Page 6 RAIN January 1979 -WOOD Wood-Fueled Power Generation: A Potential Source of Energy for Northern Michigan, Michigan Public Service Comm_ission, 1977, free from: Fuels Planning Office Department of Commerce 6545 Mercantile Way P.O. Box 3022 Lansing, MI 48909 More and more states are turning to their local renewable energy resources and discovering, as Michigan does in this study, that they can provide a large percentage of even today's excessive energy use. So far so good. But most such studies are focussed muc::h too narrowly to provide really meaningful answers or even to raise significant questions forcefully enough tQ get additional inquiry·into them to occur. Using this report as an example, it finds wood waste supplies in northern Michigan to be more thaµ adequate to provide the region~s present electrical demand. But it doesn't examine necessary' actions to ensure continued future availability: maintaining soil fertility and organics, prevention of overcutting, forest zoning, replanting and mana__gement for sustained yield. It doesn't question if there are more desirable uses, such as furniture making, specialty wood products and firewood, for considerable amounts of "waste wood." It does not compare the use . of wood for electrical generation with other less expei:isive uses of wood for energy-dir~ct wood heat or co-generation of steam for industrial or space heat with steam for electrical , generation, or explore how much demand for the more expensive electrical energy could be reduced by use of such alternatives. It suggests that' energy plantations might increase energy prbductivity of the forests, without examining whether the combined value from timber and waste-wood energy in multiple-use forestry is preferable. Although wood-electric appeared competitive in small decentralized plants, neither simple means of improving boiler efficiency (preheating the •wood chips ' with exhaust·gases 110 redu'ce moisture content) nor the costs' of distribution, reserves requirements and systems reliability were included beyond a mention that they weren't examined. A good study in itself, with good references, that shows the considerable experience and proven reliability of wood/ electric systems that now exist, and within its scope a good discussion of their competitive economics. But unless the questions are knowingly being addressed in ·related studies, the responsibility remains it:1 studies such as this to at least clearly indicate what issues have not been addressed and require further study. There is a danger with studies suc_h as this that do not begin to think more compreqensively. They can lead us to use the right energy sour~es to continue to do the wrong things rather tha.n shift to patterns appropriate to such new conditions. -TB Russian Type Masonry Fireplace-Stove Plans, $5 from: Timeless Products, Inc. Box 143-J7 Roxbury, CT 06783 Plans for building your own Russian type masonry fireplacestove with unique features: 36 hrs. per load, 100,000 BTU per hr., cooking and hot water, separate fireplace, ten form variations. (Info from Country journal, July '78) -M~rjorie Posner, Alsea, Orngon • There have been many efforts to improve fireplace efficie~cy over the decades. They range from the "Rumford" design in masonry fireplaces to prefabricated steel air circulating µnits and a wide variety of heat exchangers which sit in the existing fireplace cavity. At best, the efficiency achieved by these techniques barely approaches 50 percent of the efficiency of the average free-standing woodstove. At this time, one of my greatest concerns is the lack of durability ;ind safety in fireplace heat exchangers. These units are usu~lly constructed of steel tubing (round or square). The rate of deterioration of the tubing (often doubling as the wood grate) is often quite rapid. Failure of a blower fan motor, or a temporary interruption of electrical service, can greatly accelerate deterioration of the air-cooled steel tube. The eventual result of the steel tube failure is a spray of hot ashes and embers onto the home carpet. I ~ecommend avoiding heat exchange contraptions constructed in this manner. Another method of utilizing fireplace chimneys is the installation of a fireplace-stove insert in the fireplace opening. ·One disadvantage ·of this idea is that chimney cleaning is made very difficult or nearly impossible. The entire unit may need to'be completely removed for chimney sweeping. Some products are advertised as being "permanent installations" and are .securely fastened in_plac;e. Chimney cleaning is a regular, needed maintenance chore which should not ,be hindered or discouraged. I also have yet to find a fireplace-stove insert incorporating the necessary features required for efficient wood combustion. Glass windows usually le~k air, steel doors and door frames warp (leaking more air), etc. If possible, I'd avoid these ill-conceived contraptions. Vertical view of fireplace cover installation The best utifization of masonry fireplaces is-the use of the chimney as an exhaust vehic.Je. If the chimney is located on an exterior wall, it's reasonable to assume that the creosote accumulation will be greater thari if it were enclosed inside the • building. A free-standing, efficient wood-burning stove can be installed in such a manner that ·the fireplace heat loss is diminished and the efficient wood burner provides a large share of the heat required to make your home comfortable. Whatever the method of installation, one basic require·ment must be met. No air should be allowed to enter the chimney without passing through the stove. Using the taller kinds of vertical exhausting stoves, it is necessary to put a new flue opening above the fireplace opening. Some local codes may require this form of installation. if the stove exhausts horizontally at a level not ex~eeding the height of the fireplace opening, it is usually possible to exhaust through the fireplace cavity into the chimney. • A major advantage of exhausting the stove through the fireplace opening is that no cosmetic dama~e is done to the face of the fireplace. This type~of fireplace closure is easily removed for chimney cleaning.
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