Why is local renewable electricity generation seen as so desirable by green folk

[dan_aka_jack]

I don't understand why local generation is often seen as so much more desirable than centralised renewable electrical generation.  Centralised is likely to be more cost effective both in terms of £ per MWh and in terms of £ per tonne of CO2e saved.  A megawatt of centralised PV is cheaper and easier to install, maintain and manage than a MW of roof-mounted PV.  Centralised solar arrays can be optimally orientated and kept clean; roof-mounted solar arrays can't (so easily).  Off-shore wind turbines get plenty of wind and are invisible to the majority of the population; neither of these statements are true for urban roof-mounted turbines.

Yes, about 8% of the electrical output from powerstations is lost in transmission and distribution.  But it's important to tease apart long distance transmission and local distribution.  1.6% of total generation is lost in long-distance high voltage (hundreds of thousands of volts) AC transmission; 6% is lost in local low voltage distribution (SEWOTHA notes p116).   If you're sending power across a local community then you'll still incur 6% local distribution losses, surely?  (I assume these losses are mostly in the 230v wiring running under the local streets; IIRC power lost is inversely proportional to the square of the voltage; i.e. for a given power draw you'd lose 4 times as much power in distribution at 100v as at 200v).  Heck, even if you're just sending power from your own PV array to your own toaster then you'll still incur a loss of somewhere between 1-15% in the inverter and wiring.  The evidence I've seen suggests that local community generation and distribution incurs losses only fractionally smaller than centralised generation.  Maybe I've missed something.

And local generation might not help much in terms of local energy security, either.  If the grid goes black then all the local community renewable generation units will automatically power down and won't come online again until the grid spins up again.  Almost all inverters and generators are designed and mandated to only push power into a live grid; they will refuse to turn on without a healthy grid to feed into.  Even if you could (illegally) hack your inverter to push power into a black grid, you'd risk electrocuting the grid engineers and causing a serious short circuit when the grid comes back on again because the inverter and grid are very likely to be out of phase.

Perhaps there are psychological benefits to having PV arrays dotted over urban roofs.  But I struggle to see any engineering or financial benefits to local PV / wind generation (taking an economy-wide perspective where FITs cancel out).  Maybe it'll benefit the economy to have lots of PV engineers gainfully employed.  But wouldn't it be better if those engineers were trained to retrofit insulation, not PV?

What have I missed?!

Local renewable generation of heat, on the other hand, is a great idea (because heat can't be sent very far).

[rhys]

Take a look at Woking Borough Council who have lead the way on local generation of electricity. The core of the local grid is Combined Heat and power as you say Heat is difficult to distribute and is wasted in Cenralised powerstations!! It not just transmission losses but heat put up cooling towers.
One the local grid  is there it may as well be used for linking in PV's on the roofs of available buildings.
http://en.wikipedia.org/wiki/Woking

[dan_aka_jack]

Good points, thanks.

I suppose I'm really comparing local renewable generation with centralised renewable generation.  Sure, placing a natural gas power station near to buildings is a good idea so you can use the heat.

My point is more like this: say I have a million pounds to spend.  I'd be much better off spending that million pounds on off-shore wind than on roof-mounted PV, surely?

[RichardKB]

In theory roof mounted PV will need a lot less maintaining than any wind power be it on or off shore.

Rich

[djh]

In theory roof mounted PV will need a lot less maintaining than any wind power be it on or off shore.

It'll still cost a lot more.

BTW, apparently the government's latest planning proposals have something to say:

“Local planning authorities should assess their area for opportunities for decentralised energy. The assessment should focus on opportunities at a scale which could supply more than an individual building and include up-to-date mapping of heat demand and possible sources of supply. Local planning authorities should in particular look for opportunities to secure:
i. decentralised energy to meet the needs of new development;
ii. greater integration of waste management with the provision of decentralised energy;
iii. co-location of potential heat suppliers and users; and,
iv. district heating networks based on renewable energy from waste, surplus heat and biomass, or which could be economically converted to such sources in the future.”

[dhaslam]

Wind generation is  more suited to wide open spaces but there is a  social benefit to having electricity generated locally.  If a local group puts up a ten million pounds worth of turbines and they pay for them over say seven years  they  then have another ten million to spend over the next seven years and much of that expenditure is likely to circulate in the same area.  The same thing applies to individual householders  except on a smaller scale and also wind generators cost about four times as much on a small scale.     PV seems to be the one that is preferable to be  owned by individuals.  

[martin]

One word- "control" - we are hopefully coming to the end of a period of government by the most controlling government (apart from North Korea) for a very long time - on this evidence I don't trust central government with it's own dinner money, let alone ours...... (of whatever party that's likely to end up in power, they're all a bunch of scrotes).
As things get worse (as they will), while the razorwire is being erected, and the Kalashnikovs dug up, the last people I want in control of my power supply are central government - far better to have it at local level (where we have at least a slight hope of exerting some control) - there are already highly successful small schemes based around wind, and at least one of the Scots Islands have a community generation scheme
What's wrong with "local" grids that may choose (or not choose) to export/import from a national grid network, whilst retaining local control?

ps, lest you missed it, roof mounted turbines don't work!

[dan_aka_jack]

"local control", when talking about infrastructure projects the size of a local grid, would probably mean "local council control".  I'm far from convinced that local councils are preferable to central government.  Especially considering a number of UK councils don't accept anthropogenic global warming.  At least central government has scientific advisers (even if central government fails to listen to those advisers).  Local councils get their "science" from the media.

[martin]

As I said, they're all a bunch of scrotes, but at least they're local scrotes that you can "deal with at a local level" -  we're also talking energy coops, not parish councils

http://www.westmill.coop/westmill_home.asp
http://www.ecodyfi.org.uk/prbdcrsept06.htm
http://www.theecologist.org/News/news_round_up/398810/largely_selfsufficient_scottish_island_wins_prize.html

it also rather turns the "not in my back yard" thing on it's head - in that it'd be in everybody's backyard, and people would have to make the choices, and put up with the results of their choices - I don't think it's very fair for people living in downland villages to decide the Downs are "too pretty for turbines" and happily importing electricity from far less efficient and pricier offshore windfarms - if you want power, you generate it - on your own doorstep!

[dan_aka_jack]

it also rather turns the "not in my back yard" thing on it's head - in that it'd be in everybody's backyard, and people would have to make the choices, and put up with the results of their choices

Yeah, very good point

[KenB]

Dan,

Local renewable generation only comes into its own if you can utilise the waste heat directly.

Most UK houses need heating for 5 or 6 months of the year, and the balance between waste heat and electricity production well matches the requirements of a typical UK house.

In another post, I have just pointed out that the UK generators are planning to build 18GW of CCGT plant over the next few years to replace the coal plant that is being closed under the Large Combustion Plant Directive, and a  further 15GW to replace our ageing nuclear plants is on the radar for around 2020.

A commercial CCGT plant gets 50% efficiency typically  (some slightly better) - but we still waste 50% of the energy in the gas, and very rarely is the waste heat used for space or industrial heating. Imagine how many of hectares of greenhouse you could heat with the waste heat from a CCGT plant - not to mention the CO2 for plant propagation.

So back to your question - why greens want local renewable generation:  A number of answers, some more relevant than others:

1.  They want to be partly in control of their future energy supply - don't trust utilities or corporates
2.  They do it for the environmental reasons
3.  They do it as a technical challenge - to show it's possible  ;-)
4.  They want the ability to sell back surplus to the grid.
5.  They like importing goods from the other side of the planet, with a high embedded energy  - mostly Chinese coal

This gets me thinking, that with the relatively low cost of natural gas, and the successful Lister spark conversion, there would be no reason to prevent you running it on natural gas.   At 20% efficiency or thereabouts - you would burn 5 units of gas (16.2p), and get 1 unit of electricity 11.2p back plus 3 units of heat worth 10.8p.  So you make 5.8p profit.

On a typical winter's day you might burn 100units of gas - or  £1.16 profit.  Do this for 6 months of the year - and its like £215.76 off your gas bill.

But at the same time you are not importing any electricity, so that saves a further £156.24, and you are able to export your surplus power for 10p per unit  - another £232.5 per year.

So for 6 months you buy 100kWh of gas per day costing you £604.50, less your deductions of - wait for it - exactly £604.50!  (WOW!)

So you have totally offset your gas bill, your electric bill and are now heating and powering your home for free - rather than the £760 that you were previously forking out to Southern Electric and Gas - or who ever.

On cold days - you are quids in.  Not exactly in the spirit of renewables - but if microgeneration - like the Baxi unit - see below, will get paid for their power why not a Lister?

http://www.baxi.co.uk/information/feed-in-tariffs.htm
  
Just off to see my creative accountant - I may be some time ;-)


Ken


Erm - the maths may be a little flawed - but not sufficiently to outrule the overall plan.

You spend £605 on the gas, and you get back £325.50 for the surplus power you export, so you have a total outlay of £279.50 compared to £761.

Your winter energy costs have been reduced to 37% of what they previously were.

[martin]

But the thing that nearly always remains unspoken in discussions of this sort is the simple concept of "if you don't use it, you don't need to generate it"........
and taking my "you can shower perfectly satisfactorily on 3 litres of water at 38c, anything more is a luxury" attitude to it's logical conclusion we're far too keen to "start at the wrong end" - if we concentrated far more on using less, the problems start diminishing..... (my contention is that if we got fusion power running tomorrow it would be a disaster - we need less people doing less "stuff", not the other way round..........)

[dan_aka_jack]

@Ken  Nice response Ken!  Many thanks.  Interesting stuff (as always).

@Martin I don't think you need worry about fusion being rolled out at scale any time soon

[KenB]

Jack, Martin,

Small scale heat and power schemes often fail because of NIMBYISM.

In Redhill we have a large county hospital in a semi-rural, out of town location - heaven knows what it's heat and power bill is.

Less than 1.5 miles away we have one of the biggest landfill sites in Surrey.

Some years ago an incinerator was proposed, which with steam coils could produce enough heat and power for the whole hospital site and the surrounding properties including a BUPA private hospital and a converted asylum - now posh mansion flats.  Unfortunately incinerators were out of fashion - so they just extended the landfill to the adjacent fuller's earth pit to take up the extra demand.

I suppose they could revisit this one day, and use landfill gas or gasification technology to provide a more acceptable CHP solution than incineration.


Local Councils, joined up thinking - don't think out council tax stretches to that. 

Do we get a poll tax reduction when they start laying off some of these super-numeraries?  Same council tax revenue for less employees does not sound like an increase in efficiency to me?


Ken

[dan_aka_jack]

Ken, you should consult on behalf of local councils.  Seriously.  They could do with your help.