Household energy needs to be available on demand, consumed at any given time of the day, and be reliable in order to power applications such as fridges and freezers which contain perishable food (Speidel & Bräunl, 2016). Our problems can be simplified in one phrase: “the wind doesn’t always blow, and the sun doesn’t always shine” (Koen & Antunez, 2020). For example, solar power is only available in the day, therefore a grid operator is responsible to adjust the day-ahead plan to include generators that adjust power output to make up for the rise and fall in solar generation (Fares, 2015).
Different types of power plants take different amounts of time to come online; 48 hours for nuclear, 12 hours for coal-fired, a few hours for modern gas power plants, ten seconds for the water released from a dam to start the turbines (Spataru, 2014). Due to this, having a back-up available at all times means having power plants running most of the time, which is both inefficient and expensive (Spataru, 2014). For example, as solar becomes increasingly popular power plants may be asked to turn off during the middle of the day so that the energy produced from solar can be used as a replacement to fossil fuels, but the goal is to eliminate the reliance of fossil fuels, so storage would be needed (Fares, 2015).
At this point in time, over 99% of large-scale electricity storage is due to pumped hydro dams, but there are geological restrictions to this storage option (Koen & Antunez, 2020). In addition, there is an increased interest and demand for integrated home battery storage, to avoid a connection to the electricity grid (IRENA, 2017). Of course, all renewable energy sources depend on the geographical location, therefore it may be better suited
If countries continue to double renewable energy systems, total electricity storage capacity is set to triple (in energy terms) by 2030 (IRENA, 2017). This means that electricity storage capacity will need to grow from 4.67 terawatt-hours (TWh) to 11.89-15.72 TWh, which is 155-277% higher than in 2017 (IRENA, 2017). It is predicted that by 2030, pumped hydro storage capacity will increase by 1,560-2,340 GWh and the storage capacity of battery electricity storage systems will increase by a factor of at least 17, compared to 2017 (IRENA, 2017).
With storage, there will be a loss in efficiency with every conversion, as seen in figure 1. But ultimately the challenges with operating the grid in an efficient manner may not even be comparable to the initial challenges with building the power plants, stringing all the wires, and implementing the controls that make up the present grid (Fares, 2015).