Carport - Solar Shade Structure

A car port or solar shade structure is very useful in and of itself independent of any rooftop solar, especially with all the EVs that are being purchased these days. If the homeowner doesn't want to deal with the utility company, the carport can be entirely off-grid and use batteries to store energy and top off an EV at night. Or it can be integrated directly with the utility without any batteries at all.

In this section, we'll go through some of the typical design considerations with carports and shade structure such as pergolas.

Carport-Shade Structure

The picture below shows a typical driveway, where the owner have to park in front of the garage because it's otherwise being utilized as a workshop. The owner is contemplating the purchase of a sports car. It may not be an EV now, but in a couple of years the owner would like to accommodate one. There is an existing shade structure on the left, but it is too small to provide adequate shade through out the day to the sports car.

Carports

There are essentially three approaches that one can take. 

Build New

You could essentially build a new carport on the right hand side and leave the existing shade alone. 

Remove and Replace

Alternatively, you could remove the current shade structure and build a new dedicated carport.

Modify Existing

You could try to add solar to the shade structure where the solar would extend beyond the existing structure to make it large enough to provide continuous shade throughout the day for the sports car and you could cantilever the solar racking where it extends beyond the structure so that it is properly supported given the high wind loads due to occasional wind storms in this area. 

Designing an New Solar Carport

Let's look first at designing a new structure to go on the right hand hand side of this. There are numerous shade structures designed to give share to a car. These structure may have been designed for integrated solar or they may have been designed just to provide cover to a car, and integrating solar, if desired, is left as an exercise for the designer. Another option is the pergola or shade structure which can be adapted as a carport and may or may not have been designed to support and have integrated solar. The figure below illustrate a couple of these options:

Unfortunately, as is so often the case with the solar industry, the first option means that we have to design the solar on top of the otherwise purpose build structure.

The other options were simply lead generation advertisements where the lead generation company is just trying to get you to click through to something that will just collect your information and send it to a bunch of installers with neither the front end company who placed the ads, nor the installationation companies who paid for the leads has any idea about the picture that was used to generate the lead and they only want to sell you rooftop solar. 

So the whole process leaved everyone dissatisfied and feeling a little slimy and like you've been taken advantage of. You have to do some additional sluething through Google's reverse image search to get information on these products. More on that later.

Design Specifications

For now, let's just focus on option one since that is a purpose build structure, is generally much more inexpensive than something designed with integrated solar, but with the downside that it requires some D(o)I(t)Y(ourself) and may be less efficient and not stand up as well long term.

Curved Surface

The first thing to note is the curved surface of the carport. While this shape may be optimal in terms of offering good coverage for the car, it represents a challenge for the design. Most solar panel are rectangular and rigid and meant to be laid out flat or on angular surfaces. This is generally to protect the crystalling and inflexible nature of the substrate of the individual cells, whether mono-crystaline or poly-crystaline. The advantage of these types of cells is that they are generally of higher output.

However, there is another type of solar cell that is flexible and can even be rolled up in some cases. The advantage is that they can be places on many surfaces that are not rigid and even sometimes accommodate odd shapes and curves. The disadvantage is that these flexible panel have lower output with the cells getting varying exposure to the sun and in some cases may be subject to eventual cracking under the stress of repeated flexing.

Dimension

Accepting that the panel may have slightly lower out put, we need to know the dimentions of the structure so that we can cover as much of the structure as possible to maximize the power we can get out of it.

Panels

Next we have to find panel that are A) adhesive, B) close to nine feet in length or can fit in multiples that add up to nine feet, and C) have a width dimension so that we can lay them out next to each other and come close to 16' feet. Fortunately for us, solar panels come in all shapes and sizes, flexible and not, adhesive  or with other attachment mechanisms.

MiaSole Flexible FLEX-03M 2.6m

Fortunately for us, there is one panel that seems to match our specifications pretty closely. It's the MiaSole Flexible FLEX-03M 2.6m which at 8 ft 5.7" long and 3 ft 2.3" wide, will cover our surface nicely.

Next we have to figure out how much power we can get out of these panel, and for that we need to find their maximum operating voltage and current, so we have to diver further into the panel specifications:

Power Output

Know the power output of the individual panels we can then calculate the total power from the system, once we lay them out in series or parallel. To keep the wire size small, we'll use a series configuration:

Decision, Decisions!

Now, unfortunately, it gets a little complicated because we have to make some major decisions about how we want to use power from our solar panel, and that has major implications for our system set up and what further components we need.

Off-grid or On?

Probably the simplest thing we can do is to be grid tied, that is power from the solar cells go directly to the grid, period end of story. All we need in that case is an inverter and a hook up through our service panel (with appropriate lockout and shutdowns in case of grid outage so we aren't endangering utility employees with an energized system when they may be working on the grid). The only thing to do is to match the inverter to the solar panel and make sure has appropriate voltage range and power.

System Components 1

So, now we've designed the simplest system. Here's what it looks like all together:

Adding EV Charging

Remember, the original intention of adding a solar carport was to be able to add EV charging to the house for when the home owner eventually decides to add an electric vehicle or converts an internal cumbustion engine (ICE) vehicle to electric, which is an increasingly popular thing to do these days, especially for people who love their classic and sports cars, but don't want the mess and bother of ICE, even if they can get them serviced, especially for older cars where parts availability only gets harder with time. By converting it to an electric vehicle, they can keep the car they love and bring it up to modern, clean standards and technology, and as batteries continue to evolve perhaps get even more performance from them. But that's a discussion for elsewhere.

There are essentially three options for home EV Charging:

• Level 1 

  • Basically 120v ac just like any other appliance, slow and takes a long time, but done overnight it should not matter

• Level 2

  • Basically 240v ac depends on the household wiring but if you've already got a washer/dryer/dish washer the house is already wired with 240 v circuits and the question is if there is space in the panel for another one and due to sizing constraints you may be limited in terms of how many of them can be used at the same time or only  individually

  • This is a lot faster than Level 1 charging

• Level 3 (DC fast charging)

  • The vast majority of homes are not equipped nor should they be for Level 3 charging, which should only be done at commercial charging stations