Mini-Microgrid Technology Promises To Bolster Grid Resilience

A new technological innovation designed for residential energy consumption may prove to be a means by which homeowners can ensure that the lights stay on–even if the grid shuts down.

Sponsored by
Mouser Electronics.

Power Factor is a measure of how efficiently the home draws energy from the grid.

The federal government has increasingly been looking at ways to make the grid more resilient to natural disasters and potential terrorist threats.

The “Energy Switch,” as Austin, Texas-based research and development organization Pecan Street has dubbed the device,  is a multi-source microgrid that gives users the option of drawing power from a wide variety of sources including, photovoltaic cells, generators, natural gas or a combination of them all.

The technology could potentially lessen the damage of storms such as Hurricane Harvey which, according to the US Energy Information Administration, resulted in the forced outage of 10,000MW in generating capacity on the Electricity Reliability Council of Texas’ (ERCOT) grid.

Bert Haskell

Bert Haskell

Pecan Street’s CTO Bert Haskell told Icons of Infrastructure that the “set-and-forget system” will maximize self consumption and minimize grid impacts due to intermittent solar generation. He added that there are currently four prototypes, two of which are in Pecan Street’s lab. The others are housed with the company’s partner Concurrent Design, which is also located in Austin.

“We are looking forward to the future grid architecture which we see as being very highly distributed,” Haskell said. “One problem that manifested early was how to make it easier for someone in a remote area to buy what they need to go off grid.”

He noted that the company realized that combining the requirements from the consumer and utility perspective could appeal to homeowners who want to store their solar energy for later use, as well as utilities that want to drop residential loads during demand response events.

Energy Switch One Line Diagram (Source: Pecan Street)

How it works

The energy switch enables users to manage their electric consumption from a single point, instead of having someone check a battery, solar panels or a generator. To download the Energy Switch One Line Diagram (pdf), click here.

The device is powered by built-in lithium Ion batteries. Notably, the device can also be powered by external sources such as a solar array, a backup generator or the grid itself, so that it can function continuously.

The current iteration has five different modes, Haskell said. The first allows the device to charge its batteries with available grid power. The second mode enables the energy switch to sell energy from a battery or photovoltaic array  to the grid in addition to charging the battery.

The third and the fourth are “off-grid” modes that can be used if there is a grid outage or demand response from the local utility, according to Pecan Street. The device automatically switches to the third mode if there is a power outage, and the fourth is enabled when a secondary power source such as a gas or diesel-powered generator is brought online.

Haskell said that the device also has a “maintenance” mode that enables a residence to operate off of energy from the grid. Additionally, all of the modes except for the fifth have a power factor correction function, which is necessary to make drawing energy from the grid more efficient.

“If the phase and the current of the voltage are not aligned, the grid has to provide more energy less efficiently,” he said. “If the grid operator fails to manage those parameters, the equipment in the home may be wrecked.”

Haskell said that, if the grid parameters changed for any reason, the power factor and the quality wouldn’t matter for the homeowner because both would be balanced.

Notably, Pecan Street uses transducers to measure voltage, current flow and monitor the amount of energy within a system. Haskell noted that the company takes roughly 400,000 measurements every minute, in part to prevent energy spikes.

The road ahead

Pecan Street does not currently have a UL certified product to sell, Haskell said. He added that the energy switch can serve as a reference design for companies looking to develop and commercialize their own microgrid products.

“Our system can emulate product features to test the value proposition and the design.”

The company has also been working to add an electric vehicle (EV) charge controlling element to the system. Haskell said that the full benefit of hybrid vehicles as a means to generate electricity has yet to be fully explored.

“When someone gets a [Chevrolet] Volt, they almost never buy gas: it’s just there as a backup,” Haskell said. “The benefit not fully recognized is that the vehicle is a backup generator for the house. The gasoline makes automobiles such as the Volt a backup gasoline generator.”

Haskell noted that the element would give riders control of charging and discharging energy back to the grid as well. He added that the implications of the technology include greater economic independence for individuals, and a higher degree of resiliency for society as a whole.

“It will be a gradual improvement, and people may not notice it immediately, but 20 years from now we may find that we are able to better withstand some cataclysmic events.”

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