Solar lens effect must be taken into account when choosing your MPPT; surges in solar power energy occur regularly.
If you are planning to build a green home you must take account of how certain properties of droplets of water can effect the sun's radiation, increasing its energy temporarily by fifty percent and perhaps more.
What is unexpected is that a 100 percent cloudless day, with very low humidity produces lower levels of radiation. Moisture in the air can increase the sun's radiation and concentrate the energy received at your photo voltaic panels by refraction.
A PV panels turns photons of sunlight into a usable direct current, powering your home and office; your factory and farm too, of course.
This solar lens effect is especially true as a cloud brushes past the sun.
Ever noticed that your skin is far more likely to burn should you be tanning on one of those days when there is a thin haze in the sky? By refracting the solar energy, moisture in the atmosphere can substantially increase the energy at the PV panels on your roof.
That moisture, coming from the sea, actually carries fine salt crystals too; did you know that rain is about one hundredth of the concentration of sea water, depending on how close to the ocean you live? These minerals can also influence the solar lens effect of clouds.
This sudden, but temporary, surge in solar power energy has importance in the planning when you are building a solar powered generator; the amperage may exceed the specs of your regulator. Whilst a high quality regulator, such as the MPPT that I have chosen, is designed to cope with sudden temporary surges in power, el-cheapo may blow.
In Holland we would say, "goedkoop is duurkoop." Buying cheap is often expensive. If you put in the best equipment the first time, it hurts only once.
When choosing the required items for a solar generator, it's best to assume upfront that, when you discover that Mr Golden Sun offers his energy free of charge, you will want to add more PV (photo-voltaic) panels which of course deliver more amps.
Whilst your original planning may be for lights and computer equipment only, my experience is that it won't be long before you are kicking yourself for designing too small. Upgrading a 20 amp regulator to a 60 amp was an expensive mistake for me. Oddly the sixty amp was not much more expensive that the twenty, but the upgrade...
Back to the solar lens effect
On a dry day, my solar panels will deliver about 1050 watts of power at midday. But yesterday, as the cloud above passed over the sun, the power surged to...
A 15% increase. I have seen it yielding a massive 50% increase, but only for a few seconds. It's not your imagination - your skin will burn worse on a slightly cloudy day on the beach.
So I feel comfortable doubling the number of PV panels which will yield around 40 amps for my 48V solar powered generator
40A x ~ 50V = ~ 2000W (or 2kW), roughly the power used by a hot water kettle.
We have done several upgrades since writing this page some years ago. We now have 4000 watts of panels, yet stay on the grid for rainy days, simply for convenience. I'm not yet that much of a solar nut!
One innervation, after a consideration about shadows on PV panels, was to put 900 watts of panels on a west facing wall. It sounds crazy, receiving direct sunshine for less than half the day, but in fact it's the late afternoon when our need for energy is the greatest; when our solar electric oven is being used.
Yes, 4000W and a 10kw inverter, are ample for heating water, cooking, using my power tools and even the heavy duty electric lawnmower. Plan to go big from the start and save yourself a lot of money and headaches.
On the other hand, reflection doesn't have to do with the concentration of power, if you have a flat mirror, but simply the redirection of light. You can't use it to set fire to a piece of paper as you could do with a lens.
On the other hand I'm thinking of using a concave mirror made of
small squares on a disused satellite dish to increase the energy
reaching my panels.
This triple reflection has nothing to do with your proposed solar generator; it's just an exercise in fun, and an appreciation of the beauty of creation.
For just two weeks in the year, once as the great ball of fire moves north, and the other as it retreats south again, we enjoy this triple reflection of the sunshine in our home; it's right around the equinoxes.
The sun beams land on this window opposite which acts as a mirror,
and the sunshine is reflected... onto the mirror on this sideboard.
From the sideboard mirror the sunshine is reflected a second time, on this occasion onto the glass on the hallstand.
Today she who must be obeyed has made a flower arrangement of poppies she has just rescued from the honey bees that seem to love the pollen, and wear the flowers out with their coming and going. Mm, I wonder if they get a high from snorting it? Within an hour they have ruined the blooms.
In reflection there is no bending of the sunbeams.
And so the third reflection. Here is the image blown up on the wall. Beautiful, eh?
This is light is lovely to behold, but perhaps even more important is that it can be put to work to power your lights and computer, and even your lawnmower and oven. See how a day in the life of solar geek Bernard Preston unfolds.
Reflection and refraction, two very different aspects of optics, something we take for granted perhaps, using them every day to brush our hair, and in spectacles. And of course in the eyeball itself where the lens effect enables us to see objects clearly.
Isn't God's creation stunning? Or do you believe it all came about by chance?
Shadows on PV panels in contrast to the solar lens effect are reputed to drastically reduce the output; however, my measurements suggest this isn't the case with some until they cover more than half of a panel.
With others even a small shadow can have a profound effect.
If the shadow covers one whole panel, the output from a whole string will be zero even if the remainder are in full sun.
Bernard Preston certainly has something of an enquiring mind; and his wife says he should be on Ritalin! Observing surges in power far beyond the expected output of the PV panels he noticed the solar lens effect.
Good MPPTs like those produced by MicroCare handle these occasional surges but beware of those made in Ping Pong Ting.