The Solar PCU

Every revolutionary product has an origin story. For Su-Kam's Solar Power Conditioning Unit — the device that would win the ISA Technovation Award, take Su-Kam to Intersolar Europe in Munich, and ultimately define the company's identity as India's solar pioneer — that story begins around 2007, in a government office in Tamil Nadu.

The Man from TEDA

The Tamil Nadu Energy Development Agency (TEDA) was the state government's vehicle for renewable energy deployment. In 2007, it was headed by an IAS officer named Sudeep Jain, a BITS Pilani-trained electrical engineer who would later rise to become Additional Secretary at the Ministry of New and Renewable Energy (MNRE) and pursue a PhD in solar energy at IIT Madras.

Jain's ambition was specific. He wanted smaller solar PCUs — power conditioning units that could serve rural Tamil Nadu households — in capacities ranging from 300 watts to 2 kilowatts. Not the large industrial systems that dominated the market. Compact, affordable units that could bring reliable solar power to villages where the grid was unreliable or absent.

Su-Kam's team in Tamil Nadu connected Kunwer Sachdev with Jain, and the two struck a chord immediately. Both men shared the same conviction: solar energy in India would not succeed as a luxury product for urban rooftops. It had to work at the village level, at the smallest scale, for the poorest households.

The Impossible Specification

What followed was one of the most technically demanding product development projects Su-Kam had ever undertaken.

Sachdev and Jain worked together to create joint specifications for the new Solar PCU. The device had to do what no Indian solar product had done before: not just convert and store solar energy, but monitor and record generation data. TEDA needed proof that the systems were working — actual kilowatt-hour data from each installed unit.

The challenge was enormous. This was 2007-2008. Rural Tamil Nadu had no internet connectivity. No cloud infrastructure, no IoT ecosystem, no cellular data networks reaching remote villages. The monitoring data couldn't be uploaded — it had to be stored locally, inside the processor of each Solar PCU, and physically collected by field teams.

Su-Kam's R&D team had to engineer a solar inverter that was simultaneously a power conditioning unit, a charge controller, a grid interface, and a data logger — all in a compact, affordable package. The communication protocol alone specified 26+ telemetry parameters transmitted in exactly 114 bytes.

"That was very tough to develop," Sachdev recalls. "The specifications were joint — what TEDA needed and what we could engineer. The monitoring requirement pushed our R&D beyond anything we'd done before."

The Breakthrough

Under Sachdev's direct guidance, Su-Kam's R&D team worked through the technical challenges methodically. The Solar PCU that emerged was unlike anything on the Indian market. It integrated the solar charge controller, the inverter, and the grid charger into a single unit — eliminating the need for separate components.

By 2010, the TEDA project was a success. Su-Kam's Solar PCUs were deployed across rural Tamil Nadu, and the generation data TEDA needed was being collected from every unit. The handheld data collection device that Su-Kam designed specifically for this project became the bridge between remote installations and TEDA's data requirements.

As Sachdev puts it: "That project made us heroes. After that, there was no looking back."

The Sudeep Jain Connection

There is a certain poetry in the fact that Sudeep Jain — the IAS officer whose vision pushed Su-Kam to create the Solar PCU — went on to become Additional Secretary at MNRE. Under his later leadership at TEDA, Tamil Nadu installed three lakh solar rooftops and one lakh solar streetlights in four years.

The Solar PCU story is a rare example of what happens when a visionary bureaucrat and a determined entrepreneur find each other. Jain had the policy mandate and the technical understanding. Sachdev had the R&D capability and the manufacturing scale. Together, they created a product that didn't just serve a government tender — it created a category.

Every Solar PCU that Su-Kam sold after 2007 — to dealers across India, to institutions, to villages, to international markets in 90 countries — carried the DNA of that original TEDA specification.

The Radical Next Step: A Pure-DC PCU

The AC Solar PCU made us heroes. But those same TEDA conversations had planted a second, more radical idea — one we could not let go of. Solar panels generate DC. Batteries store DC. The lights and fan in a basic village home do not actually need alternating current at all. So why convert DC to AC and back, losing power at every step? Why not run the whole home on DC directly, throw out the inverter stage entirely, and build the cheapest, most efficient solar home system possible?

We started developing it: a 12V, 120W Solar DC PCU — enough to run LED lights and a fan all night in a modest home. The DC concept was too unconventional for that first government tender, and it was set aside. But we did not give up on the technology. We went looking for another partner.

UPNEDA Said Yes — 50,000 Homes

The Uttar Pradesh New and Renewable Energy Development Agency (UPNEDA) was open to it. UP had some of the worst power cuts in India, and rural households were spending heavily on kerosene for lighting. A 12V/120W Solar DC PCU that could run lights and a fan the entire night on a small battery was exactly what the state needed. We convinced UPNEDA, the project was sanctioned, and over the deployment period Su-Kam's Solar DC PCUs were installed in 50,000 homes across Uttar Pradesh — fifty thousand families who had lived with kerosene lamps now had electric light and a ceiling fan running on the sun.

The BLDC Fan Challenge Nobody Had Solved

The biggest challenge was the fans. A 120W DC system cannot power a conventional AC ceiling fan. The answer was BLDC — Brushless DC — motors: a BLDC fan runs directly on DC, consumes a fraction of the power, and lasts far longer. The problem was that nobody in India had heard of BLDC ceiling fans at the time — no manufacturers, no supply chain. We developed the motor-control technology in-house and worked with a fan manufacturer to bring it to production, making Su-Kam one of the first companies in India to deploy BLDC fans at scale, years before they became today's standard. Getting DC lights manufactured was just as hard; everything had to be developed, sourced and standardised from scratch.

The Patent: Grid-Integrated MPPT

As the Solar DC PCU matured through the UPNEDA deployment, we kept improving it — and the most important addition was grid integration. A purely solar-and-battery system has one critical weakness: consecutive cloudy days drain the battery dangerously, and for a rural UP family a dead battery meant no light and no money to replace it. Our solution was to integrate the grid as a battery guardian. The moment battery voltage dropped below a set threshold, the grid charger activated — not to run the load, but purely to bring the battery back to a safe level, then hand control back to solar. The lights and fan never went down, and battery life extended dramatically because deep-discharge events were eliminated.

Discovery Channel Came to Film It: Sun Fuel

The scale of the UPNEDA deployment did not go unnoticed. Discovery Channel came to India to document it, and the resulting documentary — Sun Fuel — covered the 50,000-home project: the families, the technology, and the story of how an Indian company built and deployed solar home systems at a scale few countries had matched.

A meeting in Tamil Nadu. A shared vision. A product that changed everything.