Solar photovoltaic (PV) systems have become one of the best alternatives to generate your own source of renewable and clean energy, depending much less on utilities and save money on the long-run by offsetting energy bills.
Due to these facts, home and commercial owners are getting more and more involved in this sector, curious on how to install their own solar system or just curious on the procedure that must be followed to carry on a solar PV installation.
In this article, we will go over a few steps of the procedure to give you a good overview and if possible install the system yourself. If you are looking for specific RV solar PV installations, you can check this article which focuses on this type of systems. Now, let’s go over the main phases of a solar PV system installation.
Choosing the right location for the solar panels
Solar energy generation is highly dependent on the tilt and azimuth (orientation) angles in which it is going to be installed. For the US, the optimum tilt angle varies depending on the latitude of the city where you are at, but generally anywhere between 20 and 30 degrees is a good reference point.
On the other hand, the orientation plays another important role. The highest production can be obtained by placing the modules to the south, meaning 180 degrees. Followed by orientations towards the east and west. Finally, north production is very low, therefore it is the less desirable location for panels.
Now, these are general reference parameters, however, it is highly important to know first what type of installation it is going to be. There are two main types, roof mount and ground mounts.
Roof Mount Systems
Roof mounts are the most common across the US because they generally offer a better return of investment rate and also because many times homeowners do not have enough space in a backyard as to place a ground mount. However, roof mounts are highly restricted in terms of space, orientation and tilt angles. The panels must be placed on the available roof faces which have a predetermined pitch and orientation, which not always is the best. Also, there can be multiple obstructions on a roof including chimneys, vents, antennas, and so on, which reduce the space where the panels can be placed. Therefore, many times it is not the most optimum.
Ground Mount Systems
Ground mounts, do not have such limitations, and they are generally placed at an optimum tilt angle and facing south which maximizes the production of the solar panels. If space in the backyard is not a problem and there is not too much shade caused by nearby trees, a ground mount may be a great choice for you.
Install the Solar Mount Structure and Secure the Panels
The first thing that must be considered in any solar installation is to set the racking system first. Assuming that you would be installing on a roof mount, you must know first if the racking is to be installed on a tilt roof or a flat roof.
For pitched roofs, a railed system must be installed. This consists on attaching a set of rails to the roof to hold the solar modules. Flashings, screws and bolts are used to attach these rails by drilling the roof and using sealant to prevent a water leaking. Rafter locations must be identified first to place the flashings there, this provides a higher structural support for the system.
Below can be seen a schematic of the typical flashing mounting. Also, Ironridge, one of the best solar mounting racking manufacturer companies, provides short video on the procedure to install their new flashing mounting system which can serve as a good reference of this procedure.
Once the flashings are set in place, we use a set of clamps and fasteners to secure the rails and then all that is left to do is to place the panels on top and similarly adjust them by using another set of clamps and fasteners.
Meanwhile, for flat roofs, a common practice is to use a ballasted racking system in which a set of ballasted rocks are used on the back of the panels to hold the system to the floor. A flat mounting racking system tends to be installed in angles between 5-30 degrees depending on the type and manufacturer. These systems can provide the option to install dual-orientation (east-west) systems, which although they generate less energy than a south facing system, they can have a more fluent response to patterns of consumption.
(a) Ballasted racking mounting system for higher tilt angles (20-30 degrees). (b) Flat roof mount system for lower tilt angles (5-15 degrees). Source: K2 Manufacturer
On the other hand, if we are talking about a ground mount, the procedure is different. In that case a foundation must be made by digging on the ground to act as the structural support for the modules. Depending on the type of soil, whether it is sedimentary rock, gravel or clay, the type of foundation will change. Available foundations tend to be helical piles or concrete piers. Once the foundation is in place, a set of vertical mechanical aluminum pipes are installed. Then, the rails are placed in a rectangular layout to place the panels directly on the structure.
Interconnection of the Solar Panels
The most common way to interconnect solar panels is by using the so-called MC4 connectors. Before moving on to this step it is important to have a very clear idea of the system layout, including which panels are to be connected in series in a single string and the number of strings that will be installed. It is common to set a series connection and then send the string wires to a combiner box or directly to the inverter. This is done by connecting the positive lead of one panel, to the negative lead of the next module. However, for small off-grid system cases, there is also the possibility to connect panels in parallel, or even do series/parallel connections using the connectors. To learn more about this, you can visit this article on solar connectors.
At the time to do this, it is important to know that as long as the solar panels are receiving sunlight, they will have an open circuit voltage waiting for something to close the path of the electrical circuit, therefore, it is important to be careful while handling them.
Maximum Voltage Limit
Another consideration that must be taken into account when stringing the modules is to make sure that the maximum output voltage of the string will not exceed the inverter input voltage, taking into account temperature variations. This must be done during the design phase.
Also, it is important to make sure that the panels are not connected to the load during the installation phase. For safety purposes, the grid must be disconnected to ensure no electricity will flow during the installation.
Rapid Shutdown Switch
Moreover, a recent requirement according to the National Electrical Code is to make sure that the system includes with a rapid shutdown switch installed on an easy-access location. This is very important for fire safety reasons to ensure that in case of a fire in the house, the firefighters will have a safe path to the roof by disconnecting the PV system through this switch.
Installing the inverter
After this, the next step is to install the inverter on a location according to the required parameters of the manufacturer. Some equipment can be installed outdoors while others must be installed indoors. Besides, making sure of which inverter layout you will be installing its important before jumping to the site.
There are two main types of inverters. The ones called string inverters and the ones called microinverters.
String inverters are the most common, most matured and more economic option available in the market today. This consist of a power electronic equipment which is capable of converting the direct current (DC) coming from the solar panels into alternating current (AC) which is commonly used to power appliances. Based on the power size and voltage input, the string inverter can handle up to a maximum number of panels.
Many of them also include a number of MPPT inputs which allow to connect multiple strings without the need for any combiner box. MPPT stands for maximum power point tracker and it represents an electronic system capable of tracking the maximum point of operation from a string in specific. These string inverters are generally installed close to the main panelboard to reduce ohmic and voltage losses.
Meanwhile, microinverters are the cutting-edge technological solution for the residential sector. These devices perform the DC to AC conversion at module level, meaning that each solar panel will have a microinverter installed. These microinverters are much more efficient in sites with different orientations and different shading patterns, however they are more expensive than string inverters.
Connect solar inverter to the batteries (if applicable)
If you are choosing to add energy storage to the system, then the next step would be connecting the inverter to the batteries. For this there are two main methods, DC-coupled and AC coupled.
Under the DC-coupled configuration, a charge controller would be required to act as the maximum power point tracker while the battery inverter would only perform the DC to AC conversion from the battery bank. This configuration is highly used for stand-alone and small solar PV and RV applications.
Alternatively, there is the AC coupled configuration. Under this setup there are two types of inverters, the string inverter and the battery inverter. The string inverter would perform the same task as it would on a grid-tied PV system which would be performing the MPP tracking and converting DC to AC. On the other hand, the battery inverter is connected to the energy storage system, to the backup panelboard and also to the main panelboard.
When the power from the grid is active, the string inverter sends the AC power to the backup panel loads and also to the battery inverter, device which at the same time uses this power to charge the energy storage system and to feed the main panel board as well. When the grid is off, the battery inverter disconnects from the main panelboard, and starts generating its own alternating frequency. The string inverter synchronizes to this new frequency and the system starts working in isolated mode to feed the critical loads until the power from the grid is back on. This system is mostly used for backup purposes. Illustration below shows a diagram of this system.
Connect the inverter to bidirectional meter
Additionally, another upgrade must be made. Households typically have installed a meter to track the use of energy, this is typically set up by the utility. However, when installing a solar PV system that will be grid-tied or grid-tied with battery backup, the household turns from being a strictly demand load, to become a load that can quickly change its load mode to a generator mode. This means that your PV system will be able to inject power to the grid.
Traditional metering systems only allow to keep track of energy in a single direction, which is assuming that the household will always be consuming power. However, if they household has the possibility to act as a generator in the power grid, then a bidirectional meter must be installed in order to track energy flows in two-ways direction (as load and as generator). For this purpose, the PV system needs to pass local electrical inspection and approval from the electrical utility to connect the system to the grid. It is important to check on local jurisdictions in order to comply with the requirements on your state.
Solar System Commissioning
Finally, the last step in the solar PV installation is to switch ON the system. This is done by flipping the breakers, ensuring that the inverter will not set any sort of alarms and that has been synced with the power grid. In this matter, the configuration will vary for each case scenario and manufacturer, it is important to check on the manual from the inverter to properly set the system. Consulting a certified electrician for this matter is highly important if you are not sure how to handle this with the inverter. Stand-alone or off-grid systems are easier to handle from a permitting point of view in this matter since they do not require connection to the electrical grid.
Solar Panel Maintenance
Once your PV system is up and running, it is important to know that the story doesn’t end there. Generally, you will need to perform some maintenance procedures every now and then to keep the solar system in perfect shape.
A solar PV system maintenance is quite simple since there are no moving parts involved. However, a general inspection should be carried out at least once a year to make sure all the connections are in good state. Cleaning is probably the most important part, especially in places where raining is not that common or that are dusty. Dirt blocks the sunlight from the panels which eventually affects the solar production. To clean the modules you should refer to the maintenance guide provided by the installer or the manufacturer to make sure you keep guarantee conditions.
In most cases, it is recommended to clean the modules using water directly or if dirt doesn’t remove make use of cleaning liquid specialized for solar panels called Polywater, a hose can be used for this purpose. An important thing to keep in mind is to never, under any circumstances, use bleach, detergent or any other sort of chemical, this can damage the modules badly and lead to delamination which is a devastating phenomenon for the system.
Frequently Asking Questions
DC optimizers are another type of module level electronic equipment which perform the task to track the maximum point of operation of the solar module, just as microinverters do. The main difference between them is that DC optimizers output is another DC signal that needs to be converted by a string inverter, while microinverters directly convert the DC signal into AC.
Houses with layouts or solar arrays with different orientations/shading conditions are generally better for microinverter configurations. Since microinverters track the maximum power point of operation at module level, the solar production will always be higher than with string inverters in this case scenario. However, microinverters are more expensive than string inverters, therefore, it is up to you to decide if it’s worth to pay the extra price for them.
The connection of solar panels is generally organized by maximizing the number of modules connected in series. Series connection of modules (also called string) increases voltage while keeps electrical current the same, which is desirable. The maximum number of modules that can be connected in series is determined by the maximum voltage limit of the inverter. Parallel connections of strings can also be used to increase the power of the array.
The number of MPPT inputs refers to the number of strings that can be directly connected in parallel to the inverter. By making a direct connection from a string to an MPPT input, the inverter will track the maximum point of operation of such string independently from the other strings. The advantage of this method is that any shading or loss factor from one string, will not affect the other string which is connected to a different MPPT input.
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