For seventy years, Albuquerque-based Sandia National Laboratories has been developing electrical microgrids that increase community resilience and ensure energy security. The Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS), designed to support military bases abroad, and independent power systems for hospitals and regions where electrical grids are at risk of being compromised by natural disasters are some of the applications.
In the coming years, NASA will be sending astronauts back to the Moon for the first time since the Apollo Era and establishing a sustained program of lunar exploration. Future endeavors like mining, fuel processing, and other activities on the Moon could be supported by this technology.
The creation of lunar infrastructure is one of the main objectives of the Artemis Program. NASA will establish the lunar gateway and the Artemis base camp before the decade is over to ensure that rotating crews can explore and conduct science experiments on the surface. This concept will serve as a technology demonstration that will allow for short stays with the goal of staying up to two months.
The Base Camp concept consists of a habitation unit capable of accommodating up to four astronauts and a mining and processing facility that will use local resources to fashion rocket fuel, water, oxygen gas, and building materials. This will extend the duration and range of surface exploration. The facility will be far from the base camp to avoid disrupting other science and technology activities.
The electrical grids for both units will be connected during emergencies. While NASA is designing the electrical system controller for the habitation unit, which will be very similar to the International Space Station's direct-current (DC) system, Sandia's engineers are developing the system that will connect the two microgrids. Jack Flicker is an electrical engineer at Sandia.
“There are some very important differences between something like an ISS-type microgrid to something that has the extent of a moon base. One of those differences is the geographic size, which can be problematic, especially when running at low DC voltages.
“Another is that when you start to extend these systems, there will be a lot more power electronics as well as a lot more distributed energy resources that will exist throughout the base. Sandia has been looking at microgrids with a lot of distributed energy resources for quite a long time.”
Microgrids are part of a larger field of technology that includes distributed energy resources and power electronics. The electrical system controller for the mining and processing center has been designed by Lee and Dave.
The controller needs to maintain an even voltage over a long period of time. Dave said that this controller is similar to a vehicle's cruise control system in that it maintains an even level of voltage on the grid.
“Our goal is to come up with a lunar energy power management system that can efficiently maintain a level system on all those timescales. We’ve got a specialized Secure Scalable Microgrid [SSM] facility and control-system-design methodology that analyzes this. The facility also has specialized energy storage emulators that can help us determine the specifications for how much energy storage the base needs and their requirements.”
The SSM testbed is a scaled and simplified version of the DC lunar microgrid. The testbed consists of three DC microgrids with custom-built electronics that can mimic different power-production systems and devices. The microgrids can be configured to test different scenarios.
Experiments with slightly-adjusted control software can be conducted on this platform. The team will use the SSM to fine-tune their control system and study questions about power system controllers, including the interactions between distributed energy resources, energy storage, and power electronics. Said Wilson.
“The goal here is top-down engineering: We’re trying to determine the control design first, come up with the specifications for the energy storage, and then NASA could use those specifications to get the flight-ready components that meet those specs,” Dave said. “A lot of the time people will do the reverse; they’ll bring you a battery and say, ‘make it work,’ which may degrade the microgrid performance.”
The second focus is to develop a system that will connect the mining facility and habitation module to ensure resilience in emergencies. One way to make this happen is to develop a system that can be changed with ease. There is enough power if multiple parts fail. Said Jack.
“Usually, we have some combination of those two, where it’s oversized to some extent, but you are also able to flexibly route power how you need to within a microgrid or between independent, yet cooperative microgrids like we’re exploring for the moon. In a contingency event such as an energy storage system failing during an eclipse, we want to be able to port the power at the mining facility over to the base camp to keep astronauts safe.”
The efficiency and stability of both will be affected by the distance between the microgrids. The team is trying to figure out if NASA should stick with a DC system or develop something that uses alternating current for the mining unit, then switch to DC once it reaches the habitation unit. Two research facilities are being used by the Sandia team to explore these questions and investigate contingency scenarios.
The Distributed Energy Technologies Laboratory (DETL) is a multi-purpose research facility designed to integrate new energy technologies with existing electrical infrastructure. The lab has the tools to conduct hardware-in-the-loop experiments, where hardware is subjected to various scenarios, including catastrophic blackouts and weather conditions. The experiments are a crucial step between lab simulation and actual field tests.
“With this DC power-hardware-in-the-loop setup that we’re building in the lab, we can test power converters, the impedance of electrical lines between lunar facilities, we could also test actual energy generation and storage devices. Basically, we can use it to study a variety of situations so we can design a system that is self-sustaining and can continue operating even if a solar panel array goes down.”
Kirtland Air Force Base will be used to see how their power system operates and distributes power in low-energy contingency scenarios. In addition, the teams will be working closely together and using tools from NASA and the SSM Testbed in their connection simulations, and eventually plan to test Dave's controller in these simulations as well. This research will have applications on Earth as well.
Even though this work is for a microgrid on the Moon, the research is relevant to creating resilience for communities on Earth. I hope that some of the lessons that come out of this project are lessons I can use back home.
This project is funded by the DOE's Office of Electricity as part of a DOE-NASA partnership to develop the necessary systems for future lunar missions.
Further reading: Sandia Lab News.
All Rights Reserved © 2024
