Your questions answered: Microgrids 301: Tying multiple power systems together with intelligent controls

The Sept. 24, 2019, “Microgrids 301: Tying multiple power systems together with intelligent controls” webcast presenters addressed questions not covered during the live event
By Consulting-Specifying Engineer October 8, 2019
Microgrids defined. Courtesy: MTU Onsite Energy

This presentation is designed to educate energy professionals (consulting engineers, owners, distributed energy managers) regarding microgrid and distributed generation projects using intelligent control systems. The presenters discussed consideration factors commonly used to evaluate intelligent automation systems, including monitoring and power resource control capabilities, and impact on system reliability and sustainability. During this webcast, the presenters also highlighted the benefits of digital simulation capabilities, in which real-world applications are modeled and analyzed to determine the most economic deployment of energy producing assets.

Key topics include:

  • Introduction to intelligent automation systems
  • Understanding of common consideration factors including monitoring and power resource control capability, and system impact on reliability and sustainability
  • Benefits of digital simulations to model real-world applications and determine optimal configuration of energy producing assets.

Presenters during the webcast were:

  • Christian Mueller, senior sales engineer, MTU Onsite Energy
  • Tom Drake, regional sales manager for Gas Power Systems MTU Onsite Energy

Presenters Christian Mueller and Tom Drake responded to questions not answered during the live Microgrids 301: Tying multiple power systems together with intelligent controls webcast on Sept. 24, 2019. Brian Ponstein, regional sales engineer, MTU Onsite Energy moderated the Q&A session.

Question: Are there behind the meter smart panels available for buildings that can be used to manager various distributed energy resources (DER)?

Christian Mueller: Yes, that is the microgrid controller we talked about in our presentation.

Q: What are the industry-standard controls? Are there nonproprietary standards for heterogeneous interoperability?

Mueller: The controller and the software running on it is typically proprietary. However, interfaces to nonproprietary controllers on generation assets are provided.

Q: Do different DER/power sources impact the existing utility grid power?

Tom Drake: Yes, each DER can impact a customer/utility and the controller is set up to maximize the various resources from an operational and financial perspective.

Q: How large are these controllers? At what scale does this system become feasible? For a single building? For a campus?

Mueller: They are the size of a typical controls cabinet. Feasibility depends on the financial viability of the project.

Q: For new facilities, to avoid curtailment, what size of microgrid do you recommend: 80% to 90% of building requirement?

Drake: Each microgrid is specific to the facility and curtailment depends on the utility tariffs.

Q: Do you have program that determines ratio of generator, photovoltaic (PV) and battery for given project?

Drake: Yes, we have an in-house program along with commercially viable programs like Homer Pro.

Q: In your greenhouse simulation, what is driving the calendar-month step differences in electrical energy demand?

Drake: The drive is the site’s cooling loads.

Q: What would be the optimum facility size or grid demand that would make the Microgrid Management system a viable financial option.

Drake: Optimum size depends on the electrical and thermal at the facility and the interconnection rules with the local utility.

Q: Won’t microgrids exiting the main grid when generation reserves are critically low just make the situation worse on the main grid?

Drake: In many cases, utilities are offering incentives for the installation of microgrids. These allow utilities to delay expensive transmission and distribution upgrades.

Q: Is the simulation software available for use?

Drake: Yes, there are multiple platforms available for modeling; Homer Pro as an example.

Q: I have heard about solar pushing power to the grid. How is this accomplished and how does your control system handle this to avoid over-voltage in the grid?

Drake: Ideally, if the microgrid is paired with a battery energy storage system, we can store the energy from PV in the battery by charging the system during times of overproduction to avoid curtailment of solar generation.

Q: Can you please touch on the challenges of seamless (unplanned) transition from on-grid to off-grid and back?

Drake: The main challenge of transition from grid parallel to microgrid operation is controlling the load from the grid to the generation assets. Sizing the generation assets, gas or diesel generator, with their ability to accept load steps is the key to seamless transition. Often, using battery systems to smooth the application of the load.

Q: In a normal application which one is the ROI?

Drake: ROI depends on the cost of the utility resources being replaced: the electricity and natural gas and the spark spread between them.

Q: Can modeling reveal the optimal sizes of gensets?

Drake: Yes, ideally, the loads are input into the modeling program to optimize the mix of generation assets.

Q: Which one is the operating life of the bank of batteries?

Drake: Operating life depends on the full cycle, discharge and recharge, of the BESS, normally 3,600 cycles. 

Q: Were you talking about lithium batteries? How much do they cost? What is their life?

Drake: Life cycle of the battery energy storage systems is standard 3,600 full cycles and depends on the application.

Q: What does behind the meter mean, upstream or downstream from the meter?

Drake: Behind the meter, for Rolls Royce/MTU, means customer facing behind the point of utility connection.

Q: Does MTU provides a portion of, or an entire commissioning services?

Drake: Rolls Royce/MTU can offer the specific distributed generation equipment (diesel and gas generators) along with battery energy storage systems with the supervisory controls along with commissioning services for the equipment.

Q: Who do we talk to on seeing if a project possible?

Drake: MTU can offer project services for high level and project analysis.

Consulting-Specifying Engineer