Thread: Passive House Cooling

Originally Posted by Felix Sphinx

PM if you wish advice

What's the point? No one can understand your retarded ramblings.

The trick with passive cooling of a home would be to have as much natural draft flowing through the home as possible, to begin with. Good thermal insulation & heat-barriers would be essential. These cost in terms of initial capital outlay, but are free thereafter (except for maintenance).

Once you've exhausted all the 'natural tricks', then it's time to begin modifying the environment artificially - these costs are ongoing. The trick here is to keep them as small as possible by using cunning designs.

Originally Posted by watterinja

The problem with wanting to cool is that the cooling in a conventional aircon system is on the evaporator end (inside). The condenser (outside) end essentially passes the (room heat)+(compressor heat)=(condenser heat) into the surrounding air. In other words, moving low-grade thermal energy - room air - to high-grade thermal energy & dumps it. Now, in this scenario, you would need to dump the condenser heat into the geo-thermal system at rather a large temperature - probably at entry, at anything around 60-100'C (depending on compressor load), dropping off to a saturation temp of anything between say 40-65'C.

That doesn't seem to be how it's usually done. I'm nick this from Wiki, as it's explained better than I can do it.

Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat. Heat pumps can capture heat from a cool area and transfer it to a warm area, against the natural direction of flow, or they can enhance the natural flow of heat from a warm area to a cool one. The core of the heat pump is a loop of refrigerant pumped through a vapor-compression refrigeration cycle that moves heat. Heat pumps are always more efficient than pure electric heating, even when extracting heat from air.
But unlike an air-source heat pump, which extracts or exhausts heat to or from the outside air, a ground-source heat pump exchanges heat with the ground. This is much more efficient because underground temperatures are relatively stable through the year. Seasonal variations drop off with depth and disappear below 10 m due to thermal inertia.[2] Like a cave, the shallow ground temperature is warmer than the air above during the winter and cooler than the air in the summer. A ground-source heat pump extracts that ground heat in the winter (heating) and exhausts heat back into the ground in the summer (cooling).

Geothermal heat pump - Wikipedia, the free encyclopedia

It's basically a load of plastic piping, a manifold and a vapour compression fridge.

^ It's a fair bit more than that...

Try using plastic piping on a hvac system.

Water is a much better condensing medium than air so you could have a cool water supply to use for your condenser cooling you could gain quite a bit over 100*F air for the job.
I used a sea water heat exchanger for my condenser on my last cruising boat when I built my holding plate reefer system and had a deep freeze and a fridge box on one compressor and could maintain -20 in the freezer box with 1/2 hour per day engine time, and that charged all batterys with a 150 amp alternator as well as made 3 gallons of fresh water and well.

BG... that was in moving water. No problem there - an infinite heat-sink.

For pumping heat down into a ground-loop, for an hvac condenser, is going to have to dissipate the heat into either local ground-water, or the soil. Has any work been done on this in Thailand? Would be interesting.

The cost of the ground-loop would also be a bit, I'd imagine.

All perfectly doable, but not yet sure on how to determine the condenser design closely, under Thai conditions. (A ground-loop evaporator, in Europe is a given). Would probably need some info from ground drillings, or house foundations. How deep would this coil need to go - for instance?

If you had a large tank or pool, that could be pumped round to act as a cooling agent

as long as you don't mind swimming in warm water

I think the key to a cooling system that has been suggested is the relative humidity. Will work well in a climate with a low humidity, but as one climbs up the humidity ladder, this type of cooling system doesn't work as well.

Personally, I have not tried this in Thailand but it might work. I do know that in the summer; midwest regions of the states found this idea not the best.

Originally Posted by watterinja

BG... that was in moving water. No problem there - an infinite heat-sink. For pumping heat down into a ground-loop, for an hvac condenser, is going to have to dissipate the heat into either local ground-water, or the soil. Has any work been done on this in Thailand? Would be interesting

I understand that, but some units that are put on boats use the conventional fan cooled radiator type condensers.
and I do not think that ground loop will go as well here as it does in a more temperate climate where you have at least night time cooling as there is not much below mid seventys here and mostly clay soils and in our area there is no real water as I drilled a well to 59 meters and came up dry.
I really do not think you would get below 65*F here and that would take a fair size ground loop unless you also incorporated a conv. fan cooled condensor too.
We went down 1.5 meters with our foundation pillars when we built and it was very warm at that depth.

But swamp coolers did work quite well when I worked at Nevada Test Site and with ours running if you got in front of it you damn sure developed goose bumps in a hurry, and Air con there was not good as it was to dry and you would develope a cough.

^^ MM - fair-enough, they're running a secondary loop in plastic.

Instead of dumping the condenser heat into the ground, why don't you simply heat water for your home? This is precisely what the AWHP is designed to do.

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^BG - good points.

But swamp coolers did work quite well when I worked at Nevada Test Site and with ours running if you got in front of it you damn sure developed goose bumps in a hurry, and Air con there was not good as it was to dry and you would develope a cough.

Interesting comment about the humidity being too low - developing a dry cough.

Originally Posted by watterinja

Interesting comment about the humidity being too low - developing a dry cough.

That happens quite often in my home state as it is dry and when it gets below freezing then there is no moisture in the air at all and either you have a water kettle on the heater stove if wood or gas or use commercial humidifiers that use expensive distilled water or do not last to long with heavy mineral water.
My gram used to have a few playing marbles in the pot and they would collect the lime and solids and get as big as golf balls and she would throw them out and put in some more of my marbles.

Originally Posted by watterinja

^^ MM - fair-enough, they're running a secondary loop in plastic. Instead of dumping the condenser heat into the ground, why don't you simply heat water for your home? This is precisely what the AWHP is designed to do.

Well, you're the designer. Get on and design it. :P

It's already designed... How many kW do you require?

Originally Posted by watterinja

It's already designed... How many kW do you require?

About 60.

60kW... What hotel is that for (120+ rooms)?

Originally Posted by watterinja

60kW... What hotel is that for (120+ rooms)?

A ton of heat is 12,000 British thermal units per hour (BTU/h) or 3.5 kilowatts.

OK, well I suppose 120,000 BTUs would do for a house, so 30 to 35k would suffice.

What were you thinking of?

well I need another ton if thats how you figure it, for the living room as I run this one in the bedroom 24/7 now, so be another 3.5 KW

Originally Posted by blackgang

I run this one in the bedroom 24/7 now

Must be where your computer is located! Mine too.

Originally Posted by Marmite the Dog

OK, well I suppose 120,000 BTUs would do for a house, so 30 to 35k would suffice.

What were you thinking of?

So, you've got a house, with 35kW of cooling off the evaporator coil.

Next calculations:
1. Determine the electrical power required (to drive compressor, fans x2);
2. Determine kWh energy usage in one day, month;
3. Determine monthly electricity bill.

Can I be your Bank Manager?

Originally Posted by watterinja

Originally Posted by Marmite the Dog

OK, well I suppose 120,000 BTUs would do for a house, so 30 to 35k would suffice.

What were you thinking of?

So, you've got a house, with 35kW of cooling off the evaporator coil.

Next calculations:
1. Determine the electrical power required (to drive compressor, fans x2);
2. Determine kWh energy usage in one day, month;
3. Determine monthly electricity bill.

Can I be your Bank Manager?

Are you going to do the calculations or am I?

Originally Posted by Norton

Must be where your computer is located! Mine too.

Yea, I put one in the bedroom, but I can get no one to come and put in my attic fan as some work needs to be done to do it, so I am going to put another 12000 BTU in the living room.

Originally Posted by watterinja

Determine monthly electricity bill.

A couple of years ago I did start the hot season running 37000 BTU of aircons for the first month, and what had been 4500 to 5000 a month before was now 7500 a month so I quit that shit and ran only a 12 in the bedroom at night and only about 4 hours a day on the big one in the kitchen/dining room.

A friend of mine has a couple of fans built into holes in his bedroom walls which he leaves running all day and says that they negate the need to run the AC.

I was thinking of trying something similar, but finding the right fan might be a problem, as I wanted to try mounting one on my security bars, so it would have to be thin like a car fan. If I bought a car fan, would it be easy to find a 12v transformer. I assume it would as they are used for low voltage lighting aren't they?

The title of this thread is 'Passive House Cooling'.

Fans, a/c, are 'active coolers'. You will need to broaden your views MM.

(Btw, thanks for removing my previous post. Don't forget the COP, if you're going to compute your a/c electricity bill)

I have just read some of the postings here.
WOW,,,, I do not want a heated discussion here but this is what i think.

I worked on many geothermal systems in the past... But the ones i worked on all had problems... (The Same Problem) Not enough holes in the ground. Simply could not transfer enough heat into the ground or what ever they were using to transfer. (Swimming pool, Lake, what ever.) Cost cutting on holes in the ground or poor engineering to begin with. Who knowes.... EXPENSIVE

Every one knowes it is cheaper to heat water or air or whatever with a heat pump. With high effiency compressors and increased condenser area,,, very good. I see now two speed and even variable speed compressors now. For up to 20 SEER and up. COP of 9 and up.... WOW

The bottom line is cost ,,, cost ,,,, COST of installing and maintaining.

In my opinion. Large to medium size buildings of new construction is a good choice for high tech engineering for cost savings. ( DDC control, geothermal or water source pumps... on and on.....)

In Tropical locations. I personally see no need for high tech high cost equipment for residential applications.

I think insulation, insulation, insulation on existing houses, Then run a quick load and install a medium effiency air cond. in your home. Cost wise you will be way ahead...
Hot water.... Your in the tropics.. sun abounds... USE IT.... If possible.... If not go with a heater on the wall.

KISS , Keep it simple stuid. My motto now in life...

Go, GREEN