Solar Geyser





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Thread: Solar Geyser

  1. #1
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    Default Solar Geyser

    For those in the know.

    I'm looking at converting my current geyser to solar.
    The options are flat plate or pv solar panels.
    What is the best option? I'm confused.

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    Default Re: Solar Geyser

    Don't convert your ex geyser,
    Leave it connected as a extra storage tank.
    Get your new solar installed and feed the hot water from the solar geyser into your old geyser, your ambient water temp inlet to your old geyser could even be hotter than your element heated water.
    All your old geyser will do is maintain heat...and give you extra storage water your can use at any time.
    If you want to go the PV method you would obviously have PV panels and a different element...
    Ask Fluffy or one of the other eletrickery guys to explain what is needed...

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    Default Re: Solar Geyser

    This is worth considering ............
    If you make a noise or need music in the bush or on the beach, youíre missing the point.

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    Default Re: Solar Geyser

    Quote Originally Posted by DeVilliers View Post
    For those in the know.

    I'm looking at converting my current geyser to solar.
    The options are flat plate or pv solar panels.
    What is the best option? I'm confused.
    I would choose a grid tied inverter with 4 x 280+W panels. This would be enough to heat up a 150L geyser on the days we have 80% sunshine. Once the geyser is on temp the power form the panels can drive other standing loads like fridges and other loads during the day. This one would perhaps not want to use if you are on prepaid meters that might switch off.

    Another solution could be to drive the excisting 220V element with the 130V @ 7.5-8A provided by the 4 panels in series. This will provide up to 3.6kWh per day with sunshine. The current thermostat would cut the PV when the geyser is at desired temp. One just needs to wire in a changeover switch to switch the current element between grid and PV. Also one would use a timer to select the grid after 17h00 to heat up the water during the evening or when it is raining or overcast. The timer can cut the 220V say at 03h00 in the morning to heat up the hot water used in the morning once the PV starts heating up the water. It just means one will have to get used to the fact of changing over from grid to PV each morning. The changeover switch MUST be rated for DC to blow the DC arc.

    This method might not be common and could provide some debate around it's functionality.

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    Default Re: Solar Geyser

    Quote Originally Posted by ekkekan View Post
    I would choose a grid tied inverter with 4 x 280+W panels. This would be enough to heat up a 150L geyser on the days we have 80% sunshine. Once the geyser is on temp the power form the panels can drive other standing loads like fridges and other loads during the day. This one would perhaps not want to use if you are on prepaid meters that might switch off.

    Another solution could be to drive the excisting 220V element with the 130V @ 7.5-8A provided by the 4 panels in series. This will provide up to 3.6kWh per day with sunshine. The current thermostat would cut the PV when the geyser is at desired temp. One just needs to wire in a changeover switch to switch the current element between grid and PV. Also one would use a timer to select the grid after 17h00 to heat up the water during the evening or when it is raining or overcast. The timer can cut the 220V say at 03h00 in the morning to heat up the hot water used in the morning once the PV starts heating up the water. It just means one will have to get used to the fact of changing over from grid to PV each morning. The changeover switch MUST be rated for DC to blow the DC arc.

    This method might not be common and could provide some debate around it's functionality.
    I think a grid-tied inverter is a bit of an overkill for the application - depending on the OPs future plans.

    Would direct DC PV panel input on the DC element work, will it be efficient?

    Look geyserwise, or the link PRA placed for a combined unit.

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    Default Re: Solar Geyser

    Quote Originally Posted by SAND View Post
    Would direct DC PV panel input on the DC element work, will it be efficient?
    My question is why do we want to use a so-called DC element?
    Any element wheather connected to DC or AC should yield the same power=heat as it is only resistive.

    I fail to see why a 1kW grid tied inverter at R4 750 plus whatever the panels cost is an overkill. A 1kW grid tied can generate up to 5kW per day in good sunshine. The panels can also be used if there is any future plan for using PV which I think as the loadshedding continues for at least the next 6 years could be part of any power plan going forward.

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    Default Re: Solar Geyser

    I got a flat panel system it is connected directly to the geyser. The hot water pumps into the geyser. The vacuum tubes work much better but we have baboons that will break them. If you can fit the tubes or panel below your geyser you dont need a pump. I don't know how effecient a inverter with solar panels is compared to a direct heating system? I dont see it often presume there is a reason for it.

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    Default Re: Solar Geyser

    Quote Originally Posted by ekkekan View Post
    My question is why do we want to use a so-called DC element?
    Any element wheather connected to DC or AC should yield the same power=heat as it is only resistive.

    I fail to see why a 1kW grid tied inverter at R4 750 plus whatever the panels cost is an overkill. A 1kW grid tied can generate up to 5kW per day in good sunshine. The panels can also be used if there is any future plan for using PV which I think as the loadshedding continues for at least the next 6 years could be part of any power plan going forward.
    Sorry, my question on AC vs DC on the element was genuine, as I donít know how these things work.

    I agree with your wrt to the benefits of going for a Ďbiggerí integrated approach with the grid-tied system, but based on the OPís question, it may indeed be overkill, as we donít know his ultimate plan behind his setup.

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    Default Re: Solar Geyser

    Quote Originally Posted by Fishing1 View Post
    I don't know how effecient a inverter with solar panels is compared to a direct heating system? I dont see it often presume there is a reason for it.
    The common solutions are not always a yardstick. In the last year I met 3 guys installing PV systems that did not know how a grid tied system works. That gives an indication of the level of know how around PV installers.

    I would guess for each grid tied there are perhaps 9+ normal back up sysyems. Yet we find in the devoloped world more grid tied systems are in use due to their better ROI and saving power cost all the time. You gain whatever PV energy you can yield even in low radiation on clouded days.

    One can also compare grid tied to using a heat pump that uses about 33% of a normal grid element. Savings are generated over the life of the heat pump and pays for itself in a much shorter period than the common flat panel or tubes systems.

  10. #10
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    Default Re: Solar Geyser

    Future plans are uncertain at this point.
    Which of the two systems is more effective?

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    Default Re: Solar Geyser

    Quote Originally Posted by DeVilliers View Post
    Future plans are uncertain at this point.
    Which of the two systems is more effective?
    Cannot answer. Both would heat the water to 60 degrees during the day. The grid tie can power a portion of your power used by the fridge which a tube system cannot. The tubes might boil the geyser water but is it really needed?

    The tubes might heat to 60 by say 12h00 and the grid tied by 15h00. This could imply the tubes are more efficient?

  12. #12
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    Default Re: Solar Geyser

    True. Grid tie, might be better

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    Default Re: Solar Geyser

    Quote Originally Posted by DeVilliers View Post
    True. Grid tie, might be better
    My problem is to work out efficiency.

    When I was small I was told Effec=Output power/Input power= a certain %.

    In this case our output is hot water/Input is the heat of the sun = cannot get an answer

    The final answer would be in the actual application. Many variables must be known first.
    Last edited by ekkekan; 2020/01/25 at 07:50 PM.

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    Default Re: Solar Geyser

    Well, actual application would be to get hot water with little or no help from Eskom

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    Default Re: Solar Geyser

    Quote Originally Posted by PRA View Post
    This is worth considering ............
    Just be careful dealing with this company - https://www.hellopeter.com/energy-sp...k-scam-2844474
    Metalian Maxi

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    Default Re: Solar Geyser

    Okay Im really confused now. If you have four panels of say 300w .How many volts would it produce.?Is this pumped into a dc element using some electric gizmo that alters it somehow. ?

    What is the thinking of using a dc element.What happens if you pump dc into an ac element. Will it heat.How does an element (ac) know what voltage its intended for.

    Being a resistive element does it care if it gets 120v or 240 v.
    The geyserwise dc/ac element that is used is apparently not a resistive element. Is this true only for the dc side of the element or is it for both the ac and dc . Or is it one element that can be fed by dc and ac?(in other words is it one or two elements combined in one tube.
    There can be an advantage to ptc element that I can immediately see and that is a built in saftey factor. It should never be able to create superheated steam in case of a thermostat failure.
    I suspect the pv solar geyser would perform better if no one is at home. If you have a maid using water during the day it may not be ablke to catch up. I know this applies to any solar system but perhaps more so with pv

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    Default Re: Solar Geyser

    Quote Originally Posted by Fishing1 View Post
    I got a flat panel system it is connected directly to the geyser. The hot water pumps into the geyser. The vacuum tubes work much better....
    We installed evacuated tubes end of last year. They are very effective and we had water up to 78 degrees on a hot day.
    2018 Toyota Fortuner 2.8 GD-6 4x4 AT
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  18. #18
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    Default Re: Solar Geyser

    Quote Originally Posted by plunger View Post
    Okay Im really confused now. If you have four panels of say 300w .How many volts would it produce.?Is this pumped into a dc element using some electric gizmo that alters it somehow. ?
    The voltage of the panels one can check by connecting a resistor over a panel that is about 3.9 ohm. Alternatively one can connect 2 car H1/H4 headlight globes in series and measure the voltage produced by the panel. A 300W panel can have a full load voltage of 30-39V and 8.5-9A. These values are for a Canadian solar 300W panel.
    Thus 4 panels can give 120-156V. Amp into a normal 3kW AC element with 16 ohm resistance is about 7.5A. Thus the heat generated will be W=120x7.5=900W+. No need to waste money to get a 800W DC element. Paying for the benefit that it cannot burm out.


    A resitive load does not care if it gets AC or DC. The older 12V 50W downlights which were so popular all worked on AC but it was just to same cost for the rectifier as they work just as well on 12V DC.


    What is the thinking of using a dc element.What happens if you pump dc into an ac element. Will it heat.How does an element (ac) know what voltage its intended for.
    The element just produces the heat=power based on the actual voltage applied which determine the current which is a function of the resistance which is fixed for the element. It all get down to Watts=VoltsxAmps and Volts=AmpsxResistance.

    Being a resistive element does it care if it gets 120v or 240 v.
    The geyserwise dc/ac element that is used is apparently not a resistive element. Is this true only for the dc side of the element or is it for both the ac and dc . Or is it one element that can be fed by dc and ac?(in other words is it one or two elements combined in one tube.
    The DC elements are made of a special material which does not burn out as it limits current when getting hot. The same way as a PTC heater element which is usedon AC. It does not matter if supplied by AC or DC.
    There can be an advantage to ptc element that I can immediately see and that is a built in saftey factor. It should never be able to create superheated steam in case of a thermostat failure.
    If the thermostat should fail you should not get steam as the safety valve on the geyser would open and blow off. Yes the PTC element has the safety advantage but bear in mind none of our normal geysers in use by many millions give problems if the thermostat does not switch off.

    I suspect the pv solar geyser would perform better if no one is at home. If you have a maid using water during the day it may not be ablke to catch up. I know this applies to any solar system but perhaps more so with pv
    Yes you are spot on. That is why I indicated it depends on the actual application. With regular use the grid tied inverter option could be more desireable. One will need to look at the pattern hot water is used. Using say 8 x 300W panels to provide about 2400W from 11h to 15h00 can help if hot water is used during the day.
    This is perhaps applicable to using the panels without the grid tied inverter. 4 panels with grid tied inverter costs about R11 000 for equipment. Thus PV could actually be cheaper than tubes or flat panel and provide AC for other loads as indicated in a previous post.
    Last edited by ekkekan; 2020/01/26 at 10:38 AM.

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    Default Re: Solar Geyser

    Did is a while back. 3x 300w panels in serie. 120vdc dirctly onto element. AC thermostate does not work due to arch. Panels was facing west and there was a tree that gave shade from 16.00. Boiled the geyser in day 3. 100lt geyser. Started with cold water. You need a DC thermostat.

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    Default Re: Solar Geyser

    Anyone dealt with livestainable.co.za before?
    They have a good price on pv solar system.

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