Microgrid applications -  Driving low carbon initiatives (Part 6)

Microgrids have a number of applications and I have categorised and discussed these in this blog series as follows:

All the microgrid applications discussed in earlier blogs use RES to reduce carbon impacts and in many cases are designed to displace or replace traditional diesel fuelled generation as the anchor microgrid energy sources. The microgrid applications discussed in this blog have a primary focus to attract and encourage the use of low carbon DER, primarily in high density population areas e.g. town and city centres, by local authorities and city councils who have committed to carbon reduction or climate emergency targets.

This microgrid application is illustrated through two example projects where Smarter Grid Solutions (SGS) is utilizing our extensive experience in DER management system design and applications.

  • In 2018 the town of Lac-Mégantic in Canada and Hydro-Québec the local utility distribution network operator (DNO), set out to deliver a microgrid that brings together leading-edge energy technologies to position Lac-Mégantic as a leader in the clean energy transition. Linked to Hydro-Québec's main grid, the microgrid connects some 30 buildings and is equipped with 2,200 solar panels providing almost 800kW of power, 700kW of storage batteries, fast-charge stations for electric vehicles and smart building systems in about 20 apartments and commercial buildings. In the case of an outage, the batteries can supply downtown Lac-Mégantic with electricity for several hours. The microgrid can also store the surplus energy it generates and feed it back into Hydro-Québec's main grid. In island mode conditions the smart building systems provide information that allow customers to amend energy usage and extend the run time of the BESS supported island network. SGS were responsible for delivering the microgrid control solution which is being further developed by SGS to include demand and PV output forecasting. Lac-Mégantic and Hydro-Québec are using the microgrid as a demonstration to encourage the clean energy transition in other Canadian towns and cities.

  • As noted, and summarised in blog 3, SGS is part of a consortium developing a UK smart city initiative that will cut customer energy bills and provide green heat, electricity and transport for residents helping the city council hit their net zero targets. This smart city demonstration project centres on the use of a private heat network (PHN) and a private wire network (PWN). The associated microgrid control system to be provided by SGS will manage centralised and decentralised battery energy storage systems (BESS) and solar PV, and various electric vehicle (EV) charging infrastructure for bus services, council vehicles, taxi services and public carparks.   The microgrid control system will also provide forecast data to the operators of a combined heat and power (CHP) energy from waste plant that will be a major source of electricity to the PWN as well as the source of heat for the heat network. This data will influence the balance between heat and electricity production when required at the energy from waste plant. The microgrid controller will ingest wholesale electricity market price, PWN demand and generation forecast data and use the BESS to minimise the use of energy from the wholesale market when the PWN net demand and wholesale prices are forecast to be high. The microgrid controller will also be used to minimise utility grid use of system (UoS) charges in order to offer customers on the PWN reduced energy tariffs. The overall concept being to attract further RES and demand customers onto the PWN. This smart city initiative will demonstrate the potential for towns and cities across the UK to meet their carbon reduction targets employing similar microgrid solutions to offer residents and businesses clean electricity, heat and transport with reduced energy charges.

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Both of these projects aim to demonstrate microgrid based technology solutions that will assist in the clean energy transition of town and city local authority areas. These projects illustrate a number of emerging microgrid themes :

  • The need for wholesale energy price forecasts for energy arbitrage. SGS can included the ingestion of wholesale and other electricity market price forecasts into our fleet DERMS and microgrid solutions.
  • The need to forecast demand, generation and BESS run time. BESS run time forecasts in island mode can be used to control or influence flexible demand to extend BESS supported island mode run times where required.
  • There is a clear need for monitoring the real time carbon intensity of all energy sources supplying the microgrid including what flows through the utility grid connection and how that aligns with onsite energy demand and production. Firstly using data analytics on historical carbon intensity data will allow local authorities and councils to track historical carbon reduction delivered by microgrid applications. This provides a means of monitoring microgrid carbon reduction success over time.

Secondly real time carbon intensity data can be used to enable real time control decisions to minimise carbon intensity in the microgrid. This may also require data analytics to support forecasting of microgrid carbon intensity. In the UK the ESO publishes half hourly regional carbon intensity data which broadly aligns with peak system demand, in turn correlated with wholesale electricity market price. This provides an estimate of the microgrid’s utility grid supply carbon intensity on a half hour by half hour average basis. If you had a microgrid supported by carbon free DER but taking top up supplies from the utility grid you may not want to charge the BESS when grid supply carbon intensity is higher even if wholesale prices are lower. While UK data shows broad alignment between carbon intensity daily peaks and wholesale price daily peaks, the alignment is not exact and at other times of day alignment is poorer. Hence wholesale prices cannot be used as an accurate proxy for utility supply carbon intensity. Hence carbon intensity can be used as an additional influencing factor for the timing of BESS based energy arbitrage with the wholesale market where local authorities wish to consider carbon intensity as well as purely economic factors.

Another interesting example of why carbon intensity is important is microgrid based fleet depot EV charging such as electric refuse trucks and electric buses. Real time data on microgrid carbon intensity can be used to influence real time EV charging in addition to electricity price data i.e. if you are a local authority investing in a fleet of electric refuse collection vehicles you don’t want the fleet to come back to the depot and start charging these at 5:30pm when the microgrid carbon intensity is peaking due to top ups of high carbon intensity power from the utility grid. The micro grid controller can use grid carbon intensity data to influence fleet EV charging from the microgrid.

SGS’s Strata Resilience product is a software-based microgrid manager that delivers grid connected, island and black start operations while optimizing the value of microgrid assets for customers with grid and market integration. Strata Resilience delivers the core capabilities of DER microgrid management.

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