Small Wind General Information Date: July 2006

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1 Small Wind General Information Date: July 2006 Wind Energy Wind generators produce power by converting mechanical wind energy, captured by the blades, to electricity through its generator. Most of today s wind generators have a horizontal axis design with a tail that helps it track the direction of the wind flow, which keeps the blades steered into the wind for maximum power. Wind generators also have some kind of mechanism to govern (slow down) the blade speed in high winds. Otherwise, the wind generator could heat up and ruin internal parts if the wind speed gets high enough. Wind generators for residential use range in size from about 1000 to 40,000 Most have a startup speed of about 7mph, but typically don t start generating useful power until about 9 or 10 mph. Each manufacturer supplies an energy output chart that lists the expected energy output in kilowatt-hours at a given average wind speed. Wind generator blade diameters typically range from about 10 to 23 feet. Wind generators should be mounted above any obstacles for best results. This is generally assumed to be at least 30 feet above any structures within about 500 feet of the tower base. The higher the better, since airflow is typically faster and less turbulent at higher altitudes, and the power output is proportional to the wind velocity cubed {P= (1/2)*d*A*v 3 where P = power, d = density of air, A = area swept by the blades, and v = velocity}. There are 3 main types of towers used for wind generators free standing, tilt-up tower, and a guyed tower (see diagram below). The free-standing tower may require some heavy-duty equipment to erect it and place the wind generator on top. A guyed tower may also require some heavy-duty equipment depending on the height of the tower and size of the wind generator. The tilt-up tower can be raised and lowered to place the generator on the tower and also for maintenance (This is typically done with a pulley system and a winch or a vehicle). Required radius of the anchors for the guyed and tiltup towers is about ½ the tower height.

2 Wind Information System A wind utility intertie system uses the electric power from the wind generator and distributes it to the dwelling and the electric utility. When excess power is available from the wind system it is sent back out on the utility lines for use by the utility. This excess power is metered and sold back to the utility at a rate determined by a contract between the utility and the customer. If the dwelling needs more power than the wind is producing at the time, the customer is provided power from the utility. Advantages of these systems are a reduced electric bill and clean energy, which help the environment. A disadvantage of this type of system occurs during a utility power outage, where the system must automatically shut down. This is necessary so no power will be fed out on the utility lines, which could endanger a worker trying to fix the problem. This leaves the dwelling without power. Main Components The main components of a typical system are shown in the one-line diagram below (some systems may vary see the electric utility cogeneration documents for specific requirements): Wind Generator The wind generator output is dependent on the blade size, velocity of the wind, air density, and the manufacturer. The specification sheet should give expected energy output based on average wind speeds. The wind speed of the location can be estimated from wind maps, local airport wind speed data, local observations of the surrounding tree growth, or by using a anemometer to measure wind speed for a given time frame. Controller Wind generator controllers are generally supplied with the wind generator. If the controller is not supplied with the wind generator, then a diversion controller and diversion load may be required. Some controllers can feed directly to the utility power through the AC disconnect and wind meter if they have sufficient safety control features required by the utility (see Inverter section below for description of safety features). Inverter The inverter converts the DC power from the wind generator controller to AC power, and synchronizes the output with the utility. The inverter must be rated to handle the maximum power output from the wind generator. The inverter has to be able to meet the specifications and limits set by the contract between the utility and the customer. This includes, but is not limited to, acceptable distortion of waveform, over/under frequency, over/under voltage, and automatic shutdown during a power outage. DC and AC Disconnects The DC disconnect allows the wind generator to be isolated from the inverter and other parts of the system for maintenance or when upgrading the system. Care must be taken to apply some kind of brake on the wind generator so it does not free spin at this time. The AC disconnect provides the utility with an emergency switch to shut down the

3 system. The AC disconnect provides added protection for utility line workers and should be located in a location accessible to the utility workers, next to the meter socket. Utility Meters Some of the power generated by the wind generator is used by the dwelling and some is sold back to the utility. The utility meter is the service meter that is already in place at the dwelling. For the customer to be correctly credited for excess wind power the standard utility meter needs to be replaced with a bi-directional meter by the utility. Many utilities utilize a special bi-directional meter, that records power flowing in both directions. Installation Process The following is a general guide to the process of installing a wind utility intertie system. Local and National codes should be followed for safety and insurance reasons. 1. Check with federal, state, county, township, and city on zoning restrictions for towers in your location. Also check with your neighbor. Wind generators may not be allowed, or special permits may be required. 2. A complete evaluation of your location will help determine the feasibility of doing this type of system. The site should have enough room for the type of tower (consider guy wire radius), and should be able to be at least 30 feet above any structures within about 500 feet of the tower base. Evaluations are usually available for a nominal fee from a qualified contractor. 3. Evaluate the feasibility by weighing the advantages and disadvantages of installing a wind generator intertie system. Consider environmental, maintenance, and monetary issues before deciding. 4. Make sure your insurance homeowner s policy will cover the new equipment. Upgrade if necessary when the system is completed. 5. Contact your electric utility to receive the proper documentation and contracts for approval of the system. Submit forms and any additional specifications to the utility for approval. Most wind contractors can help the homeowner complete this step. 6. It is recommended to call a wind generator contractor to help design and install the system. 7. Obtain the proper permit(s) from the building department at the local city or town hall. This is typically an electrical permit. Fees will vary depending on location and size of the system. If working with a licensed electrical or wind generator contractor, they should be able to obtain these permits for the installation. 8. Discuss the system with the local utility and electrical inspector for any special requirements. The inverter must meet utility specifications for the power it sells back to the utility. See Article 705 of the National Electric Code (NEC) book for interconnect requirements. 9. Make sure all equipment is labeled with an approval from a testing laboratory that is acceptable by the State Board of Electricity. UL 1741 label is typically required for the inverter by the utility. This would include UL, ETL, CSA call the State Board of

4 Electricity for a complete list of approved testing facilities. If any equipment is not labeled, then it is up to the local inspector whether it can be used in the system. If there are any questions work with the inspector early on in the process before making major purchases. See Article of the NEC. 10. The equipment can then be purchased and installed to the specifications of the utility, NEC, and inspector. After the installation has been approved, the system can be put online. Typical Costs Typical costs of these systems consist of the main components as described above, materials for footings, wire, conduit, connectors, permits, labor, and other miscellaneous electrical parts. The following prices are general numbers based on the latest pricing information as of the date of this brochure. The following pricing should NOT be considered as a quote (200) Wind generators generally cost approximately $1600 for a 1000 Watt wind generator, $5000 for a 3000 Watt wind generator, to $17,000 for a 10,000 Watt wind generator. Typical wind utility intertie systems would be in the 3000 to 10,000 Watt range. Note: The wattage ratings of wind generators are given at a specific wind speed this is usually in the 27 to 30 mph range. The tower kits can range from $1000 to $8000 depending on the height of the tower and the weight and vertical thrust of the wind generator. Anchors, footings, concrete, miscellaneous parts, and equipment rental could range from $1000 to $4000. Utility intertie inverters range from $1600 to $3200 for a single inverter from 2500 Watts to 5500 Watts, respectively. Multiple inverters can be used to increase system capacity. The disconnects, batteries, wind meter, and other miscellaneous electrical parts should be in the $1000 to $4000 range, and labor would be in the $3000 to $6000 range for typical installations. This gives a system total cost range of about $9,200 to $45,400 for a complete installation. Economic Analysis An economic analysis needs to consider present and future utility energy prices, interest on loans to purchase the system, any tax credits available, the energy output of the system, system maintenance costs, and the price of the system itself. A simplified analysis based on present and future energy prices, output of system, and cost of system is shown here as an example: Wattage rating of wind generator at 28mph: 3000 Watts Energy output per 12mph average wind speed (taken from manufacturers spec sheet): 600 KWhr/month System Cost: $19,000 Utility Energy Cost: $0.075 per kw-hr 600 KWhr/month output would be 7200 $0.075/KWhr equals $540/per year savings. Assuming a rise in energy costs of 5% per year, the payback period comes to about a 21-year payback. A utility energy cost of $0.12/KW-hr and an increase of 3% per year would result in a payback period of about 18 years. A more extensive economic analysis should be done for specific situations.

5 Maintenance Modern wind generators have relatively low maintenance compared to the generators of 20 years ago. Some areas to consider for maintenance are as follows: A visual check for any unusual vibrations or noises can help detect potential problems before they get serious. Tightening loose bolts on the wind generator, tower, or guy wires may help solve the problem. Most manufacturers recommend checking the wind generator up close about every 6 months for cracked blades or loose fasteners. This can be done on the ground with a tilt-up tower. With a free standing or guyed tower, it may have to be climbed or may need some heavy duty lift equipment to get to the wind generator for inspection. We strongly suggest hiring an experienced wind generator person, or renting the proper equipment if climbing a tower is required. Check wind generator meter output occasionally during a windy period to make sure the system is generating power. If power output is lower than it should be, check for blown fuses, circuit breakers, loose or corroded wiring connections, or a damaged lightning surge protector. Remember to put the brake on the wind generator and have all power sources disconnected before checking or replacing equipment. If unsure of safety procedures, then have a qualified service person check the system. Equipment problems are typically covered by the installer and/or the manufacturers warranty for a specified time period. Save all documents on the system for future reference, and refer to the equipment owner manuals for all safety precautions and maintenance instructions.