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A solar driven, 350V Direct Current, datacenter!

Well, not entirely correct, but for part of the load YES.

Solar Rooftop

At Comsys we recently made a 350V Direct Current installation with rooftop solar at the Blix Solutions datacenter in Oslo, Norway.

Blix Solutions are at the forefront with their system solutions and they have many interesting and eco-friendly installations in their datacenter. They are housed in a multi-tenant building where they use the top floor for the datacenter. The building was originally built to house small factories and warehouses that were moved just outside Oslo city center to make room for offices and residential buildings in the city.

They suffered from high electricity cost in that part of Norway and wanted to try DC.

In order to make the installation more energy efficient and also include solar energy they wanted to install our Direct Current UPS. 

Comsys Application

The DC UPS is working with 350VDC and uses TN-S grounding, all according to the ETSI as well as the Current OS specifications. In case of power outages the load is supported by two lead-acid batteries housed inside the UPS cabinet giving minimum 20 minutes of backup energy supporting the load, during sunny days the backup time is very long as the load is fully driven by the solar panels. To increase the power we can daisy-chain several cabinets and install up to 1MW of DC power in the UPS room.

Rooftop installation.

On the rooftop, 13kW of solar panels are installed in East-West orientation, the East-West orientation was selected to limit the mid-day peak and give a smoother production curve with higher yields during morning and afternoon, maximizing the number of hours with internally useable energy production.

Rooftop installation

The solar panel installation is divided into 3 strings, connected to Comsys product “PV protector3” (overvoltage, overcurrent, short circuit) that makes sure no surge voltages are transferred down to the UPS and the datacenter.

From the roof, individual PV string cables goes down to our PV charge regulators (NetTracker) housed inside the UPS cabinet.

None of the "green" PV energy is lost in conversions DC/AC.

The NetTrackers in the DC UPS have some nice features; the most important is that the PV energy is never converted to AC, instead a super efficient DC/DC converter with 99% energy efficiency takes care of the regulation and MPPT.

-Another important feature is that the NetTrackers are fed by the input from the PV panels which means that the energy consumption is zero at night and during the long, snow-filled Scandinavian winter months no energy is lost.

And they are hot-pluggable, when the power demand rises, more modules can be plugged into the rack.


The system prioritize energy coming from the PV installation and when the available PV energy is not enough to support the load, the rectifiers seamlessly fills in the rest of the energy from the grid. Power sharing between the NetTrackers and the rectifiers is passive, avoiding a "single point of failure" SW control module.

The rectifiers have 97% energy efficiency and a power factor close to 1 so also grid power is handled with great care.

Load distribution.


Load distribution from the DC UPS is protected by DC MCBs and all racks connected have dual feeds (A+B). Breaker to the right can isolate the PV strings for maintenance.

Above the racks our 32A CEE DC connectors connects the racks to the distributed power.


"Industry standard" Saf-D-Grid connectors.

In the racks our PDUs are used to feed the load. The rack PDUs have internal protection fuses and triple-function indicator LEDs to signal input voltage, correct polarity and working fuses. The rack PDUs have Andersson Saf-D-Grid connectors for the load.

Cisco routers

Cisco routers.

The main loads are large routers from Cisco that handles all communication and connects all Blix customers to the datacenter. Blix Solutions have a large fiber network that covers all of Scandinavia and large parts of the northern Europe.

The Cisco routers have power supplies with Saf-D-Grid input connectors and can use any voltage between 280-400VDC.


Heat recovery.


Because the building originally was designed for industrial use, it was relatively easy for Blix to also design a system for heat-recovery to heat the rest of the building where the other tenants have their location. As the number of datacenter customers is growing fast there are plans to connect the building to the nearby district heating in order to also heat other buildings in the area!

Installation cables.

The DC cables used in the installation are N1XV, rated 1kV with PEX insulation, that can be used indoors as well as outdoors.


The installation in the datacenter was made by the local Norwegian companies NTC Services and Astracom AS. Because this is a TN-S grounded installation (even if DC was new to them) training of the installation guys was minimal and the end result was very good!