Pellets for Palaces

Posted Wednesday, August 21, 2013 in Sustainable Maine

Pellets for Palaces

by Paul Kando

How much would it cost Lord Grantham to keep Downton Abbey warm? -- someone asked on a cold Sunday evening last winter. Wondering about an answer, Drottningholm Palace came to mind. It is an 86,111 square foot 17th century edifice set in a beautiful public park, a stone’s throw from downtown Stockholm and the official residence of Sweden’s royal family. Until a few years ago the palace was heated with fuel oil, but the Swedes are dead serious about getting off oil, and one of King Carl Gustav’s and Queen Silvia’s jobs is to set a good example. So, in 2006, the heating system was replaced by a biofuel plant, which combines a wood pellet-fired boiler and a district heating grid. In addition to the palace, it serves a nearby research center and 22 other buildings. Two water-source heat pumps offer additional  flexibility. The new system has enabled the palace to abandon fuel oil in favor of wood pellets and rapeseed oil and move towards climate neutrality. Annual heating bills have been cut in half, carbon dioxide emissions are down by 90 percebt. The biofuel technology has also reduced electricity use from 1,300 MWh to 270 MWh per year – an 81 percent reduction.

Sweden is in many ways like Maine:  glacier-carved,  covered by pine, fir and birch forests, lots of lakes and even potato farms. The wood pellets that heat Drottningholm Palace are made from domestic forestry waste, just like the wood pellets I burned instead of oil last winter. My system is small – a pellet burning fireplace insert. I left the old oil-fired boiler in place, with its thermostat set so that it comes on only whet it’s extremely cold, should the pellet-insert struggle to carry the load. The scheme worked: I burned only $59 worth of oil last winter, and that because  for two weeks I was away. A ton of pellets is the energy equivalent of 118 gallons of #2 fuel oil. The per ton cost hovered between $217 and $280 all winter, less than half of what oil would have cost Btu for Btu .

Wood pellets are compressed wood particles. Their raw material is usually a byproduct of some wood processing operation. Hardwood flooring mills are one good example, but as interest in pellets grows, some mills make pellets from “round wood”, which is de-barked before processing. Since moisture in the raw material can cause problems under the high temperatures and pressures of pellet manufacture, it is first dried to a uniformly low moisture content of under 4 percent. Once the feedstock has been dried, a hammer mill breaks the wood into small, uniform particles. This makes for consistent pellet density and heating value. Dryness, of course, also ensures that the pellets burn well.

The pellets are extruded through special dies reminiscent of a potato-ricer or a pasta-machine. The high pressures (45,000 PSI) and temperatures (200 ºF) employed soften the lignin in the wood and bind the pellet material together without the need for adhesives. Once cooled, the pellets are  are packaged in bags or stored in bulk. Most people buy pellets by the ton (a pallet of fifty 40-pound bags), or in bulk to be stored for use in small silos. 

Using pellets is more bother than using oil. They must be stowed and kept dry. Pellet fueled devices are fully automated, but the hopper of a small heater like mine holds only a little more than a bag of pellets and needs to be regularly refilled. I top off the hopper twice in 24 hours on cold days and remove ashes from the stove at least once a week. After every ton of pellets the stove gets a routine cleaning, which takes about half an hour. At the end of the season, my friend Isaiah shows up from the Stove Shop at Damariscotta Hardware. He expertly slides out the pellet insert from its shell and, in less than an hour, inspects, vacuums and cleans every component. Slid back into place the unit is ready for next winter.

Pellet stoves and fireplace inserts involve less effort than wood burning stoves. Their fan-forced exhaust systems require no chimney; can be vented through a 4" stainless steel pipe. The fuel is dry and clean burning, so the fire always burns hot. There is no creosote problem. On the other hand, unlike wood-burning stoves, pellet burners require electricity. My fireplace insert operates  under computer control. It lights its own fire and regulates the rate pellets are burned, in response to a thermostat.

King Carl Gustav and I share a bit of common ground. We heat our respective palaces with locally made renewable fuel, harvested and made by local people. Unlike the money we had spent on oil, 100% of what we spend on pellets stays in the local community. We also save money: he $284,068, I about $1,500 per year.

But what about Lord Grantham? In the early 1900s Downton Abbey would have been heated with cord wood. Converted to oil, it might burn about 68,685 gallons of it per year,  just like Drottningholm Palace. In Sweden, that would cost Lord Grantham (at  $8.27 per gallon) $568,135 a year today. In England or Maine, where subsidized oil costs about $3.50 a gallon, he’d be paying $240,397.

I think I’ll stick with wood pellets – and my own palace.

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