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Manzanita Hybrid Power System Project.doc

Final Report Title Page

Project Title: Manzanita Hybrid Power System Project

DOE Award Number: DE-FC36-99R810677

Period Covered by Report: September 30, 1999 to March 31, 2005

Document Title: Manzanita Hybrid Power System Project - Final Report

Recipient Organization: Manzanita Band of the Kumeyaay Nation

Angela Santos, Tribal Council

P.O. Box 1302, Boulevard, CA 91905

(619) 766 4930; fax (619) 766 4957

numberz4me@aol.com

EXECUTIVE SUMMARY

The Manzanita Hybrid System Project was funded under the U.S. Department of

Energy's Tribal Energy Program to provide electricity to one of the tribal community

buildings. The project began September 30, 1999 and was completed March 31, 2005.

The hybrid renewable energy system was designed and the equipment supplied by

Northern Power Systems, Inc, an engineering company with expertise in hybrid system

design and development. Personnel of the National Renewable Energy Laboratory

provided technical assistance in system design, and continued to provide technical

assistance in system monitoring.

This final project report provides a technical accounting of the activities performed, and

a description of the results achieved, including lessons learned from the Manzanita

Hybrid System Project. This report contains the following sections:

• Executive Summary

• Project Overview

• Objectives

• Description of Activities Performed

• Conclusions, Recommendations, and Lessons Learned

• Appendix

Project Overview

The Manzanita Indian Reservation is located in southeastern San Diego County,

California. The Tribe has long recognized that the Reservation has an abundant wind

resource that could be commercially utilized to its benefit, and in 1995 the Tribe

established the Manzanita Renewable Energy Office. Through the U.S. Department of

Energy's Tribal Energy Program the Band received funds to install a hybrid renewable

power system to provide electricity to one of the tribal community buildings, the

Manzanita Activities Center (MAC building).

The project began September 30, 1999 and was completed March 31, 2005. The

system was designed and the equipment supplied by Northern Power Systems, Inc, an

engineering company with expertise in renewable hybrid system design and

development. Personnel of the National Renewable Energy Laboratory provided

technical assistance in system design, and continued to provide technical assistance in

system monitoring.

The grid-connected renewable hybrid wind/photovoltaic system provides a

demonstration of a solar/wind energy hybrid power-generating project on Manzanita

Tribal land. During the system design phase, the National Renewable Energy Lab

estimated that the wind turbine is expected to produce 10,000-kilowatt hours per year

and the solar array 2,000-kilowatt hours per year. The hybrid system was designed to

provide approximately 80 percent of the electricity used annually in the MAC building.

The project proposed to demonstrate that this kind of a system design would provide

highly reliable renewable power for community uses.

- System Description

The grid-connected renewable energy system is a 10 kW Bergey wind turbine and a 1.2

kW Siemens photovoltaic array, which provides electricity to the MAC building. Although

the power system can be configured for stand-alone operation, the best use of it on the

Manzanita Reservation is in a grid-connected mode. For stand-alone applications at

other sites, the design of this hybrid power system will allow a standby generator to be

added to provide on-demand power in periods of diminished renewable resources or

increased electrical loads.

The hybrid system is centrally located for monitoring and visibility, and provides power

for established community needs. The overall system rating is 10kW, allowing it to meet

the criteria for net metering requirements that existed in California when the system was

proposed in 1999. See Figure 1. for a Schematic of the hybrid system.

As in many rugged and rural locations, the Manzanita Reservation occasionally

loses grid power, particularly due to high winds in winter storms. A battery bank

provides energy storage allowing several days of independent operation in the event of

a power failure or to enhance power quality in brown out conditions. Tests of grid-

independent operation were conducted during the project period.

Figure 1.

Schematic of the system by NREL consultant, Greg Barker of Mountain Energy

Partnership.

The hybrid system operates at a nominal voltage of 48 VDC and provides 120/240 VAC

power for user applications through an inverter. DC power can be provided directly for

equipment such as telecommunications radios and repeaters that operate at DC

voltages.

The major components of the hybrid system include:

• 7.5kW Bergey wind turbine with 80-ft guyed-tower. Includes turbine charge

controller.

• 1.2 Siemens PV array consisting of sixteen 75W panels, 4 panels per string.

• 875 AH Deka Unigy II deep discharge, maintenance-free, battery modules.

• 8000VA Inverter bank consisting of 2 Trace SW4048 modules.

• DC power center.

• NRG anemometer

• Support frame for PV array. Adjustable array angle.

• All system wiring and protective devices including turbine disconnect and utility

interconnect panel.

Project Objectives

The primary objectives of this project were to design, install, maintain, and

monitor a renewable hybrid power system, with the intention of demonstrating that a

system of this type can be used to provide highly reliable renewable power for

community uses.

The modular system was to be designed to be versatile, in that it could be adapted for

either stand-alone power applications or connected to the utility grid. Designated

Manzanita tribal technicians were to carry out the service and maintenance functions. In

addition, ongoing education was to be held for tribal members seeking to increase their

technical knowledge related to the wind and solar energy industries.

Description of Activities Performed

The Manzanita Hybrid System project began September 30, 1999 and was

completed March 31, 2005. The activities consisted of project design, installation,

monitoring, maintenance, and education/outreach, as follows:

- System Design

The system was designed and equipment supplied by Northern Power Systems, Inc.

(NPS), an engineering-oriented company that specializes in hybrid design solutions

integrating renewable and conventional energy resources. In addition, personnel of the

National Renewable Energy Laboratory provided technical assistance in system design.

While NPS was involved in the design phase, Manzanita project staff changed out the

old lighting fixtures in to Manzanita Activities Center building since lighting is the single

largest end use for electricity; installed in all rooms were the more energy-efficient

fluorescent fixtures to ensure that building would make the best use of the electricity to

be produced by the renewable hybrid system.

- System Installation

After the design work had been completed by Northern Power Systems, the project was

ready for installation. The site on the hill above the MAC building had been selected as

the best location for the Bergey wind turbine. The hill was well-exposed ground without

trees and located approximately 450 feet uphill from the MAC building.

Mike Bergey of Bergey WindPower, Inc. recommended an installation contractor located

in southern California. In late April of 2000, the concrete pads for the wind tower were

formed up and the cement was poured. The work crew consisted of five to six people,

the Tribal work crew, the contractor Joe Guasti, and his assistant. The site was cleared

of brush and leveled with a small bulldozer. 450 feet of trenching downhill to the

Manzanita Activities Center building was accomplished using a trench-digging machine.

In late May, the crew installed the turbine. There was a crane on-site for one-half day to

lift the turbine into place on top of the guyed-tower. During this week, the crew also

mounted and connected the solar system on the roof of the MAC building. Batteries and

other balance of system components were installed in a room in the MAC building

designated as “The Battery Room.”

During the week of August 20th, the crew spent two days installing the project

anemometer using a guyed tower. This was accomplished using a gin pole, without

heavy equipment. The turbine and anemometer guyed-tower pads comprise

approximately one acre.

- System Monitoring

Personnel of the National Renewable Energy Laboratory provided technical assistance

in system design, and continued to provide technical assistance in system monitoring.

On an ongoing basis, the designated technician, Tribal member David Thompson,

collected the chips from the NRG met tower and sent them to NREL for processing.

In 2002 and 2003 we had discussions with NREL and it was determined that we needed

more detailed performance records. We decided that what was missing from the data

acquisition system was a direct measurement of the amount of energy delivered by the

renewable energy systems (PV and Wind). Also missing was a fail-safe method of data

collection and storage.

In early 2004 NREL sent Greg Barker of Mountain Energy Partnership to consult on

these issues. He installed two pulse-initiating kilowatt-hour meters on the AC lines

connecting the electrical grid to the inverters. With these new measurements and the

existing measurements, the total energy delivered by the renewable energy systems

could be directly measured. David Thompson worked with Greg Barker to collect the

data. Barker filed monthly reports with NREL.

In addition, NREL used the project data to validate the potential performance of a hybrid

project. See the Appendix for the NREL report, “Annual Performance Prediction,” by

NREL consultant, Greg Barker of Mountain Energy Partnership.

- System Maintenance

Northern Power Systems designed the hybrid system so that maintenance requirements

would be very limited. David Thompson, the project’s technicians performed the

maintenance functions. The batteries were the primary maintenance concern and

maintenance was relatively straightforward, involving checking battery terminals for

corrosion, checking the water level in the batteries with a hydrometer, and equalizing

the batteries when necessary. Thompson also cleaned the PV array on an ongoing

basis. In addition, Thompson maintained an record of the local utility meter readings.

- Education and Outreach

The Manzanita Renewable Energy Office project staff coordinated education and

outreach during the project period. The official dedication of the hybrid system in

December of 2000 was an opportunity for all Manzanita Tribal members, other

local Tribes, and surrounding community members to see the system and learn

about renewable energy. Representatives from DOE and local agencies also

attended the event.

Through the project period, the Manzanita Renewables Committee (MRC) met to

discuss project issues. The MRC and other Manzanita Tribal members met with

technical consultants from NREL, Charles Newcomb and Greg Barker, when

they visited Manzanita. When Pieter Huebner from Bergey WindPower, came to

trouble-shoot the system, project staff organized training sessions for the MRC

and other Manzanita Tribal members to review and discuss project operations

and maintenance.

There were numerous other visits by interested local people, including

schoolchildren and Kiwanis Club members, to see the hybrid system. Children of

neighboring Kumeyaay Tribes and other Tribes visited the site, to increase their

knowledge of, and appreciation for, renewable energy as a clean alternative to

fossil-generated electricity.

Conclusions, Recommendations, and Lessons Learned Throughout the Manzanita Hybrid Power System Project, there was an opportunity to

gain first hand experience with a Tribal resource that could benefit the community. The

project has also provided a significant learning experience in community project

development.

- System Design

As mentioned above, the system was designed and equipment supplied by Northern

Power Systems, Inc. (NPS), an engineering-oriented company that specializes in hybrid

design solutions integrating renewable and conventional energy resources.

The lesson learned was that even thought NPS was a highly skilled and reliable

organization; they were located too far away to interact successfully with Manzanita.

The key is to work with local consultants if at all possible, or at least consultants that are

accessible, who can provide local services without high travel expenses.

- System Installation

Utilizing the installation contractor recommended by Bergey, the Manzanita work crew

cleared and leveled the site with a small bulldozer; formed and poured the concrete

pads for the wind tower; trenched 450 feet of downhill for the wiring using a trench-

digging machine; installed the turbine, working with a crane-operator; mounted and

connected the solar system; and installed the batteries and other balance of system

components.

The lessons learned during this process were gleaned from the hands-on experiences

of installing the hybrid system; tribal members not only gained an awareness of factors

related to the use of wind and sun to produce power, but also the practical training

needed to install and operate a small hybrid system of this type.

- System Monitoring

As mentioned, Personnel of the National Renewable Energy Laboratory provided

technical assistance in system design, and continued to provide technical assistance in

system monitoring. By working with personnel of the National Renewable Energy

Laboratory, project technician David Thompson received the benefit of technical training

in resource documentation.

In addition, NREL used the project data to validate the potential performance of a

community renewable energy project, which may be a useful model for other Tribes to

replicate, who are considering wind as a community development strategy. See the

Appendix for the NREL report, “Annual Performance Prediction,” by NREL consultant,

Greg Barker of Mountain Energy Partnership.

- System Maintenance

As mentioned, Northern Power Systems designed the hybrid system so that

maintenance requirements would ideally be very limited. David Thompson, the project’s

technician performed the maintenance functions, which were relatively straightforward

and primarily involved checking and maintaining the batteries on a regular basis.

However, we encountered several technical system problems that required calling in

either an NREL technical consultant or a representative from Bergey WindPower, the

turbine manufacturer. Although a great deal was learned from these visits by technical

consultants, regarding system trouble-shooting and maintenance, the basic situation

remains the same. The Tribe has no on-site staff trained in the complexities of the

system. If something fails, project staff is trained in basic safety procedures to shutdown

the system and switch to grid-power; but from that point outside technical expertise

needs to be utilized to diagnose and fix the system. The uncertainly of the cost to

maintain the system after the grant period and into the future poses a dilemma for the

Tribe. The MAC building is used for multiple activities nearly every day. The hybrid

system is hard-wired into this building and when there is a problem, it affects everyone.

We would like to say that the system is working as designed and providing 80 percent of the

building electrical needs as originally projected by NREL, but whenever there is a problem, the

system is down, and it takes some time to diagnose and fix the problem. When the system is

working as designed and the winter winds are high, the renewable hybrid system provides

nearly all of the power used by the Manzanita Activities Center building.

APPENDIX Annual Performance Prediction

Manzanita Tribe Activities Center Hybrid System Boulevard, California

April 14, 2005

Submitted as Deliverable for

Subcontract # ACX-4-44403-01

Prime Contract # DE-AC36-99GO10337

Greg Barker Mountai nership

under

n Energy Part

1. Introduction Although the performance of PV-Wind hybrid system at the Manzanita Activities Center has been monitored for about a year, its performance does not necessarily represent the performance over a typical year, as weather patterns during the monitoring period were not necessarily typical. It is desirable, therefore, to predict what the performance of the system would be under typical weather conditions. We have made this prediction by using a computer simulation model driven by TMY (Typical Meteorological Year) weather data for a site close to the actual site. In this case the TMY site closest in location and altitude is for Dagget, CA. 2. Comparison of Daggett, CA (TMY site) to Boulevard, CA (actual site) The three weather components which significantly affect the hybrid system are dry bulb ambient temperature (influences PV temperature), solar radiation (influences PV temperature and PV output), and wind speed (influences PV temperature and wind turbine output). In Figures 1, 2, and 3 these quantities are compared on a monthly and annual basis. In Table 1 are shown the geographic location statistics. Table 1. Geographic Location Statistics Boulevard, CA

(actual location) Daggett, CA (TMY site)

Latitude (deg) 32.75 34.87 Longitude (deg) 116.36 116.78 Elevation (m) 1280 588 Climate Type High Desert High Desert From Figure 1 we can see that the dry bulb temperature at Dagget follows a similar trend as the measured dry bulb temperature at Boulevard, but is on an annual averaged basis 5.3 oC higher than Boulevard. Since Boulevard is at an elevation 692 m higher than Dagget, this offset is to be expected. Applying the rule-of-thumb of 6.5 oC temperature drop per 1000 m elevation rise (1), the Dagget dry bulb temperatures can be decreased by 6.5 X 692/1000 = 4.5 oC to account for the difference in elevation. There is no particular reason to think that the solar radiation in Boulevard is significantly different from that at Dagget, and Figure 2 seems to imply that the measured period was not far from typical insolation levels. The seasonal wind patterns shown in Figure 3 are quite different between our measured period in Boulevard and the typical patterns in Dagget, although the annual average wind speeds are similar. Since wind patterns can be a fairly localized effect, we have opted to use the measured wind speeds rather than the typical wind speeds at Dagget for our analysis. Ambient Temperature

20

25

30

35

s C

TMY

TMY, correctedfor elevation

Measured

19.7

14.4

Annual Average

15.2

Collector-Plane Irradiance

0

100

200

300

400

500

600

700

800

900

1000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kJ/m

2 per

mon

th

TMY

Measured

8136

7808

Annual Total

Fig. 2 Comparison of average collector-plane insolation between the Dagget, CA TMY site and our measured insolation in boulevard, CA.

Wind Speed

0

1

2

3

4

5

6

7

8

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

m/s

ec

TMY

Measured

4.9

5.0

Annual Average

Fig. 3 Comparison of monthly average wind speeds for the Dagget, CA TMY site and the measured wind speeds at the Boulevard, CA site. Monthly distribution is quite different, but annual average is very similar.

3. Prediction of Annual Performance of PV Array As noted throughout the monitoring period, the PV array has consistently generated almost a factor of two less energy than should be expected. Lacking further information, we have made the assumption the array will continue to perform as it has for the last year. A model was developed to estimate efficiency as a function of the driving weather parameters Tamb (ambient dry-bulb temperature), Ic (collector-plane insolation), and W (wind speed), with a few basic assumptions: hw=c0+c1W (Eq. 1) where: hw = heat transfer coefficient due to wind c0 = empirical constant c1 = empirical constant η = η0(1+β(Tc-Tc0)) (Eq. 2) where: η = array efficiency η0 = array efficiency at STC (constant) β = temperature coefficient of efficiency (constant)

Tc = cell temperature Tc0 = cell temperature at STC (constant) hA(Tc-Ta)=αIc-ηIc (energy balance) (Eq. 3) where: A = array effective heat loss area (constant) α = solar absorptance of PV array (constant) Combining Equations 1, 2, and 3, we arrive at the equation form: η = (Ic+a1+a2Ta+a3W+a4TaW)/(a5+a6Ic+a7W) (Eq. 4) where: a1,a2,a3,a4,a5,a6,a7 are empirically-derived constants. Using a non-linear numerical regression routine, we fit the year’s-worth of measured hourly data to Equation 4 to derive the constants a1-a7, and used this equation to model the performance of the PV array driven by Daggett, CA TMY weather data. In Figure 4 we show a comparison of the measured and modeled PV power output. A perfect fit would show up as a single line; our fit has an RMS error of 19 Watts.

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

Measured PV Power (kW)

Pred

icte

d PV

Pow

er (k

W)

Fig. 4 Predicted PV power output versus measured. A perfectly correlated model would produce a single straight line with a slope of 45 degrees.

The wind turbine, as noted in previous reports, appears to have undergone some sort of drop in efficiency after October 18, 2004. Figure 5 shows the power output as a function of hourly-averaged wind speed, with the two periods before and after Oct. 18 showing up as two distinctly different curves. Recently it was discovered that the wind turbine had been damaged by vandalism, and it is expected that the wind turbine will be repaired so that it operates as it had

A fourth-order polyn

before October 18.

wt = b1W+b2W +b3W +b4W (Eq. 5)

here:

4

Figure 6 the goodness-of-fit of Equation 5 is shown. The fit has an RMS error of 455 watts.

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0

Wind Sped (m/sec)

Pow

er fr

om W

ind

turb

ine

(kW

)

Before Oct 18 2004After Oct 18 2004

Fig. 5 Wind turbine power output versus hourly-averaged wind speed. Vandalism to the wind turbine appears to be the cause of the drop in efficiency after about October 18, 2004.

omial fit was made to the data before Oct. 18 of the form:

2 3 4P wPwt = power output of wind turbine b1-b = constants In

Measured vs Model(before Oct. 18, 2004)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8

Measured Wind Turbine Power (kW)

Pred

icte

d W

ind

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ine

Pow

er (k

W)

.0

0

500

1000

1500

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2500

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kWh

Wind TurbinePhotovoltaics

Fig. 6 Comparison of model versus measurement for the wind turbine power output before Oct. 18, 2004, when the turbine was damaged due to vandalism.

Fig. 7 Monthly DC energy production predicted for a typical year.

Using Equations 4 and 5 to model the power output of the PV array and wind turbine respectively, and driven by Dagget, CA TMY data modified for altitude and wind patterns, we have estimated monthly DC energy production as shown in Figure 7. Applying an inverter efficiency curve on an hourly basis, we arrive at the estimated monthly AC energy delivered shown in Figure 8.

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kWh

Fig. 8 Estimated monthly AC energy delivery from PV array and wind turbine.

Table 2. Summary of Energy Production, Predicted for Typical Year DC from

PV (kWh)

DC from Wind Turbine (kWh)

DC Total (kWh)

AC Total (kWh)

January 76.6 1397.4 1463.4 1343.6February 82.8 1039.9 1098.7 1008.0March 121.0 740.1 863.4 797.2April 143.1 626.6 715.6 644.6May 154.9 824.4 983.6 909.2June 156.5 399.2 559.1 515.7July 156.3 246.2 396.9 368.9August 145.2 247.6 384.8 356.4September 125.6 647.8 778.8 715.5

October 105.6 1018.0 1116.1 1020.5November 78.9 832.9 913.9 830.3December 70.0 1852.6 1926.0 1745.5 Year 1416.5 9872.8 11200.2 10255.4 4. Conclusions In a typical year, assuming that the wind turbine is repaired, the total AC energy delivered by the hybrid PV/wind system is predicted to be about 10,255 kWh. Output from the wind turbine accounts for about 87% of this total. If the PV array is found to be faulty and is repaired, the output from the PV is expected to rise by about 70%, bringing the total annual output of the hybrid system to about 12,420 kWh.

References (1) ASHRAE Handbook of Fundamentals, 1981, page 5.1, Table 1.