Generating in a drought

The drought of 2026 in the UK is going to be remembered for a long time and in spite of no rain for 2 months my Powerspout is continuing to generate.

The flow available has dropped to half a litre per second (0.53 l/s) but that small amount at a head of 53 metres and an overall efficiency of 40% is enough to make 111 Watts (2.66 kWh per day).

0.53 l/s pictured today being strained of trash before dropping into the header tank.

The onset of the drought can be seen graphically from daily energy output declining from March onwards:

Rainfall had been unusually heavy during the five months October to February, totalling 944 mm which is not far short of the total rainfall expected for 12 months. Yet in spite of this generous topping up of groundwater in the hillside, the water issuing from the spring fell off steeply from mid-March onwards.

In many years, the month of June sees a good amount of rainfall, what I call the 'June Monsoon', but in 2026 it didn't happen and the decline in yield from the spring continued inexorably.

Happily though, the rate of fall in spring water yield seems to have flattened off after May and from experience I know it will be quite likely that even with no rain falling, the 0.53 l/s issuing at the moment will continue to be available for several weeks to come. 

The reason for this ongoing yield of water, with no rainfall to support it, is that the geology of the hillside above is a type of rock called Old Red Sandstone. It is a rock which can take up and hold prodigious volumes of water with the result that the yield of its springs is largely unaffected by droughts of just a year's duration.

The nozzle I am using to deliver a flow of 0.53 l/s is Roman numeral II in my numbering of nozzles. I have been curious to observe how good the efficiency is with this smallest of nozzles because efficiency always drops off at low flows. 

It turns out Nozzle II is giving a respectable efficiency of 40.1% and that is not bad. For reference, the best efficiency I get is 56.4% which happens when flow is between 2.30 and 2.74 l/s.

To know efficiency for your hydro scheme, you need to know accurately two parameters: output power and flow.

The new monitoring system I installed in January of this year (see previous post) allows me to know power very accurately indeed.  The meter measuring it is one accredited by the UK's Measuring Instruments Directive (MID), which means it is in a class of meters accurate enough to be used for billing purposes.

The power output trace from this meter for nozzle II today, over one hour, is shown in the picture below:

The meter is so accurate that it records the 'hunting' of the Powerspout's inverter as the inverter seeks its 'set point'. 

This is seen as the saw-tooth pattern in the power output trace. 

The 'set point' it is seeking is determined by the inverter measuring incoming dc voltage from the Powerspout's Smart drive alternator and then trying to deliver the output, in watts ac current, that its 'table', - stored in memory in the inverter, - tells it is the appropriate power output for the incoming dc voltage.

But like all control systems which change what they're controlling, it continuously overshoots and undershoots its set point and fails to give a straight line.

You can see that the time in takes to complete one full cycle of this unwanted oscillation, - what is called the 'period', - is between 5 and 10 minutes.

Before I installed this MID accredited meter, because of this oscillation I had difficulty measuring power output accurately, but now calculating efficiency correctly is easy using the MEAN power output, which can be read in the red oval. 

It is 111.8 W.

Another thing I've learned from this spell of using Nozzle II is that my previous obsession with keeping rpm (revs per minute) close to the optimum rpm for my pelton (1000 rpm) has been wrong.

I used to keep rpm high by packing off the alternator rotor. 

In fact I packed it off so much that rather little of the shaft's splines engaged in the plastic splines of the rotor, - and this led to rotors being damaged.

What I've learned now is that whatever gain in efficiency might result from having the pelton operate near its optimum speed, is counteracted at least as much by a loss of efficiency in the alternator because of impaired flux linkage between permanent magnets and stator cores.

So the efficiency I'm seeing now with Nozzle II, the respectable 40.1%, is actually obtained with little packing off and with a resulting rather slow rpm, - just 742 rpm .

This slow rpm can be seen in the concluding pic below, where the splash pattern of water exiting the pelton cups is way off to the right. At the optimum rpm of 1000 it is at 6 o'clock. Note that only the bottom jet is in use.

Turbine on 19 August 2026, on 0.53 l/s of water, at 742 rpm, generating 111.8 W to grid.

To round off this blog post, I have to admit that with such a memorable drought happening, it amuses me that I can still be using water to generate a bit of electricity. 

Long may it continue !

A new on-line monitoring system.

Home energy systems need to be monitored; they need to be monitored not least because it is satisfying to know how much energy you are producing and how it is being used, but also because monitoring can be critical in picking up small problems before they become big problems.

In operating my Powerspout, since it was commissioned I have relied on the on-line visibility of the power being produced to know when to change nozzles. As the header tank begins to empty so the power generated begins to drop, - not by much, only by about 5 Watts. But it is enough for the downward trend in the data seen on my iPad to tell me I need to change to a smaller nozzle.

With this being a key observation for me to run my scheme efficiently, imagine my consternation when, at the start of 2026, the company which had been hosting the output of my turbine, decided it was time to close down the service they had been giving. Suddenly I was in the market for a new system to replace what was no longer available.

This blog is about the new system I found. I am enthusiastic about it and want to make known the company marketing it in case others might be interested in following the same path. If you click where it is written "Live Power and Energy" on this blog page, you'll see the new 'Dashboard' provided by the company. It displays the power and energy being produced by my Powerspout in real time and is updated every 10 s.

The hardware capturing my Powerspout's output.

The system is provided by OpenEnergyMonitor.org. The company provides all kinds of monitoring, from simple systems like mine where there are only two data feeds, power and energy, to whole house systems where feeds can come from solar generation, individual house loads, room temperature sensors, EV chargers, heat pumps and more.

The company is based in Wales, UK and when you buy products from them the deal is that 20% of the value of what you've bought is credited to you against the charge for them hosting your data on the web. Each feed you sign up to costs GBP 1 per year (excluding VAT, 1.20 with VAT). The cost of the kit I purchased was GBP 345 excluding VAT, and has therefore given me credit of GBP 69. I have two feeds at a VAT inclusive cost of GBP 2.40 per year, so that gives me 29 years worth of web hosting included in the cost of buying the hardware (calc 69/2.4). 

The guys behind the company are super helpful. I received much help, willingly given, to get my system up and running. Being an 'open source' data handling enterprise, if you have the computer skills to set things up yourself, then so much the better. I don't have those skills but with their support, all went smoothly.

The 'dashboard' accessed via this blog page is the way of publishing your data for anybody to view it, but it is not the only way of accessing your data. From the account you open with OpenEnergy when you purchase from their on-line shop, you have secure access to the raw data of your system, and you can make graphs, choose time frames and make downloads. It is a very versatile platform and much better than what I had before. The picture below is an example of how detailed the view can be of the power coming from my turbine.

A detailed, more granular view of the power output in Watts from my turbine.

Here in Wales, the rain is incessant. Last month I recorded 271 mm. That makes January 2026 amongst the top 5 wettest months in the 12 years I've been keeping records.

Of course, it's good news for electricity generation. It has been the month where we have used the least energy from the grid ever, just 12.6 kWh.

And the revenue earned in Feed in Tariff (GBP 267) has contributed most of the cost of my new monitoring.

Happy days !

New live data link

Note added 22 September 2023

This link has been removed because the Bluetooth data transmission on which it worked interfered with a new battery storage system installed later.

I've added a new link to this blog which takes you to a Live Power and Energy web page displaying the outputs of my hydro AND solar generation, combined in one display. 

Before long, I hope to be able to add battery storage, and this link to SMA's SunnyPortal platform will be able to display battery data too when that becomes available. 

Creating the link has been possible by tracking down a WebBox which was for sale in Australia; the WebBox is an obsolete SMA device, obsolete since 2016, - which works by picking up the Bluetooth communicated data from the two inverters and making it available over the web on SMA's SunnyPortal interface. 

My new WebBox was commissioned on 9th March 2023 and therefore only displays data from after that date.

On holiday but in touch.

I've just been away on holiday, - and owners of Powerspout turbines have decisions to make when they go away.

Those lucky enough to have a water supply which is constant can decide without thinking: - the turbine can be left running. But for those, like me, who have to change nozzles, planning is needed.

One option would be to shut down the turbine, but that would mean missing out on useful generation; an empty house still uses electricity and it's nice to know the hydro is meeting that demand.  Besides, I've set myself the target of generating all through each year without any breaks, and that means I don't come close to considering shutting down.

The alternative then is to keep going, and this is where it gets tricky; my crystal ball has to be dug out so I can gaze into the future to make a prediction about how much water is going to be available while I'm away.

The reason for this is that Powerspouts have nozzles with an orifice size which is fixed, and they are not automated in any way; many small hydros are automated; they have a nozzle orifice which is variable in size and can be adjusted dependent on how much flow is available, the flow being sensed by the level of water in a tank at the top of the penstock.

People can, and do, automate their Powerspouts along this line but keeping things simple is the line I prefer to take.

So the exercise with the crystal ball is to discern what size of fixed nozzle to leave the turbine with, which will still, I hope, be the right size for whatever is the flow at the end of my time away.

The things to look for in the crystal ball are recent rainfall, time of year, anticipated rainfall, temperature, and vegetation cover in the catchment area of the water source.

It doesn't much matter if you compute everything and get it wrong; if the flow dries up more than you thought it would, it's not a disaster.

What happens in my set-up is the head tank empties, water coming into it immediately goes out again down the penstock, setting up a new operating head somewhere down the pipe. This lower level of head ensures flow through the nozzle is less and the end result is a new equilibrium is reached where water arriving equals water leaving.

The operating efficiency of the system is rubbish when the turbine runs like this, - it labours at a much too slow rpm and power output is greatly reduced, - but the system does manage to keep generating and no damage is done.

Because of the technological wonders of the age we live in, there is no need to be in ignorance of how your turbine is doing while you're away. The photo shows that at the top of Carn Llidi in West Wales, I could check to see if the crystal ball had spoken truthfully.

In fact, when I got home I discovered it had not; far from drying up, 5 inches of rain had fallen in the ten days I was away; I could have been generating twice as much as the 220 W I set the turbine up for.

I need to get a new crystal ball !

Pictured yesterday...

Yesterday was a perfect cloudless day, - giving near maximum photo-voltaic output (19.54 kWh) on top of maximum hydro output (20.92 kWh) : total 40.47 kWh.  This concurrence of maximum outputs only happens at this time of year when water flow is still good and the sun sufficiently high in the sky to make the pv panels give close to their full rated output.  It also helps that the air is still cool, which boosts the output from the pv panels.  

For those discerning enough to note it, the asymmetrical shape of the solar output curve is because the orientation of the panels is ESE, - and they are located in the northern hemisphere.
😊

Meter deviousness

The 'big six' electricity companies in the UK understandably get concerned when they see from their records that a customer's bills have suddenly become smaller.  If they see that decrease in their income to have coincided with the installation of a 'micro-renewables' at the customer's premises, the conclusion they come to is: the supply meter must be being made to run backwards when energy is exported to the grid.

Such has been the accusation levelled at me in this past week by SSE (Scottish and Southern Electricity).

It is completely reasonable that SSE should want to investigate when they think such a situation has arisen, but the somewhat irritating thing is the way they go about it.  Instead of writing to say what their suspicions are, they say this: "we have come to know that your meter is incompatible with the  micro-renewables system that you have had installed. On a regular basis we extract data from flows that are sent between ourselves and your local network operator. It was highlighted on this report in January that we have come to the knowledge that the meter at your property is incompatible".

Part of the reason why they write such utter nonsense is because the government in the UK has set a target of having 'Smart meters' installed in all domestic premises by the year 2020.  The onus for meeting this target is upon the "big six" electricity companies. So given a situation where they think a meter is running backwards, rather than saying so they just say "your meter needs to be replaced".

From a consumer's point of view however, having an old-style meter replaced by a Smart meter carries implications, - possibly quite major financial implications affecting the income he gets from his "micro-renewables" installation.  This comes about because a Smart meter will measure precisely how much energy is exported, so instead of export payments being based on "deeming", they will come to be based on a metered reading.  For a Powerspout owner where deeming is reckoned at 75% of generated kWh's, this will mean a severe reduction (read here for more about why).  And for people who have any of the devices (such as an Immersun or a SolarCache) that divert surplus energy to alternative loads within the home, - again Smart metering will be a hit on the income they receive from that part of the Feed-in-Tariff which comes from the export payment.

Now SSE is, in my opinion, a good company.  I have held them in high regard ever since they helped with the installation of a 300 kW hydro at a small hospital in Uganda where I used to work (see here).  So when I took up my pen to object to having my meter replaced, and to object to the manifestly fabricated evidence they put forward for replacing it, I did so with a feeling of respect.

The incontrovertible weapon I have for resisting is that my meter does NOT run backwards. So if that argument is their sole reason for insisting on replacement, - their case fails.  If, on the other hand, they were just using that as a Trojan Horse argument in order to get one more old-style meter replaced by a Smart meter to help meet the 2020 target, then they will have to think again.  Although the supply meter at my house is the property of SSE, any change to the installation needs to be made with the agreement of the customer, - and from me that is not likely to be forthcoming.

Post script added 21 Feb 2018: an interesting, if trifling, point of detail came to light after writing the above entry when SSE sent another email explaining why they were so insistent about my meter being able to go backwards. They had the wrong entry in their records for the type of meter I had. They had it recorded as Type C11B2A-R, - which is to say lacking the "H" at the end (see photo below). Apparently the 'H' is all important: lacking it means the meter can go backwards; having it means it can't. So now we know !

More on monitoring

Over a year ago, I was contacted by a Meter & Monitoring Services company who were keen to add a hydro installation to the range of sites they were already monitoring.  At the time, I couldn't see that the data they collected, or the way they collected it, would add to what I was doing before.  But one year on I'm rather impressed by their system.

Their set up involved installing a second energy meter in series with my existing kWh meter;  the new meter collects and stores generation data and once per 24 hrs transfers it over a mobile phone link to my 'account' held on a central server; by logging into this 'account' I can view all the data and down-load both the raw data and the graphs which the data make possible.

'Smart' meter and circuit diagram in the required G83 format

This is the record of generation since 1st Oct 2015 to today 31st Jan 2017 as logged by the system:

...the vertical scale shows kWh generated per day; a point of note in this record is how little generation there has been in Dec / Jan 2016/17 compared with 2015 /16; the present daily yield is just 8 kWh per day whilst last year at this time it was 18 kWh, - testament to how dry this year has been.

The advantages of this system compared with what I was, and am still, doing are that it is automated, more accurate and more secure.  My old system takes data from the inverter (which is less accurate than this 'industry standard' energy meter); requires me to take it manually each month (whereas this needs no human input); and requires me to keep it on my computer (whilst this system uses 'cloud storage').

All in all, I think it's quite a useful addition to the way I monitor my Powerspout... especially since for me it's free, - though that might change. But take note - it does require mobile phone reception.

Live power feed

I find it useful having a display on my computer of how much power my Powerspout is producing.  Many times a day, when doing other stuff on my desktop, I'll check to see what the output is. It saves a walk downhill to the turbine or uphill to the header tank, - though I do those as well !

The data stream I view is the same as anyone can view by clicking on this "Live power" link.

Viewing it often as I do has thrown up observations which make me curious as to what I'm seeing. In this diary entry I want to write about these.  I am, after 3 years, still reaching for explanations for some of them.  

The output should in theory be absolutely constant. And mostly it is, as this record shows, captured just now as I started writing.  The variation of 1 watt either side of 216 W simply represents the limit of the system's ability to resolve and display the true reading; the base line is dead flat for 7.5 hours:

But the record is not always a flat line like this. Earlier in the year, I captured this record showing how a change in temperature in the SmartDrive housing, created artificially by blocking or allowing ventilation, made the power output anything but a flat line. As can be seen the baseline dropped 20 watts with the compartment warming up and rose again when it cooled down:

Discussion about this 'temperature effect' can be found on these blog pages.

Recently, I think I've come to understand what's going on in another type of record I see almost every day.  Unlike the fluctuation caused by temperature, which is a genuine change in the power output of the Powerspout, this one is only an apparent change.  It arises from the way in which the monitoring system works and not from a real variation in the power being put out.

An example can be seen in this trace from last week:

What is noticeable here is that output is dead level between midnight and 06.00 hrs, and dead level again between 20.00 hrs and the following midnight. In between these times it appears to jump around all over the place.  This in-between time is day-time, the time when activity in the house is causing most electricity to be used. It is also the time when my solar panels are working, putting their output into the grid via the house consumer unit.  Could it be that the level of energy consumption in the house and the output from my solar panels have an effect on the display of hydro generation?

I think the answer is yes and the explanation is twofold. It lies in understanding the way the hydro monitoring gets its data and what happens to mains voltage when household consumption is high or the solar panels are generating.

The way the live power feed gets its data is from the frequency of a pulse taken from the installation's kWh meter.  The meter is calibrated to give 1000 pulses per kWh.  The parameter which the meter actually measures to give these pulses is current.  It doesn't measure voltage, which is the other parameter necessary to give an energy reading.  It just assumes that voltage will be constant, and for my Elster meter it assumes 230v.

Now in reality, house voltage is never quite constant at 230v. It varies slightly up and down from this value as a result of fluctuations in voltage in the main grid network; in addition to these fluctuations there are further fluctuations contributed by voltage drop over the supply cable from grid to house, and these will be dependent on how much power is being taken moment by moment.  So the voltage seen in the house actually varies significantly through the day, going down as power consumption goes up, but going up if there is much solar input.

What this variability in voltage means for the display of live power is that what is, in reality, a constant power output now appears to be not constant; and it mostly appears to be not constant in daylight hours because that is the time when the factors causing disturbance to voltage are most prevalent. It appears not constant because when the prevailing voltage is less than the meter's nominal 230v, the current the meter will measure will be higher by as much as the voltage is lower; since the meter measures only current, and this current measurement alone is the source of the frequency of the pulses on which the power display relies, the result will be an apparent upward blip on the power trace.

Conversely, transient or sustained voltages above 230v will cause downward blips and troughs.

It is only because the sensitivity of the system which is measuring live power is so good that such fluctuations in voltage can be seen to have any effect.  For all practical purposes, they matter not at all !

A workaround for monitoring problems

The on-line 'Live Power' feed is back up again.  However it is reading exactly double what the true output is: the problem was too weak a signal and my workaround has been to put two current transducers in series on the wire from the inverter. 

Better to have a reading than no reading !

Monitoring problems

Generating at flows lower than I have been able to generate at previously is creating problems with my monitoring systems.  For the moment, I haven't been able to quite understand why this should be, but a result of it is that I have removed the feed to the "Live Power" tab on this blog because it was giving wrong readings.

Having an interest in closely following the output of my installation, I monitor output in different ways. Some are convenient but not very accurate whilst others are inconvenient but more accurate.

The convenient, 'at-a-glance' system relies on a Wattson monitor with its feed going also, via a Wattson Anywhere hub, to the web. It is this system which is playing up: when the turbine is happily putting out 160 W, the monitor and web portal sometimes show zero.  As can be seen from the online trace below, it suddenly dropped to zero at 17.00 hours on Thursday even though the turbine was in fact OK:

As a backup to Wattson, I also monitor using the blue tooth output from the Sunny Boy inverter : SMA's Sunny Beam system.  This is not quite so much 'at-a-glance' and it is not quite as accurate, but it does have the benefit of being able to store several months of data.  The Wattson display can also store data but only about three weeks worth.  If you don't remember to download the data to your pc within that time, it starts overwriting and readings are lost.

The final system I use, which is the most accurate, is the kWh generation meter used for submitting readings for Feed in Tariff claims.  One can use this as a way of measuring power output by noting the exact moment in time when its decimal place updates and then doing a calculation based on the increment in kWh and the precise time interval to achieve this increment (measured in seconds).  I usually do readings over at least a 24 hour period and, of course, to be valid, there should have been no change in the turbine's output during this period.  Since multiple 24 hour readings give values for power which are within 0.5 W of each other, I think the method is accurate enough.

Unfortunately, this meter too is proving inaccurate at low flows - something which Elster, the manufacturer, makes clear will happen when the current flowing is below 0.5 A.

None of this matters very much except that it's introducing error into my on-going study of 'whole system' efficiency at low flow.  In truth, there are probably so many other inaccuracies, especially knowing precisely what the flow is, that this added error will probably not matter very much.

The usefulness of a head level sensor

Over the past ten days we've had a fair amount of rain and I've been gradually "upping" the nozzles to make the most of the increasing flow as it becomes available.

This morning at nine o'clock, I "upped" from a nozzle combination which delivered 2.47 lps to one delivering 2.78 lps, - but it was too big a step to take.  By midday, the header tank had stopped overflowing, the 'spare' flow falling over the quarry face below my catchment site had reduced to a trickle: 

...the online trace of live power showed a falling level of output as the water level in the tank fell:

...and the level sensor sited in the connection pillar by the turbine registered that the tank was 150mm below being full:

I relate all this to illustrate two things:

1. How much more useful it is having a head sensor at the top of the penstock compared with just having a pressure gauge at the bottom. Powerspout provide such a gauge in the kit of parts which comes with each turbine and it does have its uses.  But the pressure gauge for my site was calibrated to a full scale reading of 750 kPa, which is about 76 metres head of water.  There is no way it could have conveyed the relatively miniscule drop in pressure described in the above situation.

The head sensor is very simple: it's powered by three 9v batteries, which need replacing at yearly intervals.  It's connected to a pressure transducer at the top of the penstock, by a 3 core, 1.5 mm², SWA* cable running alongside the penstock. The pressure transducer sits in a vertical pipe, where the water is still and not flowing, with its reference mark exactly 1000 mm below the water level when the tank is full.

This vertical pipe also acts, incidentally, as a vent to let air out of the pipeline when filling it, and air into the pipeline when emptying it.

The sensor was provided by SCS Ltd, a company making turbine control and grid connection equipment for micro-hydros bigger than Powerspout size.  It's a manually operated version of the sensor they use to regulate the flow to a turbine by servo control of its inlet valve.

2. How handy it is to have a good amount of water storage: despite 3 hours operation during which flow out from the tank has exceeded flow in, the tank water level has dropped only 150mm and the turbine is happily still putting 714 W into the grid.  

From the power trace above, it looks as if the water level may have stopped dropping: the trace from 11.30 onwards seems to have levelled out, meaning inflow and outflow may have come into equilibrium.

All this being so, I am not going to rush to reverse the nozzle change I made this morning.  The weather forecast is for more rain, albeit not very much, and my hope is that the yield will pick up sufficiently for me to keep operating with the present nozzle combination.

Perhaps this account will convey something more than I initially intended, which was just to say something about the level sensor.  It will, doubtless, also convey that a micro hydro needs supervision, at least on days like today !

* steel wire armoured