Maximizing the power of renewables

“Utilizing more than 40 years of experience in high efficiency solar power conversion, Eltek Valere has developed the groundbreaking THEIA HE-t photovoltaic inverters.”

A photovoltaic installation typically consists of an array of solar panels to convert the energy from sunlight into direct current (DC) and an inverter to then convert the DC into alternating current (AC) so that power can be fed into the mains.

One of the most important characteristics of a photovoltaic inverter is efficiency, and there is a constant need to increase efficiency to as close to 100% as possible.

There have traditionally been two types of PV inverter with distinct differences:

Isolated inverters contain internal galvanic isolation between the DC input and the AC output. These units are able to have one of the DC poles grounded, and therefore are suitable with all types of photovoltaic modules. However, these isolated inverters normally have a low efficiency and heavy weight due to the transformer inside providing the galvanic isolation.

Transformerless inverters contain no galvanic isolation between the DC input and AC output and typically have lower weight and higher efficiencies, as there are no losses associated with a traditionally heavy transformer. However, they are not able to be used with all photovoltaic module types. Generally, this is because there is no isolation between the DC and AC. Therefore if one pole of the DC input were to be grounded, it would mean that the AC side of the inverter would also be grounded- which is not something that electricity companies like to have happening on their network. There are some transformerless inverter topologies which are able to have the negative grounded, but these units then suffer a loss of efficiency.

Which one to choose?

Traditionally, isolated inverter has been used mainly with Thin Film (Amorphous Silicon) panels due to the requirement of grounding to prevent degradation of the panel. In addition, it electrically isolates the input from the output which is an important safety aspect and lowers the possibility of disruption to the grid which may invite heavy penalties. There will also be a lower risk of shock hazards for installers and engineers who maintain the system as one pole of the installation is tied to earth and provides a path for fault currents.

With Crystalline (Poly-crystalline and mono-crystalline) panels, transformerless inverters have normally been used due to their higher efficiency, lower cost, smaller size and weight.

Taking these challenges into consideration, and utilizing more than 40 years of experience in high efficiency power conversion, Eltek Valere has developed the groundbreaking THEIA HE-t photovoltaic inverters, which are an isolated range of grid-tie inverters suitable for use with any PV technology. With a peak efficiency of 97.3%, they have the highest power conversion efficiency in the industry for isolated inverters, and are even higher than most transformerless inverters in the marketplace. With higher efficiencies equating to lower losses, and lower losses meaning less stress on components, a further benefit is that of a more reliable inverter, with a longer lifetime. This is clearly an important factor for equipment used in PV plants which have expected lifetimes of 25+ years, as failures of any kind may result in unreliable energy harvesting, lost revenue and service and maintenance costs. In terms of form factors such as weight and size, it is similar to other transformerless inverters or even smaller.

All power levels in the range include an integrated web server with an intuitive user interface. For sites with multiple inverters, a single inverter can act as a central monitoring hub to collect data and provide a single point of access. On the front of the inverter, the color display with touch sense button is also one of the first in the industry and provides an excellent user experience.

An onboard web server included by default eliminates the need for additional and expensive dataloggers or interconnected devices for small to medium installations.

The sophisticated inverter communication system used in the THEIA He-t can be connected to a single inverter in a PV power generation plant composed of up to 100 bus-linked inverters via an Ethernet cable for the user to be able to read the total site performance information on a PC, either locally or remotely.

In summary, thanks to the state-of-the-art high frequency transformer technology, the single phase THEIA HE-t inverters are the only devices on the inverter market that combine maximum efficiency (97.3 per cent) with the safety advantages of galvanic isolation. The THEIA HE-t series inverters can be used for crystalline and thin film photovoltaic modules of all types. Eltek Valere offers the THEIA HE-t string inverters with an AC output of 2.0 to 4.4 kW. Even at low outputs, the inverters provide high efficiency over a broad performance spectrum and can be used anywhere in the world. For operators of photovoltaic systems, this means maximum returns on investment (ROI). Photon Profi, a well-known German solar energy magazine tested and evaluated these parameters thoroughly. Eltek Valere’s THEIA 4.4 HE-t was awarded the magazine’s top rating, ‘very good’ for performance at both medium and high solar irradiance.

“Essentially all results from the Photon test laboratory correspond with our own testing and also what the Austrian Institute of Technology has previously tested and verified,” says Ingvar Apeland, Executive Vice President of the Renewable Energy division at Eltek Valere. He adds, “Eltek has been setting the standards in the power conversion industry for years and is continuing this tradition with its high efficiency policy and the THEIA HE-t line, and we feel the overwhelming interest from the market for our products confirms the validity of our approach.” In addition to the high efficiency ratio, the THEIA HE-t series inverters are compact, robust (IP65 and NEMA 4X protection class), guaranteed to be long lasting and virtually maintenance free. A flexible connection set, multi-language functionality, backlit color display and integrated web server enable quick configuration and easy operation- under very different conditions and for any type of country-specific requirements. At locations where several THEIA HE-t inverters are in use, it is possible to install one unit as a central monitoring hub for a single point access and to transmit its settings to all of the other inverters.

Utilizing a combination of benefits from both isolated and transformerless inverters, plus additional features and benefits, the HE-t inverter is the clear choice for photovoltaic installations.


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