HMS Photovoltaik is also used interchangeably with the HMS series of microinverters manufactured by Hoymiles for photovoltaic, or PV, systems. A microinverter is a power inverter at the individual module level . It is not a centralized inverter , but instead an inverter which converts electricity from a group of solar panels in place of a traditional string inverter . This means the direct current (DC) produced by individual solar panels can be converted to alternating current (AC) near the point of generation.

Hoymiles HMS microinverters are available in a number of configurations, including models designed for use with two or four solar panels. Depending on the model, they can provide independent maximum power point tracking (MPPT), module-level monitoring, rapid-shutdown capabilities and communication with monitoring equipment.

If you’re a U.S. homeowner, installer, or solar lover, understanding what HMS Photovoltaik means can help you compare microinverter technology to other solar system designs. Exact specifications, certifications and approved applications vary by model and local electrical requirements.

What Does HMS Photovoltaik Mean?

HMS Photovoltaik steht für Photovoltaik mit HMS-Mikro Wechselrichter Technologie von Hoymiles. “Photovoltaik” is the German term for photovoltaics, the process of converting sunlight directly into electricity using solar cells.

An HMS microinverter sits behind or near the solar modules and converts the DC electricity produced by the panels into AC electricity that can be used by electrical loads or supplied to the grid in a properly designed grid-connected system.

Hoymiles describes its HMS products as module-level power electronics. For example, the HMS-600/700/800/900/1000-2T series can connect up to two PV modules, with independent MPPT and module-level monitoring.

This module-level architecture is one of the main reasons microinverters are considered for residential and small commercial rooftop installations.

How an HMS Microinverter Works

Solar panels create electricity as Direct Current , or DC . The vast majority of electrical devices in a home in the U.S. are designed to run on AC power . So a solar setup needs an inverter to convert the electricity to a usable form .

HMS microinverter does the conversion at the solar-panel level. Power from each panel enters the microinverter which converts the power from DC to AC.

Then the system can connect the AC output to the building’s electrical system, by way of properly designed wiring and protection equipment.

One of the important features is maximum power point tracking or MPPT for short. MPPT allows the inverter to continuously search for an operating point that can allow a solar module to produce as much available power as practical under changing conditions. Hoymiles documentation describes its HMS microinverters as using module-level independent MPPT technology.

Key Features of HMS Photovoltaik Systems

Module-Level MPPT

The advantage of HMS architecture is independent MPPT. Module-level optimization can reduce the impact a poorly performing panel has on the rest of the array when individual solar panels are receiving different amounts of sunlight due to shading, orientation, dirt or other conditions.

HMS-2000-4T series provide independent MPPT for connected panels and HMS-1000-2T series provide two independent MPPT channels.

Module-Level Monitoring

HMS microinverters can also be combined with compatible communications equipment for module level monitoring.

That means installers and system owners can get data on individual modules, rather than just the aggregate output of a whole solar array. Such information can help to identify performance differences and potential faults.

Hoymiles says data from its microinverters can be collected by its DTU communication equipment and sent to the company’s monitoring platform.

Two-in-One and Four-in-One Designs

The HMS family is available in many different configurations.

The HMS-600 to HMS-1000-2T series is a 2-in-1 microinverter, i.e., one unit connects to two solar panels.

More powerful HMS models such as the HMS-1600, HMS-1800 and HMS-2000 series can connect up to four panels. For this family Hoymiles lists output ratings to 2,000 VA.

The decision on these configurations will depend on the solar panel specifications, system size, electrical design and regulations.

Rapid Shutdown Support

Another key consideration for rooftop solar systems in the United States is rapid shutdown.

The manufacturer lists some of the Hoymiles HMS models as compliant with applicable U.S. rapid-shutdown requirements including NEC Article 690.12. Hoymiles refers to its HMS-1600/1800/2000-4T-NA series for North America PV rapid shutdown equipment, pointing to the requirements of NEC-2017 and NEC-2020.

HMS products must be verified for compliance with the actual product model, installation design and local authority requirements. You must not assume that all HMS products are compliant.

HMS Photovoltaik for Residential Solar

Microinverter technology is typically used for residential rooftop applications.

If a home has multiple roof orientations, partial shading, or other conditions where panel-level control may be beneficial, then an HMS system can be helpful. By placing the microinverter near the solar modules, homeowners can also gain more insight into the performance of individual panels if the system is paired with compatible monitoring equipment.

If it’s a small install, such as a rooftop, then a two-in-one HMS microinverter may be a good option. Larger installations with high-powered solar modules might instead use a four-in-one model.

You don’t just pick the model that has the highest output rating . Your choice should be determined by the electrical characteristics of the panels and inverter .

HMS Photovoltaik for Commercial and Larger Installations

Microinverters aren’t only for small residential systems. Several microinverters HMS can be combined to bigger solar systems.

The HMS series from Hoymiles is described in documentation as both single-microinverter and multi-microinverter configurations. For a larger rooftop system, multiple units can be connected together and the communication and monitoring equipment can manage system information.

But in commercial projects, system designers need to consider other factors such as electrical capacity, equipment placement, branch limits, communications, grid requirements, maintenance access and local code compliance.

Advantages of HMS Photovoltaik

The modular design is one of the major benefits of the HMS microinverter technology. In a solar system you don’t have one inverter that collects all the DC electricity from the array and converts it.

Module level MPPT can also reduce the mismatch between solar panels. If one module is shaded or the output is reduced, then the other modules can continue to operate to their own conditions.

Another plus: monitoring. With compatible communication hardware, users will have easier access to detailed performance information and be able to identify potential problems. Hoymiles specifically points out module-level monitoring and maintenance benefits of its microinverter systems.

Its modular design also allows flexibility for the extension or design of systems with differing roof sections.

Things to Consider Before Choosing HMS Photovoltaik

HMS microinverters have some useful features, but that doesn’t automatically make them the best solution for every solar installation.

The inverter should match the voltage, current and power characteristics of the solar panel. Operation outside approved electrical specifications of the equipment can lead to performance and safety issues.

Second, the system should be designed to the local electrical codes and utility requirements. Requirements vary by jurisdiction and utility in the US.

Third, some monitoring or configuration functions may require communication equipment. Hoymiles has DTU products for microinverter communication and monitoring systems.

Finally, professional installation makes a difference. Hoymiles recommends that microinverters are installed by qualified personnel.

HMS Microinverter vs. Traditional String Inverter

The main difference is where the power is being converted.

Normally in a traditional string inverter the power is provided by a number of panels in series. Conversion is done at the module level by a microinverter.

Simple roofs with good sun and the right panel arrangement are ideal for string inverters. Microinverters can be helpful when panels are shaded or have different orientations.

No single design is better than all others. The best option will depend on the roof, arrangement of the panels, size of system required, budget, electrical needs and long term maintenance strategy.

Is HMS Photovoltaik Suitable for U.S. Solar Projects?

HMS microinverters are suitable for solar applications in the U.S. if the selected North American model is listed to the certification required and installed to all applicable codes and utility requirements.

Hoymiles, for example, lists some North American HMS models, along with compliance information related to NEC rapid shutdown, UL 1741, IEEE 1547, and other applicable requirements.

However, not all U.S. locations are approved for all HMS models; users should not assume so. Product versions can vary by market so installers should consult the exact model documentation before buying or installing equipment.

Conclusion

HMS Photovoltaik is a concept for solar power conversion with HMS microinverters at module level. This technology is suitable for a variety of modern rooftop PV systems, thanks to its features such as independent MPPT, module-level monitoring, multi-panel configurations, and rapid-shutdown support.

The most important step for U.S. homeowners and businesses is to select the right model for their particular solar panels and electrical design. Check Product Specifications, Certifications, Utility Requirements and Local Codes before installation.

A good solar system should look at the bigger picture when determining the right inverter for the job, not just the inverter’s advertised power rating. This includes panel compatibility, roof conditions, shading, monitoring needs, safety requirements, installation costs and long-term serviceability.

HMS microinverter technology, when designed and installed by professionals, can be a practical approach to individual panel level solar energy management and give system owners greater insight into photovoltaic performance.