Time to replace aging GTs in the US. With what?

The combustion turbine fleet is aging in the US. Closures have been announced. Many of the machines are more than 40 years old. Their heat rates are typically high and so are their NOx emissions. They are typically the last to be dispatched. The dash for gas in the 1990s saw a further ramp up of gas turbine capacity and it may now be time to consider replacing these machines.

Options for replacing combustion turbines are: New combustion turbines, reciprocating engines, solar, wind, and hybrids of the above. In a presentation at Power Gen International 2019, Edward Malley of the Natural Gas Hub compared and contrasted the options. Below are a few points from his presentation.

At $41 to $74/MWh levelized cost of electricity, gas combined cycles are the cheapest while at $160 to $267, solar rooftop is among the most expensive. Combustion turbines and reciprocating engines have a levelized cost of electricity of $152 to $206.

The globalized benchmark for battery-based energy storage (4 hours) has dipped sharply to $200/MWh while onshore wind has reduced to below $100. In terms of demand/response times, the combined cycle and reciprocating engines are on a par with minutes. While wind and solar alone are weather dependent, the addition of batteries would bring their demand/response times to a few seconds.

Based on a variety of factors, Malley’s conclusions are below.

Replacement of aging combustion turbines with new ones or reciprocating engines is economical. These options have unlimited run times unlike batteries. They are especially good options in remote locations where utility-scale options are unavailable. They are a good balance to wind and solar in grids where reliability is essential.