Solar Horse Barn
- Jan 1, 2006
Solar electricity, produced by photovoltaics (PV), is a proven means of generating electricity from the sun, and it's not just for high-tech houses anymore. Whether you want to be more "green" in your electrical use on the farm, you have a remote location without electricity, or you want something to supplement your electrical source, solar power could be your answer. This article will take a tour of solar power to see if brightening the inside of your barn with energy from the sun is a viable option.
Why Solar Power?
Solar power has been around for decades, but arrays of shiny blue panels are becoming more common sights on houses, businesses, and barns around the country as the technology improves, components become more readily available, and energy prices increase. Almost any existing electrical system can be retrofitted to be solar-powered (at a cost), and new construction allows a great opportunity to plan and include many options solar can provide.
While the cost of a PV system is high when compared to today's grid power rates (the payback time for a sizable house system usually ranges from 10-30 years), many people make the choice to power their lives with solar energy because it is a non-polluting, renewable energy resource. With the projected life span of many solar panels being 10-25 years, solar energy is one investment that might eventually pay for itself, as well as being an environmentally sound choice. It also provides "green" power for your kids, their kids, and even their kids, which is truly a rare find in this age of planned obsolescence. Additionally, any properly installed PV system with quality components is codeworthy and insurable.
Some states even offer a tax rebate for renewable energy systems, making the cost of converting to solar energy a little easier to bear. See the Database of State Incentives for Renewable Energy for more information (www.dsireusa.org).
Some folks install alternative systems to enjoy energy independence, so utility power outages won't affect them and they won't have to pay an electric bill. Many rural areas experience frequent outages, sometimes for extensive periods of time, and solar energy is a way to avoid the recurring difficulties that poses.
In some instances, particularly in situations where power is needed a significant distance from existing grid power lines, the cost of installing a solar power system can actually be cheaper than having utility power brought in. For a remote barn, this can be an ideal choice.
Nearly every horse person is familiar with electric fence chargers powered by a small solar panel with a small battery for energy storage to continue operating the fence through dark spells. Many farms and ranches also have small solar electrical installations for pumping water from nearby wells. Powering a barn is merely a different adaptation of the same PV technology used to power these systems.
The information here covers a type of PV system called the "off-grid" or "stand-alone" system. This is an electrical system that generates power from the sun and is completely isolated from the utility power grid. This distinction is made because some great technology now exists for grid-interactive systems with battery backup and grid-interactive systems without battery backup (also called a "straight line-tie"), which are becoming increasingly popular. In these utility interfaced systems, the locally produced solar power mixes with the utility company power, often on a single "net meter" that runs forward if the system is drawing from the grid and backward if more power is being produced than used.
To power your barn with off-grid solar energy, you must first figure out what your electrical needs are for the structure. This can range from the really simple (a single light, for instance) to as large a system as your aspirations and budget take you.
Regardless, every system has solar panels and a deep-cycle battery bank at its core with various disconnects/over current protection (fuses or breakers), wiring, and devices (switches, receptacles, lights, etc.) to complete the job. Additionally, PV systems often have other components such as charge controllers and inverters, which we will discuss in a moment.
Sizing the System
The first step toward designing a solar electrical system for your barn or stable is to understand that it is a completely different animal from mainstream utility grid systems. A standard grid wiring scheme generally is figured for 120 volts alternating current (AC), or sometimes 220 volts AC. Solar electrical panels generate direct current (DC), typically (although not always) at a low voltage (below 50 volts nominal). Nearly every aspect of low-voltage DC current requires different skills and knowledge to work with than high-voltage AC.
As renewable energy expert Bryan Walsh, owner of Solar Connexion in Blacksburg, Va., puts it, "A solar contractor needs to know everything a mainstream electrician knows, as well as all about the different components found in renewable energy systems."
These include making low-voltage connections, installing battery banks, configuring wire sizes and types so that each step of the system is correct for the differing voltages and types of current that are present, familiarity with programming the computerized renewable energy electronic devices, and so on. The point here is to stress that getting a qualified solar energy contractor if you do not possess these skills yourself is essential to installing a safe and properly functioning PV system. Your typical local electrician might not be qualified.
Building any off-grid system begins with a load evaluation. Sit down and put on paper the various appliances and devices you will use in the barn and how much they will be used each day. These might be lights, clippers, a radio, fans, a coffee maker, refrigerator, etc. Be sure to include seasonal needs, such as extra energy usage that might occur during a heavy show season, and consider sizing the system to not run all the heavy loads at once.
At this stage, it is advisable to look into energy-efficient appliances, as energy savings here relate directly to cost savings in the system components. For example, if you're just building the system for basic lighting, and you switch from standard bulbs to compact fluorescents, you will reduce your lighting power needs by two-thirds. That translates into the same lighting for one-third the panels and batteries--a very significant cost difference.
Other appliances are equally capable of producing large savings. For example, a washer and dryer will significantly raise the system's power requirements. If you plan to put a washer and dryer in the barn for blankets, saddle pads, towels, and leg wraps, will you pick the top-loading or front-loading washer? A front loader
typically uses one-third the water of a standard top loader for the same results
(big-time savings if you are powering a well pump), and it boasts much higher revolutions per minute during the spin cycle, removing more water and significantly reducing drying time (another potential saver).
Different regions of the country have varying amounts of overall solar potential based on latitude and weather patterns. This potential does change throughout the year as day length changes. This needs to be factored into sizing your system.
The idea is to size your solar electrical system to be large enough to accommodate all your needs during the shortest days of the year, even considering the possibility of having several cloudy days in a row during winter or rainy seasons. The knowledgeable professional (or novice armed with more printed information than can fit here) will assign a wattage or amperage value to each listed load, take into consideration how frequently it is used each day, then estimate the number of solar panels and batteries required to meet these needs at your specific site.
Panels--The solar panels generate power when sun hits them. These must be positioned to catch maximum sun; you must aim them towards the equator and avoid all possible shading as even a tiny shadow in part of the array can greatly reduce the power produced by the panels. The angle of the array can be adjusted up and down for the time of year to stay focused on the changing angle of the sun in the sky.
Many people have the natural desire to place the solar panels on the barn roof. But placing them directly on the roof is not the best solution. Heat decreases the efficiency of PV panels; getting maximum air flow around them maximizes power production. Also, roofs are typically not engineered for the additional wind load caused by these panels, and roofs that require maintenance (whether painting or installing new shingles) will require that all the solar panels be removed and re-installed each time you work on the roofing. A solid pole mount array (or arrays) or a rack built on the ground is the best option.
Very small systems can have a single, self-regulating panel like those found on the solar fence chargers. Most systems, however, will have panels that are larger and require regulating. A charge controller takes care of this job, switching the power on and off as the battery bank becomes full and when various loads draw power.
Charge controllers--Maximum Power Point Tracking (MPPT) technology is now standard in such charge controllers as the Outback MX-60, which electronically monitors all aspects of the overall system and actually boosts available current that otherwise is lost to the old-school pulse width modulated charge controllers.
Batteries--Every off-grid system needs battery storage to carry the system through each night and spells of bad weather. Never mis-match battery types and sizes; it is always best to purchase new batteries of like kind and keep them in a bank so they age together, then replace the whole bank when their life span is over. This life span can vary quite widely depending on cell quality and the use (or abuse) they receive.
The only type of battery suitable for PV systems is the deep cycle type. These batteries have their capacities figured in amp-hours, not cold cranking amps, and they are physically adapted to the long times spent charging and discharging power (relative to car batteries) found in these systems.
The most readily available type of battery is the lead-acid one. The main consideration for these is temperature. Similar to your automotive battery, the lead-acid types have half the storage at 30 degrees as they do at 90 degrees, so you must figure their capacity in your system for the lowest temperature they will experience. Also, if discharged, they can freeze and burst--a situation you want to avoid. They must be vented to the outside.
Sealed gel cell types are used in applications where there can be no venting, or particularly when the batteries cannot remain level.
Nickel-cadmium batteries are more expensive and difficult to come by, but are the other type of deep cycle cells found in off-grid systems. These are not affected by temperature and will not freeze, but are around 10% less efficient, requiring additional panels to receive a charge similar to the lead-acids.
Inverters--Inverters convert DC power to AC. A range of these devices is available, and you might have to do a bit of research to see which one(s) best suit your needs. First, many small systems can eliminate the expense of an inverter by using only DC appliances and devices made for the voltage of the battery bank in your system.
For instance, if your barn requires only lighting and a water pump and your batteries are configured to 24 volts DC, specialty bulbs and a pump can be installed directly from the battery bank to operate by the 24-volt DC power. If, however, you want the convenience of running the 120-volt AC standard appliances that are so cheap and plentiful from retailers everywhere, you will require an inverter. These come in three basic types: Square wave, modified sine-wave, and full sine-wave. Modified sine-wave inverters produce a current that is slightly different from regular grid power and most things run fine on it, but some electronics can be sensitive to the difference and not function. This can occasionally cause problems like loud humming in fan motors. Full sine-wave inverters produce grid-quality power, but are more expensive. Square wave inverters are an older technology and produce power that is more different from grid power than modified sine wave, and can also cause some sensitive devices to function improperly.
Many off-grid systems have an inverter with a sleep feature--this is standard on all quality machines. This is an electronic brain that can sense when there is no electrical need and puts the inverter into a sleep mode where it does not consume large quantities of power just to stay at the ready. When a need is presented (if you flip on a light switch, for instance), the machine senses this need and instantly powers up the inverter to meet the need. Many installations with an inverter still use DC lighting, so the inverter inefficiency is not needed just for the frequent small load of burning a light or two.
Other components--These might include the specialty breakers, meters, wires, and such devices that go between the larger components.
The properly installed PV system should provide years of reliable service, although it will take a lot of planning and expense not only for the system itself, but also the appliances and ancillary items that it will power. Solar power might be an attractive option for a barn or stable whether your reasons are environmental or independent-mindedness. Three things are for certain--the cost of power will increase, blackouts (rolling and otherwise) will occur, and inflation happens. Solar energy is one alternative to grid power costs in the long run.
--Tom Moates and Christy West
Database of State Incentives for Renewable Energy: www.dsireusa.org
Global maps of average solar power: www.solar4power.com/solar-power-global-maps.html
Solar power basics: www.solar4power.com/solar-power-basics.html
Sounds Good--Now How Much?
The initial cost of a solar electrical installation is significant when compared to bringing in grid power in most cases, even though it will pay out at some point. The cost also will vary greatly with the design and function of the solar system you choose.
Some solar energy websites quote an average cost of $15 per watt for a solar energy system. Now think of that price applied to a single 60-watt bulb, let alone the rest of them. But most of those cost estimates are for homes, and a barn system could be cheaper to install as barns might be less problematic to work in than houses. Also, the quality of equipment varies, which likewise affects price.
Another consideration is that each installation is so unique that average costs might be nowhere near a quote for your needs. Price per watt increases as the size of the system decreases, so a small system for a handful of lights might even be $30/watt. For example, a small DC system to run four lights for four hours in each 24-hour period would be around $2,000 for panels, batteries, charge controller, labor, etc., says Bryan Walsh, owner of Solar Connexion in Blacksburg, Va. He cites another example of a barn system he installed to generate 1 KW of power (as large as some small house systems) to run a barn's lights, clippers, fans, a small refrigerator, computer, etc. that cost $15,000.
The up side, of course, is that you decrease or completely remove your monthly electric bill from the power company. It could even pay for itself, depending on your initial outlay and monthly savings.
So how do you know if solar power will fit in your budget? Find a solar contractor, map out your needs, and adjust from there.--Tom Moates and Christy West
About the Author
POLL: Mosquito-Borne Diseases