PV Gap

Naomi Said:

What are solar photovoltaic panels?

We Answered:

Photovoltaic panels (PV) captures the sun’s energy and converts it into electricity. Solar cells are made of silicon, a naturally occurring element in abundance within the earth’s crust. The silicon is processed into semi-conductors, which are called cells, and are electrically conductive in the presence of light (photovoltaic).

Cells operate at a low voltage and modules are constructed with many cells connected together in series, within a protective frame. Modules are then connected in series or parallel (to give the desired voltage and current) into a solar array. The array is connected to an inverter, which converts the DC voltage from the solar panels into AC voltage, to power your home and allow the electricity to be exported to the grid.

Kevin Said:

Where can one obtain components to build photovoltaic solar panels.?

We Answered:

I thought I read somewhere that you can get them at Costco. Go online. Hit the yellow pages and see what turns up. Go to Home shows and you might be able to get that answer that you really want.

Earl Said:

Are photovoltaic solar panels economical. I live in the San Francisco Bay area.?

We Answered:

Photovaltaics are very economical (the panels to be purchased), yet everything associated with the storage of energy is through the roof! You will have to purchase batteries for the storage of your energy, and an inverter that takes the DC and converts it into AC for home use.
Batteries lose their life after a period of time, and you have to purchase new ones over a period of time. Inverters replace DC's 100% energy into around 30-40%, so this is not a very efficient means to pull in energy into the home.

I would suggest purchasing a copy of "Home Power" magazine. It is around $7.00 per issue, and is very insightful. Being in San Francisco, you may want to look into passive energy means, such as a "black box" water heater for the roof.

Donald Said:

What is the difference between Photovoltaic Panels and Solar Panels?

We Answered:

Solar panels collect energy from the sun and then provide it to a system that typically concentrates it.

Solar energy comes to us in the form of heat and light. Photovoltaic panels take the light energy from the sun and convert it to electricity. Although the maximum efficiency is around 42% in the lab most commercial models you will see are from 8 to 22% efficient. Adding collectors together concentrates this energy into usable amounts.

Solar thermal panels are from 60 to 80% efficient. They come in many different types and collect the heat energy from the sun. That heat may then be stored in some form of thermal mass where it becomes concentrated sufficiently to be used. Solar thermal panels can be used to heat a medium. This can be a phase change material, air, or water. Solar thermal air panels are cheap to make and offer a quick pay back period. Solar thermal panels for some heating and hot water systems circulate water. Vacuum tube collectors are solar thermal "panels" that may heat water directly or a phase change materials. They can operate better in cloudy and colder weather with more efficiency. Air and water panels are often called "flat panels" as a way to contrast them with vacuum tube collectors.

Solar thermal panels often lead to some form of energy storage called thermal mass (water tanks, phase change materials, masonry walls and rocks.) Photovoltaic panels make electricity that is stored in batteries, used or sent to the general grid.

Panels are only one way to collect solar thermal energy. Other types of "collectors" are used commercially and are often called simply solar "concentrators." Some are called parabolic trough collectors and parabolic dish collectors.

Max Said:

why are photovoltaic solar panels "relatively inefficient"?

We Answered:

The wavelength of light needs to be closely matched to the bandgap of the semiconductor material. Some newer, multilayer photovoltaic cells are more efficient because each layer absorbs photons of a different wavelength. They already use antilreflective coatings to reduce reflected light.