Mobile Solar Demonstration Kit
With the help of project energy technician Vertis Bream, the FCSL has enacted a portable solar electricity demonstration. The demo kit is made up of all of the components needed to provide remote power generated by the sun, and is very useful for educating the public about solar electric possibilities. Children love to get a "hands-on" look at solar power in action. The kit serves as a mobile AC power source, and is equipped with a water pump that runs directly from the solar array for a real time demo of solar power.
Staff of the FCSL use the mobile solar kit as a power source on the farm and at field events. The kit has been used to demonstrate the workings of solar electricity to hundreds of adults and children on field trips and at farmer’s markets, environmental fairs, and other agricultural events.
The solar demo kit consists of the following items:
- 2-55 watt BP Solar modules (110 watts total power)
- 2-12 volt 105 amp-hour batteries (210 amp-hours total storage capacity)
- 1200 watt power inverter for converting 12 volt direct current stored in the batteries to 120 volt alternating current.
- A charge controller to regulate battery voltage
- A 12 volt water pump to run directly from the solar array
- Guages to monitor battery charge and power generated by the solar array.
- All components are mounted on a convenient, portable cart for easy transport to field events and around the farm.
Solar Electric Fence Charger and Solar Security Lights
One of the most practical uses of solar electricity is in remote power situations. In locations that are far away from grid power or wired buildings, solar electricity can enable affordable and convenient operation of electric devices. At the FCSL farm, we have found solar fencers and solar security lights to be very handy.
The solar fence charger is used to electrify a mobile fence used for chickens. Rather than keeping the farm’s laying hens penned up in a building or yard, the farmers move them around, enabling the chickens to consume fresh greens and insects, while spreading their manure on fallow fields. The solar fence charger (commercially available at most farm stores) provides a mild shock to keep the chickens from roaming into nearby crops. The fence charger is easily portable, and the whole unit of chickens, house, fence, and charger can be moved to new ground in about an hour or less.
Solar security lights are quite handy for lighting up dark spaces that are far from electricity sources. The FCSL is using them to provide student-safe travel at night between the farm and main campus. Solar security lights are commercially available "instant on" fluorescent lamps, complete with mini solar module, lamp, sensor, and a battery that will store electricity to make it through periods of cloudy days.
Solar and Wind Energy Systems in the Owens Barn
The FCSL has set up a wind and solar electricity demonstration at our main public building, the historic Owens Barn. Tour groups and visitors to the barn are intrigued by the opportunity to learn more about the components involved in an off-grid renewable energy installation.
Our "hybrid" system consists of:
- An 800 watt wind generator mounted on a pole attached to the farm silo
- 330 watts of solar power (2-165 watt modules)
- 4 350 amp-hour, 6 volt batteries (provides 700 amp-hours of storage at 12 volts)
- A charge controller, safety disconnects, and monitoring gauges
- A 1200 watt power inverter for converting 12 volt direct current to 120 volt alternating current (to power household devices)
- 12 volt DC lighting
- 120 volt AC compact fluorescent lighting
- Understanding Renewable Energy
One of the most common questions that arises during field or farm demos of renewable energy is "How much would it cost to power a house with solar electricity"? Unfortunately, there is no easy answer, but actually a series of questions, such as: How much power is presently consumed by the house? What appliances are being run, and how much power do they require? How many hours will they be used per day or week?
Powering a home with renewable energy is fairly uncomplicated, but not nearly as simple as plugging things into a wall socket and paying a monthly power bill. One must learn the language of electricity, its key concepts, and the basic workings of components in a system to successfully power a building with "green" energy. However, embarking on a renewable energy project enables a consumer to understand his or her power consumption in detail, and inevitably leads to energy conservation.
Steps to getting started with renewable energy:
- Read a few books or articles on the subject, or contact a reliable dealer of solar electric equipment who will offer free consultations. We have had good experiences with New England Solar Electric. Home power magazine and Solar Energy International are also indispensable resources
- Estimate the power consumption of the proposed building by adding up all of the loads, and how many hours they will be used per day. This will help you to size the system.
- Consider transferring some heavy loads to other power sources. Solar and wind energy technologies are fairly expensive, and are best used for powering devices that must be powered with electricity (computers, lights, etc). Some heavy energy users, such as stoves, and building heating and cooling, can be cost prohibitive to a renewable electric system, but can be cost effective in other ways (wood or gas heat, cooling by proper building design).
- After settling on the amount of energy that will be needed for the building, calculate the amount of battery storage and generating capacity required.
- Shop around for affordable components. A reliable dealer with good customer service is worth paying for!
- Decide whether to install the system yourself or to hire an experienced installer. Simple cabin systems can be easily installed by homeowners, while whole-house systems will be more complicated.
Other options for renewable power include purchasing a grid-tied inverter, which allows the system to feed power back into the utility wires (and to run the power meter backwards!) in times of surplus production such as prolonged sunny weather or windy days. Utility companies should be consulted for permission before attempting any grid-tied systems.
When starting out working with renewable energy, there is a steep "learning curve" while the user becomes accustomed to the equipment and its operation. We can provide the following lessons from the initial years of our renewable energy project:
Deep cycle batteries are an essential component of all but the most basic renewable electric systems. The battery “bank” stores energy harvested from the sun and wind for use when the electricity is needed. Batteries are not cheap, but with proper maintenance they can last for many years. Most commonly used are flooded lead-acid batteries, in which lead plates are bathed in a solution of sulfuric acid. As the batteries charge and discharge (or “cycle”) some of the fluid will be lost as hydrogen gas. This fluid must be replaced periodically or the batteries can become damaged. Once a month or more, we check the level of fluid in our battery bank, and top it up with distilled water if necessary. A battery filler bottle is a cheap, handy item for conveniently adding water with no mess.
Solar panels and wind generators will overcharge a battery bank if the system is not monitored closely. Batteries have a limited storage capacity for energy and once they are “full”, excess charge can begin to cause harm. The easiest way to prevent overcharging of the battery bank is with a charge controller. These relatively inexpensive devices sense the level of charge in the batteries and will disconnect the solar array from the batteries as they reach full charge. The better charge controllers will also display interesting information about the system, including battery voltage and the amount of energy being generated by the solar array. Wind generators must not be disconnected from the batteries, so if a state of full charge is reached, extra wind energy is “dumped” into water heating or lights using a diversion load controller.
Photovoltaic Panel Installation
Photovoltaic (solar electric) panels or modules are made of glass or other breakable materials and should be securely installed on a building, pole, or other mounting system. Building mounts should face to the south (in the northern hemisphere), so that they can catch the maximum amount of sunlight possible. Our barn-mounted photovoltaic system is mounted on an adjustable frame so that it can be angled upward in summer when the sun is high, and toward the horizon in the winter when the sun is low in the sky. Ground mounted panels should also be securely mounted to a wooden frame or pole or they may be blown over and damaged during high wind events. All photovoltaic components should be “grounded” in case of lightning strikes.
Installing the wind generator
Wind generators must be installed firmly upon a sturdy pole or tower. Ideally, the height of the generator should be at least 15 feet or more above any trees, buildings, or other obstructions in the surrounding area. This helps to capture the maximum amount of wind energy and cuts down on turbulence caused by swirling air currents.
At the Fulton Center for Sustainable Living, we used the existing concrete silo at the Owens Barn to support the pole for our wind generator. A steel hinge plate was mounted at the base of the silo in concrete, to which the 50 foot steel pole was attached with heavy bolts. We then routed a rope through the top of the silo to the pole and used a tractor to pull the tower up to a vertical position. The pole, with its wind generator on top, was then secured to the silo with stainless steel cables. It was very handy to have a “people lift” (cherry picker) handy to get up on the silo for securing the cables.
Care of the wind generator
Wind generators are fairly maintenance-free. Once installed, the wind machine makes power when the wind blows and rests when the weather is calm. It is a pleasant and satisfying sight to watch the blades spin in the wind and to know that some “free” energy is being harvested.
The wind generator must always be kept under a load- that is, connected to the battery bank. If the wind generator is not connected to a load, it may “freewheel”, spinning very fast and potentially damaging the circuitry inside. We learned this lesson the hard way during a freak summer thunderstorm when we happened to have the battery bank disconnected for servicing. Our 800-watt wind generator spun out of control in the brief high winds, damaging some of its components. Servicing the generator was thankfully not expensive, but retrieving it from atop the 50 foot high mounting pole was a chore!