Distributed energy storage (DES) resources, such as electric vehicle batteries and hot water storage, can provide significant, currently underutilised, demand flexibility to support the uptake of variable renewable energy sources. However, large-scale assessments of DES resources on a city level are scarce. In this research, a set of methods are developed for high-resolution temporal and spatial assessment using Geographic Information System-based models. An all-electric energy future is modelled for the Australian Capital Territory as a case study, which features one of the world's most rapid transitions towards net-zero emissions. The modelling results show that electric vehicle batteries and hot water storage can provide storage capacities of 43 kWh and 2.6 kWh per capita, respectively. The daily flexibility they provide can reach 3.8 kWh/day and 1.5 kWh/day per capita, equivalent to one-third of the average electricity consumption of 16 kWh/day per capita. The distribution of DES resources is highly dependent on population density and urban growth. Storage capacity varies dynamically with daily travel patterns, rising by 2%-21% during the weekday in workplace-dense districts. Integrating electric vehicles and electric water heating systems may increase electricity consumption by 48% while raising peak load by 34%, indicating an improvement in the utilisation of electricity grid infrastructure from transport and heating electrification. Additionally, various charging and heating strategies could modify the peak load growth to 37%, 16%, and 20% with the daytime, overnight and flat profiles, respectively.

Decarbonising heavy industries, e.g., steel, aluminium, and cement, present unique challenges due to their high energy intensity and reliance on 24/7 continuous power supply. With volatile fossil fuel prices and increasing carbon regulations, the transition to renewable energy is critical for long-term economic and environmental sustainability. This study develops a new high-resolution energy modelling framework to assess the technoeconomic feasibility of supplying 24/7 industrial electricity using low-cost onsite photovoltaic (PV) and battery storage systems. The model incorporates lifecycle degradation and intermittency with an hourly temporal resolution over a 25-year time horizon, integrated with grid interaction and load flexibility strategies. The results show that projected declines in PV and battery costs could lower electricity costs by 41% from $157/MWh to $92/MWh, though energy spillage constrains further savings. Grid interaction through bidirectional electricity exchange with the grid could reduce electricity costs by up to 42% and increase renewable energy integration from 37% to 100%. Load flexibility could reduce electricity costs by up to 80%, while achieving 100% renewable energy integration. Sensitivity analysis suggests that electricity costs are most sensitive to natural gas price and discount rate, while PV and battery degradation also have a measurable impact of $2-$5/MWh. The research findings provide quantitative evidence on the techno-economic feasibility of PV and battery integration for heavy industry operations, supporting strategic decisions for industrial decarbonisation.

Fossil gas is sometimes presented as an enabler of variable solar and wind generation beyond 2050, despite being a primary source of greenhouse gas emissions from methane leakage and combustion. We find that balancing solar and wind generation with pumped hydro energy storage eliminates the need for fossil gas without incurring a cost penalty. However, many existing long-term electricity system plans are biased to rely on fossil gas due to using temporal aggregation methods that either heavily constrain storage cycling behaviour or lose track of the state-of-charge, failing to consider the potential of low-cost long-duration off-river pumped hydro, and ignoring the broad suite of near-optimal energy transition pathways. We show that a temporal aggregation method based on 'segmentation' (fitted chronology) closely resembles the full-series optimisation, captures long-duration storage behaviour (48- and 160-hour durations), and finds a near-optimal 100

The increased uptake of variable renewable energy sources has increased electricity price volatility in many energy pool markets, providing an opportunity for storage systems to profit through energy arbitrage. Comparison between the cost or value of storage systems engaging in energy arbitrage should be performed on a levelised basis due to differences in system lifetime. Existing energy arbitrage models with bid/offer curves and imperfect forecasting are typically computationally expensive and are impractical for calculating lifetime levelised cost metrics. In this work, an open-source modular energy arbitrage model with bid and offer curve inputs was developed for a lithium-ion battery energy storage system (BESS) and pumped hydro system (PHS) to analyse lifetime levelised cost and revenue. The mixed integer linear program scheduling module included a new piece-wise linearised description of PHS charging behaviour for rapid optimisation. A one-at-a-time sensitivity analysis indicated that levelised cost and revenue were highly sensitive to discharging efficiency. In a case study based on Australia’s National Electricity Market, imperfect forecasting with no risk hedging was found to increase levelised costs by up to 24% and decrease levelised revenue by up to 50% relative to perfect price forecasting, despite 95% of prices being forecast to be within $35/MWh of the actual trading price. BESS levelised costs were more significantly correlated with consistent low risk bids (Kendall Tau-b of 0.75), since the undiscounted capital costs contribute to a larger proportion of the overall costs than in the PHS systems.

Sustainable, low-emission electricity generation options are needed in the Greater Mekong Subregion, including for cross-border electricity trade. Large-scale investment in solar and wind power, together with off-river pumped hydro energy storage, is identified as a promising way forward. The GMS has many potential off-river pumped hydro sites. Actionable recommendations include greater use of bilateral power purchase agreements for cross-border solar and wind power supply, and potential development of a high-voltage direct current grid. Institutional prioritization and ongoing evaluation are required to ensure desired social, environmental, and economic outcomes from the transition.

Fossil fuels currently cause about three quarters of global greenhouse gas emissions. Renewable electricity can be used to decarbonize electricity production, transport, heating, and industry. Solar photovoltaics and wind energy accounted for about three quarters of global generation capacity additions in 2022. Using Australia as an example, we show that large reductions in freshwater consumption can be expected when a coal-dependent electricity system transitions to a 90% solar photovoltaics and wind generation mix, supported by pumped hydro energy storage. Such a system would have a similar levelized cost of electricity to the current one, but near zero greenhouse gas emissions and operational air pollution. For the Australian case study, water consumption for operations and fuel are reduced by about 80%. We also present a method to measure water consumption from off-river pumped hydro pairs.

Low-cost solar photovoltaics and wind offer a reliable and affordable pathway to deep decarbonization of energy, which accounts for three quarters of global emissions. However, large-scale deployment of solar photovoltaics and wind requires space and may be challenging for countries with dense population and high per capita energy consumption. This study investigates the future role of renewable energy in Japan as a case study. A 40-year hourly energy balance model is presented of a hypothetical 100% renewable Japanese electricity system using representative demand data and historical meteorological data. Pumped hydro energy storage, high voltage interconnection and dispatchable capacity (existing hydro and biomass and hydrogen energy produced from curtailed electricity) are included to balance variable generation and demand. Differential evolution is used to find the least-cost solution under various constraints. This study shows that Japan has 14 times more solar and offshore wind resources than needed to supply 100% renewable electricity and vast capacity for off-river pumped hydro energy storage. Assuming significant cost reductions of solar photovoltaics and offshore wind towards global norms in the coming decades driven by large-scale deployment locally and global convergence of renewable generation costs, the levelized cost of electricity is found to be US$86/Megawatt-hour for a solardominated system, and US$110/Megawatt-hour for a wind-dominated system. These costs can be compared with 2020 average system prices on the spot market in Japan of US$102/Megawatt-hour. Cost of balancing 100% renewable electricity in Japan ranges between US$20-27/Megawatt-hour for a range of scenarios. In summary, Japan can be self-sufficient for electricity supply at competitive costs, provided that the barriers to the mass deployment of solar photovoltaics and offshore wind in Japan are overcome.

Indonesia has vast solar energy potential, far more than needed to meet all its energy requirements without the use of fossil fuels. This remains true after per capita energy consumption rises to match developed countries, and most energy functions are electrified to minimize the use of fossil fuels. Because Indonesia has relatively small energy potential from hydro, wind, biomass, geothermal and ocean energy, it will rely mostly on solar for its sustainable energy needs. Thus, Indonesia will require large amounts of storage for overnight and longer periods. Pumped hydro comprises 99% of global energy storage for the electricity industry. In this paper, we demonstrate that Indonesia has vast practical potential for low-cost off-river pumped hydro energy storage with low environmental and social impact; far more than it needs to balance a solar-dominated energy system.

Large greenhouse gas reductions are possible with a fully decarbonised grid and electric land transport. Additional electric load could pose a significant challenge to a grid with high levels of variable and non-dispatchable renewable energy sources. This scenario is not well-examined, nor is the use of pumped hydro energy storage for low-cost energy balancing. In this paper, we investigate the electrification of land transport within a photovoltaics and wind dominated 100% renewable electricity system. Only technologies that are deployed at scale and widely available globally are considered, namely photovoltaics, wind, battery electric vehicles, high voltage transmission, and pumped hydro. As a case study we present an hourly energy balance analysis of the Australian National Electricity Market with 100% renewables and 100% uptake of electric vehicles for land transport. The cost of the system is determined by occasional periods (days-weeks) of low renewable generation, and therefore only weakly dependent on the charging regime. The 40% increase in electricity demand due to electric land transport can be incorporated with a 4%–8% increase in the levelized cost of electricity. An exception occurs if most passenger vehicle charging occurs during the evening peak period, in which case the average price increases by about 18%.

Resilience of the energy system is a crucial concern as we transition towards net zero and must also adapt to a changing climate. We investigate the effect of more frequent La Niña events on the operation of a future 100% renewable electricity grid in Australia. We find that such events do not lead to an increase in electricity cost for a grid that contains an optimized mix of solar, wind, pumped hydro and batteries, supported by a HVDC transmission network. Our results are a step towards the design of a future grid that is resilient to a range of extreme climate events.

Rapid increases in electricity consumption in Southeast Asia caused by rising living standards and population raise concerns about energy security, affordability and environmental sustainability. In this study, the role of short-term off-river energy storage (STORES) in supporting 100% renewable electricity in Southeast Asia is investigated. Large-scale integration of off-river, closed-loop pumped hydro storage is a new approach to providing system flexibility facilitating high penetration of variable renewable energy in electricity systems. The features of STORES include large storage potential, high technology maturity and a long service life. Energy generation, storage and transmission are co-optimised based on long-term, high-resolution chronological energy data. A comparative analysis is undertaken between the scenarios with and without an intercontinental Asia-Pacific Super Grid. The results show that, with support provided by STORES, the Southeast Asian electricity industry can achieve very high penetration (78%-97%) of domestic solar and wind energy resources. The levelised costs of electricity range from 55 to 115 U.S. dollars per megawatt-hour based on 2020 technology costs. In the Super Grid scenarios, the costs change by-4% to thorn 7% while the storage requirements reduce by 50%-89%. Renewable energy supported by STORES can be a cost-effective solution for Southeast Asia's energy transition, delivering long-term, substantial environmental benefits. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Australia is installing PV and wind at 10 times the global per capita average rate and 3-5 times faster per capita than the USA, Japan, Europe or China. Australia’s National Electricity Market (NEM) and the state of South Australia reached {PV + wind} penetrations of 24% and 70% respectively and are tracking towards 40% and 100% in 2024. This represents a natural experiment in the cost of generation and balancing. The real cost of generation and balancing will become clearer as each year passes and the PV and wind fraction of electricity in Australia continues to increase. In response to rising PV and wind penetration, balancing investment in Australia is predominantly in off-river pumped hydro, transmission and batteries. The current (2021) and market futures (2024) price for electricity is in the range of US$35/MWh which includes both generation and balancing.

Solar photovoltaic (PV) energy is identified to be a vast energy source whose technical, environmental and economic potential far exceeds Indonesia's present and future energy requirements. We estimate that electricity consumption in Indonesia could reach 9000 Terawatt-hours per year by 2050, which is 30 times larger than at present. Indonesia has abundant space to deploy enough solar PV to meet this requirement, including on rooftops, on inland reservoirs, on the Indonesian inland sea, on mining wasteland and in combination with agriculture.

Japan has committed to carbon neutrality by 2050. Emissions from the electricity sector amount to 42% of the total. Solar photovoltaics (PV) and wind comprise three quarters of global net capacity additions because of low and falling prices. This provides an opportunity for Japan to make large reductions in emissions while also reducing its dependence on energy imports. This study shows that Japan has 14 times more solar and offshore wind resources than needed to supply 100% renewable electricity. A 40 year hourly energy balance model is presented of Japan's electricity system using historical data. Pumped hydro energy storage, high voltage interconnection and dispatchable capacity (hydro, biomass and hydrogen energy) are included to balance variable generation and demand. Differential evolution is used to find the least-cost solution under various constraints. The levelized cost of electricity is found to be USD 86 per MWh for a PV-dominated system, and USD 110 per MWh for a wind-dominated system. These costs can be compared with the average system prices on the spot market in Japan of USD 102 per MWh. In summary, Japan can be self-sufficient for electricity supply at competitive costs.

The need for storage in electricity systems is increasing because large amounts of variable solar and wind generation capacity are being deployed. About two thirds of net global annual power capacity additions are solar and wind. Pumped hydro energy storage (PHES) comprises about 96% of global storage power capacity and 99% of global storage energy volume. Batteries occupy most of the balance of the electricity storage market including utility, home and electric vehicle batteries. Batteries are rapidly falling in price and can compete with pumped hydro for short-term storage (minutes to hours). However, pumped hydro continues to be much cheaper for large-scale energy storage (several hours to weeks). Most existing pumped hydro storage is river-based in conjunction with hydroelectric generation. Water can be pumped from a lower to an upper reservoir during times of low demand and the stored energy can be recovered at a later time. In the future, the vast storage opportunities available in closed loop off-river pumped hydro systems will be utilized. In such systems water is cycled repeatedly between two closely spaced small reservoirs located away from a river. This review covers the technology, cost, environmental impacts and opportunities for PHES. The key motivations for this review are firstly that large amounts of variable wind and solar generators are being deployed; and secondly that there are vast opportunities for low-cost pumped hydro storage that do not require interference with rivers (with the associated environmental cost).

Australia has one of the highest per capita consumption of energy and emissions of greenhouse gases in the world. It is also the global leader in rapid per capita annual deployment of new solar and wind energy, which is causing the country’s emissions to decline. Australia is located at low-moderate latitudes along with three quarters of the world’s population. These factors make the Australian experience globally significant. In this study, a fully decarbonised electricity system is modelled together with complete electrification of heating, transport and industry in Australia leading to an 80% reduction in greenhouse gas emissions. An energy supply-demand balance is simulated based on long-term (10 years), high-resolution (half-hourly) meteorological and energy demand data. A significant feature of this model is that short-term off-river energy storage and distributed energy storage are utilised to support the large-scale integration of variable solar and wind energy. The results show that high levels of energy reliability and affordability can be effectively achieved through a synergy of flexible energy sources; interconnection of electricity grids over large areas; response from demand-side participation; and mass energy storage. This strategy could be a rapid and generic pathway towards zero-carbon energy futures within the Sunbelt.

The difficulty of finding suitable sites for dams on rivers, including the associated environmental challenges, has caused many analysts to assume that pumped hydro energy storage has limited further opportunities to support variable renewable generation. Closed-loop, off-river pumped hydro energy storage overcomes many of the barriers. Small (square km) upper reservoirs are typically located in hilly country away from rivers, and water is circulated indefinitely between an upper and lower reservoir. GIS analysis of high resolution global digital elevation models was used to determine economically feasible closed-loop scheme locations outside protected and urban areas. This search identified 616,000 potential storage sites with an enormous combined storage potential of 23,000 TWh. This is two orders of magnitude more than required to support large fractions of renewable electricity, allowing flexible site selection. Importantly, the resource is widely distributed to effectively support large-scale solar and wind deployment for electrical grid decarbonization.

Good solar photovoltaic generation facilities are now the lowest cost source of electricity generation. However, solar generation is highly self-correlated and not well correlated to peak demand, leading to lower prices for solar generation relative to average value in markets. Energy storage provides the opportunity to shift generation from the middle of the day to meet evening and early morning peaks. Pumped hydro energy storage is the largest and cheapest source of electricity. Sites searching indicates that there are vastly more sites in the United States than could be needed for 100% renewable electricity. Levelised cost of storage for good pumped hydro sites is low. Continued installation of solar is enhancing the ‘duck curve’ effect, increasing the viability of bulk energy storage.