It was very interesting and some good ideas. The bit I dont understand is the obsession with wind power and not tidal power given that we live on a island with some of the biggest tidal ranges in the world.
I have been involved with prototype wind and tidal blades for 25 years . Not too many sites in uk with the right depth and flow characteristics. Tidal is very expensive due to being off shore and running cable ashore etc. We have built blades running in the Humber, Orkneys and soon to be in the Pentland Firth and off Ramsey Island in Pembrokeshire. One thing is for sure it is a recession proof industry...at the moment.
Assume the raw materials for these public, private and haulage transportation devices are made mostly by way of windmill and tidal barrage powered electric ovens and 1000C oversized hairdryers?
I'm fairly sure I said "almost".
But, yes, a large amount of energy is embodied in the materials used in production of stuff.
was 10% in the figures I saw for renewables.
1.4% of total global energy consumption is renewable source electricity.
assuming 50% efficiency for the rest, the only dent renewables make is approx 0.7% reduction in total energy consumption. And figure for HEP is approx 1/5th of that assuming that any pump storage is 100% efficient (which you could argue possibly is if all pumps are powered solely by dedicated windmill/PV isolated from grid)
I think what all this debate confirms is that to maximise the benefit of renewables, then an efficient way of storing electricity is essential. It also needs to be a solution that is compact enough to be located close to the users, in cities and countryside alike.
don't see why it needs to be compact and distributed close to place of use.
there's a national grid with international interconnects specially designed so that power can be sourced and exported based on demand and the characteristics of the generation source. so we can source solar from spain to power aircon during summer, and we can send them wind to power lighting in winter.
the storage bit is a given, since PV only work during daylight, turbines on windy days, ...
don't see why it needs to be compact and distributed close to place of use.
there's a national grid with international interconnects specially designed so that power can be sourced and exported based on demand and the characteristics of the generation source. so we can source solar from spain to power aircon during summer, and we can send them wind to power lighting in winter.
I'm no electrician but do you not get voltage drop over mains cables? I think you do with AC, but not sure about DC.
the only dent renewables [b]currently [/b]make
FTFY?
there's a national grid with international interconnects specially designed so that power can be sourced and exported based on demand and the characteristics of the generation source
I get the feeling the international part of that grid is going to have to get a whole lot more capable.
that's why they use high voltage AC distribution.
DC distribution was tried in teh early days of electricity. it didn't last all that long.
I'm no electrician but do you not get voltage drop over mains cables? I think you do with AC, but not sure about DC
Yes, but its calculable. And more important than just voltage drop is the power that ends up being converted by the cables into useless heat. This depends on voltage [i]and[/i] current [i]and[/i] the characteristics of the transmission medium (i.e. cables). Generalising, more current = more power lost.
Broadly speaking, loads of volts and not much current is a good combination - hence the lovely proportions of power pylons.
The losses of our national grid vary between around 7 and 12% depending on at what stage you take the power out. The earlier the stage and the higher the voltage, the lower the loss. Unfortunately, this means that domestic consumption, down at 240vac is one of the lousiest ones. In future, as our electricity demands at home grow (lecy cars, less dependancy on gas/oil and high potential for local feed in generation (solar pannels on roof etc) i would expect more houses to be connected at 3phase 440v to help in that respect.
It is in discussions of renewables that the subtle difference in meaning between "effectiveness" and "efficiency" become important. In fact, as the original energy source is free (we don't pay for the sun (yet 😉 absolute efficiency is less important than overall effectiveness, where effectiveness will generally be a measure of kWHr / £
A nice sunny day today. 18kWh produced so far. I ran the washing machine this morning (filled with solar-heated water) and cooked the beef for this evening's bourguignon at lunch time. There's enough hot water in the solar tank for at least 36h. Total consumption for the day will be around 4kWh with nearly all of it during production hours.
If I'd been really keen I could have under-cooled the fridge before morning peak demand and could do the same now before evening peak demand.
Now if every house with a roof/roofs well enough exposed to get December sun were equally energy positive then managing excess renewable production might be an issue. At present it just isn't, simply shutting down gas power stations is enough (but the gas generation companies don't like this and will do/print anything to prevent it).
In the near future intelligent metering and punitive tarifs will be enough to smooth demand as more renewables come on line. If people start making serious efforts to save energy there may eventually be so much surplus that intelligent use/smoothing demand, shutting down fossil fuel stations and increasing pump storage won't be enough. I look forward to seeing that day. At present every saving and every bit of renewable production is just less CO2 in the atmosphere.
i would expect more houses to be connected at 3phase 440v to help in that respect.
Barring car chargers, I can't think of any other applications where you'd need such massive amounts of power delivered continuously to the home?
Mind you, it's a bit scary to see how much electric an electric car actually needs to charge up. 85kWh capacity for the Tesla S, which would probably take about double that to charge, 170kWh, or about £30 in [i]current[/i] prices for about 250 miles of driving.
OTOH, if I (as the average man who doesn't want to actually pedal) could possibly stoop to commuting on an electric bike, I can buy one for a few hundred quid, and it has a battery with 0.36kWh capacity and does (allegedly) 30miles, which covers most commutes. I'm guessing that will cost about 20p to power a days ride to work and back.
nice to have a house that's technically energy positive.
and that's one of those that *does* have energy storage.
still very much reliant on baseload supply though.
I guess things like FIT payments, where someone can sit down at a table and show € / $ / £ numbers makes PV more enticing than solar water heater that (for the UK at least) just reduces the amount of gas/leccy you need to have a shower.
and imho, solar water makes more sense on a distributed scale than trying to implement strange things like H2/O2 electrolysis/heaters or molten salt batteries locally. save them for big grid scale.
leccy car for me is out of the question. dangling a 3 phase cable down 4 storeys is probably not going to be popular, and that's assuming I can guarantee a parking space.
[quote=Edukator ]Now if every house with a roof/roofs well enough exposed to get December sun were equally energy positive then managing excess renewable production might be an issue. At present it just isn't, simply shutting down gas power stations is enough (but the gas generation companies don't like this and will do/print anything to prevent it).
Though to reach the planned renewable targets that won't be enough - not even with intelligent metering etc. Hence this discussion.
At present every saving and every bit of renewable production is just less CO2 in the atmosphere.
When they're actually producing...
Best start reducing energy demand then.
How many people on this thread have any insulation under the floor of their house? How many have doors and windows with a uW of less than 1.2? How many have more than a bit of loft insulation, something in the cavity walls and double glazing with thermal bridges all the way around it and the original back door.
There are plenty of figures on the Net so you might find ones that vary a little but the average UK home is an energy disaster:
If you have "a 3-bedroom, 2-storey home, with a 160m2 floor area. Your typical electricity demand might be 4800kWh/year and your space heating demand is 18,000kWh/year. Your hot water usage is 3,800kWh."
We use less than a fifth of that and all renewable and with a surplus of electricity (our house is only half that typical size)
People will always blame the government and power industry but the solution lies in people doing something about their own homes rather than buying a flasher car than they need and flying to Australia on holiday.
that's why they use high voltage AC distribution.DC distribution was tried in teh early days of electricity. it didn't last all that long.
Not strictly true, they're building a sub-sea DC link to the Wirral outside my work so we can export all our (Scotland's) windy mill juice.
As for insulation and such - it's all very well getting preachy but when you're stuck with a 60's built terrace there's not much you can do that comes under the banner of "economically viable". Under floor insulation is on my list but only if I can get a bulk load at knockdown price. Fitting it is going to be fun as well.
Maxtorque - very good point, transportation issues need to be looked at as well. Local authorities actually have powers to force businesses to come up with a transport strategy as part of planning laws. sadly it's a very under-used power but when it is used the resulats can be very good.
Local authorities actually have powers to force businesses to come up with a transport strategy as part of planning laws. sadly it's a very under-used power but when it is used the resulats can be very good.
It's actually commonly used: every business related planning application we have submitted in the last few years requires a demonstrable travel strategy, especially if the business is expanding or building new premises.
We even have to produce them for care homes and the like.
DC distribution was tried in teh early days of electricity. it didn't last all that long.
High voltage low current is crucial for distribution - I think they went with AC originally because it's easy to step up and down - but it's probably more lossy overall so now we've invented better technology HVDC is feasible and advantageous?
HVDC will be and is used for things like railways and grid interconnects. UK-France one is HVDC for sure.
DC around the house could theoretically make sense when so many devices have a power brick (although some laptop ones still actually dish out AC).
Replacing an entire 210-250V (or whatever) AC distribution with DC around small communities isn't going to happen. Nor is augmenting existing supply with a parallel one.
Within our DNO we have been discussing DC supplies to people's homes. One DNO has done a trial of DC in people's homes.
It's not impossible, but most ideas revolve around a single AC-DC converter for the house. The other advantage is that we could then bang the LV volts up from the current 430V 3-ph to something a lot higher, reducing losses and increasing capacity.
No need to require the house, the existing twin and earth could be used. The sockets could be reused, but to avoid change over confusion (plugging AC gadgets into DC sockets and vice versa) it might be worth changing them.
This is of course power engineers idly speculating. The single AC-DC converter for the house would be massive at present.
DC around the house could theoretically make sense when so many devices have a power brick
All the power appliances go straight from mains AC, it's only the small fry that is DC.
the average UK home is an energy disaster:
and also not easy to upgrade to something less wasteful
DC around the house could theoretically make sense when so many devices have a power brick
I thought about this, but the power you'd lose in low-voltage DC wiring would be much more than the power you lose in the power bricks, I reckon. Plus the devices are all different voltages, so you'd have to have lots of circuits and types of socket, or you'd have to step the DC voltage down, which is probably lossier than the powerpack anyway.