Reference project: Zero Grid Export

Location: Hughes Medical Center, Anguila, British West Indies

Generating Power: 60 kWp

Inverters: SMA

Monitoring Hardware: Solar-Log 1200, Solar-Log® Commercial Revenue Grade Meter plus consumption meter

Monitoring Platform: Solar-Log WEB Enerest™

Utility Requirements: The local utility company charges for any solar PV power that is exported to the grid. To avoid these charges, the Solar-Log® adjusts the output from the inverters to reduce the PV production when the building consumption is below PV yield.

Solar Data Systems, Inc., along with Comet Solar, helped Hughes Medical Center in Anguilla avoid Feed-In charges by installing a Solar-Log 1200, creating a Zero Grid Export solution (ZGE). 
Hughes Medical Center is a modern, private medical facility in Anguilla, British West Indies. This small Caribbean island is best known for beautiful beaches and high end tourism product, but this is not the only attraction. Local plastic surgeon, Dr. Lowell Hughes, built his dream facility in 1999, offering modern medical care to local patients and international visitors. The facility enhanced Anguilla’s tourism product by adding medical tourism as an option.

After the business was launched, Dr. Hughes looked for solutions to reduce costs. One of his main efforts has been to lower the cost of electricity at the clinic. Anguilla has some of the world’s highest electricity costs and Dr. Hughes recognized the crippling effect of those costs on his business.

Dr. Hughes enlisted local solar installer Comet Solar to install a 30kW rooftop grid tied system, at that time the largest solar installation on the island. The installation was successful in reducing costs but still left a large portion of the daytime energy usage uncovered, so the intrepid Doctor decided to enlarge the installation. He commissioned another 30kW of ground mounted solar panels behind the clinic, constructed a berm to surround the system and keep it safe from high winds.

Once the system was put into operation, it became apparent that the clinic was not receiving the benefits that the owner expected. Metering equipment revealed that the utility was charging for any excess electricity that flowed out to the grid. “We knew going in that the utility would not readily pay for any electricity we exported, but we were not aware that there would be charges on that power,” Dr. Hughes explained. On the weekend, when the clinic is closed, we can export 80% of the power we generate. We would be better off if we turned the solar system off on the weekend.”

After a period of research, Comet Solar identified Solar Data System’s Solar-Log® as the only commercially available equipment to control the export of power. The Solar-Log® metering equipment adjusted the output of the SMA inverters to reduce the production of electricity from solar when it sensed excess power being exported to the grid. During the week, this resulted in modest savings, but over weekends and holidays, the power management was able to reduce costs through excess power to almost zero.

The graph above shows the consumption of power in red and the production in green, closely following the consumption. In fact, the Solar-Log® can achieve almost zero demand and export, perfectly matching the solar production to the facility’s demand.