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Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to "Ask SILICON CHIP" and ?Circuit Notebook?.

Electric cars will be the storage element for wind power

I have just finished reading Paul Miskelly’s interesting letter (SC, April 2010) on the consequences of the intermittency of wind generation. I note the work devoted to charting the capacity factor of the interconnected wind farms in South East Australia for the month of January 2010 and seek to extrapolate that data to an annualised value, only for the purposes of illustrating an argument on the value of wind power.

In absence of the real data, allow me to assume that the ratio of kWh supplied to hours of wind generator operation is 25%. That is to say, the same energy would be generated by 25% of the installed capacity were it able to operate at capacity for 24 hours per day. From the charts, that seems about right. Assume one further thing – the use of the editor’s projected $6 billion worth of possible wind generation which I will round out to 2400MW. The approximations in these assumptions do not detract from the matter of principle I present.

With those parameters, now please allow me to refer to Tim Flannery’s comment [i] on the intention by Denmark to use wind-generated electricity to charge batteries for use in a fleet of motor vehicles. The batteries can be charged at parking bays or they may be exchanged at filling stations for recharged units on a plug-in basis.

Tim points out that the myriad of electric-car batteries comprises the storage element so often represented as being unavailable to wind power. He takes it as read that electric cars are inevitable, as would nearly every thinking person, in the light of diminishing oil supplies and exhaust gas pollution from our existing vehicle fleet.

Now the nay-sayers have educated us well as to why this cannot be done. But please allow me the opportunity to spell out how it can!

Assuming that we have 2400MW installed at the assumed annual capacity factor of 25%, we can be assured of 600MW delivery over a full year. So that is the limit for wind power’s contribution to electric-car operation.

The undeniable intermittency of such a supply means that for a guaranteed availability of an exchange battery on demand, we must have a battery stock greater by four times than the total electric-car capacity.

That means that regardless of the energy available to charge batteries at any instant, over the long term, there will be enough fully charged batteries available for use. The method by which this aim is achieved is the same as is used today for management of electricity generation and consumption.

Information about the available capacity for each generator site is integrated at market headquarters and the commensurate rate of battery charging can be communicated by load control technology, available and used currently for many purposes, including off-peak hot water, air-conditioner load limiting and so on. Today’s smart meters all have the capacity to relay the necessary control information to intelligent chargers. Market operator’s seals on the controllers would of course be mandatory.

So there it is – an electric load that uses all the generated power, no matter the instantaneous capacity factor; an electric energy storage system that exactly matches the generation capacity; and replacement of deleterious gaseous emissions from 600MW worth of motor vehicles. The only reason to require back-up of such generation by gas turbines of open or closed cycle types is to cater for loss of a turbine.

Three counters to this argument exist. First, the requirement of four times the base battery capacity implies a cost burden. The effect will not really be known until the real cost has been agreed and/or the cost of doing nothing is realised. Second, the control needed for optimal results cannot readily be achieved for distributed charging installations, such as in one’s garage at home, but the outcomes should justify that shortcoming. And third, my argument has to date ignored current green-power contracts that must be honoured, including those for desalination, but the control information needed for such purposes is all readily available at present and would complicate the algorithms not at all.

Warwick Nichols,
Tea Gardens, NSW.

[i] Tim Flannery, Now or Never, Quarterly Essay Issue 31 2008

Comment: some thinking persons argue that electric cars are far from inevitable as the future of personal transportation. Furthermore, even if electric cars do eventually become commonplace, that will take many years or even decades. In the meantime, there is no effective storage for wind-generated power.

Nor is there any guarantee that all the planned wind power projects will now proceed, following the Australian Labor government’s decision to abort the emissions trading scheme (ETS) and the misnamed Carbon Pollution Reduction Scheme (CPRS).

Plumbers disconnect
house earths

I have recently found two instances (a block of five units and a house) where two different plumbers have disconnected the main earth wire from an effective earthing stake, while re-plumbing older properties.

In the latter case, the plumber has installed copper pipe underground from the water meter to the building, then plastic pipe above ground under the house and connected this to the existing copper pipe from sinks etc. The existing earth wire has been transferred from the previous steel pipe to the copper pipe from the sinks, leaving a gap of 5-10 metres to the underground copper pipe. And the wire was just twisted around the copper pipe.

Both plumbers were older, very experienced men who regularly do re-plumbing, so there are likely to be many houses with ineffective earth connections. Fortunately, no accidents have occurred in the 12-18 months since the work was done.

If an older house has been re-plumbed, then I suggest that the owner does the following:

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