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Author Topic: alternate hot water  (Read 2451 times)
Moxi
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« on: March 22, 2019, 03:11:36 PM »

Hi

Apologies for the title but I wasn't sure how better to describe what I am thinking of attempting:

We live in a cottage on the west coast of North Wales at the 300m contour with clear views out over Caernarfon Bay (we see the Wicklow range in Ireland on the horizon on clear days)

The cottage has external wall insulation and is generally warm and cosy heated by an 8kw wood stove with a 5kw wood stove in the other room so we can run one or the other or both as required and as a backup we have an LPG condensing boiler which provides direct hot water and central heating - there is no hot water tank and no space to fit one other than outside the house.

I would love to be able to offset some LPG water heating and earl and late season log heating with electric (we have 3.8kWp of solar panels WSW) and I am seriously contemplating a LE300 wind turbine given our aspect (nothing bigger as we have limited ground adjacent to the house (garden is across the road  Cry)

I have an idea of dropping some surplus power in to the radiators via towel radiator heating elements but to circulate would I need a separate pump and if so would this interfere with the Worscester Bosch 28kW condensing boiler?
I have also wondered in an under sink inline electric water heater would work but again I don't know how this would work with the boiler and also its limited by daylight hours so not necessarily well aligned with night time heating demands.
I have considered and ASHP but we have very moist air being close to the see so not sure if this is an option.

Does the forum have any suggestions or ideas?

Moxi
 
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bxman
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« Reply #1 on: March 22, 2019, 04:08:38 PM »

do you have a diversion device ?
if so
there are insulated  under sink electric water heaters in the range of  5 -20 litre capacity  with 1 or  2 kw heating elements  that might fit the bill.

good luck
Patrick
 
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RIT
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« Reply #2 on: March 22, 2019, 05:46:40 PM »

You may find it is better to keep it as simple as possible and not touch your current heating system.

If you take a PV diversion product like a Solar iBoost+ or immerSUN (depending on the exact state of the supplier) you can connect up any purely resistive heater (no pump/fan or electronic control features). An added advantage is that the likely cost of the heater is going to be very low. A no feature 2kw convector heater can be sourced for less than £20 off the internet.

Such a solution would not touch your current central heating and so keeping things separate. One reason for doing this is is that trying to raise the temperature of the water within your central heating with spare PV energy will be a slow process - consider the volume of water to be heated and the fact that at times you may only be diverting 100's of Watts of PV output.
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brackwell
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« Reply #3 on: March 22, 2019, 05:50:21 PM »

Patricks suggestion is a good one.

The basic problem we are all faced with is the fact that PV produces the least when we most need it.  Leccy is a very valuable source of energy and should not really be used as heat energy as this is the lowest form of energy (all types of energy end up as heat) and so you have to use it as leccy or lever it up to make something more usefull.  
The most obvious thing is to us it to power the house and to maximise this it may be nesassary to fit a storage battery which can also capture E7 rate leccy.
Other ways to capture the most value is to charge a EV or a HP
I guess you know the advantage of a HP. the only real problem comes when operating near the dew point of the air when if say 0to3C the additional cooling causes ice to form and reduces the efficiency. It does not stop it working even then but for 9 months of the yr it will work OK.

Wind power is a bit up and down and therefore requires significant storage but then maybe the batt could do this but i do not think this will be viable but others on here have experience.

Remember that for say 100 days of the yr there is not any spare PV leccy after powering the house.

Ken
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biff
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« Reply #4 on: March 23, 2019, 10:59:53 AM »

Moxi,
      My apologies. I should have posted my solution to your heating problem, If you have a peep at my last post on the thread, ( A FOUL WIND A BLOWING) you will see read a possible solution to your heating
 query in my address to Tod. It does of course of course involve batts and a thermal store + a Pump on the opposite Push/Pull of the existing C/H pump. It has been working here exceedingly well for a past few years..
  It,s worth considering if you wanted a little protection against outage as well.
                 Biff
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knighty
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« Reply #5 on: March 23, 2019, 01:43:29 PM »

for heating you could add an inline heater to your current system - pretty much just an immersion heater in a bit of big pipe, with a little pipe at each end (one for in one for out)

power it via diversion load to put solar power into it


is there a decent spot out outside up against the house you could add a tank with lots of insulation?
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andrewellis
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« Reply #6 on: March 23, 2019, 08:57:15 PM »

I have an idea of dropping some surplus power in to the radiators via towel radiator heating elements but to circulate would I need a separate pump and if so would this interfere with the Worscester Bosch 28kW condensing boiler?

I tried the towel radiator thing this year.  I am in the process of wiring in a wireless switch to turn it on/off depending on the spare exported power.  It makes the towels nice and warm but I found that even when it is boiling hot the water coming in whips across the bottom rail and out.  The temperature gradient is too hot so you don't get the hot water coming out of the return like you might think would happen.  You would need something inline with the main water loop to put heat into if you wanted to do all your radiators. 
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Moxi
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« Reply #7 on: March 25, 2019, 02:09:15 PM »

Thank you all for your thoughts and opinions,

I must apologise as I had not mentioned that I do indeed have a diverter which powers an oil filled radiator in the day when there is sufficient solar available, that aside your combined comments have, I think, helped me to zero in closer to the issues that I am grappling with:

1) Energy storage - to use the energy at the time its required not at the time its available:
    a) Store as heat ?
    b) Store as electric ?

If I store as heat then I face difficulty integrating it with the existing house plumbing circuit and storing sufficient quantities of heat in a heat store and as a few of you note its a poor use of electric power.  Andrew, thank you for the information about the towel rail heater issue that was a new learning point for me.

If I store the energy in its electric form then storage appears to be more straight forward (no additional plumbing, no outside heat store, no interface with existing boiler and pump) the flip side of this is that we are pretty frugal on electric and early to bed to boot so even in the depths of winter we only consume around 1.524kWh during dark hours (includes usual scavenger loads like F/F router etc) so is battery storage for that amount worth it - reading through the forum suggest not.  It also forgoes the basic fact that we need heat during the darker hours far more than we need electric.

Biff, I have read and re-read your threads for direct heating many times and I think this is the system that I ultimately need to emulate - the draw back being the kit required to achieve it seems significant but now I see that maybe I have been trying to get to the end point solution too fast / in one step and the real solution is to apply what you and Ken and others have advocated before using self produced electric to off set imported electric and start small and scale up as and when funds/ confidence permit.

I will go back through the threads to refresh myself about battery charging and 12, 24, 48V systems etc and get saving

Thank you again for your comments its helped.

Andy

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offthegridandy
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« Reply #8 on: March 25, 2019, 02:28:52 PM »

Hows about a single night storage heater as your energy store.  Keep the vent flaps closed during the day and slow release heat at night.? No plumbing and simple wiring no  integration issues.  Less  use in summer when house may not need heat.

Andy
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andrewellis
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« Reply #9 on: March 25, 2019, 02:31:50 PM »

Hows about a single night storage heater as your energy store.  Keep the vent flaps closed during the day and slow release heat at night.? No plumbing and simple wiring no  integration issues.  Less  use in summer when house may not need heat.

Andy
This would only be of use in the shoulder months and then it comes down to your motivation. Would it be cost effective?
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Stig
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« Reply #10 on: March 25, 2019, 03:14:43 PM »

Hows about a single night storage heater as your energy store.  Keep the vent flaps closed during the day and slow release heat at night.? No plumbing and simple wiring no  integration issues.  Less  use in summer when house may not need heat.

Andy
This would only be of use in the shoulder months and then it comes down to your motivation. Would it be cost effective?

If you can find a suitable storage heater on ebay that's nearby (not the sort of thing you can post) it can be very cheap - I got one for 99p as no one else bid!  When it's been a sunny day in the last few weeks my central heating hasn't been needed in the evenings.
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andrewellis
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« Reply #11 on: March 25, 2019, 03:27:37 PM »

Ah I hadnít thought of that. Are they a pure resistive load? Ie can one run them of an immersun?
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Stig
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« Reply #12 on: March 25, 2019, 03:51:51 PM »

Ah I hadnít thought of that. Are they a pure resistive load? Ie can one run them of an immersun?

Yep, that's what I'm doing (well, a home-build version of solar diverter).
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nowty
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« Reply #13 on: March 25, 2019, 07:59:08 PM »

Me too if you buy the most basic one without any timers.
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biff
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« Reply #14 on: March 25, 2019, 08:19:58 PM »

  When I built our thermal store,     
                              I built it in the hall downstairs. I insulated it to the hilt, It came with 50mm insulation stuck to it but I boxed it in and surrounded it with celotex 50mm 100mm on top and 100mm on the bottom. I left access panels for the pump and the expansion tank. Then on the outside paneling in the hall I fitted a row of coat hangers. despite the insulation, there must be a gap at the top because when I put my hand between the coats and the paneling I can feel the heat most days. Near the top,,2100mm up there is a adjustable vent like the one near the bottom, In winter I can open and close these but I just leave them shut.This set up keeps the hall chill free.
     One of the things about storing heat in water is that it is fluid and can be pumped anywhere in the house at a few seconds notice. It is important to remember that. Static heavyweight heaters can not be easily moved. Even with a sack trolley , Grin been there done that, dinged the toes,
  Still, storage heaters are a good choice at least you are saving the heat and letting it go as you need it.
                                   Biff
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