Product review: Enphase micro-inverter
Enphase Energy is the number one brand in the market for micro-inverter solutions. Enphase micro-inverters are available in a wide range of unique products. Let’s take a closer look.
Today we’re going to take a closer look at Enphase Energy’s micro-inverter.
Enphase Energy is one of the most important companies in the business of micro-inverters, with more than 10 years in the market, more than 14 million production units shipped across the world and more than 580 thousand installations done.
They were the first to develop this type of inverter and have designed a complete system around it that includes inverter, combiner box, storage solutions and monitoring systems which are mixed together to create the Enphase Solar Energy Solution.
This is why we are so interested in sharing this product review with you.
Why use a micro-inverter?
The first question that might arise to a solar designer or a homeowner is why should you use a micro-inverter instead of a typical central inverter?
Let’s analyse some of the advantages of this product.
The first thing that any solar designer thinks about is power. How much power will the array need?
This question will lead to the number of panels that will be mounted on the roof. The designer must also consider losses associated with the system.
In order to better understand the importance of the Enphase micro-inverter, we must first understand the impact of the power losses due to several factors.
One of the most important causes of power losses in solar systems are from mismatch losses. These are associated with a lower power output in a string of modules because each module is not working at its Maximum Power Point (MPP).
If you are not familiar with the MPP, a simple way to understand it is to think that it represents the maximum power output that a solar panel can produce under clear sky conditions.
However, there are some factors that can affect MPP, such as soiling, shading or ageing.
Any of these elements will reduce the power produced by the module.
The problem with a string of modules lies in series connection – what affects one module will affect the others.
This means that the power output of a whole string will be reduced every time if there is more dust (or bird droppings) on one module than on others, or every time a tree shades a side of one module.
When considering large-scale solar systems this represents a high amount of energy loss and the impact of the losses is huge.
That’s why it is an intrinsic design element that should be considered when selecting a central or string inverter.
The great benefit when considering an Enphase micro-inverter is that the energy conversion from DC to AC is done at module level.
In other words, each module that is not affected by soil or shade, will be producing energy at its MPP with no dependence on the performance of the other panels!
This is a great benefit that can be applied to PV systems in all scales, but of course, the bigger the system, the higher the energy savings will be!
Additionally, if one module is damaged for any reason, the rest of the system can still work perfectly and you will only need to remove the damaged panel and replace it. Besides, there is no DC power loss as inverters are placed at the DC output of the panels.
Moreover, an issue when selecting a central inverter is that the strings of modules need to be placed on the same orientation to achieve Maximum Power Point Tracking (MPPT).
If, due to constraints of the location, you need to place your solar panels in different orientations, you will need to make a market research on grid-tied inverters that can work with two MPPT inputs. If you have more than two strings in different orientations then you would need to use another central inverter or consider multiple string inverters that could lead to higher investment costs.
If you use an Enphase micro-inverter you can forget about all those problems, as the modules can be placed in any orientation and the micro-inverter can still achieve MPPT.
As you can see there are huge advantages on selecting an Enphase micro-inverter for the design of a solar system.
Now, let’s take a look at the product offer that the Enphase Energy company has available.
Enphase offers a wide range of micro-inverter solutions for different applications. One of them is the S-Series with two types of models: the S280 and the S230. Both products are UL-listed (UL is a global independent safety science company) and conform with NEC-2014 and NEC-2017.
S-Series micro-inverters are compatible with storage systems including battery management systems, and are designed with grid interaction features to meet utility requirements.
The S280 micro-inverter is rated at 270 VA continuous AC power with a peak AC output power of 280 VA and is compatible with 60-cell modules up to 360 W under Standard Test Conditions (STC).
On the other hand, the S230 micro-inverter is rated at 220 VA continuous AC power with a peak AC output power at 230 VA and is compatible with 60-cell modules up to 300 W under STC.
All Enphase micro-inverter products interact with an Envoy device which acts as the Energy Management equipment of the system and provides a network access to the PV system to measure production, performance and other data.
All Enphase systems are also associated with an Enlighten device, which acts as a web-based monitoring and management software that allows you to visualise energy production and peak power available during the day as well as solving performance issues.
It can be connected to a smartphone which allows you to interact with your system to establish modes of operation. The Enphase S-Series is compatible with the Envoy-S and Enlighten Manager (all Enphase micro-inverters are compatible with this manager).
A very important and particularly interesting feature of these micro-inverters is that they contain an integrated DC and AC disconnector which is a device required by NEC on PV installations.
Regarding over-voltages, these micro-inverters have an internal surge protection.
Moreover, the Enphase S-Series are integrated ground micro-inverters, meaning that the DC circuit inside the equipment is isolated and insulated from the ground, besides, a Ground Fault Protection (GFP) is integrated to the micro-inverter, which is different from other brands of micro-inverters that need a GFP.
Here are other specifications for both inverters:
MPPT Voltage Range
This is the allowable Maximum Power Point Tracking range of the micro-inverter which establishes the maximum and minimum voltage that the algorithm of the device can track to establish maximum power output.
Temperature variations and their effect on the MPP voltage of the panel must be considered to establish the range of the panel, which must be within the MPPT voltage range of the micro-inverter.
Maximum Input DC Voltage
The lower the temperature of a location, the higher the voltage. The open circuit voltage under the coldest conditions must be below this parameter.
Maximum DC Input Short Circuit Current
Must be below the short-circuit current of the panel.
Peak AC Output Power
Reference to real maximum power output in AC.
Nominal AC Frequency Range
Must match the frequency of the grid.
Maximum Micro-inverters Per 20A AC Branch Circuit
There is a limit to the number of micro-inverters that can be placed into a single branch depending on the configuration used (split-phase or three-phase) considering a 20 A protection device.
Peak Inverter Efficiency
Highest efficiency of the inverter.
Enclosure Environmental Rating
Provides the overall protection of the inverter against heat, humidity and dust.
Enphase C250 micro-inverter
The commercial solution of Enphase Energy. This micro-inverter is used with a transformer to meet voltage of 480Y/277V for distribution level and typical commercial applications.
The C250 is compatible with 60-72 cell modules up to 350 W and MC4 connectors.
The typical use of this micro-inverter is to couple it with an auto-transformer or isolation transformer to take the voltage of the micro-inverter to the required utility voltage.
Adjustment of taps in the transformers are necessary to establish the voltage of the grid. It is necessary to install a phase coupler with each Envoy-C (Envoy compatible equipment) to allow communication with the micro-inverters on all three-phases.
As with the S-Series, these micro-inverters come with ground fault protection and surge protection, but a an SPD is still recommended, the same as the S-Series requires.
Enphase D-380 micro-inverter
An interesting configuration is presented with this device.
The D-380 model (also called Twin Pack) houses two micro-inverters individually connected to two PV modules assuring MPPT for each module!
This feature allows for a reduction in the number of components, making the installation easier.
Even though there are two DC inputs with two micro-inverters, there is only a single AC output summarising the power from both sources as can be seen below.
Compatibility is assured with 60-72 cell PV module configurations and they can be used to provide a single phase 240 Vac or 208 Vac three-phase system.
Moreover, these inverters are compatible with MC-4 and Amphenol H4 Type 2 locking connectors.
As with other Enphase micro-inverters, they have an internal surge protection, but it is advisable to place an external SPD.
Particularly for this model the manufacturer recommends the SPD Citel DS72RS-120 for split phase residential application.
Enphase IQ 7 micro-inverter series
Finally, the latest development of Enphase Energy is the IQ Series.
This new product is listed under UL and conforms with NEC-2014 and 2017 to comply with Rapid Shutdown Requirements. It offers three types of models: IQ7, IQ 7 PLUS and IQ 7X Micros.
The new development of this technology as a whole new system is that it performs on a smart grid environment to administrate the power energy production depending on tariffs and electricity rates at your convenience.
A new Enphase IQ Envoy needs to be coupled with the IQ7 Series and is capable of monitoring up to 600 Enphase IQ7 micro-inverters and 39 IQ Batteries.
Yes! The micro-inverters can be coupled with the Enphase Storage Solution, the IQ6 Plus-B1200.
These Lithium batteries have a single capacity of 1.2 kWh, therefore, in order to size your battery system, you must couple as many batteries of this capacity as necessary to comply with your stored energy requirements.
They are sold in a single compartment including a battery-based inverter that uses AC power to charge the batteries and converts DC energy from the batteries to AC energy to feed the panel board when needed.
An important consideration that must be taken into account if choosing this type of storage solution is that the battery set is not suitable for off-grid or back-up purposes, as the battery-based inverter needs the frequency of the grid to operate.
Therefore, the purpose of this system is to increase your self-consumption and reduce expenses when using electricity from the grid, which can be more expensive than the solar energy produced and stored on a $/kW basis.
The difference among available IQ7 models lies in application and size.
The IQ7 and the IQ7+ supports PV modules with 60-72 cells, while the IQ7X needs at least 96-cell PV modules.
Another particularly interesting feature of these models is that they do not require grounding electrode conductors and have a Class II double insulated rating with ground fault protection.
Regarding lightning and surge protections, as with other micro-inverters they have an internal surge protection, but is advisable to add an external SPD.
For this model, the manufacturer recommends the MNSPD-300 from Midnite Solar for residential purposes or the Delta LA-303 lightning arrester for commercial cases.
Enphase micro-inverters offer a wide range of available products. The concept is unique and continuous development maintains this brand as the number one in the market for micro-inverter solutions.
Moreover, considering the numerous inverter options and the infinite PV module possibilities, it might be hard to visualise which micro-inverter would be compatible with your panel considering open voltage circuits and temperature variations.
Enphase Energy offers an online tool to evaluate the module compatibility which is very useful to find out easily which models could be coupled with your solar panels.