Rain Gutter Power

[Michael GilliganParticipant @michaelgilligan61133]

This series of videos touches on several topics of interest

It is entertaining and informative,

educational but not too patronising.

… A pretty good balance, in my opinion:

https://youtu.be/S6oNxckjEiE?feature=shared

 

MichaelG.

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[John HaineParticipant @johnhaine32865]

Interesting but stretched out too long. The problem with this type of item is that within a week or so there will be a rash of stories on “alternative energy” websites about how gutter power makes solar panels obsolete even though the available power is minimal. And it hasn’t rained significantly here in East Anglia for months!

A few years back there was much excitement about an innovation in solar panels that added a piezoelectric layer to generate power from raindrops, based on a very trivial press release from a Chinese university. A few minutes googling rain rate and doing some basic calculations showed again that the power available, even with 100% conversion efficiency, was at most an order of magnitude below that available from solar radiation.

[Michael GilliganParticipant @michaelgilligan61133]

I presume he’s targeted it at kids … and I thought it a useful ‘reality check’ on total cost of ownership for some of the ‘Green’ ideas.

MichaelG.

[duncan webster 1Participant @duncanwebster1]

In similar vein, quite a bit of the water we put down the drain is warm, with a heat pump we could recover the heat, more efficient than ambient air as the cold end (waste water) is hotter. Cleaning out the heat exchanger is the downside

[Nigel Graham 2Participant @nigelgraham2]

I wonder how much loss there was in those gears being meshed by a spring?

Entertaining experiment but not really a serious proposition.

[duncan webster 1]

On duncan webster 1 Said:

In similar vein, quite a bit of the water we put down the drain is warm, with a heat pump we could recover the heat, more efficient than ambient air as the cold end (waste water) is hotter. Cleaning out the heat exchanger is the downside

A good point Duncan.  Even better if it could be plumbed into a heat storage system as often the warm waste water drains when the heat may not otherwise be needed.

[SillyOldDufferModerator @sillyoldduffer]

Recovering energy from rainwater and warm water are both common.  Problem is that neither is worth doing on a small scale.  Forget domestic installations.

• The 2.5GW Robert Moses Power Plant averages 15,897,000MWh per year from rainwater.   Rain falling on a sizeable chunk of North America ends up as a more or less steady high-volume stream at Niagara Falls.
•  Recovery is economic in a large power station, steel works, chemical plant, oil refinery or similar, but the recovered energy is usually fed back into the industrial process, not sold to the public.  They prefer to keep their distance: not many fossil fuel fanboys choose to live close to a coal power station!Industrial plant often recover waste heat.

These schemes both depend on geography and customers.  Plenty of customers in Norfolk, but hydroelectric is out because there are no hills!  Norway has lots of lovely mountains, but not many customers!   Rose Cottage has a customer, but the roof is too small to catch water, and there is no way of storing it on high.

Likewise, Rose Cottage alone is unlikely to produce enough waste heat to worth recovering.   Could be made economic by collecting the waste heat from many homes, but I guess only be worth doing in a large city.

Efficiency considerations require energy production to be done on a large scale whatever the source: bigger the better.  This is true of fossil burning and renewable sources.    Coal power stations and windfarms are both gigantic

Imagining renewable energy is restricted to techniques that work at home is quite wrong.    A tiny wind-turbine on the chimney isn’t the answer, nor is rain on the roof, or heat recovered after washing up!  The reality is a 3GW windfarm comprising a few hundred turbines each with blades bigger than Jumbo Jet wings, carefully located in a windy place.   Off-shore is good!    Same with solar panels:  think a square kilometre of them in the Sahara rather than a few on British rooftops!  Ditto hydroelectric and heat recovery – they have to be big.

All this has been seen before.  When in 1690 Papin modelled a steam engine with a piston, the idea was rubbished.   Partly because it didn’t produce useful power (too small), and partly because so many fear change, preferring the devil we know to anything we don’t understand.   Savery and Newcomen took the idea forward, achieving success by building big.  Scale matters – to this day it is difficult for us to make a working scale model of a Newcomen engine.  Just the start. The efficiency of Newcomen’s engine was improved by Smeaton, and then James Watt got seriously inventive, not least by explaining to horse obsessed men, why they needed an engine at all.  Watt led to locomotives and steam turbines.  Same pattern with other technical advances.

Six things stand out:

• Ideas are fulfilled by thinking big, both technically and financially
• Many of us would rather die in a ditch than accept a new idea.   This group may rely on gut feel and experience rather than  science and maths.  If so, given gut feel is easy and maths is hard, which is more likely to be right?
• Naysayers always deploy the same arguments to explain why:  canals will be no good compared with roads;  railways will be no good compared with canals; steam will be no good compared with horses; sail is better than steam; machine made will be inferior compared to crafts; gas light is inferior to candles; electric light is bad for the eyes; oil is inferior to coal;  smoking is good for you; cinemas are inferior to music halls; TV is inferior to cinema;  cars will ruin the roads;  women will be spoilt by washing machines;  etc etc etc
• Nothing new arrives fully debugged.  There’s always a long development period and some failures, enabling naysayers to delay progress at every step.
• Despite strong opposition, most engineering innovations work in the end.
• No technology is perfect and othing lasts forever – change is inevitable.  As something always needs fixing, engineers cannot rest on their laurels.

Now then dear reader, be honest!  Are you a cynic or an optimist?    Do you think engineering stopped in 1947 with the single-phase Imperial Myford 7?  Or should British engineers be enthusiastically into Quantum Computing, Nano-technology, AI, robotics, renewable and tomorrows challenges?  There are a lot of them!

🙂

Dave

 

[Ian PParticipant @ianp]

Well put Dave

Ian P

[JasonBModerator @jasonb]

Energy recovery for the individual home has been available and has been used for some time. OK not so much generation but taking the heat out of extracted air and passing it through heat exchangers to offset some of the energy needed to heat the fresh incoming air.

Likewise a few solar panels on your roof may not cover all your usage but will go some way to reducing it.

Both these at the end of the day will help reduce energy needs however they are generated.

As for rain water you are likely to save yourself more money by storing it for watering the garden or even more if used as grey water to save on paying for fresh only to flush it down the bog. This will save energy in the long run as there is less work for the treatment plants so that is where the energy will be saved.

[Ian PParticipant @ianp]

I wonder whether (pound for pound) a high level of home thermal insulation wouldn’t save more energy overall than the two examples Jason gave.

Ian P

[JasonBModerator @jasonb]

Funny enough I was going to mention insulation as well. In the ideal world you would use a combination of all those.

[duncan webster 1Participant @duncanwebster1]

A major advantage of Jason’s air/air heat exchanger is that it reduces humidity in the house, less condensation, less potential for mould.

[JasonBModerator @jasonb]

If my maths is right then saving the water is a lot more cost effective.

 

In the video he was getting 1 watt from the two gallons per minute equals 0.06KW per hour. To make 1Kw he would need 16.7hours of rain at the same rate totalling 2000gallons.

1Kwhour lets say cost 30p.

2000gal is 9m3 of water at say £2.50 a m3 so that same rain water could save you £22.50 if used to replace tap water.

And before the pedants chip in I have not allowed for US gallons, standing charges or sewerage included in the water cost.

So Michael instead of using your new 3D printer to print one of those fancy water wheels you would do better printing a water butt, lucky your filament is green😉

[JasonB]

On JasonB Said:

If my maths is right then saving the water is a lot more cost effective.

 

In the video he was getting 1 watt from the two gallons per minute equals 0.06KW per hour. […]

My point in posting the link was that he provides an amusing but educational de-bunking of various ‘bright’ green ideas.

MichaelG.

[duncan webster 1Participant @duncanwebster1]

Jason’s units are a bit awry. A watt is one joule per second, energy per second, so power. A kW per hour would be a rate of increase of power. A few others, but perhaps I’ve picked enough nits

[Nigel Graham 2Participant @nigelgraham2]

I don’t think the chap with his little Pelton turbine imagined the output would ever be enough for more than recharging his ‘phone. Doesn’t he more or less say as much, early on?

What rather surprises me is that he didn’t try to consider some of the basic engineering problems he met, from the start, before making it. He does show a turbine needs a steady head of water, but why not fit a strainer to the top rather than a sediment-trap at the bottom; make a nozzle and constrain its position; find a more elegant way to mesh the gears (admittedly he did not realise he needed those, at first)?

 

Dave –

That turbine project was to prove you can’t run a home from rain-water on its roof; but the basic argument of small-scale devices that simply take the edge off the electricity-bill would seem sound. After all “we” already have roof-top photovoltaic panels and water-heaters, using Old Sol, very effectively indeed. As my brother proved with quite elaborate systems he built himself – and he lives near Glasgow, not Grenoble. These do not always replace the mains electricity and bulk-tank gas; but certainly contribute very significantly to the home’s needs.

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Yes, making a working model of the Newcomen Atmospheric Engine would be difficult, but not impossible. Ron Jarvis, whose model-engineering was along similar themes and quality to Cherry Hill’s, proved that – but he did use a little electric element in the boiler about the size of an orange, w.p. 2psi. Complete with “orange-peel” finish to represent the original’s hand-forging; and the pipes all of lead as prototype. Though he also wryly said this was an 18C engine with 20C computer control: the element was controlled electronically!

I knew the engine as Ron and I were members of the same model-engineering club, but sadly, I never saw it operating.

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The naysaying you describe is from all sorts of factors; but fear of change and the unfamiliar is perhaps the largest.

Railways? Capable of exceeding 30mph? We all know the human body cannot stand travelling faster than that… Where did that come from? Centuries of humans had never been able to move faster than a galloping horse can carry them, which is at about 30mph and for quite short distances. Though one must admire the footplate men of the first locomotives coping with a heady 40mph on a wet, cold Winter night with just a vertical wind-break for shelter, and crude oilskins for outer clothing. Even worse traversing the bleak Scots moors – the Caledonian Railway’s designers did not like to be too soft on the operating staff. Cabs are of steel but cost brass!

Engineering has “always” (since the Industrial Revolution) been a quest for better ways to do things. The commercial imperative for greater efficiency, in engineering sense, mattered as much to James Watt as it matters to designers now. The Tay Bridge Disaster woke everyone up to needing be better at building things: the Inquiry proved it collapsed through poor design and very poor workmanship.

No-one suggests what sufficed in 1947 will necessarily suffice in 2047; but I think Engineering has become more remote from many people’s lives because they find it ever harder to recognise, they tend to favour that waffle-word, “technology”; and both terms are so misused and abused.

Worse, as society becomes ever more reliant on Science and Engineering, those are entering realms many people find ever harder to comprehend; encouraging fear based on ignorance, hence naysaying.

 

[JasonBModerator @jasonb]

Duncan, thanks for the correction so can you say what he is generating in the way of kWh so it can easily be related to the cost of electricity. I think it may be even less than I said but a second opinion is useful.

So if the 1watt showing on his meter is 1joule per second

Then in one hour that is 60×60 or 3600joules

Online conversions to kWh gives that as 0.001kWh

so to generate 1kWh he would need 100 hours of rain fall at 120gal/hour.

100 x 120 = 12000gal = 54m3 of water

54m3 @ £2.50 = £135 Anyone want to check?

Or you could catch the water after it has been throght the wheel and save an extra 2 1/2p

 

Nigel, as he says at the end there are improvements he could make and there are several other videos in the series that cover some of those.

[John HaineParticipant @johnhaine32865]

The reason that I dislike this sort of video is nothing to do with luddism or whatever people are discussing above.  My point is about ENGINEERING.  One approach to this sort of possibility is to dive into making something which makes entertaining video with an educational point at the end which will probably be ignored.

But an engineering approach starts with the requirement, the proposed solution, the applicable data, and does some sums to see if there is any point in the approach.  That’s what we need to inculcate in people.  Only if there is some apparent feasibility might one make some sort of experimental apparatus.

[John Haine]

On John Haine Said:

The reason that I dislike this sort of video is nothing to do with luddism or whatever people are discussing above.  My point is about ENGINEERING.  One approach to this sort of possibility is to dive into making something which makes entertaining video with an educational point at the end which will probably be ignored.

But an engineering approach starts with the requirement, the proposed solution, the applicable data, and does some sums to see if there is any point in the approach.  That’s what we need to inculcate in people.  Only if there is some apparent feasibility might one make some sort of experimental apparatus.

I’m sorry you didn’t like it, John

Personally, I thought it was nicely pitched at a ‘bright kids’ demographic.

MichaelG.

[MetalhackerParticipant @metalhacker]

The entry here I find significant is the ‘grey’ water recycling. When I lived in rural Western Australia, 1m3 of water cost 57 cents or about 26p! Compare that to UK water prices, and it is the driest part of a very dry continent. We had evaporative air conditioning which works by soaking pads of wood shavings with waterand sucking air at high volume through it. This water was recycled through the system, but gradually got more and more Saline which recuced the efficiency and increased corrosion of the moving parts. The solution was to connect the drain from the air confitioner to the input pipe of the toilet flush. The water was therefore used twicw and saved both corrosion and money! Not my idea but certainly effective lateral thinking!

Andries

[Nigel Graham 2Participant @nigelgraham2]

John –

He did approach the project in the way you suggest – very simply and informally, yes, but including calculations.

So on that definition it was an Engineering experiment.

The flaw perhaps is this approach was not stressed as good engineering practice, though it’s not really clear at whom the video was aimed. Probably not an audience like us, who would have gone into it a lot more thoroughly before carving up our valuable stocks of aluminium chequer-plate. So had he presented it more formally, he would no doubt have lost many of the intended viewers even before calculating the theoretical torque on the turbine.

[JasonB]

On JasonB Said:

Duncan, thanks for the correction so can you say what he is generating in the way of kWh so it can easily be related to the cost of electricity. I think it may be even less than I said but a second opinion is useful.

So if the 1watt showing on his meter is 1joule per second

Then in one hour that is 60×60 or 3600joules

Online conversions to kWh gives that as 0.001kWh

so to generate 1kWh he would need 100 hours of rain fall at 120gal/hour.

100 x 120 = 12000gal = 54m3 of water

54m3 @ £2.50 = £135 Anyone want to check?

Or you could catch the water after it has been throght the wheel and save an extra 2 1/2p

 

Nigel, as he says at the end there are improvements he could make and there are several other videos in the series that cover some of those.

Take an average house, say 8m (315 in) square. The average annual rainfall in UK is 1.4m (55 in), less in East Anglia, more in mountainous regions. This is 8 * 8 *1.4 = 89.6 cu.m (5467727 cu.in). Density of water is 1000kg/cu.m, so this is 89600 kg (197534 lb). The force applied to this mass by gravity is 9.81 * 89600 = 879000 Newtons. The height to the gutters is say 5m so the total energy available is 5 * 879000 = 4394880 Joules (197534 * 197/12 = 3242850 lb.ft). This sounds like a lot, but 1 kWh for a year is 31536 megaJoules, so the equivalent constant power output is 0.00014 kW.

This is why hydroelectric schemes ideally have huge upland catchment areas and a long drop down to the turbines. Maentwrog station has a catchment of 38 sq.km (14.5 sq miles) and a fall of 190 m (630 ft). The rainfall in that area of North Wales is 3.67 m ( 144”)

Using existing weirs on rivers is a far better bet than house roofs, Woolston on the Mersey has a capacity of 520 kW delivered by three Archimedean screw turbines using the flow of 30 m3/s in total and can generate nearly 2,300 MWh of electricity per year. The weir was already there. Similar schemes have been proposed but not implemented on the Weaver navigation and the Thames at teddington

[JasonBModerator @jasonb]

This popped up on Pinterest this morning, you would need a reasonable bit of rainfall for that one

[Metalhacker]

On Metalhacker Said:

. When I lived in rural Western Australia, 1m3 of water cost 57 cents or about 26p!

For those not on a meter – SW Water charge me $2.07 per M3 but then assume it all goes as sewage for which they charge £3.32 per M3. Plus standing charges of £8 per month. Strong incentive for rainwater flushing. And solar heated rainwater shower.

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