Archive | September 2015

ZESCO and El Nino

As far as I know, that blog I sent last week DID go out, so I am going to keep trying with WordPress and an Airtel Dongle – at least for a while.

Sarah Trou tells me that a group of farmers in Serenje have managed to persuade ZESCO to leave them connected 24/7 in exchange for the solar power that these Serenje farmers are feeding back into the grid. We intend to start discussion on a similar scheme here. If anyone is interested please contact me or Sarah.

I am hoping to invest in 60kW of solar power. If it generates for 8 hours a day, 300 days a year, it would generate all the power that I used in 2014. BUT, I need ZESCO to take my surplus in April May (for instance) and to make it available when I am curing and irrigating in December.

In order to persuade ZESCO to leave ME connected 24/7 I would have to convince them that they would get enough solar power back from the Sibanyati line, to leave us ALL connected. That is going to take more than my 60kW! However, if enough of us (Hennie, Piers, me, Patrick, Kurt, Rob, Southern Bio, Steve) did 50kW each, that would be 400kW and I think we could convince ZESCO to leave us on – they would get more power back from us each day, than we would absorb at night – on average.

The Kalomo/Kala guys and the Namwala Road people would have to come up with a similar proposal. (I cannot do much for you as I don’t know who is connected where, and where the isolation points are. We might have to persuade ZESCO to train somebody at Mbabala to isolate the rest of the Namwala line, according to the load shedding schedule – and at other isolation points.)

At the moment I don’t know what price ZESCO is paying the Serenje scheme. For my 60kW scheme I would be happy to get paid what they charge me, as I doubt that I would have a net surplus for the year. Though obviously if somebody DID have a net surplus of power (from their solar panel system) they would want something higher so we will try to negotiate for something better

Through Mary, I did suggest that we could use a grid-tie inverter to supplement our generators. I am now concerned that a grid-tie inverter may not be able to follow the change in frequency when you switch on a chongololo fan, while on a genny. If anyone had been planning to do this, it might be worthwhile thinking of splitting the load. Put the base load (the chongololo and one or two other things on the generator – the more constant the better) and put the house, borehole and whatever else the PVs can cope with, on your solar panels. Two SEPARATE circuits.

I have yet to meet Wimpi – although I have asked Karen to put me on her list. I think it would be worth our while to get together and discuss our plans as there may be significant savings if we buy our panels (in particular) in bulk,

I mentioned that I had the latest Kariba data and that, at present rates, Kariba would keep going to the end of January. (At present rates Zambia will exceed our allocation of water long before then! I have no idea how THAT is to be resolved.) I also hear that Lance Carr (?) crossed Kariba and the intakes are already causing a vortex. I THINK this CAN be managed – up to a point. The dam is very definitely designed to generate power for another several meters; I imagine if they had all 6 turbines each running at say ¼ capacity, they could deliver the power we need, without the vortex problem….but there could be yet another curved ball there. (In 200XXXX when the lake level WAS much lower, we DID get power out of Kariba, so I don’t expect the lights to go out soon.)

For your interest, the average of the non El Nino years’ rain for my farm was 760mm (as far back as the first El Nino year for which I have records). The average of the EL Nino years is only 600mm (about a 21% drop). If you are interested the years are: 82/3, 86/7, 87/8, 91/2, 94/5, 97/8, 02/3, 04/5, 06/7 and 09/10 and you may want to check through your records to see what is the most likely impact on your farm. I would also look at LENGTH of season, as I suspect that El Ninos start late and finish early.




Solar Power

Dear All,

It has been a long long time since I last attempted to write a Blog because connecting to WordPress was just too frustrating. My Zamtel modem has given up on me, and I am now using an Airtel dongle, which looks as though it might be marginally better. We shall see.

I am making very slow progress with my plans for solar energy. I wonder how other people are getting on? If anyone ever gets the name of somebody in ZESCO who is prepared to discuss Solar Power, please let me know. I am getting nowhere with the MD’s secretary.

I have obtained the latest Kariba levels up to Tuesday 22nd. At this rate Kariba will hit empty (the level at which the turbines no longer generate power) in late January. By then, the rains should pick up the lake levels, so we will get through this season. I fear the news on the Kafue is less good. I was at IteshiTeshi 3 weeks ago and eventually found a Chinese Engineer who could confirm that the power station should be finished by end of November. However, there is a blackboard at the ZESCO office with the river data. IteshiTeshi is only 45m deep; it looks as though it is already down by 7m (so say 38m) and it is losing 8cm a day – so 7.2m by the end of November, or only 31m. I very much doubt that the turbines will have been designed to operate at such a low head – 45m (full) to 31m (expected) is just too wide a range for a water turbine.

And then there is El Nino. I have asked the ZRA (that is Zambezi RIver, not Zambia Revenue) for their historic river flow data….but no reply yet. I obtained a list of El Nino years from a South African weather site and (for my farm) every recent El Nino did result in rainfall considerably lower than my average. If we find the same correlation between El Nino and the inflow into Kariba, then the 2016 problem will be dire.

So we have to keep pushing solar – or diesel, if you prefer to pay 30cents and upwards for each unit of power.