Hydro-electric plant 500KW FSBO…..
Thanks for adding a voice of experience to the conversation, silvervarg.
Silvervarg is correct; but, I think maybe still a bit generous with estimated outputs.
The output current of a PV array is directly related to irradiance and inversely related to cell temperature (effected by ambient temperature, wind speed, and irradiance).
Effective irradiance can be increased by reflectance from adjacent snow cover; BUT, remember that the incident angle of the radiation striking the PV array will be far from optimal, greatly reducing its impact. Thus, I think silvervarg's 1.5 multiplier is still too optimistic. In order to optimize performance, the array needs to aligned so the direct solar radiation hits the array at an incidence angle as close to 0-degrees (as perpendicular) as possible. Even still, unless you have a tracking array, you'll rarely achieve this level of perfect solar incidence angle. Thus, you will rarely have an electrical output that meets, let alone exceeds, the nameplate rating of your PV modules.
There is an advantage to be gained by reflectance off the snow; but, do not try to increase the irradiance on the array too much, using parabolic reflectors, or whatever. This will cause a temperature rise on the modules that can lead to damage. Additionally, as cell temperature rises, output voltage drops…ouch!
Solar absolutely will work in the north! Germany has the same solar-irradiance resource as Alaska, yet they are well ahead of the U.S. in kWhrs produced with solar PV.
Though any increased output is a plus when it comes to solar inputs, I think what hydro explained as a parabolic experience might have been what was going on. The lake reflected onto the east, then west valley in front of the house. Once snow hit the ground, triple the heat output. And, since solar panels are at the lowest angle at that time of year, they caught the most rays.
Good discussion and whenever I hear about solar panels in northern climates I have to say something on this effect. Maybe not 5 times the result, but definitely a plus.
I don't think solar rays bouncing off the snow is the dominant explanation for increased solar gain during winter months.
For my money, the answer lies in this chart, which is a typical representation of solar cell efficiency as a function of temperature.
As you can see, there's a very large effect.
So the combination of longer days plus cold weather are probably the strongest drivers of solar gain in the month of March for northern solar installations.
Snow might contribute a little bit, but the angle of incidence of light bouncing from snow I might suspect to be very suboptimal for much solar gain. Most would probably reflect off, but that's just my intuition speaking, I have not studied that at all so I am open to being surprised.
Last note: where you might look at the above chart and think that doesn't apply to me, it never gets to 50C around here, that is the temperature of the solar cells which get much hotter than ambient air temp because they absorb light. It's kinda one of their main features….
Fascinating conversation. So in the Deep South we can expect lowered PV efficiencies in the summer with our routinely 100 F/40-50 C air temperature, eh? Nice to know since this is the year we are putting the rest of our panels in. They will be positioned to catch as much breeze as possible, but there's a reason we are not doing wind power.
At least our winters will be merry and bright, even if our Christmases will not (usually) be white.
Hydrodog – Is your site still available? If so do you have stats and pictures, etc.?
I have people still asking if my site is for sale…..It has been sold. Am now fixing my home for sale now…. so that I can do the Atlas Shugged thing … go overseas ….live cheaper and utilize the foreign earned income exclusion….
Anyone care to discuss ???
I NEED SMALL MW HYDRO PLANT UNDER 5MW, HAVE TO BE PERMITED, IN HAND.