Ann: Valentia Funding Tranche Remitted, page-57

The long and the short of it is they don't have the funds to build a tower yet. Plus energy storage is very expensive. If you want to price yourself out of the market all you have to say is we want to build a solar updraft tower for $800 million and we want storage with that, for an extra I-don't-know-how-many hundreds of million of dollars. Despite the fact, that, out of ALL the existing basic renewable energy technologies, the generation profile for a solar updraft tower is more likely to match the demand profile (high demand in the day, low demand in the middle of the night) than any other.

Yes, in principle, energy storage is needed for increased renewable penetration into the grid, but if utility scale energy storage were affordable then all we would need would be existing technologies like solar and wind, the market would not need to build any solar updraft towers.