Case Study – Energy optimisation through micro grid design

When the Askersund Municipality redeveloped the site of an old 1960s high school to provide a new cultural centre they were keen to incorporate local energy production, increase the reliability of their electrical supplies and to reduce on-going electricity costs.

They commissioned Vattenfall to develop a comprehensive micro grid which would also provide charging facilities for electric vehicles and utilise smart grids features through the use of smart lighting.

Vattenfall designed an integrated solution, carefully balancing energy production and consumption to minimize the use of grid based power and improve the reliability of energy to the network through the use of dynamic grid controls.

The solar PV system was designed from 380 265Wp panels, providing a 100kWp system split across three roofs.

Seven 7.2kWh lithium iron phosphate batteries were installed to maximize the benefits of the solar PV and reduce energy conversion losses by keeping power in DC.

A 50kW EV charger and two 11kW semi-fast charging points were connected to the micro grid. The energy storage system works with the chargers to reduce power peaks that arise from car charging and to provide an uninterrupted power supply (UPS).

A smart lighting system with 700 control points was incorporated into the grid and all devices were connected to a micro grid control, communication and protection systems as part of the LV grid.

In the entrance foyer of the building, visitors can learn about the micro grid via an energy monitoring system. For example, visitors can study instantaneous energy flows to and from the different power sources and energy demands in the network.

The results of the project include reduced downtime (System Average Interruption Duration Index – SAIDI), improved power quality, and reduced CAPEX for the Municipality. Furthermore, the data collection and analytics of the project have contributed to increased learning and provided valuable insights for future projects.

Goals:

• Enable peak shaving for solar and EV-charging as well as for consumption.
• Deploy a low carbon energy system including solar PV, EV-charging and energy storage.

Results:

• Reduced downtime (System Average Interruption Duration Index – SAIDI)
• Improved power quality
• Reduced CAPEX
• Energy data collection and analytics solutions