Solar iboost installation

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  • SterlingtimesSterlingtimes Forumite
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    Martyn1981 wrote: »
    1,200kWh of gas would need about 1,000kWh of leccy (if boiler is 80% efficient ... If losses from boiler efficiency and pipes are closer to 40% (in non heating months), then 1,000kWh of leccy is closer to 1,400kWh of gas.
    I have


    Interesting posting, Mart. There are factors there that I had not previously considered. Very convincing.
    Solar installed 21 November 2014 > Centre of England > 3,780 Wp > 14 *270 Watt Trina panels > 14 * Enphase micro-inverters > managed by Enlighten Envoy Hub > 19° west of south > 35° pitch > tree shading to east > iBoost > Wattson Anywhere monitoring > Schneider Electric (Drayton) MiGenie smart thermostat.
  • SterlingtimesSterlingtimes Forumite
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    nigelpm wrote: »
    I've no doubt you could divert around 1,200 Kw/h in a good year but not useful if you only make use of 75% of it.


    We all have a tendency to justify our own purchases. For me, the iBoost was thrown into a job price. However, I will not be fully convinced until I have the first summer's data. Problem here is that as an eco-dad, I fail in imposing behaviour on the Sterling family.


    Regards, Sterling
    Solar installed 21 November 2014 > Centre of England > 3,780 Wp > 14 *270 Watt Trina panels > 14 * Enphase micro-inverters > managed by Enlighten Envoy Hub > 19° west of south > 35° pitch > tree shading to east > iBoost > Wattson Anywhere monitoring > Schneider Electric (Drayton) MiGenie smart thermostat.
  • nigelpmnigelpm Forumite
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    We all have a tendency to justify our own purchases. For me, the iBoost was thrown into a job price. However, I will not be fully convinced until I have the first summer's data. Problem here is that as an eco-dad, I fail in imposing behaviour on the Sterling family.


    Regards, Sterling

    If it's thrown in no point in considering whether it's economic then :)

    Of course, it's not generally good for the environment though either as much better to send the few kw/h's to your neighbours and reduce carbon emissions and UK electricity demand.
  • 1961Nick1961Nick Forumite
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    From the little bit of research I've done it seems that the best way to make use of one of these units is to combine it with a destratification pump. Lowering the central heating tank stat & maxing the immersion stat will only go so far. A destrat pump could probably double the energy storage of the existing tank & enable a lot of water to be drawn over night before the boiler kicked in. It might even be possible to make it until sunrise the next day without any boiler assistance.

    Investigations continue.
    4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North Lincs
    Installed June 2013 - PVGIS = 3400
    Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus Batteries - 12kWh
  • edited 7 January 2015 at 8:02PM
    zeupaterzeupater Forumite
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    edited 7 January 2015 at 8:02PM
    1961Nick wrote: »
    From the little bit of research I've done it seems that the best way to make use of one of these units is to combine it with a destratification pump. Lowering the central heating tank stat & maxing the immersion stat will only go so far. A destrat pump could probably double the energy storage of the existing tank & enable a lot of water to be drawn over night before the boiler kicked in. It might even be possible to make it until sunrise the next day without any boiler assistance.

    Investigations continue.
    .... probably not if your annual demand for showers alone is 131 tonnes of 60C DHW consuming over 17kWh/day of heat provision energy - without a really large (/massive) heat store you'd never have a buffer for dull days, but with a really large (/massive) heat store and a destrat pump you'd rarely have any hot water anyway .... 17kWh would just about boil a 200l cylinder from cold, and tomorrow you'd need to do it again, come rain-or-shine ....

    To supply that level of shower energy whilst providing a buffer for dull days and supply a decent proportion of DHW from pv you'd probably need a 1000l cylinder and divert from an 8-10kWp array to multiple immersion elements ... but, of course, there's always the possibility that the EST DHW calculator is wrong, assumptions used have been overestimated, or the OP has very old & very inefficient gas boiler - in which case the money for a heat-pump tumble dryer could probably be put to better use ... ;)

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • 1961Nick1961Nick Forumite
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    zeupater wrote: »
    .... probably not if your annual demand for showers alone is 131 tonnes of 60C DHW consuming over 17kWh/day of heat provision energy - without a really large (/massive) heat store you'd never have a buffer for dull days, but with a really large (/massive) heat store and a destrat pump you'd rarely have any hot water anyway .... 17kWh would just about boil a 200l cylinder from cold, and tomorrow you'd need to do it again, come rain-or-shine ....

    To supply that level of shower energy whilst providing a buffer for dull days and supply a decent proportion of DHW from pv you'd probably need a 1000l cylinder and divert from an 8-10kWp array to multiple immersion elements ... but, of course, there's always the possibility that the EST DHW calculator is wrong, assumptions used have been overestimated, or the OP has very old & very inefficient gas boiler - in which case the money for a heat-pump tumble dryer could probably be put to better use ... ;)

    HTH
    Z

    Who said anything about buffering for dull or rainy days?

    We use about 100 tonnes of 60C DHW for showers pa plus about 10 tonnes for everything else.

    During the summer months we average 10kw per day spare which would go a long way towards meeting the DHW needs. The problem is getting as much of that energy into the existing tank as possible while there's a solar surplus. A destrat pump would ensure that happens. Without it the immersion stat maximum setting would soon be reached & the surplus energy would be exported.
    4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North Lincs
    Installed June 2013 - PVGIS = 3400
    Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus Batteries - 12kWh
  • edited 8 January 2015 at 12:41AM
    zeupaterzeupater Forumite
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    edited 8 January 2015 at 12:41AM
    1961Nick wrote: »
    Who said anything about buffering for dull or rainy days?

    We use about 100 tonnes of 60C DHW for showers pa plus about 10 tonnes for everything else.

    During the summer months we average 10kw per day spare which would go a long way towards meeting the DHW needs. The problem is getting as much of that energy into the existing tank as possible while there's a solar surplus. A destrat pump would ensure that happens. Without it the immersion stat maximum setting would soon be reached & the surplus energy would be exported.
    Hi

    Are you sure ? ..... you cannot shower in 60C water without pretty serious side effects. The OP has stated that 6262kWh/year is used to heat DHW just for showers (from on-line calculator) ... that's enough energy to raise the 131 tonnes of water from mains temperature to 60C ... obviously this would need to be thermostatically mixed (assume 2:1), so total shower consumption must be closer to 200tonnes if showering at a hot 45C (Recommendation is low 40s to avoid possibility of burns)

    Without a buffer you're effectively screwed and often have to use a backup energy source even in the summer ... at the OPs level of usage, a large DHW cylinder is being emptied twice a day just by the shower .... not much good if you're only heating it once to the thermostatic set-point when it's sunny and then to emptying it twice before the next day's heating cycle and even less so if its cloudy for the next day or so ....

    If you're using 110cu m of 60C hot water a year, that's 342 litres/day, again around 2 reasonable size DHW cylinders, which would require closer to 10kWh of solar provision each if you had a destrat pump .... alternatively, with a standard cylinder and a 342litre 60C requirement, you'd need to use the backup every day, even in the summer ...

    We have solar thermal with gas backup for the DHW (multi-coil cylinder) and are able to (and do) meter DHW energy input from each energy source .... we use less DHW than the BRE average for our sized household, but not by a great factor.

    BRE assume (from memory) something like a basic 40litres of DHW for the property plus 25litres per head within their 60C DHW provision calculator (It's available on-line at BRE and within SAP calculations if anyone's interested) .... at that (25n+40), a 342litre daily requirement resolves to the average use for 12 people ((342-40)/25) ....

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • 1961Nick1961Nick Forumite
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    Who said anything about showering at 60C? I said we use about 100 tonnes of DHW (not DW) for showering. The mix rate is pretty hard to calculate because the percentage of HW from the cylinder increases the longer the shower is run (I'm making the assumption that the energy cannot be replenished as quickly as a power shower can use it).

    You keep asking whether I'm sure about something. Well I am sure that on a peak summer's day, I have too much surplus energy to heat a domestic HWC in it's current configuration. A destrat pump would solve some if not all of that problem. Another method would be to fit an immersion heater lower down the tank, but as mentioned earlier on this thread, it's not easy because of the profile.

    For clarification....I'm investigating the possibility of using as much of the surplus solar energy as possible. I'm not trying to provide all of my DHW needs from solar as that would be impractical & very costly.
    4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North Lincs
    Installed June 2013 - PVGIS = 3400
    Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus Batteries - 12kWh
  • edited 8 January 2015 at 1:31PM
    zeupaterzeupater Forumite
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    edited 8 January 2015 at 1:31PM
    1961Nick wrote: »
    Who said anything about showering at 60C? I said we use about 100 tonnes of DHW (not DW) for showering. The mix rate is pretty hard to calculate because the percentage of HW from the cylinder increases the longer the shower is run (I'm making the assumption that the energy cannot be replenished as quickly as a power shower can use it).

    You keep asking whether I'm sure about something. Well I am sure that on a peak summer's day, I have too much surplus energy to heat a domestic HWC in it's current configuration. A destrat pump would solve some if not all of that problem. Another method would be to fit an immersion heater lower down the tank, but as mentioned earlier on this thread, it's not easy because of the profile.

    For clarification....I'm investigating the possibility of using as much of the surplus solar energy as possible. I'm not trying to provide all of my DHW needs from solar as that would be impractical & very costly.
    Hi

    I understand that you're investigating, and I also understand your point about 110cu m of 60C DHW .... it's what I'm attempting to convey that's being missed.

    Effectively, this is the Green & Ethical board on a moneysaving site. As it stands what I can see is a couple of members who are looking to reduce energy consumption, presumably for green or moneysaving reasons, but have completely missed the point .... the best way to reduce energy costs/usage is to not use it in the first place. How is using more energy than required green? -and- knowing that you're using far more energy than average and wasting limited energy resources which future generations may need ethical? -and- not taking measures to save money a reasonable strategy for moneysaving ?

    Regarding the mix rate ... in the most simple term available - rubbish, if you have 60C DHW and a 15C mains supply you have a deltaT of 45C ... if you mix 1:1 you'll have a 37.5C flow (60-(45/2)) and at 2H:1C it's 45C(60-(45/3)) .... as for "the percentage of HW from the cylinder increases the longer the shower is run" complicating matters, well that's down to the DHW cylinder - if it's a tall, cold feed at the bottom and DHW take off at the top (as normal) and the water is 60C throughout, the contents will stratify as DHW is drawn, if it's not or doesn't, why would you need to have a circuit to de-stratify? ... when running off water from a stratified column the DHW take-off temperature remains pretty constant until the boundary layer approaches the top of the cylinder, then falls-off rapidly .... of course, if at some time some idiot takes a shower whilst running a destrat circuit your assumption would be correct, but I am assuming that you'll not be doing that ... :D

    If you have a power shower and are looking at reducing energy usage I think you already know what the logical next step is, also, unless you have atypical DHW storage you're very unlikely to be able to make a significant energy consumption difference without addressing the atypical DHW demand. A proportional power energy diversion system on a pv system will only deliver energy when excess is available, so allowing for a household primary pv load averaging (say) 4kWh/day, there's only around 2000-2500kWh/year available to divert ... a typical DHW cylinder would take around ~10kWh to heat from cold to scalding hot, so if there's no (major) daytime draw-off of DHW whilst generation is strong, the maximum useful generation is likely to be 14kWh, even if generating ~25-27kWh on the best days.

    It's all logic & basic physics ... the sensible approach can't be analogous to asking ... "We live in a dutch barn with no walls and having never been able to get it warm have just contracted to replace the D rated GCH boiler with a new really efficient condensing one, so, how much warmer will I be ?" ....

    The reason I keep asking whether people are sure is that there's a general propensity to incorrectly estimate times and quantities .... MrsZ thought that she spent 15-20 minutes in the shower in a morning ... so I timed her for a couple of days - it was nearer to 6 .... that makes a lot of difference. We used to have massive 'tropical rainstorm' showerheads and most of the water ran down the drain without even touching flesh - measuring the real flow rate with a simple plastic bag, a watch and a 1l kitchen jug resulted in a flow restrictor being fitted without really noticing any difference when showing - the shower head has now been replaced altogether ..... what I'm trying to convey is that I've/We've been there, made the mistakes, made the incorrect assumptions, overestimated, used rubbish on-line resources etc ... then we measured what we did, then we improved what we did - and importantly, have not become complacent & still look to improve ....

    The old adage "You can't improve that which you don't measure" is certainly true ... read the water meter, have a shower, read it again <repeat & average> .... turn the GCH off & DHW heating to 'Off' after a normal heating cycle has completed, then use the DHW water as normal until cold (someone will get a shock in the shower!) then read the gas meter, flick the DHW to 'Manual' wait 'till the cylinder thermostat shuts off then read the gas meter again and convert the volume used to kWh .... knowing the gas used and the volume of the DHW cylinder will give the data to calculate the actual system energy conversion efficiency for your own DHW heating .... <repeat & average> ....

    If you supply more information on your current system setup and how it's used maybe someone on these boards would be able to provide some input to assist, but expect a pretty typical reply to include the fact that "The cheapest energy available to you is that which you don't waste" ....

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • 1961Nick1961Nick Forumite
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    I understand what you are saying but (you knew there'd be a but:)) I still think I can increase the total amount of energy stored in the cylinder with a destrat pump. It's a tall tank & there's a significant temperature gradient between the top & bottom. I've not measured it as yet but it's cool enough to touch the bottom but not at the top for very long. I know that's not very scientific but it's a starting point. It would probably only require a tiny pump to de-stratify it.

    My purpose in this instance is not to reduce energy consumption but to look at ways to use green energy rather than gas for as much of the DHW as possible. Solar iboost is clearly a reasonably cheap way of doing this. A destrat pump is a potential add on if there's still a significant amount of surplus pv energy. I do accept your point that it would be 'greener' to export that energy & use less DHW. I confess to not being ethical in that respect but surely still qualify on the other two criteria?:)

    Your mention of the boundary layer is interesting & a thermal map of the cylinder would be a sensible next step.
    4kWp (black/black) - Sofar Inverter - SSE(141°) - 30° pitch - North Lincs
    Installed June 2013 - PVGIS = 3400
    Sofar ME3000SP Inverter & 5 x Pylontech US2000B Plus Batteries - 12kWh
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