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The world is warming, and the demand for cooling is increasing. Developing a future green hydrogen economy will also increase the demand for cooling for hydrogen liquefaction. This increase in cooling demand will happen mainly in tropical and developing countries due to their increase in population, improvements in quality of life, and the export of their renewable potential with liquid hydrogen. To solve this increase in demand for cooling, this paper proposes the use of ammonia airship cooling (AAC). AAC extracts cold from the tropopause (−80 °C) with airships and ammonia refrigeration cycles. The liquid ammonia is then transported back to the surface to provide low temperature cooling services (−33 °C). This cooling service is particularly interesting for lowering the electricity consumption in hydrogen liquefaction plants. If all the technological challenges mentioned in the paper are addressed, it is estimated that the cost of cooling with the technology is 8.25 USD/MWht and that AAC could reduce the electricity demand for hydrogen liquefaction by 30%. AAC is an innovative renewable cooling technology that has the potential to complement other renewable energy sources in a sustainable future. [ABSTRACT FROM AUTHOR]

Low-carbon energy transitions taking place worldwide are primarily driven by the integration of renewable energy sources such as wind and solar power. These variable renewable energy (VRE) sources require energy storage options to match energy demand reliably at different time scales. This article suggests using a gravitational-based energy storage method by making use of decommissioned underground mines as storage reservoirs, using a vertical shaft and electric motor/generators for lifting and dumping large volumes of sand. The proposed technology, called Underground Gravity Energy Storage (UGES), can discharge electricity by lowering large volumes of sand into an underground mine through the mine shaft. When there is excess electrical energy in the grid, UGES can store electricity by elevating sand from the mine and depositing it in upper storage sites on top of the mine. Unlike battery energy storage, the energy storage medium of UGES is sand, which means the self-discharge rate of the system is zero, enabling ultra-long energy storage times. Furthermore, the use of sand as storage media alleviates any risk for contaminating underground water resources as opposed to an underground pumped hydro storage alternative. UGES offers weekly to pluriannual energy storage cycles with energy storage investment costs of about 1 to 10 USD/kWh. The technology is estimated to have a global energy storage potential of 7 to 70 TWh and can support sustainable development, mainly by providing seasonal energy storage services. [ABSTRACT FROM AUTHOR]

The rapid increase in cooling demand for air-conditioning worldwide brings the need for more efficient cooling solutions based on renewable energy. Seawater air-conditioning (SWAC) can provide base-load cooling services in coastal areas utilizing deep cold seawater. This technology is suggested for inter-tropical regions where demand for cooling is high throughout the year, and it has been implemented in islands with short distances from the coast and the deep sea. This paper proposes adjustments to the conventional design of SWAC plants to reduce implementation risks and costs. The approach is named high velocity SWAC and consists of increasing the excavation depth of the seawater pump station up to 20 m below the sea level, compared to 2 to 5 m in conventional SWAC projects. This allows a twofold increase in the speed of inlet pipeline seawater and cooling load of the plant. The cooling load can be expanded twofold with only 55% capital cost and 83% project costs, compared with the costs of a new system. In addition, this article shows that high velocity SWAC plants with thermal energy storage will have an important role supporting the dissemination of intermittent renewable sources of energy in regions where SWAC is a viable cooling alternative. [ABSTRACT FROM AUTHOR]

Renewable sources of energy are providing an increasing share of the electricity generation mix, but their intermittency drives a need for energy storage. At the same time, water resources are increasingly scarce due to changes in demand, such as from population growth, supply side pressures such as climate change and governance challenges relating to poor management. Large storage reservoirs are used for water management and for energy storage. However, some existing and proposed hydropower reservoirs require vast areas of land and have considerable social and environmental impacts. Growing concerns on water and energy storage from a water-energy-land nexus approach motivated this study. Our objective is to compare how energy and water storage services, such as hydropower generation, electricity grid and water management, are provided with Seasonal Pumped-Storage (SPS) and Conventional Reservoir Dams (CRD) plants. Our case study region is Brazil, a country with extensive hydropower capacity and development plans, for which we compare the cost, land requirement and social impacts between CRD and potential SPS plants. Whilst seasonal pumped-storage have higher capital costs than conventional reservoir dams, given the much lower land requirements and evaporative losses, they are a valuable water and energy storage alternative especially in locations with plain topography and high evaporation. Results show that if Sobradinho CRD was built today it would result in a $USD 1.46 billion loss, on the other hand, Muquém SPS plant would result in a $USD 0.67b revenue. [ABSTRACT FROM AUTHOR]

The world is undergoing a rapid energy transformation dominated by growing capacities of renewable energy sources, such as wind and solar power. The intrinsic variable nature of such renewable energy sources calls for affordable energy storage solutions. This paper proposes using lifts and empty apartments in tall buildings to store energy. Lift Energy Storage Technology (LEST) is a gravitational-based storage solution. Energy is stored by lifting wet sand containers or other high-density materials, transported remotely in and out of the lift with autonomous trailer devices. The system requires empty spaces on the top and bottom of the building. An existing lift can be used to transport the containers from the lower apartments to the upper apartments to store energy and from the upper apartments to the lower apartments to generate electricity. The installed storage capacity cost is estimated at 21 to 128 USD/kWh, depending on the height of the building. LEST is particularly interesting for providing decentralized ancillary and energy storage services with daily to weekly energy storage cycles. The global potential for the technology is focused on large cities with high-rise buildings and is estimated to be around 30 to 300 GWh. • A new gravitational energy storage solution based on the operation of lifts in high-rise buildings. • LEST is a decentralized solution for energy storage with daily to weekly cycles. • The installed capacity energy storage cost of LEST is 21–128 USD/kWh. • LEST is particularly interesting for providing decentralized ancillary services. • The world potential for LEST is estimated to be 30 to 300 GWh. [ABSTRACT FROM AUTHOR]

The world switching to more sustainable energy sources to curb CO 2 emissions and haul climate change. One sector expected to see rapid growth in energy consumption is the cooling sector due to population growth and climate change. A sustainable solution for cooling needs in coastal areas that are not often addressed is seawater air-conditioning, which pumps cold water from the deep sea to the shore and uses it for cooling. The main challenge for this technology is to distribute the cooling service. This paper proposes using pressurized ammonia to distribute the cooling services provided by SWAC plants. Results show that ammonia district cooling allows SWAC to significantly increase its load demand and lower cooling costs. Ammonia district cooling could be the missing piece for implementing seawater air-conditioning due to its potential to increase the cooling load of district cooling systems. • Ammonia district cooling, the missing link for district cooling solutions. • A 17 m3/s seawater flow can provide 1 GWt of cooling load. • Ammonia, a better alternative for thermal energy transport than steam. [ABSTRACT FROM AUTHOR]

The world is undergoing a transition to a more sustainable energy sector dominated by renewable energy sources. This paper proposes an innovative solution that consists of catching water from streams at high altitudes to fill storage containers and transport them down a mountain, converting the potential energy of water into electricity with the regenerative braking systems of electric trucks and storing it in the truck's battery. The energy stored in the electric truck can be sold to the grid or used by the truck to transport other goods. Results show that the levelized cost of the electricity truck hydropower is 30–100 USD/MWh, which is cheap when compared with conventional hydropower 50–200 USD/MWh. The electricity generation world potential for the technology is estimated to be 1.2 PWh per year, which is equivalent to around 4% of the global energy consumption in 2019. Apart from being a low cost and impact electricity generation technology, electric truck hydropower can operate in combination with solar and wind resources and provide energy storage services to the grid. • Innovative hydropower generation alternative. • Levelized cost of the electricity truck hydropower is 30–100 USD/MWh. • The electricity generation world potential for the technology is estimated to be 1.2 PWh per year. • Asia and South America have the highest potential for ETH. [ABSTRACT FROM AUTHOR]

Before the COVID pandemic, oil and gas companies invested only a small fraction of their capital on sustainable energy technologies. With the substantial improvement in the performance of batteries and their rapid cost reduction, the oil and gas industry could potentially lose a large share of their market in the transport sector. A similar shift in energy sources is happening with the surge in renewable energy sources to supply electricity, heating and cooling. In an ever more sustainable future, the need for an oil and gas industry could reduce significantly. This paper reviews the possible paths that an oil and gas company could follow to become a sustainable development corporation and continue to be relevant in the future. This paper aims to describe alternative sustainable pathways such as the extraction of natural hydrogen, a hydrogen economy, offshore wind power, deep sea mining, biorefineries, seawater air-conditioning, geothermal and geoengineering. This paper also proposes the use of electrolysis ships for the flexible production of green hydrogen and showed that its investment cost can be three times smaller than in fixed electrolysis plants. The oil and gas industry has substantial intellectual, financial capital and geopolitical influence that would not be lost during a shift to a more sustainable world. Indeed, these assets should be used to facilitate the transition to a more sustainable future. • Hydrogen is a good alternative for sustainable development in O&G companies. • Natural hydrogen is a good alternative to the upstream O&G companies. • Benefits of electrolysis ships to produce green hydrogen. • Case study to produce green hydrogen in Brazil. [ABSTRACT FROM AUTHOR]

The energy sector is undergoing substantial transition with the integration of variable renewable energy sources, such as wind and solar energy. These sources come with hourly, daily, seasonal and yearly variations; raising the need for short and long-term energy storage technologies to guarantee the smooth and secure supply of electricity. This paper critically reviews the existing types of pumped-hydro storage plants, highlighting the advantages and disadvantages of each configuration. We propose some innovative arrangements for pumped-hydro storage, which increases the possibility to find suitable locations for building large-scale reservoirs for long-term energy and water storage. Some of the proposed arrangements are compared in a case study for the upper Zambezi water basin, which has considerable water storage limitations due to its flat topography and arid climate. Results demonstrate that the proposed combined short and long-term cycles pumped-storage arrangement could be a viable solution for energy storage and reduce the cost for water storage to near zero. • Review of existing pumped-storage types. • Pumped-hydro storage an effective alternative for water, energy and land nexus issues. • Proposed arrangement for combining short- and long-term energy and water needs. • Proposed arrangement for combining hydropower and pumped-hydro storage. • Comparison of proposed pumped-hydro storage projects in the Zambesi river basin. [ABSTRACT FROM AUTHOR]

The world is undergoing an energy transition with the inclusion of intermittent sources of energy in the grid. These variable renewable energy sources require energy storage solutions to be integrated smoothly over different time steps. In the near future, batteries can provide short-term storage solutions and pumped-hydro storage can provide long-term energy storage with large generation capacities. However, none of these technologies can provide long-term energy storage in grids with small demand. This paper proposes a new storage concept called Mountain Gravity Energy Storage (MGES) that could fill this gap in storage services. MGES systems move sand or gravel from a lower storage site to an upper elevation. The higher the height difference the greater the amount of stored energy in a given installed capacity, as this technology is constrained to the topography of the location. MGES cost varies from 50 to 100 $/MWh of stored energy and 1–2 M$/MW of installed capacity. MGES could be a feasible option for micro-grids, for example, small islands and isolated areas, and power systems where electricity costs are high, demand for energy storage is smaller than 20 MW with monthly or seasonal storage requirements. • A new energy storage solution based on mountain gravity is found particularly for grids smaller than 20 MW. • MGES is a solution for seasonal storage where there is no water for pumped-storage solutions. • We show the world potential for MGES using a GIS based tool. • The new storage solution can fill the gap in terms of size and duration of existing storage options. [ABSTRACT FROM AUTHOR]

Energy harnessing from renewable energy sources has become more flexible with power electronic technologies. Recent advancements in power electronic technologies achieve converter efficiency higher than 98%. Today, reliable power electronic devices are needed to design a PV-based energy converter (inverter) to reduce the risk of failure and maintenance costs during operation. Wide-bandgap SiC devices are becoming more common in power electronic converters. These devices are designed to reduce switching loss and improve the efficiency of the system. Nevertheless, the cost of SiC devices is a major concern. Hence, to improve the reliability of the PV inverter while considering the economic aspects, this paper develops a highly reliable PV inverter with a hybrid Si/SiC power module that consists of a Si-IGBT with a SiC anti-parallel diode. A test case of a 3 kW PV inverter is considered for reliability analysis. The loading of the PV inverter is done under uncertain environmental conditions by considering the yearly Mission Profile (MP) data related to Ambient Temperature (AT) and Solar Irradiance (SI) at the India and Denmark locations. The effectiveness of the proposed hybrid Si/SiC power module is tested by comparing it with a conventional IGBT power module. The results showcase the marked improvement in PV inverter reliability with the proposed hybrid power module. [ABSTRACT FROM AUTHOR]

Modular Gravity Energy Storage (M-GES) systems are emerging as a pivotal solution for large-scale renewable energy storage, essential for advancing green energy initiatives. This study introduces innovative capacity configuration strategies for M-GES plants, namely Equal Capacity Configuration (EC) and Double-Rate Capacity Configuration (DR), tailored to optimize energy storage efficiency and stability. Through comprehensive MATLAB/Simulink simulations, we demonstrate each configuration's distinct power characteristics and operational advantages. Our findings reveal that while the EC configuration offers enhanced power accuracy and stability, it requires a larger number of units. In contrast, the DR configuration, characterized by fewer but larger units, shows a trade-off with reduced power stability. This paper contributes significantly to the field by presenting a first-of-its-kind comparative analysis of these configurations, offering insights into their practical applications and scalability. The proposed strategies and findings lay a foundation for future research and development in gravity energy storage systems, marking a step forward in pursuing sustainable and reliable energy solutions. [Display omitted] • Two typical unit capacity configuration strategies for M-GES power plants are proposed. • The unit scheduling method of the M-GES power plant is proposed. • The coordination control method is provided for each proposed configuration strategy. • Equal capacity configuration has better power accuracy but requires more units. • Double rate configuration needs fewer but larger units and less power stability. [ABSTRACT FROM AUTHOR]