How a solar panel works

Photovoltaic (PV) solar panels are a cluster of silicon cells that convert light to electricity using the photoelectric effect.  The amount of energy produced from a solar cell depends on the amount of light, specifically  Photons, that enter the cell and the overall quality of it's internal construction.  The cells are "wired" together  to increase the output voltage of the solar panel to a useful level. 

The electricity generated by a solar panel is direct current (DC) just like a common flashlight battery.  So a row of solar panels are really just a bunch of batteries on your roof.  They are connected in identical ways electrically although the wires are a touch larger, these things are built to power  your dryer!   A good system design  will typically connect as many panels as possible as this will increase the DC voltage.  With DC the higher you can get the voltage, the less energy you loose inside wires. 

Converting sun in to electricity is difficult business.  Making a solar panel is a complex and extremely sensitive process backed by years of cutting edge science.  One of the most common types of solar panels uses  Crystalline Silicon.  The current manufacturing process for this type of cell is so sophisticated they can be built within 4% of the theoretical maximum efficiency.  In today's market panel manufacturers are focusing on lowering the unit cost over increasing the panels output. The price of these panels has now been lowered enough to truly compete against fossil fuels, and if you live in an area that qualifies for a utility rebate there may never be a better time to go green. 

The inverter is the "brain" of a solar energy system.  It's primary job is to convert direct current (DC) power to alternating (AC) which we use in our homes.  DC is what is stored in flashlight batteries, AC is what is available in a wall outlet.  See our learning center for more information on types of useful electricity.

Most solar arrays will use an inverter that is connected to the normal circuit breaker of a home or business.  This is known as a grid tied inverter.  It simply means that the electricity from the power grid, and the electricity generated by the sun are connected and are able to flow through the same wires.  With this technology you can install a solar array on your roof that is not large enough to supply all of the electricity that you use.  You use the solar power until it is gone, then buy energy from your utility for the rest of the time.  Connecting the inverter in this fashion requires an interconnection agreement with your utility as they will most likely sell the solar power during the day and then you will buy from them as usual at night.  A special electrical meter must be installed to keep a tally.  In fact if you produce more power than you use they must buy that excess from you at a wholesale rate.  So you are basically a small utility company buying and selling electricity for what is typically a twenty year contract.

An important thing to consider with a grid tie system is that the solar power and the utility grid power must be synchronized.  When the power grid goes down, your solar power must shut down as well.  This is especially important for fire fighters and electrical linemen who need to make sure no dangerous power is flowing while they are working. 

New technology has started to become more mainstream in the PV solar field.  There are devices available that will allow an inverter to control energy harvest for each solar panel independently.  The two most popular types are the micro inverter and solar panel  maximizer.  Both are able to increase energy harvest by allowing the inverter to get maximum harvest from each panel.  Micro-inverters actually do the whole thing mounted right underneath each solar panel.  The DC is converted to usable AC up on the roof.  A panel maximizer is a small box that connects to each solar panel basically "tricking" the string inverter into thinking that the panel is at maximum output even when the panel is at a low performance level.

A solar array can be installed in a variety of different ways.  There is even hardware to attach an array to the metal shed out back.  Some of the most popular mounting methods will be discussed here but keep in mind every situation is different and meeting with a qualified system designer is always recommended. 

L foot

Feet are mounted on the roof using what's called a lag bolt.  A pilot hole is drilled through the roof surface in to the center of a rafter.  The bolt is the covered in roofing sealant then screwed in to the pilot hole securing the foot which will support the array.  This simple mounting solution has shown remarkable reliability and decreases installation costs.  Most thermal solar arrays utilize a mounting bracket that is very similar to the L foot.  The are simple with few parts to fail and can support a large amount of weight which can sometimes lower the overall number of required mounting points.

Flashed Standoff

A flashed standoff simply means that the end result of the foot installation looks like a typical pipe sticking out of the roof.  The installer cuts a shape through your shingles, uses lag bolts to secure a metal bracket to a rafter, then installs a barrier around the hole.  In this "premium" installation moisture is drawn around and away from the hole in an attempt to protect against roof leaks.  This method also raises the array above the roof surface which can help cool the solar panels increasing efficiency.

Tile Roof

As far as installation is concerned tile roofs typically prove to be more expensive for a solar integrator.  The result however is typically seamless and attractive.  Specialized hardware is made for virtually every type of roofing material.  In most cases the feet for the solar array mounting hardware a made to match the rest of the roof.  Even though the installation cost is usually higher a tile roof is certainly not a reason to rule out installing a solar array.  Even though there is a small cost increase tile roof installations can outlast most roofing materials. 

Ground Mount

Pole mount, single panel mount, stacked panel mount, a crazy thing that sticks in the air.  A ground mounting solution requires two things; enough space to install and engineering that takes in to account what goes in the ground, what lives above ground, and what will happen to both over the next 50 years.  Ground mounted solutions can yield the highest solar energy production (see active tracker) however they typically require the most space as they are exposed to more shade - or less sun, you can't be exposed to shade but shade is still the bad guy.  If you have unobstructed area ground mounting solutions can speed up investment return and be some of the most fascinating renewable energy generators available.  

Ballasted Hardware Mounts

Solar panels are lightweight and modular.  This allows them to be mounted on a roof surface in a way that does not penetrate the roof surface.  Concrete weight, or ballast, is added to the bottom of the racking to keep the array safe during high speed wind gusts common in Colorado.   This configuration lowers concerns about roof leaks.  When considering a ballasted system it is important to note that a massive amount of data must be analyzed for structural integrity of the array and the building itself.  It is very important that a professional installation plan is developed to prevent costly repairs and unsafe roof loading.