Engineer turns sand into clean energy, sets sights on global markets

At the 2025 P4G Summit in Hanoi on April 16-17, Ho Viet Hai’s sand battery startup, Alternō, stood out among dozens of green tech exhibitors from various countries. It was one of the first three booths visited by Prime Minister Pham Minh Chinh along with the prime ministers of Laos and Ethiopia, the UN deputy secretary-general, and Cambodia’s deputy prime minister.

Hai, 40, is the co-founder and CEO of Alternō. He says the idea for the battery took shape when he lived and worked off-grid in a remote part of Lam Dong Province in the Central Highlands in 2023, relying entirely on solar power and lithium batteries.

He soon realized that lithium batteries were ineffective at providing the heat needed for daily activities or commercial use. That led him to explore sand-based thermal energy storage, a technology researched in Europe but mainly used for heating buildings in winter.

Unlike conventional batteries that store electricity, Alternō’s sand battery stores heat by warming sand to 600–1,000°C using solar or wind power, and retains it in insulated tanks for up to six months.

Co-founder and CEO of Alternō, Ho Viet Hai. Photo by VnExpress/Trong Dat

"I thought why not apply sand batteries to agriculture where reliable heat is crucial for drying and processing but fossil fuels remain the dominant energy source," Hai says.

He took the idea to Antler, a Singapore-based accelerator. Within 10 weeks he secured seed funding, allowing his team to begin research and testing. Nine months later they completed a prototype and signed their first commercial deal.

"Today, 51% of heat used in industrial and agricultural processes comes from fossil fuels," Hai says. "Our technology helps cut reliance on those sources."

Trials showed the battery helps factories and farms reduce monthly energy costs by 5–15% with just a switch in the heat source and without requiring changes to production lines.

Alternō has also applied the technology to waste treatment. One pilot project dried 10 tons of wet coffee grounds per day, cutting waste volume in half and halving treatment costs.

"This is how technology can reduce both expenses and environmental impact," Hai says.

Less than two years since its launch, Alternō is expanding globally. In addition to Vietnamese clients, it has received orders from Japan, the Philippines and Kenya, a country with a thriving coffee industry.

Hai says: "Most people have never heard of sand batteries. They hesitate to invest without seeing results."

Sand batteries use solar or wind energy to heat sand, which is then stored in specialized containers for thermal energy retention. Photo by VnExpress/Trong Dat

A key breakthrough came via P4G, an international platform that supports public-private partnerships to promote green growth in countries including Vietnam, Kenya and Colombia, he says.

"They helped fund our trial units, which we installed directly at factories. Customers could try them at no cost and only sign contracts after seeing the benefits."

A standard Alternō system, including solar panels and a thermal storage tank, costs around US$30,000. The company also offers a lease option at $300 per month under a four-year agreement. Agricultural systems cost around VND500 million ($19,255).

Alternō’s largest order so far has been for $2 million. Clients include multinational firms with emissions-reduction goals, farming cooperatives and shared household users.

After a period of product development, Alternō is now targeting markets in Asia, Africa and Latin America, regions with strong agricultural and food-processing sectors still reliant on fossil fuels.

"My goal is to help build a more sustainable future for light industry and agriculture in Vietnam and other developing countries," Hai adds.