Ray (seated) shows us the control room. There are about a dozen different computer terminals, some with proprietary software to run the turbines, some with BOP software ("Balance of Plant" - non-proprietary). Red icons indicate active parts of the system; green, inactive. One can ramp a turbine up or down simply by clicking its icon and typing a different MW value (e.g. 180 MW instead of 176 MW).

Delta Energy Center is an 880-MW combined cycle natural gas plant (meaning it includes both gas and steam turbines). To the left and middle of the picture, mostly out of view, are the three gas turbines. Their hot exhaust gases are pumped through the pipes you see in the middle of the picture, into a boiler that produces steam to power the steam turbine (housed in a building out of view on the right).

We walk toward a building housing one of the the three gas turbines. These are Siemens-Westinghouse gas turbines, each rated at ~200 MW. Currently one of the three is down for maintenance. That is the turbine we will visit, because it will not be as noisy and as hot as the others!

A similar view as above. You can now see two of the three buildings housing the gas turbines. The one in the foreground is CT#2, the turbine that we'll visit because it is currently non-operational.

This is the compressor for CT#2. Because the turbine blades must be kept in pristine condition, the air has to be stringently filtered. It is then compressed and delivered to the combustion chamber. This is a 17-stage compressor; by comparison, most jet engines have only 4 stages. Plant manager Rob Parker comments: "Power plants don't lend themselves too well to tours - they're mostly just a bunch of big gray boxes."

Though it doesn't look like much, this is one of the gas turbines. It is heavily padded for insulation and protection. The white pipes deliver natural gas to the 16 "cans" (combustion chambers). Combustion temperature is about 2400°F (1300°C), which is great for efficiency, but reaches the limit of the currently available materials - if the temperature got much higher, the metal would actually melt.

This compressor is pulling in such a huge volume of air (2 × 10⁶ lbs per hour) that it is sucking Rob's hard hat right against the mesh. Though compressors are an essential component of the system, they account for a large fraction of the efficiency loss: at this plant, about 60% of the power generated by the gas turbines goes to run the compressors. That means the gas cycle (Brayton cycle) at this plant could not be more than 40% efficient; in fact, it is closer to 30%.

Ben, on the verge of blowing away, demonstrates the rate of air flow into the compressor.

Now we're standing on the roof of the building that houses the steam turbine. The boiler receives hot exhaust gases from gas turbines 1, 2, and 3 (laid out sequentially in the background). To our left, you can see one of the large pipes that transfers the exhaust gases.

Here is the steam turbine. This turbine is operational, so it is hot and noisy inside the building, and we are barely able to talk. It's actually a three-stage turbine (high, intermediate, and low pressure; the low pressure is only 300°F), with a total capacity of 330 MW. Without the steam turbine to receive the hot exhaust from the gas turbines, none of the three gas turbines can run. Therefore, it is imperative to keep the steam turbine online whenever possible.

This is the breaker yard, where the voltage is transformed and then the electricity is delivered to the grid. The turbines generate at about 18,000 V; this is stepped up to 230,000 V for long-distance transmission. Because of the dire financial consequences of any malfunction, the breaker yard is designed with multiple layers of redundancy.

Delta Energy Center is intentionally situated next to a wastewater treatment center, so that the treated water from the wastewater plant can be used in the cooling towers of the gas plant. The wastewater plant needs to get rid of its tertiary water (for environmental reasons, it's not allowed to dump the water in the San Joaquin River, which you can see in the far distance). And the gas plant needs a lot of water to evaporate in the cooling towers (5 × 10⁶ gal/day). So it's an ideal partnership! You can see one of the wastewater ponds on the right, just under the railing.

Here are the cooling towers (panning to the right from the previous picture). A fine mist is falling through the black lattice that you can see at the bottom of the structure. Believe it or not, the second most expensive operating cost for the Delta Energy Center - after the cost of the natural gas itself - is chemicals for maintaining the cooling tower (e.g. sodium hydrochloride). The water must be maintained at the proper pH, without biological contamination.

The boiler water is even more carefully maintained than the cooling tower water. Any impurities in the steam would damage the turbine blades. So this water passes through treatments to remove suspended solids (reverse osmosis) and dissolved solids (ionic exchange). Even this ultra-pure water has to be continually replaced (about 1% per hour), as it accumulates impurities from the pipes in which it circulates.

We all greatly enjoyed the tour and are immensely grateful to Rob Parker for being so willing to answer questions! From L to R: Ben, Stefan, Spencer, Leneve, Rob, Jeff, and Dan. We are standing in front of CT#2, which is well on its way to being up and running once again, but which in the meantime provided us with the perfect opportunity to see a gas turbine up close.

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