A Different Angle

Traditionally, we’ve been told to point our solar arrays to the south.  There were guidelines on the angle from horizontal, too.  Pretty much all of this is open for question, now.

You may have noted my recent posts on the arc the sun travels and my experiments with a vertical array.  There’s more to it.  Instead of my next expansion of the Solar Shed being linear along the airstrip, I’ve decided to make a portion of it extend to the north, with a north-facing slope for the solar roofing tiles.  I had thought to add just a carport for the EVs on the backside, but the Man Cave needs room for a fitness center and other activities.  Careful observation has shown that a north slope could pick up quite a bit of morning and afternoon sun.

It’s not just me, thinking this way, and people who don’t have a roof with a perfect southern exposure needn’t fret when wanting to add solar.  Recent studies in Australia have found that splitting the array between northeast and northwest is a good plan.  Bear in mind that the Land Down Under is upside down, or we who dwell in the Northern Hemisphere would say southeast and southwest.

Why?

Well, think about when you use your electricity and the possibility that maybe sometimes you are making too much and other times not enough.  In grid tie situations, there are sometimes limits on how much the power company allows you to export.  Also, places that have high concentrations of solar, have run into problems when everybody is making max power at the same time.

Typically, we use the most power in the morning and evening.  Think about it.  You roll out of bed and go turn on Mr. Coffee.  You stumble into the shower, which activates the water heater.  You pop a couple of frozen waffles into the toaster or nuke a frozen omelette.  You might even fry up some bacon and eggs on the stove.  After breakfast, you toss the dishes into the dishmasher (yeah, that’s what we call it) and off you go to work.  Lots of electricity was consumed.

Maybe you set back the thermostat during the day, so it cycles a little and so does the fridge.  Not much goes on during the day.

You come back home, after work, and hit the thermostat.  Turn on the tube for the evening news.  Run pretty much everything in the kitchen to get supper ready.  Maybe do a load of laundry.  More water heater and more dishwasher.

Lots of power in the morning and evening.  If your arrays (instead of array) pick up more power early and late, it can be self consumed and not run as much back into the grid.  This minimizes the chance of exceeding a limit.  It is very beneficial in areas where they pay you, say, 4 cents for your power and charge you 12 cents to get it back.

There are benefits off grid, as well.  I see in my own array that my batteries sometimes are just begging for some morning sun, especially these mornings where the A/C needs to really get buzzing early.  Here, we define a warm day as 80 by 8 and a hot day is 90 by 9am.

Then, late in the afternoon, that afternoon sun is way off the axis of the south array, but really cooking the back side of the house, placing maximum load on the A/C.  Not only that, I get hungry about then and all the kitchen stuff comes online.

At solar high noon, my batteries are pretty much topped and more power is being generated than is being consumed.  That means I am just throwing power away.  Part of that will be alleviated with my next battery upgrade and that will allow me to put more load on the system.

Another angle on this, so to speak, is time of year output.  Come winter, the sun will lean a bit more to the south.  The array on the north slope may get little or even no direct exposure to the sun.  They will put out a bit because of incidental insolation, but the lower angle on the southern array will produce more power due to closer alignment to the sun.  Then there is the matter of load.  I rarely run the A/C in winter.  I suppose I could run the heat pump.  That would save on the efforts involved with firewood.  Firewood is good exercise, badly needed exercise, but there may come a time when I can’t handle that anymore.  The problem with heat pumps, which gas companies are quick to highlight, is that they don’t pump much heat when it is truly cold.  That’s why we have a wood furnace boiler out in the backyard.

For now, though, summer is our high power consumption time. Right now, probably about 90% of my solar output is going to air conditioning and that is more than the rest of the loads combined.

Therefore, I propose that you carefully study what your loads are, and when, and you might find your options for an effective solar array are better than you thought.–Neal