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1209 PD: Energy-saving options for you are around every corner

Loretta Sorensen Published on 05 August 2009

Energy saving options for dairies are widely varied, and new options are developing regularly.

Some options are tried and tested and others involve emerging technology. Incentives and rebates may also apply to some new energy-saving technologies.

Simple, inexpensive changes in a dairy can begin with installation of fluorescent light bulbs to make lighting as much as six times more efficient. Besides increased profitability, actions such as correcting improper ventilation and inefficient vacuum pumps can have positive effects on cow comfort and behavior, resulting in greater milk production.

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On a typical dairy farm, energy use stems from vacuum pumps (17 percent), milk cooling (25 percent), lighting (24 percent), ventilation (22 percent), manure handling (4 percent), electric water heating (4 percent), feeding equipment (3 percent) and miscellaneous (1 percent).

Ensuring that equipment is efficient and operating properly is easy and inexpensive. Variable speed drive (VSD) pumps are highly recommended because they’re more efficient. Scroll compressors require less energy than reciprocating compressors because the scroll type has fewer moving parts. Dairy producers should consider these options if replacement or major repair is required for existing pumps. Well water plate coolers can reduce cooling costs as much as 60 percent.

The most efficient fans move 20 cubic feet per minute (CFM) per watt. Keeping fan blades clean is key as dust accumulation of one-eighth of an inch can reduce fan performance by 40 percent.

Alternative energy forms that provide significant savings include solar energy water heaters, a heat recovery system, an anaerobic digester to produce biogas to create electric power and use of photovoltaics to convert light to electricity.

Solar water heating systems are comprised of solar thermal collectors, a fluid system to move absorbed heat from the collector to its point of usages and a reservoir tank for heat storage and subsequent use. Evacuated tube collectors are widely used in Germany and heat water to the boiling point. However, flat-plate collectors are more economical and are well-suited to commercial and industrial heating and cooling applications. A dairy’s solar hot water system will require a heat booster system to satisfy equipment cleaning requirements.

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Dairy farmers can design an anaerobic digester that specifically fits their individual needs. Bio-gas can generate electricity and warm floors in the dairy barn. The resulting liquid nutrients can be used for crops. The energy in bio-gas generated by 100 dairy cows each day is equivalent to the energy of one barrel of oil. Plants can more readily absorb nutrients in the liquid manure produced by the digester. Producers may also be able to obtain payment for carbon credits through use of a digester.

AgStar, an Environmental Protection Agency program, partners with farmers to develop digester designs. They have developed six different types of digesters that include an upright digester that treats only liquids after the solids are separated; upright mixed digester treating all manure from a herd; conventional plug flow digester with flexible cover; covered pond digester with insulated sides and cover; low cost plug flow digester utilizing a plastic liner inside a large steel culvert; and a community digester owned and operated by three or four farms. More information about AgStar and digester designs is available at www.epa.gov/agstar

Treated, weed-free solids produced by a digester have been used for dairy bedding. With proper treatment, solids can significantly reduce costs and the material can be recycled again and again through an anaerobic digestion and separation system.

Photovoltaics involves solar cells or photovoltaic arrays combined to make panels that collect light and convert it to electricity. Typically, sunlight produces 1kW (1,000 watts) per square meter. As much as 15 to 21 percent of the collected energy can be converted to electricity that is then stored in batteries for future use or fed into an electricity supplier’s grid. The greater the area of the panels, the more energy is captured. Because this type of power is dependent on sunlight, it’s necessary to provide a means of storing excess energy.

Sahr Dairy in Bricelyn, Minnesota, is working with Redline Energy Solar Installation to develop a pilot project using photovoltaic panels at the dairy. Redline has applied for a grant from the State of Minnesota to help cover the cost of solar panels and installation. The 1,200-cow, 24-hour dairy is a fourth-generation farm employing 18 full-time personnel. Owner-operator Mark Sahr is intensely searching for an alternative to purchasing electricity from the local co-op. His winter electricity bill is $6,000 and over $10,000 during summer. Electricity is used for milking machines and associated systems, milk cooling, water pumps and fans. He also heats water for sterilization of milking components, laundry and animal cleansing.

“We’ve been looking for something effective with low maintenance,” Sahr says. “This is just a pilot project, but it seems to be a feasible way to cut energy costs. Something that needs to happen before this system works on a large scale is higher feed-in tariffs. Right now our rate is only 8 cents. California’s rates are 22 cents and Florida pays up to 32 cents. Power companies need to pay more for the electricity they’re buying from systems like this. We haven’t seen much interest in this from other producers yet, but if rates keep rising that may change.”

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Wind and hydro power are long-term options that need more study and testing before they’re ready for wide adoption. Rotating turbine blades converting wind power to electricity can generate a dairy’s power if site topography generates adequate wind. As the wind power market develops in Australia, wind turbines suitable for dairy farm requirements will become more common. A micro hydro system with access to flowing water may also generate electricity to charge batteries and supply AC power directly. Flow rate of the water and amount of head pressure and gravity will determine the amount of power generated. The efficiency of converting water power to electricity can vary and ranges from 30 percent to 70 percent. Approval from local and state authorities is required if modifications are made to a watercourse.

Johnson notes that producers need to identify their state rebate or tax credit and other financial incentives because they may receive as much as a 55 percent reimbursement for energy-saving technology.

“Impact of changes will be determined by your current energy source costs,” Johnson says. “Electricity rates in South Dakota are much lower than other states. There are no alternative energy state rebate or tax credits. A producer has to carefully review all these details before deciding which alternative energy will provide the best payback.”

North Carolina State University Extension Educator, Geoff Benson, encourages dairy producers to look beyond their barns and consider no-till or lower input measures to produce crops. Calculating fuel costs for each step of the farming process will help farmers determine which process is most cost-effective. Whatever energy-saving practices dairies adopt, Benson says producers should stay clearly focused on profitability in the process.

“Start with your largest cost items,” Benson says. “To evaluate energy use, do either a third-party or self-audit. Consider likely changes in energy prices.”

Benson suggests producers evaluate their current energy resources and costs and project future increases. They should also assess investment and ownership costs, as well as changes in operating expenses related to new technology.

“Determine what you will save and how quickly you will see payback,” Benson says. “Saving energy is important, but cash flow circumstances may not allow for new investments right now. Make sure new investments are both profitable and feasible from a cash flow standpoint and that you’re able to pay your bills today.” PD

Loretta Sorensen is a freelance author from Yankton, South Dakota.

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