The set up

The set up

Monday, 8 August 2016

Grievances with NRW.

In the past couple of weeks I've been having a dialogue with a very nice lady at NRW. NRW stands for Natural Resources Wales.  It is the body in Wales responsible for issuing and regulating licences for water abstraction.

In the UK, we call such a body a "quango", - an acronym for quasi autonomous non-governmental organisation.  A quango has power to set and enforce legislation. The disconcerting thing about the power possessed by a quango is that where such legislation is later shown to contain glaring anomalies amounting to abuses which arouse protest, yet can the quango close its ears and say that such abuses are in the nature of things so must be accepted without demur.

Ordinary people like myself, coming into contact with NRW for the purpose of getting an abstraction licence, may perceive these wrongs; may perceive that an injustice is being imposed; and this creates a feeling of resentment at being unfairly treated.  Yet the deafness of the organisation makes it impossible to get even a hearing, let alone redress.

The particular matter which has been the subject of my dialogue concerns the imposition of a charge for the water I abstract.  Water abstracted for the generation of electricity does not attract a charge. Neither does water abstracted for domestic use, so long as the volume is less than 20 m³ per day. Yet if these two abstractions come from the same place, the way NRW has written the rules makes it compulsory to 'aggregate' the two volumes and aggregating inevitably brings the total daily volume to greater than 20 m³. Such a volume now triggers a charge; in effect: two abstractions, each on its own free yet together being made not to be free !

There have been other injustices in NRW's self written rule book which I have drawn attention to before. Let me mention two again:

1. - in this third year of operating my Powerspout I am going to generate over 4000 kWh of energy.  The volume of water I have abstracted to generate this is calculated by applying a 'hydro-abstraction factor' (HAF). For my site this is 13  per kWh; To have generated 4000 kWh I will thus have abstracted in excess of 52,000 m³. This is more than the limit set by my licence (49,982 m³) and yet I have generated this number of kWh's, an exceptional number for me, only because it has been an exceptionally wet year;  the instantaneous flow abstracted and the daily volume abstracted, figures for both of which are also stipulated on the licence, have not been exceeded.  

The injustice here is that it is inconsistent for a licence to set both a daily limit and an annual limit; there is no knowing when one applies for a licence how many wet days there will be in future years, so making prediction of an annual limit impossible. All that should matter to NRW with its concern for harm to the watercourse is that the daily limit is not exceeded. It ought to matter not at all to them if a year happens to be so wet that water is plentiful enough to allow people like myself to generate an exceptional number of kWh's.

A subsidiary point to be made about the yearly volume, if indeed there has to be one, is that it is mathematically amateurish to stipulate a figure which purports to be more precise than the accuracy possible from the method used to calculate it.  My licence, instead of saying 49,982 m³ would better have said 50,000 m³, and better still from a mathematical standpoint, should have added an error allowance of, say, 10%, acknowledging the calculation method can sustain no greater accuracy than this. By allowing some measure of flexibility then at least licence holders would be saved the anxiety of overstepping their limit in occasional years.

2. - in describing the way to calculate one's HAF, NRW say that the component efficiencies of the different parts of the installation 
at maximum power
must be used.  To say this is unscientific and subtly over calculates the HAF by the effect of two linked factors: 

  • 'run of river' hydros in Wales will never operate at maximum power throughout a year
  • efficiency, at least for a pelton, is not very good at maximum power
It would be better to calculate the hydro abstraction factor either from the efficiency at the flow which predominates through a year (the mode flow value) or, and this would be being generous to the licence holder, at the flow where the installation is most efficient.

These points of grievance are highly specific.  They refer to arcane detail which is not for everyone. There is however another matter of grievance, which requires no knowledge of obscure detail, is relevant to all hydro owners and reaches to the deepest level. It has been the subject of a long running argument between NRW and the two organisations in the UK which represent owners of small hydro installations, the British Hydropower Association and the Micro-hydro Association. 

It is the argument about how abstraction for electricity generation should be treated; the proposition that abstraction for the generation of electricity should not be treated as abstraction for other purposes because the one permanently removes water from a watercourse whilst the other does not; that the principles, right and proper principles as they are which guide NRW in wanting to restrict and have control of the removal of water from Wales' water courses, need to be modified when applied to abstraction for electricity.

Unfortunately for hydro owners, the response of NRW so far has been characteristic: the organisation has been unwilling to engage on the issue.  In like manner I have had no real engagement on the particular grievances I have put forward. Such is the typical quango stance.

Who in an organisation like NRW are those responsible for the conduct of the organisation ?
Certainly it is not those like the lady I have been corresponding with or the two NRW field workers who paid me a visit two years ago, all of them open and approachable people but people who are necessarily constrained to work within the legislation that NRW has itself devised. What needs changing is the legislation itself.

The people at the top who sit on the board are the ones who carry the responsibility for the image the organisation conveys.  As it happens, I am familiar with a few of them ! One is a micro-hydro owner who lives near to me and whose installation I have visited. With two others I share the experience of having been a senior employee of the Welsh Health Service. 

Come on you board members ! - ensure NRW puts in place mechanisms for real consultation on matters of grievance concerning your legislation.

Why not have a board member who acts as an internal 'ombudsman', to whom grievances about your legislation can be addressed ? Your complaints procedure specifically excludes using the complaints route for legislative change.

Wednesday, 3 August 2016

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 that which anyone can view by clicking on the "Live power" link on the right of this blog.

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 an actual variation in power output.

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 !

Sunday, 17 July 2016

Thoughts about water storage

Some considerable time before I installed my Powerspout, when I was still trying to decide if it was a scheme worth proceeding with, a friend who had much experience with hydro came to walk the ground with me.  He advised creating a bit of water storage.

At the time, I wasn't very sure what he meant. I assumed he meant digging a sizeable reservoir.  The nature of the terrain made this an impossible proposition so I was left wondering about his advice, - when he was with me, I didn't like to show my ignorance by asking him to explain !

Gradually I came to realise why storage is valuable, - not to provide a huge volume in the hope of extending generation into the dry months but just a small volume to facilitate day-to-day operation by buying time before action needs to be taken to match outflow to inflow.

How valuable such a buffer proves to be depends to a considerable extent on the behaviour of the flow one is capturing, - and operating a small hydro certainly brings you into an intimate understanding of the behaviour of your particular water source. 

Such understanding comes slowly.  After three years I am still getting the measure of how, as summer progresses, the flow initially drops off quite quickly but then slows down in its rate of decline.  Plotted on a graph, I think it would be an exponential curve. 

Another fragment of this understanding is that a bit of rainfall in the summer makes little or no difference to the rate at which flow falls off.   Yet another fragment is that when winter rain starts, it takes several weeks before the flow begins to pick up, but when it does pick up, it can pick up very quickly indeed: in my 2014/15 water year, flow went from 1.18 L/s to my maximum of 3 L/s in the space of just one week.

With a source like mine which, when it is diminishing, changes only slowly, my 5 cubic metres of tank storage means I can wait several days, even a week, from the time when the tank stops overflowing to the time when I need to step in and change to a smaller nozzle. Only because of this behaviour am I able to operate as a 'variable head' site, as described in an earlier post.

But for a different site where the flow is more 'flashy', by which I mean the flow rises and falls rather quickly in response to rain falling, even my generous 5 cubic metres of storage would be inadequate to operate in such a way. It wouldn't buy enough time, wouldn't provide enough of a buffer, before a nozzle change were to become necessary.

So the merits of putting in a tank at the top of the penstock, and the size of it, really depend on the site hydrology.

EcoInnovation has recently published a very good document about constructing intakes for their Powerspout turbines. It can be found here.  In it, mention is made of the benefits of providing storage and it is well worth reading if you are at the stage of wondering about putting in a turbine.

To illustrate how a storage tank can be sited relative to the take-off point from a water-course, here are some pictures: