A lesson learned

Even after 10 years, I am still learning about my Powerspout; today the lesson has been how minutely critical the alignment of the jet to the pelton wheel needs to be for maximum power to be generated.

My lesson came about like this: the turbine had been running very sweetly on 1.23 l/s, generating 331 watts into the grid, at a water to wire efficiency of 51.2%, - when I took it upon myself to disturb this happy state of affairs by putting in a wire-mesh grill; the grill was to sit beneath the turbine and stop me dropping parts beyond reach of retrieval when I do a nozzle change.

To slip the grill into place required the plinth on which my turbine sits to be lifted a very small distance, - but to lift the plinth requires the pipe manifold to be separated from the Powerspout casing, and to do that, the jet-cum-nozzle assemblies have to be removed.

No problem I thought !

After re-assembly, I was perplexed to find that the previous output of 331 W was now only 250 W, and the overall efficiency had dropped to 41.2%.

Nor did the turbine look or sound right; the splash pattern was not what it had been and there was the sound of some water missing the pelton and hitting the opposite wall of the Powerspout casing.

What followed was much experimentation with packing washers behind the runner, measurements using my knitting needle alignment tool (see this blog) and checking and rechecking what else could have been inadvertently put out of alignment.

Eventually, it was a hammer and a piece of wood that solved the issue, - by judicious tapping of the jet-cum-nozzle assembly whilst the turbine was running.

The tapping restored the original happy state of affairs by moving the assembly tiny amounts within the bounds of the hole in the casing through which the assembly passes, with these barely perceptible movements being judged good or bad only from observation of the splash pattern and from the sound the turbine was making.

Creating a Powerspout installation is a labour of love; having created it, everyone wants 'their baby' to generate as much as their site conditions allow; as this lesson teaches, it's worth checking that your jet alignment really is optimal.

Here are some pics to put flesh on the day's adventure:

Wire mesh grill in place beneath where pelton runner normally is attached to the shaft.

Using knitting needle tool to optimise alignment of runner to centre of jet.

 "if all else fails, 'it it wi' 'ammer" !