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  1. #1
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    Default All in one off-grid heating solution?

    For a scenario where hot water needs are as follows:

    1. On demand hot water from taps
    2. Thermostat controlled in-room heating solution for bedrooms
    3. Pool heater

    Plan is as follows:

    Heat source(s)
    • 17kw heat pump (input power required - 4,2kw) that operates during the day (~5 hours) - heating hot water storage tank in a closed loop system
    • Gas boiler for not so sunny days to keep hot water storage tank at temperature


    Energy sources
    • Solar panel array able to run heat pump during sunlight hours
    • Gas for gas boiler
    • low power circulation pumps from inverter/battery bank


    Hot water storage
    • Insulated hot water storage tank - 2000/3000L.


    Heating requirements
    • Circulating hot water main ring that gets heated via heat exchanger from storage tank and supply hot water taps on demand
    • Thermostat controlled in-room radiators fed from storage tank
    • Pool heating - daytime: solar pipes (black pipes on roof). Night time: heat exchanger thru hot water storage to a point. Solar blanket.


    Few questions:
    • Will a 5 hours daily heat pump cycle store enough hot water in the storage tank to drive my heat requirements until the next day? (maybe not the pool, but at least the hot water taps and two 2m radiators)
    • Can this be done cost effectively?
    • Does sounds completely over-engineered and I can achieve the same outcome much cheaper and simpler?

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    Default Re: All in one off-grid heating solution?

    Perhaps question time... What is the rate of flow to the room heaters or how many bedrooms?
    What is the flow rate through the heat exchanger circulating the pool water through the storage tank.
    Bear in mind at the end of the day the storage tank can be no higher than 60 degrees.

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    Default Re: All in one off-grid heating solution?

    Interesting, will be following progress. Will this be in Pretoria?

    In the last few months I read of a few solutions where a huge volume of hot water was stored, 2000, 3000, even 5000l, initially I thought it was crazy and very inefficient, but if you read up a bit then there is a case for doing it.

    I assume you will want to run the rest of your house off the solar system as well and not only the heat pump. This means you'll need a huge solar system with that size heat pump if you plan to run it 5 hours a day, plus still have some solar in reserve for the rest of the house.

    Have you thought of maybe just doing a proper solar system for the house and then using electric elements for the water? Not too long ago someone posted on here I assumed he is a installer, that they install 2000, 3000l geysers. The geyser then have 3 or more 1 kW elements and depending on the solar generation available threw the day, the system then switches on 1, 2 or 3 elements as needed, so when ever there is spare solar generation after the batteries have been charged, it switches on some or all of the geyser elements. With this you can of course still have a gas geyser as backup for when the brown stuff really hits the fan.
    Last edited by bigboy529; 2021/10/19 at 05:29 PM.
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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by ekkekan View Post
    Perhaps question time... What is the rate of flow to the room heaters or how many bedrooms?
    What is the flow rate through the heat exchanger circulating the pool water through the storage tank.
    Bear in mind at the end of the day the storage tank can be no higher than 60 degrees.

    Why not higher than 60 degrees? From what I read in the past, with these systems where you store lots of hot water, you want to heat it as high as possible with in reason of course, up to 80, 90 degrees. Obviously you must then be sure that your tank, pumps and pipes can handle it.
    "The man who does not read has no advantage over the man who cannot read" - Not Mark Twain

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by ekkekan View Post
    Perhaps question time... What is the rate of flow to the room heaters or how many bedrooms?
    What is the flow rate through the heat exchanger circulating the pool water through the storage tank.
    Bear in mind at the end of the day the storage tank can be no higher than 60 degrees.
    2 room heaters

    flow is still to be determined, but I would expect around 5-10L per minute or thereabouts.

    the hot water for the taps to also be circulated (ring main) with an added pressure pump to increase pressure when a tap is opened for duration of use.

    the 60 degree max - would that be the max temp the heat pump can generate?

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by bigboy529 View Post
    Interesting, will be following progress. Will this be in Pretoria?

    In the last few months I read of a few solutions where a huge volume of hot water was stored, 2000, 3000, even 5000l, initially I thought it was crazy and very inefficient, but if you read up a bit then there is a case for doing it.

    I assume you will want to run the rest of your house off the solar system as well and not only the heat pump. This means you'll need a huge solar system with that size heat pump if you plan to run it 5 hours a day, plus still have some solar in reserve for the rest of the house.

    Have you thought of maybe just doing a proper solar system for the house and then using electric elements for the water? Not too long ago someone posted on here I assumed he is a installer, that they install 2000, 3000l geysers. The geyser then have 3 or more 1 kW elements and depending on the solar generation available threw the day, the system then switches on 1, 2 or 3 elements as needed, so when ever there is spare solar generation after the batteries have been charged, it switches on some or all of the geyser elements. With this you can of course still have a gas geyser as backup for when the brown stuff really hits the fan.

    Yes, solar power will be to drive the whole house. Nothing too big (i guess this is relative), but essentially a 12,5khw system with a bit of stretch. The thinking around the heatpump was to increase the PV array with another 4,5kw to run the heat pump directly from the sun during the day and store the energy in water as oppose to batteries over night. To increase the battery bank to drive the heatpump (or any large appliances like geyser elements) would be a very expensive affair. I guess I could run normal geysers off the sun in the same way the heatpump config above, but I wont be able to store enough heat energy in the geyser to provide heat for the bedrooms and hot water in the taps which is my main challenge.

    yes in pretoria, so luckily I dont have to deal massive temperature drops.

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    Default Re: All in one off-grid heating solution?

    Doesn't Legionnaire's Disease like 60 degree water?
    Jakes Louw
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    Default Re: All in one off-grid heating solution?

    You are smack bang in the middle of an expensive professionally designed system.

    The slightest mistakes and you are either going to be expensively over-engineered or left with a heap of T-Shirts that don't fit.

    ------------------------

    A ring main system is a whole new ballgame, as is the storage requirements you have.

    You mention house, but is sounds more like small hotel or lodge to me.
    Cheers

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by jelo View Post
    Doesn't Legionnaire's Disease like 60 degree water?
    The Legionnaire's couldn't organise Canape in a Cafe', never mind a virus in a vessel.
    Cheers

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by Boesman88 View Post
    Yes, solar power will be to drive the whole house. Nothing too big (i guess this is relative), but essentially a 12,5khw system with a bit of stretch. The thinking around the heatpump was to increase the PV array with another 4,5kw to run the heat pump directly from the sun during the day and store the energy in water as oppose to batteries over night. To increase the battery bank to drive the heatpump (or any large appliances like geyser elements) would be a very expensive affair. I guess I could run normal geysers off the sun in the same way the heatpump config above, but I wont be able to store enough heat energy in the geyser to provide heat for the bedrooms and hot water in the taps which is my main challenge.

    yes in pretoria, so luckily I dont have to deal massive temperature drops.

    I found the thread, https://www.4x4community.co.za/forum...Energy-Storage his example is with a 500l geyser, but you can do it with bigger ones as well, I read of bigger ones else where. Maybe contact him.

    The idea isn't to run the electrical element/s off battery power, the idea is to run it directly off solar during the day, same as you plan to do with the heat pump. So your battery bank doesn't have to be bigger.

    Why bother with all the complexity and cost to heat the bedrooms for 2 - 3 months in a year and same with the swimming pool, Pretoria doesn't even get that cold, won't it be much more cost effective to just focus on hot water for the bathrooms and kitchen?

    You can put the pool on its own system with panels on the roof, that alone along with a solar blanket will already extend your pool usage to at least 9 months of the year, those things get so hot that you have to bypass the panels in summer.
    Last edited by bigboy529; 2021/10/19 at 06:17 PM.
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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by bigboy529 View Post
    Why not higher than 60 degrees? From what I read in the past, with these systems where you store lots of hot water, you want to heat it as high as possible with in reason of course, up to 80, 90 degrees. Obviously you must then be sure that your tank, pumps and pipes can handle it.
    Because that is is the max setting on the heat pump controller. It is also not advisable to go higher than 55 as it used much more power to add the last 5 degrees than from 50 to 55.

    Quote Originally Posted by bigboy529 View Post
    Interesting, will be following progress. Will this be in Pretoria?


    Have you thought of maybe just doing a proper solar system for the house and then using electric elements for the water? Not too long ago someone posted on here I assumed he is a installer, that they install 2000, 3000l geysers. The geyser then have 3 or more 1 kW elements and depending on the solar generation available threw the day, the system then switches on 1, 2 or 3 elements as needed, so when ever there is spare solar generation after the batteries have been charged, it switches on some or all of the geyser elements.
    I just wonder if the maths was done on the power you would need just to keep the 3000L of water at the same temp during the evening with 1,2 or 3 x 1kW elements? This is if the 3000L tank has the same heat loss as a normal geyser.
    Last edited by ekkekan; 2021/10/19 at 06:43 PM.

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by ekkekan View Post
    I just wonder if the maths was done on the power you would need just to keep the 3000L of water at the same temp during the evening with 1,2 or 3 x 1kW elements? This is if the 3000L tank has the same heat loss as a normal geyser.
    I am clearly way out of my depth on this subject, but as far as I know 3KW resistance heater element(s) is just enough for 150-200L geysers… not sure it would heat up the entire 3000L tank. Hence the choice of 17kw heat pump. This gives you the theoretical heat generation ability of 17 of those 1kw units.

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by bigboy529 View Post

    Why bother with all the complexity and cost to heat the bedrooms for 2 - 3 months in a year and same with the swimming pool, Pretoria doesn't even get that cold, won't it be much more cost effective to just focus on hot water for the bathrooms and kitchen?

    You can put the pool on its own system with panels on the roof, that alone along with a solar blanket will already extend your pool usage to at least 9 months of the year, those things get so hot that you have to bypass the panels in summer.
    yes I hear you, and it does sound practical and much cheaper indeed! i am also very aware of the prospect of various sized t-shirts lurking on the horison….

    general use hot water can easily be sorted with a gas on-demand geyser(s) or some hybrid system. Pool also can be sorted with rooftop coils.

    Problem is the house has a lot of glass windows/walls. A LOT. So the heatloss is rediculous. While I dont mind this too much, my family disagrees. So heating solution has to be found and with solar electricity, there arent a heck of a lot of options…

    hence I’m looking into an integrated solution. But, if it ends up to not be feasible or affordable, I’ll re-think.

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by Boesman88 View Post
    yes I hear you, and it does sound practical and much cheaper indeed! i am also very aware of the prospect of various sized t-shirts lurking on the horison….

    general use hot water can easily be sorted with a gas on-demand geyser(s) or some hybrid system. Pool also can be sorted with rooftop coils.

    Problem is the house has a lot of glass windows/walls. A LOT. So the heatloss is rediculous. While I dont mind this too much, my family disagrees. So heating solution has to be found and with solar electricity, there arent a heck of a lot of options…

    hence I’m looking into an integrated solution. But, if it ends up to not be feasible or affordable, I’ll re-think.
    I do support the using of heat pumps to heat water but not using a 1000+L of hot water storage. For the winter I would use inverter aircons and heat the rooms during the day by using PV via grid tied inverters. PV is cheap for the power you can yield even in our winter sunshine. This is for the few months needed.

    It seems like some of us have excess PV and now looking how can we use it but end putting it to use to have 10 times more hot water than is the actual need but a nice to have.

    Without a feeling for the cost of the 3000L tank option one cannot really even start comparing.

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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by Boesman88 View Post
    yes I hear you, and it does sound practical and much cheaper indeed! i am also very aware of the prospect of various sized t-shirts lurking on the horison….

    general use hot water can easily be sorted with a gas on-demand geyser(s) or some hybrid system. Pool also can be sorted with rooftop coils.

    Problem is the house has a lot of glass windows/walls. A LOT. So the heatloss is rediculous. While I dont mind this too much, my family disagrees. So heating solution has to be found and with solar electricity, there arent a heck of a lot of options…

    hence I’m looking into an integrated solution. But, if it ends up to not be feasible or affordable, I’ll re-think.

    Personally I wouldn't go close to the route in your OP, it will simply be too complex and eventually too expensive.

    I'm not even entirely convinced on the big volumes of hot water storage yet, so I'll do it much more traditionally if it was me.

    Geysers, depending on the amount of bathrooms in the house, 2 or 3 normal size 150l and they must be vertical. It's still a toss up for me between going normal electric with 2 kW elements or EV tubes with 2 kW backup elements, this will depend on the cost of the EV vs normal geysers.

    Solar system, depending on the size of the house and your usage, start out with a 5 kW inverter, 6 kW PV and 10 kW batteries grid tied, with the option right from the start to add on to it in future if the need is there.

    Swimming pool, its own stand alone closed loop panel system as already mentioned, plus a solar blanket.

    Heating bedrooms in winter, don't know, something which can run off the batteries at night, maybe wall panel heaters plus electric blankets, they are quite low power. Personally I haven't used any form of heater in the house in years.

    With a control system your geysers can then run directly off solar during the day, obviously not all at the same time, but if the need is really there early morning or evening, you just run the geyser on Escom, or of batteries if you expand your solar system at a later stage.

    Oh and maybe also explore double glazed windows especially for the bedrooms, this in itself is very expensive, but in the bigger picture, passive insulation might work out cheaper than active heating, same goes for ceiling insulation.
    Last edited by bigboy529; 2021/10/19 at 07:37 PM.
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    Default Re: All in one off-grid heating solution?

    Quote Originally Posted by bigboy529 View Post
    Personally I wouldn't go close to the route in your OP, it will simply be too complex and eventually too expensive.

    I'm not even entirely convinced on the big volumes of hot water storage yet, so I'll do it much more traditionally if it was me.

    Geysers, depending on the amount of bathrooms in the house, 2 or 3 normal size 150l and they must be vertical. It's still a toss up for me between going normal electric with 2 kW elements or EV tubes with 2 kW backup elements, this will depend on the cost of the EV vs normal geysers.

    Solar system, depending on the size of the house and your usage, start out with a 5 kW inverter, 6 kW PV and 10 kW batteries grid tied, with the option right from the start to add on to it in future if the need is there.

    Swimming pool, its own stand alone closed loop panel system as already mentioned, plus a solar blanket.

    Heating bedrooms in winter, don't know, something which can run off the batteries at night, maybe wall panel heaters plus electric blankets, they are quite low power. Personally I haven't used any form of heater in the house in years.

    With a control system your geysers can then run directly off solar during the day, obviously not all at the same time, but if the need is really there early morning or evening, you just run the geyser on Escom, or of batteries if you expand your solar system at a later stage.

    Oh and maybe also explore double glazed windows especially for the bedrooms, this in itself is very expensive, but in the bigger picture, passive insulation might work out cheaper than active heating, same goes for ceiling insulation.
    You make strong arguments for a more conservative approach. And I agree with most of what you say, especially the benefit of having good insulation to avoid the drastic heat loss!! Insulation, or the lack of insulation is unfortunately the key concern I am trying to work around. Double glazing would have been the no.1 choice for me, but not viable due to the unconventional construction of my home.

    So I am primary solving for heating up the home, then I'll solve for pool and hot water which in my case are the two easier challenges to solve. My heat loss calculation shows a 138000 BTU/hr loss considering infiltration and conductive losses for my house which is a big problem for a few months of the year. I'm not even going to try and get the whole house warm - instead focus on heating the bedrooms which currently runs at 27 000 BTU/hr loss each in colder months.

    I do hear you around keeping it simple, but I first want explore the possibilities of a basic central heating system.

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    Default Re: All in one off-grid heating solution?

    Hi Gents,

    This is something I have been looking at for awhile now, not exactly what the OP is looking for as I am looking at underlfoor heating, but nevertheless some ideas:

    1. Samsung has a system were you use a heat pump to run the domestic water supply, heating and the air-conditioning as well.
    2. You get a built in fireplace, were the chimney goes through a soapstone wall. The idea is that the heat from the fireplace heats up the soapstone and then radiates the heat back into the house over an extended period of time. You could combine this with a water heater in the chimney as well.
    3. There are some developers in Germany that are proposing a "Passive House". Basically 300mm of insulation plus air tight. Due to it being airtight you have to install mechanical air circulation to maintain air freshness. The trick there is that the outgoing hot, stale air goes through a heat exchanger with the fresh cold air - warming it up before it gets into the house.

    I attach brochures from Samsung, Tulikivi and Passive House.
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