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The electrical engineer who worked his way up

Greg Tremelling

Greg Tremelling is a Senior Manager of Electrical Engineering at NEC Energy Solutions in Westborough, Massachusetts. Here, he discusses his work with large-scale energy storage systems, the importance of safety in the industry and the steps he and his teams have taken to ensure it, and his hopes for a productive future together with NEC.

Starting in design, ending in management, and building teams to pull it all together

Photo: Greg Tremelling

--First, please tell me a little bit about your background.

I'm from Berlin, Massachusetts. I grew up in that area and I've lived there my whole life. I went to school at Worcester Polytechnic Institute in Worcester, Mass. While I was there I worked on two major projects, one for two months in Switzerland and one at the Goddard Space Flight Center, where we re-designed an optical encoder for NASA.

--Can you fill us in on your work history?

Prior to joining NEC Energy Solutions, I designed un-interruptible power supplies at a American Power Conversion (APC). Since joining the NEC team as an electrical design engineer, I have architected and designed a number of battery management systems including a 200KW hybrid bus energy storage system and NEC's large scale multi megawatt Energy Storage Systems. After working in the design team, I transitioned into a new role to create and manage a Platform Engineering team. The Platform team provided sustaining engineering support for the products that I had just designed. When this team became stable, I had the opportunity to start another team within the company called the Smart Grid Integration team. Smart Grid Integration was responsible for managing the installation of large scale energy storage systems for our customers from the time of purchase order through commissioning the systems in the field. Now I'm back on the new product development side of the business, running the Electrical Design and Test Engineering departments. The significance of all this is that I was able to start in design, and then go downstream and actually support and manage the products that I had designed, and then come back full-circle from the customer projects back to design. This has given me an interesting perspective on how products should be defined and designed and architected to improve the product life cycle—specifically, to make them serviceable, manufacturable, and testable.

--That sounds like a very holistic approach. What are some of the benefits of going through the process in this way?

Ultimately, it comes down to having a bigger-picture view of product design. A higher-level view that is not limited to just the electrical aspect or the product design itself. It's enabled me to place an emphasis on manufacturability, on testability. On what our customers are going to actually do to this product in the field. It helps us think, “How can they break it? How can this product fail?” You get to see a lot of things firsthand. I got to go out in the field and talk to a lot of customers and deal with real issues—that's really where you learn.

Architecting the next generation of battery management

Photo: Greg Tremelling

--Explain what you're currently responsible for.

My teams and I are responsible for designing all of the electronics and electrical systems needed to manage our large scale energy storage products as well as the battery management systems for NEC Energy Solutions' commercial product line. The Test Engineering team also reports up through my organization.

--Please go into more detail about what these teams do.

The test equipment group designs the test equipment that will test the product in production for quality control. At the same time that we're developing the products and the electronics, we also have to develop test infrastructure to support it, so that when we manufacture it, we have a way to test the quality and the functions before shipping. With the Electrical Engineering team, depending on the needs, we jump back and forth between working on various commercial products or the large scale grid energy storage battery management. We have some new designs that we're working on that we're very excited about. Some new technology that will reduce costs and make the products more flexible, higher-performing—essentially, more connected. We're actually architecting the next generation of battery management.

Making the most of renewable technologies

Photo: Greg Tremelling

--What exactly are large scale energy storage systems? How do they work?

Large scale energy storage systems are essentially shock absorbers for the electrical grid. They are able to pull energy from the grid when there is an excess, and push that same energy back onto the grid at a later time when it is needed. By adding the dimension of time into the grid stability equation, many problems can now be solved. The widespread adoption of distributed solar and wind power generation is just one area where grid scale energy storage can provide tremendous value. NEC's energy storage is able to smooth out the rapid power fluctuations introduced by these renewable technologies. Other energy storage applications include frequency regulation and spinning reserve.

--How are they utilized now?

NEC Energy Solutions now has over 110MW of Energy Storage installed worldwide performing a wide variety of applications for our customers. NEC is actually serving more energy storage applications than I have time to talk about during this interview, but I can comment on a few of them. We have multiple energy storage sites that have been integrated with wind power to control the ramp rate of the power generated. We also have Energy Storage sites that provide spinning reserve. This is in addition to several smaller distributed energy storage systems we offer.

--Can you explain some features of these systems?

Normally these systems are watching the frequency, voltage, and current levels at the site where the system is installed. Using these inputs, NEC Energy Solutions' AEROS controller controls the entire site to manage one or more of these parameters to be within a specified range. At one particular site we have 16 “53-ft containers” all working together in unison as a single 32MW power source.

--Please give us a usage example from Japan.

Sure. A great example is solar. Solar energy changes its output very quickly. The base load generation on the grid cannot change its power level quickly, so, there's a gap. And that gap is actually preventing solar applications from turning on. What this means is that there are solar projects that people have built that they can't turn on, because in certain areas of the grid, they're concerned about stability. This is of great interest in the wake of some of the power issues that are unique to Japan.There have consequently been changes in the desire to deploy solar. Overall, solar is really ramping up.

Photo: The battery management system

“The battery management system shown in this picture manages a 100kwh rack of energy storage which operates at 960v DC. It includes a very unique feature called “the equalizer” which we have patented, which allows high voltage racks of different DC voltages to connect to the same main DC power bus automatically, without taking the rest of system offline or manually matching the rack voltages before connecting them into the rest of the system. It allows for superior availability and serviceability of our systems. This battery management system provides control, redundant safety, and full visibility into the battery system.

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