Smc Newsletter April 06


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Smc Newsletter April 06

  1. 1. Next discussion group: “50 Ways to Cut Energy Usage in Your Home” will be held at the Central Avenue Bakery, 174 Central Avenue, PG, on Thursday, April 6, from 7:00 to 9:00 PM. The meeting is free and the public is invited. How Do I Lose Energy-- Let Me Count the Waste The average American home turns high quality energy into useless low-grade heat. How? By using crude devices designed for energy that was once nearly free—but now that it’s getting scarce and expensive, it’s time for a change. What do we do that wastes energy? Lighting Most lighting is still done with incandescent bulbs—a fine tungsten filament is heated by electric current in a vacuum—so hot that it glows. The problem is, if you get tungsten hot enough so most of the radiation it emits is visible, it melts or evaporates. So the vast majority of the output of an incandescent light bulb is invisible infrared radiation that heats the bulb envelope and surrounding surfaces. If you have the light on when you’re heating your home, and you have electric heat, it doesn’t matter much. But in any other situation, you’re throwing away almost all the power that goes into that light bulb. What’s better? A halogen light can burn a little hotter than a standard bulb, because it uses a gas like iodine to react with tungsten that sublimates from the filament and return it, rather than letting it condense on the glass surface. A compact fluorescent bulb uses about a quarter as much power to produce the same light as an incandescent bulb, and an LED-based lamp uses on the order of a tenth as much. However, LED lamps are still quite expensive to buy, though the dealers say they are more economical in the long run. By the way—any light that uses a flame as a light source is probably even less efficient than an old-fashioned bulb. Heating Heating is required when the temperature indoors is unacceptably cool for the occupants or the contents of a home. Once the desired temperature is reached, the only heat required is the amount that is lost to the environment through the floor, walls, windows doors and roof. If they don’t let any out, you don’t have to put any in. The key to keeping a home at a comfortable temperature is insulation. And remember, you can buy insulation cheaply now, but you will have to purchase energy dearly later. There are several ways to heat a home, and each warrants a little discussion: • Fireplaces range from the old, crude open box with a chimney, to sophisticated glass -fronted units with heat exchangers, blowers and thermostats. The simple open fireplace typically burns wood or gas, drawing air from the room to feed the flame, heating it to a Newsletter Editor: Mark Folsom 831 648 1543
  2. 2. very high temperature and sending it up the chimney. Almost all of the heat that gets into the room is in the form of radiation, which is a pretty small fraction, while the bulk is lost in the hot flue gas. Even more pernicious is the way the air consumed is replaced—it comes into your home from the cold outdoors, under and around doors and leaky windows—and may cool your home more than the fire heats it. Of course, the most sophisticated fireplaces can be as efficient as a modern furnace. • Wood stoves can also be relatively efficient or very wasteful. The most wasteful are those that burn the wood rapidly and hot, with a lot of hot gas going up the chimney. More efficient units burn the wood more slowly and extract a greater fraction of heat from the flue gas. However, cooler smoke can condense more readily on the chimney walls, sometimes leading to increased danger of chimney fires. • Electric resistance heaters, such as the electric baseboard type, are very efficient with respect to converting electric power into heat—but there’s a huge heat loss at the power plant: about two-thirds of the heat energy of the fuel used to generate the electricity is discarded as waste heat. That isn’t because the power generators are perverse, it’s a consequence of the laws of thermodynamics—heat engines can never turn all of the heat in a fuel into power. However, if the power plant can find a local use for its waste heat, it isn’t wasted, and could be used as process heat for some industrial process, or as space heat for homes or businesses. This is called cogeneration. • Heat pumps can make the overall picture even better. The special thing about electricity is that it’s 100% available (meaning that all of it can be used to do work, unlike heat), and can thus be used to operate a motor at nearly perfect efficiency. And the really neat thing about a motor is that it can be used to take heat from the environment and pump it up to a higher temperature—so all the electric power goes into heating your space, and some heat from the cooler environment is added in as well. It reverses the principle of a heat engine and instead of dumping low-grade heat into the environment, it takes low- grade heat from the environment and upgrades it a little bit to heat your home. How much it can get from the environment for each unit of electric energy depends on the temperature of the environmental heat source and the temperature of your home—the smaller the difference, the better it gets. That means that, if you can take heat from a source underground, instead of the cold winter air, you get an extra bonus of efficiency— and savings. • Furnaces can range from around seventy percent into the nineties. If yours is old and decrepit, it will cost you dearly as fuel prices rise—as they surely will. The problem with a conventional furnace is that it converts high-quality energy (high temperature flame) directly to low-grade heat, without exploiting all the power that a really hot flame makes available. When concentrated energy is converted to diffuse energy, the process is irreversible—its availability is lost forever. I’m not aware of any small-scale cogeneration plants that are available commercially, but they would be good to have— you could heat your home with 2/3 of the energy and use or sell the rest as electricity. • Solar heat is available on sunny days at about 1000 watts per square meter. If you can store some of it in a big thermal mass when it’s available, it can help keep you warm at other times. • Hot water heaters in the US have traditionally had a big tank full of water that’s kept hot all the time. They continually leak heat into their surroundings—heat that has to be replaced with a flame or an electrical resistance heater. Fortunately, on-demand heaters Newsletter Editor: Mark Folsom 831 648 1543
  3. 3. and solar water heaters are available now as alternatives. Leaving hot water running longer than necessary can waste a surprising amount of energy. • Dehumidifiers extract moisture from the air and collect it as liquid water. In the process of condensing, the water gives up a lot of heat, which is put into the dried air, which is thus warmed a bit, as well. Cooling Almost all space cooling is done by refrigeration—a heat pump is used to extract heat from one’s living space and dump it somewhere in the environment, along with the work it takes to do the pumping. The bigger the difference in temperature between your living space and the sink where the heat is dumped, the more power it takes per unit of heat removed. Humidity contributes a great deal to the air-conditioning load, because the water vapor gives up a huge amount of heat upon condensing to liquid. Again, if you have a nice cool cave or a big cool underground mass where you can dump your heat, you can get rid of it more efficiently than trying to get the hot summer air to accept it. Heat always tends to flow naturally from warmer places to cooler ones, and always requires work to make it go the other way. Cooking There are many ways to heat food, and most also involve heating the surrounding air. Each has its characteristic ways of wasting energy, and many can be used more efficiently with a little thought. • Ranges--A gas flame that curls up around the bottom of a pot or pan will mostly heat the air nearby—as will an electric burner that’s too big. If the space heater is in use anyway, it might not make a lot of difference, but if the air-conditioner is running, the extra heat will just load it up further. And—if you turn on an exhaust fan to draw air out of the kitchen, an equal amount of air will be drawn in from outdoors to make up for it. If the outdoor air is cool, you may have to heat it and if it’s hot or humid, you may need to cool it. • Ovens usually vent into the kitchen and lose heat through their walls as well. • Microwaves are usually quite efficient, but often don’t produce very appealing results, especially when cooking meat dishes. • Crockpots and slow-cookers are often better at holding in heat than regular pots and pans, but very long cook times can aggravate heat loss. • Outdoor cooking may or may not waste heat directly, but it has the advantage that it doesn’t burden indoor climate control and ventilation. Refrigeration Keeping food cold or frozen is a great way to keep food and beverages fresh, but it comes at a high cost in energy, more so in a warmer home. Each time a refrigerator door is opened, cool dry air is lost and warmer, more humid air replaces it. That new air has to be cooled to the temperature setting of the refrigerator and the moisture condensed out of it—often in the form of frost in the freezer, which then is melted and drained away. Big refrigerators generally use more energy than small ones, and old ones use more than new. Uprights use more than chests. Holding the door open while staring in uses the most of all. Newsletter Editor: Mark Folsom 831 648 1543
  4. 4. Entertainment Televisions, VCRs, DVRs, DVDs, computers, stereos, game consoles and the like all draw power, often even when they are dormant or turned off.. Though their contribution to energy use is not usually as great as heating, air-conditioning or refrigeration, they can add up if not managed well. Resources for further information: • C. Crane & Company—for LED lighting • Energy Star—for high efficiency appliances Newsletter Editor: Mark Folsom 831 648 1543