Combined solar plus heatpump central heating
 

..my latest project..

Last year I built a heat pump system and connected it to my central heating system. The results were spectacular to say the least. I saved in the order of 1500 euros on heating oil for an investment of about 100 or so euros.

See http://ecorenovator.org/forum/geothe...ks-mods-3.html

Well, having acquired a couple of 100L vertical mounted water tanks during the year (one top fed, one bottom fed, couldn't have wished for a better combination!) and a couple of solar hot water panels with blown pipework (an easy enough fix just a bit of brazing) the logical thing to do was to see if I could add solar heating to the system as well.

So I have put a system together, one tank (the left one in the photo) connected to the solar panels, the other tank connected to the dual compressor heat pumps (there are actually 3 but...) - see http://ecorenovator.org/forum/geothe...at-pump-2.html

I've just got to mod the controller now so it runs the solar as well as the heat pumps and commission the system. Just in time for winter although it seems to be later coming this year.

http://ecorenovator.org/forum/attach...1&d=1387301512

http://ecorenovator.org/forum/attach...1&d=1387301480

http://ecorenovator.org/forum/attach...1&d=1387301480

The solar controller is now built and up and running. It is fully programable via the main controller I built that controls the heatpumps.

It has settings for upper and lower panel temperature differences and I also built in a frost prevention temperature setting so the pump will run to keep the panel from freezing should the panel temperature drop below a certain point (it rarely happens here but better safe than sorry).

As I used a solid state relay to run the pump I wrote an algorythm so when the difference is less than 10 degrees the pump only runs part of the time in relation to the difference.

i.e.
if the difference is 9 degrees the pump runs 9 out of every 10 seconds
if the difference is 4 degrees the pump runs 4 out of every 10 seconds

The idea being that the water in the panel will have extra time to absorb heat as it is moving slower through the panel.

I'm getting between 10 and 12 degrees temperature drop across the input and output of the heat exchanger so it's doing it's job well.

I also run the recirculating pump to disturb the water through the 2 tanks so this is helping as it provides a continual disturbance of the water.

The picture shows the schematic of the system. The photo shows the 2 panels on the roof (the 2 at the end after the solar panels).

I intentionally put the solar heating after the heatpump as theoretically the solar can generate more heat than the heatpumps which are limited to around 55 degrees.

http://ecorenovator.org/forum/attach...-schematic-jpg

http://ecorenovator.org/forum/attach...ing-panels-jpg

A quick update:
The system has now been up and running a couple of months and is working brilliantly. I had to add a non-return valves into the down pipe (hot leg) from the solar panels as I was suffering with reverse circulation at night, i.e. the hot water was circulating back up to the cold panels by itself. A non-return valve soon sorted the problem out.

Obviously there isn't heating from solar every day but it is helping when there is.

Acuario

Looks like a great setup. Thanks for sharing!