Femtogrid is a smart DC grid. It is a 3-wire, soft, a-symmetrical, 380 Vdc, isolated, bi-directional, self-stabilizing, decentralized network designed to distribute DC power and data.The Femtogrid, typically 380 Vdc, is not intended to to be used in a datacentre only, but in the built environment, where people plug their computers, lighting, refrigerators in a DC outlet. Where people have modules, small wind turbines or other sustainable generators and plug it in. Also storage (like small batteries) is easily added to the Femtogrid.
A patented safety wire concept keeps the user free of arcs, electrical shocks, fire, balancing issues, decreases standby power and provides high speed Internet out of your wall outlet. This unique DC grid, the Femtogrid, saves integral 30-50% of the energy consumption at home, small and medium enterprises and buildings. AC grid connected or as an autarkic grid. In 2012 we transported, converted and inverted more than 500 MWh of DC energy with our grid and transported terabytes of data. Femtogrid, the smart DC, sustainable energy grid.The unique and patented parallel Femtogrid architecture builds on 4 mutual reinforcing smart components: 1) Solar Power Optimizers (DC/DC converters), which perform Maximum Power Point Tracking (MPPT) and voltage management per module, 2) safe, reliable and plug & play DC cables, 3) a robust inverter, which performs DC to AC inversion, and 4) a web-based portal for module level monitoring and problem-free service. The Femtogrid solution builds on the following technological advancements.
In contrast to traditional solar Femtogrid uses a parallel instead of a serial architecture for solar panels. Parallel power optimizers ensure the parallel architecture and are used as an add-on by the installer to each solar panel. The parallel architecture is plug & play: the solar panel is connected to the power optimizer, which connects the solar panel in parallel to the inverter.
Femtogrid DC cables have 3 wires: hot (red), cold (blue) and safety (black), whilst standard solar DC cables used by traditional solar have 2 wires: plus (red) and minus (blue). The extra third wire gives Femtogrid the edge to control every single module in the system, as the hot wire is switched off by the safety wire. This makes Femtogrid the safest system.
Using a smart algorithm for the Femtogrid Solar Power Optimizer, each module constantly performs at its Maximum Power Point (MPP), thus maximizing the energy generated per module, and consequently the total solar energy generated. Besides the additional energy production, MPPT per module is faster than MPPT performed by a string inverter with traditional solar.
Femtogrid Power Optimizers convert the output voltage of every module or urban wind turbine to a fixed (constant) bus voltage; the Femtogrid 380 Vdc. At this fixed voltage, the inversion from DC to AC is optimal, regardless of the number of modules used or the environmental conditions. The fixed voltage mode enables a robust inverter design for optimal efficiency and reliability. Furthermore, this fixed voltage mode makes it possible to connect different DC sources to the fixed bus voltage. The output voltage of single DC sources no longer matters; it’s the fixed bus voltage that matters. As a result, different types of modules, urban turbines, or even different types of DC energy sources can now be mixed & mingled in one (hybrid) system.
The inverter feeds all Femtogrid Power Optimizer via the additional third (black) wire. This gives Femtogrid the edge to control every single module in the system. A shutdown of the inverter will result in a shutdown of all Femtogrid Power Optimizers. This feature makes the Femtogrid Inverter a very important linkage in the total system. With our parallel system architecture the voltage of a single module is, as as result, the open circuit voltage of that particular module. This makes Femtogrid the safest system.
Knowledge is power. All Femtogrid Power Optimizers continuously measure and communicate a range of module characteristics such as the (DC) power and energy generated, temperature and voltage per module. In addition, the Femtogrid Inverter also continuously measures and communicates the (AC) power and energy generated by all modules together. The data of all Femtogrid Power Optimizers and Femtogrid Inverters is transmitted wirelessly via ZigBee to the Femtogrid Monitoring gateway. This gateway sends the data either via GSM or Ethernet to the remote Femtogrid monitoring server, which displays the data in a user-friendly format for full visibility.
A key contributor to the efficiency and overall reliability of the Femtogrid Power Optimizer is the integration of the underlying components into an Application Specific Integrated Circuit (ASIC). The integration of all functionalities into the ASIC improves the overall reliability and performance of the Femtogrid Power Optimizer. The ASIC technology is now used as an add-on version for modules. This year, however, it will also be used in an integrated version; the Femtogrid Power Optimizer will be integrated into the module's junction box.