Is affordable, 24/7-reliable, electricity ever possible again?

In 2022-23, the NEM supplied 520,000,000kWh per day on average. Suppose Australian EVs grow to 1,000,000 by 2027 (an electric vehicle association target). Net of EV battery usage for owner-transport, assume, on average, 40% of EV battery storage is available for diversion to grid support. Way too optimistic? That's 40,000,000kWh, or about 7.7% of daily NEM power supply.

Not so fast.

If grid support is demanded of EV owners who have paid for their EV batteries, how will they react? One future buyer response is refusal to purchase EVs. That would undermine ambitious future EV targets. For those still buying or owning EVs, would they unplug them from their chargers when they expect their own stored EV power to be commandeered for grid support?

Like other lithium-ion batteries, do EV batteries last about 10 years? Must EVs be replaced every ten years? Who buys the old ones? Is resale value of old EVs now very low because replacing their batteries is costly? Isn't the second-hand EV market showing this?

Could very heavy restrictions on motor vehicle ownership and use be needed to make this idea work? Then Cuba-style ageing of fossil fuel cars as owners use them for longer to avoid EVs?

Chemical battery developments beyond lithium-ion. There's lots being spruiked in this area. I've already assumed battery storage costs for electricity fall to just 10% of SA's Hornsdale 'big battery'. Happy to react as new technical breakthroughs emerge. When? Time – possibly a long time – will tell. We can't, for sure.

Renewable solid gravity batteries. This notion is mechanically-intensive, physically large, and, I suspect, very energy-negative in net terms. Google it. Are proponents serious? In my opinion, this is a fanciful notion, with little chance of being a power storage device at any scale.

Real-world gravity battery options. We do have water-based gravity batteries operating today. The Guthega/downstream turbine generator facility in the Snowy Hydro system is one example.

Upstream water from the Snowy river is allowed to fill the Guthega Pondage during (human) off-peak demand periods. Excess inflows are allowed to flow unrestricted over the dam. Dam storage can be gravity-discharged, feeding downstream power turbines, during on-peak electricity demand (typically in the evening). That can be profitable for the Snowy scheme, via high peaking power prices. As a 'peaker' generator, it also softens prices downstream for users.

Win-win? In suitable locations, with reliable water flow, yes. Can be a long-lasting option too. Guthega Dam was completed in 1955.

Without enough free water, however, hydro power supply is cut off. As in Tasmania now.

Net zero gravity battery options. 'Pumped hydro' relies on releasing water from an upper dam (where potential energy is stored) to a lower dam (generating kinetic energy through power turbines as it does so). That water is then pumped up again to the upper dam, and the process is repeated as power is needed.