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Why Our Antiquated Power Grid Needs Battery Storage
Lucas123 writes: Last year, renewable energy sources accounted for half of new installed electric-generation capacity (natural gas units made up most of the remainder). As more photovoltaic panels are installed on rooftops around the nation, an antiquated power grid is being overburdened by a bidirectional load its was never engineered to handle. The Hawaiian Electric Company, for example, said it's struggling with electricity "backflow" that could destabilize its system. Batteries for distributed renewable power has the potential to mitigate the load on the national grid by allowing a redistribution of power during peak hours. Because of this, Tesla, which is expected to announce batteries for homes and utilities on Thursday, and others are targeting a market estimated to be worth $1.2B by 2019. Along with taking up some of the load during peak load, battery capacity can be used when power isn't being generated by renewable systems, such as at night and during inclement weather. That also reduces grid demand.
Trouble is you need very large tanks of water, or to seperate them a long way. For instance a house might use 2 kWh overnight, that's about 7 MJ.
Round trip efficiency for pumped hydro system is around 88%, call it 100, and call g 10. So you need a tower or hill 350m high with 2 tons of water in it, or if you prefer, a swimming pool, 2*5*10m suspended 6 metres above your current pool. So, that's a fair bit of unlikely, just to power one house.
Most sensible big hydro locations have already been gobbled up, they made sense decades ago.