HCTGS v40 Africa. The Continent That Can Decide

Abstract Africa withdraws about 270 billion cubic metres of water a year for 1.4 billion people, and the continent's population is projected to reach 3.2 billion by 2070. Most of that withdrawal is agricultural and most of it sits in the basins — the Nile, the Niger, the Senegal, the Congo — where every additional litre is taken from a fixed quantity that already has users. This concept describes a source that adds rather than divides, placed where the coastline already is, and states what it does not reach as plainly as what it does. The architecture is a gravity-fed seawater thermal cascade. Magnesium burns behind a ceramic wall and carries the pipe it heats to about 2,200 °C, with process steam rising inside that pipe at some 20 bar against a wall at 1,500 °C; the steam there is the plant’s own condensate, so the hottest ceramic face stays clear of salt. Rotation comes from the hydrogen–oxygen burner, which meets the water directly, entering horizontally and tangentially below the waterline, with steam injected at twenty to thirty times the flame mass, and the column rotates. Chilled distillate is sprayed as a fine mist at the crown, and the vapour condenses in flight rather than on any surface, collapsing near 1,600 to one close to atmospheric pressure and approaching 7,700 to one at the sub-atmospheric design point. That collapse draws the next vapour mass upward without a pump. The plant is described as three coupled circuits on two levels — the thermo-mineral cascade on the water side, the tower on the steam side, and the product-water path to the cistern — with the column at reference output raising 11,574 kg/s of steam, 26.1 GW of latent duty. Condensation heat returns down the falling water and preheats the feed, placing the purchased external heat at 0.65–0.87 GW, an equivalent gain-output ratio of 30 to 40 against 6 to 15 for multi-stage flash, and a residual cooling stream of 12–60 m³/s. Heat leaves through eight descending stages, from specialist ceramic at the top to a cupola at 4 °C, and the dissolved minerals are separated in the same vessel and the same column that make the water. Fresh water is the remainder. The reference geometry is a 600-metre structure of 50 metres diameter at 1.0–1.5 GW continuous, with freestanding tower, deep shaft, hybrid, mountain shaft and floating platform as site-chosen configurations. The African reference output is 1,000,000 cubic metres a day, at 60–70 % of the tower’s capacity ceiling of 1.4–1.7 million, with a regulating range of 0.59–1.0 million and first towers running at 0.7–0.9 million for twelve to eighteen months. One installation at reference output yields 365 million cubic metres of water a year, 8.76–13.1 TWh of electricity, 175–263 kilotonnes of hydrogen at the same capacity rather than in addition to it, 547–703 kilotonnes of magnesia, salt at a capacity of 9.86 million tonnes, and calcium, potassium, bromine, boron and lithium fractions. At 0.365 billion cubic metres per tower-year, current withdrawal corresponds to 740 towers, the 2050 population at unchanged per-capita use to 1,230, the 2070 population to 1,640, and 2100 to 2,050. These are a ceiling if every litre withdrawn today were replaced by the sea and a floor if prosperity raises per-capita use; neither is a build order. The plan is the build-out curve rather than the ceiling. Each tower carries 25,000–40,000 person-years of direct and indirect construction labour over two to three years, with a peak on-site crew of 2,000–4,000. A build rate of 40–60 towers a year at peak reaches 740 towers around 2043, 1,230 around 2054 and 1,640 around 2062, with the first five years slower and the first hundred towers the hardest. CAPEX is 0.65–1.15 billion US dollars per tower and OPEX 180–280 million a year; across 1,640 towers the programme is 1.07–1.89 trillion dollars over thirty years, or 36–63 billion a year in orders. Employment is stated as 41–66 million construction person-years, 490,000–820,000 permanent operations posts, and — conditional on tenure, credit and mechanisation — 8–15 million agricultural jobs over the build. Five field conditions decide whether a pilot starts at all, and they are treated as the substance rather than as caveats. Africa's electricity is more than fifty largely unconnected systems, so the continental figure is a ceiling only where corridors exist. The magnesium loop must close from the tower's own brine within twelve months of first fire, which is handled as a fuel gate rather than a title gate: the plant belongs to the host from commissioning, the operator advances the first charge and holds the burner line, and a missed gate extends the operator's obligation rather than the host's. Land along the corridor is held before it is crossed, under customary, community and statutory title with existing procedure and named counterparties. The coastal source is an addition alongside the basin rather than a replacement of it. And operating cost falls in hard currency, which an export mineral stream or an indexed tariff has to carry. The financing and ownership structure is set out in five models, with a pension mandate allocating 20–30 per cent of equity to the host country's national fund and the African Development Bank, locked for twenty-five years, a state golden share, packages bid separately so that no supplier holds the tap, a second-sourcing rule for any package that could throttle the plant in year fifteen, and a legal seat chosen against three stated conditions and re-bid like any other package. Industrial development is treated with the Central European convergence record as the counter-case: consumption arrives in months, convergence takes decades, and what separated the countries that closed the gap was ownership and an institutional anchor rather than appetite. The oxide carries the plant and the metal has to make its own market. World primary magnesium production runs at roughly one million tonnes a year, so the metal a single tower releases is a significant share of world supply from one structure on one coast, and a metal ladder of six rungs is stated as conditionals rather than as a market: titanium and zirconium sponge, aluminium alloying and steel desulphurisation, components in salt water, lightweight structures, magnesium as an energy carrier, and resorbable implants — each with the barrier that holds it and the condition under which it falls. The first rung is already an African export: the heavy mineral sands of the southern and eastern coasts leave as ilmenite and rutile, and the reduction leaves with them, because the magnesium chloride electrolysis that the Kroll loop returns is the largest single cost block in sponge and a cluster on the same coast runs that cell already. No rung is booked as revenue: the metal is capacity, and the oxide carries the plant. The open parameter is named. The conversion efficiency of the vortex stage is calculated at 0.277 and is settled by measurement under load. A pilot of 10–15 million US dollars over two to three months settles it, together with eight further parameters including whether the cascade can ingest a licensed membrane-plant concentrate and finish the separation. Everything the pilot produces is published. Technology readiness is stated conservatively: components individually established at industrial scale, their integration in this configuration not. Magnitudes are theoretical design estimates offered for independent assessment. Published under Creative Commons Attribution–NonCommercial–NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Commercial use by separate agreement.