power quality and stability challenges; and ever more stringent environmental requirements (Chen et al., 2009). Researchers have found that opportunities and challenges run in parallel with developmental projects such as PHES, and they become more complex when they are not being discussed, prioritized or answered on time (Ali et al., 2020).
Researchers are continually contributing to enriching the information on PHES and reviewing the historical and geographical perspectives, technological advancements, opportunities, and barriers. For example, Deane et al. (2010) examined the techno-economic drivers for existing and proposed PHES and inferred that developers of liberalised markets are interested in repowering, enhancing or building ‘pump-back’ PHES. However, the study's scope was limited to the European Union, Japan, and the United States. Yang and Jackson (2011) studied the historical development of PHES, encompassing the controversies, disputes, challenges and prospects in the United States. Zeng et al. (2013) shared knowledge on the capacity, distribution and developmental barriers of existing and proposed PHES facilities in China. Ardizzon et al. (2014) analysed the prospects of PHES for sustainable development, studying planning- and management-related challenges. In 2015, Rehman et al. (2015) reviewed globally existing PHES, recent technological developments in PHES and the hybrid version of PHES with wind and solar energy resources. This study found that PHES is technologically suited to islanded grid applications. Subsequently, existing operational trends in PHES and the associated challenges were studied by Pérez-Díaz et al. (2015). This study also discussed the capacity of PHES to provide supportive services in deregulated and centralised electricity markets. Barbour et al. (2016) explored the historical perspectives on PHES in various electricity markets and the accessible rewards for PHES investors, policymakers and developers. They also briefly discussed public sector investments. Guittet et al. (2016) reviewed PHES evolution, its usage and the driving forces behind its construction, in chosen countries.
However, having analysed the published review papers, it was realised that there is still room for improvement in the reporting of contemporary drivers for and barriers to the development of PHES, covering technical, environmental, social, and economic aspects, which might be useful to the scientific community and related stakeholders or industries. Most of the previously published papers on PHES have covered specific themes or territories and are narrative or traditional literature reviews. Moreover, these narrative reviews predominately discussed aspects of PHES from a theoretical or contextual point of view only and rarely provided concrete and generalisable findings related to the drivers, enablers, and barriers of PHES. Whereas, the systematic review uses rigorous methodological approaches (Gregory and Denniss, 2018). Therefore, this study intends to collect recent findings systemically and coherently from 2000 to 2020 on the prevailing drivers for and barriers to PHES in techno-environmental and socio-economic domains, for both developed and developing countries around the world. A study on this subject involving both domains has not been conducted before. Along with articles and conference proceedings, the search was expanded to the reports published by various organisations or industries which had been mainly ignored in the reviewed articles.
So, the overarching research question of this review is: ‘What are the prevailing techno-environmental and socio-economic drivers for and barriers to PHES development? The study had two related subsidiary questions: (1) What are the more significant drivers and barriers? and (2) What are perceived differences in the importance of drivers and barriers in developing and developed countries?
2. Materials and method
2.1. Overview of the systematic literature review procedure
Following the PRISMA guidelines (Liberati et al., 2009), the methodology of this review study was developed as presented in Fig. 1.
Fig. 1It encompasses the evidence available on the prevailing drivers for and barriers to the development of PHES to convey the breadth and depth of PHES developments around the world. The systematic literature review was conducted based on the procedure of Can Ĺžener et al. (2018), who systematically identified multiple drivers and barriers to understand the diverging paths of renewable energy deployment, and Mayeda and Boyd (2020) that studied public perceptions about hydropower in a systematic fashion. A search strategy was formulated to systematically target peer-reviewed articles according to the identification methods outlined by (Harari et al., 2020). The search resulted in 1,010 articles from Scopus and 4,583 articles from WOS, a total of 5,593 articles. Only 178 articles were judged relevant for eligibility assessment, where they were further assessed for inclusion or exclusion from the final content analysis and synthesis of the data based on the adapted procedure (Salim et al., 2019). Following this was a further filtering method that returned 64 records (Supplementary Table S2) that were eligible for content analysis to synthesize the prevailing drivers for and barriers to PHES applications. The eligible records were studied in detail and were profiled according to (Painuly, 2001), which provides a specific discourse on the categorisation of the drivers for and barriers to diffusing renewable energy, whereas (Deane et al., 2010), broadly encompasses the techno-economic review of the hydro storage technologies. The details related to the systematic review protocol, the method adopted for the identification of relevant studies, the analysis and coding of the identified records are all provided in the Supplementary Material file (S1.1 to S1.4).
2.2. Categorisation of drivers and barriers
The drivers and barriers are clustered into techno-environmental and socio-economic factors due to the partly overlapping sub-categories. Techno-environmental factors are those that reflect the positive and negative impacts of the employment of PHES due to the technical and environmental reasons e.g., natural topography, clean energy, land use, vegetation clearing etc. The socio-economic factors are the those that reflect the positive and negative impacts of the employment of PHES due to the social and economic reasons e.g. job opportunities, revenue generation, resettlement issues, cost overrun etc (Hossain et al., 2018). Therefore, the drivers were clustered as techno-environmental drivers (TEDs) and socio-economic drivers (SEDs), and the barriers were clustered as techno-environmental barriers (TEBs) and socio-economic barriers (SEBs).
2.3. Method for creating global weighting
Weight scoring prioritization is needed to delineate the respective weights of each criterion. Therefore, a global weight analysis procedure was implemented similar to the analytic hierarchy process (AHP). This procedure has been adopted for the identification of criteria weights for the site assessments of rubber wood biomass (Waewsak et al., 2020a), and for assessing renewable energy-based power plants (Waewsak et al., 2020b). In this study weight analysis was conducted to systematically determine the relative importance of the identified drivers and barriers. The techno-environmental and socio-economic factors were combined to understand the separate relative importance of drivers (TEDs and SEDs) and barriers (TEBs and SEBs). The number of studies on the respective factor or item was used as an input to the calculation of the relative weight, where the global weight was calculated by multiplying the relative weights of the hierarchised theme, factors, and items.
2.4. Comparison between PHES study completed in developed and developing countries
Lastly, a comparative analysis was conducted to understand how the drivers and barriers to the development of PHES differ between developing and developing countries. Whereas the country's economic classification was considered according to the world economic situation and prospects provided by the United Nations that classifies them into three broad categories: developed economies, economies in transition and developing economies (United Nations, 2019). Studies considered during this research were based on either developed or developing economy settings only, the economies in transition was therefore invalid.
3. Results and discussion
3.1. Assessment of study characteristics
The identified records were imported to the Mendeley Reference Manager Software, and with the removal of 1,010 duplicates, 4,026 articles were systematically examined. These were narrowed to 64 records (1.589% of the examined records) to be included in this review study. Readers seeking a detailed assessment of the reviewed study characteristics (i.e., publication trends, geographic trends, research subject and methodological trends etc.) are referred to the Supplementary Material file (S2.1 and S2.2).
3.2. Categorisation of PHES drivers
As a result of a full review of the included studies, several techno-environmental and socio-economic themes emerged as main drivers for PHES development. The drivers under each techno-environmental and socio-economic category of factors were sub-divided and clustered by theme. The following sections describe the engendered positive factors for PHES, whereas the sub-themes follow the precedence ranking based on the number of times they were mentioned in the reviewed studies.
3.2.1. Techno-environmental drivers
Fifty-one of the reviewed studies discussed various promoting factors under the cluster of TEDs, which are described in this section (see Table 1).
Table 1. Categorisation of drivers to the deployment of PHES applications.
| Main theme | Code | Factors | NoS | Code | Items | NoS |
|---|---|---|---|---|---|---|
| Techno-environmental drivers (51 studies) | TED1 | Grid resilience | 42 | TED1.1 | Support renewables | 38 |
| TED1.2 | Grid stabilization | 20 | ||||
| TED1.3 | Black and quick start | 12 | ||||
| TED1.4 | Ancillary services | 8 | ||||
| TED1.5 | Support non-renewables | 5 | ||||
| TED1.6 | Solution to grid congestion | 2 | ||||
| TED2 | Utility-scale storage | 35 | TED2.1 | Daily storage | 33 | |
| TED2.2 | Seasonal storage | 5 | ||||
| TED3 | Sustainability | 24 | TED3.1 | Clean Energy | 21 | |
| TED3.2 | Long lifetime | 6 | ||||
| TED4 | Landscape characteristics | 23 | TED4.1 | Conventional hydro or lower reservoir | 13 | |
| TED4.2 | Mountain topography and existing rivers/streams | 9 | ||||
| TED4.3 | Coal mines | 4 | ||||
| TED5 | Auxiliary services | 5 | TED5.1 | Flood and sediments control | 4 | |
| TED5.2 | Breeding place for amphibians | 1 | ||||
| TED5.3 | Groundwater recharge and replenishments | 1 | ||||
| Socio-economic drivers (30 studies) | SED1 | Energy arbitrage | 18 | SED1.1 | Revenue generation | 12 |
| SED1.2 | Cheap electricity | 11 | ||||
| SED2 | Rural development | 10 | SED2.1 | Job opportunities | 6 | |
| SED2.2 | Business opportunities | 6 | ||||
| SED2.3 | Quality of life for rural population | 4 | ||||
| SED3 | Proximity and cross-functional characteristics | 8 | SED3.1 | Nearby demand centre | 5 | |
| SED3.2 | Irrigation and drinking water | 3 |
*Note: NoS (Number of Studies) – all tables to consider; Extended version of this Table with references at item level is supplied in the Appendix A (Table A1).
3.2.1.1. Grid resilience (TED1)
The reviewed studies mentioned grid resilience as the main driver behind the development of pumped hydro in current electricity markets. The development of PHES is highly significant to the modern electricity networks that are transitioning to renewable power systems (Ghorbani et al., 2019). Pumped hydro storage has the potential to ensure the grid balancing and energy time-shifting of intermittent renewable energy sources, by supplying power when demands are high and storing it when generation is high. Moreover, ancillary support such as frequency and voltage modulations, the ability to track and adapt to drastic load changes and black start to solve grid congestions are believed to be significant technical drivers behind the active development of PHES by the reviewed studies. Typically, a PHES acts as a reserve powerhouse that quickly manages unexpected fluctuation caused by either demand or generation, due to its excellent manoeuvrability in operation. Hydropower can move from zero to full power within minutes, and it is vital to avoiding system-wide collisions and recovering from emergencies and disasters (Makarov et al., 2005). The PHES plays an integral complementary role in regional grids and cross-regionally interconnected grids in addition to their role in local grids; one study argued that electric grid congestion from the north to the south of Germany was the main reason for its development of a pumped hydro facility (Deane et al., 2010). In some countries, PHES is strongly correlated with the development of nuclear (France and Japan) and coal (USA and China) power plants since these plants are inflexible sources of baseload generation that continuously generate electricity. Therefore, in such scenarios, PHES offers vital storage capacity for energy when demand is low, especially during the night. Researchers thus believe grid resilience to be the driving determinant to embracing pumped storage around the world.
3.2.1.2. Utility-scale storage (TED2)
Pumped hydro provides the largest and most mature form of energy storage compared to the energy storage devices currently on the market (Koohi-Fayegh and Rosen, 2020). Its development will increase in the coming years due to the growing concern of climate change and renewed interests in renewable energy. Pumped hydro energy storage could be used as daily and seasonal storage to handle power system fluctuations of both renewable and non-renewable energy (Prasad et al., 2013). This is because PHES is fully dispatchable and flexible to seasonal variations, as reported in New Zealand (Kear and Chapman, 2013), for example. When it is used for intra-day balancing, the surplus electricity from baseload sources such as coal and nuclear is usually used for pumping at night and to reinforce generation capacity during the day when demand is high. On the other hand, some types of PHES could also be used as weekly or monthly storage if they are economically justified (Fitzgerald et al., 2012). Overall, these daily and seasonal storage choices for utility-scale applications are one of the growing reasons for the worldwide implementation of PHES.
3.2.1.3. Sustainability (TED3)
Another triggering factor for using pumped-storage plants, described by the reviewed studies, is their sustainability characteristics: clean energy and long lifespan. The development of PHES promotes the use of renewable energy and directly eliminates dependency on non-renewable energy such as coal power, which is still in use. Moreover, substituting PHES consolidated with a renewable source can significantly lower anthropogenic emissions such as sulphides, nitrogen oxides, particulates, carbon monoxide and other greenhouse gas pollutants from unclean electricity generation (Ming et al., 2013). Arguably, carbon dioxide (CO2) contributes most to greenhouse gases that cause global warming and the greenhouse effect. Therefore, deploying PHES and reducing CO2 means achieving low-carbon economic development that also fulfils the Paris Agreement on climate change (Fan et al., 2020). The estimated lifetime of pumped hydro is anywhere between 40 and 80 years (Aneke and Wang, 2016), while some studies state this lifetime is up to 100 years (Deane et al., 2010), which means it is highly reliable and a one-time investment that is of great interest to investors and policymakers seeking business opportunities.
3.2.1.4. Landscape characteristics (TED4)
Pumped hydro storage typically requires two reservoirs (Chen et al., 2016), and the reviewed studies have determined that an existing dam, abandoned coal mine or lake can serve as either the upper or lower reservoir. This can be environmentally favourable because of the reduced land-use conflicts (Sovacool et al., 2011) and clearing of vegetation required, and it, in turn, reduces construction time and costs. The reviewed studies also described the importance of natural topography and water resources as significant driving factors. A favourable landscape topography provides the technically required head difference and slope between the two reservoirs of pumped energy storage, such as the topographies across most European countries such as Croatia and Austria (Deane et al., 2010); otherwise, artificially developing the required head and slope results in increased construction cost. Water resources in proximity, such as rivers or streams, are useful for the first filling of a reservoir or to replenish water lost due to evaporation or leakage. On the other hand, transportation using water tankers might not be environmentally or economically feasible.
3.2.1.5. Auxiliary services (TED5)
The variety of auxiliary services linked to PHES which emerged during this research include flood and sediment control, amphibian breeding grounds and groundwater recharge and replenishment. The reviewed studies perceived the development of pumped hydro storage as an opportunity to control flood and sediment that usually occur due to natural land degradation and building of settlements upstream (Munthali et al., 2011), as the reservoirs store water to reduce the impact of floods and sediments (Hunt et al., 2017) and do not let them pass to the vulnerable settlements downstream. A sophisticated PHES system can also be home to amphibians and water-related insects. It can positively influence the microclimate and develop the landscape, although most of the studies investigating hydropower developments selected locations where habitats and ecosystems were fragile. Another study (Saraf et al., 2001) suggested that pumped hydro could be environmentally useful, since it provides an opportunity to recharge and replenish groundwater, which is an important process in sustainable groundwater management.
3.2.2. Socio-economic drivers
Twenty-five of the reviewed studies discussed various socio-economically stimulating factors for the development of pumped energy storage under the cluster of SEDs, which are described in this section (see Table 1).
3.2.2.1. Energy arbitrage (SED1)
The reviewed studies suggest that pumped hydro is a strong source of revenue generation (Deane et al., 2010). The pumped hydro utilises the cheap electricity from the utility grid during off-peak hours to transport water uphill. This water would be plunged during peak hours to generate electricity to be sold at higher rates. This method of trading on energy arbitrage opportunities strongly attracts energy stockholders. Over the years, with improvements in technology, the cost of electricity from renewable sources has been plummeting, and these sources are believed to be even cheaper than fossil fuels (Ram et al., 2018). This has been true for the pumped hydro technology, although capital costs are still higher (this is usually site-specific). However, cheap operation and maintenance costs make it lucrative for long-term commercial use in addition to supplying cheap electricity.
3.2.2.2. Rural development (SED2)
Developmental projects such as PHES usually create numerous job opportunities, especially for locals, during construction and operation. This attracts local populations however, opposition for various social or political reasons is common in a developmental project, therefore the rural development has great social importance, and this has been reported in the reviewed studies (Cebotari and Benedek, 2017). The reviewed studies further highlighted the theme of business opportunities from hydro projects, mostly in developing countries, as a significant social driving factor. These business opportunities include uplifting tourism (as more people might visit project sites for academic and recreational purposes), fishing or fish farming and property rentals in the proximity of the project sites. Moreover, the local contractors may also receive a fair share for providing materials and other necessary services during the construction phase. Various types of economic prosperity other than job and business opportunities accompany development projects of PHES in rural areas, as the location for PHES is often in remote areas that lack basic facilities such as road and infrastructure, schools, and hospitals. Therefore, the development of PHES reciprocally improves roads and other infrastructure and recreational facilities, and the sharing of revenues and the payment of local taxes are positive economic indicators for rural development.
3.2.2.3. Proximity and cross-functional characteristics (SED3)
Favourable and socially acceptable site conditions allowing a configuration of PHES plants and the construction of integrated grid systems in close proximity would significantly reduce power transmission losses, such as anywhere in the range of 8–15% (Glasnovic and Margeta, 2011), as excerpted from the reviewed studies. The studies reported various other cross-functional abilities, such as water for irrigation and drinking, especially from the run of river-type PHES plants, as a possible driver for the construction of a pumped hydro project in far-off locations.
3.3. Global weight analysis results of the identified drivers
Among the drivers, pumped hydro storage as daily storage (TED2.1), under the utility-scale storage cluster, was the most important driver, with a global weight of 0.148. Pumped hydro's ability to generate revenue (SED1.1), under the energy arbitrage cluster, was the second most prominent driver, with a global weight of 0.096. This is followed by pumped hydro's ability to support renewable energy sources (TED1.1), under the grid resilience cluster, with a global weight of 0.091. Fig. 2 shows the determined global weight for TEDs and SEDs that are placed in a precedence rank with specified colour codes for TEDs (dark blue) and SEDs (dark grey). Where the x-axis represents the drivers at the item level and the y-axis represents the obtained global weight of the drivers. The details on the individual and global weights of the driving factors and items are provided in Appendix B (Table B1).
Fig. 23.4. Comparing PHES drivers from developed with developing countries
The research findings revealed that most drivers for PHES application are identical in developed and developing countries, except that the number of times they are mentioned is uneven for each cluster. Fig. 3 provides comparative knowledge related to the TEDs and SEDs in developed versus developing countries. In this figure, the number of studies on TED1 (grid resilience), TED3 (sustainability), TED4 (landscape characteristics) and SED1 (energy arbitrage) in developed countries were noticeably higher than those in developing countries. These results imply that developed countries are persuaded by the integration of pumped hydro based on renewable energy into existing energy systems for cleaner power production. These countries are also motivated to achieve grid stability, exploiting existing reservoirs for PHES and its long lifespan and deploying it in their territories for techno-environmental reasons. Revenue generation and supplying cheap electricity to the population are arguably the core SEDs for the development of pumped hydro storage in developed countries compared to developing countries.
Fig. 3However, studies from developing countries are more attentive towards drivers such as TED2 (utility-scale storage), TED5 (auxiliary services), SED2 (rural development) and SED3 (proximity and cross-functional characteristics). This shows that, compared to developed countries, developing countries are more attracted to pumped hydro development for its energy storage, flood and sediment control and groundwater recharging for techno-environmental reasons. The uplifting of rural populations through job and business opportunities, establishing electricity facilities in close proximity to these populations and achieving access to irrigation and drinking water sources are the endorsing socio-economic factors behind PHES development in developing nations. Further, see Appendix C (Table C1) on PHES driver comparison for developed versus developing countries.
3.5. Categorisation of PHES barriers
As a result of a full review of the included studies, several techno-environmental and socio-economic themes emerged as main barriers to PHES development. The barriers under each techno-environmental and socio-economic category of factors were sub-divided and clustered by theme. The following sections describe the engendered negative factors for PHES, whereas the sub-themes follow the precedence ranking based on the number of times they were mentioned in the reviewed studies.
3.5.1. Techno-environmental barriers
Forty-seven of the reviewed studies discussed various inhibiting factors under the cluster of TEBs that either slow or completely block the development of PHES. The themes identified are presented in this section (see Table 2).
Table 2. Categorisation of barriers to the deployment of PHES applications.
| Main theme | Code | Factors | NoS | Code | Items | NoS |
|---|---|---|---|---|---|---|
| Techno-environmental barriers (47 studies) | TEB1 | Lacking infrastructure | 26 | TEB1.1 | Transmission lines | 23 |
| TEB1.2 | Roads | 15 | ||||
| TEB1.3 | System integration | 1 | ||||
| TEB1.4 | Lacking surplus power | 1 | ||||
| TEB2 | Landscape topology | 25 | TEB2.1 | Head | 25 | |
| TEB2.2 | H/L | 13 | ||||
| TEB2.3 | Slope | 10 | ||||
| TEB2.4 | Landfill works | 5 | ||||
| TEB3 | Land acquisition challenges | 21 | TEB3.1 | Land use | 16 | |
| TEB3.2 | Vegetation clearing | 5 | ||||
| TEB3.3 | Land ownership | 2 | ||||
| TEB4 | Water issues | 20 | TEB4.1 | Availability | 12 | |
| TEB4.2 | Quality | 6 | ||||
| TEB4.3 | Leakage loss and evaporation | 5 | ||||
| TEB4.4 | Local supply | 3 | ||||
| TEB4.5 | Hydrological effects | 2 | ||||
| TEB4.6 | Oxygen loss in water | 1 | ||||
| TEB5 | Geological faults | 16 | TEB5.1 | Seismic activities | 16 | |
| TEB5.2 | Landslide | 1 | ||||
| TEB6 | Biodiversity loss | 15 | TEB6.1 | Aquatic life and spawning | 12 | |
| TEB6.2 | Birds loss | 3 | ||||
| TEB6.3 | Temperature change | 1 | ||||
| TEB6.4 | Soil erosion | 1 | ||||
| Socio-economic barriers (45 studies) | SEB1 | Project investment | 35 | SEB1.1 | High capital cost | 29 |
| SEB1.2 | High payback period and cost overruns | 10 | ||||
| SEB1.3 | Operation costs (Grid fee, water fee) | 7 | ||||
| SEB1.4 | Land compensations | 5 | ||||
| SEB2 | Public opposition | 24 | SEB2.1 | Acceptance (Inundation public) | 15 | |
| SEB2.2 | Forced displacements | 13 | ||||
| SEB2.3 | Affect fisheries business | 13 | ||||
| SEB2.4 | Awareness | 10 | ||||
| SEB2.5 | Not in my backyard | 7 | ||||
| SEB2.6 | Lengthy const. time | 6 | ||||
| SEB2.7 | Scattered houses | 1 | ||||
| SEB3 | Institutional challenges | 13 | SEB3.1 | Absence legal and policy framework | 13 | |
| SEB3.2 | Institutional coordination | 3 | ||||
| SEB4 | Political government interference | 12 | SEB4.1 | Lack of political will | 10 | |
| SEB4.2 | Bureaucratic drags | 4 | ||||
| SEB4.3 | Corruption | 2 | ||||
| SEB4.4 | Forest and Land departments | 1 | ||||
| SEB5 | Market failure | 9 | SEB5.1 | Lack of skilled human resources and technology | 7 | |
| SEB5.2 | Controlled energy sector | 2 | ||||
| SEB5.3 | Market rule uncertainties | 2 | ||||
| SEB6 | Sponsorship | 8 | SEB6.1 | Finance procurement challenges | 6 | |
| SEB6.2 | Lack of private investor | 3 |
*Note: Extended version of this Table with references at item level is supplied in the Appendix A (Table A2).
3.5.1.1. Lacking infrastructure (TEB1)
This was the foremost barrier cited in the reviewed studies. The absence of roads and transmission lines that prevents access to cheap surplus power is a technical barrier, which in turn delays the development of PHES; this delay has financial consequences. Having an infrastructure of roads and power transmission in proximity is beneficial in several ways. First, it allows easy access to the supply materials required during construction and maintenance phases; without this infrastructure, building new roads would increase the initial cost of the projects. Second, access to nearby transmission lines or a power utility grid is required to transport power, first when there is surplus power in a grid that would be used to pump the water to the upper reservoir and second when the grid requires power to balance the loads by utilising stored water to generate power. However, the unavailability of surplus power causes the facility to be dysfunctional, as power for pumping is mostly available between midnight and early morning. This reduces the overall output from these pumping stations, as mentioned in one of the studies (Sivakumar et al., 2013) in India. This study also reported that during national holidays and weekends, the pumping station in their study obtained a greater power share in the utility grid to operate machines such as water pumps. The closure of industrial sectors and a power surge during the rainy season significantly reduced the load on this utility grid, as electrically fed agricultural pumps were not used. Therefore, the absence of road and, more significantly, the absence of a transmission network may be technically and financially demanding to PHES projects.
3.5.1.2. Landscape topology (TEB2)
This was the second most reported precluding factor in the literature. The topography of a site decides the type, height (head or elevation), slope and shape of a dam, the head to length (H/L) ratios and the amount of earthwork required to build it (Lu et al., 2018). The head is the minimum elevation difference between the upper and the lower reservoirs (closed-loop system) or the river, sea, or stream (open-loop system). Having a high head means less construction is required and equipment costs are lower, and vice versa (Kucukali, 2014). A mild slope of the surface reduces the time and cost required to cut and fill the surface while constructing an artificial reservoir. Therefore, areas with a slope of more than 10%, for example, are a barring factor. The H/L ratio is the ratio between the gross head and the horizontal distance that separates the two reservoirs of the PHES and is usually 10/2 for most PHES projects. Having a higher H/L ratio means more hydraulic losses and a high cost of excavation and construction (Kucukali, 2014), so landscape topology has technical and financial implications on pumped hydro projects.
3.5.1.3. Land acquisition challenges (TEB3)
Land acquisition challenges, such as land use, vegetation clearing and land ownership, are environmental complications of pumped hydro development. Usually, land use for a project such as this is meticulously planned. There must be no interference in protected lands or forests, river systems, urban or rural settlements or intensive agriculture, national parks, or areas of historical or cultural value. Violating these guidelines is often discouraged environmentally and socially; otherwise, this violation complicates project development (Blakers et al., 2017). One study even mentioned that potential sites intersecting with moving transmission lines are a conceivable constraint, as they are expensive and disruptive. Therefore, abstaining from building at such sites is highly favourable (Fitzgerald et al., 2012). Landownership issues were also reported in one of the studies (Sovacool et al., 2011) as a land acquisition barrier, which means the locals claim ownership of uninhabited lands, or they intentionally move into the designated project area to collect compensation money, building temporary accommodation shelters or structures before construction work begins.
3.5.1.4. Water issues (TEB4)
Water issues were the fourth most reported barrier in pursuance of pumped hydro project development. For the studied papers, water issues were emphasised more in developing countries when compared to developed countries. The reviewed studies captured various themes in this regard, such as water availability and quality, water loss, conflict of interest with the local water supply (for open-loop systems), loss of oxygen and other hydrological effects. A high volume of water is normally required to fill the reservoirs. Most studies identified water availability as a key challenge for the development of PHES; as expected, studies where water scarcity is more prevalent such as Jordan, Iran and Cameroon, indicated this issue being of paramount importance (Droogers et al., 2012). Transporting water from a long distance is expensive, and nearby river or stream availability is uncommon at potentially available sites. Leakage and water evaporation loss are yet another issue, which is partly compensated by rainwater and occasional water replenishment. The geographical location of any PHES requires consideration for leakage and evaporation effects on life cycle performance; usually, countries near the equator have much lower evaporation (Seager et al., 2003). Some environmental groups in Hudson Highlands, USA, obstructed the construction of a pumped hydro facility on grounds that posed a threat to the local water (Yang and Jackson, 2011). Some studies also mentioned that pumped hydro reservoirs spoil the quality of surface and underground water (Lu et al., 2020), as stagnant water might result in water-borne diseases, especially in tropical areas (Koch, 2002). Oxygen loss in water was reported in the Richard B. Russell Dam and a conventional hydropower station in South Carolina, where an oxygen injection system was installed to compensate for this issue (Yang and Jackson, 2011). The hydrological impacts of PHES on concentration levels of heavy metals such as cadmium, lead, zinc and copper has been determined as an issue (Provis, 2019).
3.5.1.5. Geological faults (TEB5)
The reviewed studies described geological faults as a technical constraint on the development of pumped hydro facilities. These faults are no longer frequently considered. However, more detailed future studies on large-scale pumped hydro facilities should consider geological constraints such as active faults, large-scale faults and fracture zones and the presence of permeable bedrock, such as in karstic areas, in the lining of the reservoirs. This may increase the overall construction costs (Kucukali, 2014). Screening of these faults is crucial to the construction of underground waterways (tunnel and shaft) and control rooms. Seismic activity and large-scale landslide areas are other factors entailing consideration while executing a pumped hydro project (de Carvalho and do Carmo, 2007).
3.5.1.6. Biodiversity loss (TEB6)
The studies highlighted biodiversity loss related to pumped hydropower development as a prominent environmental barrier to the development of PHES. The participants across studies cited the environmental impacts on birds and fisheries and temperature changes and soil erosions. For example, an environmental activist against the Hudson River project in the USA blocked its construction based on claims that it posed a threat to the fisheries business (Yang and Jackson, 2011). Similarly, a study in Turkey flagged a PHES construction site for its sensitivity to biodiversity loss and asked to ensure the protection of critical habitats, threatened species and spawning areas (Kucukali, 2014). A study in Nepal also warned that the run from river projects could pose a threat to fish migrations due to the disturbance of river ecology (Suhardiman and Karki, 2019). One of the studies also warned that PHES might impact on bird habitats (Lu et al., 2020), and PHES induced soil erosion issues was reported in another study (Lu et al., 2018). One of the studies noted that creating large reservoirs or lakes might change the local climate by increasing the lowest temperature and decreasing the highest temperature; hence, the region would become colder (Gajic et al., 2019). The issues described in these studies could agitate locals and environmental groups.
3.5.2. Socio-economic barriers
Forty-five of the reviewed studies discussed various SEBs to the development of PHES, such as high capital costs and social and political opposition. These themes are presented in this section (see Table 2).
3.5.2.1. Project investment (SEB1)
This was the most cited SEB in the reviewed studies that considered capital costs, operation and maintenance costs, the payback period and other economic parameters as complex financial hurdles to pumped hydro projects. The capital investment of pumped hydro projects is usually site-specific, and some studies have stated that it varies from €600–3,000/kW (Deane et al., 2010). This cost is for land, road construction, development costs (project study and management, as this, comprises of 7–10% of the initial costs), equipment, control rooms, secondary electromechanical equipment, grid connection and internal cabling and the transformer's initial cost (Kapsali et al., 2012). The cited studies mentioned that an additional cost is likely to be incurred in securing financing for all the capital costs. Operation and maintenance costs might include the costs of maintaining the facility and pumping water back to the upper reservoir. However, this cost can vary depending on the time when the power is borrowed from the grid to run the pumping machine. Furthermore, open-loop-configured plants might be subject to a water usage fee for using water from a river or lake (Bjarne Steffen, 2012). The wages and salaries of workers, engineers and the management team are yet other costs involved. Further costs would also be required to compensate businesses such as agricultural and fishery businesses in the inundated public downstream. The payback period required to repay loans is believed to be another hurdle in developing pumped hydro, as it requires at least 2.5–5.5 years (Connolly et al., 2012).
3.5.2.2. Public opposition (SEB2)
This was the second most reported barrier in the literature. The relevant studies discussed public acceptance, lack of awareness, not in my backyard syndrome, business impact, forced displacement, construction time complaints and scattered settlement issues, among other issues. Public debate and dispute in pumped hydro developmental projects are relatively common. A study (Yang and Jackson, 2011) described that its local environmental group objected to the profitability and the concept of energy storage itself, calling it a ‘perpetual money machine’ and said it is not renewable, rather a power arbitrage thus preventing the acceptance of PHES systems. The public can also oppose PHES construction, saying that stagnant water has a bad smell and causes disease from mosquitos, and there is a risk of bursting during earthquakes. Another study (Seetharaman, Moorthy et al., 2019) claimed that these oppositions are mostly due to a lack of awareness of the ecological and financial benefits of the projects. Another study (Sovacool et al., 2011) claimed that the public in rural areas are unaware of the timeline for project completion and are bothered by the prolonged construction time (10 years or more in some circumstances), and they thus raise concerns. When potential construction sites are found in rural areas with scattered housing or low population density, these areas are disrupted for the greater good and their people are forced to relocate, which is often met with opposition from the anti-dam communities, as reported in Nepal (Sovacool et al., 2011). Disturbing fisheries and other benefits linked to the locals residing downstream are also potential reasons for public dispute of hydro projects. This makes the approval and construction of these projects controversial and time-consuming.
3.5.2.3. Institutional challenges (SEB3)
The reviewed studies underscored the absence of legal frameworks, lack of decision making and lack of coordination among the participating institutions as potential barriers to pumped hydro storage systems. For example, NHA (2013) documented the extensive delays in obtaining a licence for a new PHES project from the various regulatory authorities across various jurisdictional levels, such as the state and then federal level. This issue was also reported in in developed countries (e.g., the USA), often making it cost inhibitive to deliver an economically viable PHES project (Deane et al., 2010). Similar problems can be found in developing countries such as Nepal, where the delayed response of institutions and lack of coordination, in addition to the impacts of the decade-long civil war, has incapacitated their purpose of hydro energy utilization. The lack of unified planning and decision making has exacerbated the issues with hydro project development, in addition to wasting social resources (Ghimire and Kim, 2018).
3.5.2.4. Political government interference (SEB4)
The studies underlined that government lobbying, bureaucratic drag and corruption are barriers to the construction of pumped energy facilities. They determined that having different ruling political parties at the state and federal level is likely to create a rift for political gain that could delay the timely execution of projects. Bureaucrats are administrative officials, and they reportedly pose administrative hurdles due to a lack of coordination between the heads of different departments. They might also purposely delay the project's start time by slackening the bureaucratic system to extort more bribes, which also reduce motivation (Locatelli et al., 2017). One of the studies (Kear and Chapman, 2013) mentioned that a pumped hydro project would allegedly be opposed by the Forest and Bird department due to the destruction it would cause to the ecological value of the existing landscape.
3.5.2.5. Market failures (SEB5)
This cluster includes the state-controlled energy sector, market rule uncertainties and a lack of skilled labour, which were reported by the reviewed studies. Skilled labour, including engineers, energy and policy experts and technical diploma holders, are vital to the construction of power plants. However, the availability of skilled labour mainly depends on the educational systems of the country. Due to a struggling economy, developing countries mostly lack local specialists who can conduct feasibility studies or help in the construction of hydro projects, and in procuring outside labour, high salaries and perks increase the overall costs of the project (Jaber, 2012). Liberalising electricity markets expedites the development of energy projects (Deane et al., 2010), and failing to do so has negative impacts. Uncertain market rules are a prime reason for low investment in projects, so this is also considered a barrier.
3.5.2.6. Project financing (SEB6)
The construction of a new pumped hydro project is subject to the availability of funds, either from the government, private sector investors or multiple financing sources, and it is a challenging and complex task (IHA, 2018b). Very few organisations or private investors agree to finance such long-term projects due to licensing timeframe uncertainties or long payback periods (NHA, 2013). A study (IHA, 2018b) determined that presently, most PHES systems in operation are financed under public sector ownership.
3.6. Global weight analysis results of the identified barriers
Among barriers, the top-weighted item was high capital cost (SEB1.1), under the cluster of project investment, with a global weight of 0.0963. Seismic activities (TEB5.1), under the cluster of Geological faults, were the second most weighted barrier, with a global weight of 0.0625. This was followed by the absence of transmission lines (TEB1.1), under lacking infrastructure, as the third most prominent barrier, with a global weight of 0.0620. Fig. 4 shows the determined global weight for TEBs and SEBs that are placed in a precedence rank with specified colour codes for TEBs (dark blue) and SEBs (dark grey). The details on the individual and global weights of the barring factors and items are provided in Appendix B (Table B2).
Fig. 43.7. Comparing PHES barriers from developed with developing countries
For barriers (see Fig. 5), a similar response to drivers was recorded, where the techno-environmental barriers to PHES reveal that studies in developed nations compared to developing nations focus more on lack of infrastructure (TEB1), landscape topology (TEB2) and geology-related issues (TEB5) as potential barriers to the installation of PHES. On the other hand, studies in developing nations compared to developed nations emphasise TEB3 (land acquisition challenges), TEB4 (emerging water issues) and TEB6 (biodiversity losses) as potential barriers to executing PHES. The SEBs to PHES development identified during this study were more apparent in studies conducted in developing countries than developed countries and include SEB1 (Project investment), SEB2 (public opposition), SEB3 (institutional challenges), SEB4 (political government interference) and SEB5 (market failures). However, SEB6 (sponsorship) was reported the same number of times in developed and developing countries. These findings for SEBs imply that it is difficult for developing countries to secure funding and investments for the development of PHES, coupled with public and political opposition, corruption and lack of institutions. Although it appears that developed countries report these issues less often, they are there. Further, see Appendix C (Table C2). on PHES barrier comparison for developed versus developing countries.
Fig. 54. Conclusions
In this paper, a wide range of techno-economic and socio-environmental drivers for and barriers to pumped hydro applications have been systematically analysed, synthesised and tabulated, following PRISMA guidelines. This study reviewed the published literature over the past 20 years (2000–2020). It used a forward search strategy of records in the computerised databases WOS and Scopus. Backward reference search was also used to include the records that might have missed.
This study also synthesised the different methodologies that were implemented in relation to PHES applications and found that feasibility studies were the most reported method. In these studies, a GIS–MCDM algorithm was frequently used. Hybrid wind–PHES system to energise urban and rural areas was the most reported subject, as PHES provides the storage mechanism crucial to buffer the volatility from the wind supply. This study also discovered that there was a growing interest in the closed-loop system due to greater certainty in gaining an operating license, since closed systems don't interfere with water supply security and typically have a lower environmental impact.
The important drivers for PHES were its ability to act as utility-scale storage, generate revenue by pumping water at cheap prices during off-peak times and then selling it at higher rates during peak hours, and their ability to support volatile renewable energy sources. The main barriers to PHES development were a lack of supporting infrastructures such as roads and transmission lines, unfavourable topography such as low head or H/L ratio, high capital costs, high operation and maintenance costs, and long payback periods. The overall findings of this study have been synthesised in an illustration (Fig. 6). In this figure, the drivers, and the barriers of PHES are presented and their relative significance prioritized based on the findings in a clockwise direction, whereas the bi-directional arrow sign (⇆) at the centre represents the pumping modes of a PHES. The inner-circle represents TEDs and SEDs whereas the outer circle represents the TEBs and SEBs.
Fig. 6While this study outlines various drivers for and barriers to the development of PHES, it has limitations that could be addressed by future researchers. This review primarily retrieved records only from WOS and Scopus databases, however, other databases could be used to search articles not indexed by WOS and Scopus. Articles in other languages and/or with access restrictions could also be used as most of these services are available only to registered users. The records profiling and coding of drivers and barriers were guided by related past studies and the authors experience. Future work could solicit expert stakeholder opinion through extensive surveys and in-depth interviews in order to verify the barrier and driver factors, their categorisation, and their relative significance. Overall, by systematically collecting and reviewing the literature, this paper has provided a sophisticated understanding of the existing drivers for and barriers to PHES applications in developed and developing countries as well as the ongoing methodological trends. The findings of this study will be of significant use to researchers and developers of PHES in the future.
CRediT author statement
Shahid Ali: Conceptualization, Methodology, Investigation, Writing– Original draft preparation. Rodney A. Stewart: Supervision – reviewing and editing. Oz Sahin: Co-supervision – reviewing and editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.