Appropriate Energy Inc-Remote Area Power Generation-Report

Appropriate Energy SLG Performance Report
Dean Davis, Craig Hansen

The Appropriate Energy SLG wind turbine has been in operation for approximately 3.5 years at the Spanish Fork Test Site. The testing, including operation, data collection, and maintenance has been conducted by Windward Engineering L.L.C. of Salt Lake City, Utah, USA for the entire period. This report is a brief summary of the testing project.

The Appropriate Energy SLG (grid connected) wind turbine was installed at the Spanish Fork Test Site at the end of 1995. Testing began early in 1996. Since May ¹of 1996 the wind turbine has supplied the local utility (Utah Municipal Power Authorities (UMPA)) with 152189 kWhrs of energy. This is an average of 132 kWhrs/day. This number is considerably lower than the potential energy capture for the SLG at the Spanish Fork Test Site. This is because much of the preliminary operation of this turbine was for prototype debugging and testing. This involved significant down time for turbine improvements, controller modifications, instrumentation calibration and data collection, as well as for maintenance. For example, we had the turbine out of operation for approximately 6 months (winter of 97-98) as we waited for a replacement compressor part and as we debugged an electrical instrumentation problem. When the turbine is allowed to operate normally it averages approximately 220 kWhrs/day. Figure 1 shows the cumulative energy metered over the three and a half years of testing.

Figure 1. Appropriate Energy SLG energy production summary.

The test site is located in Utah Valley, approximately 55 miles south of Salt Lake City and 5 miles east of the town of Spanish Fork. The site is situated near the mouth of Spanish Fork Canyon. The site elevation is approximately 5,200 feet (1585 m) above sea-level. Spanish Fork Canyon is bordered by peaks approximately 10,000 feet (3048 m) in elevation, so there is an abrupt rise in the terrain about one mile east of the test site. The high elevation air density at the site is lower than sea-level values, and the energy production is reduced as a result.

The winds at the test site result from drainage flow down Spanish Fork Canyon. On a typical day, the winds begin blowing as the sun sets and the canyon walls begin to cool. The winds increase throughout the evening and night, generally peaking between midnight and 5 am. Typically the early morning winds will be between 12 and 15 m/s. After sunrise the winds begin to diminish and are generally calm by 10 am to noon. During the daytime the winds will shift to blow up the canyon, but the wind speed is usually only a few meters per second. Storms in the area can break this normal cycle of events and result in either calm or strong winds from other directions.

The weather at the site is typical of northern Utah valley locations. The climate is generally very dry, with approximately 15 inches (38 cm) of precipitation per year. Most of this falls as snow between December and March. The maximum snow depth we have experienced at the site in four winters is approximately 20 inches (51cm). The ground is free of snow much of the winter, but we have seen extended periods with some snow accumulation. The lowest temperature likely at the site is approximately -10F (-23C). Most often the low temperature during winter months is in the 20’s (-7 to -1C). In the four winters of testing we have not experienced icing conditions, but freezing rain and icing accumulation have been observed in the area infrequently in the past. Summers are very hot and dry. The high temperature most days is in the 90’s (32 to 38C), with 100-105F (38-40C) a few times each summer. Humidity is low, and the corrosion environment is quite benign. Thunderstorms occur throughout the spring and summer seasons, generating very high, turbulent winds along with the possibility of lightning strikes.

The Spanish Fork test site not only sees good energy producing winds it also has its share of extreme wind conditions. When thunderstorms build in the mountains it is not uncommon to see winds gusting above 25m/s. These gusts can be associated with large wind direction changes as well. Hearsay suggests that these winds were the winds that continuously damaged, and eventually caused the removal of the Jacobs test turbine which was installed by the city of Spanish Fork.

The high winds are generated from strong low pressure systems moving into the area. We have seen winds associated with these weather conditions above 32 m/s and the town 10 miles to the north measured 41 m/s during this same event. From our limited experience at the test site we would guess that we could expect winds above 35 m/s once or twice a year.

Figure 2 shows winds collected during a thunderstorm a few years ago. The last peak has been detailed in Figure 3. Also plotted on Figure 3 is the IEC extreme coherent gust. We can see that the wind measured in SF is almost equivalent to the IEC wind condition.

Figure 2: Plot of winds during a period where there were thunderstorms in the mountains east of the test site (June 10, 1996). The large spikes in wind speed were typically associated with direction changes of approximately 90°.

Figure 3: Last wind speed spike from Figure 2 detailed. We can see that the measured wind is very close to an IEC extreme coherent gust.

The Appropriate Energy SLG grid connected wind turbine has been in operation for ~3.5 years at the Spanish Fork Test Site. Much of the early operation of the turbine was directed towards testing and data collection of loads and performance of the wind turbine. This testing has resulted in validation of the computer modeling used in the design. The testing has also resulted in numerous improvements to the turbine operation. The turbine has produced a total of 152189 kWhrs since May of 1996.

[1] UMPA did not install the watt meter until May of 1996. As a result the first 4 months of energy production were not recorded.