Combined solar + heatpump central heating/cooling

[Acuario]

Anyone following my adventures will have seen the thread on our new build.
As a result the old boiler room where I had the heat pump/solar etc. was demolished and a new room built to house everything. This also meant a major re-plumbing/mounting/installing etc.... So mk2 was born with a few changes and to incorporate under floor heating/cooling..

Originally I had a home made heat exchanger with a 100L water tank to do the transfer between the heat pump and water system. A while back I experimented with a second unit connected to a small plate heat exchanger and was pretty happy with the results so when my home made hx developed a leak I decided it was time to move to a slightly larger plate hx.

This worked well over the winter and then in reverse mode was working well for cooling the water for the under floor cooling.

My only concern was that the hx was at one end of the boiler room and the heat pump at the other, resulting in some losses due to distance. So when a broken heat pump came my way I had the perfect solution - a huge plate hx with mount and flow sensor and as a bonus a filter dryer - ok, it was for R410A and I'm using R417A but with a bit of a clean all should work out well.



So I re-plumbed the piping to the heat pump, connected up to flow and return and all now works exceptionally well.



I've also installed a second heat pump connected to the original hx so I can give a boost on those few cold days we get in February.





I also re positioned the hot water panels I have for winter heating - they are connected to the 100L water tank in the picture. They are angled high to capture maximum sun in the winter - in the summer they aren't used and I empty them. The controller (not shown) is home made using a pic and has anti-freeze protection built into it just in case...



The picture of the collector set shows the temperature of the water going into the floor at 18 degrees, this just about coincides with the exit temperature from the hx.



The system is being run by an AIR-80 heat pump controller - this unfortunately only works for heating (so I have the 4-way valve set to cooling)but will do until I build my own controller. It works perfectly in the winter in heating mode as it has a hot gas defrost cycle as part of its program.



You can find these cheaply on AliExpress.



In the picture of the 'mess :-)' you can see the boiler which is connected as a back-up of last resort should a)The weather is too cold for the heat pumps or b)We have no grid power - we have 4Kw solar electric that will happily run the boiler and circulating pump. Also visible on the left is my latest project, the Fan-coil internal aircon unit which is just there for testing.

Acuario

[Acuario]

The winter is now over (I hope!) so how did it all work out?

I have readings for the years 2012, 2013 and 2015 (2014 was building work and I didn't have it set up for taking readings).

2012
- Using existing 7 aluminium radiators - no under-floor heating or solar assist, heat pump only.
- Area heated approx. 120M2

Hours of use: 3377
Kw used: 6592
Electric 0.1644/KWh
Total cost: 1084.21 euros
Average daily cost: 7.704 euros

2013
- Using existing 7 aluminium radiators - no under-floor heating or solar assist, heat pump only.
- Area heated approx. 120M2

Hours of use: 3653
Kw used: 6653
Electric 0.192/KWh
Total cost: 1273.73 euros
Average daily cost: 8.366 euros

2015
- Using 3 existing aluminium radiators
- 50M2 under-floor in lounge
- 10M2 under-floor in bathroom
- 130M2 under-floor in new build
- Area heated approx. 250M2
- 3 solar hot water panels to support heat pump
- Change of plate heat exchanger to larger model

Hours of use: 4116
Kw used: 5129
Electric 0.156/KWh
Total cost: 800.64 euros
Average daily cost: 4.67 euros

They are, I think, impressive results this year. They show conclusively that under-floor heating supported by solar hot water panels can save serious amounts of money.

Also, before I connected the heat pump in 2012 I was using around 1300 litres of oil to heat the house just part of the day. The readings above are for 24h/day heating and at approximately 21C.

[jeff5may]

Very impressive! That's a 60% increase in efficiency. How much would you say is heat pump efficiency versus raw solar thermal? Either way, you've got to love the lower electric bill.

[Acuario]

I think a lot comes from the solar as I was previously running the heat pump. For next winter I'm going to re-write the software for the solar controller to log hours it is active.

I think the biggest change is as a result of the under-floor heating as we have a huge thermal mass that gets charged up by the solar during the daytime. Even in mid winter on partly sunny days there was a big difference in power usage by the heat pump. The last week of January was very sunny and in 7 days our electric usage was only 166Kw. We're lucky to live near the Mediterranean where we don't suffer from very cold days and generally have lots of sunshine.

I must admit that I was very surprised at the low power usage, I had to re-check my readings more than once, especially as we had increased the heated space substantially.

Previously I didn't think that solar central heating was feasible but now, when supported by a heat pump, under floor heating and, essentially, good insulation, it certainly is.

[Mikesolar]

Looks good. You must be retired, haha. I can't find enough time to complete my projects.

That chinese heat pump controller looks good but it won't work for us in northern North America as we get outdoor temps well below -20C. None of those controllers seem to work below that.

[Daox]

Any additional updates Acuario?

[Acuario]

Nothing at the moment. Everything is shut down as the winter is well and truly over.

Towards the end of June it usually starts getting pretty hot here so I'll be switching to cooling mode along with my cheap non-air conditioning night-time cooling system.
http://ecorenovator.org/forum/other-...t-cooling.html

I am noticing a big temperature difference between the old and new build, the old being much hotter due to lack of roof insulation. The temperature in the roof space is very high compared with the rooms - I'll take some readings and let you know what the difference is - 7cm insulation certainly makes a difference!

You can see the new/old build quite well on Google Earth.

[Acuario]

Summer is over and, as usual, long and hot.

For the first time I had the under floor cooling running properly and so have some data, obviously no comparisons as I've not been running air conditioning previously so don't have comparisons to see if there is a saving.

The house was definitely very comfortable though, with temperatures varying between 24 and 26 degrees, outside temperatures in the mid to upper 30's and touching 40 a couple of times.

Initially I ran the unit 24/7 but had problems with dew forming.

To overcome problems with floor dew I ran the cooling on a 12h cycle, from 8am to 8pm and we had the ceiling fans running at a slow speed. This, apart from one or two days, prevented any dew forming. There wasn't too much impact on the house temperature.

The water temperature in the floor was typically around 17C

Electricity use averaged 23KWh per day, around 2.74 euros (our electric is 0.119 euros per KWh)

In total we used 2142KWh.

[randen]

Acuario

I ve been following your threads. It's nice to see a fellow ecorenovator enjoying the power of the sun. I was looking at your results of doubling your living space and reducing your power usage by almost half. Impressive.

Another ecorenovator is just starting to understand the power the sun wields. Geo-NR-gee is playing with some flat plate collectors and making steam. Soon he should be harnessing that heat and hopefully heating his living space. All for FREE.

Here in Canada the summer has been consistently warm. We have a ground source heat pump which is a water to air unit so the humidity is controlled and our cost to air-condition is very very low. Another big plus is we are essentially storing heat in the ground for the impending winter.

The solar hot water provides 100% of the domestic hot water. Now that October is here and night time temps are dropping into the negative numbers the solar hot water is heating the concrete floors keeping us very comfortable. As the weather becomes increasing nasty and the sun disappears for weeks at a time we resort to a water to water HP to heat the floors.

Our cost for operation of air-conditioning maybe a little less Kwh per day would be around 15 kwh. However the price per Kwh is 0.18 Euro. And we understand another sizeable increase is coming in Nov. We are conditioning 330 sq m.

Kudos to your efforts in harnessing the sun and phase change of gases.

Randen

[georgepacu]

acuario I am thinking that if you send cool water aroun 20 to 21 C in the underfloor loops then you will not have dew forming from what I have seen on threads for underfloor cooling