The set up

The set up
5.36mm jet delivering 0.63 l/s to the pelton which is rotating at 870 rpm and generating 127 watts into the grid.

Monday, 1 October 2018

End of year results: 2018

The end of September marks the end of the 12 month interval I use to report annual generation. September and October are the driest months of the year and for neatness of display in a graph, it is convenient to have a "water year" begin and end when output is at its lowest.

Close scrutiny of the three graphs below reveals all that is important for learning how productive my installation has been.  All three graphs are derived from the same raw data and that data is a record of the number of kilo-watt-hours (kWh) generated each day.  This data is captured automatically by the SMA inverter, transmitted wirelessly to an SMA Sunny Beam and downloaded each month from the Sunny Beam to my computer.

In each graph, the bold black line represents the results for the 2017-18 "water year" which has just ended.  Previous years are shown for comparison.


  • With a total of 3816 kWh generated, it has been the second most productive year so far.
  • The year started slowly with less energy generated than previous years up to the end of December
  • From December onwards output then exceeded previous years through until mid-May
  • From mid-May onwards, output fell to being less than most previous years
  • The good output between December and mid-May was achieved through peak generation hitting just in excess of 900 W whilst in previous years it had not exceeded 800 W
  • This higher level of generation was made possible within the limits imposed by my abstraction licence by knowing with greater refinement the volume of water the turbine was actually taking and operating it to within the upper margin of error intrinsic to the way the volume imposed by the licence is calculated. 
  • The volume of water extracted for the year totalled 45,791 m3.  My licence limit is 49,982 m3.
  • Capacity factor for the year was 58% (using as datum the design power of 750 W; calc: 3816*100 / [0.75*24*365] )
  • Availability factor was 100% (non-availability of the turbine for generation, whatever the reason, never exceeded 4 hours in any day; I only count whole days as being an impairment on the availability factor).

Monday, 27 August 2018

Blast through time

It's that time of year when once yearly maintenance jobs need to be done, and de-silting is one of them.  This year I devised a new way of blasting through the penstock without having to take the turbine off its plinth:

A galvanised union, barrel nipple, 90 degree elbow, and a short length of threaded pipe, each in 2" size, were all that were needed. The union screws on to where the jet sleeve has a thread for the nozzle retaining cap.

With the head tank de-silted and the penstock as clean as a whistle, I'm ready now for the best possible level of generation in the coming 12 months.

Sunday, 12 August 2018

Policing water abstraction

Yesterday the abstraction police descended on me: Saturday morning, unannounced, in an unmarked vehicle and brandishing paper copies of my abstraction licence.  The intent was clear: to catch a criminal in the act of transgressing the terms of his licence.  Is it just me who gets irritated by such tactics ?

I was irritated from the start, and that was a shame because the Natural Resources Wales (NRW) policeman who came to make the inspection was a decent fella, with a wife and child, worried about the security of his job with NRW, and with an interesting career before joining NRW. But we got off on the wrong foot with each other, largely because the circumstances of the unheralded visit made me resent being treated as a neo-criminal. Not just that: there's a long standing sore dating from when I first applied for my abstraction licence which has yet to heal.  I still feel hard done by and am left nursing a grievance that NRW as an organisation fail to properly engage with clients. 

With the decent fella however, toward the end of his visit, bridges had been built.

This is the third inspection I've had and each time it's someone different.  No continuity which might make for a fruitful discussion with someone who knows the site from a previous time.  So he was seeing it afresh.  Everything needed to be explained. Queried. Photographed.

There really ought to be another way, a better way, of doing this sort of compliance visit.  Most of us who have small hydro sites are people who are environmental enthusiasts.  We're not going to be trashing the water courses of Wales or draining them dry from over-abstraction. And in any case, the damage possible from such minnow schemes as mine hardly makes it justifiable to do a compliance visit every year.

NRW have more important things they should be addressing: they still haven't managed to sort out a reporting system for hydro abstractors to give their annual readings on-line.  It's been banded about for over three years, launched and failed twice and still hasn't seen the light of day. 

It's a question of priorities: finances are tight so they need to deploy wisely what little they have.  Not happening at the moment though !