CHARACTERISTICS

Solar cells are thin wafers of silicon or other semi-conductor material that create an electric current when sunlight strikes the semiconductor material. When a number of solar cells are mounted on a surface and are wired together in series, they become a solar module, the building block of a photovoltaic (PV) system. Current commercial PV devices have a maximum conversion efficiency of about 15%. Direct sunlight as well as diffuse light scattered by clouds or humidity may still be able to generate electricity, making PV an option in warm and in cool climates. PV is by nature an intermittent resource, but where it matches daytime power peaks, it may be economic for utility applications. Also, the solar PV module's relatively high initial cost (currently ~$5/watt) is offset by a very long life (as many as 30 years) and relatively low maintenance requirements.

PVs produce no net emissions, although some toxic chemicals are used to produce PV systems. Where PVs are used for baseload or peaking power, fossil-fuel generated electricity is avoided.

PV modules can be used without moving parts; their support structures can be fixed in place, or designed to track the sun across the sky. Large-scale photovoltaic power plants, consisting of many PV arrays installed together, can prove useful to utilities for many reasons. Utilities can build PV plants much more quickly than they can build conventional power plants because the arrays themselves are easy to install and connect together. Also, because siting PV arrays is much easier than siting conventional power plants, utilities can locate PV plants where they are most needed in the grid. Finally, unlike conventional power plants, PV plants can be expanded incrementally as consumer demand increases. New developments include increasing production capacity as well as increasing efficiencies of the technologies, helping to reduce costs.

SIZE:
Modules range from a few watts to multi-MW. For power generation, modules can be combined to produce 5-10 MW_e or larger.

FEATURES:
Maximum operating efficiency 15% (sunlight-to-electricity); average efficiency 10%. Systems using trackers that follow the sun receive about 33% more sunlight than fixed arrays.

COST:
$6,000-20,000/kW for systems of which the module costs ~$5,000/kW, although expectations are that cost will decrease to $1,000/kWh by 2005-2015 and as low as $700-800/kW by 2020-2030. PV is competitive as a stand-alone power source in areas remote from electric utility grids. The levelized cost for large PV systems (>1kW) is $0.25-.50/kWh, making PV cost-effective for residential customers more than a quarter mile (0.4 km) from the grid.

CURRENT USAGE:
About 150 MW of PV is shipped every year; more than 200,000 residential and commercial buildings use PV systems. PV demand is increasing at a rate of 15-20% each year.⁵

POTENTIAL USAGE:
Solar insolation sufficient for PV exists in areas of virtually every country in the world.

ISSUES ASSOCIATED WITH IMPLEMENTING ACTION

• Solar insolation varies geographically.
• Once PV equipment is purchased and installed, negligible additional costs are incurred. Fuel costs are zero, so PV systems may be more economical over a project lifetime. PV is becoming the power supply of choice for remote and small-power, DC applications of 100 W or less.
• Cost of photovoltaic-produced electricity varies with atmospheric conditions—photovoltaic cells may lose 0.5% of their production efficiency for each degree Celsius above their rated temperature.
• PV cannot provide continuous power without energy storage systems. Because of its variable nature (due to the variance of sunlight), utility planners must treat a PV power plant differently than they would treat a conventional plant.

CLIMATE CHANGE IMPACT

EMISSION EFFECT:
    

CONDITIONS FOR EMISSIONS MITIGATION:

• In some applications, back-up power generators (e.g., diesel) may be necessary; where back-up power is necessary, some emissions would be produced.

EMISSION ESTIMATE:
No direct GHG emissions.

COST-EFFECTIVENESS:
$26-400/ton of CO₂ avoided (net), depending on alternate fuel sources.

SECONDARY EFFECTS:
Produces no air pollutants although some systems involve the use of toxic materials which can pose risks in manufacture, use and disposal.

RESOURCES

• The U.S. Department of Energy is sponsoring three commercialization efforts for utility-scale operation of PV:
  1. The Utility PhotoVoltaic Group, a collaborative effort of U.S. utilities and the U.S. DOE is designed to accelerate the use of cost-effective small-scale and emerging large-scale applications of PV for the benefit of electric utilities and their customers.
  2. TEAM-UP Utility/DOE PV Commercialization Program
  3. Photovoltaics for Utility Scale Applications(PVUSA) is a cooperative agreement between DOE and utilities to operate three pilot test stations. This allows participating utilities to specify, purchase, test, and evaluate utility-ready photovoltaic equipment. The agreement is helping prepare both utilities and the PV industry for quantity installations.
• The International Finance Corporation (IFC) has established the Photovoltaic Market Transformation Initiative, a fund of $60 million contributed by the Global Environment Facility, to invest from $1-5 million in large-scale expansion projects for PV in a select number of eligible countries.
• The GEF has established the PV Green Carrot Program to cover part of the risks of PV manufacturing and marketing scale-up. This program offers a cash award to manufacturers of efficient low-cost PV technologies.
• Zweibel, K. 1990. Harnessing Solar Power: The Photovoltaics Challenge, Plenum Publishing Corporation, New York (US)
• PV Discussion Group online, http://aurora.crest.org/resources/emlists/pvusers/

CONTACTS

International Finance Corporation
Dana Younger
IFC GEF Coordinator
Environment Division
Technical & Environment Department
Washington, DC
Tel: (202) 473-4779
Fax: (202) 334-9705
DYounger@WorldBank.org
http://www.ifc.org

National Renewable Energy Laboratory
Golden, CO
Tel: (303) 275-3000
http://www.nrel.gov

Solar Energy Industry Association
Scott Sklar
Executive Director
Washington, DC
Tel: (202) 383-2600
http://www.seia.org

Utility PhotoVoltaic Group
Matt Cheney, Director
Washington, DC
Tel: (202) 884-0689
Fax: (202) 223-5537
mcheney@ttcorp.com
http://www.upvg.org

World Bank
Charles Feinstein
Senior Environmental Specialist
Global Environment Division
Environment Department
Washington, DC
Tel: (202) 473-2896
Fax: (202) 522-3256
Cfeinstein@WorldBank.org
http://www.worldbank.org