Taking solar energy storage ‘behind the meter’

Ignacio Quiles, Managing Director of Saft’s operation in Spain, outlines how a manufacturing facility in Northern Spain has deployed a lithium-ion (Li-ion) energy storage system (ESS) ‘behind the meter’ to optimize the utilization of its existing solar photovoltaic (PV) plant. Thanks to a 20 percent reduction in peak power demand and increased self-consumption the site’s energy bills are now reduced by up to eight percent.

EXKAL, located in Navarra, Northern Spain, is the country’s leading manufacturer of refrigeration systems. The company is a key supplier to the refrigeration and retail sectors in both Europe and worldwide with a wide range of sustainable and innovative remote and plug-in cabinets.

EXKAL’s manufacturing facility already had an extensive solar PV plant when, in 2016, the company decided to participate in the five-year European STORY project that aims to demonstrate new energy storage technologies and their benefits in distribution systems. The project involves 18 partner institutions in eight different European countries. The target is to analyse and enhance the use of distributed power generation, so that the dependence on the distribution network can be reduced.

One of the main project partners is CENER (Spanish National Renewable Energy Center), with EXKAL’s facility acting as Spain’s demonstration site for energy storage technology. Green Renovables provided the technical direction for the project.

Solar PV plant

The EXKAL solar installation comprises 23 strings of 20 LW245 PV modules, each rated at 245 watts, providing a peak output of 112.70 kW. The modules are fixed to the factory roof with galvanized structures at 25 degrees tilt on a south-facing azimuth. The modules feed into a 100 kW inverter controlled by an MS Manager that prevents the discharge of energy to the distribution grid that supplies the site.

The factory consumes 428,000 kWh a year, with a peak load of 270 kW. The solar plant enables EXKAL to save around 158,000 kWh a year – equivalent to the energy consumed by 72 typical Spanish households – as well as saving CO2 emissions of over 100 tonnes a year.

The addition of the Saft Li-ion systems, together with an energy management system developed by CENER, has enabled the PV system to be adapted into a storage facility. The aim is to demonstrate two main capabilities: reducing the peak power element of EXKAL’s utility bill by combining energy storage with PV integration; reducing the electricity supply factor of the bill by self-consumption of energy drawn from the batteries at the most expensive time of the day.

Intensium® Mini lithium-ion (Li-ion) systems provide energy storage

Two Saft Intensium® Mini E systems have been installed to provide the EXKAL site with flexible energy storage to meet local grid code requirements, with a capacity of 50 kW power and 200 kWh energy.

The Intensium® Mini provides compact, robust outdoor energy storage in a wide range of energy and power combinations suitable for renewable integration, industrial and commercial installations, utilities, and microgrid applications. Dedicated to medium-size energy storage projects ranging from 100 kW to 1 MW, it is used for peak power reduction, demand response, voltage control, capacity support, frequency regulation and spinning reserves, or a combination of these. 

The Intensium® Mini is a fully integrated storage system manufactured in Saft’s specialized Li-ion factory in Nersac, South West of France. Made up of 56 Synerion® modules, it provides high operational reliability over thousands of cycles with excellent energy efficiency. Its modular design accommodates a wide range of energy capacities and different power to energy ratios suitable for cycle durations from minutes to several hours. It is suitable for applications ranging from 80 to 480 kWh of energy capacity and from 240 to 1720 kW of power.

In the EXKAL application the maximum depth of discharge (DOD) is around 80 percent and the Intensium Mini is designed to support a minimum of 5,000 charge/discharge cycles at this level, which means that it will easily outlast the five-year life of the project. In fact, the projected life is seven to eight years.

Energy storage system operation

Currently, the ESS batteries are charged by the energy generated by the PV facility. However, the power electronic equipment - an MM60 Microgrid Manager rated at 60 kVA / 54 kW, offers the future flexibility for the batteries to also be charged from the site’s electrical grid.

In this particular project, the decision to either charge or consume (discharge) energy from the batteries is made by an external control system designed to regulate operation according to a range of parameters such as DOD, current cost of energy (ie peak or non-peak) and level of consumption. The MM controls the flow of energy to ensure the data monitored is always maintained within the operation limits required for safe, efficient operation of the Li-ion batteries. 

By controlling the active and reactive power, the MM60 Microgrid Manager enables EXKAL’s ESS to offer the following functions:

• Storage of surplus solar energy
• Reduction in peak power loads (peak shaving)
• Reducing energy consumption from the grid at peak hours
• Compensation of reactive power (power factor correction)
• Balanced consumption

The Microgrid Manager can be operated and monitored remotely via Ethernet bus communications. A PC embedded internally, allows the exchange of information between the internal CAN bus and the external Modbus TCP / IP (Ethernet). Thus, the Microgrid Manager acts as a server Modbus TCP /IP.

The results – a significant saving in energy bills

Originally, the ESS was targeted at a peak shaving approach according to a pre-calculated threshold in order to reduce the demand charge levied by EXKAL’s energy supplier. Subsequently, the consumption of the factory was decreased due to restructuring. Therefore, the threshold was lowered, and the strategy refocused on reducing the energy charge.

EXKAL’s energy storage system came on line in April 2017. The initial results are promising. The ESS is contributing to a 20 percent reduction in peak power during the most expensive (P1) period of the day. It is also helping to reduce overall energy consumption by 20 percent during the same peak period by self-consumption of excess PV energy. Considering that there is a ratio of approximately 2:1 between energy costs and demand charge costs then the overall saving in the site energy bill is around eight percent.

The verdict – behind the meter storage will change the future of industry

Clemente López Gilardi, the Green Renovables energy consultant and installer responsible for the EXKAL Project said:

"This application is a great opportunity to show that energy storage in industrial behind the meter applications is a reality that has already arrived, and will change our future".