Does Australian renewable energy save the earth – or just cost it?

The further south we go, the worse this winter solstice dilemma becomes. The further north to the equator, the more the equinox scenario applies.

Of course, if we relax the assumptions about cloudy and foggy days and light intensity, the capacity multiple and cost dilemma for solar gets worse in all cases.

What about non-base-load power?

The daily power demand cycle adds peak period demands to base-load demand. These include early morning demand and evening peak demand, plus different summer and winter demands (cooling and heating demand, respectively). In all cases, more generation/storage capacity will be needed to deal with demand peaks.

If we use renewables to meet these peaks, the generation/storage capacity multiples relative to fossil-fuel peaking plant will depend on how much these peaks coincide with solar power generation. We also need to determine these capacity multiples to cover the weakest solar power generation period (the winter solstice).

In winter, the intra-day demand peaks will tend to occur when the sun is not shining or is only shining very weakly.

So daily non-base-load solar power generation will increase the generation/storage capacity multiples needed, relative to fossil-fuel capacity (eg, gas peakers).

What about wind, hydro and thermal solar power?

Wind, hydro and thermal solar (the new rage for SA?) renewables are also intermittent, but with different (usually longer) cycles than the daily solar cycle.

In general, the longer the non-power generation period in their cycles (no wind, no stored water, no sun/molten salt) the larger the generation/storage components required for reliable renewable energy. This generation/storage capacity multiple can be very large where generation power is not available for extended periods. With an interconnected grid, spatial variations in renewable generation can reduce required capacity multiples, but usually with increased transmission losses.

What about the other new (Commonwealth) rage, 'pumped hydro' ('Snowy 2.0')?

This idea already operates, as anybody watching, say, the Guthega Pondage over a summer day will know. It might make economic sense (given the capital investment) if arbitrage is possible between cheap base-load power in the small hours of the morning to pump water uphill, to be released (say) during peak power demand in the afternoon/evening of the following day or later on.