The bottleneck is the job
A factory in California ran for eight months without the utility. No grid, no problem - a stack of batteries and a layer of software did the work while the paperwork crawled. That kind of story is the whole pitch at Critical Loop, and Nanna Nielsen is the person who turns the pitch into a business that holds together. As Chief Business Officer she sits where the engineering meets the customer, the capital and the calendar.
Critical Loop builds behind-the-meter battery systems wrapped in autonomous control software. The promise is almost rude in its simplicity: get power in days or weeks while the permanent grid connection - the one that can take years - catches up. Factories, transportation hubs, data centers, airports. Wherever electricity is the thing standing between a plan and a working site, the company shows up with a modular stack and a way to switch it on.
In April 2026 the company closed a $26 million Series A, led by Conifer Infrastructure Partners and Hanover, with Better Ventures, Climate Capital, Adapt Nation Capital and Cyrus Ventures along for it. The round pushed total committed equity and debt to roughly $49 million. Nielsen marked the moment plainly, calling it fuel for a mission she describes as "a world with abundant, affordable energy where power is available and reliable." The money goes toward partners like San Diego International Airport, where Critical Loop won a competitive bid to optimize on-site solar and batteries against an 11-megawatt load.
Before the batteries, the banks
Here is the part that makes people blink: almost none of her career was about energy. Nielsen spent seven years in capital markets, working in e-commerce and foreign exchange, finishing as a Senior Manager at Saxo Bank. She held leadership roles in Commercial Banking at Lloyds Banking Group. Then she went to Cambridge for an MBA at Judge Business School, where she served as the alumni representative for her class and wrote, with some understatement, an essay called "The Balancing Act" about discovering there was more in the bag than she expected.
After Cambridge she landed at GoCardless, the fintech unicorn, and ran global operations - banking infrastructure, customer experience, compliance, payments. The scoreboard from that chapter is the kind that does not need a footnote: more than $52 billion in transactions for over 93,000 businesses. Somewhere in there she also took a turn as COO of a Los Angeles drone startup, because apparently moving money and moving aircraft were not different enough to scare her off.
The pattern is not really about industries. It is about plumbing. Payments and power grids share an unglamorous truth: the magic everyone wants depends on a backend nobody sees, and the person who can make that backend reliable, compliant and fast is worth a great deal. Nielsen is, by her own framing and her employer's, that person - the one who "brings operational rigor and experience building high-performing teams to drive scalable, sustainable growth." Read past the LinkedIn polish and it means: she makes the machine behind the mission actually function.
Beyond profit, on purpose
The move to energy was not a random swerve. Back in her Cambridge days she was already drawn to social finance and what she filed under "beyond profit" - the idea that commercial skill and social impact do not have to live in separate buildings. Clean energy is where that interest finally got a full-time job. Critical Loop's mission, fixing the electric grid by making power more accessible and efficient, is exactly the kind of place where an operator with a conscience and a spreadsheet can do real damage to a real problem.
Illustrative. The whole business is the size of that gap.
What makes her unusual on an energy founding team is precisely what she is not. She is not the SpaceX engineer (that is CEO Bala Ramamurthy). She is not the climate-tech data scientist (CTO Lydia Maher). She is the one who has already scaled the boring, essential parts of a fast company twice over, in industries where a missed compliance box or a broken process costs real money in real time. In a startup racing to plug in airports and data centers before the grid can, that experience is not a nice-to-have. It is the difference between a demo and a company.
She is Danish by origin, Cambridge by training, and Long Beach by zip code now - part of the Los Angeles cluster where aerospace talent, climate capital and an overloaded grid all happen to collide. It is a good place to be holding a stack of batteries and a track record of making complicated things run on time.
The headline number will be the $26 million, and the photogenic story will be the airport and the factory that ran for eight months in the dark. But the quieter bet Critical Loop made is on people like Nielsen: operators who have done the unsexy work of scaling a regulated, capital-heavy business and lived to tell about it. The grid does not need more enthusiasm. It needs someone who knows how to close the books, keep the partners happy and ship the next site on schedule. She has been doing versions of that for a long time. The voltage is new. The job is not.