Electrify Everything

[vbaker]

I live in a high desert climate at 6300 feet. Even now in July the early morning temperatures drop outside to ~ 65F. I thought I would be able to drop my home's temp to close to AM ambient with powered ventilation but I never succeeded. The home air temp would nadir to ~ 72 - 75F and then quickly rise through the rest of the morning, suggesting that the home mass unrelated to radiation had not cooled down to the interior air temperature.

Nowadays I dream of passive ventilation through the night and then use of a heat pump that I run from ~ 6am - 8am off PV. Imagine the COP !!

I have done a lot of experimentation with passive energy transfer, rule of thumb: the most efficient transfer happens with ~15F temperature differential. That last 15F takes a lot longer to achieve.

 

[SageBrush]

I have done a lot of experimentation with passive energy transfer, rule of thumb: the most efficient transfer happens with ~15F temperature differential. That last 15F takes a lot longer to achieve.

That makes sense, although my home ventilation is only 'passive' in the sense that I do not supply power. In June we have early evening wind that can continue until 10pm. There is also some early AM wind when the ambient is lowest. Unfortunately July is no where near as windy and is hotter.

Those are the reasons I think about 6am - 8am heat pumping. Poor wind anyway, low ambient temps, and enough sun to do the work

 

[vbaker]

That makes sense, although my home ventilation is only 'passive' in the sense that I do not supply power. In June we have early evening wind that can continue until 10pm. There is also some early AM wind when the ambient is lowest. Unfortunately July is no where near as windy and is hotter.

Those are the reasons I think about 6am - 8am heat pumping. Poor wind anyway, low ambient temps, and enough sun to do the work

And you have to think about the humidity (at least in the mid west). Sometimes getting the house cooled to 68F is not worth the extra humidity once it is closed up. Definitely look at those wall-hung heat pumps, most of them are pretty much DIY - if you have existing air returns you can use to get the tubing through the walls.

 

[SageBrush]

And you have to think about the humidity (at least in the mid west). Sometimes getting the house cooled to 68F is not worth the extra humidity once it is closed up. Definitely look at those wall-hung heat pumps, most of them are pretty much DIY - if you have existing air returns you can use to get the tubing through the walls.

Yeah ... I know what you mean wrt to humidity. I live in a high desert region and it is still a consideration.

 

[ThomasD]

High humidity sucks My electricity bill goes up by 35 to 40 dollars a month in the summer. If I could remove the humidity in the air and have my A/C at 79 I would do it I just don't know how Right know it's 87 degrees with 70% humidity and the sun is out and no rain

 

[vbaker]

High humidity sucks My electricity bill goes up by 35 to 40 dollars a month in the summer. If I could remove the humidity in the air and have my A/C at 79 I would do it I just don't know how Right know it's 87 degrees with 70% humidity and the sun is out and no rain

As I have been posting, those wall hung units! They are made to run almost continuously, advantage being de-humidification. Central air units do not run long enough to be effective at de-humidification.

 

[nwdiver]

As I have been posting, those wall hung units! They are made to run almost continuously, advantage being de-humidification. Central air units do not run long enough to be effective at de-humidification.

Yep; Working at URENCO gave me a greater appreciation for how dehumidification works. At URENCO we made a cold spot and it pulled the UF6 towards it. It was mostly passive. You can do the same with a mini-split on the wall. In the dehumidification mode the fan barely runs. If you have a ~40F area the water vapor is pulled into it. So you can reduce the moisture content of the room without expending energy significantly lowering the temperature (which also draws in more moisture through the same effect)

I think this is actually one of the 'creepier' or 'weirder' physical effects. If you have a high pressure container with 0% humidity and a low pressure container with high humidity the humidity in the low pressure container will actually migrate to the higher pressure until the partial pressures of water vapor equalize even before the absolute pressure does. The water vapor will actually go from low pressure to high pressure in terms of absolute pressure. Weird.

 

[vbaker]

Yep; Working at URENCO gave me a greater appreciation for how dehumidification works. At URENCO we made a cold spot and it pulled the UF6 towards it. It was mostly passive. You can do the same with a mini-split on the wall. In the dehumidification mode the fan barely runs. If you have a ~40F area the water vapor is pulled into it. So you can reduce the moisture content of the room without expending energy significantly lowering the temperature (which also draws in more moisture through the same effect)

I think this is actually one of the 'creepier' or 'weirder' physical effects. If you have a high pressure container with 0% humidity and a low pressure container with high humidity the humidity in the low pressure container will actually migrate to the higher pressure until the partial pressures of water vapor equalize even before the absolute pressure does. The water vapor will actually go from low pressure to high pressure in terms of absolute pressure. Weird.

Yeah, we usually have a hard time thinking of vapor pressure and air pressure being different critters, the odd part is the denser vapor moving faster. Or was it through a restricted orifice where the vapor could act as a blockage for the air?

 

[SageBrush]

I think this is actually one of the 'creepier' or 'weirder' physical effects. If you have a high pressure container with 0% humidity and a low pressure container with high humidity the humidity in the low pressure container will actually migrate to the higher pressure until the partial pressures of water vapor equalize even before the absolute pressure does.

I don't think I'm following.

It sounds like the water vapor near the coil is in a temperature below its dew point so it condenses to liquid. That is the dehumidification part I think; but I am wrong in thinking that the phase change releases heat ? It sounds like a reverse swamp cooler effect.

 

[nwdiver]

I don't think I'm following.

It sounds like the water vapor near the coil is in a temperature below its dew point so it condenses to liquid. That is the dehumidification part I think; but I am wrong in thinking that the phase change releases heat ? It sounds like a reverse swamp cooler effect.

Not referring to the phase change but how different types of gas molecules equalize in a space.

That's why something specifically working as a dehumidifier is more efficient than something working to cool the air. A dehumidifier minimizes air flow while maximizing condensation so most of the energy is used to condense water instead of cooling air.

 

[SageBrush]

Not referring to the phase change but how different types of gas molecules equalize in a space.

That's why something specifically working as a dehumidifier is more efficient than something working to cool the air. A dehumidifier minimizes air flow while maximizing condensation so most of the energy is used to condense water instead of cooling air.

Yes ...
I agree that a pressure sink develops in the coil area for water vapor as it phase changes and the subsequent movement of more water vapor towards the coil is energy investment free. Am I wrong in thinking that savings would otherwise cost the running of a fan ?

 

[nwdiver]

Am I wrong in thinking that savings would otherwise cost the running of a fan ?

Mostly yes; You want to minimize air movement. If you condense the water vapor without moving air you can move water molecules without moving air molecules... that's what I think is the 'creepy' part. How do the water molecules 'know'? They're not moving with the air. They're moving independently because there's a 'void' of water molecules in the condenser.

 

[vbaker]

Mostly yes; You want to minimize air movement. If you condense the water vapor without moving air you can move water molecules without moving air molecules... that's what I think is the 'creepy' part. How do the water molecules 'know'? They're not moving with the air. They're moving independently because there's a 'void' of water molecules in the condenser.

I got you now.

The condensation of water is more ~without~ airflow because airflow enables evaporation. It would evaporate a lot of the condensed water, even on the cold surface. This is how our modern frost-free freezers work, they have airflow in the freezer to evaporate the frozen and condensed liquid.

Until the air is foggy, it still has a lot of capacity to reclaim water. So units that do low-velocity, high-volume air exchange evaporate less of the condensed water, allowing more to be drained away outside the house.

 

[SageBrush]

The condensation of water is more ~without~ airflow because airflow enables evaporation. It would evaporate a lot of the condensed water, even on the cold surface.

Correct me if I am wrong -- I thought that the air temperature around the coils are below the dew point in just about any cooling application

 

[nwdiver]

I got you now.

The condensation of water is more ~without~ airflow because airflow enables evaporation. It would evaporate a lot of the condensed water, even on the cold surface. This is how our modern frost-free freezers work, they have airflow in the freezer to evaporate the frozen and condensed liquid.

Until the air is foggy, it still has a lot of capacity to reclaim water. So units that do low-velocity, high-volume air exchange evaporate less of the condensed water, allowing more to be drained away outside the house.

No; The problem is you're cooling the air in the room. So you're expending energy to cool air instead of condensing water. If you want to cool the room that's great... not so much if your objective is to lower the humidity. A 100% 'efficient' dehumidifier would remove the water vapor without lowering the room temperature.

 

[vbaker]

Correct me if I am wrong -- I thought that the air temperature around the coils are below the dew point in just about any cooling application

Correct, but the air almost always has capacity to absorb moisture. So expose enough air to the condensed water, and it will re-absorb it (except in the case of air saturated to the point of fog). ~edit: re-absorb the warmer-than-pipe-temperature water drops - air still makes deposits of humidity on bare pipe or moist pipe. The drops that form are mostly what I am talking about. Set two glasses of ice water on a table and blow a fan on only one of them. You should be able to see a difference in collected condensation between the two.

Cooling the room requires high airflow over the coils to move cooled air into the room, which evaporates a portion of the condensed water. A slow airflow will deposit most of it's water on the coils and allow it to drain. Or, like with some de-humidifiers, the air is heated before being blown across the cold coil, ensuring that even the water already on the pipe draws moisture from the moving air.

 

[ItsNotAboutTheMoney]

More on NY-state ground-source heat pump company and Alphabet X spinout Dandelion Energy. They've been featured on various sites and YouTube channels, and this time it was the well-known Tesla fanbois Now You Know interviewing the president/co-founder:

 

[SageBrush]

More on NY-state ground-source heat pump company and Alphabet X spinout Dandelion Energy.

Nice interview but they did not talk about net COP. I'm always leery of the electric consumption to run the system above and beyond the compressor.

My WAG is that if the alternative is $2,000 a year heating bill from oil/propane and the land is soft soil then it is worth looking into

 

[vbaker]

Nice interview but they did not talk about net COP. I'm always leery of the electric consumption to run the system above and beyond the compressor.

My WAG is that if the alternative is $2,000 a year heating bill from oil/propane and the land is soft soil then it is worth looking into

I just picked up a 1974 Case 580B backhoe. All soil is soft...

 

[RubberToe]

I just picked up a 1974 Case 580B backhoe. All soil is soft...

Yo @vbaker , if you really wrecked a couple Tesla's per your signature, should you really be behind the wheel of a Case 580B?

RT