Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and LP gas have affected many livestock producers, especially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever-increasing price for fuel and electricity, have encouraged many producers to begin looking for alternative energy sources

Fehr, Robert L.

English

Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and LP gas have affected many livestock producers, especially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever*increasing price for fuel and electricity, have encouraged many producers to begin looking for ways to reduce energy consumption

University of Kentucky

University of KentuckyUKnowledgeAgricultural Engineering Energy Series Biosystems and Agricultural Engineering9-1978Energy in Agriculture: Energy for Swine FacilitiesPart I: Energy ConservationRobert L. FehrUniversity of Kentucky, robert.fehr@uky.eduRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/aees_reportsPart of the Bioresource and Agricultural Engineering CommonsThis Report is brought to you for free and open access by the Biosystems and Agricultural Engineering at UKnowledge. It has been accepted forinclusion in Agricultural Engineering Energy Series by an authorized administrator of UKnowledge. For more information, please contactUKnowledge@lsv.uky.edu.Repository CitationFehr, Robert L., "Energy in Agriculture: Energy for Swine Facilities Part I: Energy Conservation" (1978). Agricultural EngineeringEnergy Series. 34.https://uknowledge.uky.edu/aees_reports/34AEES-1 ENERGY FOR SWINE FACILITIES PART 1: ENERGY CONSERVATION Robert L. Fehr Assistant Extension Professor in Agricultnral Engineering INTRODUCTION Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and lP gas have affected many livestock producers, espe-cially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever*increasing price for fuel and electricity, have encouraged many producers to begin looking for ways to reduce energy consumption. Fan energy and heat added to maintain the tempera-ture in farrowing houses and nurseries, called "supple-mental heat," are the two major energy costs in confine-ment swine facilities, excluding feed energy. Supplemental heat may talre several forms, some of which may not be recognized as supplemental heat sources. One source is the creep heat used for small pigs. In a well-insulated building creep heat can provide a large amount of the heat required to maintain the temperature in a building. However, the creep heat added in the summer time requires higher ventilation rates to control temperatures, thereby increasing UNIVERSITY of KENTUCKY COLLEGE of AGRICULTURE DEPT. of AGRIC. ENGINEERING COOPERATIVE EXTENSION SERVICE fan energy costs. Other uses of energy in swine housing include the lighting and feed handling. When:. considering energy conservation one must under-stand that present systems now utilize large amounts of energy because by utilizing more energy it is possible to eliminate or reduce the management input into. the system. As shown in Figure I, high energy /low management systems can be replaced with a low energy system, but, in High Ene.gy Use ~ Low Low High Management Figure 1.-The relationship between the level of energy use and management of swine facilities. in cooperation with KENTUCKY DEPARTMENT of ENERGY general, this will increase the level of management required by the individual producer. Therefore, in reviewing differ· ent methods to reduce energy consumption, remember that they may increase the level of management required for the system. ENERGY REDUCTION METHODS Insulation One of the most common ways of saving energy is adding insulation. Because farrowing houses and nurseries are held at high temperatures, 70°F and above, proper insu-lation is required for these structures, especially if these facilities are used the year around (Table 1). Table 1.-The Effect of Insulation Level on the Supple-mental Heat Cost in a Farrowing Facility. Assumptions: 18-Stall Farrowing Facility 30 cfm/stall 80°F Inside 30°F Outside Il'G 50¢/gal Uninsulated (R=2) Some Insulation (R=8) High Insulation (R=l8) Heat Cost for January $515.00 $150.00 $100.00 In general, the insulation requirements for swine ·housing are less than those for a residence because swine housing has a good heat source within it-the animals them-selves. This is especially true in a nursery or grower facility where there is a high density of animals. Because the animals provide some heat the supplemental heat require-ments are lowered, reducing the savings received by adding insulation. It is advisable under winter conditions to always keep a facility as full as possible because the animals are providing a heat source. Improper use of insulation in swine facilities ·may create problems. There have been instances where. insula-tion in livestock buildings has become wet, reducing its effectiveness. In most of these cases the problem has occurred because water vapor in the air inside the building has gotten into the insulation and condensed. Typically, in a residence in the winter, relative humidity levels are 30-40% or lesS; however, in some livestock facilities relative humidity levels are 70-80% or higher. This causes moisture problems to be more prevalent in livestock facilities than in 2 residences. To prevent these problems a high-quality vapor barrier must be used. It should be installed as close to the warm side of the wall as possible. Vapor barriers include aluminwn foil, plastic, and some insulation boards. However, it should be noted there is a distinction. between the two types of "styrofoam" board, the solid board and bead board: bead board is not a vapor barrier. Some problems have occurred in livestock facilities where bead board was used as insulation material and left uncovered with no vapor barrier provided. The water vapo_r in the building condensed in the bead board and saturated it, and the added water weight caused it to fall from the ceiling. It is possible to assess the savings that can occur from adding insulation. For example, au uninsulated 18-stall farrowing building operating at 80°F with a ventilation rate of 30 cfm (cubic feet per minute) per sow will have a supplemental heat cost of $515 (Table 1). This is for the month of January, with an average outside temperature of 30°F. Table I also shows that the savings for using some insulation at levels similar to those given in Table 2, in the same facility, can save $365 in supplemental heat cost. However, if the level of insulation is increased to what might be considered a high insulation level, the additional saving in supplemental heat cost is only $50 more than the moderate insulation level. Remember, these savings are for an average January and would be greater if the entire winter were evaluated. For many buildings the January supple· mental heat cost is about one-half of the total yearly heat cost. Table 2.-Currently Recommended Insulation Levels for Swine Facilities. R value of the Walls · - · · · - · · · · · · = 9 R value of the Ceiling · · · · · · · · · · · = 12 Table 1 also shows the concept of marginal returns with the addition of insulation to both livestock housing and to the home in general. As the total amount of insulation increases, the savings from the last layer of added insulation rapidly decrease. Therefore, in an uninsulated building relatively large energy savings would be realized by installing some insulation. In a building which is already insulated to some degree, increasing the insulation level should be evaluated more closely. Fan Maintenance, Selection Fan maintenance and selection is another way to reduce the energy requirements of swine facilities. Fan maintenance is a problem in swine facilities because of the dust which accumulates, coating the fan blades and shutters. Research has never established figures that show any savings from cleaning fan blades themselves, although if the conditions are severe a problem Wth the motor could develop. However, if the shutters are not clean and cannot operate freely they can reduce fan performance by 20% (4). That is, during ~ year there will be a 20% increase in operating costs for a fan if its shutters are dirty and cannot open completely. When shutters are installed on a fan they decrease efficiency somewhat. Some research indicates that if a fan operates continuously year-round, no shutter should be used. In a facility like a farrowing house, which has a fan that runs continuously when there are animals in the building, some type of shutter or door will be needed to close the facility when no livestock are present. However, when the fan is operating the shutter or door should be held in an open position. In past years, fan selection did not receive careful attention. Studies have shown that there are large differ· ences in fan efficiencies(!), but the relatively inexpensive cost of fan operation also kept interest low. However, now with electrical costs increasing, producers are becoming more concerned about the efficiencies of fans. This has resulted in a proposed new rating system for fans, which would rate fans for the cfm (cubic feet per minute) of air moved per watt of power used. In this system a fan having a high cfm/watt rating would move more air at a lower elec-trical cost than a fan having a low cfm/watt rating. Typi-cally, these numbers range anywhere from 10 to 20, which indicates that some fans are twice as efficient as others. The importance of these ratings can be seen by looking at the savings for a 2,000 cfm fan that runs continuously year-round, using electricity costing 3¢/kwh. As shown in Table 3, the low-quality fan, with a 12-cfm/watt rating, cost about $45 a year while a high-quality fan with a Table 3.-Savings which can Result from Proper Fan Selection. Assumption: 2,000 cfm Fan, operating continuously Cost of Operation Low-Qnallty Fan-12-cfm/watt - - - - - -- - - $45 .00/year High-Quality Fan-19-cfm/watt --------- 20.00/year Savings~ --------- $25.00/year 3 19-cfmjwatt rating cost ouly $20 a year to operate. There-fore, proper fan selection represents a simple way to save $25 a year. It also demonstrates that a higher priced fan with a good performance characteristic in terms of cfm/watt may be a wise investment. Ventilation Rate Given the large portion of energy use in swine facilities resulting from the ventilation of the building, it is impor-tant to consider the effects of ventilation rate on energy consumption within a facility. Ventilation is required for four major reasons: to maintain temperature, control mois-ture, control odors and provide oxygen. While providing oxygen is the primary reason for ventilation, most ventila-tion systems are operated to maintain the air tempera~ure in a facility. A minimum amount of ventilation must be provided to control moisture in livestock facilities. This method provides sufficient oxygen and will also control odors. When the ventilation control system is operated only to maintain the temperature in the facility, the humidity level can become high in the winter time. This requires that a minimum ventilation rate be used to control the humidity within the building. At these minimum rates a certain amount of supplemental heat is required to maintain the temperature within the facility when outside air tempera-tures are low. Table 4 shows the effects of ventilation rate on the total cost of operating an IS-stall farrowing house, during average January conditions. Beginning with a ventilation rate of 50-cfm/stall for the building, the total cost of opera-tion is over $300. By reducing the ventilation rate to 30-cfm/stall the total cost is reduced to $200. If the ventila-tion rate is reduced to the minimum, which would be acceptable for moisture control, the total cost would be about $100. Clearly, substantial savings will result from reducing the ventilation rate. Table 4.-The Effect of Ventilation Rate on the Total Energy Cost, Excluding Feed, of a Farrowing Facility. Assumptions: 18 Stalls 80°F Inside LPG 50¢/gal 900 cfm {50-cfm/stall) 540 cfm (30-cfm/stall) 275 cfm (moisture control) Some Insulation 30°F Outside Electricity 3¢/kwh Total Cost for January $335.00 200.00 95.00 Why are recommended rates so high? As the ventilation rate is reduced an increased level of management is required. Relatively high ventilation rates are recommended because they will provide a proper environment with little management. They allow for some error in fan ratings, and require a low level of management. Also, small fans can be difficuit to obtain. However, it is completely acceptable to reduce high ventilation rates as long as the humidity level and odors are maintained at acceptable levels. But, if lower ventilation rates are used, the manager must continually observe the conditions in the facility and be able to adjust the ventilation rate if problems occur. Thermostat Setting The thermostat setting in a facility also greatly affects energy use. The general guideline for buildings is that the lower the temperature within the building that can be tolerated, the lower the fuel cost will be. However, there are hidden costs here, because when the temperature within a facility is reduced, additional energy in the form of feed will be required. This is especially true with nursery auimals. The effect of the temperature setting can be shown with the farrowing house example. Two different manage. ment strategies are considered-one, using normal farrowing facility operating procedure of not adjusting ventilation rates, and another that reduces the ventilation rate to control moisture. Table 5 shows the effect of thermostat setting for both management strategies for an average January. An increase in the total operating cost, especially in an uuinsulated facility, can be seen for all three levels of insulation by raising the thermostat from 70°F to 80°F. However, in a well-insulated facility with the ventilation rate adjusted to provide moisture control, the effect on the total energy use of increasing the thermostat setting depends on the level of insulation. In the facility with no insulation the cost rises from $340 to $390, a $50 increase, but in facilities with some insulation almost no change occurs in operating cost. In a highly-insulated facility there is some reduction in operating cost by increasing the thermostat setting. The reason the total operating cost for a well-insuiated facility decreases as the thermostat setting increases is not obvious. The ability of the air to hold moisture at various conditions is shown in Table 6. It can be seen that when outside ail; at 30°F and 50% relative humidity enters a 4 Table 5.-The Effect of Temperature Setting on the Total Energy Saving, Excluding Feed Energy, of a Farrowing Facility. Assumptions: 18 stalls LPG 50¢/gal 30°F Outside Electricity 3¢/kwh Ventilation Rate= 30 cfm/stall Total Cost for January Temperature Setting = 70°F 80°F Uninsulated (R=2) Some Insulation (R=8) High Insulation (R=l8) Ventilate for Moisture Control tbinsulated Some Insulation High Insulation Ventilation Rate for moisture control 70°F · 400 cfm 80°F- 275 cfm $380 150 110 340 100 60 $560 200 150 390 95 45 facility and is warmed to 80°F, the huruidity drops to 10%. This warmed outside air has a large moisture-holding capability. When the relative humidity in the inside air is increased to 70%, there is a large difference in the moisture between 80°F air and 70°F air. Table 6 shows that air at 80°F and 70% relative humidity has equivalent moisture to air at 70°F and 100% relative humidity. So, for a building at 80°F the relative humidity would be acceptable, al-though !lightly high, but if it was 70°F there would be a moisture problem within the facility, and the minimum ventilation rate would need to be increased to maintain acceptable conditions. Thus, in a well-insulated building, the increase in heat loss caused by increasing the thermostat setting is less than the reduction in heat loss through the ventilation system if the ventilation rate is reduced to the minimUm required to control moisture for that tempera~ ture. Therefore, a small net energy savings is realized. Table 6.-The Air's Moisture Holding Ability at Different Temperatures. 30°F 50%RH = 80°F 10% RH 70°F 70%RH = 80°F 50% RH 80°F 70%RH = 70°F 100% RH The College of Agriculture is an Equal Opportunity Organization with respect to education and employment and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, national origin, sex, religion, age and handicap. Inquiries regarding compliance with Title VI and Tille VII oft he Civil Rights Act of 1964, Title IX of the Educational Amendments, Section 504 of the Rehabilitation Act and other related matters should be directed to Equal Opportunity Office, College of Agriculture, University of Kentucky, Room S-1.05, Agricultural Science Building-North, Lexington, Kentucky 40546 ISsued in furtherance of Cooperative Extension work. Acts of May 8 and June 30. 1914, in cooperation with the U.S. Department of Agriculture. Charles E. Barnhart, Director of Cooperative Extension Service, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort Issued 9-78, 3M; 1.5M-11-81 

Energy in Agriculture: Energy for Swine Facilities Part I: Energy Conservation

University of KentuckyUKnowledgeAgricultural Engineering Energy Series Biosystems and Agricultural Engineering9-1978Energy in Agriculture: Energy for Swine FacilitiesPart II: Alternative Sources of EnergyRobert L. FehrUniversity of Kentucky, robert.fehr@uky.eduRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/aees_reportsPart of the Bioresource and Agricultural Engineering CommonsThis Report is brought to you for free and open access by the Biosystems and Agricultural Engineering at UKnowledge. It has been accepted forinclusion in Agricultural Engineering Energy Series by an authorized administrator of UKnowledge. For more information, please contactUKnowledge@lsv.uky.edu.Repository CitationFehr, Robert L., "Energy in Agriculture: Energy for Swine Facilities Part II: Alternative Sources of Energy" (1978). AgriculturalEngineering Energy Series. 35.https://uknowledge.uky.edu/aees_reports/35AEES-2 ENERGY FOR SWINE FACILITIES PART II: ALTERNATIVE SOURCES OF ENERGY Robert L. Fehr Assistant Extension Professor in Agricultural Engineering UNIVERSITY of KENTUCKY COLLEGE of AGRICULTURE DEPT. of AGRIC. ENGINEERING COOPERATIVE EXTENSION SERVICE in cooperation with KENTUCKY DEPARTMENT of ENERGY ENERGY FOR SWINE FACILITIES PART II: ALTERNATIVE SOURCES OF ENERGY Robert L Fehr Assistant Extension Professor in Agricultural Engineering INTRODUCTION Recently, there has been some concern about energy utilization in agricultural production. Shortages of natural and LP gas have affected many livestock producers, espe-cially swine producers utilizing LP gas as a supplemental heat source in farrowing facilities. These shortages, coupled with an ever-increasing price for fuel and electricity, have encouraged many producers to begin looking for alternative energy sources. Fan energy and heat added to maintain the tempera-ture in farrowing houses and nurseries, called "supple-mental heat," are the two major energy costs in confine-ment swine facilities, excluding feed energy. Supplemental heat may take several forms, some of which may not be recognized as supplemental heat sources. One source is the creep heat used for small pigs. In a well-insulated building creep heat can provide a large amount of the heat required to maintain the temperature in a building. However, the creep heat added in the summer thne requires higher ventilation rates to control temperatures, thereby increasing fan energy costs. Other uses of energy in swine housing include the lighting and feed handling. When considering alternative energy sources one must understand that present systems now utilize common forms of energy, such as electricity and LPG, because by utilizing these forms of energy it is possible to eliminate or reduce the management input into the system. As shown in Figure 1, electrtcal aud LPG high energy flow management systems High Ene.gy u,e 1 Low Low -·-~~---------.:;.. High Management Figure 1.-The relationship between the level of energy use and management of swine facilities. can be replaced with a low electrical and LPG energy system, but, in general, this will increase the level of man-agement required by the individual producer. Therefore, in reviewing different alternative fuel sources, remember that they may increase the level of management required for the system. ALTERNATIVE ENERGY SOURCES Solar Energy One of the basic considerations in selecting an alterna-tive energy source is economics and ease of use. Because the sun is free and provides a readily available and inexhaustible source of energy, it seems to be a very attractive alternative energy source for swine facilities. Present ventilation systems use solar energy, but in the form of air tempera-ture. Some swine facilities already make use of some solar collection by allowing ventilation air in the winter to enter through the attic of the building. This can result in a temperature 2° to 20°F higher than the outside air. Modifications can be made in an attic to increase its ability to collect solar energy-one method uses a black metal roof with the intake air drawn along underneath the metal to collect more solar energy. Another method uses clear fiberglass roofing and in some cases, painting the entire inside of the attic black. Both methods work and will increase solar energy collection. However, there may be a heat problem with such arrangements in the summer time, especially with the second method because the increased heat load in the attic increases the temperature inside the facility. Solar energy collection systems have been utilized in swine facilities since the 1940's, in the form of single slope roofs with large windows on the south side. However, cheap fossil energy made their construction uneconomical. A complication connected with some of the early solar designs was that in the winter they occasionally caused sows to go into heat stress because of the bright sun shining on them. Newer solar collection systems have been developed which utilize a sidewall collection system but keep the sun from directly hitting the sows, such as the one shown in Figure 2 {3). This system utilizes an 8" block wall with no mortar and the outside edge of the block painted black. A plastic cover is installed over the block and the inlet is placed at the top to draw the air from the attic. The block wall is so constructed that all the air entering the facility passes through cracks between the blocks. The plastic cover allows solar energy to enter, striking the black painted surface, warming the air and warming the blocks at the same time. The advantage of this system is that at night the blocks which have been warmed by the sun give up their heat to the entering ventilation air. Therefore, it provides both a solar collection system and a method of some heat storage, which are important considerations. This system may also be useful in the summer cooling of the building. This is accomplished by drawing ventilation air through the blocks at night, thereby cooling them with the lower nighttime air temperatures. Then, in the daytime, incoming air is cooled by drawing it through the blocks. The overhang of the building must be properly designed so that in the summer time the entire south side of the building is shaded. The system is presentiy being evaluated and more information will be available in the future. Another solar collection system using sidewalls does not provide a direct method of storage. Instead, it utilizes AIR BLACK PAINT PLASTIC COVER 8" BLOCK WALL, NO MORTAR Figure 2.-A block wall solar collector and storage system. black plastic behind the clear plastic cover with an air space between them, and an air space between the black plastic and the wall. Air is drawn through the air spaces to collect the solar energy. However, without a method of storage, a solar collection system may provide more energy than necessary during clear days, and provide no heat energy at night. There are some commercial solar collectors available; however, commercial units tend to be relatively expensive, because they are designed for higher temperatures. Since storage is an important consideration with any type of solar collection system there have been experiments with various methods of storing solar energy. In the rock 3 storage system method the heated air is drawn through a very large volume of buried rock during the day, and intake air is drawn through the rocks at night. The rock storage systems do not necessarily need a solar collector to func-tion. In Figure 3a it can be seen that as the outside air temperature varies, the air temperature, after it passes through the rock storage, experiences a temperature modifi-cation. The rocks cause this thermal lag and may reduce the high and low extremes of the outside air temperature. With proper operation and fan control (Figure 3b), it may be possible to utilize the rock bed, but only when the air temperature coming from the rock bed is greater than the outside temperature (which would increase the average temperature of the air entering the house). Storage systems may be useful for both summer and winter operation of swine facilities. Computer modeling research work is being conducted on these type of systems to determine their feasibility and design requirements for swine facilities. 40° OUTS!DE AIR AFTER ROCKS AIR TIME TEMPERATURE 20° (a) 40° 30° TIME 20° I b I Figure 3.-The effect of a rock storage system on the intake air temperature. Heat Pumps Another energy-saving device that has recently received attention is the heat pump. Generally used for homes, heat pumps can also be used for livestock ventilation systems. Basically, a heat pump is an air conditioner operating in reverse. In Kentucky, a heat pump will provide approxi· mately twice as much heat per kwh as regular resistance electric heat. Figure 4a shows the standard installation of a heat pump in a swine facility ventilation system, with the heat collection coil on the outside and the heating coil on to I HEATED -INTAKE AIR INTAKE AIR to I HEATED -INTAKE A" Figure 4.-Possible heat pump installations for swine facilities. the intake air, thus raising the intake-air temperature. Some research is being conducted on the feasibility of using warm exhaust air as the heat source instead of the cool outside air. Figure 4b shows the configuration of the heat pump operating in this manner. The advantage of this system is that the heat would be collected from warmer air rather than from relatively cooler outside air, thus improv-ing the heat pump efficiency. The basic problem of this arrangement is that the exhaust air contains relatively large quantities of moisture and dirt, thereby increasing mainte-nance and corrosion with this installation. Maintenance may be such a major problem that this installation may never become feasible. Alternative Fuels Yet another current idea is alternative fuels. Some research is being initiated at the University of Kentucky to examine alternative fuel sources for the farm. When con-sidering an alternative fuel, it is important to remember that any fuel must first be collected and processed, then stored and finally placed in the burner and the waste products removed. Currently, fuels such as natural gas, LP gas and oil need little management for collection, process-ing, storage, placement and waste product removal. However, using fuels like wood, coal, or crop residue requires increased levels of management. Present control systems for alternative fuel sources such as wood and crop residue are not well documented as to performance. Many of those are not completely automatic either, which further limits their application. Some commercial equipment is presently available; however, the equipment tends to be somewhat expensive and designed for operation with a fairly constant load. Because of the large daily temperature variations which exist in Kentucky, a supplemental heat system must start and stop and change speeds continuously through the day. This tends to be difficult with most alternative fuel systems. 4 Heat Exchangers One energy-saving idea that has been considered is the heat exchanger. Heat exchangers are designed to move heat from the exhaust air to the intake air, similar to a heat pump. One type of heat exchanger that has been tested is a parallel plate unit in which exhaust air is passed between thin metal plates and the intake air drawn in next to it (Figure 5). One problem associated with this system is that a large plate area is required to exchange the heat between the exhaust air and the intake air. These units are capable of reclaiming from 30 to 40% of the heat normally lost in the exhaust air (2). However, they also have problems like the heat pump in that they become coated with dirt and moisture and are very difficult to clean, causing potential corrosion problems. Although most of the research on this type of exchanger was done in the SO's, there is presently renewed interest in this idea. EXHAUST AIR INTAKE AIR EXHAUST AIR INTAKE AIR EXHAUST AIR Figure 5.-Air flow pattern in a plate-type heat exchanger. An alternative to the passing of air between plates is to use a heat sink which is similar to the rock storage concept, only it uses fewer rocks. Figure 6 shows a system in which two small beds of rock are utilized. One is warmed while the second is cooled, and then the fan direction is reversed. This causes the intake air to be wanned as it passes over the rock. One consideration with this system is fmding fans and controls that will allow the fans to reverse properly. The storage area size, however, can be limited to 30 to 40 cubic feet, or can be very large depending on how frequently the fans are reversed. The biggest advantage of rock heat sink units is that the materials required for construction are rela-tively inexpensive and durable. Because of their low cost, it may be feasible to replace the rocks every year if moisture and dirt buildup is a problem. Another problem associated with this system during the winter is that as the rocks are cooled by the incoming air the moist exhaust air may con-dense and freeze on the rock surface when the fan is reversed. However, this situation was reported in a northern climate where the cold-weather temperature extremes exceed -30°F. COOL COOL INTAKE EXHAUST AIR AIR ROCKS (I) ROCKS (2) I t WARM WARM INTAKE EXHAUST AIR AIR COOL COOL EXHAUST INTAKE Alt T ROCKS (I) ROCKS (21 t WARM WARM EXHAUST INTAKE AIR AIR Figure 6.-Air flow pattern in a heat sink heat exchanger. A new heat exchanger system currently under investiM galion is called a heat pipe. This device operates much like a heat pump but has no motor. A heat pipe is a long sealed tube which contains a fluid that evaporates and absorbs heat at exhaust air temperatures and then condenses, giving off heat to the intake air (Figure 7). The tube is then set at an angle so that the lowest end is the exhaust air. The liquid runs down to that end when it condenses and the gas created by evaporation circulates up to the top. This allows the system to move heat back and forth, with the fluid within the tube being the only moving part. Presently, these systems are somewhat expensive but interest is increasing in this type of unit because no moving parts are required. EXHAUST AIR LIQUID EVAPORATES INTAKE AIR GAS CONDENSES Figure 7.-A heat tube heat exchanger installation. 5 Methane Gas The feasibility of on-the-farm methane gas production is limited at this point. Methane is the major component of natural gas. Presently, the method of methane gas produc-tion being promoted is the use of an anaerobic digester. Anaerobic digestion means the biological breakdown of material without any free oxygen being present in the system. This is a naturally occurring process, and methane is produced in anaerobic lagoons. The system has much appeal and has worked in research trials for short time periods; however, long period trials have shown that the biological components in this system are very sensitive to unbalances and require a high level of management. Also, an excessive level of investment is needed to produce the quantity of methane gas required for a farm, making methane production not economically feasible at this time. Another problem with methane is that gas production is temperature dependent; that is, the liquid used in an anaerobic digester must be heated to approximately 95°F in the winter time to maintain gas production, thus utilizing a large portion of the gas just to keep the digester ""rm. Excess gas is produced in the summer time when it is least needed for heating facilities or grain drying. Also, methane must be stored as a gas because storage as a liquid is im-practical. Therefore, it is neither economically feasible nor practical to use methane gas at the present time. Producer Gas Producer gas is basically a low-heat value gas formed by burning any type of material in a limited supply of oxygen. The producer gas is composed of carbon monoxide and some hydrogen. Producer gas systems seem to be economi-cally feasible and development is currently underway. This system allows crop residue and other biological material around the farmstead to be transformed into usable energy. Producer gas could be made whenever needed, thus elimi-nating the need for storage. A considerable amount of research and development work is necessary before this system can be utilized. Wind power Windpower generation of electricity has received a lot of public interest, and some large grants are underway to investigate its feasibility for large-scale electrical generation. However, for an individual utilizing his own equipment, windpower is not yet economically feasible, although it may provide a limited source of standby power in case of power outage. A disadvantage is the variability in wind velocity. The present wind generators require 8- to 15-mph wind velocity, but the average wind in Kentucky is less than 10 mph. Also, windmills do not generate the type of voltage and power needed in a full-scale swine production system without relatively expensive equipment. So, while windpower seems attractive and much research is presently being conducted, it may not be a feasible source of energy for many years to come. SUMMARY The overall future of using alternative energy sources for swine production facilities is somewhat limited. More research is being conducted on methods to save energy rather than in finding alternative energy sources. This is probably the most effective approach at litis time because saving energy on the farm will assist in energy conservation nationwide while reduL:ittg operating costs. Whenever an alternative energy source or energy saving device is presented one should consider what is being traded in terms of the level of management of the system for the amount of energy saved and the value of that energy. While energy costs may be high for some swine production systems, energy cost alone will not determine the economic feasibility of the swine production system. REFERENCES I. Albright, L. D. 1976. "Ventilation fans vary in oper-ating efficiency." July I August Farm Bull ding News, Milwaukee, Wisconsin. 2. Fehr, R. L. 1972. "Reclaiming heat in livestock ventila-tion." Master Thesis, NDSU, Fargo, North Dakota. 3. Murphy, J.P., C. K_ Spiliman and F. V. Robins. 1977. "Applications of solar energy for preheating ventilating air." ASAE Paper No. 77-3545, ASAE, St. Joseph, Michigan. 4. Person, H. L., L. D. Jacobson and K. A. Jordan. 1977. "Effect of dirt, louvers and other attachments on fan performance." ASAE Paper No. 77-4568, ASAE, St. Joseph, Michigan. 6 The College of Agriculture is an Equal Opportunity OrganiZation with respect to education and employment and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, national origin, sex, religion, age and handicap. inquiries regarding compliance with Title VI and Title VII of the Civil Rights Act of 1964, Title IX of/he Educational Amendments, Section 504 of the Rehabilitation Act and other related matters should be directed to Equal Opportunity Office, College of Agriculture, University of Kentucky, Room S-105, Agricultural Science Building-North. Lexington, Kentucky40546 Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Charles E. Barnhart, Director of Cooperative Extension Service. University of Kentucky College of Agriculture. Lexington, and Kentucky State University, Frankfort. lssued9-7S,3M; 1.5M-11-81 

Energy in Agriculture: Energy for Swine Facilities Part II: Alternative Sources of Energy

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Energy in Agriculture: Energy for Swine Facilities Part II: Alternative Sources of Energy

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