We approximate a Tower Design Coefficient of 1.2 when CO₂ is used in a closed-circuit cooling tower instead of glycol or R22. This 20% increase in cost is estimated due to the higher pressures of CO₂ condensation. The BAC PC2 condensers are rated for 2.8 MPa maximum working pressure, while we expect typical CO₂ condensing pressures to be about 6 MPa, and possibly as high as 10 MPa. Building equipment for higher pressures involves thicker tubing walls, which both increase the cost of material and decrease the heat exchanger effectiveness, increasing the cooling tower size required.