Stone Edge Farm Microgrid Innovates with Controls and Hydrogen

Controls platforms for microgrids—the key enabling technology for building a more resilient energy system—continue evolving. Emphasis is shifting from hardware devices and on-premises gateways to software customization performed via data-lake aggregation and advanced analytics in the cloud.

If a single microgrid has had more impact on the industry in terms of both controls and advanced thinking about energy storage, it would be the Stone Edge Farm microgrid on the outskirts of Sonoma, California, which has been operating independently in island mode since December 2019.

Market Evolves Toward Distributed and Modular Controls

The most transformative aspect of this microgrid is the birth of a new approach to microgrid controls, necessitated by the microgrid’s complexity: eight kinds of batteries and multiple types of inverters with 20 different integrated distributed energy resources (DER), which total 785 kW of capacity. As this microgrid has evolved since it was initiated in 2013, it became clear that a new approach was needed as existing controls products made integration of so many diverse DER difficult and time consuming. In fact, a new company came into being as a result of this need: Heila Technologies. Stone Edge Farm facilitated the creation of an end-to-end modular platform—Heila EDGE—that brings intelligence to the grid edge, allowing for the organic and agnostic integration of any DER. Using distributed control and optimization, each DER becomes an independent agent capable of determining at split-second intervals the most beneficial operating point relative to system-level objectives. In short, a bottoms-up instead of top-down approach. The history of how Stone Edge Farm helped create this new controls approach is the subject of a new white paper. 

The world is moving away from a hub and spoke model that mimicked top-down, bigger-is-better thinking. This is not where the electricity industry began. Thomas Edison started with microgrids, but existing technologies of his time rendered a highly competitive and decentralized energy industry inefficient.

Microgrid controls range from top-down, bottoms-up, and (increasingly) hybrid controls approaches. The beauty of the distributed and decentralized approaches is that they can be deployed for any framework preferred or required for a microgrid or other aggregation, including virtual power plants.

Hydrogen Is Also Key for Future Microgrids

Along with the birth of a new controls paradigm, another revelation emerged from the Stone Edge Farm experiment: the business case for hydrogen.

A major challenge for the Stone Edge Farm microgrid was the overproduction of renewable energy during summer, when the days were long and solar energy was plentiful. (Conversely, the system contained less renewable energy supply during winter when days were short.) After investigating the potential sale of excess renewable energy to the surrounding distribution utility or the wholesale market, the regulatory barriers and costs associated with telemetry requirements rendered these options uneconomic.

Stone Edge Farm decided to add hydrogen production technologies that could harvest excess renewable energy and convert it into a fuel storage medium, further diversifying the microgrid. In 2017, the farm installed electrolyzers at the microgrid. This technology can create hydrogen at small scale and has been deployed in a few remote island microgrids in Latin America and Asia Pacific.

Distributed Bidirectional Hydrogen System at Stone Edge Farm

 
(Source: Heila Technologies)

At Stone Edge Farm, this hydrogen is used for vehicles onsite, but it can also be used for longer-term seasonal energy storage (see figure above). Energy use and transportation are likely to become increasingly intertwined. Microgrids that incorporate hydrogen can potentially support both, a critical interaction required to meet the net-zero energy future. When combined with state-of-the-art controls, microgrids can run completely on renewable energy.