Rural Renewable Energy

Highlights

• Agricultural producers have long been on the forefront of renewable energy use
• Rural locations are ideal for wind and photovoltaic power applications
• Agricultural waste and energy crops may become a new source of farm revenue

Introduction

From the 200-foot tall windmills in Holland to those of west Texas, agricultural producers have long relied on renewable energy for their livelihoods. Whether the task was pumping water, drying crops or cooking, farmers have always relied on three things: the sun, the wind, and the rain. In fact, solar energy is the key that allows farmers to unlock the Earth’s potential, whether it is the kinetic energy captured by the windmill or the photosynthetic energy captured by plants.

Water Pumping

Water pumping may be the most common use of renewable energy in agriculture, but can be applied to residential or business use as well. Two basic types of electrically-driven water pumps are based on renewable energy systems.

PV-Powered Pumps

Submersible electric water pumps powered by photovoltaic (PV) modules are suitable for small to medium scale pumping needs up to about 2 horsepower depending on the depth of the water well. Given their simplicity, lack of moving parts and long life, these systems are growing in popularity.

Wind-Turbine Powered Pumps

A relatively new type of pump system, this method uses the electricity generated by a small wind turbine to directly power a submersible or centrifugal pump. U.S. Department of Agriculture tests here in Texas have compared this newer technology with mechanical windmills. While costing about the same as mechanical systems, the USDA found that the wind turbine systems produced almost twice the volume of water. Larger wind turbines can pump enough water for small-scale irrigation. Solar/wind hybrid pumping systems are also available.

Electric Applications

With the cost of extending a power line as high as $30,000 a mile, reliable PV and wind power systems offer farmers and ranchers many uses they otherwise could not afford.

Electric Generation

PV systems are simple, reliable and require little maintenance. While relatively expensive at about $6,000 per kilowatt, PV systems costing as little as $50 can be a perfect fit for providing small amounts of power around the ranch. In rural areas where the wind is fierce, wind turbine systems costing about $2,500 per kilowatt are usually a better investment than PV, especially for applications needing a lot of energy. In some cases, large wind turbines may even provide electricity more cheaply than the local electric company.

Water Tank De-Icers

An essential technology for ranchers in cold climates, water tank de-icers are powered by a PV module that provides power to a small compressor that generates air bubbles on the bottom of the water tank. The movement of the water prevents ice from forming on the top of the tank. Performance of these units is best on tanks that are sheltered or insulated.

Electric Fences

Powered by PV modules, commercially available units can keep a fence electrified day and night. These units can deliver brief shocks with small pulses of low current at around 8,000 to 12,000 volts potential – more than enough to keep livestock contained.

Gate Openers

Gate openers are an ideal candidate for PV power because they are often located far from available power lines. Some models are brawny enough to open gates 16 feet wide and weighing up to 250 pounds. These gate openers can utilize wireless
remote control mechanisms or digital keypads, both of which offer convenience and security.

Biomass Applications

Many farmers used to burn or plow under farm wastes. The advent of new technologies that convert biomass material from plants or animals into valuable energy may give farmers and ranchers moneymaking alternatives to such practices.

Agriculture Wastes

In many cases, troublesome waste products from agricultural cultivation and processing can be effectively used as a low cost fuel for making electricity or process heat. One cogeneration operation near Houston burns rice hulls from a local mill to make electricity that is sold to the local utility. Other candidates for agricultural waste feed stocks in Texas include cotton gin trash, sugarcane pulp, and peanut shells. Commercial development of small biomass gasification systems may soon assist this market. On dairies and large feedlots, manure can be processed to make electricity. Doing so reduces odor and potential pollution problems while adding a revenue source.

Biofuels

While Texas refineries are among the nation’s leading producers of ethanol-based automotive fuels, the ethanol feed stocks used in these blending operations come almost exclusively from grain produced in mid-western states. Texas farmers growing corn or grain sorghum would have another market for their products if local biofuel producers considered shopping locally. Over the next few years, markets may develop for the cultivation of dedicated energy crops such as switch grass, poplar trees or other fast-growing crops grown specifically for energy uses. Before long, growing our own fuel could become a reality.

Sunlight contains a lot of infrared and ultraviolet as well as all other colors. Some people think heat is a different form of energy from light. Both are forms of electromagnetic radiation and both can provide energy. Since most infrared and ultraviolet are blocked by Earth’s atmosphere, solar energy, whether it is used to heat water or is converted to electricity in a PV cell, comes from the visible part of sunlight.