Future Energy Sources 1.4 Wind Power

Hi discussion partners,

there are some misunderstandings or missing information:

High voltage transmission is costly in installation but low in losses.

You would not use a big train or airplane for one passenger only, similar situation with high voltage transmission.

Synchronous generators and motors are suitable for any speed: at twice the speed it will generate twice the frequency and twice the voltage.

Only in old times with no power electronics available there was a need for constant speed.

In big power plants the turbines have to run at high speed so the frequency is selected to be locked in frequency and phase to the existing electrical net.

Turbines are efficient only near their maximum speed.

Generating DC with wind-turbine driven generatos ia not a good idea as DC generators (as DC motors) have to have "collectors" to mechanically switch the voltage to reversed polarity if voltage is below zero.

So wind-turbines have to generate AC with variable amplitude and this converted to DC by simple rectificatiun. (As in a cars generator where the diodes for rectification are built into the generator.) This is generating DC with windspeed dependent voltage which is difficult to use: dictating constant speed and very bad efficiency.

So more modern installations use an additional inverter that is an electronic switch operating at frequencies between 10 and 100KHz switching the + rail of the DC for a very short time to one rail of the AC output, as the voltage there is raising more slowly as the switching speed because of inductance in the switching path. The sine AC voltage output is made by changing the on time of the switch. In the 10 milliseconds of the half wave of european 50Hz a 10KHz inverter is thus switched on and off 10times. On is commanded if the voltage has dropped slightly below the momentary voltage according to the sine waveform, off is commanded if the voltage has risen a little above. The negative is switched in the same manner to the other wire of the AC output.

In the negative half of the cycle the same +DC and -DC are switched to the other wires of the AC output.

If three phase are to be generated this is existing three times for the three phases.

Look into some book on power electronics or inverters or into google or wiki to find a better explanation.

This AC can be made to have any voltage, fequency and phase as realised in modern 3phase generators for feeding asynchronous or synchronous motors.

So many obstacles are blown away with the winds by our engineering skills but some principle drawbacks remain.

So I would build my own wind generator (or buy one) if I have to live high in the mountain or out in the desert or at an unaccessible seaside.

But near an existing power net this is waste of money and time.

RHABE

Rhabe,

Your explication is a quite decent technical explication of one of the solutions.

Frankly said, it is the modern "high tech" WOW.

The efficacy is low but the price and maintenance costs are also low.

A better way to describe the synchrone generator working at variable speed is a brushless DC generator. (inverse of the brushless DC motor) There are some technical differences but they are minor and more in the details.

A more effective way to couple the power from a variable speed generation system to the grid is the combination motor - generator. It delivers the best efficacy but is costly and only used for high powers or where the quality of the result needs to be high (certified labs that need to test 60 or 400Hz appliances). Somewhere between the electronic inverter and the this system is the asynchrone generator which is also used in windmill applications.

Big generators do have brushes, to feed the electric magnets in the rotor. This is a better way to control the output of the machine.

All these conversions cost energy, thus CO₂ production that could be avoided. Even a rectifier takes a nice part of the losses.

I agree on the grid coupled generator from the moment that we avoided all the other stupid applications of oil and coal. These are the first fossil fuels that should be kicked out of the system. But at the moment the big distribution networks are not designed to distribute energy as windmills require. They are designed to capture local temporary shorts. If tomorrow we need to deal with the possibility to generate power for Europe along the coasts or on the highlands, we will have to build a lot of extra transmission lines. Until the moment that this infrastructure is finished we have to install windmills for other purposes.

We could also decide to do none of all the needed things because the other one is not there.

Gwen

GM1964 in post #101 you asked;

But is it feasable/ likely that enough power will be produced in one neighbourhood to supply all their needs, and still export to other areas?

If only the occasional building used co-generation then I would doubt that any energy would feed back through step down transformers and into the distribution system. However if every house had a co-generation system than yes the surplus would feed back onto the distribution system for use in areas that had a shortfall. The great thing about the concept of multi technology multi user co-generation is that all the technology already exists and for most part the existing power distribution system would be adequate to transfer surplus capacity in one area to the areas that have a deficit.

The more diverse the technologies and locations the better and more reliable the system becomes.

In response to RHABE statement in post #102 where he stated;

But near an existing power net this is waste of money and time.

This is only true it you are not talking about co-generation where surplus capacity is sold over the power distribution network. Thus you not only decrease the amount of electricity you purchase but also get a credit for the surplus that further reduces the amount you pay for electricity. A large enough co-generation system could actually be a profit generating item.

The system that is offered by Origin Energy in Australia, that I referred to in an earlier post, uses solar panels to co-generate electricity. There is no reason however, the same technology couldn't be used in conjunction with a wing turbine, micro hydroelectric unit or hamsters in a tread mill it you are so inclined.

It depends on the broad mindedness of the local authorities and if encouraged there is no technical reason that co-generation couldn't be used by nearly every electricity consumer. The more forward thinking authorities are actually offering subsidies for people to install co-generation systems so if it can work in Australia why not everywhere?

Under which main topic did you place the hamster in a treadmill?

This is the big solution, every kid want's a hamster, millions of hamster all over the country, driving the everwatt generator.

Should I try to file this?

Hi masu,

The link you provided tends to show that my statements were correct, as the examples given of 1kW of solar panels for a demand of 3.5kW (I assume the figures are rounded to the nearest 0.5kW), suggest that the occupant will never produce enough power for himself, let alone exporting outwith the neighbourhood.

In the UK, there is a company making solar roof tiles, but seem to have missed a trick by selling them by the area of panel required at full output to meet hopusehold needs, rather than to cover the entire roof, which would even look better than the patched-up result:

http://www.solarcentury.com/products/solar_photovoltaics/c21e_solar_electric_roof_tile_black

Those solar tiles are great, but way to expensive to cover the whole roof.

Marketing plans and prices buildup of those firms are a bit different than compaired with automotive. They charge a lot for the "green" aspect and the fact that you can harvest energy with it.

If govenments would legislate that all new houses were to have these fitted as standard, then mass production would be ensured - look at cavity wall insulation and double glazing - and remember, these fit instead of the standard tiles, not on top as before, so some of the cost is offset compared with retro-fit units.

Switserland is doing this.

As soon as you build a roof of a certain size, you need to do something with the surface.

As usual, the rest is a bit slower and Belgium is the worst in class. But we do have great chocolats.

Are there possibilities to suggest these kind of legislations in the EU?

"The link you provided tends to show that my statements were correct, as the examples given of 1kW of solar panels for a demand of 3.5kW (I assume the figures are rounded to the nearest 0.5kW), suggest that the occupant will never produce enough power for himself, let alone exporting outwith the neighbourhood."

You are misinterpreting what the link says. The link states that your total energy usage will drop from 4,500 Kwh to 3,000 Kwh not from 4,500 watts to 3,000 watts. You are forgetting about the time factor.

If you consumed 4,500 Kwh or energy over a period of 12 months your average consumption would be just over 500 watts. With a 1,000 watt solar panel that operates during daylight hours you would have a surplus capacity of 500 w then at night a deficit of 500 watts. The result would be that you would be energy neutral over the entire year.

This is a simplified explanation but hopefully you get the picture,

Under which main topic did you place the hamster in a treadmill?

This is the big solution, every kid want's a hamster, millions of hamster all over the country, driving the everwatt generator.

It was an idea that I remembered from a MAD comic that I read as a school boy. If you use it though make sure that you don't put male and female hamsters in the same treadmill. Failure to observe this safety procedure will result in an out of control runaway generator and millions of hamsters.

Hi masu, I apologise - the figures are somewhat confusing $4,000, 4,500kg, 4,500kWh,.........and that's just 4 lines!

Did you notice that this works out at an average of 4.1kWh per day - I presume this will be more in summer/less in winter, but as the user pays more for electricity coming in than for exportI'm not sure the figures add up quite so nicely.

Did you notice that this works out at an average of 4.1kWh per day - I presume this will be more in summer/less in winter, but as the user pays more for electricity coming in than for exportI'm not sure the figures add up quite so nicely.

I just chose the year as an example. The billing cycle is usually over a 3 month period so if we do the calculations again and use a quarter of a year then

Power_Average = 4,500 KwH ÷ 2,190 H ≈ 2 Kw

So we would therefore halve our energy consumption during the day and that would reduce our total energy consumption by 25% therefore 4,500 KwH will be reduced to 3,375 KwH.

That's not that far out from the stated figures but it doesn't allow for an uneven demand so the figures they claim are probably quite possible.

Hamsters are good .., how about a higher output system ... cat and dog pairs. Both systems are organic and "renewable".

All joking aside, Austin, Texas, USA is an interesting study of wind, hydo, and steam generation. There is also some solar cogeneration (private and public). This grid system is under the Austin city Utilities (government), if I remember correctly.

Why should you try to store electricity?

It is one of the most uneconomical and environmental unfriendly things to do.

Look for what you need most of the energy in your house? Heat. Storing heat is not that difficult. All you need is an insulated water tank.

You are right on selling the excess to the grid. In case that the excess can't be used for anything else.

In case you locally need to have more electricity, co generation is the best way to go. Nice experiments and actions are taking place: http://www.cogen.org/index.htm

Up here we need to avoid every kg of CO₂. We are not yet in a situation that we have an excess of wind energy to start distributing it over the continent. We can win more by reducing local losses and local CO₂ generation and let the big electricity producers do their job at the best efficacy.

Avoiding the use of oil for heating purpose will save more CO₂ than starting immense projects to have large scale off shore wind parks connected to the grid.

Moving the CO₂ reduction effort from the community to the user will generate a larger acceptance base. If people feel that they have to pay less for their heating they will accept that large windmills are placed on locations short to the grid, making them more economical. Now we have the tendency to look for places where they are not seen.

Several points:

In the 1960s power transformer efficiencies were above 98%. I have no idea what it is today, but I would guess above 99%.

These transformers are bi-directional.

There may be many (more than 4) levels of voltage over the total "distribution network" from the EHV "backbone" to the end user.

Similarly, there are multiple steps between the generators and the "backbone" depending on the output voltage of the specific generator.

Reduction of CO2 emissions is an important "regional" issue, that can only be understood and resolved "locally". The issue of where "best use" of any particular energy input is not always an easy "nut to crack". But if wind results in local power excess ... obviously if can be sold to the rest of the network.

Volvo has been building high powered variable displacement motors/pumps for power machinery that handle very high torque and can provide continuously variable transmission (CVT) ... variable speed in fixed speed out, This might be a good match for certain windmill installations ... for what it is worth!

Finally, cogeneration occurs quite often in the USA. Generally, the pricing does not favor the cogenerator ... from the little I have heard/read (at least here in the USA).