In Roald Dahl’s famous children’s book “Charlie and the Chocolate Factory,” a handful of guests are given a once-in-a-lifetime opportunity to look inside the operations of a place that many relied on without knowing how it works or what it does.

While not quite as mysterious as Wonka’s chocolate factory, Homer Electric Association’s Combined Cycle Power Plant in Nikiski is not often visited by members of the public, even though it provides power to nearly everyone living on the peninsula. On Thursday, HEA offered a rare opportunity for the public to tour its Nikiski power plant — no golden tickets necessary. The two tours were led by Larry Jorgensen, director of power, fuels and dispatch, who unfortunately left his purple suit and top hat at home. The tours took place on the same day as HEA’s annual meeting of the members, giving HEA members an opportunity to experience what it takes on a day-to-day basis to keep the lights on.

The Nikiski Combined Cycle Plant generates power through natural gas combustion as well as through a steam turbine for a total potential output of 80 megawatts of power, and Jorgensen said that the actual output varies from month to month. In a month like May where heaters aren’t being run and fish aren’t being processed yet, the output averages around 60 megawatts. The plant has generated the bulk of HEA’s power supply since January of 2014, but with its location nestled right next to the Marathon refinery in Nikiski, most people could drive right by it and not realize it’s there.

After walking up a narrow flight of stairs to a conference room, tour participants listened to a brief introduction from Jorgensen before being outfitted with the noise-blocking headphones, hardhats and safety goggles required for the bulk of the tour.

The first stop was the control room, which was decked out with wall-to-wall computer screens, control panels and camera feeds and was significantly quieter than the rest of the plant. No headphones were needed yet. Jorgensen said that the plant’s activities are monitored from the room 24/7. The system only requires one person to man the control station at any given time, and Jorgensen said the plant typically only requires a handful of employees to operate — four crews consist of a total of 10 operators and four shift supervisors.

One of the most important aspects of power generation that the control room monitors is the output frequency, which has to stay at around 60 hertz (cycles per second.) As people turn their power on and off throughout the day and the load on the plant changes, the plant’s systems adjust the speed of the power output in real time to maintain a consistent 60 hertz frequency. Jorgensen said that this consistency is important because if the output frequency gets too low, the system could shut off.

Once the control room had been covered, the visitors donned their headphones and entered the belly of the beast, also known as the combustion turbine room. Jorgensen described the combustion turbine as a “jet engine in a box.” The turbine took up most of the space in the large warehouse-like room, and even with protective headphones the roar of the machine could be heard loud and clear. Jorgensen said that the waste heat generated during natural gas combustion exits at 1,000 degrees Fahrenheit, which is then captured by a heat recovery steam generator (HRSG) and used to drive a steam turbine, generating additional power output. The HRSG — pronounced “her-sig” — essentially allows power to be generated twice from a single combustion cycle and is an efficient way to maximize the output from the natural gas.

The water that is boiled for the steam turbine has to be completely free of impurities, which is where the water treatment facility for the plant comes into play. Here, Jorgensen explained that since the water is used for multiple cycles before being discarded, qualities such as Ph balance, purity and conductivity are constantly being monitored and adjusted. If any impurities such as sulfur or iron are in the water, they plate out on the turbine itself as the water turns into steam. This can lead to maintenance and cleaning issues and impact the overall efficiency of the turbine.

Every power plant needs multiple contingency plans in place in case the unexpected happens and the turbines stop firing. For the Nikiski plant, one of those backups is an 8,000-gallon diesel generator. The generator burns diesel at a rate of about 149 gallons per hour, so Jorgensen said its use is primarily reserved for maintenance operations that require one of the turbines to go offline. That kind of fuel efficiency also makes it pretty impractical for road trips.

As Jorgensen mentioned during the tour, the water that is boiled to drive the steam turbine is used over multiple cycles. The problem with steam, Jorgensen said, is that there is no good way to recapture it. The solution to this problem at the Nikiski plant comes in the form of a massive air-cooled condensing system that uses 36-foot diameter fans to push the steam up into a set of large radiator fins, extracting the heat from the steam and turning it back into liquid form that is then able to be recaptured. Jorgensen led the tour up into the condenser and explained the cleaning and maintenance procedures as guests peered down at the massive fan blades turning slowly below them. The fans were slowed down significantly for the tour, as they normally push air up at about 45,000 cubic feet per second.

As the tour concluded, Jorgensen brought the guests into a conference room for lunch and to answer any questions about the plant. Heather Smith with HEA said that the tours this time around filled up quickly, and as a result the association will likely organize another set of tours in the fall.

One of the guests offered a suggestion for future tours: “Besides telling people to wear closed-toe shoes, you should also warn them about the heights!”