Utilities can embrace home solar and avoid costly grid upgrades. Here’s how.

Learn how a Distributed Energy Resource Management System (DERMS) combined with a microgrid controller allowed a utility to coordinate customer DERs without fear of exceeding the system’s constraints.

Onslow solar farm and substation
Onslow solar farm and substation

As on-site renewable energy becomes a more attractive option for homeowners due to the falling costs of solar panels, expanded incentives through the IRA, and rising energy prices, more people are seeking to install solar PV and battery storage. However, plugging these distributed energy resources (DERs) into the local grid requires utilities to consider current network capacity, leading utilities to refuse interconnections for systems that could overload the grid or that require expensive equipment upgrades.

Such connection refusals are often attributed to a lack of capacity related to the wires’ ability to carry a certain volume of electricity. The grid was originally designed for one-way power flow from power plants to homes where the utility could strictly control the amount of power flowing through its wires. When homeowners start to put excess solar power back onto the grid, this becomes a two-way flow, which the grid wasn’t designed to handle. Furthermore, the utilities haven’t traditionally needed to manage power sources other than their own, so their equipment isn’t designed to do so.

A large part of the problem: utilities do not always have visibility into how much home solar is being added to the grid. Utilities may be aware of an individual solar PV’s maximum output capability, but they don’t have integrated systems that provide them with real-time data showing how much power is flowing back onto the network from moment to moment.

This lack of insight is especially challenging during times of intermittent power production such as when clouds are passing overhead, causing wide fluctuations in power production from one minute to the next, from one neighborhood to the next.

To keep the system stable for everyone, utilities play it safe by curtailing the solar that is connected to the grid, ensuring power flow stays well within system thresholds. If grid capacity is exceeded or overloaded, it can lead to outages, blackouts, damaged power line equipment, and more.

What are utilities’ options other than costly and time-consuming grid upgrades?

DERs and grid management software

Increasing customer DERs can make electric grids both more resilient and cleaner by relying less on energy derived from centralized fossil fuel power plants and more on locally produced energy. Grid management software can also help in circumstances where grids are either permanently or temporarily islanded from the main grid. Smaller grids such as these, often referred to as microgrids, are more vulnerable to intermittency fluctuations because they don’t have as much system inertia to buffer the variability.

One non-wires alternative to increasing the amount of DERs on the grid is grid management software. With the ability to monitor and coordinate customer DERs, utilities can confidently maximize the use of their existing infrastructure without fear of exceeding the system’s constraints.

How grid management software works:

  1. Using machine-learning to predict the system load;
  2. Developing a schedule for the DERs to match that load;
  3. Executing the schedule by dispatching different resources to fully produce, curtail, or absorb (in the case of batteries) power to match the load predictions, and;
  4. Monitoring network conditions and responding in real time to deviations in the load or production predictions.

Microgrid management in action

Over the last three years, innovative projects in regions of Australia have demonstrated how grid management software can enable utilities to permit additional residential renewables where previously network constraints had led to moratoriums on adding DERs. Though the examples are drawn from small, isolated grids (microgrids) in Australia, they are relevant to anywhere a utility is struggling to get a handle on a proliferation of DERs.

As mentioned earlier, managing a multitude of DERs on a smaller grid with less inertia is more technically challenging than doing the same on a much larger grid—implying a favorable outcome for scalability in a larger playing field.

Utility snapshot: Horizon Power is Western Australia’s regional energy provider and supplies electricity to over 35,000 residential and 9,000 business customers.

Challenges: Many of its customers rely on power distributed via isolated microgrids located in hot summer climates where sunshine is abundant and air conditioning is a necessity. These conditions have resulted in a high proliferation of home solar installations, which unfortunately led Horizon Power to resort to moratoriums and refusals of solar interconnections to protect the safety and reliability of its networks. The quantity of solar PV was tripping generators offline due to issues like too much solar production feeding back into the grid and an inability to handle the rapid variations that occur when cloud cover impacts generation. Predictably, the moratorium cast a negative light on the utility.

Solution: Aiming to lift the moratoriums, Horizon Power set out to find a solution that didn’t involve expensive and time-consuming infrastructure upgrades. In the town of Onslow, one of 38 microgrids Horizon Power operates, the utility piloted a configuration that included a Distributed Energy Resource Management System (DERMS) combined with a microgrid controller.

Horizon Power leveraged the DERMS for high-level visibility and forecasting for the entire system, including utility and customer-owned assets, and consolidate coordination, visibility, and control of all the systems under a single dashboard.

  • The DERMS’ demand forecasting feature continuously analyzes historical demand and weather data to derive an operating plan for anticipated demand.
  • It recalibrates the operating plan through autonomous optimizations that maximize renewable generation, cost savings, and system efficiency.
  • The network-aware optimization considers voltage and capacity limits, topology, and energy resource characteristics to ensure the system converges to an optimal solution rather than merely the fastest or easiest to initialize.

Working in concert with the DERMS, the microgrid controller executes the DERMS’ operating plan while making real-time adjustments as rapidly as 10 times per second that accurately respond to current conditions on the grid. This controller adds a level of precision control that enabled Horizon Power to debunk a long-held myth in the power industry—that you can’t operate a 100% renewable grid without some sort of spinning generator.

Community powered 100% by solar + storage

In the world’s first known instance of solar-plus-storage supplying 100% of a community’s power, Horizon Power powered Onslow without any fossil fuel or hydropower-based systems and kept the system stable for over an hour. In this successful demonstration, the system inertia was maintained by a battery energy storage system, which acted as a system shock absorber, dispatching or absorbing power in response to solar PV production fluctuations.

The project served as a successful demonstration of how grid-control technology can enable communities to embrace increasing amounts of renewable energy, without the risk of grid stability issues.

Today, Horizon Power has a 1 MW solar farm that adds to the 2.1 MW of customer solar PV installed across 260 sites, and there’s opportunity for an additional 200 kW of customer-owned DER assets to be interconnected.

This major success in Onslow was followed by an announcement from the Government of Western Australia that solar PV installations have been expanded in the town of Carnarvon. The DERMS deployments will eliminate solar PV connection refusals in more than 34 microgrids in Western Australia.

Feasibility in U.S.

Efforts across Australia can be mirrored in the U.S. for similar results and hold the potential to be adopted globally and applied to any grid. Small, isolated grids have amplified issues taking on solar, and if a utility for remote regions in Australia can tackle these challenges, others can do the same.

In the U.S., island states and territories such as Hawaii and Guam are turning to renewables to lessen their dependence on imported fuels, and using grid management software to allow more solar PV will be key to this energy mix. Rural co-ops and municipal utilities are also increasingly looking to renewable microgrids to meet their energy needs.

As customer sited installations like home solar PV continue to grow in popularity, the issue of grid capacity and stability will become even more critical across the U.S. The reality is that there’s only so much the grid can be stretched without lengthy and costly infrastructure upgrades. By adopting advanced grid-control technologies, utilities can best prepare the grid for more customer DERs – without compromising power reliability or stability.

 By Andy Miller, Head of Commercial Development, PXiSE Energy Solutions

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