Posted By: SteamyTeaHow does this work without a centralised system to take any excess?

Brief outline on a dutch smart grid

http://www.cospp.com/articles/print/volume-11/issue-3/features/implementing-micro-chp.html

Steamy

Bit more technical stuff as I know you like this sort of thing. Personally I am only interested in the fact that it works.

http://www.federesco.org/images/PowerMatching%20City.pdf

Posted By: SteamyTeaNot read the last link yet.
But the first two are lacking in detail. And it still needs a centrally controlled grid. Also there is an assumption that more local smart grids with more distributed generation will result in more stability, dubious claim that one.

Smart nodes (devices that are frequency and voltage responsive) enhance grid stability. The voltage/frequency "data" is the result of local information and available globally but requires little in the way of central control if your loads are intelligent.


Copy paste from an email of mine of an outline of what this might look like:

Not all energy (and electricity specifically) is
created equal. Propose categories of devices; say:

1) Non negotiable loads. Heart and lung machines, heating and alarm
systems, boradband, and emergency/transit lighting features.

2) Partially negotiable loads. Stuff I don't mind turning down a
little in an emergency. Slower kettles and washing machine heaters for
example.

3) More negotiable loads. Stuff that I don't mind turning off
completely in an emergency or that waits for certain criteria to be
met before operating. EV charging and dishwashers that wait for
troughs in the night rate for example.

4) Stuff I really couldn't care less about. I'll take excess Wind, PV
or Nukes if it's there to top off the EV or preheat some thermal mass
with a heat pump but really am not that fussed about it.


Controls have to be piss fucking simple. I would use frequency to
signal grid load, and half hourly data via broadband or GPRS to signal
price and CO2 intensity (less critical if unreliable; fairly
universal; reversion to "flat rate/peak rate" isn't catastrophic.


Controls absolutely have to be in the hands of the consumer not the
supplier in order to be palatable. This means intelligent nodes. From
boggo basic 50p TRIACS dropping the odd half-cycle in devices with
resistive heating elements to that plus a timer for "getting close
enough to what are very predictable troughs" in white goods to perhaps
something smarter still that I can show off down the pub/use for home
automation via my iPhone in lighting an AV gear.


*I* choose the CO2/kWh threshold, or the £/kWh threshold, for the
various categories of appliances. *I* set my own demand curves. *I*
choose what works how and when (other than emergency frequency based
demand response). Utilities can get stuffed. Daily Mail is happy.


Savvy smart meter operators also ought to be happy. Or broadband
operators providing network nodes. Or cable/satellite TV operators
providing the base for AV and home automation by extension. Or games
console manufacturers. Or smartphone manufacturers deciding to nail
one to the wall. (my Google Nexus 4 was £160, contract free and
unlocked, and utterly spanks any device designed to be integrated into
buildings in terms of connectivity and processing power per $)


Why? Many people will be happy with the default settings out of the
box, provided that you're reasonable about programming all new
products with these technologies included. (any that don't have them
don't get A ratings for energy efficiency or are otherwise taxed in
order to raise money/punish importers of generic chinese "world" goods
etc) The innovators/leaders/early adopters (and objectors) will want
to set their own thresholds though, and they'll want a centralised way
to do this. You then sell, as a service/product, ratther than imposing
it, a way to manage your electricity demand.


The more exposure you give the customers to true cost of generation
the better in this respect. You must be able to play the game. (none
of it works if all electricity is 15p/unit 24/7) Duty-free thresholds,
or power limits below which electricity is flat rate but above which
it is priced differently, or variable tariffs for interruptible
suppliers, or half hourly pricing, or any of the models that already
exist and are proven to work for larger users, would all work here.

http://brightgreenisland.com/

Here is a link to the main website for the Bornholm sustainable community project.

Took a day trip there last August and should go back for a longer stay in the next year or two.

Well worth a visit if you get a chance.

Steamy

How can you say there inefficient and costly, Electric efficiency is better than coal and combined efficiency is better than coal or gas. As for costly if your already replacing an old gas boiler than the additional cost of a CHP unit is minimal. Think the UK target was 1 million old gas boilers per year which if replaced by CHP would soon have a significant effect on daily demand.

Have read that third link you posted, more about the economic model on a very small scale. They do acknowledge that the system has technical limitations (power quality) which is pretty important when comparing to an existing system.
They don't say what happens when the thermal stores are all full (or if they did I missed it).
There is also a potential problem when individuals try and play the market by withholding generation.

What sort of CHP are you asking about Steamy? There's a big difference between domestic µCHP, district heating CHP and large power plant CHP.

Here in the UK the only µCHP systems available are heating led. They only run when there's demand for heat, any electricity they produce is a nice little bonus on top. So strictly speaking they don't need a heat store, although coupling them to one does improve efficiency somewhat.

Well, given current near-zero interest in µCHP I don't think we're going to have any problems with an overabundance of it any time soon.

Electrical output is 1kW for a unit like British Gas's Baxi µCHP, so like you say it's designed to just deal with domestic base load, with any excess only going as far as one or maybe two adjacent houses away.

You're not ever going to have an oversupply of heat, because they're only responding to demand for heat within the home they're in anyway. It essentially works just like a gas boiler that also produces some electricity.

Ed, that is for my heating and DHW for the day, and the washing machine was on when I read the monitor.
The heating and DHW come on at 4, about the lowest CO2 intensity time, day before yesterday all the hot water (200lt) was used, that is a rare day, won't know what today's usage was till midnight.

Posted By: SeretElectrical output is 1kW for a unit like British Gas's Baxi µCHP, so like you say it's designed to just deal with domestic base load, with any excess only going as far as one or maybe two adjacent houses away.

That is why I think they are so small, keeps the grid stable.
The only way I could see a district system working is with quite a lot of storage and running the CHP unit at times of peak load only. May be useful for flats where gas is a danger and the space heating loads are pretty small, so mainly used for DHW and electricity.

What do you expect at 6 in the morning, shall go back and change it.

Edit 07/12/2013
For anyone interested, yesterdays usage was 19 kWh of which 16 kWh was between 4 AM and 7 AM. So about £1.50
When the monitor is calibrated that will come out at about 16 kWh. Yesterday was pretty warm, about 10.2°C with a Min of 8.7°C and a Max of 12.4°C, not much wind and a bit of sun (230W.m^-2).
Trouble is with storage heater is that I don't use any less when it is hotter than normal, just end up with a warmer house.

There are problems when many PV systems are on the same local circuit though, the DNOs tend to put it right. I am not sure how they do it, are there automatically adjustable transformers or do they just over engineer?

Power boys down here are really pleasant, though they are the ones with permanent jobs !

I can't see how that makes any sense at all; the frequency of the national grid has practically nothing to do with with loading conditions on the local network.

The national grid won't go over-frequency just because the tappings on one particular local transformer (which have been set to prevent an undervoltage when everybody's heat-pumps are running in the winter) are too high to prevent an overvoltage when the heat pumps aren't running in the summer but the PV is producing at maximum.

Posted By: SteamyTeaI also do not have any way of working out how much frequency will change for any given change in demand.

Frequency doesn't depend on demand. It depends on the imbalance between generation and demand.