They use high voltage DC between Tasmania and the mainland, but of course this still requires the right voltage in as AC before it is rectified and then has to be 'remodulated' (?) at the other end into AC before distribution.

Not cheap by the sounds of it, but on long runs apparently quite efficient compared to AC transmission.

So, Macro, you are going to need AC somewhere. Even in houses, DC is problematic. Either low voltage and high current, or high voltage and lower current. Switching is going to be a problem, not to mention all the existing transformers and inverters that need 120 or 240VAC.

Going solar does not neccessarily mean pv panels. Try solar heating of thermal sink(oil)as a closed system through heat exchanger to steam turbine again closed system. A large enough oil thermal sink will ensure constant base load generation. barely affected by cloudy days .

Test pilot 1 said...
Going solar does not neccessarily mean pv panels. Try solar heating of thermal sink(oil)as a closed system through heat exchanger to steam turbine again closed system. A large enough oil thermal sink will ensure constant base load generation. barely affected by cloudy days .

That is right but at this moment to convert heat into electricity you need complex mechanical device that is and will be expensive,

Electronic or solid state converters are highly inefficient and used only on space mission that costs and efficiency doesn't matter much

Solar panel could be as cheap as paint on your home soon...

Back in the late 70's the Russians tried harnessing the power of lightning. During construction, the tower to support the lightning rod(2,000 square millimetre woven tinned copper cable) was destroyed 4 times by ... yup you guessed it, lightning. the heat sink was a 200 tonne of Sodium in a sealed electrically and thermally insulated container buried underground under what was to be the steam turbine generation building. The steam was to be generated by a 2 stage heat exchange unit(Sodium/oil, oil/steam) all closed systems. It operated for only 3 months with maximum out put of 15 Megawatts before cattaclysmically self destructing as the thermal expansion was calculated incorrectly(cracks opened in the concrete containment shell of the Sodium vat, and storm water conduits next to the vat ruptured flooding the vat containment. And we all know what happens when you mix water and Sodium. 32 workers and staff died as it occurred during a shift change. Luckily it had been built in an isolated part of Siberia where only bad people are sent(political prisoners)

Macroscien said...

FormulaNova said...

1) Are you forgetting the infrastructure required to deliver this power to the train.

Whole world is running electric trains, specifically because they are cheaper to operate then diesel

Beside there is interesting concept of electric Energy Storage device in the form of Huge Fly Wheel. The same could be achieved by train running at circular route.

As heavy as possible ,fast and the air-dynamic electric train would store energy to smooth fragile Green Power.

Run it in a vaccuum sealed tunnel to lessen air drag losses.
Trouble is unless you stop you can't get on or off

Macroscien said...
No you don't but just in case that you have DC supplied to your home gate you still may have ordinary inverter

If you want to use a standard: aircraft 28Vdc.

Test pilot 1 said...
And we all know what happens when you mix water and Sodium. 32 workers and staff died as it occurred during a shift change. Luckily it had been built in an isolated part of Siberia where only bad people are sent(political prisoners)

Holly crap. We have all heard stories of high school teachers cutting off a bit too much sodium for the sodium experiment. I take it sodium as a excellent conductive coefficient ? :)

FormulaNova said...
They use high voltage DC between Tasmania and the mainland, but of course this still requires the right voltage in as AC before it is rectified and then has to be 'remodulated' (?) at the other end into AC before distribution.

Not cheap by the sounds of it, but on long runs apparently quite efficient compared to AC transmission.

FN, there are two factors here: Distance transmission relies on high voltage to minimise losses. The AC crosses the zero voltage point 50 times per second. The lower the voltage, the more the losses. Each zero-crossing (or in fact, any operation at less than peak voltage) costs efficiency. The second, and bigger factor is capacitive losses. The transmission line to Tassie is most likely "ground return", i.e. a single "wire". So, the conductor in the HV cable, its insulator (dielectric), and the ocean water become one giant capacitor. That's OK with DC - once you charge this capacitor it won't draw any more energy. However, with AC, you just keep recharging this capacitor with each reversal of polarity, 50 times per second. This is very lossy.

These are the reasons why HVDC is more efficient. In the past, conversion from AC to DC and vice versa was costly, and relied on some really weird stuff (mercury arc valves), but it's not a big deal nowadays and can be done with semiconductors.

However, 240 VDC is probably not a good choice for domestic use. It's a lot more dangerous for physiological reasons, and also results in all sorts of stray current (galvanic) problems (e.g. the light bulb fittings will keep corroding all the time).

Macroscien said...

FormulaNova said...
Macro, you are going to need AC somewhere. Even in houses,

No you don't but just in case that you have DC supplied to your home gate you still may have ordinary inverter to run your ablosete AC arterfact devices ...
but most could run on DC alone -LED lights, Universal and Permament Magnet motors, computers etc

The problem with HV transmitting lines is similar to one with imperial units in US.
The longer they stick to gallons the more difficult painful and expensive will be their switch to metric SI units whole world is using.
Some power lines could be turned to HV DC today but the bulk stations and distributors must be eventually replaced.

Macro, I don't think you really understand how power transmission works. High voltage DC transmission? Why? It might make sense if you have a very long run without any taps taken off it, but if you need to feed half the state on the same run, you need AC so you can use step down transformers.

There are a huge number of things in the house that would need to be changed to support DC. Who's going to pay for that, and what benefit do you get?

Computers? The irony is that you would need to turn the DC into AC (again!) in order to run the switchmode power supply.

I am flat out thinking of anything in the home that would be better off running on DC.

You would need to keep the same voltage level as the existing AC in order to keep your cabling size down. Are light switches able to switch the same amount of power in DC as they can in AC? They certainly aren't rated for it, and depending on the current drawn, may get stuck on. Fix that!

Your induction motors are flat out not going to work.

So, tell me again where the benefit to this idea is? DC was suggested originally as the way to transmit power, but there are so many things against it, that its not really economic unless there is a specific requirement that needs DC.

jn1 said...

Test pilot 1 said...
And we all know what happens when you mix water and Sodium. 32 workers and staff died as it occurred during a shift change. Luckily it had been built in an isolated part of Siberia where only bad people are sent(political prisoners)

Holly crap. We have all heard stories of high school teachers cutting off a bit too much sodium for the sodium experiment. I take it sodium as a excellent conductive coefficient ? :)

Yes, but also important are its high heat capacity (at a constant volume) and high boiling point. WWII aircraft engines pioneered the use of sodium-cooled exhaust valves...

BTW, only the best people were sent to Siberia :)

Macroscien said...
240 DC supplied to your home power point, agree could be danger, but there is a petrol in your car that is flammable and combustible and we managed to live with that.
48V on another hand will be extreamaly safe in comparison to existing 240AC.

Macro, do you realise how thick your wiring would have to be to run your tumble drier off 48 VDC?

jn1 said...

d1 said...
Macro, do you realise how thick your wiring would have to be to run your tumble drier off 48 VDC?

Yep, another good point :)

no so because I am not yet convinced that 240V DC in your power point will be lethal.
In such case all your switches and cables will be in better position conduction much lower current
but
sparking and other electrochemical effect may cause the replacement of most infrastructure eventually.
But for new devices build with DC in mind I can't see any barrier..

Macroscien said...

In direct comparison DC at same voltage as AC will be always much safer.

Really? How so? At the same voltage, they should be as lethal as each other.

Please, no claims of aligning pyramids and DC power being 'calming'. I want to hear tangible evidence, not hopeful side-effects.

I think you have a solution searching for a problem. Despite what you hope, AC is more practical.

Macroscien said...

jn1 said...

d1 said...
Macro, do you realise how thick your wiring would have to be to run your tumble drier off 48 VDC?

Yep, another good point :)

One more catch !
All your existing cables are 3 wires but for DC you may need 2 and much thinner.
So there is obvious saving on 240 V DC installation measured in copper.

How do you figure that? Why only 2 wires? Why aren't you going to use an Earth for safety?

Do you realise that the Neutral in most AC systems is bonded to the Earth anyway, and that its mainly there for protection. Why wouldn't you want this same protection in a DC supply?

Why much thinner? If they are passing the same power at the same current, they will use the same diameter cable.

FormulaNova said...

Macroscien said...

jn1 said...

d1 said...
Macro, do you realise how thick your wiring would have to be to run your tumble drier off 48 VDC?

Yep, another good point :)

One more catch !
All your existing cables are 3 wires but for DC you may need 2 and much thinner.
So there is obvious saving on 240 V DC installation measured in copper.

How do you figure that? Why only 2 wires? Why aren't you going to use an Earth for safety?

Do you realise that the Neutral in most AC systems is bonded to the Earth anyway, and that its mainly there for protection. Why wouldn't you want this same protection in a DC supply?

Why much thinner? If they are passing the same power at the same current, they will use the same diameter cable.

Negative in DC wil be Earth anyway. Not sure what for the third cable could be used for ?
For the same power conducted the required current in DC is smaller.