Geothermal Questions and Answers

Below is a record from this field trip of the questions posed by students and the answers provided by Donald the LEARNZ Teacher and Experts from DoC. All field trips have an Ask-an-Expert Web discussion board for this purpose. A month after the field trip, the Web Board is closed and the questions and answers are archived by being moved to this web page.

1. How much electricity is generated by geothermal? What about other methods?

A good question - because the numbers alone tell the story. The NZ percentages for the year ending March 2005 are below.
Hydro 64%
Gas 16%
Geothermal 6%
Wind 1%
Coal 10%
Other 3% (including cogeneration)

2. Why do you earth everything as well as disconnect it all when working on stuff?

Its always safety first.

What you have mentioned is especially so in places like switchyards. A length of wire, fence, ladder, flight of metal stairs can have a lethal voltage induced in them simply by being near a power station or switchyard.

Remember these places (power stations, switchyards) have strong magnetic fields around them. So you can end up with a length of metal in a magnetic field –that means if anything moves current can be induced, just like in a generator.

By earthing everything any current will flow to the earth mat underneath the power station through the earthing connection you have made, rather than going through you.

Donald :-)

3. Does Contact Energy do other types of generation?

Yes. Of Contact’s generation
50% is by Thermal plants (eg burning natural gas or oils)
35% is by Hydro
15% is by Geothermal

Donald :-)

4. Donald - What IS silica?

Hi Gael
Silica is the element Silicon connected to two oxygen atoms. Its formula is SiO2 (2 should be smaller and subscript). It's chemical name is Silicon dioxide.

59% of the mass of the Earth's crust is silica.
Silica is the main constituent of more than 95 percent of the known rocks. The most abundant form of silica is as the mineral quartz.
Sand is almost pure quartz or silica

Hope this helps
Donald :-)

5. Haywards clothing

When Donald went on the National grid field trip last year he had to wear flame proof overalls with plastic zips inside the substation. Do you have to do this at Wairakei? The voltage is still 200KV correct?

Ben W

Hi Ben
Yes its still 220KV because both Haywards and Wairakei substations are on the same national grid.

This means the rules are the same because 220KV behaves the same in both places. However in the steam field this clothing is not required but hard hats, hi vis vests, long sleeves and long trousers are because the pipes and fittings can be very hot.

Donald :-)

6. Last time you went into the switchyard. Why not this time?


Nice spotting of the difference. You have been reading this diary I think:

Last year we went into the switchyard because work was being done and we could get a closer look at HOW it was being done. This time we followed the electricity from the other side of the safety fence and did not need to get so close. If you don't really need to go in the switchyard, then don't. It is quite intimidating place I found.

Also we wanted to look more at the environmental effects of silica this year.

It is really a case of ' So many good stories to tell- but so little time'.

Donald :-)