Nice Microgrid: Solar, Storage, and Reliability
Tom Lombardo posted on August 05, 2016 |
In a world where the grid is "too big to fail," microgrids deliver reliability, cost savings, and re...

Way down in the south of France, an experimental microgrid is demonstrating both the technical and business sides of local power production and distribution. The Nice Grid Project combines rooftop photovoltaic resources, strategically placed battery banks, and a smart control system, all of which provide on-site generation, peak load shifting, and islanding. I recently attended a webinar that gave an overview of the project, so I thought I'd share some of the details with you.


Nice (pronounced "neese") is located at the end of a major distribution line, making it susceptible to power outages, as well as brownouts during high demand periods. The microgrid project, commissioned by French grid operator Electricité Réseau Distribution France (ERDF), was conceived in 2011. Its mission is to serve as a test and demonstration site - a proving ground for grid-level energy storage and renewable energy integration.


Solar Production

A combination of residential and commercial rooftop arrays, spread over 500 buildings, produces up to 2 MWp of power. These grid-tied arrays ease the demand from the grid during peak hours, such as summer afternoons. They accomplish that and then some, often generating more surplus power than the grid can accept.


Storage

Since the PV arrays often go above and beyond the call of duty, microgrid engineers designed a multi-layered, distributed energy storage system. At the point where the high voltage grid enters the region, there's a 1 MW/560 kWh battery bank. The medium voltage/low voltage substation features a 250 kW/620 kWh storage unit. The low voltage side includes a pair of 33 kW/106 kWh batteries, and eighteen residential customers agreed to have 4 kW/4 kWh behind-the-meter storage systems installed. 

Each storage unit houses a bank of Saft maintenance-free lithium-ion batteries controlled by a Socomec SUNSYS PCS² power conversion and storage system. The control system is scalable,  hot-swappable, works with nearly any battery and supercapacitor technology, and boasts a 97% efficiency rating. A built-in smart cooling system allows it to work at temperatures from -5 °C to +60 °C. Saft claims that its batteries have a 95% round-trip efficiency and a twenty-year lifespan, even with daily deep discharges, and they're made from highly recyclable materials.  



Islanding

In the event of a grid failure, the Nice microgrid can disconnect from the grid and keep the juice flowing to its customers through a combination of solar, storage, and automatic switching. The islanding system is capable of maintaining power for up to five hours.

Power Management

Moving electrons among various resources and loads is quite the feat of choreography, so the Nice Microgrid uses GE's Grid energy management system (EMS). In addition to monitoring production and consumption through a cadre of smart meters and sensors, the system also incorporates weather forecasting, which allows it to accurately predict solar production. It sends text messages to select customers, offering lower electric rates when solar production exceeds local demand. For example, a coffee shop in the district roasts its own beans. The roasters are energy-intensive, so the shop will fire them up when the rates are low. On a fully-automated level, smart water heaters can turn on when solar production is high, allowing them to serve as a form of thermal energy storage. This type of load-shifting allows the excess solar power to be used locally, with battery storage as a second option.


Results

The microgrid successfully reduced peak grid demand during winter and summer months. On cold winter days, stored energy reduced grid demand by 43%. In the heat of summer, the photovoltaic arrays worked overtime to provide electricity for cooling, with excess energy going to the battery banks.  


On the human side, customers were happy to have more control over their energy consumption, from both a financial and environmental standpoint. Everyone wants to save money, but the people also have favorable opinions about using more solar power and maintaining energy security through distributed generation services.


In a world where the grid is "too big to fail," microgrids deliver reliability, cost savings, and renewable energy integration. Nice!



Images courtesy of ERDF – Electricité Réseau Distribution France

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