Energy of the future 

PG&E's decision to close the Diablo Canyon Nuclear Power Plant was based on math—economics—not environmental concerns, Mark Henry ("Mathematical conundrum," Aug. 17).

From the beginning, the costs of Diablo were daunting. Construction costs projected at $2.2 billion escalated to $5.4 billion because of seismic issues and human error.

It is the largest single generation system on the California grid. Government rules require that the grid be capable of withstanding the sudden loss of its largest single source without loss of load by holding a "spinning reserve" equal to or greater than, in Diablo's case, the 2,240 megawatt capacity. This means the nuclear plant must have "one-for-one backup" at all times, and this backup must be dedicated to reserve duty in case of an outage.

The Helms Pumped Storage Plant east of Fresno is the main spinning reserve facility for Diablo. When Diablo Canyon retires, the system requirement for spinning reserve will be cut significantly—minimizing GHGs (greenhouse gases)—and a portion of Helms will be available to supply system flexibility without restriction, providing power when the sun's not shining.

In the Joint Proposal to Retire Diablo Canyon, PG&E concluded that "the most effective and efficient path forward for achieving the goal for deep reductions of GHG emissions is to retire Diablo Canyon ... and replace it with a portfolio of GHG free resources. This will be the reliable, flexible, and cost-effective solution for PG&E customers."

Flexibility in generation and a demand-response system are the energy choices of the future.

Dev Young

Los Osos