23.8 kW Photovoltaic rooftop panels produce part of the electricity for Sophia Gordon Hall (funded by a grant from the Massachusetts Technology Collaborative with matching funds from Tufts).
The building is modeled to use approximately 476,000 kWh (not including plug loads for appliances and electronic equipement). The PV panels on Sophia Gordon’s roof will produce about 25,000 kWh per year. In comparison, a base case building (a conventional building meeting MA code) would have used close to 700, 000 kWh.
In the rare event that the generation of electricity exeeds that consumed by the building, the electricity will be used within the Tufts campus.
How do Photovoltaics Work?
Photovoltaics is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity.
In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications.
Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool.