Posted By: tonyThe idea of decentralising energy is basically a good one

Why?

Posted By: djh

Posted By: tonyThe idea of decentralising energy is basically a good one

Why?

By their very nature fossil fuels are incredibly practical because they are concentrated forms of stored energy, that can be transported to a centralized point and turned into a usable power source for distribution, as required and on demand.

The challenge for renewables is that they all most all have mostly almost the exact opposite qualities (with exceptions)

Posted By: SteamyTeaProbably end up with a huge nuclear installation sited in Westminster.

Some might view that as an improvement ;-)

Posted By: tonyThe idea of decentralising energy is basically a good one but in itself it is not an answer to our problems.

I would like to the emphasis on reducing demand rather than relying on the ideas of decentralisation as a be all and end all.

Tony,

I would think it would go hand in hand. If you have to get by on the energy you can produce yourself on site then you will naturally tailor your usage to suit I would have thought.

Jonti

but CHP does not necessarily have to be decentralised all we have to do is to make use of the "wasted" heat from generation.

Posted By: tonybut CHP does not necessarily have to be decentralised all we have to do is to make use of the "wasted" heat from generation.

Dont think that will ever happen in the UK as that involves joined up thinking which DECC are not capable of doing. Once looked at a proposal to build IGCC plants throughout the UK in population centres in excess of 100k with river or canal access for fuel delivery and was surprised by how many towns and cities it covered. It then provoked the inevitable question of why has it not been done before as it would be so easy. We could not find any logical answer apart from political will or brown envelopes depending on how cynical you are.

Physics are not against moving a hot mass. It is very simple technology used effectively in Denmark for decades which has been ignored by the UK which is why where in such a mess.

Its not a new discussion as can be seen from this old paper

http://www.cibse.org/pdfs/8aamos.pdf

Just think how much better off the UK would be now if every gas fired power station built in the last decade was linked to a district heating system similar to Denmark.

Posted By: renewablejohnPhysics are not against moving a hot mass

Physics of moving mass, hot or otherwise, is limited because a Joule, the unit of energy, is the force required to move 1 kg 1 metre. Then you have the Specific Heat Capacity of the mass you are moving, so air can move 1 kJ.kg^-1.K^-1, water can move 4.2 kJ.kg^-1.K^-1. Note this is mass not volume. So to move a kWh of energy at say 98°C (about the practical limit of water without going to a high pressure system) and to be used at 50°C at point of delivery, 1 km, you will need to use:

3.600 (kJ) / 4.2 (kJ.kg^-1.K^-1 x 48 (°C))
=
17.86 kg

17.86 (kg) x 1000 (m)
=
17.86 kJ

17.86 (kJ) / 3600 (s)
=
0.0049 kWh

You then have to bring the water back to the CHP unit, so double that:

0.0098 kWh

or about 1% of the energy is lost for every km it is moved and that is before thermal losses, friction losses, pump inefficiencies and assumes level ground. Start pumping against gravity and multiply it by 10.

Now lets look at induction loop charging, a great technology and very keen on it myself as I hate tripping over leads.
Yes it can transfer large amounts of electricity very short distances, but where is that electricity generated? Locally or remotely. There is some scope to have shopping centres/Industrial Complexes/Leisure Facilities with a CHP unit, but each one of them (except some very large processing facilities) have limited opening hours and any excess thermal/electrical energy needs to be either stored (my preferred choice) or distributed.

So we are back to non-local distribution or lower efficiencies.
Take your pick

Posted By: renewablejohnSo that I can make loads of money ????

That seems like a good reason. Vote for John!

Centralisation is necessary until we find the holy grail of efficient, localised energy storage.

Tonys OP is therefore probably correct, until that time, reduction should be the priority.

But it wont be for economic reasons, we live in a consumer driven economy

Posted By: djhIt has nothing to do with moving mass at all

What is a Newton?

You're always going to have slightly lower efficiency in decentralised energy use if you're talking thermal plants ST, no one is disputing that. That doesn't mean it isn't a better way to do things sometimes.

It's not a binary decision, there's no reason you can't have both. And IMO there's no reason to have an entirely centralised system any more. There are too many good opportunities at a decentralised level.

It's slightly more decentralised than in the past, but hardly the optimal mix. Change comes slowly in the UK. We could learn much from some of our European neighbours.

Just to put thing into perspective, most of the old thermal plants are 40 to 60 years old now. Not really relevant to compare yesterdays technology with todays.
Then there is total lifecycle costs, we have little experience of this yet with the latest technology but plenty with the old ones.
There is also the issue of renewable not meaning unlimited, by just about any measure renewable generation as we think of it is very limited