COMBINATION POWER GENERATION AND BACK-UP SYSTEM
The proposal below was submitted to the Alaska Public Broadcasting Capital Grants Program.
COMBINATION POWER GENERATION AND BACK-UP SYSTEM
KSDP RADIO STATION – SAND POINT
KSDP Radio – Aleutian Peninsula Broadcasting, Inc – is an AM public radio station broadcasting from Sand Point, Alaska. It’s listenership consists of approximately 3,000 year-round residents and an additional 3,000 seasonal residents in the Aleutian communities of Sand Point, Chignik, Perryville, Port Moller, Nelson Lagoon, King Cove, Cold Bay, and False Pass. The station broadcasts 24 hours a day, providing a vital link to local, state, and world news, local weather, local and regional events, and entertainment.
The goals for this project are two-fold. The primary objective is AC power generation capacity sufficient to sustain the radio station requirements on an annualized basis. As a privately and publically funded non-profit entity, the radio station has no revenue generating capacity. Thus, there is an implied obligation for prudent and efficient management of operating costs. Electrical costs are a significant portion of the annual operating budget for the radio station and are expected to increase substantially in the future. Installation of this system will eliminate the majority of those costs for the radio station. This project will also free up capacity for the local electrical utility, deferring utility infrastructure upgrade requirements. Power generation in excess of the radio station requirements can, at the discretion of the local utility, be fed back into the Sand Point electrical grid for use by the community, further benefiting both the utility and the community. Power generation is to be achieved through the free, non-polluting, and sustainable wind energy source, supporting the ethical obligation of public radio to operate in an environmentally responsible manner as a good steward of the public trust.
The secondary objective is the incorporation of a back-up system of sufficient capacity to allow continuing, uninterrupted operation of the facility for a minimum of 24 hours in the event of a loss of electrical utility power due to either power grid malfunction, natural disaster, inclement weather, terrorist activity, etc. With this system the radio station will be in a position to provide critical community-wide communication and information dissemination.
NOAA operates from this facility, transmitting crucial weather information. Also, the threat of tsunami activity in Southwest Alaska is real. Earthquakes almost anywhere in the Pacific Ocean have the potential of generating deadly tsunami waves. The waves, varying from several inches to several feet, can devastate low-lying communities and residences. The transmitter site is above the designated tsunami impact area. KSDP radio, in conjunction with NOAA, provides a vital tsunami advisory service for the listening area. There are no television stations or other radio stations in Sand Point. Providing reliable, independent power to autonomously maintain site functionality is crucial.
The wind turbine project is to be located at the existing AM transmitter site on the eastern side of the City of Sand Point, specifically the westerly portion of Tract “G” in “The Meadows” subdivision. Site elevation is approximately 200 ft above sea level. The site is centered on a 6.49 acre parcel of ground leased by the radio station from the Shumagin Corporation. The site has good access via an all-weather road from the northwest across school district property. The parcel of ground (and site) are located on a flat meadow surrounded by gentle ridges ranging from 10 ft to 50 ft and at distances of 1,000-2,000 ft from the site. The Sand Point School is to the northwest. The north and east are lightly populated residential. There are no residences within 1,000 ft of the proposed turbine site.
The site currently consists of the 200 ft guyed lattice AM transmitter tower and an 8 ft by 10 ft enclosure housing the transmitter equipment. Both are secured in a locked, chain link fence compound. Access to the transmitter site is via an all weather road from the northwest (see photos) that is presumably only used for accessing this site. The proposed wind turbine tower location is adjacent to the access road approximately 120 ft to the northwest of the existing compound. The wind turbine power system equipment would be housed in a 6 ft by 10 ft building in the secured compound and immediately adjacent to the transmitter equipment building. The power system building would be secured to concrete blocking in a manner similar to that for the existing building. Guying for the turbine tower would be buried concrete blocks like that used for the AM tower.
Alaska Energy Authority wind resource data for Sand Point was used as the basis for the wind resource analysis. That data indicates an annual average of slightly less that 12 mph. There is no site-specific wind data. However, It is our belief that the average wind speed at the sited turbine height for this project is probably in excess of 15 mph for the following reasons:
1. The AEA data was tabulated from a MET station with a 23 ft sensor height compared to the 80 ft turbine height for this project. The AEA data is significantly impacted by ground effect.
2. The MET station used to collect that data is located at the southern end of the airport runway apron, and in a sheltered spot between the runway and a significant hill to the immediate east. The elevation is approximately 50 ft above sea level. The transmitter site is on an exposed area 200 ft above sea level.
Both the location and the sensor height tend to moderate the wind data significantly. During the site inspection we were able to conduct a rough comparison of the wind resource at the transmitter site and the airport MET station during a storm with NE winds. At the airport the winds were gusting to 20 mph. At the transmitter site, the winds were gusting to 30 mph, a 50% increase (taken with hand-held anemometer at a 5 ft height). While the variation with a NE wind is probably greater than that for north-south winds, the difference between the two sites is still expected to be significant. Since the exposure at the wind turbine site is good, particularly to the north, east, and south, an annual average of 14.6 mph (Class 5 Wind Zone) will be used here for analysis.
A 10 kW wind turbine, mounted on a 78 ft guyed pole tower, is planned for the system. The site is in a meadow surrounded by gently sloping ridges. As measured with a hand-held clinometer, the elevations on the ridges ranged from a low of 10 ft to the east to a high of 50 ft to the west. The predominant power winds are from the north and south. The ridges in those directions consist of gentle slopes averaging 40 ft, and are at least 1/4 mile distant from the tower site. It is anticipated that winds will follow the ground contour. Regardless, the 80 ft hub height for the wind turbine will place it above the ridges and in largely unobstructed air flow. Based on turbine manufacturer production data at an annual average wind speed of 14.6 mph, and discounting 10% for inverter and system losses, average monthly power production should be 1,805 kWh, or 103% of the average station power requirement.
The power system will be housed in the locked and fenced compound. The turbine tower will be located outside that compound. It is recommended that a locked gate be installed on the access road and prior to the turbine tower. This will prevent unauthorized vehicular traffic in the vicinity of the tower that could result in tower or guy anchor damage. There is some risk of injury to snow machines from guy anchors or guy wires. However, the existing AM tower has three sets of guy anchors that have been in place for years. The turbine tower guys will be marked with orange guy markers. All electrical wiring outside the compound will be underground. The turbine tower is sited far enough from the existing facility to prevent the turbine or tower coming in contact with any other equipment (including AM tower guy lines) should there be a failure that causes the tower to fall. Vandalism is always a possibility but the site is only accessed by one road and is clearly visible from the full 360 degree perimeter. There was no evidence of vandalism or theft at the existing site.
Although the site is in a meadow area, local residents reported that there is no bird nesting activity in the area and that the wind turbine should not pose a risk to birds.
The site is not (to our knowledge) in an airport flight path. Since the 78 ft turbine tower will be located only 120 ft from the existing 200 ft AM transmitter tower, it is not anticipated that a permit would be required.
As stated earlier, the closest activity is over 1,000 ft from the proposed turbine site. The maximum noise level for this turbine (including wind noise) is 59.4 db at 12 meters, diminishing thereafter. At a distance of 1,000 ft the turbine noise will be mitigated. Noise should not be an issue.
Soils & Vegetation
Research indicated that soils for the area typically consist of several inches of organic material, several feet of silty sand, and then bedrock. Examination of the site supported this. There is no permafrost in the area. Seasonal frost is estimated at three feet. The project anchoring is designed to extend below this frost line. The area is seismically active. Since the existing AM tower has withstood seismic activity for years, emulating that anchoring system for the wind turbine tower should be adequate and produce satisfactory results. The existing AM tower has successfully used concrete block tower base and guy anchors. The durability of the foundation and guy system for the existing AM transmitter tower validates the viability of a similar scenario for the wind turbine tower. The vegetation consists of grasses in the meadow and scattered scrub brush to 6 ft height on the slopes.
The average temperature ranges from a low of +20F to a high of +58F. The record temperatures are a low of -9F and a high of +78F. The precipitation average is 33 inches of rainfall and 52 inches of snowfall annually. In general the weather is mild except for wind.
Storms with winds in excess of 100 mph are possible in the area. Obviously winds of this magnitude are a concern. The wind turbine is designed to furl out of the wind to a maximum 90 degree angle and apply dynamic braking in excessive winds. The tower height for this site was selected specifically to expose the turbine to free air flow but not to the extent that it would have unrestricted exposure to excessive winds. Ground friction from the surrounding ridges should increase with wind speed and help moderate excessively high winds.
Icing of the turbine and tower structure are always a concern in Alaska. A specific question posed to residents was whether the area was subject to prolonged periods of heavy frost or ice buildup. None was reported, but short periods of ice buildup may occur periodically. Our suspicion is that the occasions when icing conditions are accompanied by calm winds are rare. The turbines are far less susceptible to ice buildup during windy conditions that tend to
help shed moisture. Icing is a potential issue that will be carefully monitored, particularly during the first winter.
Since the site is leased from Shumagin Corporation, the lease arrangements were reviewed. The lease was entered into on Sept 1, 1993. It has a 20 year term so will expire in 2013 with no renewal provision specified in the agreement. The fair market basis of the lease was identified as $2,700.00 (not clear if per month or year). An annual lease fee of $500 is paid, with the balance considered a charitable contribution. The radio station is currently negotiating for the purchase of the property. The lease Use of Premises clause allows “such other improvements as are reasonably necessary to the operation of a non-profit radio station” so the installation of a power and backup system for the transmitter facility are clearly authorized by the lease and will not require prior approval.
Ordinances or Covenants
Station general manager Kels Hetherington indicated that there are no City ordinances or covenants that would impact the wind turbine system. The only lease restriction is avoidance of electronic interference with the surrounding residences. This system should generate no electronic interference.
A review of the radio station utility records for 2006-2007 (and substantiated by January, 2008 records) indicate that the power consumption is fairly stable throughout the year – ranging from 1400-1900 kWh per month (1755 kWh average). This equates to a daily power consumption average of 58.5 kWh. The power costs are currently $0.53/kWh, resulting in an annual power cost of $11,162.00. These costs are for the transmitter site only. The radio station offices are located in Sand Point at the City office building. It is my understanding that utility costs for the offices are donated by the City.
The transmitter site is presently powered by an underground 100A 120/240VAC service connection with an electromechanical meter. The service is located on the northwest exterior of the transmitter building, where it penetrates the wall to a Square D 100A surface mounted load center with main breaker. Wind turbine system integration would be achieved by re-routing power from the load side of the exterior service disconnect to the inverter set, and then returning from the inverter set to the building load center main breaker.
Monitoring and coordination of building power will then be handled by a pair of Xantrex model XW6048 inverters – prioritizing the use of wind turbine system power to satisfy building requirements, while utilizing grid power for peak load shaving. A loss of grid power would result in the immediate shift of the entire building electrical load to inverted power. During normal operation, grid power is paralleled by inverted power and monitored on a half-cycle interval. If grid power quality exceeds specification limits or is interrupted, building power is immediately shifted to inverted power until grid power quality has been restored. Inverted power is full sine wave with the following specifications:
AC output voltage limits
Line to neutral – 120 VAC +/- 3%
Line to line – 240 VAC +/- 3%
AC output frequency – 60.0 Hz +/- 0.1 Hz
Total harmonic distortion – <5%
Inverter capacity is 12,000 watts continuous with a 24,000 watt 10 second surge. Pass through capacity is 120A at 240VAC. The inverter system contains bypass breakers that allow the inverter system to be taken off line for maintenance or repair without interruption of power. The inverters are UL1741 compliant and can be easily programmed for grid-sell of excess power.
Daily station transmitter power consumption averages 58.5 kWh. A system battery reserve of 2000 amp hours (at the 20 hour rate) at 48 VDC (nominal) – or 96 kWh of battery storage capacity – is anticipated. The battery bank can support the entire facility electrical load for 24 hours to a 61% depth of discharge. Deep cycle, AGM non-spillable batteries requiring minimal maintenance are planned for the system.
Wind 10 kW grid-connect turbine $34,800
Includes the turbine, 78 ft guyed pole tower,
rectifiers, and all electrical.
Enclosure 6 ft x 10 ft fiberglass building for the battery bank $ 6,600
and power system.
Battery Deep cycle AGM non-spillable $26,000
2000 AH at 48 VDC, cabling, and all electrical.
Inverter (2) Xantrex XW6048 120/240 Sine wave inverters $12,900
Includes AC/DC distribution panel, system control
software, and electrical.
System Installation & commissioning – $38,400
Includes materials and labor,
equipment and transportation.
Does not include permitting or regulatory costs.
Total System Cost $118,700
Two project feasibility analyses are attached to this quotation. They are both based on a fixed 2.0% annual O&M cost, a 5% annual electric rate increase, and a 25 year system life. One shows a traditional payback based on the total project cost. The second shows the cash flow impact to the radio station based on a $100,000 grant and a radio station contribution for the remaining $18,700.00. As can be seen from the cash flow projection, the benefit to the radio station cash flow is significant after the second year.
Warranty: The system comes with a one year parts & labor only warranty and a five year parts only warranty.