Solar PV
Photovoltaics (PV) use solar cells to convert solar energy into electricity. When sunlight hits the semiconductors (solids, such as silicon, that can conduct electricity) in the solar cells, an electrical charge is generated. The different types of PV and accompaniments include:
- Mounted PV: PV panels that are mounted on the roof or walls of building; they are often made of silicon.
- Thin-film PV : PV cells that are integrated into roofing materials; they are light, flexible, thin, and durable and made of amorphous silicon, cadmium telluride, or copper indium (gallium arsenide).
- Building Integrated PV: BIPV integrates solar cells (often made from amorphous silicon) into glass- often used in building walls, windows, and skylights.
- Tiles: Powerlight manufactures tiles that can be integrated into a roof like roofing tiles.
- Electrochemical Solar Cells: (in development) The active components are liquid and use a dye sensitizer to absorb light; the simple construction and cheap materials might make them an inexpensive option.
- Flexible PV: (in development) Konarka is using technology to develop flexible solar that can be used on many different surfaces.
- PV Power Stations: Large power plants that use PV exist in many countries; the largest is a 20 MW station in Spain.
- Heliostats: Heliostats track the sun to increase the amount of sunlight available to the PV system.
- Concentrators: Concentrators use lenses to concentrate the sun on to PV cells, increasing efficiency.
Fact Sheets
Interested in installing PV at Harvard? Our pv fact sheet and solar glass fact sheet goes through the basics of what you need to know.
University Case Studies
Many universities have installed PV with systems ranging in capacity from 0.15 kW to 2,683 kW (as of May 2008). Check the Association for Advancement of Sustainability in Higher Education (AASHE) for the most up-to-date list.
Photovoltaics at Harvard
1. HBS Shad Hall PV- 36 kW, 192 panels. Installed in 2003.
2. Harvard Forest PV- 10.2 kW, 60 panels. Installed in 2007.
3. Science Center lamp- 2 kWh of electricity per day. Installed in 2006.
4. Science Center PV- 10.8 kW. Installed in 2007.
Financing Options for Harvard
1. Power Purchase Agreements (Third Party Financing):
Agreement with a third party who funds the project and sells the electricity back to the host. The third party assumes all risks, maintenance, and costs associated with the project. Third party can take advantage of tax benefits that universities cannot. Power purchase agreements (PPAs) are beneficial for projects with a long payback. If a PPA sells the RECs, the school would not be able to claim the emissions reductions for their greenhouse gas inventory.
Tax benefits that PPAs can take advantage of include:
Federal Tax Credit: offers a rebate of up to 30% off PV. After 2008, the rebate will be 10% unless it is extended by Congress. Expires 12/31/08.
Federal Production Tax Credit: 1.5 cents/kWh credit (valued at 1.9 cents due to inflation) for the first 10 years of a renewable energy facilities operation. Expires 12/31/08. 
2. Renewable Energy Credits (RECs):
RECs (also known as green tags) are the property rights to the environmental benefits associated with generating electricity from renewable energy sources. If the RECs are sold, the emissions reductions cannot be counted towards the generator’s greenhouse gas inventory. One option in Massachusetts is the Mass Energy Renewable Energy Certificate Incentive which purchases PV RECs for $0.06/kWh.
3. Commonwealth Solar Initiative:
This new, four year, $68 million Massachusetts fund replaces the Massachusetts Technology Collaborative’s Small Renewable Initiative rebate and Large Onsite Renewable Initiatives grant for PV. Rebates range in size, from $3.25 per watt for small systems to $1.25 per watt for systems over 200 kW.
4. Net Metering:
In Massachusetts, systems that are 60 kW or less can sell excess electricity back to the grid and receive a credit from the electric company.
LEED
Buildings can obtain LEED points for using renewable energy on-site. More information is available on our Renewable Energy and LEED page.
Sources/More Information
Energy Payback: Clean Energy from PV
Solar Energy Industries Association
Massachusetts Technology Collaborative
National Renewable Energy Laboratory: Thin Film Partnership Program
MTC MA Solar Power Performance