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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]

There is an enormous untapped potential for hydropower generation in rivers with large head and high flow variation, currently not feasible for conventional hydropower dams. Conventional dams make use of the potential energy, but waste kinetic energy from spillage during periods of high flows. This article studies the possibility of harnessing energy from potential and kinetic energy from hydropower dams with large head and flow variation, analyses its potential, and shows possible technologies. Focus is given to a Moveable Hydro-Electric Power Plant (HEPP) system in which the turbine module can be adjusted according to the flow and water level in the river. During floods the exceeding flows can pass above and below the Moveable HEPP results in a sub-pressure environment after the turbine module, thereby reducing the dam’s downstream head, increasing the pressure difference between the turbine inlet and outlet and the flow through the turbine, which increases the electricity generation of the dam. Dams with head increaser arrangement have been implemented in several dams in the 1930–1950s and now are regaining attention in Middle Europe. The main intention for its implementation is harnessing hydropower generation at run-of-river plants, with low-head, with a 20%–30% cost reduction, lower flooded area at the dam site, the resulting evaporation and the impact on the aquatic fauna. A case study was performed with the proposal of the Aripuanã Moveable HEPP in the Madeira River with a 26 ms height dam and a generation capacity of 1400 MW. The increase in generation with the head increaser effect is as high as 21%. The estimated potential for this technology in the Amazon region is 20 GW. Other potential locations are discussed in the article. Dams with head increaser effect have been successfully implemented and have the potential to become a major alternative for base load renewable energy in the future. [ABSTRACT FROM AUTHOR]

• Swimming pool as a seasonal, cooling, thermal energy storage solution. • Case study in Phoenix, Arizona, USA. • The pool is used for heating in the winter and cooling in the summer. • An average pool stores 3500 kWh of cooling energy at 0oC. • Cooling energy storage cost of 0.078 US$ kWhe−1. The rise in distributed renewable energy generation creates a growing need to find viable solutions for energy storage to match energy demand and supply at any time. This paper evaluates the possibility of using swimming pools as a long-term cooling energy storage solution, i.e., Swimming Pool Thermal Energy Storage (SPTES). This technology allows a small building to store solar energy for cooling purposes in a yearly cycle, by filling the pool with ice slurry in winter and using that ice to cool the house in the summertime. Additionally, the pool can be used as a heat sink for a heat pump to heat the house during the winter. Results show that the energy storage cost of 0.078 US$ kWhe−1 is substantially smaller when compared with batteries (125 US$ kWhe−1). This makes SPTES a good alternative to support the development of 100% renewable energy systems in locations where the climate has a highly seasonal variation in temperature and the cooling demand is high in summer. [ABSTRACT FROM AUTHOR]