Ocean thermal gradient: Correlation
Prices it moves with, and why
The ocean thermal gradient between warm surface water and cold deep water is free and steady in the tropics, but its small temperature difference needs large heat exchangers and pipes, so equipment costs set its value.
No public price Ocean thermal gradient has no public monthly price series: A free natural flow; no market price, only capture costs.What its price moves with
Ocean thermal energy conversion plants are the converters for this gradient, and only small pilots exist, in Hawaii and Japan for example. Their value depends on cutting the cost of very large heat exchangers and deep pipes.
No public price for OTEC and salinity power, so the link is explained in words only.Heat exchangers in seawater must resist corrosion, so many designs use titanium plates, though aluminium is also tested. Titanium prices therefore affect the cost of using the gradient. Cheaper materials would cut the plant cost considerably.
Not enough overlapping price history to measure.Closed-cycle OTEC plants boil ammonia with warm surface water and condense it with cold deep water. Ammonia is a small cost, but the cycle depends on it. Ammonia is chosen because it boils at low temperatures.
Not enough overlapping price history to measure.Open-cycle OTEC flashes warm seawater into steam and condenses it as fresh water. On islands short of water, that by-product can be worth as much as the power. This makes the resource more valuable than power alone suggests.
Not enough overlapping price history to measure.Tropical islands where OTEC works best often run on diesel generators. High oil prices make the steady output of OTEC more attractive to these small grids. Each unit of OTEC power saves imported fuel shipped at high cost.
Not enough overlapping price history to measure.How to read these numbers
Correlation of monthly changes (the number in the coloured pill) compares how much each price moved, month by month, since 2006 or the first month both series exist. It runs from −1 to +1: near +1 the two usually rise and fall in the same months, near 0 there is no link, and a negative number means they tend to move in opposite directions. Above 0.7 is strong, 0.4 to 0.7 moderate, 0.2 to 0.4 weak.
12-month changes compare year-on-year moves, which shows whether two prices share the same cycles even when the month-to-month noise differs.
Price function is a straight-line fit of the two prices on logarithmic scales: price ≈ k × (partner price)β. β is how much this price moves, in per cent, for a 1% move in the partner over the whole period, and R² is the share of the variation the fit explains. Two prices that both drift up with inflation can fit well without any real link, so read it together with the monthly correlation.
Lead or lag checks whether the monthly correlation is clearly higher when one price is shifted by 1 to 6 months.
Correlation is not cause. The reasons on each card explain the economic link; the numbers show how strongly it has shown up in prices. Proxy series are US producer price indexes or related prices and can blur the real link.
Data: World Bank Commodity Price Data (Pink Sheet), October 2026; US Bureau of Labor Statistics producer price indexes, IMF primary commodity prices and US EIA prices via FRED, Federal Reserve Bank of St. Louis, retrieved November 2026. Calculations by this site.