Monday, October 10, 2011

Energy Safari Visits Woodchip Plant

On October 4, the Energy Safari class visited Springfield Power LLC, a wood-burning power plant in Springfield New Hampshire. The plant is very visible from Interstate 89, at Exit 12A, Georges Mills. It is rated for 19 MW, and usually makes that amount.

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.

Turbine below.

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.


Anonymous said...

I've often wondered about the "scalability" of wood-fired power plants.

Meredith mentioned it would take 31 plants the size of the one you toured to replace Vermont Yankee. That doesn't actually sound un-doable to me. The big question is fuel supply.

Granted, Vermont is a relatively rural state with a much lower population density (and total population), than many other states, so I think wood-power is, perhaps, much more likely to be a viable alternative in Vermont.

But, I have to wonder - how much of its power could Vermont get from wood, before the rate of harvesting wood becomes too large to be sustainable?

I'm all for the idea of somewhat increasing our wood power plants, but if we do that, we should be pretty careful that we don't over-extract wood. Ohio is a state which, I think, could get no small amount of power from wood - we have a pretty high population density, though (10th in the nation, if you can believe it, according to wikipedia), but we also have a LOT of woodlands. But, I'd hate to see 50% of our woodlands cut down for power.

Meredith Angwin said...

Jeff, that is a really important point.

I spent this morning leading the Energy Safari class, starting with a review of last week's visit, and this was the main issue we talked about, considering the Springfield plant. Okay. Here we go. Doing the numbers.

The Springfield plant burns 200,000 tons of wood to make 19 (say 20 for ease) MW of electricity on a regular basis. The wood it burns is wet. On the web, I looked up weight-per-cord for wet wood and got about 4000 lbs, or two tons, per cord. The table I found showed most types of wet wood weighs about that much, but dry wood varies a lot, especially between pine and hardwood.

Okay, at two tons per cord, that would mean the Springfield plant burns 100,000 cords of wood a year.

In class, we did a cross-check on that number. Someone in the class said that one of the people at the plant said the plant burns 10 cords an hour, which would be 90,000 cords a year if it ran non-stop. So, 100,000 cords is the right ball park.

More to come..

Meredith Angwin said...


Now comes the interesting part. A year ago (see my post on our press conference)
the Coalition for Energy Solutions reviewed a VPIRG report on substituting renewables for Vermont Yankee. Within our report, I was mostly responsible for the biomass section. I needed to find out how much wood grew sustainably in Vermont. So, I tried to find out. Hit a dead end.

It turns out that foresters don't like to commit themselves in print. "It depends on the soil, on the weather that year, on the pine beetle, on the..." So, I interviewed people in the state forestry office, township forestry offices, and a superb magazine called Northern Woodlands. I promised them I wouldn't quote them by name. Under these circumstances, I got a consensus on sustainable growth in Vermont.

Vermont forests grow about one-half cord per acre, sustainably.

So, 100,000 cords of wood can be sustainably harvested from 200,000 acres. In comparison, Vermont is 6,000,000 acres, and the Green Mountain National Forest is 400,000 acres.

So yes, we can get more biomass electricity in Vermont, But not anything like 30 times the biomass. Also, people in the class pointed out that we are looking to biomass to displace oil for heating homes and schools, etc. There's going to be a competition for it.

It is possible to have more wood-fired power, but it is not possible to replace Vermont Yankee with it.

Anonymous said...


Thanks for the replies. Interesting stuff. My "gut instinct" was that you couldn't provide nearly enough power for the nation, or even most States from wood, but it's nice to see some real numbers put to that. Interesting that Vermont can't power itself with wood, sustainably.

If Vermont can't do it, there's probably almost nowhere in which that would be possible.

Meredith Angwin said...

Jeff. This guy doesn't like coal or nuclear. But he sure doesn't like biomass! An interesting perspective in a local paper today