Can a Solar Power Panel be effective if you attach it to the inside of a window instead of putting it outside?

Image by eastpole
Today was a sunny day, and I logged the output of some local solar energy facilities.

See a similar graph for a cloudy day (with a different scale.)

The vertical axis here is the amount of power that sunshine drops onto each square meter of earth. Note that solar panels collecting light to make electricity are about 16% efficient, so if 1000 W are coming into a 1 m^2 array, you can expect about 160 W at best (when the sun is highest.) For example, check out BP Solar’s BP SX 160 panels — 1.2 m^2, and offering 160 W.

A solar water heater is more efficient, so for a pool, hotel, laundromat, or hospital that needs hot water, a solar heater is a great deal.

This graph above is as close as I’ve seen to an ideal curve, which means today was nearly cloudless. (It looks like there were some clouds in Woodbridge around 3pm.)

Note the slow start indicated at the solar water heater on Main St. (purple squares). Why? I’m not sure, but it’s consistent. This may be a building or tree in the way (to the East), shading the collector in the early morning.

I can’t explain why the Main St. sensor gives consistently lower insolation values all afternoon.

If subsequent days give me interesting clues I’ll add more. I should also estimate the area under the curve and give an estimate of the kWh that would be produced on a day like this.

Note that kWh produced per kW capacity of the array is not just the area under the curve. The 14% to 18% efficiency of the solar panel has to be factored in.

Based on a very small sample, it looks like this particular May sunny day yielded about 6.6 kWh for each kW of installed solar electric capacity.

Additional thoughts:
Temperature: Low 3.7 C, high 15.9 C.
Visibility: 21.4 km all day.
Solar noon
day duration: 14:36
Sunrise: 5:56
Sunset: 20:32
solar zenith angle
Ravina Project produced 9.8 kWh with a 1.5 kW array, so 6.5 kWh/kW(p)
Carmanah reports 170.5 for Hershey Centre, with an array rated for 25 kW, so 6.8 kWh/kW(p)

Note that a rough but reliable rule of thumb in the solar energy industry here says that at Toronto’s latitude, 1 kW of panel yields about 1000 kWh of electricity in a year*. The average on-grid home uses about 11000 kWh in a year.

Residentially, we pay our utilities around CAD $ 0.10 for each kWh of energy we buy, in mid 2009.

Up-front cost to install rooftop solar photovoltaic power is about CAD ,000 / kW* . Unlike most US states, we have very little in the way of rebates, but our local utilities must buy power from small solar producers at an attractive rate.

(*) These generalities are "true" but they lack an explanation of range or variability — I’d love to know how much extra power you get in a year that’s sunnier than 95% of years on record. And I’d love to know how wide the range of installed costs can be. Anyone?

Question by Jesus: Can a Solar Power Panel be effective if you attach it to the inside of a window instead of putting it outside?
Can a Solar Power Panel be effective if you attach it to the inside of a window instead of putting it outside? Like if you just put it right against a window inside your home facing out towards the sun, would it absorb sun light just fine or does it have to be outside taking direct sun light to be effective?

Can you help? Leave your own answer in the comments!