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Old 07-28-14, 09:29 PM   #451
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Originally Posted by NiHaoMike View Post
You could build a water source heat pump to supply some of the heat, with the generator supplying the rest. Should be far more efficient than idling the "APU" purely for heat. Also, when connected to mains (maybe not often enough for it to really matter), the APU wouldn't have to run at all.
Ok, I've done a couple of hours of googling & reading about water source heat pumps. An Open Loop Water Sourced Heat Pump is of great interest now.

Alas these seem to be aimed at moderate sized houses or larger. The smallest I did find was a Dimplex SIH 4 ME (4KW) but it is listing at 3.5K/$6K. Several times more than a 5KW Diesel Water Heater designed for a Marine environment. The power use of the heat pump will need looking into carefully.

Also I have a feeling from my initial reading it would take 1KW.hr as an input (EG in a 4KW Heat Pump that needs 1KW electrickery), whereas a 5KW Diesel Water Heater would need 35-50 W.hr as an input (for the circulation pump & control unit aspects... IE nearly nothing). Power is a big concern as previously mentioned.

Still, DIY to the rescue? Do you have any more specific advice/pointers in this regard?

Cheers!


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Old 07-28-14, 09:39 PM   #452
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Still, DIY to the rescue? Do you have any more specific advice/pointers in this regard?
You might try the Homemade Heat Pump Manifesto

You should find a good bit of information there.

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Old 07-29-14, 01:09 AM   #453
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Originally Posted by Jim_UK View Post
Ok, I've done a couple of hours of googling & reading about water source heat pumps. An Open Loop Water Sourced Heat Pump is of great interest now.

Alas these seem to be aimed at moderate sized houses or larger. The smallest I did find was a Dimplex SIH 4 ME (4KW) but it is listing at 3.5K/$6K. Several times more than a 5KW Diesel Water Heater designed for a Marine environment. The power use of the heat pump will need looking into carefully.

Also I have a feeling from my initial reading it would take 1KW.hr as an input (EG in a 4KW Heat Pump that needs 1KW electrickery), whereas a 5KW Diesel Water Heater would need 35-50 W.hr as an input (for the circulation pump & control unit aspects... IE nearly nothing). Power is a big concern as previously mentioned.

Still, DIY to the rescue? Do you have any more specific advice/pointers in this regard?

Cheers!
Rather than run the APU at a fast idle just to get it making some heat, actually use it as a generator and make use of the power to run a heat pump, while still making use of the heat from the engine. In your situation, it wouldn't be too difficult to net more heat into the space than what was in the fuel to begin with.
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Old 07-29-14, 09:14 AM   #454
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Rather than run the APU at a fast idle just to get it making some heat, actually use it as a generator and make use of the power to run a heat pump, while still making use of the heat from the engine. In your situation, it wouldn't be too difficult to net more heat into the space than what was in the fuel to begin with.
There isn't an [propulsion] Engine(s) as you are assuming (normally, you'd be quite right).

Currently planned: There will be two 14KW PM DC motors for propulsion. 1KW Solar, 40KW Batteries & 5-8KW Diesel Generator (+ occasional 3.5KW Shoreline). It's an 'all' electric boat (well Diesel/Electric Serial Hybrid technically speaking due to generator - and the 5KW Diesel water heater previously mentioned).
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Old 07-29-14, 11:12 AM   #455
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There isn't an [propulsion] Engine(s) as you are assuming (normally, you'd be quite right).

Currently planned: There will be two 14KW PM DC motors for propulsion. 1KW Solar, 40KW Batteries & 5-8KW Diesel Generator (+ occasional 3.5KW Shoreline). It's an 'all' electric boat (well Diesel/Electric Serial Hybrid technically speaking due to generator - and the 5KW Diesel water heater previously mentioned).
Nice! How civilized!!

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Old 07-29-14, 07:57 PM   #456
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Then it would be a range extender rather than an APU, but same idea.

Assuming the generator is 30% efficient (diesels generally do better) and the thermal recovery system can recover 80% of the waste heat, the heat pump only needs to get a COP of 1.47 (EER of 5) to beat an ideal furnace. For comparison, a cheap window A/C easily does 9.7 EER or more.
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Old 09-22-14, 01:39 PM   #457
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Hello everyone,

I'm a relatively new ecorenovator. Concerning this site it is. I've been working on my house for a number of years now and probably considered a bit of a geek by many people, but it's nice to see I'm not the only one!!
I've read the whole thread from AC-Hacker about building a heat pump, a little in the conservation section and this thread. It took me a few days...
I have a house that's CO2-neutral (including the electric car BMW i3). The house was built in 1987 including a balanced ventilation system with heat recovery (1 cross flow hx). So it should be OK. But the efficiency I measured was approx 65%. This is only based on measured temperatures. So not including moisture effects. So in reality it could be a bit off the real value.
I thought about improving (or replacing) my system to achieve a better efficiency. However I'm also concerned about the AC-fans I have. To my opinion DC fans must be much more efficient, especially because in normal conditions (medium flow) my AC-fans run with a high "slip" (percentage of difference between the rotational speed of the fan and of the rotational speed of the electrical/magnetical field). This is achieved by a series capacitor.

But thinking about my centrifugal fans, I wondered about the fact that in this thread I almost all the times am reading about small axial fans. In my opinion generally the combination of hx, filters, ducting etc. requires a dp that most axial fans don't produce.

Of course I've seen the efficiency calculations (based on temperatures) in this thread and they sometimes looked impressive!
But I wonder if someone really did flow measurements. I fear that in many installations the efficiency might be OK, but the flow is just far below what's required. Normally in Europe we calculate these installations with 30m3/hr per person and some minimum values for toilet and bathroom.

Just curious about the measured flows. Anyone?

If you want to see details about our house and how we achieved CO2-neutrality, take a look at our site. It's in Dutch, but Google translate can help (although sometimes the translations are funny/odd).
The title means: No more energy bill. Here it is: geen energierekening meer: energieneutraal woonhuis fam. Kriegsman Ootmarsum - Rekening energiebedrijf 2013
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Old 09-22-14, 04:35 PM   #458
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...I have a house that's CO2-neutral (including the electric car BMW i3)...
Congratulations on CO2 neutrality!!!

You have achieved a goal that most of us haven't even allowed ourselves to dream of... and you have done it, very nice.

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If your house was built in 1987, and had a cross-flow HRV, you really are ahead of the game.
But as you surely know, a lot of improvement has happened since then, with ECM fans and improved HX cores, etc. I would check into what kind of HRVs are being used for Passive Houses. They seem to be at the cutting edge of this kind of thing.

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Just curious about the measured flows. Anyone?
Good point!

I did some experimental work that was posted on the DIY HRV thread, and Mike, the guy I was working with, happened to have a precision air volumetric measuring meter. They're really expensive and he was pretty lucky to have found one used, in good condition, and cheap.

In the DIY HRV thread also, there is a procedure described that uses very large plastic bags, and their volume is estimated and the time-to-fill is measured. I know it sounds very crude, but it should give you a good approximation of air volume rate.

-AC
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Old 09-23-14, 02:46 AM   #459
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In the DIY HRV thread also, there is a procedure described that uses very large plastic bags, and their volume is estimated and the time-to-fill is measured. I know it sounds very crude, but it should give you a good approximation of air volume rate.

-AC
If you want to do a proper measurement (including the duct losses), you should install plastic bags on all supply nozzles (in my case there are 5) and have someone with a stopwatch at each bag....
Otherwise you could only measure the hx + filters.
On the other hand... that's better than no measurements at all.

I had the opportunity to borrow a flow-measuring device that's intended to measure airflows from ventilationsystems (TSI Velocicheck including air capture hood).
In this way I was able to measure each separate supply nozzle and extraction nozzle and after that, I could adjust the nozzles so that incoming and outgoing air were really balanced.
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Old 09-23-14, 10:43 AM   #460
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...I had the opportunity to borrow a flow-measuring device that's intended to measure airflows from ventilationsystems (TSI Velocicheck including air capture hood).
In this way I was able to measure each separate supply nozzle and extraction nozzle and after that, I could adjust the nozzles so that incoming and outgoing air were really balanced.
Yeah, when I was working with Mike, he had a similar instrument, and we were measuring airflow from a duct opening. He measured at the edges and the center and various other places in between, and it was clear that the velocities were quite different across the opening. To get real volumetric accuracy, some averaging was needed.

The bag method takes care of those differences.

But if you only want to balance velocities, I suppose a center measure would do it.

-AC

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