Sept. 26, 2007 — The V.I. Water and Power Authority broke ground Wednesday morning for a long-awaited waste heat-recovery boiler at St. Croix’s Estate Richmond power plant.
“This is really a milestone for WAPA,” said Gregory Willocks, WAPA’s chief engineer and director of water distribution. “This generator benefits us in three major ways: One, it’s more efficient. It will save fuel. Two, it emits less pollution because it lets us burn less fuel. And three, it increases our plant’s reliability because there is an additional source of steam.”
Local radio, television and print media came out in force to see the spot being prepared for the energy- and money-saving device.
What is a waste heat-recovery boiler and why does St. Croix need one? The power plant itself has a number of boilers and a number of generators. The boilers are all heated with fuel oil, and recent jumps in oil prices have caused the fuel surcharge on resident’s utility bills to skyrocket. With the regular generators, oil-fired boilers send super-hot, high-pressure steam through the generators, spinning them to generate power. The exhaust from the burnt fuel oil goes out the plant’s smokestacks.
Waste-heat generators work by passing the super-hot exhaust gases over what is essentially a giant radiator working in reverse. The gases, which vary from 540 to 960 degrees Fahrenheit, flow over and past a bank of finned tubes. The tubes run up and down inside the casing, just like the tubes in a car radiator.
As the gases pass the radiant fins on the tubes, the water inside turns to superheated steam. One of the recovery boilers will generate 23,000 pound of steam per hour, according to Nellon Bowry, WAPA's interim executive director. That steam then gets funneled into the existing generators to generate electricity.
The steam-recovery boiler generates more than half as much electricity as the original boiler. That is, the oil-fired burner boils a certain amount of steam and generates a certain amount of electricity for each barrel of oil. The hot exhaust, instead of being piped out into the air, then gets used to boil enough steam to generate 50 percent more electricity.
After the super-hot steam is used to generate electricity, it has lost much of its heat and pressure, but it is still very hot. It is then used to boil seawater in tanks kept under vacuum for WAPA’s seawater desalination plant. This cools down the steam more. Next the steam is cooled down one more step by piping it through more cool seawater, which returns it to a liquid state. Once liquid again, it is piped back into the boilers to be heated up again, starting its closed cycle all over.
“This project is a major undertaking for WAPA in several respects,” Bowry said. “It is the most complicated project since I’ve been at WAPA. And without a doubt it is the most expensive project. I would like to challenge our engineers and staff to finish this on time and on budget. It is a critical project not only for us, but for the rate payers. Any fuel savings will impact the infamous LEAC."
LEAC stands for levelized energy-adjustment clause, a fuel cost surcharge.
WAPA estimates the total cost for the new St. Croix steam-recovery generator at about $34 million. Bonds issued this year finance $26.2 million, while funds remaining from bonds issued in 1998 and 2003 account for the remaining $7.9 million.
WAPA customers will pay a surcharge which, for typical residential use of about 500 kilowatt hours, should amount to about one dollar a month. That charge begins next October, around the time the generator is supposed to come online. Customer bills should go down significantly as soon as it becomes active. If oil prices remain above $60 a barrel, the increase in efficiency would save WAPA $12 to $15 million a year on St. Croix. That amounts to a savings of $240 to $300 per year for every household electrical-service account in the territory.
“We are really excited finally, after years of planning this project, to have it come to fruition,” said Al Franklin, a WAPA board member, at Wednesday’s event.
WAPA has contracted with a Missouri company, Nooter Eriksen, to build the St. Croix generator.
There is already a heat-recovery boiler on St. Thomas and one on St. Croix, although they do not have as much capacity as the one now being built. After this one is complete, a second is planned for St. Thomas, as well.
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