The solar (dis)advantage

9 06 2011

There is something appealing to being able to generate one’s own electricity – especially in Zimbabwe where I thoroughly resent the attitude of the supply authority, ZESA, who seems to turn off the power at a whim and shows precious little interest in upgrading the grid. So it was with more than a passing interest that I asked about the solar panels at my local electrical hardware outlet this afternoon.

The largest costs US$750 and puts out 150W.
In Zimbabwe we pay around 10c a unit (kWh) for our supplied electricity. $750 would thus buy 7500 units.
The solar panel could theoretically put out 1.35 units a day (8 hours of usable sunshine x 150W).
It would take 6944 days at this rate to equal the 7500 units of ZESA supplied power. This is assuming an 80% efficiency conversion to mains power through a battery and inverter; which might be optimistic. (I don’t know if the panel requires full sunshine incident at 90 degrees to generate the 150W).
Now the salesman said the lifetime of the panel should be around 25 years. 6944 days is 19.29 years if the sun shines for 8h every day which of course it doesn’t. Nor have I included the price of a deep cycle battery (around $200) or the inverter (about $150). Do that and the payback period jumps to 28.29 years. And the battery will need to be replaced at least every 5 years! Factor in the replacement batteries and it would take around 49 years to pay back the investment to the equivalent of $750 of the grid electricity.

Why bother?

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19 responses

10 06 2011
goneXC

Alternatively one can work out the approximate cost of the power output by the panel over it’s expected lifetime of 25 years: 25.9c per kWh!

10 06 2011
Big Blister

Discouraging. If it won’t pay in the land of sunshine, how would it work in more temperate zones?

12 06 2011
goneXC

It will only work when the conversion of light to power gets more efficient. It is around 19% in commerical panels now. In the lab it as high as 40% but costs $10,000 a square mm! Quantum dots are the most efficient but no-one is too sure how they work. If you want to buy a panel I’m told Germany has the cheapest because they are heavily subsidised.

10 06 2011
Tuppit

We have just hired machines to a firm who put up a £250,000 wind turbine on a farm near here which they said would pay for itself in about 7 or 8 years as well as supplying free power to the owner.. The grid guarantee to buy excess power index linked for 20 years, the current rate is about 20p/unit. Apparently manufactured in Canada, this one had three 9m blades, obviously smaller versions are available.

16 06 2011
goneXC

Efficiency increases with size which is why they like to keep them big if possible. There is the reamains of a mini “wind farm” of very small turbines on the road from Rusape to Nyanga at a business centre and a friend of mine made the blades of the turbines years back. Every time I go past I check to see how many are still working. They all appear to be seized now.

12 06 2011
Frazer

You have a dog:
dog + treadmill + generator = solution

I know, I’m a genius, why aren’t I going to Oxford? 😉

12 06 2011
goneXC

Wrong type of dog. Therefore you will be going to Nottingham Uni.

17 06 2011
Frazer

Ridgebacks can run can’t they? And hey, there’s nothing wrong with Nottingham, minus the slightly above average levels of gun crime. Too much literature at Oxford anyway…

23 06 2011
goneXC

Ridgebacks are selective about what they chase. They were tried for racing but worked out that it was only a piece of rag and not a rabbit and if you went the other way around the track it could be nailed as it came past. I don’t think a treadmill would find much favour!

12 06 2011
La Canadienne

You omitted the ‘reliability’ factor cost, as demonstrated by the relief that you feel, when you have electricity when you need it, for cooking, laundry, computer work, etc. You have to pay for that peace of mind. So, how much would you pay to have electricity ‘on tap’, as it were?

How much do you think ZESA would cost if the equipment were renewed, as must be the case? How much do you think ZESA would cost if electricity were sold at a commercially viable cost; not a ‘for profit’ cost, but a reasonable cost to the consumer from an organization which is not profit oriented, but is tasked to provide a service at an efficient rate.

In Ontario there are 3 cost layers; off-peak,(5.9c/kWh); mid-peak, (8.9c/kWh); on-peak (10.7c/kWh). This will only increase, in fact by 12% as of October this year. And this increase is predicated on the fact that, after years of doddering and neglect, the entire electricity provision system will have to be renewed.

Go for it…what’s your peace of mind worth to you?

16 06 2011
goneXC

I am surprised at how cheap your power is but then I think a lot is hydro which of course is cheap to run once the dams are in.

Our power infrastructure is in such a mess it would take a lot to get back to where it should be. The country simply could not afford to pay back the investment without getting an economy going – bit of a chicken and egg situation. I saw in a recent Economist article that Zimbabwe has the world’s second worst performing economy just ahead of … wait for it. Drum roll here. Haiti!

I would prefer to put the peace of mind investment into some good quality cabernet/shiraz. Instant gratification!

17 06 2011
La Canadienne

hi, I don’t feel our elec is cheap; that’s the cost per kWh, then there is the ‘delivery charge’ added to the bill. Our electricity bill is approximately $275 a month, which I feel is really high. We use elec for light, cooker, laundry, air con, and general uses. We are careful, and don’t forget there are only 2 of us in the house most of the time.

Totally agree on the cab/sauv or shiraz…or both.

14 06 2011
Big Blister

Recently talked with a fellow who is opposing wind turbines in his area (Arizona) because:
1 – the wind is not consistent enough for them to be economic and (coal) power stations are still needed to provide a constant power source 2 – they are horribly noisy 3- they reduce property value i.e. it becomes unsellable 4 – the companies are a scam, they come in (from foreign countires), take govt subisdies, go bankrupt & leave the turbines for the landowner to deal with, then return as a new company under a new name….
See http://illwind.co.uk/default.aspx for a situation in the UK

14 06 2011
Big Blister

Re La Canadienne: The coal power stations up and running provide peace of mind…!

14 06 2011
La Canadienne

Agreed Big Blister. The wind farms are not received enthusiastically in Canada, principally for the noise reason. Though the gov’t of Ontario has just granted an extrememly lucrative deal to MARUBENI a Japanese firm, which will invest in ‘for profit’ wind farms.

Coal powered stations might well be the way forward; in Nova Scotia, there was work to liquify coal so that it could be used in a more environmentally friendly manner==less smoke etc.

Re peace of mind, I was just hectoring Andy who only ever see things in $ and cents…not in the lack of stress that electricity when you need it, can bring you.

16 06 2011
goneXC

When coal fired power stations have left their legacy of environmental damage I will be long gone – which remindsme; I must change my will to state that I want to be buried and not cremated which will release too much CO2.

Sadly power storage is not at the stage where it is capable of running high current usage devices such as cooking. In fact that is oneof its major disadvantages – what to do overnight? Wind is not reliable enough in Zim to use for power generation. I cannot think why the turbines cannot be made quieter and, anyway, people are prepared to put up with city noises so why cannot they put up with turbine noise? It seems a small price to pay for future peace of mind!

18 06 2011
Big Blister

The argument in favour of coal power plants (for plug-in electric cars) is they are Point Source pollution and thus easier to regulate and clean up than millions of petroleum-using vehicles. There are ideas like pumping the CO2 produced deep into holes in the ground where it will? remain frozen solid….

Wind turbines noise is pretty loud. >100 db if I remember rightly. The blades move at 100 mph so I don’t know how one dampens that. They are also tough on birds.

Hydro power is no longer considered “green” here because of its effect on migratory salmom. Tho most of the people who claim to be pro-salmon mostly want more of them to kill and eat!

All a most interesting topic…

28 09 2011
doc.

1st of all u got ur calculations twisted cz u ddnt include e factor of hw many run hours u hv on 2 12Vbatts for a 1200Winverter wch z approx8hrs & wn u consider dat w an inverter u dont connect items lyk geysers, stoves,microwaves,heaters,etc.u also get to connect energy saver lamps wch only consume 11W per bulb.No sunshine?hv a backup generatr-charge ur batts only for jus a few hrs.Cooking factor?-use gas..tz way mch cheaper!e reason zesa z so high z bcz o da items we use.thnk on it!inquire!

15 10 2011
goneXC

In a communique recently, the chairman of ZESA, Richard Maasdorp suggested that all duties be lifted on photovoltaic panels and solar heaters to reduce the demand on mains electricity (there was a lot more to the communique than this). I have to wonder to what extent this would make PV generated electricity cheaper? It appears to be much cheaper in the USA (see http://www.economist.com/node/21532279) but in the Economist article it does not say if they have factored in storage and inverter costs.

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