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Farm Energy Bills Gotcha? What to do - Part Two
This article was first printed in the Jan/Feb 2007 issue of the Organic Broadcaster, published by the Midwest Organic and Sustainable Education Service.
Linear Fluorescent lamps have also been improved. The T-12, the fluorescent lamp most folks are familiar with, is 1-1/2” in diameter and comes in a variety of lengths. The new cousin to the T-12 is called a T-8 which is 1” in diameter. It provides about 20% more lumens (measure of light output) per watt than a T-12 and will last on average 65% longer. One of the annoyances of the standard T-12 lamp is that they will flick at temperatures of less than 50°F. The T-8 lamp uses an electronic ballast that eliminates the flicker and allows the standard T-8 to operate down to 0°F. The socket end for the T-12 and T-8 are identical so a fixture that currently uses T-12 lamps can be converted to a T-8 simply by changing the ballast and the lamps.
Mercury vapor lamps have traditionally been used for the lighting of large spaces such as freestall barns or barnyards. High-pressure sodium is another option which has the best energy efficiency, but the light quality from these makes it difficult to differentiate between some colors. A newer choice is a pulse-start metal-halide lamp. Metal-halide lamps are twice as efficient as mercury vapor lamps and have excellent lighting qualities, making them the lamp of choice for freestall barns. The following table provides a comparison between the popular lamp types used in agricultural applications.
COMPARISON OF LAMP TYPES
Disposal of lamps is vitally important to reduce the amount of mercury in the environment. All of the lamps above contain mercury except for incandescent bulbs. Laws in most states require that lamps containing mercury be recycled to reduce the amount of mercury in the environment. Contact your local recycling coordinator for more information.
Almost every farm has at least one yard light that lights a central location on the farm. Typically, 175 watt mercury vapor lamps have been used that will cost about $92 per year to operate. If one of these mercury lamps was replaced with 100-watt high pressure sodium (HPS) lamp, it would save $35 per year per lamp in electric costs. If the refractor on the yard light was replaced with a full cut-off reflector, the HPS lamp could be reduced to 70 watts and provide about the same amount of light on the ground as the 175 watt mercury vapor lamp, due to more light being reflected to the ground rather than lost to the sky. The 70 watt HPS lamp would save about $53 per year in electric costs.
Areas to be space heated should be insulated whenever possible and holes and crack in the enclosure plugged to reduce infiltration losses. Effective heating systems are important to match the heater type to the environment being heated. In a warehouse or a loading dock area where the whole area doesn’t require heat, an overhead radiant heater will be most effective. These systems radiate heat to heat the objects in a space but doesn’t heat the air directly. This makes it comfortable for the inhabitance without heating the entire space. If the entire space requires heating, radiant floor heating will have the lowest energy costs. High efficiency condensing type heaters are recommended. These are heaters that have thermal efficiencies of 90% or higher for gas-fired units and 80% or higher for oil fired units. If a unit heater is being used, purchase ones with power-vented exhausted because they are 13% more efficient than a gravity vented unit.
There are no grain dryer performance standards, and limited research data to make comparisons for energy efficiency of grain dryers. Typical energy consumption values for drying corn as reported by the University of Minnesota are 0.02 gallons for propane and 0.01 kWh of electricity per bushel of corn per percentage point of moisture removed. One would like to only spend money drying what can be sold, so it is highly recommended that corn be cleaned before drying and before storage to remove fines.
There are a number of different types of dryers, each of which have different methods to improve the energy efficiency of drying. It is important to understand the parameters that affect energy efficiency. Drying efficiency will increase with increasing temperature and increase with decreasing air flow per bushel, but at the expense of higher moisture variation in high temperature dryers. Cross-flow dryers are the most popular and are available in either continuous flow or batch type. The air flows through grain column perpendicular to the grain flow. The efficiency of these dryers can be increased by recovering heat from the corn as it cools to preheat the drying air. On an older dryer, ductwork over the cooling section to capture the air and route it to the dryer air intake can reduce drying cost 10 to 20%. Many newer dryers have built-in heat recovery by placing the dryer fan inside the dryer between the cooling section and the heated section. A portion of the air must flow through the cooling section to reach the fan. This is sometimes called reverse flow cooling, or suction cooling.
Bin dryers can benefit from the use of a stirring device to mix the dryer corn on the floor of the bin with the higher moisture corn above. It is recommended that the stirring device be run continuously during drying in a high-temperature bin dryer. A 25% savings in fuel costs is typical. The stirring device should only be run 2 or 3 times per season in an ambient or low temperature bin dryer. Stirring should be done once after the bin is filled, once after the corn reaches 18-20% moisture and a final time after drying is completed. This will reduce drying costs by about 20%. Over stirring can result in a build up of fines on the floor and lead to restricted air flow.
There are two types of high temperature continuous flow dryers that are considered high efficiency; mixed flow dryers and continuous in-bin dryers. The continuous in-bin dryer is an automated bin dryer that uses a sweep to remove grain at the bottom of the bin as it dries. The hot grain is moved to a storage bin and cooled. These dryers have the advantage of being able to use the dryer for storing the last batch of the year. The mixed flow dryer is a column type of dryer that has an air flow patterns through the grain in con-current-flow and counter-flow hence getting the mixed-flow name. University research studies indicate that this type dryer is the most energy efficient of the column dryers and consistently provides high quality, high test weight grain. The chart below provides an estimate of the efficiency differences between different types of dryers.
Two other ways of increasing energy efficiency is to use in-bin cooling or dryeration. In-bin cooling requires grain to be transported to the storage bin hot, about 1 to 1.5% moisture above the desired storage moisture, and cooled with ambient air immediately. This reduces energy usage by about 15% and increases dryer capacity about 30%. Dryeration is similar to in-bin cooling except the grain is allowed to steep for 4 to 12 hours before being cooled. The grain exits the dryer at 2 to 3% moisture above the final storage moisture. The grain must be moved from the steeping bin to avoid spoilage due to the condensation that will occur on the bin walls. Dryeration can save about 25% in energy costs.
Energy Efficiency Grants
You can find more in depth information on the topics discussed above at the Wisconsin Energy Efficiency and Renewable Energy Resource web site under Agricultural operations – www.uwex.edu/energy.
Very few people think about the energy efficiency of water heaters, but these units can be very inefficient, especially gas and oil fired units. Electric units are considered 99% efficient at transferring heat, while most standard gas or oil fired units have an 80% thermal efficiency. But that is only half the story. Water heaters can have very high standby losses: heat lost through the tank walls to the surroundings. This can range from about 0.5% per hour for highly insulated water heaters to greater than 3% per hour. The average water heater has about 2 to 2.5% heat loss per hour, which equates to 50 to 60% standby loss per day. This reduces the overall efficiency of the average water heater to 50 to 55%. High efficiency condensing-type water heaters are available that have thermal efficiencies of 94% and standby losses of 1% or less per hour, increasing the overall energy efficiency to about 75%. Electric water heaters are generally low standby losses because they are well insulated, but can cost more to operate depending on your electrical rate. The heating rate of electric water heaters is generally less (gallons heated per hour) than gas or oil fired water heaters, so in some cases they can’t keep up with the demand.Return to TOP