footleg
New member
graham said:
Solar panel costs 'set to fall'
By Roger Harrabin
Environment analyst, BBC News
http://news.bbc.co.uk/1/hi/sci/tech/8386460.stm
Farmers using streams for Hydro electricity
- Thread starter Daz_of_caving
- Start date
Solar panel costs 'set to fall'
By Roger Harrabin
Environment analyst, BBC News
http://news.bbc.co.uk/1/hi/sci/tech/8386460.stm
kay
Well-known member
footleg said:
"At a conference, the institute forecast that solar panels would be cost-competitive with energy from the grid for half the homes in Europe by 2020 - without a subsidy.... Cloudy northern countries like the UK could wait further, possibly up to 2030. But the day would come when solar panels on homes would be cost-competitive without a subsidy, even in Britain."
Re; 'water wars' - it happened in mid Wales in C19 - all the mines used water power for pumping, winding and dressing; water resources were pretty fully exploited in the more densely developed parts of the orefield, with leats tens of miles in length (often paralleling each other up the hillsides) and series of water wheels one below the other to maximise energy available. Some mines, in low flow conditions, resorted to breaching leats above theirs to divert flow to their wheels. It ended in lawsuits.
Maybe a glimpse of fings to come?
Maybe a glimpse of fings to come?
If your scheme needs more than 20 cubic metres per day of water then you will most probably need an abstraction license. In issuing the license the EA will consider factors like how it affects other users of the water course as well as the environmental impact etc.
Failure to get a license is an offense and your scheme would be shut down, so probably no water wars.
Failure to get a license is an offense and your scheme would be shut down, so probably no water wars.
jarvist
New member
It's a fallacy to think that PV doesn't work in the UK - in the South West in particular it is really quite sunny (as much insolation as south Germany), the coast of East Anglia and South Wales is pretty good too.
http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_Europe-solar_opt_presentation.png
And here's just the UK (with a south facing inclined panel):
http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_solar_optimum_GB.png
A major component of the cost of a rooftop PV system is the installation (both mounting and labour).
It already makes economic sense to seriously consider if you're re-roofing anyway (and particularly if you have a south facing roof and aren't hidden under trees).
You can get cells that pretend to look like normal slates:
http://www.solarcentury.co.uk/PV-Installers/Products/Solarcentury/C21e-Solar-electric-roof-tiles-slates
A typical installation cost is still ~?10k though.
Though on the plus side they've just started revising the lifetime estimates for modern day cells UPWARDS from 20 --> 30 years.
I went to a talk a few months ago from a Solar bigwig, who said that in the south of France the solar roof conversion are being referred to as 'Pensions' with the idea that the roof will be providing cash for electrons long into retirement.
http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_Europe-solar_opt_presentation.png
And here's just the UK (with a south facing inclined panel):
http://re.jrc.ec.europa.eu/pvgis/cmaps/eu_opt/pvgis_solar_optimum_GB.png
A major component of the cost of a rooftop PV system is the installation (both mounting and labour).
It already makes economic sense to seriously consider if you're re-roofing anyway (and particularly if you have a south facing roof and aren't hidden under trees).
You can get cells that pretend to look like normal slates:
http://www.solarcentury.co.uk/PV-Installers/Products/Solarcentury/C21e-Solar-electric-roof-tiles-slates
A typical installation cost is still ~?10k though.
Though on the plus side they've just started revising the lifetime estimates for modern day cells UPWARDS from 20 --> 30 years.
I went to a talk a few months ago from a Solar bigwig, who said that in the south of France the solar roof conversion are being referred to as 'Pensions' with the idea that the roof will be providing cash for electrons long into retirement.
Robert Scott
Member
More Whitelackington-ism?graham said:
R
robby69hughes
Guest
could anyone explain to me how to work out a possible output from volume and head etc 
H
hoehlenforscher
Guest
For a rather basic method (but good enough to know whether it is worth pursuing further) you need to estimate the flow in litres/second. On a small stream you can do this with a 10 litre bucket and see how long it takes to fill. Say it fills in a second then that is 10l/sec. Convert to cubic m/sec, in this case 0.01. The multiply by the head you have in metres (say 100m) and by the constant for gravity (roughly 10). This gives a figure of 10. Divide by an factor of 0.6 to account for inefficiencies and losses in the system and you come up wth a figure of 6 which is the theoretical KW/h output from a 10l/sec stream falling 100m.
In other words
Power = flow rate (m3/sec) x head (m) x gravity (9.8) / Efficiency constant (0.6)
Hardest part is estimating your flow volume. On larger streams you can get a figure by measuring the cross-sectional area of part of the channel and measuring the rate of flow using a stick timed over a set distance. Some simple math will give you a reasonable estimation of the flow rate.
In other words
Power = flow rate (m3/sec) x head (m) x gravity (9.8) / Efficiency constant (0.6)
Hardest part is estimating your flow volume. On larger streams you can get a figure by measuring the cross-sectional area of part of the channel and measuring the rate of flow using a stick timed over a set distance. Some simple math will give you a reasonable estimation of the flow rate.
AndyF
New member
Tis my opinion that the whole micro generation concept is slightly misguided in its approach.
As stated, most systems are geared towards domestic electicity and selling capacity back to the grid. This inevitably makes for complex electronics and a long "pay-back" time.
Another apporach is to use the electricity generated just for heat. This is much simpler, as all you need at the back end is a simple storage heater type thing, consisting of a concrete block with a resistor in it, or an emersion heater element in a water tank, or driving pumps on your water solar panels.
The cost is a fraction of the "sell-to-grid" model, the generator is simpler, you don't need an inverter to match power to grid frequency.
The lower take up cost and pay back costs mean more people could do it....but the technology is not sexy so doesn't get grants and investment.
As stated, most systems are geared towards domestic electicity and selling capacity back to the grid. This inevitably makes for complex electronics and a long "pay-back" time.
Another apporach is to use the electricity generated just for heat. This is much simpler, as all you need at the back end is a simple storage heater type thing, consisting of a concrete block with a resistor in it, or an emersion heater element in a water tank, or driving pumps on your water solar panels.
The cost is a fraction of the "sell-to-grid" model, the generator is simpler, you don't need an inverter to match power to grid frequency.
The lower take up cost and pay back costs mean more people could do it....but the technology is not sexy so doesn't get grants and investment.
Chocolate fireguard
Active member
The formula assumes the water has fallen freely for 100m and has therefore converted all of the gravitational potential energy (GPE) to kinetic energy (KE). The water would be travelling at around 45m/s or 100mph. The 6kW is a reasonable estimat of the electrical power you might get from converting all of the KE (MULTIPLY by 0.6). On any hillside the majority of the GPE will in fact be converted to heat, via friction, leaving little for KE. The crucial thing is that the KE of a mass is proportional to the SQUARE of its speed so if the water were still moving at 15m/s (still over 30mph and probably faster than any stream I have seen) this is one third of the assumed speed and so the KE is one ninth of 6kW. A more realistic 5m/s for the average speed means the KE is reduced by a factor of 81 and we struggle to light half a dozen low-energy bulbs. The obvious solution is more buckets per second but even a healthy stream of 1 cubic metre per second still only gives 7.5kW. It might be worth pointing out that it is not possible to take ALL of the KE from the water as that would mean stopping it completely and the turbine would soon be full! But things work for us here and reducing the speed from 5m/s to 1m/s means we have captured 96% of the KE.hoehlenforscher said:
Things may be better though. The stream will reach its 5m/s or whatever very soon after setting off downhill so it may be feasible to set up several mini generatore along the way so long as they are far enough apart to allow the water to reach "terminal" speed between one and the next.
exsumper
New member
If you have a stream or river on your land, it is a comparatively simple process to convert second hand, three phase synchronous motors (freely available from any scrap yard),to power generation. I won't go into the technicalities here, as there are numerous sites on the web (devoted to cheap generation of power for third world communities), that can explain the conversion process far better than I can. having accessed the advice, If you can't work out how to install said motor to provide free power, then you're not a practical enough person to be dabbling in such matters anyhow.
The original BBC report referred to in this thread mentioned a community hydro project in the Dyffryn Crawnon valley. Dyffryn Crawnon is very steep-sided, a classic U-shaped, glacier formed, valley and so would be ideal for these projects.
At least two of the steeply falling streams in the valley issue from caves. I wonder (if these particular streams are ever used) if the local community may become concerned about cavers entering the caves, particularly with worries over digging activities altering water courses. Of course education may help but with peoples power supplies and income involved it may not count for much and an attempt to restrict access could be made.
Just picking a scenario out of the air!
At least two of the steeply falling streams in the valley issue from caves. I wonder (if these particular streams are ever used) if the local community may become concerned about cavers entering the caves, particularly with worries over digging activities altering water courses. Of course education may help but with peoples power supplies and income involved it may not count for much and an attempt to restrict access could be made.
Just picking a scenario out of the air!
Pitlamp
Well-known member
H'm - feeling ever so slightly embarrassed; on 1st December I foolishly wrote a post mentioning that hydrams don't need a stream and just a pool would do. Of course a flowing stream is essential to provide the kinetic energy which works the pump itself. So I apologise for that mistake!
However I don't agree with Rychydwr that efficiency is an issue. In absolute terms hydrams aren't efficient but because they are using a sustainable resource (i.e. a flowing stream which just keeps coming) then the efficiency of the actual pump is less relevant. Hydrams are cheap (you can find blueprints on the interweb telling you how to make DIY hydrams from old fire extinguishers and car inner tubes - in fact someone did just this on the GG winch meet not long ago to ensure a supply of water to the bog tents, which made an electric pump redundant). So all you need to do is install a number of hydrams (each one effectively using the same water in the stream) and you can pump loads of water uphill free. Once you've got an elevated supply of water (gravitational potential energy) then you can easily generate free sparks.
However I don't agree with Rychydwr that efficiency is an issue. In absolute terms hydrams aren't efficient but because they are using a sustainable resource (i.e. a flowing stream which just keeps coming) then the efficiency of the actual pump is less relevant. Hydrams are cheap (you can find blueprints on the interweb telling you how to make DIY hydrams from old fire extinguishers and car inner tubes - in fact someone did just this on the GG winch meet not long ago to ensure a supply of water to the bog tents, which made an electric pump redundant). So all you need to do is install a number of hydrams (each one effectively using the same water in the stream) and you can pump loads of water uphill free. Once you've got an elevated supply of water (gravitational potential energy) then you can easily generate free sparks.
The formula assumes the water has fallen freely for 100m and has therefore converted all of the gravitational potential energy (GPE) to kinetic energy (KE). The water would be travelling at around 45m/s or 100mph. The 6kW is a reasonable estimat of the electrical power you might get from converting all of the KE (MULTIPLY by 0.6). On any hillside the majority of the GPE will in fact be converted to heat, via friction, leaving little for KE. The crucial thing is that the KE of a mass is proportional to the SQUARE of its speed so if the water were still moving at 15m/s (still over 30mph and probably faster than any stream I have seen) this is one third of the assumed speed and so the KE is one ninth of 6kW. A more realistic 5m/s for the average speed means the KE is reduced by a factor of 81 and we struggle to light half a dozen low-energy bulbs. The obvious solution is more buckets per second but even a healthy stream of 1 cubic metre per second still only gives 7.5kW. It might be worth pointing out that it is not possible to take ALL of the KE from the water as that would mean stopping it completely and the turbine would soon be full! But things work for us here and reducing the speed from 5m/s to 1m/s means we have captured 96% of the KE.Chocolate fireguard said:
Things may be better though. The stream will reach its 5m/s or whatever very soon after setting off downhill so it may be feasible to set up several mini generatore along the way so long as they are far enough apart to allow the water to reach "terminal" speed between one and the next.
[/quote]
Velocity is not the most important component and anyhow can easily be obtained (not that you want it) by reducing the diameter of the pipe. Try putting water round a bend in a pipe at 45m/s and see what happens! You will get tremendous vibrations and cavition at the bend which will make it fail. Anything over 4m/s and you have to be very careful. Pressure is the most important factor. Once you know the pressure you can choose the pipe diameter to keep velocity low. You don't want a high velocity because then you get large losses in the pipe which will reduce efficiency (see Darcy Weissbach equation). You increase the velocity at the turbine by reducing diameter just before it. THe most efficient way is to use one machine, not a series of them. Gilkes in kendal specialise in high head turbines.
Using ram pumps to fill a reservoir to generate from would be incredibly inefficient. You would need thousands of them to generate a tiny amount of power. I doubt you would recoup the energy required to build and install the system in the first place.
I did a quick calc to see whether a small hydro scheme would be feasable at home. we had a fall of 70m and required a pipe of 500m to do it. The losses meant I only saw 2 bar at the turbine (using a 4" pipe) and the amount of power generated would be miniscule. I could imrove it by putting in a larger diameter pipe but that would be expensive and more time consuming. It wouldn't be worth it.
Lithuania have large dams for freshwater reservoirs with no turbines installed because of political reasons and nuclear power. It would be worth installing turbines there.
Lithuania have large dams for freshwater reservoirs with no turbines installed because of political reasons and nuclear power. It would be worth installing turbines there.
nickwilliams
Well-known member
Pitlamp said:
As a former science teacher, Pitlamp, you should know better! It's obvious from first principles (i.e. the law of conservation of energy) that putting a turbine directly in the stream flow will be more efficient than using the same flow to pump the water to a reservoir at the top of a hill and then putting a turbine in the outflow from the reservoir. So, if you can't get any meaningful energy out of the original flow, you sure ain't going to get it out of the secondary flow!
Nick.
