50 Tubes (47mm)

[bqjohn]

50 tubes with 1 x 120 Litre Albion Thermal Store (preheating) and 1 x 140 litre Albion Thermal Store (primary) with shunt pump between 2 stores. Resol BsPro controller (set to array2), 100°C Thermostatic blending valve.  Solar primary pipework 22mm with Armaflex 19mm wall thickness insulation. Awaiting additional insulation for thermal stores. Dectite solar flashings used for pipework penetration through slate roof.

[Ivan]

Looks nice! Can you post some temperatures/performance figures?

[bqjohn]

I'm waiting for some Insulation to arrive, to curb the heat losses of these thermal stores, as the 35mm preinsualted foam isn't sufficent.

I'll post some more info. and pcs. when I've got a little further ahead.

[bqjohn]

Eventually I received everything, I then decided to mask off and spray the top of the manifolds black to reduce the shine factor! Then fitting acrylic mirrors beneath the tubes, as opposed to the included Aluminium reflectors. This also means it's easier to remove a tube if required (instead of messing about with those reflectors) and has resulted in further reduced solar gain on the loft bedroom and electrical savings from not having to run a portable air conditioning unit anymore.

The performance has increased marginally, from my own records I am experiencing temperatures in my tanks around 5°C higher on comparable days from before any mirrors were fitted. The additional insulation on the stores also has helped to reduce losses. Peak perfromance (so far) is a 32°C rise on both stores, starting with 2 stores around 54°C in the morning upto 86°C ten hours later.(house unoccupied during day)

Although the cost of Acrylic mirrors doesn't necessarily justify the performance/solar gain reduction, in my case it was more suited due to the weather I experince here  (being close to the sea) and the height of the installation. (No Glass sitting on roof!)

It would certainly be beneficial to use old/reclaimed mirrors if they could safely be installed behind tubes on low level instrallations, especially if they were aquired F.o.C.   

[Paulh_Boats]

bqjohn,

What is the temperature drop per hour overnight of your tanks? Mine is close to 1C per hour because my old tank has only 10mm insulation!

-Paul

[bqjohn]

The drop on the first store fitted in the attic eves is about from 12°C(top temp. probe TSTU) over night from 60° average, depending on how cold it gets etc as it's not insulated in there yet. The second thermal store in series to it fitted in the bathroom cupboard by drops about 10°(top temp. probe TST2) in 15hours (if I get an early sunset at say 6pm usually don't get much from solar until 9am onwards due to SSW roof).

I must admitt I haven't insulated the pipework fully yet. The extra insulation I put over the original foam on both cylinders(which is arkward when they're piped up + fitted) is SF19 superquilt equivalent to 270mm GlassWool, I spent a lot of time cutting it to fit and using foil tape etc. I didn't have room for anything like normal glass wool.

I guess it's not as good as having a tank that's heavily foamed in the factory, but it's an improvement on the original. I'd definately recommend the 75mm foam (triple layer insulation) option when purchasing a Navitron Cylinder/Thermal Store.

I recently observed that an unvented DHW cylinder (Megaflo) of a similar capacity to the 2 tanks I have(combined) stated on the data badge a loss of 3.25KwH/day(I stand to be corrected but it was 3.2something). Based on the fact 260lires equates to a specific heat capacity of around 14Kwh at 65°C, a 10degree drop at same room temperature equates to a new capacity of 11.2Kwh. I've heard other remarks that at 80°C a drop of 10°C on an unvented cylinder installation can be observed overnight. Heat losses (an enemy of a system with an owner dertimed to not switch the boiler on!) are something I would wish to reduce further but I simply don't have the room for storage vessels with 100mm+ thickness foam, so I'll have to live with it.

[lightfoot]

Hi All,

One thing worth noting is that like pipes, you will need proportionally more insulation the smaller the diameter or one big store will lose less energy than two stores of the same total volume and insulation thickness.

260 litres at 65 degC = 19.72 kWh total stored energy

260 litres at 55 degC = 16.68 kWh so thats just over 3 kWh worth of heatloss.

Lightfoot.

PS  It looks like a nice installation bqjohn.

[manwithtool]

Just a note on theinsulation....I too am concerned about temp losses overnight...but again a bit tight on space and only have standard insulation on the tanks.  I have however draped as many towels and other old linen over the tanks and around them, and judging by the warmth of the tank underneath these, it must be stopping a certain amount of heat escaping...not ideal but free and much better than nothing !

[bqjohn]

Just a note, I calculated the specific heat capacity allowing that the ambient temperature was 18°c...........calculating it at 65degrees arriving at 19.7kwh is correct, how ever based on the temperature in the room, I allowed a temperature of 47° as the value between room and tank temp hence arriving at 14.3kwh.

I think I'll be recycling my old linen in that way too.

[lightfoot]

Sorry I have read and re-read your post, but I'm still not sure I follow that thinking. 

I can see how ambient room temperature may effect the rate at which a store cools.  Or determine the amount of energy required to recover the store to a given temperature.  But how dose the ambient room temp effect the overall thermal storage capacity ?

Maybe I'm missing something.....please explain 

Lightfoot.

[bqjohn]

In my case the thermal store pumps into the radiator circuit so I can use ambient temperature as a relation to specific heat capacity. In case of losses, based on Delta-T, ambient 18°c, store 65°c.....shc based on 47°c, I thought this also to be sensible in the case of heat loss conditions as ambinet higher temperatures would of course mean lower losses.

I guess in the case of hot water draw off to outlets, basing you s.h.c on 65°c is correct as obvioulsy incoming water temperatures are the only varying factor.

[lightfoot]

Sorry John you've lost me !

The only thing I can think you may be talking about is useful stored energy ie;  260 litre store at 65 degC and heating return temp say 35 deg C  giving a 30 deg C deltaT,    So (260 x 30 x 4.2) / 3600 = 9.1 kWh of useful stored energy rather than 19.72 kWh total stored energy.

In other words once the store temp is the same as the heating return temp you cannot extract any more useful heat from the store at the design flow temp.

I think I can see what you mean about room temp and in theory heat would still be transfered from rads at lower than normal flow temps until they are the same temp as the room, but I would always work on design return as a minimum temp for sizing stores.

Is that what you're on about ?

But in either case to raise or lower a 260 litre by 10 deg C will require adding or subtracting 3.033 kWh of energy.

lightfoot.

[lightfoot]

I like the idea of the acrylic mirrors as I guess they are less likely to be affected by the wind and I guess thats why you used them, being by the coast.

You said they improved performance and i assume thats compared to the tubes without the standard reflector fitted ?

[bqjohn]

I was merley trying to compare the ambient losses on my budget system using end of line thermal stores with expensive unvented cylinders,  (and make the point that I didn't press the wrong buttons on the calculator) I don't have the equipment or facility to accurately compare this.

Obvioulsy the amount of energy to rasie 260litres by 10°c in practice is greater(as I know too well from what I have here) when raising from 70°C to 80°C, than 50°C to 60°C, due to the losses, which again I am unable to accurately work out.

As I mentioned earlier, the heat loss on the 260lire HE Heatrae Sadia Megaflo was stated in KwH/day on the data badge on the unit, however trying to make a direct comparison to the thermal store here is somewhat difficult without side by side test results.

Barry (John is my middle name)

ps. yes, I didn't fit the standard reflectors at all, just used an IR point&shoot thermometer on the slates inside on a sunny day for comparison. I guess the original reflectors are effective, however the salt air I think would make them deteriorate quickly. If I lived in a single story dwelling, I would have been tempted to use reclaimed glass mirrors. Just like Platinum (up the road from here) has, as mentioned in his post of 50tubes.

[lightfoot]

Sorry Barry,

I just thought I was missing something that I could not see or make sense of.........as the day I stop learning I will hang up my hat for good !

I appreciate what you say about allowing for losses in addition to the base load.

Lightfoot.