South Africa exploring option for geothermal power

South Africa exploring option for geothermal power Cape Town, South Africa (source: flickr/ dorena-wm, creative commons)
Alexander Richter 19 Oct 2010

A recent article looks into the potential options for geothermal development in South Africa, despite its remote location from geothermal hot regions.

A recent article from South Africa, looks into geothermal potential in the country, saying that so far “little attention was paid to research into geothermal energy, largely because South Africa’s geology of solid rock precludes large geo- thermal discovery but also because of the lack of government support and the significant costs involved, just for the feasibility phase of such projects”.

“However, the energy crisis and the drive for renewable-energy generation have sparked new interest in the possibility of generating energy from heat that is readily available from the earth. Technological advances over the past few years also indicate that the use of geothermal energy may be viable in areas like South Africa.

There is, currently, no large-scale geothermal production in South Africa, since coal is abundant and relatively cheap, supplying the largest part of the country’s energy requirements. ”

On the prospects for geothermal development in South Africa the article continues: “South Africa’s geology is such that the heat is very deep and requires significant drilling to obtain clear feasibility. “We have gathered significant data from various sources about different parts of the country, which estimates that we must go down to between 4 000 m and 6 000 m, depending on the exact location.”

This was previously not feasible, owing to the cost of drilling but, now, with energy shortages and increased electricity costs, he believes that the finances should become available.

There is some investor interest coming from the mining and industrial sectors, which HRP Geothermal Power has been exploring. Ochse points out that this interest is in large, long-term capital projects with the same magnitude of effort for each megawatt as for coal-fired power plants, but with the advantage that the “fuel” or heat source is free once you get to it.

“We would generally target a 50-MW or more installed capacity geothermal plant, as the financials make sense at this size, with the risk-weighted capital cost amounting to about R1,45-billion,”.

HRP Geothermal Power says it has discovered that an Organic Rankine Cycle (ORC) power plant is the preferred tech- nology for South African application, as it allows for lower-temperature heat sources, in the 100 °C to 150 °C temperature range.

The ORC is unlike conventional Rankine Cycles, which use water or steam as a working fluid, as it uses an advanced refrigerant as the working fluid. This allows the cycle to generate high-pressure ‘steam’ from lower-quality heat to drive its turbine and generate power. This also means that ORCs can operate between smaller temperature differentials than traditional Rankine Cycles.

Jones says that South Africa is far removed from active plate boundaries and heat flows to the surface predominantly by conduction. Thermal gradients vary from as low as 8 °C/km to as much as 40 °C/km. “These values for heat flux and thermal gradient are considerably lower than those experienced in geothermal areas, but the heat is there if one goes deep enough – it is a matter of extracting it at economically viable rates,” he explains.”

For the full article see link below.

Source: Engineering News