By Ishbel Matheson
BBC News, Kenya
On a chilly hilltop high above Kenya's Rift Valley, Jackson Chipyagon, 40, chops up wood to keep a small fire smouldering outside his shack.
Kenya is sitting on massive power supplies, which are hardly used
His family - his wife and six children - use fire for cooking and warmth, just as his ancestors did.
Modern amenities like electricity have not yet reached his home. But even if he had power, he is not sure how useful it would be.
"Sure, we want electricity," he says. "But it's expensive for us. We only have meagre earnings. So even if we get electricity, it's hard to afford it."
Mr Chipyagon's farm overlooks Africa's Rift Valley, a giant fissure in the Earth's crust running 9,500km from Lebanon to Mozambique. The plumes of escaping steam, and bubbling lakes, hint of volcanic turmoil beneath the surface.
Experts from the United Nations say if this geothermal energy were harnessed, it could provide power to some of the world's poorest nations.
Eritrea, Ethiopia, Djibouti, Uganda, and even Zambia have the potential to tap in. But so far, Kenya is the only nation which has made headway.
Some 200km from Mr Chipyagon's farm is the Hell's Gate National Park, with its strange rock formations and spouts of hissing steam. But even stranger is the mixture of wilderness and industrialisation.
Impala graze among a network of heating pipes. Giraffes nibble at acacias, metres away from a giant power-generating plant.
These roses look even redder thanks to geo-thermal power
But the fumes belching from the chimneys are not polluting petrochemical smoke. They are eco-friendly water vapour, which drifts off into the blue sky.
The Ol Karia station is the continent's biggest geothermal power-generating plant. It takes its name from a nearby volcano, which erupted 150 years ago and is still active.
There are 22 wells across the site, piercing the Earth's crust, and tapping into rock as hot as 345C deep below the surface.
Water pumped into the well produces steam, which powers the turbines.
Silas Simiyu, Ol Karia's development director, says: "Since geo-thermal is an indigenous energy source, we should start with what is ours - not with importing these petroleum products."
But even Kenya has been slow to exploit this energy source. The Philippines started geothermal work in the early 1980s - the same time as Kenya - but now generates 20 times more power.
Mr Simiyu attributes the sluggish development to bad policies and bad politics. In the past, hydroelectric dams - the main source of the country's electricity - have been much more appealing to Kenya's rulers.
Grand projects, built in a politician's constituency, help generate employment and shore up electoral support.
According to Mr Simiyu, the crunch came during the big drought of 2001. Kenya was plunged into darkness for hours every day as the dams dried up. The power generated by geothermal means saved the country.
In 2002, a second power plant at Ol Karia started work. By 2010, a third should have been completed.
This is part of an upsurge of interest in geothermal power across the region. In Uganda, the government is looking into "mini-geothermals", power plants which would generate enough electricity to light up remote villages.
But one of the biggest obstacles preventing the development of geo-thermal is start-up costs.
"The risks involved in drilling - that's the stumbling block," says Ann-Marie Verken of the United Nations Environment Programme (Unep).
Potential sites could be identified and millions of dollars spent drilling wells, but the result could be zero. The consistency of heat or the rock type may not be suitable for geothermal electricity.
This unpredictability makes African governments nervous. Unep, through its Global Environment Facility, is trying to help with the costs and to encourage private investors.
The potential for Kenya's businesses can be seen at Oserian flower farm, close to Lake Naivasha. The company says it has the first geo-thermally heated greenhouses in the world.
Geo-thermal power means people don't have to chop down trees
Engineering director Bruce Knight, reckons that the product - long-stemmed roses, destined for Europe - has already improved as the company can now afford to heat its greenhouses through the night.
The company was lucky because it had two existing wells on its land, drilled by the national power company, Kengen.
Kengen abandoned the wells, believing they lacked potential. But after investigation, Oserian decided the wells might provide enough energy to power a flower farm.
They bought a ready-to-assemble geothermal plant from Israel - estimating that the million-dollar costs would repay in four to six years.
The flower farm is now almost entirely dependent on geothermal energy, which is cheaper and more reliable than the national grid.
In the increasingly hi-tech world of rose-growing, geothermal is giving Oserian a competitive edge.
"All the control systems from the ventilation, the heating, the carbon dioxide - it's all controlled through computers," Mr Knight says. "You have to have a good power supply for that."
For Africa to develop, it must have access to affordable power. But there is clearly a long way to go.
As the sun sinks over the Rift Valley, only a few pin-pricks of light shine. The rest is darkness.
The company which runs the national grid, estimates 85% of Kenyans do not have access to electricity.