The Universal Controller
DC pumps have become the norm for off-grid solar installations, but are very expensive compared to their AC counterparts and require specialized controllers that support a single pump or family of pumps. In contrast, AC pumps and motors have historically been at a significant economic disadvantage to their DC counterparts because they typically required twice the PV capacity of an equivalent DC pump to effectively operate and required a sometimes complex mix of power electronics. Additionally, lower cost, single phase pumps were previously not even an option for off-grid solar. With PicoCell the rules have changed.
The PicoCell can run either single or three phase pumps, both 120 and 230Vac voltage level, and 50 or 60Hz, just by selecting the correct DIP switch combination that matches the AC pump’s parameters. Because the PicoCell is a firmware based architecture it can “shape” the power to accomodate the initial power surge that creates the AC load’s need for the excess solar capacity in the first place. By representing an integrated system that incorporates the functionality normally served by a complex mix of system components such as an inverter, variable frequency drive, MPPT controller, voltage boost and phase initiator (for 3 wire motors), the PicoCell greatly simplifies the design, procurement and installation of a solar pumping system. All of this functionality is in one integrated device with a form factor smaller than the common tissue box.
The PicoCell represents a truely universal solar controller where the same unit can run any AC motor load: pump, compressor, fan, etc. To optimize system efficiency the unit generates a true sinewave with variable frequency to match the available power coming from the solar PV with pump power at all times.
PicoCell operates both single phase and three phase AC pumps, even the single phase 3-wire that are ubiquitous in the North American market. Industrial VFDs don’t have the ability to run single phase AC loads because they are designed to be grid connected. PicoCell utilizes cutting edge SiC high speed switching mosfet devices, which not only results in 92-95% range efficiencies, but also contributes to the unit’s compactness due to low operating losses.
Instead of building a mechanically and electrically unique configuration for every combination and permutation of application variables, the PicoCell uses adaptive firmware to achieve a “one controller fits all” objective. A series of clearly labeled dip switches are configured at installation to select application variables and the controller then uses the appropriate adaptive firmware to provide appropriate control of the loads.
This takes the complexity out of the hands of the user or installer and automates the process in software. Rather than having to integrate several different functional components, the PicoCell runs one holistic and integrated algorithm that incorporates all of these functions.
DC pump controllers are based on legacy electromagnetic design concepts that have not changed much over time. They are typically limited to operating one pump or small family of pumps They are reminiscent of the large arcade games of the eighties that were the size of a refrigerator and only ran a single game versus the modern smart phone that can play virtually any game. The PicoCell represents the smartphone of the power electronics world. Even with it’s extremely small form factor and low price it can drive any AC motor with any solar array. Pick your favorite pump, there’s an app for that.
The PicoCell effectively provides five sometimes separate system components into one fully integrated controller:
- Maximum Power Point Tracking (MPPT) Controller
- Variable Frequency Drive (VFD)
- Voltage Boost
- Phase Initiator
Of these functional elements it is the PicoCell’s patented voltage boost that has the most dramatic impact on customer economics. 80% of the total cost of a typical solar pumping installation is comprised of the PV array. For small AC pumps PicoCell is capable of cutting that PV capacity requirement in Half. Combined with the consolidation of the power electronics, total project costs are reduced on average by 50%.
For distributors the universality of the controller represents an opportunity to reduce and simplify inventory. Pick any AC pump, any panels, add a Pico the mix and you are done.
One device now does the job.
Realtime power blending opens up many more applications to solar power. Some applications require a constant power level regardless of the current weather time of day. In other instances, the high cost of grid or diesel power is a motivator to offload as much as possible to solar.
By utlitizing the optional grid, battery, or generator hybrid controllers with the PicoCell, the system can blend power sources in realtime. For instance, as a day turns cloudy, instead of seeing the height of your fountain fluctuate as the VFD responds, the fountain now maintains its full pressure and flow with the Pico system drawing the balance of power from the grid, battery bank, or a generator. In areas where the cost of electricity is high this can represent a ROI of approximately 15 months. The diagram below illustrates the blending of power from multiple sources, utilizing solar as much as possible to minimize operating expenses.
Another benefit of SolHybrid is that it provides power factor correction for single phase AC loads when connected to the grid through the SolHybrid box. So, previously heavy inductive loads, with huge in-rush current, operate at unity power factor with an additional soft start feature. Diesel/gasoline gen-sets can also be connected to the SolHybrid box, and used as source of power instead of grid.
In other situations an application may not require a 24/7 duty cycle but will require some after dark operations. An example would be in the aquaculture market where oxygen levels must be maintained above critical thresholds overnight but the cost of electricity provides a motivation to avoid constant night time operation. Another operating mode is available leveraging either an external timer or a communication module to program the operating times during the evening to achieve operational objectives while minimizing operating expenses.
If each one of these inductive loads has a PicoCell controller that decouples the inductive load from the micro-grid, the PicoCell controller will make sure that the inductive load does not generate a power spike on the grid. Furthermore, because PicoCell has bi-directional communication capability, it is possible not only to monitor inductive loads operation and provide power metering services for the micro-grid operator, but also to schedule operation of those inductive loads based on the excess power that might exist in the microgrid. This occurs when the battery bank that provides the microgrid’s stability is fully charged, while renewable energy sources (solar or wind) are still producing power, so during that time, certain operations like pumping water to a tank or waste water treatment, can be scheduled by communicating between a centralized microgrid controller and PicoCells that are distributed around the microgrid’s periphery.
Ultimately, from the power side PicoCell can be connected to wide range of DC voltages (60-380Vdc), but also to variety of standard AC voltages (single phase: 120V or 230V, as well as 208, 400, 460Vac three phase). As a result, PicoCell is flexible to connect to any DC or AC microgrid system.
The PicoCell controller is among the rarest devices in the world. It can run single phase inductive loads: pump, compressor, and fan for both 120Vac and 230Vac and either 50 or 60Hz frequency. The same device can run even 3-wire single phase motors that are ubiquitous in North America, hence displacing the so called “control box” that consists of a relay and starting capacitor.
The true technology breakthrough is in the PicoCell’s control algorithm that is embedded in the firmware. Instead of utilizing a relay and capacitors for starting the single phase motors, PicoCell provides variable frequency drive capability with a true sinewave of variable voltage magnitude and frequency to run the single phase inductive loads even when they are powered from solar, wind, or even DC low voltage AGM batteries. If single phase motors are driven by a PicoCell that is connected to both electrical grid and solar, wind or diesel, PicoCell enables power factor correction, to present unity power factor for the electrical grid.
Industrial VFDs don’t have the ability to run single phase AC loads because they are designed to be grid connected, so the power factor correction (PFC) and DC link circuits in industrial VFDs are designed for three phase motor loads only. However, PicoCell’s hardware design is flexible and has additional boost circuit hardware that has dual functionality. It enables wide input voltage range from solar PV, but also filters a ripple from single phase AC motor loads. This filtering algorithm is embedded in PicoCell’s firmware.