As usual, I recommend Bob Hargraves excellent blog post on the visit. His post contains videos of logs being fed into the chipper, chips on a conveyor belt to the silo, and a semi-truck load of chips being emptied into a chip pile, from which they will be loaded into the conveyor belt. (I include that video below.) The plant buys about one-third of its wood as logs and chips them on site. The other two-thirds of its fuel is purchased as chips.
They use trees that are not good for other uses, such as furniture or firewood.Most of the trees they use are small pines. This is the first powerplant I have every visited that smelled wonderful, like a Christmas tree or a pine forest. Nothing like having tons of pine chips around for a truly pleasant odor. The plant burns 200,000 tons of wood chips per year. Our host, Chuck Theall, was incredibly patient and completely knowledgeable. I include one of Bob's videos.
Okay, I admit it. I was very comfortable in this environment, because it was a "regular" power plant, and Theall is a man who was in the Nuclear Navy. Somehow, I expect power plants to be run by Nuclear Navy people. Shows something about me, I guess!
It's a Heat Engine
This wood chip plant is a heat engine, which means they have to keep fuel on hand. The picture below shows their current log pile, which is about two weeks supply of logs.
During mud season, there are weight limits posted on the local roads, and logging trucks have a hard time traveling. Theall builds up a six weeks supply of wood and chips in preparation for mud season.
We Keep Running
I found the fact that this plant keeps running very reassuring. The exact figures are proprietary, but Theall said the plant gets paid about 5 cents/kWh, but his fuel costs are about 4 cents/kWh. These are in the price range of power from other types of plants, unlike the 24 cents and 30 cents/kWh of the solar farm, for example. Theall said that the sale of RECs (Renewable Energy Certificates) was an important part of the plant's ability to be profitable. He also pointed out that all the plant's fuel expenses are paid out to local people. The money goes right into the local communities, to loggers, land-owners, and their families.
Every day, the plant tells ISO-NE (the grid operator) whether it is on-line or having a problem. (It is usually on-line, with one or two weeks off per year for inspection and repair.) After that call to ISO-NE, the plant contracts to supply a certain amount of power to the grid that day. If it can't supply that power, it has to pay ISO-NE for replacement power. I found this type of contract and requirement a change from the discussion of capacity factors (14% at solar, 35% at wind) in the other facilities.
Pollution Control and By-Products
The plant has excellent pollution control equipment for fly-ash and NOx.
Electrostatic precipitators catch the fly-ash: you can see the big ash-hopper below. The ash is sold as a soil amendment. It brings alkalinity and minerals to the soil. They also sell tree-bark to landscapers.
The plant burns hot (1600 F) enough to make some NOx. It controls NOx with a selective catalytic reduction control system with an ammonia feed. I could include a picture, but I think a picture of a tank of anhydrous ammonia is somewhat boring.
Lovely, but Not Enough
I was impressed by the plant, by the pollution control equipment, by professionalism of those who ran it, by the sweet smell of pine. Alas, I was more surprised than impressed by the turbine hall. It's a perfectly nice turbine, but it is only 19 MW, which looks tiny to people like me who are used to coal or nuclear plants. At twenty MW, it would take 31 plants like this to make as much power as Vermont Yankee.
This is a serious, well-run plant that lives up to its committments to supply power. It is a benefit to its community and I am very glad I visited it. All in all, I got a very positive impression of biomass.
Krista Langlois of the Valley News wrote a front-page article about our trip in the Valley News October 5. The article is not on-line, but I will quote the final paragraphs:
While those in the ILEAD class are serious about getting reputable information in an industry in which misinformation abounds, one draw of the class is likely the field trips.
As Hartford resident Meredith Angwin summed it up: "I just like power plants."
It's true. I like power plants. I like electricity. I feel privileged to have spent so much of my lifetime in the electricity business, which is so important to human health and happiness.
All pictures are my own. Video from Robert Hargraves.