We are on the way back to the future, despite the stamp this was a framework for 1kW in December 2007
When the Earth was young, feed-in tariffs were 44 cents and solar panels were $5 per watt. We spent a lot of time building angled frames and orienting them in just the right direction for maximum yield. These days there are inexpensive panels available wholesale for less than $0.25 per watt and you just buy more of them. So are angled frames dead? I don’t think so, but let’s find out why.
That was then
For those familiar with solar design and installation, one of the basic points is that maximum solar radiation is captured somewhere in the far north, at a distance related to the latitude of your address.
For systems in remote areas, we used seasonally adjustable arrays with an angle of 45° or greater to capture as much valuable winter sunlight as possible. We showed customers how to lay them back flatter to get more summer yield, but that rarely happened because you had a lot of sunshine in the summer and so there was definitely a surplus of energy.
For a grid-connected system around Adelaide with a slope of 20 or 30 degrees, there is little difference in annual yield. In fact, I believe that 5° South on the summer solstice was the optimal angle at midday. And let’s not forget the tracking arrays. Introducing moving parts that keep solar panels chasing the sun across the sky every day is a great way to get 30% more yield and make totally reliable solar power a hassle.
Install a tracking solar system, they said…it’ll be fun, they said
This is now
Solar modules are now so cheap that the optimal orientation for modules is basically ↑up^
As long as they are not in the shade, you put them on the roof and they generate energy. In fact, it has been difficult to get some old solar planners to put down the protractor and realize that tilted angle frames are no longer necessary to improve yield per se.
Formulate an example
This gas station uses tons of electricity. The ideal would be to install 100 kW. Although it wouldn’t meet demand, it definitely helps reduce bills. We had three problems with this job.
No solar power on the red canopy above the gas pumps. The purple roof required 2% more budget and was deemed too expensive.
First, the short-sighted bean counters wouldn’t buy a little extra control hardware to use the car wash roof. They had a strict return on capital threshold.
Second, the roof of the main building was littered with refrigerators and sloped 3 degrees to the south.
Thirdly, the seller, who is not to be interviewed, was adamant that the building should face north and therefore specified angle framing.
Cardboard boxes provide much-needed shade for electricians. Thank goodness we no longer have to wire roof insulators.
The result was that we only ended up with 231 modules for around 72.7 kW. The system was smaller because we had to waste space on row spacing.
For mathematically sophisticated roofers, the spacing between rows is approximately 1½ or 2 times the X dimension to avoid the rows of panels shading each other (Y dimension).
Laid flat on the roof, more panels could have simply generated more energy. Additionally, a quicker installation with less materials might have even paid for the additional hardware needed to add capacity to the other building.
In a flat roof design with a 3° south orientation it is possible to have 308 modules and 97kW, so that defeats the idea of angled frames, right?
Find the right angles
We have already written about the benefits of self-cleaning solar energy. Tilted frames keep them cleaner and produce more every day. In fact, solar system rules state that if your solar panels are tilted less than 10°, a written warning must be included in the handover package to alert owners that they require more maintenance.
Angled frames also mean you don’t have to worry about warranties. When tiles are laid flat, they do not drain properly, which effectively means the bottom edge spends half of its life in a puddle. There is a risk that water can enter the panel and cause ground faults.
The right direction is up
With time-of-use measurement, it makes sense when people say East is the new North. The price of electricity in my house triples at 3 p.m., so I argue that West is so fashionable that it’s the new black. In fact, even south-facing panels make more sense in Melbourne than in London.
If you have a flat roof, the best type of solar installation is a crinkle-cut system.
An east/west crinkle-cut arrangement on a flat roof.
East and west facing panels on sloped frames stay cleaner, run cooler and provide more space for maintenance. Better yet, you put more panels on the same roof space, meaning you generate more power at more valuable times of day.
Flat Solar is a cup game
The only downside to crinkle-cut solar systems is the slightly higher upfront cost. Getting building permits from the local municipality can be a hassle, but the framing and installation itself should, in my experience, cost at most 25% more – about $250/kW, or $1500 for your 6.6kW system.
That sounds like a lot unless you factor in a $200 professional cleaning every six months. These bills will exceed the cost of angle framing in four years. If the system is clogged with leaf litter and pigeons, removing the solar array to clean the roof will easily cost $1,500, whereas you can do the cleaning under an inclined frame, even if only one panel needs to be lifted to gain access.
Tune in next week and I’ll go through a detailed comparison of the above gas station. There are a few numbers to understand and how your solar installer can design the system from the desktop and calculate the return on investment with remarkable accuracy.
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