G59 Compliance Test

Today the Manweb G59 compliance witness test was completed to the DNO’s satisfaction, so at long last the turbine is signed off. The relay has been set at 264V maximum which should allow some leeway for voltage spike problems. The DNO have also agreed now that we can set a time interval tolerance of 500 ms (ie the voltage spike will have to last longer than 500 ms before triggering a shut-down). Unfortunately however the relay fitted to the turbine does not have the ability to vary the time delay setting, and is set at zero seconds. But we will try this now and see how we get on. In any event we are still waiting for Manweb to reduce the voltage output from the transformer. That adjustment is still due, but all the engineers have been fully engaged with the extreme cold weather that we have been suffering, so it will be after Christmas now before that is done.

Our First FIT Payment

Very exciting! Our first feed-in tariff payment has arrived in the bank. I sent meter readings for 30th November, so Scottish Power have paid for all electricity generated since the commissioning date. Also, because the export meter issue has still not been resolved, we have agreed that they will pay for the “deemed” amount of exported electricity based on 50% of the total generation. This is a better deal than getting paid for actual exported electricity because I can calculate the exported quantity and it is less than the deemed quantity. At 3p per kWh it doesn’t make much difference however, but every little helps!

Anemometer Failure

There has been nothing to write about lately, which has to be a good thing. But this morning, the turbine isn’t running. Logging in to the turbine on the computer reveals the explanation, anemometer failure. My heart sinks, thinking that this is going to be another two weeks without generation while they come out and look, agree that “Oh yes, it’s broken”, then have to wait another week while the part is sent out from Holland. This might be the point in my blog where I reveal, for those who haven’t worked it out for themselves, that the turbine is a WES18 manufactured by Wind Energy Solutions of Holland. So I walk down to the turbine to see that the anemometer is spinning although the display is still reading “Alarm”. I reset the alarm and the turbine starts up.

What has happened is that I have revealed a design feature of the turbine that I was not aware of. As anyone who has been in the UK for the last week or so will know, we are experiencing some cold weather just now. Not exceptional really, though early in the year. Yesterday however the temperature rose to 5 or 6 degrees, and everything began to thaw. The wind had dropped to zero, and there was a great deal of moisture in the air. Then, around midnight, the temperature must have fallen sharply to well below zero, and everything froze up again, including the stationary anemometer. Correctly, the turbine has detected this and shut down. But it has not detected the later rise in temperature and the anemometer unfreezing. Although annoying, this is a deliberate protection measure.

It is conceivable that the frost may have damaged the anemometer bearings such that it would be spinning, but not registering the correct speed. At worst case, the wind speed may increase to a damaging level but the turbine would fail to detect this. In this scenario, considerable damage could be caused to the turbine. Therefore, standard procedure dictates that the turbine should be manually restarted after an anemometer failure, following a visual inspection. One wouldn't have to climb the tower for this, because experience would allow one to assess the wind speed on site and compare it with the anemometer reading.

There is a technical fix available in the form of a heated anemometer, but this would incur more energy use and more expense. Therefore we hope that the weather conditions were rare enough so that the riskof this happening again are minimal.