Solar thermal integrated into ASHP

[JohnMo]

I have an ASHP all installed and working.  Also have a solar thermal panel - not installed, with a full drain back system.

 

My issue I can't install direct to cylinder without quite a bit of work, but have very easy access to a roof space and ASHP flow and return pipes.

 

So was thinking of coupling direct into either the flow or return of the ASHP via close coupled tees. Then put some logic behind it. Think return pipe would be better?

 

So I need to do

Take solar thermal when cylinder heating and heating UFH, but not when cooling. Typical flow temp for UFH is around 30, so should get a decent yield from ST even in winter. I could even switch off in the summer.

 

What do you think, is it feasible?

[SteamyTea]

How about a heat exchanger?

[JohnMo]

The drain back unit has an inbuilt PHE.

 

Had another thought about indirectly increasing CoP through air pre heating. Basically flow ST water through car radiator say behind ASHP. Something like the attached. Even though only part covering the ASHP condenser air is being pulled through the radiator.

[JohnMo]

ST only needs to operate just above OAT with radiator, as long as get back more energy than the pumps being used it's a bonus. Looking at my CoP chart flowing at 30 degrees the difference between -2 and +2 is a drop of 300W. The pumps will pull around 30W each, there are two.

[Nickfromwales]

1) Sell the panel. 
2) Purchase beer. 
3) Enjoy solar thermal by sitting on a chair in the garden getting a tan.

4) see item 2. 

[SteamyTea]

I wondered if a MVHR system could be made with a couple of car radiators.

 

[JohnMo]

1 hour ago, Nickfromwales said:

1) Sell the panel. 
2) Purchase beer. 
3) Enjoy solar thermal by sitting on a chair in the garden getting a tan.

4) see item 2. 

I like playing, I can afford the beer

[Nickfromwales]

2 hours ago, JohnMo said:

I like playing, I can afford the beer

Can I have some money to go out tonight, please?

[JohnMo]

4 minutes ago, Nickfromwales said:

Can I have some money to go out tonight, please?

Sure, if you come round I'll buy you a pint or two. It's only about 10 to 12 hour drive.

[Nickfromwales]

Just now, JohnMo said:

It's only about 10 to 12 hour drive.

I am en route!

 

Never underestimate what a Swansea boy will do for free beer.

[JohnMo]

Great I see you soon

[JohnMo]

Started to get things together. Will be  using a CCT in the return pipe. Will use the solar controller, so it thinks the flow and return pipes are the top and bottom of a cylinder and set the temperature and hysterisis as required.

 

Have mounted the drain back unit (black box), the pipes at the top connect to the solar panel and there are pipes at the bottom that will connect to the CCT. CCT will be located in the pipe section highlighted in red.

 

 

Still need to figure out how to make the system to work during DHW heating and UFH heating, but be off in cooling mode - maybe some relay logic.🤔

 

 

[Iceverge]

What is it about solar thermal and solid fuel heated water. 

 

Completely outdated, expensive, require too much maintenance but none the less my inner schoolboy really likes the idea of playing with them. 

[SteamyTea]

15 minutes ago, Iceverge said:

Completely outdated, expensive, require too much maintenance but none the less my inner schoolboy really likes the idea of playing with them. 

Is it because it is mechanical?

Not like those pesky photon upsetting the quantum state of electrons.

[JohnMo]

1 hour ago, Iceverge said:

Completely outdated, expensive, require too much maintenance but none the less my inner schoolboy really likes the idea of playing with them. 

Good to play. Bought everything a 2 years or so ago, paid about £700 for 2mx1m panel, drain back unit, hoses, and controller. Will spend another £2-300 to plumb up and make a frame for the panel.

 

Plumbed the drain back unit into the heating circuit today. Just got to finish the pipe insulation 

[JohnMo]

Solar panel will become a roof above my ASHP to keep the worst of the weather off it.  The green dots are where the pipes will go through the wall to the drain back unit

 

Edited July 10, 2023 by JohnMo
Missed details

[SteamyTea]

4 minutes ago, JohnMo said:

Good to play.

What sort of monitoring you going to do on it?

[JohnMo]

1 minute ago, SteamyTea said:

What sort of monitoring you going to do on it?

Good question. No idea. Any suggestions? Needs to be simple.

 

I do know in quite good detail the gas usage to heat the house from the last two heating seasons.

[SteamyTea]

25 minutes ago, JohnMo said:

Good question. No idea. Any suggestions? Needs to be simple.

A flow and return temperature logging and a sensor that know when the system is pumping.  As long a you know the flow rate, you can work out the rest.

So two DS18B20s and a 240V relay that shuts when the pump is energised.  Then log the time the relay is closed.

[JohnMo]

So something like this? How do I log the data?

 

2 Pack DS18B20 Temperature Sensor Module Kit with Waterproof Stainless Steel Probe, TO-92 for Arduino and Raspberry Pi https://amzn.eu/d/dVa0n1F

[SteamyTea]

12 minutes ago, JohnMo said:

How do I log the data

One Raspberry Pi GPIO pin will sense the temperature and can write to a file. Another pin can sense, via the relay (in effect a no volt switch) when it is on.

When the pump is on, the GPIO that the relay shorts out and raise a flag against a time stamp. Then a bit of spreadsheet work to show the data.

I think I already have some code written for this. Shall have a look tomorrow. Not so different from my electrical data logger, which just used a light pulse as a switch.

[SteamyTea]

I think these are the .py files.

They will need a little modification for your sensors i.e. change the 28-xxxxxxxxxxxx to your DS18B20 number, and create directories to where you want to store data.

 

1 Wire

 

#!/usr/bin/python3

#imports necessary libaries
import os, time, datetime

#load drivers
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

while True:
#Sort out the time format
    dt = datetime.datetime.now()
    runday = dt.day
    dt.day == runday

#sensor 1
    tfile = open("/sys/bus/w1/devices/28-xxxxxxxxxxxx/w1_slave")
    text1 = tfile.read()
    tfile.close()
    temperature_data1 = text1.split()[-1]
    temperature1 = float(temperature_data1[2:])
    temperature1 = temperature1 / 1000

#opens and reads the time
    ts = time.time()

#sets time to UTC and dd/mm/yyyy hh:mm:ss format
    UTC = datetime.datetime.utcfromtimestamp(ts).strftime('%d/%m/%Y %H:%M:%S')

    logfile = '/home/pi/monitoring/data/1wire-%s-%s-%s.csv' % (dt.day, dt.month, dt.year)
#    logfile = '/var/www/html/data/1wire-%s-%s-%s.html' % (dt.day, dt.month, dt.year)

#creates and opens or appends data to file
    tfile = open(logfile, "a")

#writes to data file
    tfile.write("%s"%UTC + ",%s"%temperature1 + '\n')

#closes data file
    tfile.close

#sleeps for (n) seconds until next reading
    time.sleep(10)

 

 

Switch

 

#!/usr/bin/python

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
import time, datetime

GPIO.setup(7,GPIO.IN)

input = GPIO.input(7)

while True:
     if (GPIO.input(7)):

        ts = time.time()

        UTC = datetime.datetime.utcfromtimestamp(ts).strftime('%d/%m/%Y %H:%M:%S')
        
        tfile = open("/home/pi/monitoring/data/switch.csv","a")

#writes to data file
        tfile.write("%s"%UTC + ",%s"%input + '\n')

#closes data file
        tfile.close

#        print("Button Pressed")

        time.sleep(6)
 

[JohnMo]

Solar controller now installed. Still wires to tidy up. The control scheme has a PHE and two pumps, one each side of the PHE.

 

 

To monitor heat given out by the thermal system, I will reconfigure the heat meter I had previously installed in the heating system. Will install in the pipe from the PHE to close coupled tee. I have glycol in the system and the heat meter will over read by circa 2%, which I can live with.

 

[JohnMo]

Heat meter installed today, circulation pump run to get all air out of the system. Heat meter unit contains the flow meter and a hot water stream temperature probe, so is installed after the PHE. The cool water probe is installed downstream of the pump and upstream of the PHE.

 

Solar controller has the cylinder bottom probe in the heating return line upstream of the close coupled tee. The top of cylinder probe is installed approx 0.5m after the close coupled tee.

 

 

Need to get my head around the controller settings. Job for later.

 

Had a play with pump flow rates. UFH flow is approx 1m3/h. Solar thermal pump can delivery the same flow though the close couple tee. But will have a proper test when solar panel is coupled up.

 

Unistrut is being delivered tomorrow 3x 6m lengths of 41x41, £96 delivered. So a very good price. Will be moving to the framing next to hold the panel up.

 

 

[JohnMo]

Bit more progress today, support frame assembled, need to trim the ends off at top. Panel to mounted at 45 degs in landscape. All the frame materials cost £132, including panel mounts.

 

Just got to figure out how to get the panel in place.