Project Description

Introduction

Because of its location in western New Mexico, and the availability of dispersed small loads that are not connected to the electric grid, solar power appears to be an attractive option for the Pueblo of Zuni.

The tribe is currently relocating its main water source to the Ojo Caliente wells, about 11-16 miles south of the Pueblo of Zuni. Since there is no electricity available at Ojo Caliente, the new water pumping facilities would either require the extension of Continental Divide's existing power line from the Pueblo of Zuni to Ojo Caliente, or the use of remotely sited power supplies such as solar photovoltaic or diesel-based generation systems.

Goals and Objectives

The Pueblo of Zuni Tribe retained INTECH Research & Engineering Company to examine the potential for solar photovoltaic systems to support remote electric power energy needs of the Pueblo of Zuni Tribe. The work scope consists of four components:

• Study the potential for solar photovoltaic electric power to provide the entire energy needed to operate the Ojo Caliente water pumping system.

• Study the potential for solar photovoltaic electric power to provide backup electrical energy to be used when the primary electric power delivered by a hard wired system is down or to be used to reduce the pumping system's electric energy demand during peak energy usage periods.

• Define the education and training program that the Pueblo needs to assure the Pueblo Utility Department staff can service the solar photovoltaic power systems.

• Study the potential for solar photovoltaic electric power to provide sufficient electric energy to power a direct current pump to provide up to 800 gallons per day of well water at the Upper Nutria village center.

Project Actions and Resultant Data

PV water pumping for human consumption is the subject of a feasibility study conducted by the Zuni Pueblo of northwestern New Mexico. The current supply is from wells with an insufficient output of water that tastes bad and is contaminated with sulfates and uranium. Several wells at Ojo Caliente, 13 miles south of the village, produce an adequate supply of clean water, but there is no electricity available there for pumping. A line extension would cost an estimated $700,000. The feasibility study compares the cost of a PV pumping system, possibly with diesel backup, to the line extension.

Solar photovoltaic power systems have been installed and operated by several Indian tribes and electric utilities. Some examples of operating photovoltaic systems are:

• The Tohono O'odham Indian Tribe originally installed solar photovoltaic electric systems in 1978. The Tribal Power Authority uses the solar panels to provide direct current power for two applications: (1) they are installed at remote sites to pump water from shallow wells for cattle and isolated residences; (2) the bulk of the solar panels are used to power a direct current radio telephone system at a remote village.

• The Navajo Indian Tribe solar photovoltaic systems were installed at residences to power either direct current or alternating current appliances. Each system includes a set of batteries to store excess electric energy for use during the night. Owners, to date, have expressed a strong desire to change the system design to allow them to operate a small refrigerator for 24 hours per day. Some have indicated that they would even give up the ability to have electric lights if they could get a refrigerator. The Navajo Tribal Utility Authority believes that a refrigerator and TV are probably the more realistic energy demands.

• The Ute Mountain Ute Indian Tribe is upgrading wind-powered water pumps to solar power. Twenty wells with standing water at depths less than 300 feet deep were selected for upgrading to solar power. The tribe has trained their own personnel to install and maintain the pumps and solar systems, so there is no external cash expense for installation and maintenance. They also invested $25,000 to outfit a truck for well drilling or system maintenance. Maintenance consists of a weekly inspection visit and adjusting the solar panel tilt four times a year so that it collects a maximum of the available sunlight. A typical well conversion costs about $12,000 to purchase and install the solar photovoltaic system, a centrifugal pump, and a water tank. The cost is about $15,000 when jack pumps are used.

• The KC Electric Association provides solar photovoltaic systems to pump water to cattle and for irrigation use. Ice and winter storms break poles and power lines, and thus the cost of the remote-sited solar electric systems saves KC Electric significant repair and maintenance money compared to providing the power on hard-wired, pole systems (in 1988, 645 poles were broken in the winter, and in 1989 that number rose to 1,000).

• The Electric Utility Department of Austin, Texas, has installed photovoltaic systems ranging from small, 53-watt off-grid photovoltaic water meters to two large, 300 kW arrays interconnected to the grid. The grid presently has approximately 600 kW of photovoltaic capacity. The early research projects were large, consistent with the industry focus of the 1980s; the recent projects are smaller, dispersed residential and commercial systems for peak shaving. Capital costs of the early projects were $10/watt, which has decreased to approximately $6/watt in the recent projects. Peak shaving projects in new construction avoid the cost of new power plants, and avoid transmission lines and substations.

The operating experience shows that solar photovoltaic power systems can be a reliable source of electricity to the Pueblo of Zuni Tribe. The information obtained was used to develop two cases in addition to those in the contract work scope. Thus, the study analyzed four cases comprising a size range from the small remote systems (less than 500 watts) known to be economical to a very large stand-alone system to replace extending the power line. The four cases were:

Capital and operating costs for each case were generated using the SIZEPV computer program and cost information provided by Photocomm and Solarex. Thus, the costs presented in this report are representative of current costs of actual solar photovoltaic projects. The cases studied encompass the entire range of commercially demonstrated solar photovoltaic applications:

• The large, stand-alone power system used to operate the Ojo Caliente well pumps continuously is more expensive than extending electric power to the site. The solar panels will generate enough electricity during daylight hours to charge storage batteries and operate the pumps at night. In addition, there is excess panel area to enable the system to be recharged when the batteries have been completely discharged during a long period of cloudy days. The capital cost is more than $30 million because of the large photovoltaic panel area required.

• The backup system to operate one well pump during daylight, but no electricity at night costs about $4.5 million (approximately 14% of the stand-alone system). The costs of this system are much lower because excess panel area is not used to generate the entire power requirement. This case is of similar size to some operating solar photovoltaic projects. A solar photovoltaic water pumping system has energy backup available in the form of stored water, so storage batteries are not required and the system design can be optimized to pump excess water during the day for consumption at night when solar energy is not available. For this case, however, the optimized full-size (500 horsepower, 2 million gallons per day) system is more expensive than purchased electricity.

• Small water pumping systems in remote locations such as Upper Nutria Village can be quite economical. The total installed cost of the Upper Nutria water system is estimated to be between $6,500 and $15,000, including the solar photovoltaic power supply, well, pump, and water tank. This assumes contractors perform all labor. These costs are consistent with actual experience at Ute Mountain.

• Small photovoltaic systems with capacities between 240 watts and 1,000 watts and costing between $4,000 and $15,000 can supply the electric power needs of residences in remote locations. The smallest system will provide sufficient direct current power for electric lights, a ceiling fan, a television, and a refrigerator. The larger system could provide power for lighting and alternating current appliances. These systems include some battery storage to permit nighttime operation.

• Larger, grid-connected photovoltaic systems between 2,000 watts and 20,000 watts and costing between $22,000 and $206,000 can provide alternating current electric power to small office buildings.

In addition to the solar photovoltaic cases, two remote diesel engine cases were developed for possible companion and use in a subsequent optimization study. Diesel driven power systems can be economical in remote locations where the power demand is high enough that the capital cost savings offsets the cost of diesel fuel. The two diesel cases developed in this study have energy costs approximately equivalent to 8 cents to 11 cents per kWh.

The results of the different cases studied show that solar photovoltaic power systems can be additive under several conditions:

• For small loads in remote locations, the avoided cost of extending power lines to the remote site pays for the solar power supply. This is the case for applications like the Upper Nutria drinking water system.

• The power company's other avoided costs (new substation or generating capacity, for example) are high enough to make solar power attractive. This might not be true for the Pueblo.

• Environmental externalities, such as avoided air pollution can be translated into a dollar credit to offset some of the capital costs.

• Nighttime electric load is small.

Other findings of the study were:

• Solar power systems without storage batteries are more economical than stand alone systems.

• For remote medium size loads, which have easy road access, diesel engines appear to be the most economical power supply.

• The most attractive solar projects are elsewhere on the reservation where electricity is presently unavailable.

  • Very small remote residential systems with storage batteries.
  • Small remote water systems similar to Upper Nutria.
  • Small remote residential and commercial systems without storage batteries.

However, an integrated system optimization study is needed to match the individual loads (residence, office, water pumping, etc.) to the appropriate power source (solar photovoltaic, purchased electricity, hot water, diesel engine, etc.) such that the total cost of energy is minimized.

Results, Conclusions, Findings, and Recommendations

The large, stand-alone power system to operate the Ojo Caliente well pumps continuously is more expensive than extending electric power to the site. The solar panels will generate enough electricity during daylight hours to charge storage batteries to operate the pumps at night. In addition, there is excess panel area to enable the system to be recharged when the batteries have been completely discharged during a long period of cloudy days. The capital cost is more than $30 million because of the large photovoltaic panel area required.

The backup system to operate one well pump during daylight, but no electricity at night costs about $4.5 million (approximately 14% of the stand-alone system). The costs of this system are much lower because excess panel area is not used to generate the entire power requirement. This case is of similar size to some operating solar photovoltaic projects. A solar photovoltaic water pumping system has energy backup available in the form of stored water, so storage batteries are not required and the system design can be optimized to pump excess water during the day for consumption at night when solar energy is not available. For this case, however, the optimized full size (500 horsepower, 2 million gallons per day) system is more expensive than purchased electricity.

Small water pumping systems in remote locations such as Upper Nutria Village can be quite economical. The total installed cost of the Upper Nutria water system is estimated to be between $6,500 and $15,000 including the solar photovoltaic power supply, well, pump, and water tank. This assumes contractors perform all labor. These costs are consistent with actual experience at the Ute Mountain Ute Reservation.

Small photovoltaic systems with capacities between 240 watts and 1,000 watts cost between $4,000 and $15,000. They can supply the electric power needs of residences in remote locations. The smallest system will provide sufficient direct current power for electric lights, a ceiling fan, a television, and a refrigerator. The larger system could provide power for lighting and alternating current appliances. These systems include some battery storage to permit nighttime operation.

Larger grid-connected photovoltaic systems between 2,000 watts and 20,000 watts and costing between $22,000 and $206,000 can provide alternating current electric power to small office buildings. There is a potential to obtain federal funding to develop a solar demonstration project that will power the administration building or other facilities.

Solar Photovoltaic Power Systems Can Be Attractive

For small loads in remote locations, the avoided cost of extending power lines to the remote site pays for the solar power supply. This is the case for applications like the Upper Nutria drinking water system.

For situations where the power company's other avoided costs (for example, when the solar power means that the utility will not have to install a new substation or new generating capacity) are high enough to make solar power attractive. In those cases, the power company may even fund the purchase of the solar power equipment. This may not be true for the Pueblo.

Environmental considerations, such as avoiding the air pollution that results from power generation, can be translated into a dollar credit which can be used to provide some of the solar power system's capital costs.

Nighttime electric load is small, thus the batteries needed for the solar system are not expensive.

Other Findings

• Solar power systems without storage batteries are more economical than stand alone systems.

• For remote, medium-size loads that have easy road access, diesel engines appear to be the most economical power supply.

• The most attractive solar projects on the reservation are where electricity is presently unavailable.

• Very small remote residential systems with storage batteries.

• Small remote water systems similar to Upper Nutria.

• Small commercial systems that do not have a nighttime operation.

Recommendations

The tribe now plans to meet with Zuni utility, economic development, and training personnel to discuss future needs and to develop the information for the training and solar program needs of our report.

Tribal Council authorization is needed to develop proposals for the following activities:

• It is believed possible to obtain funding from the U.S. Health and Human Services, Administration for Native Americans to develop:

  • A Pueblo business plan for applying solar power at the Pueblo.

  • The Government Tribal Ordinances to cover the tribe providing electric power to residences and businesses

  • A description and the initial planning for a Tribal Power and Utility Authority

• It is also possible to obtain funding from the U.S. Department of Energy for purchasing solar power systems and for obtaining the needed operator training.

The information on the Pueblo's training needs and the need for a Power Authority to manage solar power systems is also included in the final report of this project.

Project Status

For current project status or additional information, contact the project contacts.

Project Contact

Pueblo of Zuni
PO Box 339
Zuni, NM 87327
Telephone: (505) 782-4481

<p><strong>Tribe/Awardee</strong><br />Pueblo of Zuni</p><p><strong>Location</strong><br />Zuni, NM</p><p><strong>Project Title</strong><br />Solar Water Pumping Feasibility Study</p><p><strong>Type of Application</strong><br />Feasibility</p><p><strong>DOE Grant Number</strong><br />DE-FG48-94R810518</p><p><strong>Project Amounts</strong><br />DOE: $91,781<br />Awardee: $23,003<br />Total: $114,784</p><p><strong>Project Status</strong><br />Complete</p><p><strong>Project Period of Performance</strong><br />Start: September 1994<br />End: July 1996</p>