Thermodynamic Geyser

SauRoNZA

SauRoNZA

Honorary Master
Joined
Jul 6, 2010
Messages
61,473
Reaction score
23,199
Location
Cape Town
Part of my exploration with going solar has been the option to replace my existing electric geyser with a thermo dynamic setup from https://www.energie.pt

Thing is it’s pretty damn expensive at almost 40k and this on top of an almost 300k solar installation is a tough one to swallow.

I wonder if I’d not be better off just running the normal geyser hotter during the day off solar up to say 75-degrees and then the moment battery kicks in to drop it to 50 or so and save on power.

Then I can either top it up from battery or just pay for it as I can’t go off grid completely anyway.

On the flip side I considered doing the geyser first and then seeing if I really need such a massive solar setup still.

So does anyone have one? Has it been worth it?
 
SauRoNZA said:
I wonder if I’d not be better off just running the normal geyser hotter during the day off solar up to say 75-degrees and then the moment battery kicks in to drop it to 50 or so and save on power.
Click to expand...

Why not go for a heat pump? you get more units of heat than power that you put in
 
Looking at the link it looks like they have combined a solar geyser with a heat pump, interesting

But the cost, eina!
 
Leno said:
Why not go for a heat pump? you get more units of heat than power that you put in
Click to expand...

Yeah as per your last post this is pretty much a heat pump as well.

I don’t think doing just a heat pump and then still needing high amounts of electricity to run it would make much sense, may as well just stick to what I have now then.

Over 10 years it comes down to about R300 odd a month which isn’t that crazy and should save more than that, especially with the cost from Eskom escalating.

On the flip side when this geyser pops which is likely in the next year or two then I could look at a more economical smaller element unit or make an agreement with the insurance to help fund other options.
 
If your solar journey is going to end off grid one day, you cannot plan any heating system based on electricity, solar geysers are very efficient, you hardly need to run the backup element if you size your system generously and control it using some basic tech. Gas can be used to backup a solar setup so you're not limited at all.

Heat pumps generally move over 3 times the heat it consumes in electricity, but you can never go off grid using it.
 
Kawak said:
If your solar journey is going to end off grid one day, you cannot plan any heating system based on electricity, solar geysers are very efficient, you hardly need to run the backup element if you size your system generously and control it using some basic tech. Gas can be used to backup a solar setup so you're not limited at all.

Heat pumps generally move over 3 times the heat it consumes in electricity, but you can never go off grid using it.
Click to expand...

Have absolutely no interest in gas in any way shape or form.

Doubtful it will ever be off grid going by how the CoCT operates.

The problem with conventional solar geysers (that aren’t just PV anyway) is that it seems none of them last and always require maintenance.
 
SauRoNZA said:
Have absolutely no interest in gas in any way shape or form.

Doubtful it will ever be off grid going by how the CoCT operates.

The problem with conventional solar geysers (that aren’t just PV anyway) is that it seems none of them last and always require maintenance.
Click to expand...

"Conventional" solar can be extremely maintenance free. My solar journey started with geysers back in 2007, spoke to a friend who manufactures solar geysers, was advised to rather install low pressure vacuum tubes, best decision. Got the stainless steel tanks and they are still rust free and fully working till this day, I have since added all sorts of smart controllers and valves to that system, hardly ever need to use electricity (gauteng so not as much cloud and rain in winter). If you're in the Cape you may want to look into heat pumps.

As with CoCT rules, I have worry we will all go the same route across the country once eskom completes its split, there may be a grid charge for all properties over a certain value, that charge could make it worthwhile to go off grid, don't write gas off yet.
 
It really seems that as time goes on the need to complex ways to heat water disappears. I know of 2 people that have gotten rid of their flat plate or vacuum tubes to just make space for more PV panels, many more are planning to go this route. Every year PV becomes cheaper, they are far less maintenance than vacuum tubes or heat pumps. Sure, its less efficient but who cares when total cost of ownership is less and the excess power can also be used in other places once you have overheated your geyser to become a thermal battery. This is of course if you have enough roof space for more PV.
 
Kawak said:
"Conventional" solar can be extremely maintenance free. My solar journey started with geysers back in 2007, spoke to a friend who manufactures solar geysers, was advised to rather install low pressure vacuum tubes, best decision. Got the stainless steel tanks and they are still rust free and fully working till this day, I have since added all sorts of smart controllers and valves to that system, hardly ever need to use electricity (gauteng so not as much cloud and rain in winter). If you're in the Cape you may want to look into heat pumps.

As with CoCT rules, I have worry we will all go the same route across the country once eskom completes its split, there may be a grid charge for all properties over a certain value, that charge could make it worthwhile to go off grid, don't write gas off yet.
Click to expand...

Oh you meant the entire geyser in the roof type of setups.

Yeah that’s an option I had considered originally especially to move my geyser more centrally in the house.

Thing is that also costs quite a bit of money and the thermo dynamic isn’t so far behind then.

Everyone I know of that had evacuated tube setups retrofitted had some form of problems over a couple of years, which is more what I was referring to.

The thing with the thermodynamic system is that it still works at night and uses very little power so it could happily run off the solar battery backup without a risk of drawing too much power or stealing capacity.
 
calypso said:
It really seems that as time goes on the need to complex ways to heat water disappears. I know of 2 people that have gotten rid of their flat plate or vacuum tubes to just make space for more PV panels, many more are planning to go this route. Every year PV becomes cheaper, they are far less maintenance than vacuum tubes or heat pumps. Sure, its less efficient but who cares when total cost of ownership is less and the excess power can also be used in other places once you have overheated your geyser to become a thermal battery. This is of course if you have enough roof space for more PV.
Click to expand...

This is exactly what one installer told is to simply run the geyser off the PV during the day and with my inclination towards Smart things to then simply lower the temperature during the night and turn it off early as possible, kind of why I have the thread.

His opinion is the 2ish PV panels cost all of 10k and will run forever and is included in the total solar project anyway.

They also didn’t want to hook it up to the battery unless I really wanted to, but likely more a concern of total peak draw at any one time which I can understand.

Thing is let’s say I don’t put it on the battery and pay for it off Eskom and use 3-4kw a day then I’m still paying R250-R300 a day which goes up in time and means I may as well buy the thermo system now.

Part of the thing is that I can pay for the thermodynamic system now in cash no problem and I’m inclined to do that to effectively fund my solar project and pay that almost in cash start of next year.

If I can put more money away now I can win later, so bit of a catch 22.
 
SauRoNZA said:
This is exactly what one installer told is to simply run the geyser off the PV during the day and with my inclination towards Smart things to then simply lower the temperature during the night and turn it off early as possible, kind of why I have the thread.

His opinion is the 2ish PV panels cost all of 10k and will run forever and is included in the total solar project anyway.

They also didn’t want to hook it up to the battery unless I really wanted to, but likely more a concern of total peak draw at any one time which I can understand.

Thing is let’s say I don’t put it on the battery and pay for it off Eskom and use 3-4kw a day then I’m still paying R250-R300 a day which goes up in time and means I may as well buy the thermo system now.

Part of the thing is that I can pay for the thermodynamic system now in cash no problem and I’m inclined to do that to effectively fund my solar project and pay that almost in cash start of next year.

If I can put more money away now I can win later, so bit of a catch 22.
Click to expand...
Old school geyser + Geyserwise + 2kw element + thermostatic mixing valve + Home Assistant = Winning at life.
 
calypso said:
Old school geyser + Geyserwise + 2kw element + thermostatic mixing valve + Home Assistant = Winning at life.
Click to expand...

Geyserwise **** the bed so I made my own one with a Sonoff which then exploded after a year.

Doing it again would put the CBI Astute in and then just monitor the temperature with a Sonoff TH without it being a relay.

What does the mixing valve do?

Also why the 2kw element? Purely for solar draw? Wouldn’t a 3kw just do it faster?
 
SauRoNZA said:
Geyserwise **** the bed so I made my own one with a Sonoff which then exploded after a year.

Doing it again would put the CBI Astute in and then just monitor the temperature with a Sonoff TH without it being a relay.

What does the mixing valve do?

Also why the 2kw element? Purely for solar draw? Wouldn’t a 3kw just do it faster?
Click to expand...

Mixing valve is just so the water temp coming out of the geyser is consistent.
Smaller element just so its less load on the inverter, also means it can run for longer (while PV is available).
 
SauRoNZA said:
Aaah basically to stop you burning yourself with 95-degree water because the PV was pumping all morning.

Always wondered how that works.
Click to expand...
Yep yep, and its just a passive unpowered device, so set it up and forget about it.
 
SauRoNZA said:
Oh you meant the entire geyser in the roof type of setups.

Yeah that’s an option I had considered originally especially to move my geyser more centrally in the house.

Thing is that also costs quite a bit of money and the thermo dynamic isn’t so far behind then.

Everyone I know of that had evacuated tube setups retrofitted had some form of problems over a couple of years, which is more what I was referring to.

The thing with the thermodynamic system is that it still works at night and uses very little power so it could happily run off the solar battery backup without a risk of drawing too much power or stealing capacity.
Click to expand...
You definitely shouldn't count on batteries to run your heat pump, it may be a small amount but it draws huge amounts of current starting up, you could find your inverter not able to cope with that.

shop.thesunpays.co.za

Stainless Steel - Low Pressure 150L Solar Geyser With Auxiliary Tank (2-Year Guarantee)

Includes: 150L, 0.31mm SUS304 s/steel tank with stainless steel outer shell Flat/pitched roof stand (1.5mm galvanized and painted) 15 x 2mm vacuum tubes (designed for 38mm diameter hail) and Stainless steel auxiliary tank Excludes: Plumbing fittings and piping Element & thermostat Element plug...
shop.thesunpays.co.za shop.thesunpays.co.za

Was on the forum a few days ago so did this search, it's nowhere near as expensive, also, I fitted 3 of these in a chain, one feeding another feeding another then into the house. Practically eliminates having to use electric backup as the final tank is only ever fed hot water, i later added solenoid valves controlled by sonoff switches between the geysers as well as before main water entry, low pressure is great this way as you can keep a full tank of hot water for the entire night if no cold water is added, just fit a decent small pressure pump so you can still enjoy a strong shower.
 
Kawak said:
You definitely shouldn't count on batteries to run your heat pump, it may be a small amount but it draws huge amounts of current starting up, you could find your inverter not able to cope with that.

shop.thesunpays.co.za

Stainless Steel - Low Pressure 150L Solar Geyser With Auxiliary Tank (2-Year Guarantee)

Includes: 150L, 0.31mm SUS304 s/steel tank with stainless steel outer shell Flat/pitched roof stand (1.5mm galvanized and painted) 15 x 2mm vacuum tubes (designed for 38mm diameter hail) and Stainless steel auxiliary tank Excludes: Plumbing fittings and piping Element & thermostat Element plug...
shop.thesunpays.co.za shop.thesunpays.co.za

Was on the forum a few days ago so did this search, it's nowhere near as expensive, also, I fitted 3 of these in a chain, one feeding another feeding another then into the house. Practically eliminates having to use electric backup as the final tank is only ever fed hot water, i later added solenoid valves controlled by sonoff switches between the geysers as well as before main water entry, low pressure is great this way as you can keep a full tank of hot water for the entire night if no cold water is added, just fit a decent small pressure pump so you can still enjoy a strong shower.
Click to expand...
Why 3?
 
calypso said:
Why 3?
Click to expand...
Abundance of hot water, 3 in the house with 4 bathrooms, i used to have friends and family over frequently, it helps that the tank we draw from never sees cold water. Geyser controller frequently registers 99c, water is easily over 75 in the morning after we all take a shower before bed, so I still have plenty of hot water for the morning showers after workout.
 
Kawak said:
You definitely shouldn't count on batteries to run your heat pump, it may be a small amount but it draws huge amounts of current starting up, you could find your inverter not able to cope with that.

shop.thesunpays.co.za

Stainless Steel - Low Pressure 150L Solar Geyser With Auxiliary Tank (2-Year Guarantee)

Includes: 150L, 0.31mm SUS304 s/steel tank with stainless steel outer shell Flat/pitched roof stand (1.5mm galvanized and painted) 15 x 2mm vacuum tubes (designed for 38mm diameter hail) and Stainless steel auxiliary tank Excludes: Plumbing fittings and piping Element & thermostat Element plug...
shop.thesunpays.co.za shop.thesunpays.co.za

Was on the forum a few days ago so did this search, it's nowhere near as expensive, also, I fitted 3 of these in a chain, one feeding another feeding another then into the house. Practically eliminates having to use electric backup as the final tank is only ever fed hot water, i later added solenoid valves controlled by sonoff switches between the geysers as well as before main water entry, low pressure is great this way as you can keep a full tank of hot water for the entire night if no cold water is added, just fit a decent small pressure pump so you can still enjoy a strong shower.
Click to expand...

Hence the thermo dynamic option as it’s made to run off solar and backup battery.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X