PV Gap

Eddie Said:

solar power efficiency?

We Answered:

The photovoltaic efficiency should be lower than 20% for a practical system. The most expensive widely-distributed cells, Sunpower, have an efficiency of maybe 22%. Put put them under glass in a practical frame, and it's down to 19%. These are $7 a watt type panels. The $4 a watt panels that most folks install are 13-15% efficient, after they're put in a practical frame. The 36% type of cells from places like Spectrolab are $250 a watt - not for homeowners.

Intermittency efficiency looks good for a place like California. What you're saying by that 20% is that you're expecting 24 x .2 = 4.8 equivalent peak-sun hours year round. This number should be higher in Southern Cal or Arizona, lower in Michigan. Really, this number can be the normalization factor that takes into account all the other aspects of the area - atmospheric transparency due to altitude, pollution, operating temperature.

For storage efficiency, I think you can get better than 25%. I'd use 70% - 80% for the battery, and 95% for the inverter, if any.

Now, for the real-life number from our system (see link below):
6556 (kWh/yr) / 8765 (hours/yr) / 12.5 (square meters of panel) = 60W / m^2, approximately. We are grid-tied, no battery losses.

Vera Said:

For Solar, what kind of Degree is required?

We Answered:

you may want to look into electrical engineering because efficiency may lie in how they are built, or chemical/materials engineering because a new chemical or material may capture the light better, giving more electricity.