Utilization Factor In solar panels

[bluffreggie]

Hey all.

Im currently doing some research into renewable's and have come across a value known as U whose units are kWh/m^2.

The comment next to it simply states it as the utilzation factor. Now I've looked in several books and of course ovia the internet but i can't seem to find a meaning anywhere.

It is in regards to solar power. I need to find out firstly what it is and secondly how it can be calculated. Anyone out there have any idea?

Kind Regards

 

[d2blake]

Where did you come across utilization factor? In regards to solar, I know this as the ratio of DC solar panels to AC inverter rating.
As for KWh/m^2, this is what is used to calculate the efficiency of a solar panel. Every location is different but for testing, 1KWh/m^2 potential solar energy is used. A solar panel is exposed to this quantity of energy and the amount of energy captured, along with the panels size, get its efficiency.
ie: if a solar panel is 1m^2 in size and captures 0.2KW over an hour when exposed to 1kwh/m^2, it is 20% efficient.

 

[russ_watters]

Sorry I missed this thread before: I'm pretty sure utilization factor would be the total amount of solar radiation to hit a spot on Earth in a year.

 

[Topher925]

The utilization factor is a ratio of the maximum load to the rated capacity of the solar panels. However, this is a ratio and does not have units of kWh/m^2.

I'm guessing that the author is referring to how much energy is generated by the panels per square meter on an annual basis.

I'm pretty sure utilization factor would be the total amount of solar radiation to hit a spot on Earth in a year.

I've always known this to be the capacity factor.

 

[russ_watters]

I was actually looking at the units more than the term (about which we agree). Googling the term doesn't give a lot of relevant hits, so I was thinking it isn't an industry standard term.

Capacity factor on the other hand is a standard term and is what you are describing as utilization factor!

The net capacity factor of a power plant is the ratio of the actual output of a power plant over a period of time and its output if it had operated at full nameplate capacity the entire time. To calculate the capacity factor, total energy the plant produced during a period of time and divide by the energy the plant would have produced at full capacity. Capacity factors vary greatly depending on the type of fuel that is used and the design of the plant. The capacity factor should not be confused with the availability factor, capacity credit (firm capacity) or with efficiency.

http://en.wikipedia.org/wiki/Capacity_factor

The two would be related, of course. To get kwh/m^2, you multiply the capacity factor by the peak solar radiation.

 

[thopsy]

The utilization factor, U, is a very useful dimensionless parameter for designing solar thermal collectors. It should be dimensionless. Are you sure it was not multiplied by an Irradiation value (i.e. yearly irradiation), to give kWh/m2?

A good reference is Duffie and Beckman's "Solar Engineering of Thermal Processes"