A possible solar solution
Why not combine solar and hydro technologies to get the best of both? Use farms of solar panels to generate excess electricity during the day and store it by pumping
water uphill from one large dam to another at a higher level.
By my calculations the average household could get all its daily electricity needs from a volume of water 10m x 10m x 2m (about 3 home swimming pools) held at an elevation of 50m.
(PE = mgh = 200000kg x 9.8ms-2 x 50m x 0.8 (turbine efficiency) = 78 MJ = 21.8 kWh)
Of course to do this on the scale which would provide the night time electricity needs for a city would be a big job, but not impossible. Daytime electricity consumption is generally higher than the night time load anyway.
Assuming you need to store a bit less than half this amount per household (e.g. 10 kWh) then you would need two reservoirs each 2.5 km long, 500 metres wide, and 80 metres deep to provide the night time needs of 1 million households.
Of course this depends on having suitable sites for the dams, but in principle it would work.
How many solar panels would you need to produce 20kwh per day for 1 million households ? A solar farm 6km by 6km would do it (assuming there is an average of 4 hours of strong sunlight per day), or a solar array 6m x 6m per household.
If every house had its north facing roof made of solar panel tiles we'd be well on the way!
The only real obstacle is cost. Enough solar panels to provide this power would cost between $50000 and $100000 per house at current prices.
(Of course if you could eliminate water heating (use solar), cooking (use gas), and heating (use gas) from your electricity needs then you'd need much less electricity generation capacity).
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