Your questions answered: Microgrid design for efficiency and resiliency

The webcast on Sept. 30, 2020, left unanswered questions. Read more about microgrid design here

By Tom Drake October 9, 2020

Building owners frequently want engineers to integrate the utility’s smart grid into their facilities to reduce electricity use and increase energy efficiency. Microgrids can further lower costs and improve building resiliency. Learn more in this “Microgrid design for efficiency and resiliency” webcast from Sept. 30, 2020.


  • Juan Matson, senior sales manager, engineering gas power systems, MTU/Rolls Royce Power Systems
  • Tom Drake, senior sales manager for gas power systems, MTU/Rolls Royce Power Systems


What software is best for modelling microgrids?

Tom Drake: We use Homer Grid and Homer Pro as our initial microgrid modeling tool.

Will Rolls Royce focus more on sustainable energy rather than nonsustainable energy resources such has gas and diesel?

Tom Drake: Our focus has been modified to be a solutions provider rather than only a supplier of components.

Why there is need of artificial intelligence in the controllers?

Tom Drake: AI is used to learn the performance of the plant so we can better performance changes.

The utility companies typically have very strict requirements in terms of protection relays and controllability for a microgrid system to parallel with utility or send energy back into the grid. Please tell us about what your system has incorporated in such terms or to your experience has to be added to the power distribution system to allow connecting the microgrid output to the utility grid.

Tom Drake: We always coordinate with the local utility to provide the required relays and relay settings to comply with local codes and standards.

What is the smallest demand that would warrant a microgrid application?

Tom Drake: That which provides the largest value based on customer requirements — customer desire and demand are only limitations.

To have renewables comparable to the fossil fuel-based systems, don’t you need to include energy storage in the costs for the renewables? How do they really compare?

Tom Drake and Juan Matson: If the customer load matches the installed photovoltaic production BESS is not required. Only need BESS if time shifting of the energy use is required for financial or reliability reasons. This also depends on the availability, dispatchability and reliability projected for the MG.

How realistic are the $3/MMBtu price going forward with most of the generation coming online being natural gas fired? Won’t most or all of that increasing gas supply be taken up?

Tom Drake: The forward market reflects a low cost per Btu of gas into the future based on available reserves.

What is the development status of natural gas fuel cells and where do they fit into a microgrid system?

Tom Drake: At Rolls Royce MTU, we are continuing to investigate alternative distributed energy resources and fuel cells both natural gas and hydrogen will be incorporated into our portfolio. The only limitations are the financial modeling and how they will model into a system to provide the lowest cost of power.

How do you account for time and cost uncertainty of utility interconnect studies and grid upgrades?

Tom Drake: For behind the meter projects these go much more quickly as we normally only have to prove the protective relay design. With utility facing projects, involving the utility is always the first step to establish the price and time requirements.

How much physical space did the 18.7 megawatts of PV take up on the first case study? Was it located on building roof or on ground?

Tom Drake: A general rule of thumb could be something in between 11 to 15 acres x megawatts.

Can you talk more about the capabilities of your microgrid controller. In particular ability to eliminate any power export. How well does it work with Solar PV and battery storage? Does it look at the most cost-efficient time to charge and discharge the battery.

Tom Drake: The microgrid controller can be tied to any distributed energy resource. Good communication in the project design phase will ensure that we have all of the necessary monitoring included into the design.

Does your case study scale down to smaller system? How small can you go and make economic sense?

Juan Matson: Although economic sense is something to consider, there is also the consideration as to what are the actual market needs. This varies based on demographics, etc.

In your first case study. Did you provide the software to the client to manage the actual usage? Is it installed? How close to your model were you?

Tom Drake: The software would be part of the microgrid controller.

In case study No. 1, the customer is connected to the grid as well?

Tom Drake: Yes — the plant will operate in grid parallel.

Do you provide performance contracting funding for the capital costs and service agreements to manage the plant along with negotiation power for utility rates?

Tom Drake: Ideally, we build a team to approach a performance contract with MTU/Rolls Royce providing service and guarantees on our supplied equipment. Financing for projects is reviewed on a case by case basis.

What are technical differences and cost premium if there is a need for the inverter(s) to provide VARs and/or frequency support in grid connect mode?

Juan Matson: This varies from project to project and is initially defined during the BESS configuration.

I know you have control software from generator sets, but do you have management software to combine and then optimize for solar, wind, BESS with generators and grid?

Tom Drake: Yes — included in the Microgrid controller

How does the microgrid controller work to controls other systems?

Tom Drake: Yes — we can connect with multiple types of inverters, generator controllers, metering devices, etc.

I wanted to know if you have a representation in Israel?

Tom Drake: will assist you in finding our local distributor.

Regarding your Mexico projects for on-site power, what is your opinion of present new federal governmental regulations making more difficult to get generation permits for places like Carrol Pig Farm?

Juan Matson: It’s another milestone to deal with that may affect in pricing and deployment for future projects. We’ve seen this happening several times.

Are your gas generator sets produced in U.S. like your diesel ones? If not, where?

Tom Drake: Gas units are built in Augsburg, Germany.

What batteries do you use and how do you see battery technology moving forward?

Tom Drake: Lithium ion; we are studying available chemistries for price and performance.

How fast can batteries discharge to keep the frequency stable when a block load is applied to the system? Are reciprocating gensets still needed to help respond to block loads?

Tom Drake: reaction time is in milliseconds, so controlling load steps for generators is seen as almost instantaneous.

What stability issues are important to look at when considering microgrids?

For natural gas generators, is there a requirement for on-site storage or is a connection to a natural gas distribution line considered adequate?

Tom Drake: Line is adequate.

Does MTU supply complete microgrids in including the battery, solar and wind systems? Or do you work with partners for those components?

Tom Drake and Juan Matson: We don’t supply PV or wind would partner with other vendors. Based on the project, we can be the single point of contact.

For a full island mode, is there any level of redundancy recommended for generation resources?

Tom Drake: Yes, the level of redundancy would have to be equal to the critical nature of the business.

What is about possibility to operate at extremely low temperatures (-40° to -55°C)? As far as I know our BESS was designed for the temperature range -20° to 45°C. When we are able to see MTU energy pack with extended temperature range?

Tom Drake: For cold installations we’d recommend customer third-party enclosures; we’ve seen our Canadian partners use them, to manage the ambient conditions

Author Bio: Tom Drake, regional sales manager for Gas Power Systems, MTU Onsite Energy