From: Essential Information <ei@igc.apc.org>
Newsgroups: sci.energy
Date: 31 Dec 92 12:38 PST
Subject: Re: Energy Ideas -- Solar Power
Nf-ID: #R:cdp:1466300121:cdp:1466300123:000:30473
Nf-From: cdp.UUCP!ei    Dec 31 12:38:00 1992


PHOTOVOLTAIC SYSTEMS

Today's cost-effective photovoltaic (PV) applications are
decentralized.  They provide power at the point of application. 
This is a shift from the common notion of "plugging" into an
existing utility service, which provides power from a central
plant.  Since solar power is produced at the site, it does not
require the expensive above- or below-ground wires, substations and
generators which accompany utility service.  In some locations, PVs
provide power where utility service is inaccessible.

PV systems can also replace other decentralized power sources, such
as diesel generators and disposable batteries.  PVs eliminate the
fuel and maintenance costs of diesel generators while providing
quieter and cleaner operation.  The rechargeable batteries in a
solar system last longer, weigh less and cost less than disposable
batteries.  

When considering the full life-cycle costs of diesel, disposable
batteries or solar power in areas where an electric utility is not
currently supplying power, solar power is the most cost- effective
source of energy.

PV cells generate electricity when exposed to sunlight.  A PV cell
is a sandwich of two types of semiconductors, one made with an
excess of electrons and one made with a lack of electrons. 
Electricity can only flow in one direction across the boundary
between the two types.  When sunlight strikes the excess electrons,
they travel across the boundary and return through an external
circuit, generating a current.  This current may be used either to
power equipment or charge a battery.

PV cells are made of pure silicon, the element predominant in sand.

There are four types.  Single-cell PVs are manufactured by melting
silicon and crystallizing it into an ingot.  Cells are then made by
slicing the ingot into thin wafers.  Each cell produces about
one-half volt, but the larger the area of the cell, the greater the
amount of current it produces.  These cells lose efficiency as
their operating temperature rises.

Polycrystalline PV cells use lower-grade silicon than single-cell
PVs, producing a sheet which has a random crystal pattern.  Ribbon
silicon cells are manufactured by growing a ribbon from the silicon
and cutting it into sheets.  Amorphous silicon cells, the most
recent development, are sheets of silicon with no crystal
structure.  These cells are less costly but less efficient.

PV panels are connected arrays of single cells or large pieces of
ribbon or amorphous silicon.  Panels may be connected in series or
in parallel to produce greater voltage or current.  
Other components of a PV system depend upon the application.  If
the system exists for daytime use only, the system will include a
"power-point tracker," a device which monitors the system
performance and makes electrical adjustments to keep the system
operating as close as possible to the maximum output (i.e.,
combination of current and voltage).  Nighttime applications also
require a battery bank to store the energy and a charge controller
to prevent overcharging or excessive discharging of the batteries.

Like any piece of equipment, successful PV systems require
competent design.  Small PV packages, such as battery chargers, can
be purchased in units.  Differences in application sites require
the vendor to design larger systems, for outdoor lights, water
pumps, or other applications, around each need and site.  Each
system requires a certain amount of power.  - Each site has a
particular insolation (incident solar radiation) level as well as
an expected number of consecutive cloudy days.  The PV panels must
not be shaded nor allowed to get too hot.  The vendor should
explain the ways these factors relate to the product. 

It is important to point out that, to date, PVs are not a
cost-effective means of replacing existing utility electric
service.  The payback times for the installation of solar-powered
parking lot lights to replace a current system or installing PVs to
replace the power generation of a building would be decades, given
the current cost of these systems.  However, when con- sidering the
electricity requirements for new buildings and systems, such as the
ones described in this report, solar systems are a viable
alternative.  They should be given the strongest possible
consideration, given their environmental and economic benefits.

AND NOW, A LITTLE ILLUMINATION    

Lighting, particularly with high-efficiency lights, does not
require a substantial power supply for each individual light.  PV
panels can charge a battery all day and then the batteries will
power lights for a parking lot, a bus shelter, a billboard, or
other areas all night.  Timers and light sensors are important
components of these systems to limit the discharging time of the
battery.  Just the avoided cost of a utility extension can pay for
these systems.
CASE STUDIES

In 1987, the Florida Solar Energy Center, in cooperation with the
Florida Department of Transportation and Florida Governor's Energy
Office, initiated a project to design, install and monitor the
performance of a PV lighting system for an overhead highway sign. 
The system was installed in 1988, consisting of twenty solar panels
(totaling 1032 watts), batteries, and six 40 watt lamps.  The lamps
have a lifetime of 30,000 hours, as compared to conventional lamps
which have a shorter life.  The solar panels have impact shields to
reduce the potential for damage from gunshots or other projectiles.


Extension of service from the utility to the sign would have cost
$2/foot for an overhead line and more than $5/foot for underground
extension. Florida Power & Light would have provided an overhead
7,260 volt service at $9,000 per mile, and the distance was more
than five miles.  The capital costs for the PV system amounted to
$20,000, including the array, batteries, system controller,
mechanical components and labor.  The system has operated reliably
since 1988 with no down-time.  (Contact: Jim Dunlop, P.E., Florida 
Solar Energy Center, 300 State Road 401, Cape Canaveral, FL, 32920,
(407) 783-  0300.)

       The Pinetop, Arizona, planning department installed six
PV-powered lights in the  parking lot of the Pinetop high school. 
The lights were needed to illuminate the  entrances of the school. 
The project was funded through oil overcharge monies (see 
FINANCING, p.10).  The school system installed the system as an
educational tool for  the students.

 Each light system, including pole, panels, batteries, and charge
controller, cost $1,000.   The lights remain lit from 7:00 pm until
4:00 am.  The only maintenance requirement  has been checking the
charge levels on the batteries.  The lights have been in  operation
for four years without requiring replacement of any parts. 
(Contact: Tom  Thomas, Pinetop Town Offices, Planning and Zoning
Department, 1360 N. Niels  Hansen, Lakeside, AZ, 85929, (602)
368-8696.)

       The Illinois Department of Energy and Natural Resources
(ENR) has sponsored a  number of projects to demonstrate the
applicability of solar energy.  One such project,  completed
between 1985 and 1989, involved the installation of 13 PV-powered,
135 W  high-pressure sodium outdoor lights at recreational parks. 
Though the first set of light  poles cost almost $3,600 per system,
by the end of the project poles cost less than  $2,000 due to
improvements in production.  It would have cost between $7,000 - 
$8,000 per light to connect to the utility grid.  Initially the
lights were subject to  vandalism because the poles were only 14
feet high.  In addition, PV-thieves could use  the systems on their
boats.  Subsequent designs have made the poles higher and the 
batteries unusable for any application except the lights. 
Vandalism has not been  reported since these changes, and ENR has
reported the project to be extremely  successful.  (Contact: R.
Forrest Lupu, Illinois Department of Energy and Natural Re- 
sources, 325 W. Adams St., Springfield, IL, 62704, (217) 785-3484.)

       The Queens Borough Department of Parks in New York City
recently agreed to install  six solar-powered light poles at its
Ally Pond Environmental Center. People were  illegally dumping
waste on the Center's grounds, and the staff wanted to install 
security lighting.  The New York Power Authority (NYPA) donated the
equipment to  test the solar technology in a demand-side management
effort.  The six light poles cost  $18,594, and installation labor
cost $2,700.  Installation of utility-connected lights  would have
cost roughly $18,000.
 Three poles are testing low-pressure sodium lights and the other
three are testing  fluorescent fixtures.  The batteries are
gel-cell batteries and are contained in a vented  box at the top of
the 20' tall poles.  The ventilation prevents buildup of hydrogen
gas  in the battery box and the location prevents vandalism.  
These batteries usually last  three years, but due to protection
from deep discharging, they should last up to five  years.  The
system was designed to operate for five days without sunlight.  The

systems have performed without a problem. (Contact: Mark Kapner,
New York Power  Authority, 1633 Broadway Ave., New York, NY, 10019,
(212) 468-6725.)

       In 1986, Tallahassee Transit installed PV lighting systems
on 10 of 100 new bus  shelters.  The systems consist of solar
panels, lights, batteries, photocells and timers;  the photocells
activate the lights at dusk and the timers turn off the system
after the  last bus arrives.  Each system cost $1,500. Connecting
the lights to the utility would  have cost $300-$400.  The payback
time for this system is roughly 10 years.   Tallahassee Transit
commented that their lack of expertise in maintaining the systems 
proved to be a problem; the systems were occasionally hampered by
minor difficulties  and needed to be temporarily disconnected
because the staff did not know how to  repair them.  Though the PV
panels were mounted horizontally on top of the shelter,  keeping
them out of sight, to prevent vandalism, a few have been stolen. 
(Contact:  Larry Carter, Tallahassee Transit, 555 Apple Yard Drive,
Tallahassee, FL, 32304,  (904) 574-5200.)

WIRELESS COMMUNICATION VIA RADIOS AND TELEPHONES

While radio broadcasting allows people to communicate with one
another over great distances without wires, the systems themselves
still require power supplies to drive the electronics.  The use of
PVs creates wireless systems, providing both generating and
broadcasting capabili- ties in one unit.  These systems have been
used for both radio broadcasting and cellular highway emergency
phones.

CASE STUDIES

       The Illinois Department of Transportation installed AM radio
transmitters at highway  rest stations to broadcast weather
conditions for travelers.  Each cost $3,280 and has  been
operating, without difficulty, since April 1988. (Contact: ENR
Information  Clearinghouse, Illinois Department of Energy and
Natural Resources, 1-800-252-8955.)

       After a woman was attacked on a California freeway while she
walked from her  stranded car to get help, citizens demanded that
emergency phones be posted along the  freeway at no greater than
,-mile intervals.  The Service Authority for Freeway  Emergency
(SAFE) decided to install 300 phones along 1,200 miles of freeway
in Or-  ange County, California.  The project would have cost a few
million dollars had SAFE  dug a trench along the freeway for
utility and phone lines.  Instead, SAFE purchased  PV-powered
cellular phones at a cost of $3,250 per phone (a total of
$975,000).  The battery on each phone stores enough  energy to last
six days.  SAFE reports a total of 3,000 calls a week.  The phones
have  greatly improved response time to emergencies along the
freeway.  The State of  California has installed a total of 8,000
of the phones.  (Contact:  Todd Murphy, Or-  ange County
Transportation Commission, 11222 Acacia Parkway, Garden Grove, CA, 
92460, (714) 638-3868.)     Corrosion Prevention Through the Use of
Solar Power

Corrosion is caused by the exposure of metal to electrolytes or
oxygen, which take electrons and weaken the metal.  Cathodic
protection systems reverse the flow of electrons by running an
electric current from a sheet of metal close to the structure, the
anode, into the structure, which acts as the cathode.  Cathodic
protection systems are widely used by the oil industry to protect
wells and pipelines.  PV systems can also prevent the weakening of
docks, bridges and buildings.

CASE STUDY

       The U.S. Navy installed a 1440 W cathodic protection system
to prevent corrosion of  a 775 ft.-long dock at the Naval Coastal
Systems Training Center in Panama City,  Florida.  The solar panels
provide the DC current to the anode, which runs through the  water
to the dock.  The panels only operate during the day.  Using this
system elimi-  nates the need for expensive rectifiers, which
change AC current to DC current, as  well as batteries to store the
electricity from the panels.  The system has been  operating for 2+
years without any problems.  (Contact: Dick Miller, Technology 
Transfer, or Wally Muehl, Public Works Engineer, Naval Coastal
Systems, 3610 WM,  West U.S. Highway 98, Panama City, FL, 32407,
(904) 234-4742.)

A DEAD BATTERY CAN BE A THING OF THE PAST

To remain fully charged, vehicle batteries require periodic
operation of the vehicle.  Allowing the vehicle to sit for extended
periods of time, or running equipment on the battery while not
operating the vehicle, will eventually drain the battery of its
charge.  PV "trickle-chargers" can maintain a constant charge in
the battery to ensure a reliable startup.

CASE STUDIES

       The Metropolitan District Commission (MDC) in Stoneham,
Massachusetts installed  trickle-chargers on 32 intermittently-used
emergency vehicles (plows, earth-movers and  other heavy-duty
vehicles).  The PV arrays were themselves mounted onto a metal 
plate on top of the cab.  Unfortunately, this shorted the circuit
from the PV panel to  the battery by allowing the electricity to
pass into the roof of the cab rather than along  the wires into the
battery.  Although a newer design has improved upon this problem, 
the array is also covered by a glass plate, making it very fragile.

A number of the  systems broke while in use because the trucks pass
over rocky areas and under branch-  es.  

The MDC stated that the system could be very effective if a PV
charging "station"  were built and the vehicles were connected to
the station during periods of non-use.   Then the PV system would
not be damaged during operation.  The on-vehicle system  may be
more appropriate for lighter-duty vehicles or boats, where the
bilge pump may  operate and drain the battery while the boat
remains docked.  (Contact: Marty Glavin,  Metropolitan District
Commission, Central Services, 1 O'Brien Highway, Cambridge,  MA,
(617) 727-7663.)

       The Army National Guard uses vehicles intermittently
year-round.  The guard  purchased 128 battery chargers in 1988.  At
Camp Edwards, Massachusetts, rather  than being attached to the
vehicles, these chargers are attached to permanent  structures, and
the vehicles are "plugged" into the chargers when not in use.  This

avoids the potential for damage experienced by the Metropolitan
District Commission  in Massachusetts.



PHOTOVOLTAICS CAN POWER "SATELLITES" HERE ON EARTH

Photovoltaics provide the power to space satellites for data
collection and transmission.  They can also power monitors on earth
for data collection and transmission.  Either permanent or mobile
stations monitoring atmospheric conditions, radiation levels,
contaminant levels in water or other conditions for extended
periods can be powered by PVs.

CASE STUDIES

       The Weather Project Management Office at the John F. Kennedy
Space Center  installed six weather-monitoring devices within a six
mile radius of the Center.  The  devices measure lightning and
transmit the data back to a central station.  Since the  equipment,
placed atop 50' tall telephone poles, needs to be operational at
all times,  particularly during electric storms, conventional power
is not sufficiently reliable.   Photovoltaic systems were chosen
over disposable batteries due to the longer life of  the
PV-rechargeable batteries.  The transmitters require roughly 30
watts of power.   The systems have worked flawlessly for 1+ years
and have even survived two light-  ning strikes while the
transmitters did not.  

       The Illinois Department of Nuclear Safety (DNS) developed a
mobile radiation  monitoring unit.  All of the instrumentation and
radio transmitters are powered by  three 42 watt panels and a 12
volt, 210 amp-hour battery.  The cost for each of the  radiation
monitoring units was $4,378.  Three units have been purchased and
are being  used to monitor low-level radioactive waste sites.  The
systems have operated without  difficulty.  (Contact: ENR
Information Clearinghouse, Illinois Department of Energy  and
Natural Resources, 1-800-252-8955.)

A RESPONSIBLE AND RELIABLE SOURCE OF POWER FOR SAFETY

Boating

On the water, photovoltaics can provide an alternative source of
power for towers and buoys where only one has existed - disposable
batteries.  

According to a U.S. Coast Guard report, disposable batteries have
a number of unattractive attributes, including high replacement
costs, restricted availability, and increasing disposal costs
resulting from environmental hazards.  Zinc-air disposable
batteries have a highly alkaline solution (pH of 14) and also
contain mercury.  On-site disposal or deep ocean dumping disrupts
the pH of the water, making it uninhabitable for some species of
fish and releases mercury into the food chain where it poses a
human health hazard.  Thus, depleted batteries must now be returned
to shore for disposal in hazardous waste sites.

PV systems prevent these hazards while costing less.  According to
the U.S. Coast Guard, the lead-acid batteries in the PV systems can
be recycled. These batteries are also much smaller, allowing the
entire system to be transported by one person rather than an entire
team.   

CASE STUDIES

       Six towers housing flash flood warning sirens stand along
the three-mile stretch of  riverbank at Pedernales Falls State Park
50 miles west of Austin, Texas.  Installed in  1983, the PV systems
consist of a 20-watt PV panel and a storage battery.  The cost  of
each PV system was $1,000; extension of utility service to the
towers was  impossible.  According to the Texas Parks Department,
the solar system has been very  reliable.  (Contact: Bill
McDaniels, Texas Parks and Wildlife, Route 1, Box 450,  Johnson
City, TX, 78636, (512) 868-7304.)
       The U.S. Coast Guard has installed between 12,000 and 14,000
PV systems to power  navigational aides.  These replaced systems
powered by disposable batteries which  required replacement every
two years.  Replacement of these batteries cost nearly  $500/hour
at remote buoys.  The PV systems power batteries which require 
replacement every five years.  The Coast Guard is also considering
switching three  lighthouses along the East coast, damaged in a
storm last year, from diesel to PV.   (Contact: John Grasson, U.S.
Coast Guard, Civil Engineering Division, 2100 Second  Street SW,
Washington, DC, 20593, (202) 267-1892.)

       The New York Department of Environmental Conservation (DEC)
installed PV-  powered battery chargers on Lake George and Schroon
Lake to replace disposable  batteries on warning buoys.  The
previous system used 18 batteries annually at a cost  of $40 per
buoy.  Now, two six-volt PV panels and a six-volt, 120-milliamp
battery,  costing $15, have been installed and will last for five
years.  Replacing the battery  costs $8.50.  The DEC installed 120
systems on Lake George and 20 at Schroon Lake.   Photocells turn
the lights on and off.  (Contact: Dean Meyers, New York State
Depart-  ment of Environmental Conservation, RR3 Box 3489, Ft.
George Road, Lake George,  NY, 12845, (518) 668-4125.)

Traffic Control

Warning signs are a necessary part of road and highway construction
to inform drivers of construction and to redirect traffic.  These
warning signals, such as flashing arrow boards or warning strobes,
are usually powered by diesel generators or disposable batteries. 
Diesel generators emit particulates and carbon dioxide, and they
are also very noisy.  Batteries release hazardous materials into
the environment.  Solar systems eliminate pollutant emissions and
provide quieter operation.

CASE STUDIES

       The City of Austin, Texas, purchased three PV-powered
flashing arrow boards to  direct traffic around construction crews.

The older systems used diesel generators.   The PV systems have
panels placed above the arrow and a battery bank which can  operate
for 30 days without sunlight.  Each system cost $5,300.  Though the
money  saved in fuel costs would pay back the project cost in 13
years, fuel savings are not  the only savings.  Labor and
maintenance savings reduce this payback time to five  years.  The
workers prefer the PV systems because they do not need to be
refueled  and they are quieter.  (Contact: John Hoffner, City of
Austin Electricity Department,  721 Barton Springs Road, Austin,
TX, 78704, (512) 322-6284.)

       The Illinois Department of Transportation (IDOT) also bought
flashing arrow boards,  but were not  happy with the results.  The
solar panels on the system could not  sufficiently charge the
batteries to keep the boards running 24 hours a day.  IDOT 
attributes the difficulties with the systems to vendor
irresponsibility.  The vendor did  not properly instruct IDOT
employees to care for the system, and the system was not  capable
of operating under the sunlight conditions experienced on the road.

The vendor bid a lower price but the  equipment was inappropriate
for the application.  IDOT suspects that the system  vendor was not
capable of assembling a high-quality system.  

 Each arrow board cost $4,600, as opposed to $2,750 for a diesel
generator and $2,800  for a primary battery system.  Next, IDOT
rented a few solar arrowboard systems  from a distributor in Texas,
using them from June to August and had no problems  with them. 
(Contact:  Brandon Long, Illinois Department of Transportation,
2300 S.  Dirkson Parkway, Springfield, IL, 62764, (217)
782-7234.)        

PHOTOVOLTAIC PUMPS: MAINTENANCE-FREE WATER AND AIR

Photovoltaic systems can provide the power required by water and
air pumps.  In remote locations, these systems will prevent long
trips for refueling diesel generators or replacing disposable
batteries.  For more central locations, PV systems will prevent the
extension of a utility line which ruins the aesthetics of a
location.

CASE STUDIES

       A drip-irrigation system powered by PVs provides water for
a belt of Russian olives,  Ponderosa pines, and Rocky Mountain
Junipers that serve as a wind shelter for cattle.   The system is
just south of Cheyenne, Wyoming, on Interstate 25.  The Wyoming 
State Highway Department installed it in April 1983 at a cost of
$12,000 and has not  had any problems with its operation. 
(Contact: Kevin Powell, Wyoming State High-  way Department, Box
1708, Cheyenne, WY, 82003-1708, (307) 777-4156.)

       The State of Utah sought to eliminate riparian water damage.

Cattle were drinking  from streams and rivers, trampling and
destroying the vegetation which prevents  erosion along the
streambeds.  In addition, their manure ran from these streams into 
major rivers and lakes, causing algal blooms which 

killed fish and prevented spawning.  Water pumps deliver drinking
water away from  the streams and encourage cattle to graze and
water in the same areas.  Utah's Depart-  ment of Natural Resources
purchased 15 PV-powered water pumps to replace diesel  pumps. 
Workers no longer drive long distances every morning to start and
refuel the  diesel systems.  The PV systems had some difficulty
with power control for positive-  displacement pumps but these were
solved. (Contact: Britt Reed, Utah Department of  Natural
Resources, Division of Energy, 3 Triad Center Suite 450, Salt Lake
City, UT,  84180, (801) 538-5428.)

       A pond aeration system at the Walter Heller Nature Center,
Highland Park, Illinois is  powered by a PV system.  The pond had
poor water quality due to problems with very  low dissolved oxygen
levels.  The PV system pumps air through the water during the 
daylight hours when dissolved oxygen is at its lowest.  The system
was installed for  $3,500.  The utility would have needed to step
down power from a main transmission  line and then feed a line
through the park to the pump, costing over $100,000.  (Con-  tact:
R. Forrest Lupu, Illinois Department of Natural Resources, 325 W.
Adams St.,  Springfield, IL, 62704, (217) 785-3484.)
PHOTOVOLTAICS PROVIDE FULL POWER TO REMOTE FACILITIES

PV systems are ideal for providing power to restroom facilities,
either in remote locations or along highways.  The power
requirements vary from tens of watts to run a small air circulation
fan to hundreds of watts for interior and exterior lights and water
pumps for sinks and showers.

Solar electric systems can also provide all the electricity needed
for facility operation.  A PV- charged battery bank can power
pumps, fans, lights, office equipment, telephones and other
appliances necessary for day-to-day operation.  Using highly
energy-efficient appliances and lights will reduce the cost of the
PV system since the power requirements will be lower. 

According to Sandia National Laboratory, well over 17,000 such
systems, many of which are for residences in out-of-the-way
locations, have been installed around the world.  These systems
generally provide less than 3.0 kilowatts of array power and may
include a diesel or propane generator for back-up power during
periods of bad weather.

CASE STUDIES

       The State of New York Department of Environmental
Conservation (DEC) wanted a  "cost-effective, low-maintenance,
quality restroom" at Prospect Mountain, an area  without plumbing,
a sewage system, or utility access.  The DEC installed a zero-dis- 
charge, composting toilet which evaporates all liquids and composts
the solids.  PVs  power pumps to circulate liquids, fans to dry the
solids, and lights.  The only  maintenance is dumping sawdust into
the system each day to facilitate composting.   The unit on
Prospect Mountain, containing eight toilets, cost $80,000. 
Bringing  electricity and plumbing to the area in any other way
would have been economically  impossible and environmentally
damaging. Single units cost $8,000 (including the  building).  The
older toilets cost $60 per week for a sewer pumper to service them,

totaling $3,000 each year.  Savings from the elimination of sewer
service pay back the  purchase of a single unit in under three
years.  (Contact: Dean Meyers, New York  State Department of
Environmental Conservation, RR3 Box 3489, Ft. George Road,  Lake
George, NY, 12845,  (518) 668-4125.)

       Another PV-powered "recycling" comfort station was installed
at the Hart Miller State  Park at Chesapeake Bay, Maryland.   The
system worked well for four years.  During  that operation period,
the Maryland Boating Administration constructed an office  building
on the island and powered the building from the local utility. 
When the  battery bank for the solar system at the comfort station
needed to be replaced, the park  service compared the cost of
replacing the batteries to connecting to the utility service  now
on the island.  Utility service proved to be far less expensive,
and the PV system  was dismantled.    Solar power could have been
maintained if the office building had  been powered by PVs as well.

       The Ranger's Residence in Wrangell St. Elias National Park
in Alaska runs on an  integrated system of diesel generators and
photovoltaics.  The residence, a 900 sq. ft.  log cabin, requires
electricity for the lights, washing machine, refrigerator and other

amenities necessary for year-round living.  The generators, PV
panels, batteries and  other electrical equipment are located in a
shed outside of the house, eliminating fire  hazards and noise
problems posed by the diesel generators.

 The eight-panel array provides all of the electricity in the
summer months and  supplements the supply in winter.  In winter the
diesel generators operate for two  hours per day both to charge the
battery bank and to heat the shed.  The shed must  remain warm to
allow the generators to start and the batteries to operate at an
efficient  temperature.  The electricity is converted from DC to AC
for operation in the house.   According to the residents, the PVs
are better than the generators because they do not  require
constant attention; the residents can leave for a few days and
return to fully-  charged batteries.  Everyone who lives in the
residence is pleased with the system.   (For non-technical
information, contact: Will Tipton, Wrangell St. Elias National
Park,  Box 29, Glennallen, AK, 99588, (907) 822-5234.) 

PHOTOVOLTAIC DEMONSTRATION PROJECTS POWER THE UTILITY GRID

Although not yet cost-effective, some utilities are installing PV
systems to provide a substantial portion of a building's energy
demand.  These demonstration projects provide lessons in
large-scale solar power generation and yield information which will
make the next demonstration project, and ultimately commercial
projects, less expensive and more reliable.  

CASE STUDIES

       Niagara-Mohawk, a utility in central New York State,
installed 15 kilowatts of power  on the roof of the Naval Building
in Latham, New York, as a demand-side  management demonstration
project.  The system has been working without any problems.  The
utility will test a battery system this Fall.  (Contact: Jim
Donogan, Niagara-  Mohawk Research and Development Department, A-2,
300 Erie Blvd. West, Syracuse,  NY, 13202, (315) 428-6970.)

       Eight kilowatts of PV power were installed at Nantucket,
Massachusetts, Elementary  School for $80,000. The PV arrays,
connected to the local utility grid, provide supple-  mentary power
to the school and have worked extremely well.  The panels cover one

portion of the roof over the cafeteria. (Contact: Virginia Faria,
Nantucket Elementary  School, 30 Surfside Road, Nantucket, MA,
02554, (508) 228-7208.)