One of the most imaginative and innovative schemes to build what amounts to a solar power station is the Presidential Solar Scheme now being implemented on 400 houses in Glen View 3 in southwest Harare.
This is an installation by Zimbabwe Solar Energy Company, a subsidiary of Prevail Group International, to fit solar panels to the roofs of the houses and then generate electricity that is sold to Zesa, with the surplus obviously coming during the day when household use is fairly low, and Zesa in return ensuring that there is no load shedding as darkness falls and the flows move in the other direction.
A major hassle with solar power stations is the need for a block of land, not cheap however you work it and often requiring complex negotiations and planning approval, and quite often some sort of construction to raise the solar panels above the surrounding vegetation and other shadowing structures, and then to have reasonable security.
The Glen View 3 scheme avoids much of this. The roofs are already there, in the sunlight, and tall trees are rare in high density suburbs simply because there is not enough room and the city council never bothered to line the streets with large jacarandas.
Gardens tend to have shrubs and short small fruit trees at best, and those do not shade the roofs. The home owners are able to maintain high levels of security and special planning approval is not needed for rooftop solar.
The houses are also reasonably close together, so the wiring is not a huge expense and in any case Zesa already has the basic grid in place. Modern technology allows the sort of net metering so that power can flow in both directions and be metered in each direction.
So far 80 of the planned 400 houses already have solar panels, and the company is continuing the work, so the scheme is not something that is "planned", but rather something that is under active construction and installation.
It is a pilot scheme, to see if it works and to see if the economics are as viable as the Government and investor have calculated.
We would like to guess that fitting solar water heaters, one of the largest consumers of electricity in any house, would make the scheme even more viable and ensure an even better flow of power out to the grid, minimising inflows from the grid.
Lighting at night with modern LED technology, and even the use of modern solid-state televisions, modern fridges, phone chargers, and even computers do not absorb much electricity.
It is fairly obvious that solar is the generating source of the future for much of Zimbabwe. Coal stations do produce a lot of carbon dioxide, and while Zimbabwe can balance the books by maintaining and expanding forests, locking up the carbon again, there are obvious limits.
The droughts of recent years have made it clear that hydropower is limited in usefulness and requires very large investments for giant new dams without the sort of supply of electricity that can pay for those dams. A lot of hundreds of millions of US dollars are needed for a modest output.
There has been quite detailed planning for a new giant hydro scheme at Batoka Gorge. Even with normal river flows in the Zambezi, the modest storage capacity of that dam would still have created wild swings in monthly output, the 2 400MW to be split evenly between Zimbabwe and Zambia only coming when the river is in flood, with predictions that this would decline by around two thirds at low water near year end.
And right now if that scheme was in place the river flows would be producing extremely limited output.
The two Kariba stations, and both Zimbabwe and Zambia extended their Kariba stations to a little over 1 000MW each, can average no more than a little over a fifth of their maximum output, although both authorities can use their giant stations to send a surge of peak power down the grid and then cut right back during the slack times, like midnight, to almost nothing to make the average.
So extra hydro capacity on the Zambezi is not the sort of grand solution that it was once thought to be. It might well be useful, but new calculations need to be done to work out the cost of the resulting power.
The Kariba stations in a string of years of normal to above normal flows, and with the dam wall paid for, were highly cost effective, but if the two authorities knew almost a decade ago when they were assembling the finances what the future would bring, we doubt if they would have gone ahead.
The growth of mining and industry has seen a lot of the electricity demand moving towards the daytime, when solar obviously works best, and Lake Kariba can be thought of as the largest battery in the world, with Zesa cutting back day demand to almost zero and letting the day's water ration sit in the lake before a lot of turbines are switched on as darkness falls.
That would make the extension really valuable.
ZESA is already having to be more imaginative over how it runs its power stations.
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Hwange Thermal units, at least the new ones and the rehabilitated ones, need to be almost 24/7 operations to cope with the base load, and Kariba hydro and now the growing inflows of solar used at different times of the day to make up as much of the shortfall as possible.
Wind power is of limited use in Zimbabwe; we do not have the sort of persistent strong winds that you get outside the tropics, and a few hours of gusts do not keep the turbines spinning as high levels.
Natural gas, and the coalbed methane people have been talking about, will help as their carbon footprint is about half that of coal, and the capital costs of a gas power station are a lot lower since such a station does not need water cooling, being basically jet engines in a shed.
But solar has the advantage that you can add bits as money becomes available, literally a panel at a time. Zesa has already invited the commercial sector and better off residential users with their panels to apply for the smart metering so they can sell power to the grid, while some have taken up the offer it is fairly clear that most have not bothered.
Perhaps when they see the Glen View 3 residents having a decent 24/7 power supply at very modest cost, they will understand just how this can work.
