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Develop renewable solar energy resources


I would like to make some comments on the Zimbabwe Electricity Supply Authority (Zesa) article on the electricity supply situation in Zimbabwe published October 2 2011.

The background situation is besides Kariba and Hwange there are other generating facilities sitting idle. All that has to happen is for the National Railways of Zimbabwe to pull up its socks and supply coal to these generating stations.

In the 1990s, the University of Zimbabwe and Colorado Boulder undertook a study on the response of the Kariba plant to global warming.

It showed that with temperature increases in excess of 3°C Lake Kariba would regularly fail to supply sufficient water to maintain the then installed generating capacity from late October to March.

This was amply demonstrated in the 1991/92 drought, when mean temperatures rose by 2°C in Zimbabwe. Since then Zambia has increased its generating capacity, but this does not create more water.

From observations, the Zambezi River discharge has been decreasing for the last thirty years at the rate of 35% per decade (see graph).

However, both Zambia Electricity Supply Company and Zesa see the option for increasing power output as the installation of more generators, a strategy that will probably work for most years in the near future, ie the next 25 to 30 years.

After that, unless the climatic trends change to result in increased flows long term, the flow of the Zambezi will be inadequate to for the water demand created by the increased number of generators.

What then are our future options?
Option one is to do nothing, hoping the Zambezi will always provide

Option two is to look for alternatives to complement Kariba. These alternatives are:

To increase our coal-powered generating capacity, thus increasing our greenhouse gas contribution

To develop the Batoka Gorge site

To go nuclear, with the hazards amply demonstrated by the Japanese and Chernobyl cases

To co-operate with our Sadc partners and develop the Congo Basin, which Europe has had its eye on

To develop our renewable solar energy resources

The first four options involve considerable capital investment which would lead to more borrowing from IMF.

I would like to dwell on the last option. There are now thousands of cases in the world in which installed domestic solar systems actually feed into the national grid. In Australia, the government gives generous incentives for domestic solar power generation.

Here in Zimbabwe, we have a unique situation in which we have areas of high roof surface density in the high-density suburbs.

A thousand solar units can be installed in a 10-square kilometre area. If on each high-density house three KW80M panels were installed, one dwelling unit would generate 2,4 KWh per day assuming average of 10 hours sunshine.

In a month, the household would generate 72 KWhs, an amount generally not used in such households during the day.

If such units were installed on 10 000 households, the total generating capacity would be 720 MWhs — equivalent to what Kariba produces.

The price of each of the panels is A$320. Thus, the cost of panels per house would be less than $1 000. Thus a modest $10 million dollars would provide for 10 000 households.

Knowing Zesa, they would not give this for free. If the panels were on a loan payable in say ten years, the monthly payment would be $7,50 for the panel and probably next to nothing for power consumption, after which the household owner would own their mini power station.

The particular panel quoted above has a guarantee of 25 years. Not included in this costing is the wiring cost (neglible) and the rectifier units. The latter need not be installed in every house hold unit, but can be shared between, say, 10 houses.

In the area between Mhembwe, Mutamba, Shuramurova and Muwonde streets in Mufakose, an area of 0,01km2, there are twenty households, ie a generating capacity of 140KWhs. In a square kilometre then there would be 14 000 KWhs (1,4 MWhs) per month.

What is the total area of high-density suburbs on Harare? The total generating capacity for Harare, including Chitunwiza, would be in the region of 500MWh per month.

Approximately double that if we include Bulawayo, Gweru and Mutare, then we have a potential GWh power station. The cost of building such a facility on conventional desgns would be simply prohibitive.

In the low-density suburbs a larger number, say 10, panels could be installed per household. In addition, all industrial and institutional buildings, such as UZ and schools, with large roof areas, can be recruited into the programme

The point of this exercise is to show that, for a modest outlay, we have powerhouses in our high-density suburbs that compare quite competitively with our high-cost investment power stations — and there is no maintenance cost for the sun!

  • Prof Chris HD Magadza is a Fellow of the Zimbabwe Academy of Sciences. He writes in his personal capacity.
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