EB1832

Washington State University Cooperative Extension publications contain material written and produced for public distribution. You may reprint written material, provided you do not use it to endorse a commercial product. Please reference by title and credit Washington State University Cooperative Extension.

Issued by Washington State University Cooperative Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and sexual orientation. Evidence of noncompliance may be reported through your local Cooperative Extension office. Trade names have been used to simplify information; no endorsement is intended. Published June 1997. Subject code 669. G EB1832

Renewable energy technologies represent an important, commercially available energy resource for Washington. For many power applications, renewable energy sources are already the most cost-effective answer. Some of these innovative and alternative technologies are the use of photo-voltaics for lighting or communications systems; wind, solar hot water or space heating systems; geothermal heat pumps for buildings; micro-hydro; and the use of biomass.

Installation and long-term maintenance of most of the renewable technologies presented in this book proved less expensive than the cost of conventional solutions, such as providing power from the nearest electrical line.

Washington's local and state government agencies can contribute to a safer and healthier environment through the use of renewable energy systems. Each installation of these energy systems is one more small step toward a sustainable energy future.

Easy Expansion

Most renewable energy systems can be designed for easy expansion should the power demand increase in future years. The modular nature of most renewable energy systems makes them easy and cost-effective to upgrade.

Long Service Life

Wind and solar energy systems are durable, can withstand harsh climates and geography, have few moving parts, and can last 30 years or more.

No Fuel Needed

Stand-alone renewable energy systems do not need a fuel supply. Even hybrid systems, such as renewable energy systems with natural gas or diesel backup, need far less fuel than conventional alternatives. Renewable energy systems avoid the budgetary problems of fluctuating or escalating fuel costs.

Low Maintenance

A well-designed solar or wind energy system will require little attention and can usually operate unattended. The savings in labor costs and travel expenses can be significant.

The pages that follow give examples from communities that successfully developed creative approaches to meet the energy demands of their public facilities. Also included is a glossary of terms and a partial list of manufacturers. For information on obtaining grants, receiving technical assistance or other information on applying renewable technologies, please call the Washington State University Cooperative Extension Energy Program office at (360) 956-2000.

A wind turbine captures the wind's energy to produce electricity. The system consists of a rotor (two or three blades, a hub and a shaft), a gear box, a tower, control equipment, and power conditioning equipment. Wind energy systems produce power by transmitting the rotational energy of the rotor to a generator or alternator.

Small wind systems have been developed to the point that they can achieve very high reliability levels-typically 97 to 98 percent availability with little maintenance requirements. Small wired systems are frequently the most cost-effective option in any area with annual wind speeds exceeding 8 mph. In addition to grid-connected or standalone systems, small wind turbines work extremely well as hybrid systems with diesel generators, natural gas, or solar systems such as photovoltaics.

Small wind systems, less than 50 kilowatts, are typically mounted on towers 80 to 130 feet high and should be installed on property sizes of at least one acre. Wind speed varies with time of day, season, height above the ground, and type of terrain. Proper siting in windy locations, away from large obstructions, enhances a wind turbine's performance.

Wind resource evaluation is a critical element in projecting turbine performance at a given site. The energy available in a wind stream is proportional to the cube of its speed, which means that a site with just 25% greater wind speed can produce twice as much energy as another site. It is recommended that wind measurements be taken at the proposed site of power generation. If site-specific measurements are not possible, alternate methods for estimating the resource may be employed which include: (1) consulting wind system owners nearby, (2) collecting wind data from the local weather service as well as systems data published in the U.S. Department of Energy's Wind Resources Atlas, and (3) collecting empirical data such as assessing the amount of vegetative deformation. Vendors selling wind systems should also be able to provide assistance in determining the wind resource in a specific geographic location.

Small wind systems can be used to power a variety of applications from remote repeater stations to high wind warning signs.

Wind energy is used to generate electricity for a variety of applications. A few are listed here:

• Electricity generation
• Battery charging
• Water pumping
• Communications systems
• High wind safety warning signs

Solar hot water systems collect the thermal energy in solar radiation to heat water. These systems have two common elements: a solar collector and a storage tank. Depending on geographic location, the amount of water used, and electric utility rates, system payback can occur between three and eight years. The payback time for systems installed during new construction is usually shorter than retrofit projects due to reduced installation costs.

Most solar collectors are liquid-type, flat-plate collectors, which consist of an insulated metal box, a solar absorbing surface and tubing with liquid to carry away the heat to a storage tank. There are two main types of flat plate collectors: glazed and unglazed. The most common type of collector, the glazed flat-plate collector, consists of liquid-containing tubes arranged in a flat configuration and housed under glass or some other transparent material. Such collectors are typically used for water and space heating systems. Unglazed flat-plate collectors are generally made of metal or plastic, without a transparent covering, and are commonly used to heat swimming pools.

As the radiant energy from the sun is converted to heat in the solar collector, the water is moved to a storage tank. Although conventional electric tanks can be modified for use with a solar system, specially designed, sized and super-insulated solar tanks are available The tank should be large enough to provide one day's hot water demand. A backup heating system (electricity or gas, for example) is used to ensure an adequate supply of hot water during cloudy weather or periods of excessive hot water use.

Solar water heating systems can be classified as either active or passive, depending on whether water is pumped through the collector to the point of use, or whether the collector relies on gravity or water supply pressure to move water through the system.

Collectors are usually mounted in a fixed position, frequently on the ground or on a south-facing roof, in an area with minimal shading throughout the day. Sun tracking hot water systems had many mechanical problems in the past and are not recommended. In regions with harsh winters, the collectors and support structure or roof should be able to withstand high winds and support snow and ice loads.

Listed here are some of the successful applications for the sun's radiation converted to heat:

• Space heating systems
• Small buildings
• Large office buildings
• Institutional buildings
• Schools, prisons, hospitals

• Swimming pools
• Washing
• Cooking
• Cleaning
• Car washes
• Laundries
• Commercial food processing

Photovoltaics (PV) is a technology in which radiant energy from the sun is converted to direct current (DC) electrical energy. The word photovoltaic comes from "photon," a unit of light, and "voltage," a unit of electric potential. While the public is most familiar with the use of PV cells for calculators and watches, many local, state and federal agencies are already using this solar technology for some of their energy needs This use has grown from only a few thousand applications in the early 1980s to hundreds of thousands today.

The heart of a photovoltaic system is an array of solid-state devices called solar cells. Solar cells are made of semi-conducting materials, typically silicon with trace amounts of other elements. There are two primary PV technologies in use today: crystalline and amorphous silicon. When sunlight (comprised of photons) hits the surface of the cells, electrons begin to flow and electricity is generated. Each solar cell produces approximately one-half volt. Higher voltages are obtained by connecting solar cells in a series.

Groups of solar cells are packaged into standard modules designed to provide useful output voltages and currents. The typical photovoltaic module contains 36 silicon solar cells, connected in series to provide enough voltage to charge a 12-volt battery. The series-connected solar cells are encapsulated and sealed, most with a tempered glass cover and a soft plastic backing sheet. The laminated module protects the electrical circuits from the environment and gives the long life that photovoltaic modules are noted for. These framed units with their support structures form arrays, which are then set up to meet the electrical current requirements for desired applications. The modular nature of photovoltaic systems permits them to be expanded easily, ensures minimal maintenance and allows simple repair or replacement of the systems' components. PV cells are quite durable. When installed properly, the lifetime of a PV module could be several decades.

Photovoltaic modules produce electricity from the sun even on cloudy days, but for many applications the energy is needed at night. Batteries are the most common form of energy storage. A charge controller may be needed to help protect the batteries. Batteries need to be protected from the weather. If the load requires alternating current (AC), an inverter is used to convert the DC power to AC.

There are many applications for which PV power can save money over the lifetime of the system. The following pages provide some examples.

Cost-effective lighting systems are powered by photovoltaics operating throughout the world -- tens of thousands just in the United States. Their principal uses are listed in the sidebar to the right.

Improvements in the efficiency and reliability of lamps and batteries, coupled with reductions in the cost of photovoltaic collectors, have significantly improved the economics of these systems. For example, security lighting can be powered by photovoltaics at a fraction of the cost of extending utility lines to remote areas. The lamps can be controlled by timers, photocells, or sensors. Many firms in the United States dealing with photovoltaics sell prepackaged systems containing a photovoltaic power supply, battery, lamp and ballast, and controls.

Most photovoltaic lighting systems operate at 12 or 24 volts DC. Although incandescent and halogen bulbs that operate at 12 volts are available, fluorescent lamps are recommended for their higher efficiency -- up to four times that of incandescent lamps.

Batteries are rewired for photovoltaic-powered lighting systems. Because of this, a state-of-charge controller may be required to avoid overcharging the battery or to prevent deep discharge. The batteries and control are usually placed in a weather-resistant enclosure. The array or module can be mounted on a pole or on the ground, or even on the structure to be illuminated. Elevating the photovoltaics module can reduce the risk of vandalism.

The principal uses of photovoltaic lighting include:

• Highway signs
• Parking lots
• Marinas
• Pathway security
• Bus stop shelters
• Streetlights
• Traffic hazard signs
• Traffic control signs
• School zone safety lights
• Billboards
• Fire station preemption
• Railroad crossings
• Disaster relief shelters

The city of Grand Junction welcomes visitors with a PV-powered road sign that displays the city's name and logo. Two of these signs are located on either side of the city on Highway I-70. Three 75-watt modules, located several feet from the sign, charge the batteries. The batteries provide energy for the lights for 8 hours each night. Thus, the lights remain on throughout the night during the summer and until 1 a.m. during the winter. The battery capacity can maintain the lights for 5 sunless days. The cost of each PV system was $2,300 -- considerably less than a line extension. The systems have performed according to expectations since they were installed in 1988.

Additionally, the signs have been well received by the entire community, because the lighted signs provide a pleasing highlight and architectural statement that is in keeping with the city's image.

The Bent Tree Community Association, located in a west Miami suburb, installed 26 PV-powered streetlights in the summer of 1991. Two 48-watt PV modules charge two batteries. The battery capacity enables the light to operate from a full charge for 12 hours a night for 4 nights without recharging.

The community association decided to use PV instead of the local utility service for three reasons. First, the initial cost of each PV streetlight was approximately $2,000 less than the utility service, because of trenching requirements for the electrical lines. Second, the city would have had to raise community taxes to pay for these utility streetlight costs. And, third the community would have had to pay monthly utility bills for the lights.

Both community officials and residents have been satisfied with the performance of the systems despite one case of vandalism. In fact, in the aftermath of Hurricane Andrew when utility power was out for 33 hours, the only street light came from the 26 PV lights.

The city of Lacey, Washington, Police Department is employing PV-powered speed warning devices. Systems like this are especially effective in neighborhoods that prefer to avoid the noise and air pollution emitted from gasolinepowered generators.

The city of Carrollton, Texas, a suburb of Dallas, has installed 30 PV-powered school zone flashing safety lights for 15 schools. A 90-watt PV array charges two deep-cycle batteries that power the flashers (one or two 35-watt halogen lamps) and the programmable controls. The flashers are used during the school year (fall, winter, and spring) and can maintain operation for 12 sunless days when the battery is fully charged.

Installation of a grid-connected safety light (including the wire, pole, controls, sign, and flashers, as well as underground trenching of approximately 300 meters [1000 feet]) was estimated to cost $7,000. The cost to install a similar system using PV power was only $3,400. The city of Carrollton also pays $50 per site for a yearly preventive maintenance visit.

Since the systems were installed in 1990, city officials have been extremely satisfied with their performance. Not only have the flashing lights performed according to expectations, but there have been no component failures. City residents are also satisfied with the systems, and many have complimented the city. City officials said that they "have received more positive comments and pats on the back" for PV-school zone safety lights than on any other recent city project.

Carrollton has now made it a policy to install only PV-powered flashers. The city not only saves money but reduces paper work and installation time. The city plans to install 75 more PV school zone safety lights by the end of 1994. When this project is completed, all the schools in the Carrollton district will have PV-powered flashing lights.

Monitoring is one of the largest applications for photovoltaics.

Instrumentation and data communications equipment require a power supply to maintain their batteries state of charge. Photovoltaic power supplies are ideal for this application because of their simplicity and reliability. Most applications require less than 200 watts. Almost all of these systems operate at 12 volts DC. The load can vary with the activity, whether continuous or periodic, or the rate at which samples are taken or data are transmitted.

Many monitors require only one module. The data acquisition equipment and batteries are usually located in the same weather-resistant enclosure, which is sometimes buried for protection. Controls for these power systems are usually minimal, but they sometimes require a battery-charge regulator. The module is usually mounted on the ground or on a pole; it should be securely anchored to prevent theft.

Monitors are used for:

• Highway conditions
• Water level gauge stations
• Automatic traffic recorders
• Road ice detection systems
• Meteorological information

The city of Missoula, Montana, installed two permanent PV-powered automatic traffic recorders (ATRs) within the city limits. The units record information on traffic flow rates and vehicle velocities, which then can be used in the transportation planning process. The recorded data are preserved by battery power. The battery, charged by either a 5- or 10-watt PV module, maintains 15 days of reserve power.

The PV addition to the ATRs cost $50 per installation. The cost to power the ATRs using a utility connection, including the meter, wiring, and regulator, would have been only $100 per installation, because utility power was available at the site. In addition to this cost, the local utility world have assessed the city a minimal monthly charge. Because the minimum monthly charge by the utility exceeded the ATR energy requirements, the city could not justify the cost of a utility connection and opted for PV power.

City officials are very satisfied with the operation of the PV-powered ATRs, installed in September 1992. To date, the systems have required no maintenance, and no components have failed.

Tens of thousands of photovoltaic-powered communication systems have been installed in the United States.

These systems range in size from a few watts of photovoltaic array for call-box systems to several kilowatts for micro-wave repeater stations.

 

Applications for PV-powered communication systems include:

• Emergency call boxes
• Variable message boards
• Community warning sirens
• Emergency communication systems
• Two-way radios
• Radio communications
• Mobile radio systems
• Cellular phone systems

The Illinois Department of Transportation has installed three radio transmitters powered by photovoltaics at rest areas on I-55 to provide motorists with continuous information on weather and road conditions. The radios use a special AM radio frequency. As travelers enter one of the rest areas, they are advised to turn to a certain AM channel to receive the information. The systems consist of a 100-milliwatt AM broadcast transmitter, 80 watts of photovoltaic power, and battery storage. They have been operating since April 1988 with no problems; each cost $3,280.

Orange County, California, has installed more than 1100 PV-powered call boxes along urban highways. The call boxes have several functions, including cellular phone communications, diagnostic features (e.g., battery state-of-charge, and system self-test), and providing the call box locations to a central computer. One 6.5 watt PV module charges a battery that will last through 38 sunless days when a call box is in its lowest state of readiness.

The total cost of the PV-powered call boxes was $4.5 million-57% less than the $10.5 million projected cost of a gridconnected call box system with identical capabilities. In addition PV call boxes are portable and can be moved as traffic patterns change.

There are thousands of PV-powered call boxes throughout California, and an increasing number on Washington's State Highways. Many local governments are adding 911 phones to enhance park and playground security.

The PV call-box system installation was completed in l988, and officials are satisfied with its performance. The county does, however, have a maintenance allotment of $175,000 per year, or $12.50 per month for each call box. Because of this program, few components have failed in the past 5 years.

The Washington State Department of Transportation installed this PV-powered telephone for emergency use on the east-bound side of the Evergreen Point Bridge on StateRoute 520.

A round the world, water is pumped by a variety of methods, and no single technique is suitable for the range of existing needs. Stand-alone photovoltaic systems are increasingly being used to meet the need for intermediate-sized pumping applications-those between hand pumps and large generator-powered systems. More than 21,000 photovoltaic-powered water pumps are currently operating in the United States and abroad.

The advantages of using water pumps powered by photovoltaics include low maintenance, cleanliness, ease of installation, reliability, ability to operate unattended, and the capability to be matched to water usage needs. The typical range of sizes for photovoltaic-powered pumps is a few hundred watts of array to a few kilowatts of photovoltaic collectors for larger systems.

Water pumping systems are used for:

• Median strip irrigation
• Park irrigation
• Livestock watering
• Irrigation
• Village water supplies
• Pond aeration
• Domestic use
• Water for campgrounds

Over 50,000 navigation aides have been installed world-wide. PV has become the preferred source of reliable power for navigation aids and radio equipment at thousands of sites throughout the world. For example, a 425 Watt PV array powers the navigation and radio equipment aboard a natural gas distribution platform in the Gulf of Mexico. The U.S. Coast Guard and Navy maintain thousands of navigational aids, buoys and signals throughout the continent. PV systems are economic, reliable power sources for such applications.

Each year, metal corrosion causes billions of dollars of damage to structures, pipelines -- anything made of metal and beneath the water or ground. Corrosion is a phenomenon caused when metals are exposed to electrolytes, such as in soils and water. Cathodic protection is achieved by reversing the flow of electrons. Photovoltaic systems can perform this task. The systems are quite simple in design, and most of them require less than 1 kilowatt of power. Typical applications include:

• Pipelines
• Bridges
• Buildings
• Wharves, docks, and marinas

The Las Vegas Valley Water District, in conjunction with the Bureau of Reclamation, installed two cathodic protection systems on the water pipeline leading from Lake Mead to downtown Las Vegas. The cathodic protection systems supply DC power to the steel pipes to prevent galvanic corrosion, which often occurs in unprotected pipes and metal structures. Eight PV modules supply 288 watts of DC power to six batteries in each system for 6 days of reserve power.

The cost of each PV system (including modules, batteries, controls, and installation) was $9,000. Utility service lines were only 30-60 meters (100-200 feet) away, but PV power was chosen because it produced DC electricity and, therefore, was ideally suited for cathodic protection.

Water district and Bureau of Reclamation officials have been satisfied with the operation of the PV-powered cathodic protection systems since they were installed in 1983. Representatives from each organization visit the site annually for preventive maintenance checks. No components have failed, and there has been only one case of vandalism.