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Solar GainsPUBLIC ACCESS

Photovoltaic Technology is Growing More Popular as a Means of Distributed Generation and as a Source of Power for the Unwired World.

[+] Author Notes

Barbara Wolcott, a frequent contributor to Mechanical Engineering, is a freelance writer based ill Sail Luis Obispo, Calif.

Mechanical Engineering 123(10), 66-69 (Oct 01, 2001) (4 pages) doi:10.1115/1.2001-OCT-4

This article reviews that photovoltaic technology is growing more popular as a means of distributed generation and as a source of power for the world. Net metering now available in nearly every state in the Union is a strong incentive for this kind of alternative energy because it allows excess power generated during peak hours of sunshine to reverse an electric meter, selling power back to the utility. In addition, many states encourage solar power installations by offering a 50 percent subsidy, making the net cost to an average home-owner about $5,000. Rural electrification through solar power is exemplified in Indonesia, a country of 17,000 islands, of which about 6000 are inhabited. Prior to 1991, more than 10,000 solar home systems were installed in the country, according to the World Energy Council in London. Since solar power generation peaks at the same time spot power prices spike, companies are looking very closely at comparative costs. Article In the United States, Solar power has long been regarded largely as a novelty or, at best, as a niche market. However, demand is rising for distributed power generation and the technology that produces it. That is evidenced by customers willing to make substantial investments in individual residential and business photovoltaic power systems. Net metering now available in nearly every state in the Union is a strong incentive for this kind of alternative energy because it allows excess power generated during peak hours of sunshine to reverse an electric meter, selling power back to the utility. In addition, many states encourage solar power installations by offering a 50 percent subsidy, making the net cost to an average homeowner about$5,000.

Some experts are predicting that photovoltaic technology may contribute as much as 10 percent of the country’s peak power generation 20 years from now. Solar power enthusiasts feel strongly that it will make an even greater impact. Gary Schmitz, a spokesman for the National Renewable Energy Laboratory in Golden, Colo., said that last year PV power grew by 30 percent in the United States. Elsewhere in the world, PV power increased by 40 percent.

A number of influences, from the need for reliable backup power to rising electricity rates, have boosted the demand for solar power systems. In many states, reverse metering simplifies the sale of excess power back to the utility.

Industrialized countries are installing solar electric generation to curb some of their carbon emissions and other undesirable byproducts of combustion. However, it is in the developing world where solar has really shown its power to effect change.

Germany is planning to have 350 megawatts of solar power online by 2003. It installed 48 MW in 2000 and has 95 MW more to go. Solar will contribute between 3 and 4 percent of the country’s total installed generating capacity, which exceeds 10,000 MW.

Increasing solar power production is part of Germany’s effort to reduce its greenhouse gas emissions by 21 percent by 2010. To reach this goal, new sustainable power resources must grow fivefold.

On the other side of the world, Japan currently has 192 MW, 80 of which were installed in 1999, the country’s peak year of installation.

In March 2000, Sanyo Electric Co. reported plans for a 3.4-MW solar power generation plant, called Mega Solar. The new power facility is under construction, around an existing Sanyo factory in Gifu, and is scheduled for completion by 2004. It will cost about 6 billion yen, or a little more than $50 million. It is planned to be as much show-place as power plant, so its cost is not directly comparable to a more utilitarian facility of comparable capacity. 13-MW Sun Spot in Spain What may be the world’s largest solar installation, meanwhile, will be constructed in Murcia, Spain, as a joint venture between that municipality and a Newark, Del., company, AstroPower Inc. The American corporation will supply enough photovoltaics to power a 13MW plant, which the company says will be larger than any currently in operation. The plant is expected to cost$65 million to build and take two years to complete. It will provide 4 percent of the total peak load in the region when it goes online.

Meanwhile, products from United Solar PV of Troy, Mich., marketed through Solar Energy Uganda Ltd., are making a difference in a rural African economy.

In 1997, a retired Episcopal Bishop, Alden Hathaway, initiated the electrification of poor villages in Uganda. When Hathaway visited the country to tour a new orphanage—funded in part by money he had raised in the United States—he realized that without power the woman who tended the babies at night would have to do so in the dark. Hathaway called his son, an electrical engineer, and asked him to design a system for the orphanage.

Soon after that system was working, other church officials in Uganda contacted Hathaway, who now lives on an island off the state of Maine, about electrifying churches, schools, clinics, and homes in outlying areas. The kerosene lanterns used in the backcountry provide poor lighting, threaten health, and pose a danger of fire.

The Anglican Church in Uganda established a diocesan partnership that subsidized solar power installations, half by charitable gifts from the United States and half from Ugandan churches. The project, Solar Light for Churches of Africa, has installed more than a thousand units.

The Power of Four Lights

Solar power in Uganda is seen as providing a 100-year jump in the development of rural villages. In the first year of the church project, one endeavor put four high-efficiency fluorescent lights powered by a solar cell and a battery into the home of a poor pastor.

Sanyo Electric's Mega Solar is a 3.4-MW solar power plant that will be built around the company's semiconductor factory in Gifu, Japan. The blue swaths in this computer rendering represent photovoltaic arrays.

His wife took one of the lights and put it in the room where she raised chickens, a common practice on U.S. farms, and doubled the egg production. That gave the couple a little extra money to invest in a pig and other animals, which in turn encouraged them to study how to apply modern agriculture principles where they lived.

Bishop Hathaway said, “Last summer, they had a foundation constructed for a school to accommodate agriculture extension education. This year, we put solar into that school, which is now completed, and I passed out certificates to those adults graduating from the school.”

That all started with four lights.

Rural electrification through solar power is exemplified in Indonesia, a country of 17,000 islands, of which about 6,000 are inhabited. Prior to 1991, more than 10,000 solar home systems were installed in the country, according to the World Energy Council in London. A program begun in 1992 aims to have one million rural homes solar powered by 2005, and is financed by a Global Environment Facility Trust Fund grant approved by the World Bank. It is the largest solar home system initiative in the world and will make solar energy affordable to 35 million rural Indonesians.

The demand for photovoltaic systems has increased markedly in the United States, as well, and according to some forecasts is expected to continue to do so.

United Solar Systems, jointly owned by Energy Conversion Devices Inc. of the United States and Bekaert ECD Solar Systems LLC of Belgium, makes thin-film photovoltaics in a roll-to-roll process much like the manufacture of newsprint or photographic film.

The method was developed in collaboration with a program funded by the U.S. Department of Energy in the mid-1990s.

United Solar’s thin film contains three active solar cell layers, each tuned to different wavelengths of the solar spectrum to convert sunlight into electricity. That results in an energy conversion efficiency of about 10 percent for a prototype module and 7.6 percent for cells produced in commercial quantities.

Single crystal photovoltaics operate at an efficiency of 12 to 14 percent, according to the DOE. While the efficiency is less for film than for conventional PVs, the reduction of cost plays an important part in the promotion of thin-film solar technology.

According to a schematic on the company’s Web site, the sandwich of film layers is less than a micrometer thick. It sits on a stainless steel substrate that is 125 pm thick. The technology was originally developed by Energy Conversion Devices, the U.S. parent company, which is also involved in the development of fuel cells and various battery technologies.

About a year ago, United Solar decided to increase capacity because so many people were beginning to look seriously at PV power. With its annual capacity of 5 MW, the company elected to build a machine capable of an annual capacity of 25 MW.

When the company’s executives took that step, they weren’t sure how fast the market would grow. Bob Stempel, a former chief executive of General Motors and now a principal at United Solar, said, “Our question now is how quick do we get the machine done.”

A California solar power system designer, John Ewan, is currently working overtime to fill the demand for solar power systems, most of which are grid-tied systems without batteries.

Ewan said, “Business owners express more of an interest in backup power systems, so that if a rotating outage hits, they can keep working.” Ewan’s company is installing four systems a month, and the wait for new equipment is getting longer each week as manufacturers work to fill the orders pouring in.

The cost to power customers also can be translated into monthly dollars. Bob Johnson, an analyst at Strategies Unlimited in Northern California, said his home electric use puts him in the fourth of five accounting tiers used by Pacific Gas & Electric to compute billing. The more electricity a customer draws, the higher the rate per kilowatt-hour. The minimum, or baseline level, charge is 12 cents per kilowatt-hour, and Johnson, on the fourth tier, is paying 19 cents for usage over the baseline.

Solar-powered pumps from Grundfos of Denmark raise water in a Namibian wildlife preserve. The photo is a composite. People and rhinos don’t mix.

With a solar power system he intends to have installed at his home, Johnson expects that his electric bill, now more than $100 a month, will be reduced by a considerable amount. Aided by a California state subsidy for capital costs, he will pay about$30 a month for the system.

His home will remain connected to the grid. When his solar array generates more power than the Johnson home needs, net metering will accrue credit on his utility bill.

In California, the Sacramento Municipal Utility District has invested heavily in solar installations in recent years. It has subsidized installations on private homes and has installed arrays on the roofs of parking garages. Rising demand for PV products has increased the time to schedule installations from two weeks to six.

The Los Angeles Department of Water and Power has begun its own program of subsidies for solar installations. Last February, LADWP named Siemens Solar Industries L.P. of Camarillo, Calif., the first recipient of a financial incentive program to encourage local production and use of photovoltaic technology. Los Angeles Mayor Richard Riordan said, “It has never been easier, or more affordable, to plug into the sun.” The city’s financial incentive program offers customers outside the city limits an opportunity to lower the cost of a PV system by $3 per watt, and those within the limits by$5 per watt. The maximum benefit is $50,000 for a residential site and$1 million for commercial sites.

The department serves 3.8 million people and has a goal of installing 100,000 solar roof systems by 2010. The utility is putting PV panels on commercial buildings and parking garage rooftops in systems that cover from 5,000 to 15,000 square feet. One such system produces 550 kW of power. Other systems are going up on the sides of large commercial buildings in a system of cladding used by architects to simultaneously provide exterior walls and produce power. The region expects to have 7.5 MW capacity by 2003.

Short- and Long-term Costs

Since solar power generation peaks at the same time spot power prices spike, companies are looking very closely at comparative costs.

According to Terry Peterson, manager of solar power and green power marketing at the Electric Power Research Institute in Palo Alto, Calif., it is difficult to compare the cost of power produced by a natural gas facility and that of photovoltaics.

United Solar's factory in Troy, Mich., turns out flexible film solar cells in a reel-to-reel process. The company is investing in a sixfold expansion of its production capacity, to 30 MW a year.

The capital cost of a natural gas plant is about $500 per kilowatt, compared with about$7,000 at a solar plant. However, the continuing cost of gas eliminates some of the difference over the long term. The cost of fuel to the solar plant is zero because it produces power with free sunlight.

Peterson said that, if the recent increase in the cost of natural gas of the last year is factored in, solar comes out considerably better, at least in California: 8 to 20 cents per kilowatt-hour, compared with 30 cents per kilowatt-hour for gas.

In 2000, a large group of solar interests, from manufacturers and installers to major academic institutions, U.S. national laboratories, and the U.S. Department of Energy, met twice to envision the next 20 years of PV power. Those meetings produced a white paper titled “The U.S. Photovoltaic Industry Roadmap,” which projects that solar generating systems will contribute 10 percent of the U.S. peak power generation by the year 2020, an energy equivalent of 180 million barrels of oil at that time.

The paper goes on to point out that since solar power is most available during the time of greatest use—at midday'—it mitigates the risk of fuel price volatility and improves grid reliability, thus guaranteeing a more stable energy economy. The group advocates net metering, where PV power runs a grid-connected meter backward during time of excess generation, and hopes to see that policy go into effect in all 50 states.

Another suggestion is that solar power producers receive credit for offsetting emissions in a kind of “urban airshed” program.

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