Project overview

The Nice Grid project is based in the municipality of Carros in the Alpes-Maritimes department, near Nice on the Côte d’Azur. Carros is in the Nice Urban Community area, and within the ‘Eco-Valley’ National Interest Operation. Carros is on the periphery of the French transmission grid, making its electricity supply a structural challenge, but the town has abundant sources of renewable energy – especially solar.

The project objective is to develop a smart electricity distribution grid that harmoniously integrates a high proportion of solar photovoltaic (PV) panels, energy storage batteries, and intelligent power meters – the Linky smart meter, developed by ERDF – installed in the homes of volunteer participants. The project plans to install 2500 Linky units by the end of 2015.

By giving energy users the opportunity to manage their power consumption and budget, the Nice Grid aims to turn passive consumers into active ‘prosumers’ (producer-consumers), representing a mix of residential users, business owners, and operators of apartment buildings.

To this end, the four-year Nice Grid smart solar district project will examine the various technological challenges involved in implementing future smart grid system concepts. It began in January 2012, and will run to December 2015. It will include a high proportion of solar PV panels connected to distributed energy storage systems.

Funding and partners

The budget for the Nice Grid project is approximately €30 million, of which €11 million is being provided by the French government and the European Union. This public funding comprises €7 million from the European Commission, and €4 million in refundable advances and grants from the French environment and energy management agency ADEME, following approval by the Commissariat Général à l’Investissement (General Commission for Investment).

This smart grid demonstration project is led by ERDF (Electricité Réseau Distribution France), which manages the national low- and medium-voltage electricity distribution network. The other partners are electricity generation company Alstom, electric utility EDF (Électricité de France), battery manufacturer Saft, and other industrial partners and innovative SMEs such as wireless sensor company Watteco and the EDF subsidiary NetSeenergy, a specialist in energy management for buildings.

Solar energy in the Nice Grid

The Nice Grid project seeks to efficiently supply the local grid with a substantial amount of solar-generated power. Homes, businesses, and industrial facilities are being equipped with solar panels, with a target of 1 MWp (peak, i.e. nominal power) of total solar PV generation capacity. The novel aspect of the Nice Grid project is that energy storage capability is being added to the power distribution system, allowing ‘reserve’ energy to be made available when needed.

When solar panels produce a surplus of energy during the day, it may be stored and used whenever it is needed to compensate for fluctuations in solar generation, cover peak demands, and generally to contribute to the balance of supply and demand within the distribution grid. The Nice Grid project is storing energy in Li-ion batteries installed at various points on the power grid.

The energy generated by the solar panels on the roofs of homes and buildings in Carros, and stored in the batteries installed throughout the grid and on the premises of volunteer consumers, will enable the district to operate as an autonomous ‘island’ for transitional periods, i.e. without taking electricity from the main grid.

Lithium-ion energy storage from Saft

The Nice Grid project features energy storage as an integral part of the local power distribution network. The primary partner for the energy storage component is Paris-based Saft, a leading global specialist in the design and manufacture of high-tech batteries for industrial applications.

The project is the first life-size demonstration in mainland France of the efficiency and flexibility associated with electricity storage using Saft’s lithium-ion (Li-ion) battery systems integrated at three grid levels: at the originating substation, at several distribution substations, and at the residential level. The total storage capacity is about 1.5 MWh.

Energy storage contributes to optimising overall power flows within the smart grid, and improving the local grid’s capacity to use intermittent renewable energy sources. The project also enables testing of multiple functionalities including load levelling (with regard to both production and consumption of electricity), plant shutdown management, and efficient management of the multiple contributors to energy production and consumption involved in future grids.

The energy storage challenge

The Nice Grid project is testing several types of Li-ion energy storage technology, with the deployment of a total 1.5 MWh of Saft batteries installed at three distinct levels of the electricity distribution network:

• One 560 kWh/1.1 MW Li-ion Intensium® Max containerised battery system at the Carros primary substation, which links ERDF’s distribution network to the transmission network of Réseau de Transport d’Électricité (RTE), the French high-voltage electricity transmission system operator.
• Three 106 kWh/33 kW Li-ion batteries installed in medium- and low-voltage distribution substations, which control peak generation of PV installations and manage peak demand periods, and contribute to more effective management of energy flows and voltages.
• One 620 kWh/250 kW Li-ion battery that supplements the three batteries described above. In addition to the previous functions, this battery allows for operation in ‘islanding’ mode. Ten 4 kWh/4.6 kW Li-ion batteries are also installed in volunteer customer homes to facilitate load shedding.

Saft has developed its Li-ion technology to guarantee performance levels consistent with the project’s requirements, most notably in terms of overall battery life, maximum number of charging cycles, and energy efficiency.

The battery system solutions selected for the Nice Grid project involve a certain number of power modules connected in series and in parallel to obtain the desired battery capacity and voltage. These 24 V and 48 V modules store energy, and ensure the battery system’s overall mechanical integrity and safety. A group of power modules is controlled by a control module, which integrates electronics and software for battery monitoring, management and protection, as well as various power control components.

Energy management

Alstom Grid’s energy management system centralises data and optimises power generation, demand management, and storage across an entire district. This system monitors grid operating conditions (i.e. forecast solar power generation, forecast consumption, and technical constraints) as well as the extent of flexibility – in terms of generation, demand management, and storage – offered by the various industry participants (electricity supplier, distribution network operator, aggregator).

The energy management system then uses this information to operate the grid as efficiently and economically as possible.

Energy management has three main pillars:

• Producing reliable estimates of dispersed solar PV power generation and local consumption.
• Taking advantage of customer flexibility, achieved by offering guidance to improve the energy efficiency of heating, hot water, and air-conditioning systems in residential or commercial buildings (demand control and load shedding).
• Optimal storage of electricity (charging and discharging of Li-ion batteries), tested using various approaches to centralisation.

A key objective of the pilot project is to test the impact of substantial PV power generation on the low-voltage grid and its optimal integration within the local power system. This has involved:

• Selecting neighbourhoods in Carros that offer a high proportion of PV generators (one-third of residential customers have been targeted).
• Assessing the impact of this solar generation on the grid, by monitoring energy flows.
• Optimised management of the municipality’s dispersed resources, by developing and incorporating system intelligence tools for forecasting, monitoring, and possibly even dispatching PV-generated electricity.

Islanded mode operation is key

Islanded mode refers to the operation of a portion of a grid system, including its own generators and loads, when it is temporarily disconnected from the main upstream grid. Energy production is provided solely by PV generators, and possibly by battery discharge. The voltage and frequency must be maintained within regulatory limits, and the continuity of upstream and downstream services must be assured.

The Nice Grid project includes the full-scale testing of islanded mode operation for a limited group of volunteer customers in Carros. This involves the participation of all grid system stakeholders, to enable a better understanding of the technical and economic implications of this technology.

It is essential to arrive at a full assessment of the costs and complexity of islanded mode operation that makes use of locally available – and in particular renewable – energy resources. This represents a major technological challenge, given the possibility of upstream grid failure.

Project architecture

The Nice Grid is deploying a smart solar district of significant size and scope as a pilot project, with approximately 2500 potential residential and business customers involved in the project. Several of these customers are equipped with PV rooftop panels and connected to the same low-voltage grid.

The project makes use of a high proportion of local intermittent energy sources, to demonstrate an optimal approach to electricity management, at the level of a district or town. This involves the large-scale integration of dispersed solar PV power generation systems (target: 2.5 MWp), load-shedding capacities (target: 3.5 MW), and energy storage systems (Saft Li-ion batteries with 1.5 MW total capacity), at different points in the overall system: i.e. distribution network owners and operators, electricity producers, and consumers.

The project includes the design and integration of an energy management system that communicates with the various local dispersed devices and technologies. The aim is to ensure that the primary substation has sufficient flexibility, by controlling the operation of batteries connected to the grid.

In Figure 1, the blue area represents the full scope of the pilot project, with several hundred ‘prosumers’ in Carros providing a total load-shedding and battery discharge capacity of 5 MW, and supplied with four medium-voltage feeder lines.

The orange area is the smart solar district, which consists of up to several dozen customers equipped with solar PV arrays, as a test of the optimal balance achieved at the local level between energy consumption, production, and storage.

The yellow area is the islanded mode test zone, where a group of customers within the industrial zone may be isolated from the main grid for a limited period of time. This group of customers, which corresponds to the population served by a public distribution substation, uses its solar PV generation resources to meet local power requirements when necessary.

Part of European Grid4EU demonstration

The Nice Grid project is one of six smart grid demonstrations within the large-scale Grid4EU project, which aims to test advanced smart grid solutions with wide replicability and scalability potential for the European market. Grid4EU will test the potential of smart grids in areas such as renewable energy integration, electric vehicle development, grid automation, energy storage, energy efficiency, and load reduction.

The Grid4EU project has been designed in response to a call for projects from the European Commission, to lay the groundwork for the development of tomorrow’s electricity grids. This is the largest smart grid project to be funded by the European Union, which is contributing €25 million towards the total budget of €54 million.

Grid4EU brings together a consortium of six European energy distributors: ERDF in France (Nice Grid), Enel Distribuzione in Italy, Iberdrola in Spain, CEZ Distribuce in the Czech Republic, Vattenfall Eldistribution in Sweden, and RWE in Germany. The project also draws on the know-how of other industrial and scientific partners, representing 30 or so partners from some 10 EU countries.

Grid4EU consists of six demonstrators, which will be tested over a period of four years in each of the European countries represented in the consortium. The emphasis will be on fostering complementarity between these projects, and on promoting crosscutting research and sharing results between the different energy distributors involved.

Battery specialist Saft

Saft is a leading designer and manufacturer of advanced technology batteries for industrial applications. The group is the global leader in nickel-based and primary lithium batteries used in industrial and transportation infrastructure and processes, and in civil and military electronics. Saft is also the world leader in batteries for the space and defence industries with its lithium-ion technologies, which are now also being deployed in the energy storage, transportation, and telecom industries.