Solar power is gaining more backers in the commercial market, as innovative technology and less intrusive design enhance its appeal. Under a pilot program with a supplier, Sacramento Municipal Utility District (SMUD) is offering customers a 2- to 4-kW power plant that is designed to blend with the shingles. In northern California, SMUD has become an activist organization in the spread of solar power, chiefly because of the explosive population growth in its area. Although most solar-powered roofs in SMUD's PV Pioneer program are on residences, 20 other sites take part in the project. The Power Authority has said that the experience it receives by installing various systems will prove very valuable when manufacturing and market influences drive prices down, and solar power becomes a profitable enterprise for the agency. Photovoltaic panels deck the roof of one of the Sacramento Municipal Utility District's customers; the small power plants feed electricity to the grid at peak hours of the day.


Solar power may finally be shedding its image problem. One of its biggest boosters right now is NASA. Solar cell technology has an important role in the National Aeronautics and Space Administration 's Performance Plan for 1999 and beyond. The agency pledges a" faster, better, cheaper" approach to reduce spacecraft development time and costs.

But solar power is also getting more backers in the commercial market here on the ground, where banks of cells and even some roofing materials provide primary power for households and contribute to the available electricity supply. A California utility, for instance, has embarked on a program that could eventually supplement its power generation capacity by about 10 MW of photovoltaic energy created right on the roofs of customers ' homes. In New York, a program of a different sort has, as one of its long- range aims, a curb on taxes.

Advocates argue that photovoltaic energy is extremely simple and clean, involves no moving parts, needs no support facilities, and has no toxic by-products to conflict with the environment. Basically, you take a substance and expose it to sunlight. The only environmental impact is in the manufacture, which is minimal.

Solar power has its share of marketing problems. Not only does the cost of installation make it more expensive than electricity from traditional sources, but the panels are troublesome to set and, in some cases, ugly. New marketing deals and new product designs are attempting to address those problems.

The solar power movement is only a few years old in the United States, but given its aggressive marketing for the last 15 years in other countries, it is much stronger in Europe and Japan. And it is gathering support in the States.

Signs of strength in the solar technology market have encouraged BP Amoco, for example, to commit significant production volume to the cells. The company operates BP Solar, which has manufacturing plants in six countries, including one in Fairfield, Calif. BP says the cost of solar cells is now one-seventh of what they were in 1980, because of improved manufacturing methods and increased market demand. BP Solar expects its sales will increase to $1 billion in the next decade. BP Solar makes crystalline silicon and thin film modules, and calls itself an integrated solar power supplier; that is, it designs, makes, markets, installs, and services solar power systems.

In northern California, the Sacramento Municipal Utility District has become an activist organization in the spread of solar power, chiefly because of the explosive population growth in its area. With more than 500,000 customers, it is the fifth - largest municipally owned electric utility in the United States in terms of customers served. The company, which goes by the nickname of SMUD, has had to address both distribution and production issues that do not face utilities serving longer-established populations, which already have poles and lines widely installed.

Power generation costs about half as much as putting in transmission lines. Running new residential lines costs in the neighborhood of $1 million a mile, and running power to an industrial site can cost significantly more. So SMUD looked seriously at alternative power to reduce capital costs. It polled customers to ask if they were interested in green energy. The answer was emphatically yes and, in 1993, the utility embarked on a solar power project called the PV Pioneer Program.

SMUD offers to install solar panels on the roofs of customers who volunteer to participate. Under the original plan, the utility owns and maintains the solar systems. Homeowners pay the same as their average electric bill plus a surcharge of about $4 a month. Four hundred fifty homes and 20 other sites participate in the program, which contributes 1.5 MW to the power grid.

A new version of the program, PV Pioneer H, offers to sell systems using solar panels or an alternative, photovoltaic roofing, to customers, who own the power that is generated. More than 200 homeowners have applied for the deal, said Sherri Eklof, program manager for the Pioneer 11 program. She said SMUD has a goal of installing a maximum of 100 systems this year.

Until recently, the cost of a solar power installation for an individual home has been about $18,000 in the open market, but SMUD's customers can purchase a complete 2 kW solar power system for $4,740. SMUD picks up just over half the actual cost of the installation, so the total price for the job comes in around $10,000. The price, which is for a system using solar panels, includes the arrangements for net metering, which is necessary to sell extra power back to the utility. The utility makes available a l0-year credit plan that charges 9.5 percent.

According to Eklof, three installations have been completed so far under Pioneer n, which was launched last fall.

The solar panels from SMUD's principal supplier, Energy Photovoltaics Inc. of Lawrenceville, N.J. , do not use conventional crystal wafers, but instead are made with a thin film coating on glass, a design that reduces the cost of the product.

A secondary supplier to the Pioneer II program is Solarex, a BP Amoco subsidiary based in Frederick, Md.


Photovoltaic Systems

Energy Photovoltaics, or EPV, has a deal to deliver 10 MW of solar power products to SMUD over the five years, through 2002 . The utility has a similar arrangement for inverters with Trace Engineering of Arlington, Wash., Eklof said. EPV's product uses amorphous silicon in what it calls photovoltaic modules. Conventional solar panels use crystalline silicon wafers.

According to Alan Delahoy, vice president of research, Energy Photovoltaics creates modules by coating glass with a thin film, about 400 nm thick, or hundreds of times thinner than the usual crystalline wafer, which is about 300 microns thick. The company can coat as many as 48 pieces of glass at a time, Delahoy said. He estimated that advantages in the design and the process cut the cost of manufacture in half.

Most of the product shipped to SMUD so far has come from EPV's factory in Lawrenceville. The company has a new, larger factory in Budapest, where it operates as DunaSolar. There are plans for another site in SMUD's hometown of Sacramento, where the operating name will be CalSolar.

Delahoy said EPV's lab is working on another thin film, using copper, indium, gallium, and selenium. The National Renewable Energy Laboratory in Golden, Colo., set a record last December for electricity conversion with a photovoltaic cell combining those elements. The NREL's thin film cell converted sunlight into electricity with 18.8 percent efficiency.


Dual-Purpose Shingles

The photovoltaic roofing consists of dual-purpose shingles: They keep the rain out and also contain a material that generates electricity from sunlight. Marketed under the brand name Sunslates, they generate 10 W per square foot and, under SMUD's program, a portion of the roof is covered with enough of them to generate between 2 and 4 kW The rest of the roof is weatherproofed conventionally.

Eklof said SMUD has installed Sunslates on the roofs of four model homes so far under a pilot program. She said a few reroofs of occupied homes are in development at the 1998 price of $2.23 a watt for the active portion of the roof. The photovoltaic roofing, supplied by Atlantis Energy Inc. of Colfax, Calif., replaces panels with sleek tiles, not unlike slate or asphalt.

In the roofing tile, six photovoltaic cells are connected with fine metal ribbons and attached to a concrete and fiber backplate that has been coated with conductive- metal. The result is a roof tile that is approximately the same thickness as conventional asphalt roofing. The tempered glass tiles have been documented to withstand temperatures ranging from minus 23° to 166° F, and winds in excess of 125 mph.

A similar product is in development at EPV, which at present makes solar power modules. According to the company's director of international marketing, Eva Csige, EPV has retained an outside firm that is working on a design to apply the company's technology to a photovoltaic shingle.

SMUD has a history of using alternative energy. It maintains several solar power plants, the largest of which is a 10-year-old plant with four units turning out 2.7 MW at Rancho Seco, near a retired nuclear facility.

Creating Goodwill

The utility also produces solar energy in banks of panels on covers that it builds over parking lots. In a region that commonly has summer temperatures in triple digits, the goodwill created by the shade from those roofs is in itself a public relations coup for SMUD.

Sacramento's growing number of small roof top power plants help the utility meet its electricity demand at the peak hours between 11 a.m. and 2 p.m., because they are the same hours when the photovoltaic systems are producing excess power and sending it to the power grid. That additional power has led the utility to put off or avoid building more full-size plants.

The New York Power Authority, meanwhile, has solar power installations at 11 sites in New York City and Westchester County, and plans seven others, on Long Island, in Buffalo, and northwest of Albany, the state capital. The largest is a 330-kW system at New York City Transit's Gun Hill bus depot in the Bronx.

The Power Authority supplies more than one-quarter of New York State's electricity, directly serving government and business customers and selling it wholesale to municipal systems, rural cooperatives, and investor-owned utilities throughout the state. According to a spokesman, the Power Authority's primary market lies in New York's public sector. Currently, the NYP A isn't making money on its solar installations. Instead, they are intended to demonstrate "that the technology is here." And also to prove that solar power can work in a climate like New York's, which gets perhaps half as much sunlight as the Southwestern states.

At present, NYPA puts the cost of installing solar power equipment at about $8,000 per kilowatt. The authority estimates that, with 20-year financing and the agency's bond interest rate, solar power costs NYPA about twice as much as electricity generated by more conventional means. In other words, solar power in New York at current prices carries a 40-year payback.

NYPA expects costs to drop as technology develops and the volume of installations increases. When that happens, power bills at schools, libraries, and other public buildings, and the tax money needed to pay them, may be reduced by the addition of solar power.

Each job goes out to bid separately, said Lumas Kendrick, the research engineer for the solar project. NYPA has no long-term primary supplier as SMUD does. But, according to officials at the agency, that is part of the learning process, which is the value of the program so far.

The Power Authority has said that the experience it receives by installing various systems will prove very valuable when manufacturing and market influences drive prices down, and solar power becomes a profitable enterprise for the agency.


Unexpected Challenges

In the course of its program, the authority has run into some engineering challenges it didn't expect. It lost 30 panels to high winds, for instance, at its second-largest installation, a 1l0-kW system at the Westchester County Wastewater Treatment Plant in Yonkers. The authority's president, Eugene Zeltmann, said of the incident in a speech last fall, "Even though the broken panels had to be replaced, we learned a valuable lesson on how to site and install PV systems."

A 36-kW system at a composting facility on Rikers Island in New York City was installed in 1996. The authority found that the escaping gases caused equipment to rust faster than at other sites. The NYPA plans to put housings over sensitive parts to shield them from condensation, according to Kendrick.

NYPA's solar energy installations generate a portion of the electricity needs of a building. Zeltmann said that the Gun Hill installation at peak output is able to meet half the electricity needs of the bus depot.

The Gun Hill depot site generates electricity worth about $2,500 a month for the city's transit authority, and the use of that much solar power keeps an estimated 600,000 1bs. of carbon dioxide, 1,200 lbs. of NO x' and 400 lbs. of particulates out of the air each year.

The authority has placed 6- to 8-kW solar generators at some public schools, and is working with district officials in the state to add more.