Gridless engineers build makeshift computer laboratories for bitcoin mining.
Millions of litres of water crashing over rocks and down rapids makes the Zambezi scream deafening.
Another sound cuts through Zambia's bush: a bitcoin mine's high-pitched screech.
"It's the sound of money!" Philip Walton smiles as he examines the shipping container with 120 computers doing sophisticated bitcoin transaction computations.
They receive bitcoin automatically from the network.
This is the oddest bitcoin mine I've seen, in far northwestern Zambia near the DRC border.
The river's closeness attracts bitcoiners, even though water and electronics don't mix.
Philip's mine is immediately connected to a hydroelectric power facility that draws water from the Zambezi through massive turbines to create clean electricity.
Most crucially for bitcoin mining, it's inexpensive.
So inexpensive, Philip's Kenya-based company Gridless decided to haul its shipping container full of fragile bitcoin mining machines 14 hours from the nearest big city to set up here.
Daily revenue per machine is $5 (£3.90). More if coin prices rise, less if they fall.
Philip occasionally looks at his smart watch's home screen, which shows bitcoin's dollar value fluctuating.
The bitcoin now costs $80,000, but Philip claims they can make a profit even if the price drops due to the site's inexpensive electricity and energy provider connection.
We realized we needed to cooperate with the power provider and split income to improve mining economics. We're prepared to travel so far since we can receive cheaper power "says.
The massive Zengamina hydro-power plant is a small grid for the local community.
Mining bitcoin using computers and cables
British-Zambian Daniel Rea runs the facility after his missionary family built it to power the local hospital.
The project powers 15,000 locals, but limited community adoption has prevented it from making a profit.
Having bitcoiners establish up shop here transformed the business.
We wasted almost half of our energy every day, which meant we weren't generating enough to cover our operational costs. Daniel adds Gridless' game-changing alliance was vital since we needed a significant power consumer in the area.
Since 30% of the plant's revenue comes from the bitcoin mine, they can keep local pricing low.
Zengamina residents are unaware about Bitcoin and its economics.
A few dozen shed-like buildings line a crossroads in the town a few kilometres from the factory.
Only one business has a fridge, and a dozen kids take turns choosing a tune to blast from a common computer, making grownups groan.
Zengamina hydropower
After the hydro-electric plant went online in 2007, it took years to connect it to the municipality and subsequently to individual houses and businesses.
Some people, like barber Damian, still appreciate the novelty of becoming wired a year and a half ago.
"I couldn't accomplish anything without power. I bought everything at once when I obtained power."
He's serious. A TV playing music videos, Christmas lights, and his hair clipper make his modest barber shop powerful at night. Young folks gather at his barbershop like moths in a youth hostel.
"Getting power changed my life," he beams. "The money I'm earning now from the barbershop is helping me pay for school fees again."
Damian's electricity adoption is business-driven. The two rooms of his modest abode share one light bulb.
Sisters Tumba and Lucy Machayi view the world from the crossroads.
They're phone-obsessed like many teens.
"Before the town got power, it was basically just the bush," Lucy.
They said modest solar panels provided their limited energy.
"No fridge, TV, mobile phone network," explains Tumba.
"Electricity completely changed the lives of people here," Lucy says.
We can charge phones and have network. We can communicate."
Zambian ladies Tumba and Lucy Machayi
Few people here know or care about the bitcoin mine that helps the hydro-plant run.
But soon they'll see the container rattle through town again on its way to another site.
Zengamina Hydro received a big investment to extend to new communities and connect to the national grid.
Soon, Zengamina will sell its extra electricity to the national grid, making bitcoin mining unprofitable.
Phillip and crew are optimistic and say this is wonderful news. After several successful years, they are proud to have assisted Zengamina. Naturally, profited in bitcoin.
The business thinks they can locate their bitcoin mine near stranded electricity in several areas.
Gridless has six such sites in three African nations.
North of Zengamina, another bitcoin mine uses extra electricity from Virunga National Park's Congo hydroelectric facility. The park claims it funds conservation efforts.
Gridless now aims to build hydro-plants from scratch to mine bitcoin and power rural regions.
Co-founder Janet Maingi said the business is seeking tens of millions for the project.
They're working on Zengamina-style run-of-river hydropower projects, and the continent has "untapped hydro potential" she says.
"A consumer-driven, adaptive energy model is essential for scalable, affordable, and sustainable energy access that meets the needs of African communities," she says.
The non-charitable firm believes bitcoin is the only way to ensure long-term economic sustainability for developers and investors.
Finding places for new plants or tapping into existing ones is straightforward.
Some governments and corporations oppose bitcoin as an energy-greedy and selfish use of electricity that might be utilized by rural people.
The corporation claims that the motive is to sell to the highest buyer, which is always the local community.
Bitcoin mining at scale may strain public electricity infrastructures without incentives or restrictions, as history shows. In 2020–2021, Kazakhstan's mining boom raised energy demand by 7% until the government stifled it.
Kazakhstan bitcoin mining
Bitcoin mining's new hotspot, the US, has seen disputes between miners, locals, and residents during peak energy consumption.
Authorities have agreements with some mining corporations to shut down their computer-filled warehouses when the grid requires balancing.
In January, the restored Greenidge gas power plant in New York had to shut down bitcoin mining to give electricity to the grid amid a cold snap.
If President Donald Trump wants bitcoin "mined, minted and made in the USA" these agreements must be prevalent.
Industry environmental effect is another key worry. Bitcoin mining consumes as much electricity as Poland.
Cambridge University academics, who estimate bitcoin's energy use annually, say a more sustainable energy mix is emerging.
Zengamina setups are a small portion of mining.
However, they are a rare problematic business that creates more than digital money.