I understand the concept (not the details) of PV Diverters for 1:1 electrical boilers that follow the PV production very nicely to avoid PV injection into the grid.
But nowadays a lot of heat pump manufactures advertise with things like smart grid ready, SG Ready, PV diverter, solar pv ready, … (eg. Solar PV Ready Heat Pumps by Stiebel Eltron). But can they do the same so nicely as a 1:1 electrical boiler? I don’t think it is a good idea for the lifetime to just interrupt the process of a heat pump?
As an example my heatpump (in red), PV production (blue) and my situation to the grid (yellow: + is import ; - is export). The only thing I do is programming to heat water starting from 13:00 as the chance is bigger there is sun. As you can see: it fails big at avoiding export or import…
Here’s the strategy that I use with my PV + battery + heat pump: forecast how much solar generation is expected today, and check how much energy in stored in the battery. I’ve setup the heat pump to start the water cycle at 12:00, or when the battery reaches 90%. On cloudy days, it only heats up to 45C, but on days that are forecasted to have an excess of PV, it will heat up to higher temperature.
Of course, this does rely on having a storage battery to even out the fluctuation in generated power. It’s much harder to have a heat pump respond in real-time to PV.
Something that might work for you is to look at the current generation & the forecast for the next half-an-hour. When you’re generating (say) more than 500W and the forecast suggests that you might generate at least 500W for the next half-hour, then turn on the heat pump. Looking at your chart, and assuming the forecasts are reasonably accurate, this would have the HP running from 10am until 1:30pm. (You’ll want to adjust the threshold to include your house load too).
Running in 30 minute cycles will probably work okay, without being too detrimental to the heat pump, but do check the manufacturers recommendations for minimum run time.
I don’t think any heat pump will be able to do load matching as closely as a resistive heating PV divert or battery inverter. HP compressors are not designed to be controlled in this way.
My Samsung Gen6 ASHP has got a solar PV input and a Smart Grid Input, it’s quite simplistic: when solar PV input is active the ASHP will run a DHW cycle and bump up the indoorT set-point by a couple of degrees for heating for couple of degrees less for cooling:
Sorry for the late answer! Thank you @Timbones and @glyn.hudson. We don’t have a home battery, because financially it doesn’t seem that interesting (at least in Belgium). We also don’t have the “normal” central heating: our passive house does reasonably well without. We use a simple electric heater during some colder days/hours (consumed about 125 kWh last winter in our living room). This means that our heatpump is for domestic hot water only (and ventilation).
So I guess it is possible that a cloud passes by and that electricity is imported from the grid during it heatpump cycle.
Our heatpump consumes about 600 Watt during its cycle. Would it be possible to produce a heatpump that can have different ‘levels’. Eg. 300 Watt cycle if there is not much sun (of course it takes double as long) and 600 Watt cycle if there is more sun. If this could be possible: are they on the market already?
Hi! Sorry for bothering you, i also have a samsung ashp with smart grid input…how the hell should the input work?
Do you have an idea if it works as a dry contact (close=pv producing, open=pv not producing)?
I’m just astonished about how few informations samsung is giving about these features! And of course, any local installer doesnt know anything more than connecting water tubes…
It’s in the manual, page 42 of the controller. I don’t think it’s a particularly useful feature, it’s too simplistic to be effective and makes the ASHP run inefficiently. Since most PV systems now include a battery, an input like this is redundant, since the battery can buffer the solar PV generation and the DHW scheduled for the best time.
I agree, but in my case for the moment my PV does not include a battery…
Anyway, the ASHP for me has no way to be turned ON from a dry contact, the only way to force it ON is trough the control panel or via smart things app…so dumb.
do you know if the smart grid contact could just work for it, as a dry contact with a simple smart switch?
It feels like the “load shedding” feature (for managing constrained electrical connections and the “tariff” feature (for forcing an increased setpoint during cheap periods) aka “SG Ready” has been re-labelled by the marketing department here as a PV specific feature.
Yes, it would. The default operation is to switch on DHW and to increase room temperate or water outlet temperature by 2C. You will need to enable it in settings FSV #5081
Are you sure about the ‘most PV systems now include a battery’? Most of the articles I read about the Belgium market seem to agree that a battery at home isn’t worth its money as ‘the return on investment’ is too low. In summer time you don’t make thát much profit. You could in winter time… at least if the sun would shine a bit more ;-).
For me it seems that economically and environmentally it would be better to do a ‘best effort’ to run your heat pump at times that you think an export of excess solar energy can be avoided. The battery that you didn’t buy will be more suited for e-bikes, BEVs, battery plants, … At least, that’s my IMHO… ATM.
Still it would be useful if heat pumps could be run in “steps”. Eg. 600 W to heat up water in 1 hour ór 300 W to heat up the same amount in 2 hours. But I don’t know if heat pumps can be technically easily build that way. I just know that I can use my bike pump like that .
For Daikin at least, there is an option to have a pulse meter on the grid supply and it will restrict the heat pump somewhat to the available export (depending on the minimum power requirements of the unit.
This is how I have mine set but as the minimum power requirement for my heat pump is 1kw it is only somewhat useful.
You will see for connector block X5M;
Pins 3&4 - For a pulse meter connected to the incoming main supply
Pins 9&10 - For the SG1 relay (recommended on / forced on)
Pins 5&6 - For the SG2 relay (Forced off or Forced on)
You also have to configure the energy meter on the Daikin (Page 209)
Many thanks @glyn.hudson for sharing PV Control settings for Samsung Gen6 ASHP. Can you please let me know if the Solar PV output needs to pass through an invertor ( to cover DC to AC) before it connects to Samsung Gen6 ASHP to supply additional power generated for the hot water mode. Apologies in advance if i got this wrong as Im very new to Samsung Gen6 ASHP. I’m struggling to understand how Solar power (DC) can be used to heat water( immersion is a 230v AC)
In principle, there’s absolutely no reason why you cannot use direct current to heat water - in fact, I believe one of the commercial solar diverters does, from the mains rectified as part of the controlling process to balance and thus ensure zero nett power transfer to or from the grid. The immersion heater itself doesn’t care whether it gets 230 V rms a.c. or 230 V d.c., the power output is the same.
In practice, it’s not so easy because a solar panel is essentially a constant current device, so it would be necessary to have a variable resistance immersion heater to extract maximum power - rather impractical. In reality therefore, you do need to put the direct current into the inverter, which also serves to match the load to the P.V. panels’ output to obtain the best power transfer. And of course, as the inverter output is now mixed in with the mains, you can top up with the mains if there’s not enough solar power; or if there’s too much, use it for other things or export it.
So, the answer to
is: in theory you can, in practice you cannot without converting it to a.c.
.