Atended the SHA anual ball at the weekend at the Spa, and I got asked the above question. My answer was yes, payback still looks like roughly 8 years. The pannels are providing a great deal of warm water at this time of year (though it has been cloudy lately) but no matter how many pannels you do have the temperature will not get much above 35 oc. Though this does save a lot of energy that would have been used to heat the water from 8oc (ground water temp at the moment) to 28oc (with a heat exchanger due to the specific heat capacity of water, you will normall only get the water to 8oc below the solar temperature).
I am still happy to say 6m3 of water at around 65oc from March to October on every bright day, plus with the pool heat exchanger the lower temperature of 35oc at this time of year is exchanged into the pool as the pool only needs to be around 30oc, very little heat is lost. This has worked so well that we have now taken out the now redundant second boiler to heat the pool water.
Did a talk to the Scarborough “Town Team” last night, I forgot that the town team is concerned with planning, as we have had some discussions over the years with a small minority of people whom want to see the Crown spa Hotel building remain exactly as it was in the “olden days” even if this means it will be a borderline 2 star hotel and run down.
So as I sat down and realised the above I thought “oh crap!” I expected that this was going to be a tough ride, however I was very pleasantly supprised at their reception and the discussions after the meeting. I basically the people at the meeting were not the “minority I have previously encountered. My talk covered the journey from 2005 to the present day and the future plans regarding the enviroment. I explained per the powerpoint what we have done, and took some show and tell items an “Effergy meter” (see below) a simple socket power useage measurer and 50w Halogen bulb, 2W old style LED and 2.5W SMD (a true 50W replacement). Overall it is not until you see the brightness of these lights in real life that you can really see where I am comming from with regard to them.