Jump to content

Solar Water Heating Recommendations


Kloon

Recommended Posts

The only thing diffrent from this diagram is that they used a T on the heat pump return, its not connected to a banjo vale

 

image.png

Link to comment
Share on other sites

I agree with jdp that a heat pump is the obvious solution in his setup with plenty of PV power and assures hot water at all times. Certainly the heat pump is much more efficient than resistive heating particularly if you don't have plenty of PV power and use Eskom electricity. Since October 2015 I have used only 17 Kwh for the geyser, 16 EV tubes did most of the heating of the 200 liter tank but we are only 2 people in the house. My circulating pump sucks from the bottom of the geyser and dumps at the top and the stratification of the Xtream geyser seems very efficient. The Arduino homebrew controller measures the difference between the top op the tank and the collector and turns the pump on at 5C and off at 2C. It also measures the bottom of the tank and after some time of heating the difference between the top and bottom is little. Before installing the controller. the solar driven pump tended to mix the hot water at the top with cold at the bottom because the PV panel produced power well before the EV tubes collected sufficient heat. Now the top is always hot even if the bottom is sometimes almost 30C colder.

Link to comment
Share on other sites

Yesterday I checked my energy harvesting from my solar PV system and solar thermal system and found the following:

Cape Town (Southern Suburbs) - 11/05/2016

System

Solar PV

Solar Thermal

Energy Produced

7.8 Kwh

4.4 Kwh

Array / Collector Area

10m2

3m2

Approx. Costs to Install Today

R120 000

R20 000

Specs

1.8 Kwatt Array, Outback MX 60, 48 Volt Battery, MLT 6 Kwatt Inverter

 

Energy produced at the 48 V DC level. So inverter and battery losses not considered.

200L Solar Geyser, 3m2 Collector - Thermosyphon

 

System raised 200L of water from 36 – 55 C (∆T = 19C)

Q = (mCP∆T)

CP = Heat Capacity of water = 1.16 kWh/m3K

 

Link to comment
Share on other sites

On 2016/05/09 at 1:19 PM, jdp said:

The hot water is dumped at the bottom of the hot tank not at the top. The tank also has that device (not sure what the name is) to keep the water from mixing.

 

I didn't mean to imply that all heat pump systems have this mixing problem. I know ITS (and some others) have solved it. It is a problem with the cheaper heat pumps, and the original installer is usually nowhere to be found once it is discovered :-) Experienced installers know the problem and solve it by either using a closed loop, where the water cycles until it is warm enough to move on to the main tank, an intermediary tank where the water naturally siphons to the main tank when it gets hot enough, or by injecting the water somewhere towards the middle of the main tank so that the top half of the tank is always undisturbed and contains the hottest water.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...