More paper work !

At the end of each month I need to remember to keep my records up-to-date.  

This November has been a bonanza month for generation, especially considering it was only from Nov 5th that there was sufficient flow to generate anything at all.  By the end of the month, 393.7 kWh will have been clocked up, and the capacity factor for the month will be a very presentable 0.73.

I need to remember because a return stating the volume of water I've abstracted has to be sent to Natural Resources Wales (NRW).  NRW like the year to be broken down into individual months, and you have to give the volume abstracted in each month. The return has to be sent in within 28 days after 31st March but fortunately they post the form to you as a reminder.

For my scheme, to generate each kWh requires 13 m³ of water;  this is a figure the NRW call the Hydro Abstraction Factor and they tell you how to calculate it for your scheme.  The inputs to the calculation, which will vary from site to site, are the 'water-to-wire' efficiency and the head of the scheme.

Here is the spreadsheet I keep of monthly abstraction so everything is to hand at the end of March to complete the annual return:

So that was one bit of paperwork I had to remember to do.  The other was applying for payment for the kWh's generated in the past 3 months.  Since the turbine doesn't operate for most of that quarter, for lack of water, a November claim is the lowest of the year: just £71 on this occasion.

Claiming feed-in-tariff is a much more straightforward business. I opted for a contract with Scottish and Southern Electricity (SSE) simply because they're the company we purchase power from and it seemed to make sense to stick with them.  Submitting a generation-meter reading on-line is simplicity itself at the SSE webpage. You immediately get email confirmation of your claim being processed and payment comes through direct to your bank account, - somewhat unusually on this occasion, within 48 hrs.

Co-incidently, I had a letter from SSE today telling me they're in the process of updating their FIT payment system.  When completed, I'll be assigned a new date in each quarter on which to submit my FIT claim and more detail will be provided about how it is calculated.  Additionally, their man who comes to read the meter will, in future, read both consumption and generation meters at the same visit.

So the take-home message is: in the UK at least, there is a fair amount of bureaucracy involved in operating even a small hydro installation, but like a tax return, so long as you keep on top of all the figures and the deadlines, it isn't burdensome. 

TIC, DNC, Abstraction and all that stuff.

For the first time, I now have the Powerspout operating at 'design flow', - at least it's the first time I've had any certainty the flow being delivered is the design flow: 3 lps. So for the first time too, I have reliable figures for those two parameters so loved by OFGEM: Total Installed Capacity (TIC) and Declared Net Capacity (DNC). OFGEM is the UK body giving accreditation for an installation to receive payment for the electricity it generates.

Just to set the record straight: DNC is TIC "less any electricity consumed by the generator".  So for a Powerspout the power taken by the inverter (see last post) has to be deducted from TIC to get DNC. Both of these figures need to be specified at the "highest capacity at which the generating station could be operated for a sustained period ... without causing damage to the generating station". I took that to mean at 'design flow'.

I may have taken it to be at design flow but in fact a Smart Drive alternator can put out in excess of 1kW for a sustained period and without being damaged, so there is nothing actually to stop me from delivering a flow in excess of 3 lps, when it's available, and getting more power.  That would've meant giving OFGEM a higher TIC and higher DNC.  So where do you draw a line in the sand ?

I opted to give values for TIC and DNC based on 3 lps because my abstraction licence limits me to that flow.  Which begs the question "why didn't you ask for a higher abstraction volume?" And the answer to that is another line in the sand: it seemed from the flow duration plot for my site to be the optimum peak flow when the pattern of flow over a full year is taken into consideration.

I relate all this to make the point that filling in all the forms to make an installation 'legal' is a headache.  Moreover what you put on one form, the Abstraction application, has a bearing on what you put on your OFGEM form to get accredited for Feed in Tariff payments.

To get back to real figures, below is the actual return I submitted to OFGEM last year for my FIT accreditation...

... and as you can see, I put 0.8 for TIC and 0.75 for DNC. These were, at the time, the best estimates I could come up with.  They were supported, as the extract above requires, by independent confirmation from Michael Lawley, the manufacturer of Powerspouts, who used the calculator tool on the Powerspout website to confirm my expected output.

But the thing is: it's very difficult to get the accuracy of the inputs to that calculator tool to be spot on; now I have real data available, I find the true TIC and DNC aren't what I submitted.  The DNC turns out to be 0.92kW and the TIC 1.1 kW.*

Do these small differences matter ?: no ! - no one at OFGEM is going to be any the wiser that my submission figures were 5% out.  But the saga does draw attention to the fact that in completing these forms, what you enter on one, the abstraction application, has a bearing on what you should enter on the other: the FIT application. And deciding where 'the lines in the sand are to be drawn', I found to be a hard call.

Finally, if you're wondering what OFGEM's definition of DNC is in full, as hyperlinked in the above extract, this is it:

Confused ? - so was I, - and to a large extent, I still am.  The forms are, truly, a headache.

* figures amended April 2020 with knowledge gained over the 6 years since original post was written.
 

It's just Hinkley B and me now !

What an exceptional week: from scarcely enough flow to more than enough to meet peak generation.  So with all the energy I'm exporting, it's now just me and the nuclear boys keeping the grid from collapsing !

Going through four step-ups in generation in so short a time has minded me to take the four photos below of the meters monitoring the dc output of the SmartDrive, to emphasise two points made in an earlier post:

1.  the pv inverter (PVI) is not very efficient, especially at lower power levels but gets better as power increases
2. the dc system voltage falls as power output increases, and eventually it comes down to within the range  (100 ~ 320v dc) at which the MPPT function of the inverter can operate.

Just nice to see it so clearly illustrated.

Going with the flow

Today has been a good day: the increasing flow available, now up to about 1.75 lps, has meant I've needed to put a bigger nozzle in.  I kept the same one on the bottom and only changed the top one from ∅ 3.64 mm to ∅ 4.96 mm.  An early rule I learnt was only to change one nozzle at a time, - more drastic action usually led to the header tank emptying.

Doing this lifted flow delivered to the pelton from 1.48 to 1.74 lps, and power into the grid from 343 to 421 W.

Small hands are essential and good access to the front of the turbine is helpful.

Off with the glazing

The nozzle to be put in

Nozzle retainer spanner

It's a tight fit getting to the top nozzle

Note the cloth to stop anything dropping into the tailrace

There is space only in the bottom corners to remove a nozzle

The "whole arm in" technique to screw on the nozzle retainer

I use 9 different nozzles to give me flows from 1.18 to 3.43 lps

...and best of all: 421 W generated, thus exceeding usage by 8W

Happiness is...

... the start of a new generating year !  11 am yesterday saw all systems go, and so far everything is performing exactly as it should, right down to the in-house monitoring and on-line visibility of live-power (see link to right).

Now, all that remains is to get the capacity factor for the 2014 / 15 "water year" above the 59% recorded for last year.