@toodles honestly I don't remain convinced. I thought the whole point of sunamp was to heat internally to very high temperatures (well over 100°) and then release this to heat water. This is why the footprint is much smaller as you are packing in more heat. Resistive heating at night is a 1:1 efficiency. An ashp will give you heat, but over 70° it's pointless as the efficiency trends downwards to pointless. You can also rule out solar diversion in the winter months as you won't get enough solar PV to be meaningful.

You may as well just get a power shower and save yourself the hassle? Maybe with boiler taps on timers for the sinks? You would save thousands and save all that space. You could then get the ashp for heating and maybe a battery to reduce your grid demand. 

I don't want to be a downer and wish you the best of luck with things. But I do think you're going to pay a lot of money for something which maybe doesn't deliver what you really want for a decent cost

@toodles if you haven't already, reach out for some real world experience from the large scale ashp and sunamp trial

https://forum.ovoenergy.com/my-smart-home-138/energy-storage-vs-heat-batteries-what-s-the-difference-and-which-is-better-9928

I am sure some of the trialists will answer many of your sunamp questions if you post queries. 

So many replies and comments! To reply to some (but not necessarily in the right order). I have limited space, a failing 14.5 year old gas boiler, a small airing cupboard that is too shallow for any of the modern ASHP type tanks or the intelligent tanks with lots of pipework. My wife and I have visual handicaps and neither of us are able to drive so EV’s are not in the equation. I have newly installed Solar PV (8.1kWp.) and am waiting on the arrival of Tesla Powerwall but Godot seems to be the courier for this.

Next survey for an ASHP install is this Tuesday and I am considering Daikin ASHP and Sunamp Thermino. Model of ASHP yet to be decided after discussion with installers. I am aware of different models and may consider an HT model [I need to discuss the SCOP with the installers] but run space heating at 35 degrees with HW running at a minimum of 65 degrees (63-65 degrees required by Thermino). I would like a better interface for the Thermino but I’ll not lose any sleep over the poor granularity [half / fully charged] of the status lights. The main thermal charging will be from the ASHP for the Thermino but, grid, battery, solar would be regarded as a backup source. I’m with Octopus Energy and as I am on Agile tariffs for import and export, I’ll be looking closely into any changes in possible tariffs that are offered as I don’t think that Octopus Go would apply in my case (not as yet anyway). There may be a need to replace a few radiators err… emitters and the bathroom will benefit from a change to a towel rail version anyway. Charging the Thermino from the ASHP, even at say 70 degrees will still have a better COP than using grid power as was mentioned, resistive charging would only be at a COP of 1; if there is spare solar energy in the summer, this might be economic - depending on the export to gris tariff and state of the battery charge.

Lots of variables there I know, but trial and error and experience may have to be employed; I am getting rid of gas ASAP and the boiler is the last element in need of changing.

I note that someone commented in the ASHP and Sunamp Forum that the unit got very hot - this is contrary to everything I have heard on this subject. As to the unit running at over 100 degrees C, I think that is possibly erroneous or I have misunderstood the way the PCM works; as long as 63-65 degrees is supplied by the ASHP, the PCM will change state and the system will provide hot water and would need a regulator for safety to avoid scalding water temperatures.

Regards, Toodles

@toodles

Let me first of all say that we don't have a Sunamp and don't know anyone who does, but as an Engineer I prefer to read the technical specifications as well as all the glossy advertisement brochures.

I have just been watching various video's and reading some of the documentation on the Sunamp website, and they would appear to be quite an interesting proposition for anyone who suffers from limited space as you have repeatedly stated.

Looking at the various models available, I would suggest that you may wish to consider the Thermino-iPV model along with a suitable electrical power diverter.

As you now have a size-able solar PV system, and soon to be installed battery storage, I would asses that much, if not all, of your heating and hot water requirements could be provided from Spring through to Autumn from the Sun. Obviously, that very much depends upon your electrical energy and hot water usage.

We have a 4kW solar PV system, which does indeed provide the vast majority of the hot water needs of two adults, during the specified period, and also helps to provide some home heating on the cooler days. Since installing the solar PV it also reduced our annual electricity consumption by approximately 50%, which could be even more if we had battery storage.

Obviously the final decision is for you to make, but if I was in your position I would probably be looking at the following options.

Install the largest Sunamp that space permits, along with a suitable electrical power diverter to fully utilise excess solar generation. Unless you use excessive amounts of hot water, this should possibly allow you to have all your hot water requirements from Spring through to Autumn provided free of charge from the Sun. You should also find that most days, there is sufficient PV generation available to also charge your battery storage, and supply much if not all of your in house electrical demand. You should therefore require very little import from the grid and would not need to run your proposed heat pump for much of this period. During any periods of low solar generation it may be possible to top up both the Sunamp and battery storage via cheaper overnight electricity with a suitable electricity tariff.

During the Winter months you would possibly be able to fully use any solar PV generation in the following manner. To power your heat pump when it is required, charge your battery storage for later use or heat your Sunamp. With your proposed setup you will have quite a number of options which may allow you to reduce your energy consumption, reduce your energy bills, or possibly both.

If you have not already done so, I would suggest that you go on to the Sunamp website and explore the various options. I do believe that the website contains a list of installers and also different heat pump manufacturers that are compatible with their equipment.

Please keep us all informed as you discover the best route forward.

Thank you Derek, I was beginning to wonder if I am the only person thinking on the lines I outlined! I have studied the Sunamp Site and all the technical information and viewed many Youtube presentations during the last six months [including those from Emilie from Ecobubl] and have also spent some hours doing similar things with ASHP manufacturers and installation videos. For instance, I have looked at Vaillant but because of the gas they use (propane?) I cannot site such units at the back of the property as I would be too near windows and doors. With Daikin using R32, this restriction is removed and thus there is more flexibility in siting the external unit.

Regarding the choice of Sunamp Thermino, I would like the 200 litre equivalent version; there are two of us and the bathroom hasn’t a bath, just a shower (currently pumped water from within the airing cupboard) and I’m told that with a direct system [the cold water tank in the loft will go] we will not need the pump. The 99 litre HWT has served the two of us with virtually no hot water supply failures, this is possibly because the washing machine and the dishwasher are cold-fill only. The 200 litre equivalent Sunamp Thermino should supply all we need quite happily.

Regarding the model I have been considering the HP series so that supply from the heat pump is backed up by the grid supply (which at various times would actually be from ‘home brewed’ or stored energy. I note the iPV version is intended to be connected to a ‘boiler’ and I suspect that this is to do with the elevated LWT of a conventional boiler and possibly also to do with the protocols where the Sunamp talks to the boiler - this may not be compatible with the protocol used with heat pumps. If it is just the temperature and not a protocol incompatibility, then maybe a high temperature capable heat pump would work. This is a matter that I’ll take up with the installers and Sunamp as well. I would hope that an experienced installer would be more knowledgable than I am!

I do attempt to do my homework before investing such large sums of money and am not afraid of getting ‘down and dirty’ with the technical data; some times, the information on the website just doesn’t go far enough for probing minds;-)))

Regards,

Toodles

@toodles 

You have clearly done a lot of research, always good to hear more about the different options from others like yourself. I am sure we would all be interested how you get on. 

I would be interested to hear what the installers say about the following options when you chat to them if you don't mind sharing. 

1. Using your existing cylinder and one of the newer high temperature heat pumps

Vs

2. A regular heat pump and a sunamp battery. 

I don't know how much the sunamp setup would be? How much extra electric battery capacity could you purchase as an alternative to grab cheap electricity that could be useful for space heating and hot water via your ashp?

I wonder why heat batteries are not as popular as hot water tanks generally? It is  quite a niche market. Do you think it is cost? 

Good luck whatever you end up doing. 

Good points well made! An HT ASHP into the existing tank is worth a thought but, gains me no space unfortunately - but worth considering! When the gas boiler, BG330 [Glow worm] is replaced with a ‘Hydrobox’, I’ll lose some more space anyway as it is slightly larger.

The current silly energy prices are doing very little to encourage families to go green I know; I think I will be using ‘off peak’ energy whenever possible. Running the hot water cycle at night is a given really, as is charging any storage so that it can be used during peak demand times and when solar PV is unable to assist. The heat loss from the Sunamp units is much lower than the alternative systems so night time charging will fulfil all our needs. From what I have read, the weakness with the Sunamp is the inability to programme it to charge from the grid only at certain times - I think the grid versions needs to be connected and switched on at all times thus a timer or controller will not work with the HP versions - I will see if the iPV version can work with an HT ASHP.

Regards, Toodles 

@jeff

I would have thought that the other way around would be a better option. High temperature ASHP with the Sunamp, since it needs to be heated to approximately 65C for the phase change to fully operate. A lower temperature heat pump with the present water cylinder, since it only really needs to be heated to about 45C for normal use. It should also be noted that in 'hard water' areas, heating water much above 60C leads to much increased scale formation.

@toodles

Have you considered a 'Monobloc' heat pump rather than a split system, which does not require the indoor hydrobox?

The proposal to use a low temperature HP with the existing tank may be problematical as the heat exchanger in the tank is designed for a higher temperature boiler and I suspect that a small tank at the lower temperature (even were it able to transfer the energy properly) would be short on required calories - we get by at present but the water is at 60 degrees; we do have a water softener so the hard water problem does not rear its’ ugly head here. As to using a monobloc style ASHP, I have been considering these but, there is still a certain amount of gubbins required inside (which of course is partly what the hydrobox does otherwise.

Regards, Toodle

Posted by: @derek-m

@jeff

I would have thought that the other way around would be a better option. High temperature ASHP with the Sunamp, since it needs to be heated to approximately 65C for the phase change to fully operate. A lower temperature heat pump with the present water cylinder, since it only really needs to be heated to about 45C for normal use. It should also be noted that in 'hard water' areas, heating water much above 60C leads to much increased scale formation.

That is an interesting point.

So we have been told the current tank will struggle with a low temperature heat pump due to the coil in the current tank. So the old tank needs to go.

Are you saying you think that may not be correct? Do you think he can simply use his existing tank with a low temperature heat pump?

In which can there would be no need for a special tank or a sunamp or a high temperature heat pump?

This is important as he doesn't need a high temperature heat pump for space heating. 

@jeff

I suppose that much depends on the size of the cylinder, how much hot water is used, and how frequently it is used. The cylinder should still heat up, but at a slower rate, even with a smaller heating coil.

Spring through to Autumn the cylinder could be heated to 60C using solar PV. During the Winter months the cylinder could again be heated to 60C, using a cheaper overnight tariff, either directly by an immersion heater, via an ASHP, but with a lower COP, or a combination of both. Heat to 50C using the heat pump, then up to 60C using the immersion heater. Any available solar during the day could be used to keep the cylinder topped up.

I suppose to be on the safe side, it could be prudent to install a high temperature heat pump, so that should it be decided to remove the water cylinder and install a Sunamp at a later date it should be fairly straightforward. The only thing that may 'throw a spanner in the works' is if it is not possible to get an installer to fit a heat pump with the present water cylinder.