The set up

The set up
5.46mm jet delivering 0.68 l/s to the pelton which is rotating at 900 rpm and generating 135 watts into the grid.

Thursday, 6 July 2017

14,448 hours

A couple of days ago I noticed the Powerspout wasn't sounding right. Here is an audio clip of the shaft coming to a stop after shutting off the flow.

The bearings have not been changed since 10th November 2015 and that's 14,448 hours ago. The turbine has run continuously for all of that time bar stoppages for nozzle changes and one de-silting of the header tank.  Clearly the time to change them had arrived and in this post I want to tell how things looked after such a protracted period of operation.

The bearings at each end of the bearing housing looked completely unremarkable; a small amount of the SKF Lesa 2 grease I have been using was evident at both ends, more or less equally distributed between the two ends, and was only a little grey in colour at the pelton end:

My greasing regime has been 4 pumps from a small grease gun once a month (0.8 grams / 1.4 ml per month).

From the encrusting on the length of shaft that sits in the 'top hat water flinger', it was evident that quite a bit of water penetrates into the 'top hat'. The picture below of the wet side of the SOG seal shows a tide mark to half way up it suggesting that water enters more quickly than it can quickly exit from the drain hole: 

Crucially however, there was no evidence whatsoever of water getting past the lip of the SOG seal, and had it done so, the notch cut in the bearing housing to allow it to drain downwards was fully patent and not blocked with grease which had passed through the pelton-end bearing.

The bulkhead showed where water had been striking it and it was pleasing to see this was a mirror image of the splash pattern seen on the front glazing, - indicating that nozzle alignment directing the jet onto the splitter ridges of the cups was pretty good:

The old bearings were taken out and thoroughly examined by dismantling them.  At first there seemed to be little damage to explain the rumble that had indicated the end of their working life, - but on examination with an eye glass there was spalling in the groove of the outer race and this pit was evident at one point in the groove of the inner race:

Spalling* in the groove of the outer race: 

These bearings were SKF units (made in China) as supplied by EcoInnovation. What I have installed in their place are SKF E2 energy efficient bearings which I do not intend to grease at all, - relying on their factory fill of grease to last for their entire working life.

EcoInnovation encourage Powerspout owners to change the bearings every year and this is undoubtedly the right advice: 14,448 hours is 4 months short of 2 years so it is better to stick to an easily remembered 12 month regime.  The exercise described here of pushing the boundary to see how long I could get bearings to last was just an experiment - and it has been an instructive one too.

Here is a clip of what good bearings should sound like, recorded with the new ones in place.

*Spalling is when tiny flakes of material are broken off from the wearing surfaces of a bearing and become deposited in the grooves where the balls run making them no longer smooth.

Tuesday, 13 June 2017

Work productivity - human and hydro.

Lately, the human kind of productivity has been encouraging but the hydro kind less so.  

To take the hydro kind first, - the line of the graph of cumulative kWh's generated for the current year continues to fall away from the trajectories taken in previous years:

...we have had rain, but it has been meagre and not done anything to increase energy output.  I doubt the year total will see 3000 kWh, - which would mean a 25% reduction on last year's total.

This disappointing output is not a result of any interruption in turbine operation, - it has run continuously with no interruption caused by the near miss of the tree falling next to it, - work on the clearing of which is the reason for the encouraging productivity of the human  sort:

The clearing away of the root plate of the tree is still a work in progress.  It's all being done with hand tools so it takes a while.

As I work on it, trying to remove each and every stone amongst the roots that will mean another sharpening of the chain saw's teeth, I keep telling myself "Rome wasn't built in a day", which alternates with "There are worse things to be doing in retirement"!

My thanks to my mate Paul, emptying his boot of saw dust in the picture. Without our arguments about how best to do the job, life would be less fun.

Saturday, 3 June 2017

A different sort of Powerspout

Up 'til now, these diary entries have all been about my Powerspout installation. Last month I visited an elegant scheme that is quite different, - instead of being low flow with several meters of head like mine, this one was high flow with just 2.7m of head.

I'll let the pictures tell the story:

The installation comprises two Powerspout Low Head Pro turbines generating into a single 2 kW Enasolar inverter which is grid connected.  With both turbines running, the power into the grid is just over 1 kW; the operating voltage is 204v dc. Using the Powerspout calculator to 'back' calculate how much water is actually passing through the two turbines, I get it to be 82 l/s.

A lot of water is needed for these low head sites, but as can be seen, at the time of year I visited, at this site there was more than enough, - with much overspilling via the rectangular holes cut into the tank.

With regard to how noisy they were, there was so much sound from water splashing from the over flows that I couldn't hear the turbines themselves at all.

...a nice set up!  My thanks to the owner, - with whose permission these pictures are posted.