Re: Energy alternatives for the UK.

In message <t7nsc15js33j9gg3jf4k3qqimg35gos5mm@xxxxxxx>, sylva@xxxxxxxxxxxxx writes 
On Fri, 8 Jul 2005 00:02:54 +0100, John Beardmore
<wookie@xxxxxxxxxxxxxxxxxx> wrote:

Non sequitur,

? 

Your earlier reply did not relate to my question, no matter, let's
start afresh.

I've never thought the issue under discussion was just about PV, and if
you are comparing PV to wind as it still seems you are, it's meaningless
to do that without knowing your average wind speed.


Yes, I guess you need to know both insolation and average windspeed at
a location. I think these are available for most of UK. What seems a
bit difficult to find is the cumulative performance or performance
under less than ideal conditions.

True. Most manufacturers do publish performance graphs, but some of them have to be poked before they yield them up.


Perhaps there is an opportunity for someone to market a weather
station with an aerometer and a solar pv array and data logger for
people to trial in their particular location before committing the
expense of a bigger system.

Maybe. To be honest, I'd be fairly happy to take published data for insolation unless I was interested a particularly quirky area, but wind is another matter. The national database is a very blunt instrument, and extrapolation between publish data up to 45 meters and gradient wind conditions is a bit of a black art, especially in a turbulent urban environment.

For big schemes, test masts are a natural part of evolving the projects. For small schemes, testing costs more than the proposed scheme so you look at the database, poke your fingers in the air and take your punt.


So anybody keen on going renewable to displace a proportion of their
grid electricity depends on manufacturers claims.

Which are increasingly subject to scrutiny according to established international standards.


As I said earlier the cafe at Pembroke had a panel showing electricity
generated to date, proportion of the demand displaced from grid and
cumulative power to date.

In my case at home I think it unlikely to be worth attempting this as
I live in an urban area and my electricity bill is small. The holiday
village I was talking about in W Highlands may be different but their
wind speed is also surprisingly low at 5m/s. Of course their
electricity is likely to be renewable hydro already, so cost saving
will be the driver here.

Yes, though any renewable contribution to the grid still helps. Think of it as pushing the influence of hydro south.


As their self catering chalets (occupied by tourists most of the year)
are all electric the first thing would seem to be moving to other
means of heating and cooking.

Maybe, though if their electricity comes from 100% renewable sources, would that help ??

(OK, I know my previous two thoughts are to some extent in conflict - I'm just illustrating that perspective and what you think you are paying for matter here.)


I would like to think a central thermal store heated by woodchip and
distributed by insulated pipe to underfloor heating would be
worthwhile for this.


Yes.


The cookers then being lpg powered. 

Yuk !  Maybe.


This would remove much of the electrical load. As this is a commercial
venture I am guessing there is less access to grants for renewable
electricity and unless the electricity is traded there is none of the
incentive of ROCs.


So aggregate and trade.


As the electricity demand will not be met by the
renewable much of the time I wonder if a grid intertie is worthwhile,
rather than just making use of the renewable when it is available and
diverting excess to a resistance heater in the thermal store.

So sell it all into the grid and trade the ROCs, while buying back cheap fossil power.

(But while the accountants and the algebra go one way, the electrons follow the suggestions of ohms law, so you still get the benefits to distribution of local micro-generation.)


As to the comparison, it's as important to know what's generated as what
the install costs.

While a 1kW peak output solar system might end up costing you £6,000 and
a wind system with the same peak output power might be substantially
less, if your mean wind speed is only 5m/s, the wind system will
scarcely cut in most of the time, and the PV might offer a better ROI.

Basically, think in terms of 'life cycle costs'. 

That's what I am trying to do and so far it looks to me that the idea
of an array of small wind turbines is not worthwhile because average
wind speed is too low


Where does this figure of 5m/s come form ?

If that's ground level, how high can you get them ?


and solar PV not worthwhile because the site is
too far north with few clear days.


Presumably quite cool though, which helps the PV case ?


I'll try and link a picture in a day or so, there are 5 or 6 of them
and they measure about 1.8m by 1.2m. They seem to have clear
polycarbonate covers, aluminium frame and back.

Are the covers flat ?

Yes

OK. Not Filsol then... 

Pictured at http://www.wokingnursery.co.uk/Dscn0290.jpg

As you can see they have taken a beating. 

Probably still work OK though.


My worry is that the pool would only need heating to 70C

? 30C ? 

I realised my mistake in mixing 70F with 21C, cancelled and resent the
message but you picked up the earlier one.


:)   No matter.


and the delta
T across the panels would be low, this is also indicated by the
inlet/outlet pipe sizes.


I wouldn't read too much into the pipe sizes.  Manufacturers seem to
think that 22mm is more macho than 10mm, but it doesn't take much pipe
diameter to harvest the available energy...

Yes but big pipe diameters imply a high flow with small delta T.

I know, but thinks like the Nippon Electric Glass DP-6 evacuated tube collectors come with 22mm pipes and it's quite unnecessary. I think the manufacturers just do it to tease.

Some pool heaters are actually unglazed, though these generally have unspectacular performance. In this instance you have a glazed flat plate collector, and while you may not have the niceties of selective absorber surfaces and a few other bells and whistles, it's probably not substantially worse than any other flat plate collector.


Alternatively, buy a controller that varies the pump speed
electronically to maintain an optimum delta T.


Yes and I'll put them in series once I figure out why they have 4
inlet/outlet connections.

Probably so they can be plumbed in series. Link a row of collectors together with pairs of pipes, then blank off top left and bottom right.

Cold in bottom left, warmer out top right. Voila ! Instant big connector.

What are the connectors made of ?  Looks like stainless in the picture ?


Also what would I lose by mounting them flat? 

60% in winter, 15% in summer very roughly ?  If you seriously want to
know I can work it out or look it up, but keep in mind that unless you
make them track the sun, they will almost never face an optimal
direction.


As my available flat roof is about 3m by 2.5 I think they will have to
stand on their narrow edge and tilt back to optimise for winter and
spring. I also think I would be best optimised for afternoon (i.e west
of south to give maximum yield for evening use.

Makes sense, but watch out for wind loading. Aim to cater for 100 year gust etc. Can be a very significant stress.


That said, I'd sooner put them on stands in the garden than flat on a
roof, and flat roof mounting is a bit of a dark art.

Garden is too overshadowed. 

OK.


In terms of delivering the electrical power produced to the grid it is
high, say 10% losses between generator and user. In terms of
thermodynamic performance I imagine ranging from 30% thermal in to
about 60% with integrated direct fired gas turbine and boiler. There's
scope to better this with solid oxide fuel cell integrated gas turbine
but it's a long time a coming.


OK, but wave, coal etc all have transmission grid losses.  I suppose my
point is that 40% efficiency in coal burning is a poor use of a finite
resource, and 70% efficiency in a duck is pretty good use of a renewable
resource.

I agree, overall it's the cost delivered to the consumer that counts. 

And the environmental footprint of that consumer...


If we break the costs down to capital charges, operation and
maintenance and fuel costs per kWhr(e) delivered to consumer then even
with zero fuel costs the renewable options tend to have high capital
costs.


Agreed.


The offshore option adds the capital cost of an umbilical and
decreases the generator's production reaching the consumer.

Yes, though wave at least tends to deliver power near the shore. It's not as if you need a forty million quid cable to get to Orkney or anything.


Cheers, J/.
--
John Beardmore
.

Relevant Pages

  • Re: (OT:) EVERYBODY shoudl see this, as well
    ... of Generating Electricity," comparing the costs of generating electricity ... The true costs of generating electrical power are ... compared with 3.7 p/kWh for onshore wind and 5.5 p/kWh for offshore ...
    (alt.autos.toyota)
  • Re: (OT:) EVERYBODY shoudl see this, as well
    ... of Generating Electricity," comparing the costs of generating electricity ... electrical power from various sources and the price that consumers pay is ... p/kWh for offshore wind farms." ...
    (alt.autos.toyota)
  • Re: (OT:) EVERYBODY shoudl see this, as well
    ... Generating Electricity," comparing the costs of generating electricity from ... The true costs of generating electrical power are ... compared with 3.7 p/kWh for onshore wind and 5.5 p/kWh for offshore wind ...
    (alt.autos.toyota)
  • Re: A programme to tackle the Environmental Crisis
    ... "The so-called renewable forms of energy (wind, wave, solar, ... electricity, assuming there is a broad spread of wind farms. ... Wind Power is actually a very rapidly growing industry across the ...
    (sci.energy)
  • =?ISO-8859-1?Q?Re=3A_=A32bn_offshore_windfarm_to_go_ahead_off_north_Wa?= =?ISO-8859-
    ... “The renewables sector already benefits from subsidies worth around ... the spirit of the new European Electricity Directive aimed at ... In any case there is a strong case for arguing that the costs of wind ... This is evidence that the cost of wind-power is being under-estimated. ...
    (uk.politics.misc)