Solar-powered devices aren't just for the off-grid adventurers and power-hungry gadget-loving crowd, they're also quite useful in the farm and urban garden, as they can provide the juice needed to fulfill many basic functions for the small grower and farmer alike.
Alternative energy has a long history on farms and ranches, beginning with windmills for water pumping and wind generators for electricity for remote locations. More recently, you'd also be more likely to see a small solar charger powering an electric fence than a PV array on a residential street. And with the advances in both solar technology as well as remote automation, using the power of the sun to run parts of a farm or garden operation is easier than ever.
Solar Power Production
Using an array of PV panels (or a single one) and a battery bank, solar power can be used in a very conventional manner on a farm, as a remote power source for any electrical needs. This type of installation isn't for those with a small budget (although a tiny system for select power needs can be affordable), but it has the advantage of being able to power a variety of things, with the only limitations being the size of the array, the capacity of the battery bank, and the extent of the wiring in place to route the electricity.
For the small-scale grower, or as an entry point for solar power, small standalone systems with PV panels, charge controller, and battery bank included, are available either as a package or (for the DIYer) can be built up from the wide variety of components now available.
Producing solar power on a large scale by adding a grid-tied solar farm to a conventional farm, is starting to make good business sense these days, both to offset the operation's energy use and to earn a steady income from selling power back to the grid.
Solar Livestock Fence Chargers
Farms with livestock need fencing solutions that are dependable, effective, and adaptable, and an electric fence powered by the sun fits the bill, whether for permanent installation or for moveable paddocks. Readymade solar fence chargers are widely available, in varying voltages and capacity, and some of them can power a fence several miles long. For the DIYer, the availability of affordable parts these days makes it fairly simple to piece together a system that is a custom fit for specific sites and needs. Because an electric fence doesn't need to be nearly as sturdy as a regular fence, portable solar fencing can keep the stock in a specific area for managed grazing and be moved quickly and easily.
Solar Water Pumping
Another fairly traditional use of solar power on the farm is a solar-powered well pump, especially for remote watering of livestock. A very basic setup can be as simple as a small PV array with no battery storage, which pumps water into a watering and storage tank only when the sun is shining. Adding battery storage and a controller to the unit allows for more control and more capacity, especially with wells with slow flow rates that may need to be pumped 24 hours a day.
Using the sun's energy to pump water from the ground into a reservoir isn't the only watering application possible, as some farms are using solar-powered irrigation to grow their crops. The most basic system uses drip irrigation attached either directly to the well pump, or to a storage tank that would gravity-feed the water to the rows. For bigger farms, such as those using center-pivot irrigation (which is responsible for those giant green crop circles seen when flying over ag land), solar power is an option, replacing diesel, propane, or grid power as the motive factor in these systems.
Solar Water Heating
Heating water by using the energy of the sun isn't nearly as high tech as generating electricity is, but it's just as necessary (and appropriate) in many farms. A solar water heater can provide hot water for washing or cleaning, and in some instances be used to heat the water for a radiant floor system for either people or animals. Indirectly, using water-filled drums or tanks that gain heat from the sun can be used in greenhouses as thermal mass, moderating the temperature and providing warmth when the sun is down.
Solar Air Heater
Using a solar collector to pre-heat air going into outbuildings, greenhouses, animal enclosures, or office or living spaces is another great low tech way to include solar energy at farms or urban gardens. Because the solar collector has no moving parts, and can usually be built with cheap or free components, they are a good fit for the DIYer and tinkerer. By adding them to south-facing windows, the devices will capture some of the energy of the sun as heat and deliver it to the inside of the rooms, without using any power.
Having the proper amount of ventilation for fresh air intake and hot air exhaust is an important element for greenhouses and animal enclosures, and solar energy can be used to power and automate those systems. The simplest versions use the heat of the sun to open a vent, which will then draw warm out via natural convection, but more extensive ventilation systems use an exhaust fan. The fan can be powered directly by the sun (fan runs as long as the sun is shining), or through a thermostat (fan only runs during the day when set temperature is reached), or even as an extension of a larger solar power system. With the explosion in mobile and wireless technology, many of these units can now also be controlled as a remote unit (Arduino or Raspberry Pi projects).
For the farmer who produces crops that either need to be dried before sale, or can be dried as a value-added product such as converting grapes into raisins or plums into prunes, solar dehydrators can be a great tool. Most of the solar dehydrator designs are completely passive, like the solar air heater is, and because no moving parts are involved and they can be created from common building materials, using the sun to dry food is a cost-effective method. For more control, small solar-powered vents and fans can be added to the dehydrators, so that on hot days, the food inside isn't burned to a crisp. (And solar ovens are a great way to cook dinner for a bunch of hungry farmers!)
The sun can also light up the night, as solar-powered lighting solutions are available for a variety of applications around the farm and garden. From the small solar LED garden lights to larger units for illuminating entries, gates, and outbuildings, solar lighting can be a great fit for not only off-grid and remote locations, but also for the urban gardener and hobby farmer.
Solar Powered Sensors
Gathering data for more optimal growing or watering is a crucial part of a large farm, and advances in remote monitoring devices have now made it possible to determine precipitation and soil moisture, analyze location-specific weather data, and more. Feeding and watering of animals can be monitored by remote solar-powered sensors, as can the reading of their electronic tags for precise tracking of movements.
Solar Powered Vehicles
Powering farm equipment, such as a tractor, from electricity generated from the sun is another great application for solar on farms. Electric vehicles have plenty of torque for power, and because they are efficient and quiet, may find more and more adoption around the farm. While solar tractors aren't exactly commonplace, there are innovative farmers converting or building their own versions, and small electric vehicles (utility or golfcart-types) can be charged via a solar panel for a greener fuel.
Solar power on the farm and in the garden can provide the electricity or heat needed to run essential parts of the growing operations, and while they may take an initial investment, the return on that investment could keep coming back for years and years.