Photovoltaics - A Clean Energy Alternative

Photovoltaic power systems are a relatively clean energy alternative to fossil fuels and nuclear power. Pollution from photovoltaics is limited to the initial manufacturing and deployment phase, once in place there are basically no environmental impacts. The use of photovoltaics (solar cells) has expanded from high end, high cost applications to low cost, remote location electrification projects. Photovoltaics have been used on spacecraft for decades. The International Space Station (ISS) has large photovoltaic panels which provide the electrical power for all operations on board the space station.

Cost analysis has been done (5) by the World Bank organization. For 8 watt fluorescent lights generating 400 lumens, a $500 Solar Home System (SHS) provides light at an average cost of $7.15 per million lumen-hours. In the case of a diesel generator powering 60 watts of incandescent lights the cost is estimated to be $28.77 per million lumen hours. In the case of kerosene lamps it is estimated that the price would be near $400 per million lumen-hours. Environmentally there are many benefits which can be derived from the use of photovoltaics. Photovoltaics don't emit green house gases. In round numbers, a typical 50W PV Solar Home System offsets the emissions of about 400 kg of CO2 on a yearly basis(1). Another calculation is provided in reference (5), where it is stated that for a 20 year life of PV lighting systems installed in 1000 homes, at least 6000 tons of CO₂ will be displaced.

A typical photovoltaic system is composed of the photovoltaic cells mounted in some kind of a weather resistant panel, mounting hardware to mount the cells on a roof or on the top of a pole, connecting wiring, storage batteries and a power inverter to convert the direct current output from the photovoltaics to alternating current for devices which need AC current. The cost of photovoltaic power has dropped to a level where it can be estimated that the cost is near 25 cents per kilowatt-hour(2). This is between 2 and 5 times the cost of electricity purchased off the power grid here in the United States. The National Database of State Incentives for Renewable Energy (DSIRE) is a website that lists incentives available to help pay for the installation of a solar electric system on your home(8).

In the United States, the U.S. Department of Energy has been involved in a program known as TEAM-UP, or Technology Experience to Accelerate Markets in Utility Photovoltaics. The program has a goal of 50 megawatts and has already contracted for 8 megawatts of grid-connected PV, with supplier buy-downs and consumer rebates between $2 - $4 per watt(2).

Reference number (2) gives some estimates for the cost of installing a solar system on your home. A single photovoltaic panel with a built-in power inverter that produces 75 watts can cost around $900 installed, or $12 per watt. For a 2-kilowatt system the cost will range from $16,000 to $20,000 installed, or $8 to $10 per watt. In the case of a 5-kilowatt system, capable of powering most homes, costs can range from $30,000 to $40,000 installed, or $6 to $8 per watt.

The U.S. Department of Energy, Energy Efficiency and Renewable Energy, Solar Energy Technologies Program is there for you to familiarize yourself with the most up to date information about photovoltaics(9).

An important example of a commercial use of photovoltaics is the Mauna Lani Bay Hotel in Hawaii. The hotel installed PowerGuard brand insulating photovoltaic roofing tiles on their 10,000 square foot roof. The photovoltaic panels generate 75 net kilowatts of electricity. The hotel will save enough on electric bills to recover their investment in just 5 years(7).

Another commercial success story is that of a BP Amoco station in Chicago. At the corner of LaSalle and Ontario Streets in the heart of Chicago, on top of the pump-island canopy are 140 BP Solar Millennia thin-film PV modules. They generate about 6 kilowatts of electricity, accounting for 10% to 15% of the station's power needs. The system is connected directly to the local utility rather than to a storage battery, which reduces the station's demand for utility-supplied power, and thus, its utility bill. The modules are essentially maintenance-free and carry a 20-year warranty. BP Solar is installing similar solar-powered canopies at service stations in Illinois and throughout the United States(7).

The U.S. Fish and Wildlife Service needed a cleaner and quieter power source for a facility on an island 30 miles west of San Francisco, California, which is home to biologists, volunteers, sea lions, and thousands of birds. Before the 9.1-kilowatt hybrid system was installed, the staff had to run loud and expensive diesel generators during the day, which meant that they had no electricity after work. A quiet PV system from Applied Power Corporation generates electricity around the clock. Its industrial battery bank stores up to 3 days of energy, and a new, smaller generator serves as backup in case of heavy power use or extended periods of bad weather(7).

In conclusion, photovoltaic solar electricity systems are of great importance and may be the solution to the long term energy needs of the nation and the world.

(1) The World Bank - Rural and Renewable Energy Page

http://www.worldbank.org/html/fpd/energy/subenergy/solar/solar_pv.htm

(2) A Consumer's Guide to Buying a Solar Electric System

http://www.nrel.gov/ncpv/pdfs/26591.pdf

(3) National Renewable Energy Lab (NREL) - Better Buildings Series - Myths about Solar Electricity http://www.nrel.gov/docs/fy03osti/32529.pdf

(4) Oregon Department of Energy - Basics - Solar Electricity (Photovoltaics)

http://www.energy.state.or.us/renew/Solar/PV.htm

(5) The World Bank Group - Residential PV Applications

http://www.worldbank.org/html/fpd/energy/subenergy/solar/residential.htm

(6) State of Hawaii - Solar Electric (Photovoltaic) Energy Fact Sheet

http://www.state.hi.us/dbedt/ert/pv_hi.html

(7) Solar Energy Technologies Program: Why PV is Important to the Economy - http://www.eere.energy.gov/solar/to_economy.html

(8) National Database of State Incentives for Renewable Energy (DSIRE) http://www.dsireusa.org/

(9) U.S. Department of Energy, Energy Efficiency and Renewable Energy, Solar Energy Technologies Program - http://www.eere.energy.gov/solar/photovoltaics.html -