Weekend Read: It’s time to get Sirius


From pv magazine 06/23

It was, almost, a perfect match. The eight-story building in central Barcelona was exactly what Wallbox wanted. By February 2020, the company headquarters, 30 km away, was getting crowded. “We managed to find a building which checked all the boxes except one – power availability,” says Daniel Utges, Wallbox’s head of energy.

The building only had access to 173 kW of grid electricity but Wallbox needed 300 kW to 400 kW. Testing EVs and chargers is energy intensive. “The utility told us we can solve this problem by investing €500,000 ($536,000) in a new transformer but we thought there are better ways to spend such money,” says Utges.

Big data

A year before becoming the first Spanish unicorn (a company worth more than €1 billion) to be listed on the New York Stock Exchange, Wallbox decided to develop a grid-connected building as a microgrid. It invested around $400,000 into 400 kWp of solar panels, 560 kWh of stationary battery capacity, 23 of its Quasar bi-directional EV chargers, and 23 Nissan Leaf vehicles, each with a 62 kWh battery. “We needed something on top that understands when each of these assets should be consuming or producing energy in real time and this is how Sirius was born,” says Utges.

First unveiled in 2021, Sirius is expected to be released onto the market in Q1 next year. By choosing the greenest and cheapest energy source available, Sirius optimizes building energy consumption and saves money. “Thanks to Sirius we had no blackouts in the building and we are saving more than 50% on our energy bills at the Barcelona headquarters, which were supposed to amount to more than €200,000 per year,” Utges says.

On March 27, some 54% of the building’s 2.4 MWh daily energy consumption was covered by solar and only 16.5% came from the grid, saving around €420. Sirius relies on big data analytics to integrate inputs including real time pricing, weather forecasts, and installation restrictions such as wiring capacity. It does not control loads such as heating, ventilation and air conditioning; lighting; or water heating. “We treat the building as a black box but there is a lot of variability in energy consumption, depending on the days of the week or if the lab is open or closed,” says Utges. “Integrating an artificial intelligence layer would help us learn from the building behavior and improve Sirius by 10%.”

Capturing opportunities

Most EV fleet charging systems are much simpler. Power is split evenly between charging stations without considering user requirements or real-time availability. Business information company BloombergNEF anticipates there will be 77 million EVs by 2025 and 229 million by 2030 and managing their grid impact will become a challenge. Add on-site solar and storage and there is even more for algorithms to balance.

Wallbox is not alone in investigating smart EV charging in a microgrid. Dublin-headquartered power-management company Eaton has commercialized its “buildings-as-a-grid” approach and tested it at its office in Le Mont-sur-Lausanne, Switzerland.

The project harnessed 100 kWp of rooftop solar, a 20 kW/21 kWh battery, 16 alternating-current EV chargers, and a public DC fast charger. “We turned our office building into a real-world testbed to gather statistics about how our buildings-as-a-grid approach performs and achieved outstanding results, including 60% energy cost savings, averaging CHF 1,685 ($1,877) per month,” said Fabrice Roudet, general manager for the energy transition at Eaton, who was referring to the July to December period.

In the United States, Powerflex has deployed around 10,000 chargers with more than 330 MW of solar and around 44 MWh of battery storage on commercial premises. A California Institute of Technology spinout acquired by EDF Renewables in 2019, Powerflex claims its patented software can reduce the cost of electrical system upgrades and peak demand charges by up to 60%, and can enable customers to install up to four times the number of stations than a standard configuration.

Building load

“We always take into account the building load,” says Powerflex CEO Raphael Declercq. “We use patterns [e.g. predictable office-building demand] and real-time information [e.g. air conditioning consumption increasing, balanced by reducing EV load]. It is essential to have a comprehensive view when a building and EVs are on the same meter.”

Most EV charging companies are at the early stage of integrating devices with broader on-site power management needs and adding bi-directional charging has been mostly limited to research.

At Wallbox HQ, cars are charged with grid power during the night and discharge electricity to the building during daytime. “We use the power from our batteries in the early morning, when electricity tariffs in Spain are high, and then recharge them with solar power during the day to reduce our electricity consumption from the grid in the late afternoon,” says Utges.

“Our fleet of cars is intended for internal mobility, from the HQ to the factory (5 km), and some for commercial visits, but not to go on a long trip, to Madrid, for example,” he explains. “This can be booked and we can prepare a car for a long a trip as well but it’s probably easier to go to a fast charger here on the premises and fill your car in half an hour, than to use Quasar, that gives you only 7.4 kW.”

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