I have successfully managed to control my heat pump via ebusd as well as getting current data from my PV panels. Now I want to control my hotwater, if there are more than 4KW available on my PV panels.
Since I do not have a heating rod in my hotwater buffer, I don't want to turn my heat pump to often.
Before I implement such a logic myself, I want to ask if a similar problem has already been solved and I can reuse it and adjust it to my purpose.
A PID regulator seems not to fit since this would require a heating rod inside my buffer.
@Colin thanks for your reply. Here are some more details:
In general I want to use as much of the produced energy for my own house, because we only get a few cents here in germany for each kWh we feed the electricity network with.
Therefor, I want to use it to increase the hotwater setpoint.
My heat pump has two modes for hotwater, a energy saving mode and a usual mode. The usual mode is set to 50°C and the setpoint for the energy saving mode is set to 35°C.
The usual mode is activated from 12pm-3pm and the rest of the time the energy saving mode is active.
In order to control the heat pump I can change the mode to a specific setpoint and the heatpump is heating the buffer to the desired value. (+~2°C more)
So my idea was, to set the setpoint to 55°C once I have more than ~4kW free energy on my panels for at least 10 minutes. Then I would change the value to 55°C and once it has been heated up, I will switch it back to the previouse mode.
I also need to take care of not turning my heat pump on and off too often, even if there are enough free energy from my panels due to the wear effect.
I can even imagine to take weather data like predicted solar generation into account to avoid switching on the heat pump if it is very cloudy and it is unlikely that the solar generation will be more than 4kW for at least 30 minutes.
Do you have a tempering valve on your heatpump output (one that mixes hot and cold water to get to a safe temperature ?)
What is the maximum power draw of your Heat pump compressor ?
Do you have realtime visibility on your House Power consumption and Solar panel production
What size is the water tank for the heatpump ?
Do you have room for a 2nd water tank ?
What is the maximum temperature the heatpump compressor can raise the water to ?
We use a stadnard resisitive hot water element tank here in Australia where we can take the water to a maximum temperature of 70c.
I wanted to ensure that if we had a number of day of cold/overcast weather we still have optimal hot water - so we put a 2nd tank in front of the first.
Once the first tank (which is what feeds the house) is up to temperature, we then cascade over to the 2nd tank and start heating that.
THe output of the 2nd tank feeds the input of the first tank
This means that we have a maximum of 650L of hot water available at theoretically 70c - however it is only in summer that we have enough solar to fill our batteries and heat both water tanks - but during peiord of multiple cloudy days and low solar output we were able to ride through without having to revert to mains input to heat any water
Generally on a heatpump system the compressor are very efficient and will only draw about 800w or so - the ability to therefore cycle them is not huge - you may be better off looking at a 2nd tank and a pump and valve between them. Once the first tank is full and up to temperature you can draw off 100 litres to the next tank and then reheat the first tank etc
@craigcurtin a lot of questions, I try to go through.
Do you have a tempering valve on your heatpump output (one that mixes hot and cold water to get to a safe temperature ?)
I am not sure, I have a Ochsner GMSW 10 HK plus (OTE3) but I am not aware if it consists of such a tempering valve. It is a geothermal heat pump and high efficient, in Germany during winter we have sometimes -20c and even there is does not consume more than ~4-5kW.
What is the maximum power draw of your Heat pump compressor ?
In both cases, either for hotwater as well as for the heating system the maximum power draw is ~4 kW.
Do you have realtime visibility on your House Power consumption and Solar panel production?
Sure I have realtime visibilty on both, the House Power consumptions as well as the Solar panel production.
What size is the water tank for the heatpump ?
I have two buffers, one for the hotwater (200L) one for the heating system (500L).
We use a stadnard resisitive hot water element tank here in Australia where we can take the water to a maximum temperature of 70c.
Since I do not have a heating rod inside my water tank and the heating pump is heating the water tank the maximum temperature is ~60c.
I wanted to ensure that if we had a number of day of cold/overcast weather we still have optimal hot water - so we put a 2nd tank in front of the first.
Once the first tank (which is what feeds the house) is up to temperature, we then cascade over to the 2nd tank and start heating that.
THe output of the 2nd tank feeds the input of the first tank
This means that we have a maximum of 650L of hot water available at theoretically 70c - however it is only in summer that we have enough solar to fill our batteries and heat both water tanks - but during peiord of multiple cloudy days and low solar output we were able to ride through without having to revert to mains input to heat any water
Generally on a heatpump system the compressor are very efficient and will only draw about 800w or so - the ability to therefore cycle them is not huge - you may be better off looking at a 2nd tank and a pump and valve between them. Once the first tank is full and up to temperature you can draw off 100 litres to the next tank and then reheat the first tank etc
To be honest, I do not want to change my heating system at all. I only want to optimize the solar power generation usage.
