Renewables: "talking 'bout my generation"

Kernel_Sanders wrote: »

Same curtailment of peak output as per yesterday, but another ½kWh added to yesterday's record nontheless; now 21.88 kWh. Had immersion on again, but thermostat cut in when bottom of cylinder barely warm. Why is this when it is turned to its maximum of 180°F?

As usual I'm just a bit behind you (20.77) - almost certainly due to shallower pitch as I didn't see a cloud all day apart from a few contrails.

Immersion heater is probably in top half of tank ? They're designed that way to give a quick boost to DHW so you can do a bowlful of washing up or have a (short) shower asap. Very little circulation in a DHW cylinder so water at stop gets hot and bottom stays cold. Doesn't matter quite so much with the coil you probably have heated by a gas boiler or whatever as (a) that's usually set a bit lower and (b) it's controlled by a tank thermostat which is also set lower in tank.

You could try fitting another (pref low power) element at bottom of tank but doubtful whether cost would be justified.

Kernel_Sanders wrote: »

Yes, same here. I still think you will catch up (and, indeed, overtake me) before we reach the solstice..

The optimum pitch for SS day would be approx 30deg (latitude - 23deg). Your 23deg is closer to that than my 17.5 - but we'll both be better off that day than anyone with a slope of 45deg.

Kernel_Sanders wrote: »

Aren't all single element immersion elements at the top of the cylinder? I just want to get all the water as hot as possible so it will cover the next couple of cloudy days that we have. Is it possible to disable the thermostat? I remember about 25 years ago the water boiling in my cylinder with steam coming from the header tank! Can't remember if this was due to the element or the thermostat for the gas coil that you mentioned.

The cylinder's quite old (possibly 35 years), so may invest in a stainless steel one. I'd want a small (500W?) element at the top so I can still have free hot water and that short shower in the winter.

Nothing easier than disabling a thermostat - just bridge it with a bit of wire. HOWEVER, nothing more dangerous than an exploding DHW cylinder ! I wouldn't risk it. You can certainly buy replacement thermostats and with a bit of hunting around you should find one with a higher setpoint than normal. My 'Heatbank' has two adjustable thermostats in series - one goes to 80, the other 90 deg C; may sound silly but I guess the idea is that if you choose to short out the 80 and rely on the 90 the manufacturer hasn't recommended that.

If you're buying a new cylinder, I'd suggest you specify one with two (or even more) immersion heater mounting points. One high wattage one in normal place to give almost instant emergency DHW and a couple of smaller ones at bottom so that you can wire up one (or both - depending on surplus level) to 'waste' spare electricity. Additional cost over a standard cylinder would be modest but whole cost of an unnecessary replacement probably not justified (although copper scrap value might help pay for a SS tank ?) .

I'll try & look up a contact for purpose built cylinders from the UK_selfbuild forum.

http://www.newarkcoppercylinder.co.uk
They are pretty handy for Mansfield but only seem to do copper ones.

I've PM'd you with some more

We exceeded 125% of our PVGIS estimate by 11am Weds, just before we set off for a few days away. Fortunately my Solo PV is logging away while we soak up the sun's rays elsewhere. If we've made another 55kWh then that'll be 1000kWh clocked up in total. Happy (sunny) Days!

What a difference a (cloudy) day makes. Only 2.5kWh today. So that's March over, it would be great to have an April like last year's (before I had the panels) but with some overnight rain to ease the drought