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Coexisting on your Rooftop

• a number of PhotoVoltaic ( PV ) solar panels to gather the raw energy
• the racking that holds the PV panels at the correct angle to the sun
• a CIT ( Conversion Inversion Technology ) device which converts the 'raw' energy to energy that can be sold to the grid ( in its cruder forms, this is called an Inverter )
• a transformer and meter to send the power to the grid ( these are the only components not on the roof )
• lots of wiring to connect it all together

Click HERE to view/download the diagram to the right.

1. Holding the PV panels at the correct angle
2. Ensuring the PV panels are  kept clear of snow and water
3. Protecting the roof from damage
4. Minimizing the hassles when the roof ages enough to need replacement

Here is a document which discusses the engineering reasons for the advantages and disadvantages of different mounting systems.

1 - Holding the PV panels at the correct angle

PV panels work best with they are perpendicular to the rays of the sun.  Now, obviously, the sun moves during the day and over the seasons of the year, so any angle chosen is a compromise based on :

• the latitude of the installation ( how far from the Equator it is )
• the panels chosen ( some work better with oblique light than others )
• the electronics gathering the energy ( better systems work longer during the day and at lower illuminations )
• wind loading
• heating/cooling of the PV panels

( By the way, for those who think mechanically moving the panels with a " Tracking " system is a good idea, please read this. )

We observe that many installers choose the wrong angle ( often about 30 degrees )  for one or more of the following reasons :

• they are importing their 'systems' from a different geographical area ( for example, many come from California where the latitude and weather are far different than, say, Ontario )
• they are using 'one size fits all' racking designed for a different location
• their equipment only allows them to gather electricity at optimum angles and high illumination
• they don't know any better  

In Southern Ontario, the correct angle works out to about 45 degrees for the following reasons :

1. over the whole year, this is the average sun angle - our equipment allows us to gather electricity very well during Fall  and Spring ( and even Winter ) so we don't want to miss any
2. a higher angle allows the back of the panel to cool off - panels work better when they are cooler
3. a higher angle allows the snow to slide off and not build up to a level where it cannot melt all winter ( not a problem in California , but significant here

This explanation is covered in depth in this White Paper.

2 - Ensuring the PV panels are  kept clear of snow and water

In Ontario, most rooftops are designed to hold water during downpours.  The 'held' water then runs slowly off the roof so that the storm drains are not overwhelmed.  As you can imagine, this load of water is heavy.  Similarly, in the winter, snow may accumulate.

Some installers mount panels at such a low height that during water retention, the wiring and panels will be underwater - not a good idea with electrical devices.

When snow arrives, the panels will actually try to shed it.  As light reaches the panel ( even through snow - which is translucent ), the panel actually converts some of the light to heat, melting a thin layer of snow into nice slippery water. 

• Please note that if the inverter does not turn on at low enough light levels, the PV panel won't do anything, and no thawing will occur.

• If the panel is at a steep enough angle, the snow will slide off. 

• If the panel is at too shallow an angle, the snow won't slide off completely - next night it will freeze again, and the panel won't be able to generate enough heat to melt the ice .  A buildup will occur, and soon the panel is so blocked it cannot generate any electricity . Now that doesn't matter if the electronics don't work well at low illuminations, so many low-efficiency systems are built that way. 

On the other hand, our proprietary CIT electonics from Hybridye Power Electronics can gather electricity at low sun intensities, so when the mounting  angle of the panel is correct, heat is generat the snow slides off, the panels gather electricity, and it can be sold to the grid - earning the facility owner more income.

This explanation is covered in depth in this White Paper.

3 - Protecting the roof from damage

FIRST - let's understand the meaning of " roof ".  Obviously, it is the big flat thing at the top of the building that keeps the sun, rain, and snow out.

The typical commercial/industrial rooftop actually consists of mulitiple 'layers'

• at the top is a layer of gravel - ballast to hold everything down
• next is a waterproof membrane - usually a thin layer of rubber fastened together in a large sheet - this is the only thing which actually keeps water out
• below that is usually a layer of plywood for stiffening
• under that is a layer of ( usually ) foam insulation
• next is a 'deck' - sheets of corrugated steel to hold everything else up
• at the bottom is the actual steel structure that the rooftop  rests on - beams and joists

Unfortunately, the typical 'low first cost' rooftop array is mounted exactly that way - on ballast stones sitting on the membrane. Imagine hundreds of concrete slabs with tons of steel and glass on them. Imagine the wind shaking the panels and racks which causes the slabs to move. Imagine a typical Ontario winter, when the rubber membrane is so cold it is brittle.  Imagine the hundreds of leaks the next spring.

Hybridyne doesn't build rooftop arrays like that - we fasten the racking to the structure of the building ( the roof beams and joists ), and don't sit it on the actual roof surface. Because all that weight isn't sitting on the rooftop at all, the expensive roof is spared from inevitable damage.

4 - Minimizing the hassles when the roof ages enough to need replacement

Every roof membrane will eventually need replacement ( usually at about 20-year intervals ).