July 2009 - not been a good month

[langstroth2]

.....yep, we reached 63C in the end. Not bad considering it started at 24C and there wasn't much sun until lunch time.

[Ivan]

Same thing for us. Our cylinder had all the heat sucked out of it last night with kids baths/showers - this morning the top of the cylinder was at an all time low of 37C (anybody's guess as to how much water was at this temperature, as the bottom was a mere 24C or so). Despite showers for most of the day, the sun did shine for a few hours, and the cylinder was heated to 62C. Thus at least 7.6kWh of heat gained during less than favourable weather conditions.

[Flamethrower_]

I must admit this month may not have been so good for solar, but its been good for harvesting rainwater  

Announced on the weather the 3rd wettest July on record (Coalville, Leics. had 170mm rain in July)  

hmmm.........roll on August

[Greenbeast]

- this morning the top of the cylinder was at an all time low of 37C (anybody's guess as to how much water was at this temperature, as the bottom was a mere 24C or so).

i always guestimate that the half way point of the cylinder is around the half way point of the two temperatures
so at half way i'd guess your water was about 33C

is this logical? i suppose it must be close

[KLD]

i always guestimate that the half way point of the cylinder is around the half way point of the two temperatures
so at half way i'd guess your water was about 33C

is this logical? i suppose it must be close

Well, actually no. Suppose you start with a tank full (top to bottom equal temp) of hot, and then draw off some HW. The bottom cools faster then the top, and there is no way you can know from only two sensors what the profile over the entire height is.
I've got three sensors, and the middle one very rarely is near the average temp of top and bottom.

That said, you've got no choice. Short of installing more sensors your averaging is probably as good as any method. Just don't think that the calculated energy values are 100% correct 
----
Forecast for 1 August doesn't look promissing, does it?

Klaus

[Greenbeast]

yeah i guess, if only a small amount has been drawn off then i guess the mid-point would be higher than the average of two readings.
once the drawn off amount starts to approach the mid-point then the temp at that part would start to skew towards the bottom sensor reading.

it's certainly close enough to not bother fitting a third sensor. especially as we live with the system, i get used to the heat change characteristics

[billi]

Was a great Month here for my 1.6 kw PV  (south west Ireland)  ..... total 187 kwh generated in Juli 


so about 6.2 kwh a day

Billi

[dhaslam]

Not so good here.  265KWH up to yesterday, worse than April's total  302.  Today is zero so far.    It was adversely influenced in the first two weeks by my wife being in a nursing home, so half of the hot water usage then.

[langstroth2]

I think I'll post of here more often about rubbish weather - it seems to have an effect as today was glorious

[Hugo]

It's been a good month down in Brighton.  Only switched the boiler on twice since May, and that was only for 15 minutes each time to get cylinder up to 55C.  Yesterday 186 ltr cylinder @ 69C.