Renewable energy model – Burlington Vermont's Joseph C. McNeil Generating Station
While continuing to participate in the discussion associated with Lester Brown’s guest post at Grist titled Waste of Energy: The Flawed Economics of Nuclear Power I asked for the contributors to suggest real world examples of places that currently depend on the “soft energy” technologies that have been touted by Amory Lovins and friends for at least 35 years. If those technologies can really replace fossil fuels and nuclear power, as their proponents suggest, then by now it should be possible to have operating examples so we can evaluate the effects on the environment and the economy of making that kind of choice.
So far, I have received one response to that request for a renewable energy model. Richard suggested that I take a look at the 50 MWe wood fired power plant in Burlington, Vermont. Since that city has about 50,000 residents, the plant has the potential to supply most of their electrical power needs. I took Richard’s suggestion. You can find the results of my quick study of the plant by clicking on the “Read the rest of this entry” link below.
@Richard – Thank you for the pointer. I have just spent a little time learning more about the Joseph C. McNeil Generating Station in Burlington, VT. If that is a good renewable energy model there are some interesting lessons to be learned.
The plant was financed through a bond issue approved by voters in 1978. The initial capital cost was $67 million, $13 million less than the original budget estimate. Plant capacity is 50,000 kilowatts, so the initial cost was $1,340 per kilowatt in 1981 dollars. (At an average annual inflation rate of 3% that would be roughly $3,000 per kilowatt today. That inflation number is just a guess.) The plant employs 40 people as foresters, equipment operators, fuel handers and maintenance crew.
In 1989, the plant was modified to be able to burn natural gas supplied on an interruptible basis during the months of May-November when gas is typically cheaper because it is not in demand for home heating.
At full power, the plant consumes 76 tons of wood per hour. 70% of the fuel comes from whole tree chipping operations that capture wood from forestry harvesting operations. That wood is material – like tree tops, branches, and malformed trees – that is not useful for manufacturing processes. The wood is chipped in the forest and hauled to the plant using diesel powered trucks or locomotives.
25% of the fuel is waste material from other local sawmill operations that would otherwise be sent to a landfill, and 5% is urban non treated wood waste normally dropped off at the plant by local residents. The total wood fuel consumption is about 180,000 tons per year, enough to supply about 2400 full power hours (plant capacity factor of 27%). The primary reason for adding the gas firing capacity was to increase the plant’s capacity factor so that the capital asset could be used a larger portion of the year.
When operating on wood fuel, the plant thermal efficiency is 26%, on gas it is 31% due to the higher firing temperature. The hourly fuel consumption using gas is 550 million BTU per hour, at the current gas price of $7 per million BTU, that gives a fuel cost of 7.7 cents per kilowatt hour when operating on gas. The station can also burn fuel oil or a combination of gas, wood and fuel oil. Here is a quote from the plant’s wood fuel facts page:
“Consumes 180,000 tons of wood per year, which displaces 360,000 barrels of imported oil”
The plant uses 42,000 gallons of cooling water per minute, and also has a need for several thousand gallons per day of pure water for steam plant make up. (Note: Though steam plants are ideally closed systems that do not consume new water, operational reality is that steam plants inherently leak and need make-up water that is very pure initially and has corrosion control chemicals added. Boilers also require a regular water consuming “blow down” to reduce sludge build up. The water that leaks or used in blow downs has to be treated to remove the chemicals before it can be released to the environment.)
The smoke stack that provides part of the fuel waste handling system is 257 feet tall. The wood ash residue is sold as an ingredient in fertilizer and road base material.
Another useful fact comes from the DOE’s biomass for electricity generation analysis page:
“Of the estimated total resource of 590 million wet tons, only 20 million wet tons (equivalent to 14 million dry tons, or enough to supply about 3 gigawatts of capacity) is available today at prices up to $1.25 per million Btu.”
Editor, Atomic Insights
One thing that I did not mention in that response to Richard is that there is no indication that Burlington, VT is isolated from the rest of the regional power grid. The plant may supply enough power to meet the needs of the residents in that city, but there is no way to show that the actual electrons consumed in the city come from that plant and not from some other plant operating on the grid. Of course, in Vermont, grid power is very clean power – most of it comes from Vermont Yankee Nuclear Power Plant and from Canadian nuclear and hydro power.