This is the part of the DIY process for solar heaters where some people check out (mentally).
This is because it involves thinking about the math behind the placement of your panels.
But you don’t have to do all of the work yourself.
The good news is that there are TONS of calculators online to help you figure this out based on where you live.
We’ll detail some of them a little later on.
If you find yourself getting bored in reading this, stick with it.
You will get much more efficiency out of your panels if they are placed in the right place.
So, if you’re ready, here we go… solar heater placement, and basics of attracting the sun.
As the seasons change, the angle of sunlight in the sky is also going to change.
In the summertime, sunlight comes from directly overhead during the middle part of the day. The sun rises north of east and sets north of west. But we don’t really need solar heating in the summertime in most locations.
At the Equinoxes (mid-Spring and mid-fall), the sun rises approximately due east and sets approximately due west.
The angle of the sun in the sky is a little bit lower.
Wintertime is when we really need the heat from the sun.
In the winter, the sun rises south of due east.
In the winter, the sun sets south of due west.
The angle of the sun across the sky is much lower during the winter.
That’s going to help determine where we should place our solar heater panel.
(By way of reminder, I’m using the terms “panel” and “collector” interchangeably here. Both refer to the physical box where the sun is being collected and the air is being heated.)
Let’s figure out where’s the best place to put the collectors/panels.
Things to keep in mind:
- The sunlight angle is going to change with the seasons.
- To get the maximum efficiency out of any solar collector, you want the rays of the sunlight striking the collector to be as perpendicular as possible.
So a perpendicular angle is directly straight on at 90 degrees. That’s what we’re shooting for if we can get it – 90 degrees.
To calculate what angle will be best for your panels in the middle of winter, here are some links to some great calculators.
- http://www.academysolar.com/calculator/site_info.php (This one will get you to provide some information, but still good information can be gotten from it.)
- http://www.solartradingpost.com/solar-angle-calculators.html (Good simple calculator.)
- http://www.renewable-energy-concepts.com/solarenergy/solar-basics/tilt-angle-pv-array.html (Good calculator, requires you to do some math, but keeps it simple.)
- http://www.roofray.com/calculator (Really cool calculator based on a satellite image of your roof)
- http://www.srrb.noaa.gov/highlights/sunrise/azel.html (NOAA’s old calculator)
- http://www.esrl.noaa.gov/gmd/grad/solcalc/ (NOAA’s schnazzy new calculator)
Once you’ve used one of those helpful tools to figure out the pitch of your roof and the best angle for your panels, you will need to consider one more factor.
Do you have an attic space that the air needs to pass through?
If yes, you will need to run ducting from the back of the collector through the attic space and down to the uppermost floor below the attic.
If you have a finished attic space, this could be ideal. However, if your attic isn’t well insulated, this may not be the best option for you.
Really, depending on the insulation level, this could be a really great location to get thermal gain and heat into that upstairs room. If however, you are piping air through an unfinished or poorly insulated attic space, then the hot air has to be pushed or pulled down through ducting.
And you may lose a certain amount of heat (because even though ducting might be insulated, you’ll still lose some heat for the distance you’re covering).
Depending on the distance, you might also need an additional fan, because hot air tends to want to rise.
Generally speaking, you may lose some efficiency to roof mounted heating panels, especially if you’re passing through an unfinished attic space vs. a wall mount. But if a roof space is all that you have, that is definitely better than nothing.
For existing homes, wall mounted solar heaters are generally regarded as the most straightforward, simple and most effective.
This is because when you’re installing your panels, you’re only having to pass through the thickness of the wall. Depending on where you live, that thickness may be 6-10 inches.
With a wall mounted panel, basically you’re pulling air in air from the room and blowing it back into the room. That makes for an easy install and great efficiency for a solar heater.
Something to pay attention to when deciding where to place your solar heaters is your eave overhangs.
Depending on how your home was built, it is possible that the overhang of your roof could shadow your solar heater panel/collector.
Although a slight shadow on a part of the thermal collector won’t affect its heat output very much, if you buy a solar heater panel with a built-in photovoltaic module (for powering the fan(s)), and that panel is in shadow, you will end up reducing the amount of current available to operate the fan motor.
If the fan isn’t running as much or not moving as much air, you will reduce the effectiveness of the panel and lower the heat output.
So definitely pay attention (if you’re buying a commercial model of solar heater) that your roof overhang, (also known as the eave overhang) is not going to put your solar heater panel in shadow in the wintertime.
Facing south is (generally speaking) best.
And if you’re off from south a little bit, it’s not going to make that much of a difference.
What’s more important is the vertical angle (which the calculators mentioned above can help you to calculate).
Exceptions to “south is best”
There are exceptions to the rule of placing the panels facing south.
If you tend to be an early riser or you want as much heat as possible during the morning, and you’re not as concerned about the afternoon, then you can consider placing a solar heater on a nice sunny east- or southeast-facing wall.
You will get the first rays of the sun and you’ll heat that collector up sooner in the morning.
Similarly, if you want to balance toward afternoon sunlight, it might also be a good idea to put your solar panel heater on a west- or southwest-facing wall.
Just keep in mind that if you use your solar heater panels this way (facing them east and west for morning and evening heat), you’re going to lose some of the total of the available heat possible if you face it south and get as much heat as possible for the full day.
In conclusion for today:
Wall mounted solar heaters are (generally speaking) more effective. Also, with a wall mounted solar heater, you can actually purposefully shade your panel in the summer (when you don’t need heat) using your home’s overhangs.
A roof mount is possible, but you might need to consider a tilt-up kit to place the collector/panel at the best angle of tilt. The angle is dependent on your latitude.
Consider as well that if you tilt the solar heater on your roof, you’ll have more ducting to cover. That ducting will be exposed to the elements (getting the heat from the panel through the roof (and potentially through an unfinished attic) so you will need to insulate it to retain the heat coming out of the collector.
That was a lot of information over the last three days.
You’re quickly becoming an expert though, and very shortly, we’re going to get into actual designs and panels you can build at home. Stay tuned!
What questions do you have about solar panels and solar panel heating at this point?