Maoraigh wrote:
I assume the megawatts of electricity from wind generators will lead to a lowering of atmospheric temperature. Air has a low energy capacity compared to water. Or has conservation of energy now been disproved
I follow your reasoning. On the other hand all that energy will ultimately be dissipated as heat which will warm the atmosphere, with the exception of energy used to power lightbulbs that emit frequencies of light that pass through the atmosphere without being absorbed. The net effect should be roughly neutral.
If you try googling ‘wind turbines atmospheric temperature’ you will find a Scientific American article.
What point were you making?
Shorrick_Mk2 wrote:
For solar being “utterly incapable of serving the grid” it certainly seems to work so well that utilities lobby against feed-in tariffs…
For a short explanation of active and reactive power, see here for instance.The basic principle is that voltage and current has to be in phase within a certain range, or there will be impossible to extract power from the grid (Power = current * voltage). You need synchronous generators to produce reactive power. This is one of the reasons the utilities don’t want feed in tariff. The other is of course they want to sell you electricity, not purchase low quality “junk” that disturbs the grid more than it help (freeloading on reactive power and frequency and spitting out voltage spikes). When you have surplus energy, it’s highly likely that everyone else also have surplus energy (including the utilities), so in these circumstances you should also do as the utilities, namely pay to get rid of your surplus energy, but i bet very few are interested in that 
IMO the best choice for a household is to stay as independent as possible, only using the grid to supply peek power when needed. With solar (PV cells on your roof) and a battery capacity for a day or two, it’s possible to do that. That’s how remote cottages and cabins here have used for ages already, only with 12V DC internal grid in the cabin, used for lighting and electronic appliances.
It is possible to have a DC motor (or an asynchronous motor) directly coupled to a synchronous generator that again is coupled to the grid. This would satisfy the utilities, except for frequency control. But the price of such a thing would be phenomenal, it wouldn’t pay off in 1000 years for the microscopic energy transfers to/from a single house. Therefore power electronics is used, giving good enough quality inside a house, but not even remotely good enough for the grid. Micro hydro powerplants typically use asynchronous motors directly coupled to the grid. But they offer no frequency control and does not help with reactive power. At any time there is always a farmer somewhere in the local media complaining that the utilities don’t want to pay for “his” electricity.
It’s rather funny actually. The power grids are the most complex, largest, most finely tuned, most efficient, most tobust, most expensive human made things ever made. A modern society would be unthinkable without them. Yet people are completely oblivious to how they work. If you mention the quality of the electricity on the grid, people usually go “say what? electricity is electricity”. Power grids have zero sex appeal I guess
Shorrick_Mk2 wrote:
W regards to your engine analogy – how “expensive and efficient” is it to have CCGTs stand by to pick up load spikes and provide “reactive power”? It’s exactly the same thing.
I agree. It’s not very efficient as such. However, even when not producing any power, or at reduced production, it’s stabilizing effect on the grid is needed and valuable, much more so than the junk electricity from DC-AC converters. Which is the basic bite yourself in the tail problem here. The more junk electricity injected into the grid, the more stabilizing effort is needed for the grid not to collapse. A CCGT on “standby” is not a total waste by any means, but it’s far from an ideal solution (simpler and less efficient turbines are perhaps better in this respect? I would guess at least). This is why, IMO, battery technology will revolutionize the grid. Every house can be self sufficient for one. The other thing is that grid stability and on demand power surges, which is what cost money essentially, will be better and cheaper. In short, it enables solar and wind energy to be collected and stored.
A few days ago I went to a presentation on electric vehicles and related technologies, by a guy who is very involved in the technology.
There was nothing in it which would shock anyone with a half decent engineering education, but it makes one ask the question: what are some people smoking? Going all-electric is sooo far away from being even remotely feasible.
One small snippet, from one owner who was present, is that a Tesla car charged from a mains socket needs a 1hr charge to travel 7 miles. So these cars are not even remotely viable without powerful chargers – 3 phase in most scenarios. And if you put four Teslas in the average street, the transformer at the end of the street will be fully loaded. He reckons the EU will have to spend €40BN/year just on upgrading all this stuff and that’s before you get to the extra power stations.
A 40 ton truck needs to carry of the order of 50% of that weight in batteries and needs megawatts to charge it. Not going to happen.
So I just don’t see electric planes are more than grant milking projects.
I have gone all electric for my road transport 3.5 years ago. Not sure what I am smoking but it works.
Nobody says that every car will be electric as of Jan 1st, 2018.
I am all electric and others, too. Now 4 people in my street are.
People were making similar remarks about the first cars and betting on horses. Lots of smart and obvious reasons. Took about 20 years to replace horse carriages entirely.
Electric airplanes are feasible.
The points in that report are however specific. You have four people in your street with cars of a reasonably long range and larger size and charging them from mains sockets and getting 200 miles range after 1 night, etc? That would defy physics. General statements will always work because one might be talking about a tiny car with no working heater or aircon and being used for 10 miles, twice a week, or whatever, and plugged into the mains all the rest of the time.
Statistics apply with a reasonably large number of samples. A street is a reasonably large number of samples. The average car trip in Germany is 38km I read the other day.
I don’t see anything defying physics. Nobody expects the whole street to go all electric over night. Germany gives tax incentives to allow employees to charge their cars at the workplace. Commercial areas have a lot of spare capacity in the grid. Autobahns are getting a dense network of high power DC charging stations (50kW-150kW) which is not difficult to do.
Tesla cars are not for the wider public. They are high end cars with huge consumption sold for a lot of money. It’s for early adopters where money is no object. A 2.2t car for $140k is not the future of the automobile.
Don’t underestimate progress and don’t try to predict the future by extrapolating what we are doing today.
I know plenty of people with Teslas. They seem to work well particularly if you live in a city or suburbs and can charge at home. Like it or not, it is the future.
It isn’t a matter of me liking it or not. It’s basic physics.
What size chargers are they using and are they single or three phase?
An aircraft would need a charger at least as big, because the power delivery to the prop is pretty well constant.
achimha wrote:
Took about 20 years to replace horse carriages entirely.
Actually it took less than 10 years in the cities.
Peter wrote:
One small snippet, from one owner who was present, is that a Tesla car charged from a mains socket needs a 1hr charge to travel 7 miles. So these cars are not even remotely viable without powerful chargers – 3 phase in most scenarios
Sorry, but this only shows you have no clue what you are talking about. 95% of the driving an average person do in a day is less than 100 km. You don’t need a large battery for that, and if you have a large battery, it only means you don’t need to charge every night. There are fast chargers everywhere now, but compared to gasoline stations, they are only used 5% as much, because people charge at home and/or work using slow 10-16 A ordinary outlets single phase.
I have been driving electric for more than 3 years now. I will never go back to gasoline/diesel. The age of the gasoline/diesel powered private transport is over. It’s as simple as that, and something much better has taken over.
For aircraft, who knows what is going to happen. Money rules, and the moment someone makes something that makes the airlines can cut prices, it will take over in a moment. Commuter traffic, local airline stuff, an hour or so flight, there is no reason that couldn’t be done with electric aircraft. Private GA, who cares? As long as someone buys electric aircraft, they will be made. If it doesn’t fit you, then don’t get one.
I seem to have discovered a new way of encrypting PDFs. It is read only by those who need to know but requires no keys. Post a link to them on EuroGA! 
