With the economy in a holding pattern because of COVID-19, energy use is uncharacteristically low. A couple of weeks ago Blue Lake Rancheria began to worry that the low demand spelled trouble for its microgrid. However, the microgrid controller was thinking a step ahead of everybody.
The Humboldt, California tribal facility installed the microgrid about three years ago to keep the power flowing during outages and to lower energy costs and emissions during normal conditions.
The microgrid includes solar, battery energy storage and diesel back-up generators that serve a casino and hotel. During last fall’s public safety power shutoffs, when the surrounding community found itself in the dark, the rancheria opened its doors as a place of refuge. Most notable, the rancheria was credited with saving several lives because it made room in its hotel for medical patients dependent on equipment that uses electricity.
But COVID-19 is a different kind of disaster, an uncharted territory for microgrids. Lack of power is not the concern; too much power is. Blue Lake Rancheria was worried that its solar panels were producing more electricity than its closed facility would use. Under normal circumstances the solar PV provides 80% of the facility’s peak load.
Danger of microgrid tripping off
The microgrid is connected to the utility grid, and the facility managers feared that the unusually low demand for power might cause the excess solar to backfeed onto the grid. If this happened, the microgrid would trip off within seconds because the local utility, Pacific Gas & Electric, does not allow the microgrid to export power into the distribution grid due to operating constraints. On top of that, excess power production represented an economic waste.
The microgrid uses a Siemens controller, the Spectrum Power Microgrid Management System. So the tribe called Siemens about its concerns.
Shashank Pande, software solutions architect for utility control center solutions at Siemens Digital Grid, logged in to see what was going on. Pande saw that the microgrid controller was one step ahead of everybody and had already figured out the looming problem — and averted it.
The controller was able to do so because it uses a “model based” approach — it doesn’t operate under prescriptive rules, he explained. The controller has not been programmed, for example, to charge or discharge at certain times of day. Instead, it makes educated predictions about the future and then adjusts the charging accordingly.
Courtesy of Siemens
Microgrid controller adapted on its own
“It adapts on its own,” Pande said. “It looks forward 24 hours and then it says, okay, based on the past and the weather forecast, what is my estimate of load and generation in the next 24 hours?”
The load prediction engine adapted to the new load profile quickly, he said, and the microgrid subsequently adapted its dispatch to match. The microgrid changed its schedule for battery charge and discharge to avoid loss of solar and inadvertent export to the utility. All of this was done quietly, autonomously and automatically with no external assistance or human supervision, he said.
The controller also is took into account — as it always does — how to minimize costs. Responding to changes in grid prices day and night, it charges the battery with grid power when prices are low and then discharges the energy for use by the rancheria when prices are high.
Blue Lake Rancheria helping community during COVID-19
Blue Lake Rancheria has closed its businesses to prevent the spread of COVID-19. But once again the tribe is using its microgrid to serve the broader community during a disaster, this time as a base to deliver meals.
“Our microgrid control systems are allowing us to reduce electrical loads, operate economically, and maintain maximum use of solar energy. With clean, controllable power, the tribe is continuing to provide critical government programs, such as home meal deliveries to the elderly across a 1,400 square mile service territory,” said Jan Ganion, director of sustainability & government affairs at Blue Lake Rancheria.
Below is a depiction provided by Siemens that shows the microgrid adjustments to the COVID-19 reality. Specifically, it demonstrates that:
- The load forecast has already adapted to the low load predicting reduced load.
- The battery is optimally used to absorb excessive solar PV production and return the energy back when it is most optimal (economical).
- The system is comfortably avoiding any back-flow into the grid.
- It is notable that Blue Lake Rancheria increased their battery capacity to 2,000 kWh, but Spectrum Power MGMS is only using 25% of it (500 kWh) because it is enough to minimize the cost and operate the system within the network constraints. Over or under using the battery would cost more.
Courtesy of Siemens
