Rants, Raves, Reviews

Wind Turbine micro power generation

By Gary R, in , posted: 28-Jun-2007 19:15

I read with interest on the Herald that Vector are trialling the Swift Rooftop Wind Turbine for the purpose of micro power generation. This is a great idea, living in windy Wellington we have plenty of the old puff going around to keep a micro turbine happily spinning.

As with anything green the Swift turbine comes at a cost. No figures are quoted in the Herald but looking around the web I have found some UK prices which I have converted to NZD.

Turbine - $9,200.00
Installation - $5000.00

this is a total investment of $14,200.00

Essentially you have this turbine installed and plug it into the electricity grid. When there is enough wind the power generated is put back into the grid which turns your power meter backwards therefore reducing the amount you pay each month to your local SOE power retailer. Not only that but the turbine saves around 1.3tonnes in carbon emissions per year which is equivalent to 1.3 carbon credits.

Apparently the turbine generates around 2000-3000KWh per year of electricity and this is where I start to have problems with the Math. The Herald article says that the average NZ home consumes 8000kWh per year which is around 666kWh per month. At .174 cents per kWh the average monthly bill for consumed power should be $154.00, this includes the .70 cents per day 'supply charge' and of course GST. The thing is I don't ever recall receiving a power bill this low, even in Summer.

Calculating the return on the Swift Turbine is tricky. Lets face it you are not investing $14,000 because you love the planet (unless you are a greenie) you are investing to pay your SOE retailer less money every month.

The life of the turbine is only 20 years, which probably means putting up a new unit in 20 years time. Looking at it this way:

$14,000 investment / 20 years = $700 per year it is costing you to be green
2,500KWh (average generation) @ .17 cents (plus GST) p/kWh = $478.00 (inc GST) p/year saved
1 Carbon Credit @ $50 (approx) brings the annual saving up to $528.00 p/year saved (assuming you can claim 1 carbon credit)

This means that the pay back period is 26.5 years or 6.5 years longer than the life of the turbine or so you would think, but you also need to consider this:

I have made some inquiries and I have been told that the power you generate is sold back to the grid at 5cents per kWh. Thats right you pay .17cents (plus GST) per kWh but you only receive 5cents or 3.82 times less than you pay. This makes the return on investment pay back much worse, like another 53.5 years worse.

It is no good installing these sort of systems just so you can feel all tree hugging, earth mother good about yourself, there needs to be a financial incentive. I have a few suggestions on what would make it more viable:

1. Government subsidy on purchase or installation, a set dollar kick back
2. Interest free government loans towards the purchase (hey we give money to the students for free)
3. Lower cost turbine. I only based my estimate of the price of a direct conversion for pounds to NZD, so they might be cheaper than what I think
4. Some other sort of other annual kick back from the government to acknowledge your reduced carbon emissions and general greenness. Lets face it the more power we generate ourselves the less coal gets burnt or the less we have to rely on fickle hydro lake levels and the less $1b power plants we need to build.
5. Parity on the price you pay for usage of kWh's and the amount you receive for generation of kWh's.

I think generating my own power is a great idea but the pay back period and the numbers need to stack up. I hope I am truly wrong on only receiving 5cents p/kWh back but then you have to consider that you buy power off a retailer who gets it at the wholesale rate which currently has just increased to 8cents p/kWh on the back of lower Hydro lake levels.

For this to fly the pay back period needs to be 3 to 5 years. The problem I see with this theory is that the current Labour government would probably take the money you earn from generating electricity off you and make you put it into KiwiSaver. That's the problem apparently, if we have spare cash we spend it.

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Comment by Grant17, on 28-Jun-2007 19:45

Thanks for that analysis Jama, it's very interesting.

My wife heard the item on TV One news tonight and was under the impression that the turbine cost $2000 to $3000 rather than generating 2000 to 3000kWh...

I thought it was too good to be true.  And the disparity between cost for consumed power units vs price paid for generated units is totally unfair too.  How can the power companies get away with this sort of rookery?

The consumed/generated price disparity has been argued against by alternative power proponents for years and years, yet it seems nothing has been done to address this issue.

Jeanette Fitzsimons for PM!!! 

(I was only joking, honest).

Comment by Mattnzl, on 29-Jun-2007 07:31

There is a letter in today's Herald from someone in the UK saying that the turbines have been a complete failure in the there (generating nowhere near 2000KWh per year).

The price is outrageous anyway. If you want a turbine just get a nice Chinese one off trademe for 1/10th the price :-)

Comment by sbiddle, on 29-Jun-2007 11:18

Imagine the noise when everybody installs one! At the end of the day the power companies don't actually want you to buy one of these since they would lose out! :-)

Rather than trying this PR rubbish IMHO the government should be focussing on solar heating for houses. Many people in NZ could provide all of their hot water needs for around 4-6 months of the year with a typical unit. Why aren't the government out subsidising installation costs by 50%?

Comment by FredG, on 24-Jul-2007 10:46

Hi, Jama
Thanks for your analysis, but I am confusing on
some of your words. As you said the powermeter will be backward when power put back into the grid. Also you said those monopolies will just pay 5 cents/KW for purchasing from homeholders.
How do they know the amount of putback by extra power? Can they read on the powermeter?
Or you mean there will be two powermeters one for counting consumption and the other for generation?

"I have made some inquiries and I have been told that the power you generate is sold back to the grid at 5cents per kWh."
May I share these info you have got?

Author's note by Jama, on 24-Jul-2007 17:06

Hi Fred - well that is the problem. At the moment if you 'plugged into the grid' the meter would spin backwards at the same rate as the forward spin. The power company would have to guess how much excess power you have generated based on your past average usage. Not exactly a scientific method.

Comment by FredG, on 25-Jul-2007 11:21

Hi Jama

I just read a story about a Chinese engineer installed a set of hybrid system (3KW) on the roof of his house in Shanghai. one of his problem is his original powermeter can run one way only.

I also got an email from Ablesolar
"If you are a power producer of electricity you are typically required to
install a second net-meter. Any generation produced is clocked at wholesale rates. Any power you consume off the grid is still charged at normal tarrif. Normal tarrif used is @ 20 cents/ unit. Wholesale generation is 3 cents/ unit."

Author's note by Jama, on 25-Jul-2007 14:28

That is good feedback Fred, thanks for sharing it.

Comment by geedee green, on 6-Oct-2007 15:10

Hi Jama,

Methinks the economy is even worse than you portray. You have not included the income lost by diverting a large capital sum from bank deposits - at 8% $14,000 earns $1120 gross per year - or from repaying a mortgage.

Comment by Dave, on 11-Oct-2007 10:43

Interesting, I have been looking at wind turbines,

price indication of $18000 best I found for tubine and installation.

The total cost for full turbine/solar supply $85,000+

Unfortunately we have gone down the Power distributor track, but still looking for turbine and hydra/solar power.

Great solution for power supply but price still overcosted hopefully future will reduce this.

Any good products / supplies whould be appreciated.

Comment by Leyland Benson, on 1-May-2008 12:40

My understanding is that you are charged for the net energy you use during the billing period at now 20ish c/unit so if you feed back more than you use you pay nothing for you energy but get 5c/unit for what you supply to the network. Calculate savings at retail and any bonuses from over generation at wholesale.

Most effective cost saver is probably solar hot water, my break even in Auckland was about 6 years.

In high sunshine areas solar could work all year round.

The book "The Sustainable House" detailed a house in Sydney which with solar hot water and photovoltaic cells and inverter generated more than they used.

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