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Q&A with Julieta Giraldez-Miner: Providing Innovative Integration Options to Utilities and Power Systems

Dec. 9, 2019

Julieta Giraldez-Miner is a senior research engineer in the National Renewable Energy Laboratory's (NREL's) Power Systems Engineering Center (PSEC). Giraldez-Miner joined NREL eight years ago and currently leads microgrid, smart grid, and grid integration projects. Her work includes assisting utilities with managing distributed energy resources (DERs).

We sat down with Giraldez-Miner to find out more about her field of study and what opportunities and challenges she is excited to tackle. The following has been edited for length.

Head shot of NREL Senior Research Engineer Julieta Giraldez-Miner
NREL Senior Research Engineer Julieta Giraldez-Miner leads projects on microgrids, smart grids, and grid integration. Photo by Dennis Schroeder, NREL

Talk a little bit about your background.

I grew up in Spain and completed my bachelor's degree in mining engineering, which in Spain covers electrical engineering. There were specialties you could choose in your last year, and I chose generation, transmission, and distribution of electricity. It was a life-changing experience to be introduced to the concept of the power grid, and since then I have focused on energy and the infrastructure that delivers power to homes.

How did you end up NREL?

I came to the United States 10 years ago because of a fellowship to finish my senior design project at the Colorado School of Mines. I was supposed to be here for only six months, but I never ended up leaving! I was lucky that my adviser was Katie Johnson, who did her postdoctoral work at NREL. She connected me to Paul Fleming, who at the time was a postdoctoral researcher and is now a senior researcher at the Flatirons Campus, and I ended up doing my fellowship there. After my fellowship, I decided to stay and apply to graduate school at Mines, and my dream was to work at NREL. I followed all the big grid integration studies happening here at the time. I took a class with Ben Kroposki, the director of PSEC, and he mentioned there was an opening at NREL, so I didn't waste any time in applying.

Tell me about the focus of your work at NREL.

I initially worked in what was called the Market Transformation Center in the Grid and Dispatchable Power group. My focus was on electrical engineering technical assistance, and my main projects were in microgrid design, which is how I got into the world of microgrids. I moved over to PSEC about three years after I was hired. I wanted to focus more on grid integration studies with high penetrations of DERs. In general, I focus on the distribution system and the integration of microgrids and DERs onto the grid.

In PSEC, I started contributing to and leading a lot of work with utility companies to really help them understand how to integrate and manage the high penetrations of DERs. I also look at how utilities can start leveraging some of these customer-sided resources in their operations and planning—understanding not only how to integrate DERs but also how DERs can contribute to solving integration issues. Our work with the Hawaiian Electric Company is an example.

What projects are you looking forward to?

I think now we have shown we can use customer-sited resources for voltage control. The next step is to figure out how to do it better. I am excited to continue partnering with utilities such as the Hawaiian Electric Company and the Sacramento Municipal Utility District to develop tools they can use to look at other options for integrating photovoltaic (PV) into their system other than what we call "wires infrastructure." So, instead of spending money on building the wires infrastructure, we explore if there are more innovative ways of dealing with grid integration issues through what are called "nonwires alternatives."

What are nonwires alternatives exactly?

Imagine the distribution feeder that arrives in your neighborhood. If the transformer is overloaded, the traditional option is to replace the transformer with a bigger one. With a nonwire alternative, rather than spending money on this very expensive infrastructure project, the utility can instead incentivize adding PV and storage to this location so peak load is reduced and the utility can avoid having to upgrade the transformer. It's basically looking at non-infrastructure ways to solve infrastructure issues that might also contribute to the decarbonization of the energy system.

It is an area that is growing and needs a lot of exploration. It is easy to run a model that looks at a new transformer, but it is a lot more complicated to run a model looking at hundreds of customer-sited, new PV and/or storage systems, and we want to help utilities think about these types of questions.

Looking forward, what are the biggest challenges you anticipate when it comes to grid integration?

A challenge I am personally interested in is where technical meets regulatory. When going to conferences, you get the sense that the technology is there, but the regulatory framework is not quite ready to integrate the technology. As scientists and engineers, we must be very conscious that our work considers a feasible regulatory framework. I think energy regulation is something that used to be a lot simpler, but now we must help regulators evaluate and understand more complex energy models, business models, and technologies.

As a scientist and NREL team member, how do you try to challenge yourself?

Scientifically, it's about discovering the right balance of getting a job done while always looking to the future and exploring new ideas. You need to focus on your deliverables while continuing to learn and find out what the next problem to solve is.

Professionally, it is about asking myself where I am going to thrive, but also where I will contribute the most to NREL's mission. Right now, I focus on the technical side, but I am also interested in program management and business development. NREL is a unique place where you can have many different jobs within your career. Although right now I focus on my projects and completing my Ph.D., I look forward to discovering the best way to support others and our growing team.

What are your interests outside of NREL?

Outside of work, I love to hike, do yoga, and sing when I can, sometimes with my dad or with friends. I also spend time with my son and travel internationally to places such as South America or back to Spain.

Read more about Giraldez-Miner and other women in energy by visiting the Women in Energy website.

To learn more about the NREL Power Systems Engineering Center's work in grid modernization, visit the webpage on