At Comsys we made an interesting installation of a DC microgrid at a metal factory in a rural area of Sweden.
The factory is located in an area with large forests just around the corner and also in an area of Sweden that often has heavy storms during autumn and winter time. All in all this is not a good combination with the overhead power lines feeding the factory and they suffer from regular power outages that stop the production lines with large costs as a result.
The main factory have a cluster of servers that supports their satellite production units with production data, order and invoice systems etc. In order to keep all production units running the servers housed in the main site must have power or all production units will stop working.
In addition to feeding the servers, the lighting in the warehouse is also fed from the 350V DC microgrid, meaning that at least "office and warehouse work" can still be done at the premises during a power outage even if the large mega-watt production line of course is hard to run only by PV or batteries.
On the rooftop, 100kW 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, maximising the number of hours with internally useable energy production.
The solar panel installation is divided into 27 strings connected to lighting and surge protection units placed on the roof.
And unfortunately, they suffer from heavy thunderstorms too!
From the roof, individual PV string cables goes down to our PV charge regulators (NetTracker) housed in 19" racks placed just under the roof. In the left rack the 350V DC rectifiers, distribution modules and battery supervision modules are housed.
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 PV charge regulators and the rectifiers are passive, avoiding a "single point of failure" SW control module.
In case of power outages the load is supported by a large lead-acid battery consisting of two strings, each with 26 blocks of 12V/200Ah, giving minimum 8 hours of backup energy supporting the load (servers + lighting).
During sunny days the backup time is very long as the load is fully driven from the solar panels
The DC LED lighting fixtures are our latest and super-efficient High Bay models that we developed for heavy, industrial use. They are dust and water splash protected and also supports DALI control.
The high-bay LED fixture uses the latest and brightest Samsung LEDs on the market together with a highly efficient DC LED-driver.
The DC cables used in the installation is a new cable from NEXANS that also contains 12 optical fibres (DC_EQLQ_700V_3G2,5+12_SM) a cost effective way to get both power and optical fibers installed.
The factory not only installed a new internal DC power micro grid, they also at the same time got a brand new fiber-optic network installed.
A very professional local installation company ELAJO made the installation on site and 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 successful!