The scientists in the article looked at 46 ozone-friendly coolants for turbo-expander plants. They checked their efficiency at different temperatures by creating a cooling cycle. Some coolants stayed efficient across various temperatures between 100-300°C. The best performers were R600A, R245FA, and R1233ZD(E), all with high efficiency. R600A was the top natural coolant, while R245FA and R1233ZD(E) were hydrofluorocarbon coolants. But each coolant had its own issues like high cost, explosiveness, or global warming potential.