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Old 02-02-21, 06:40 PM   #7
IamIan
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Quote:
Originally Posted by jeff5may View Post
burning liquified petroleum gas
Doesn't matter , because LPG is not part of this system.

Quote:
Originally Posted by jeff5may View Post
Megajoules per kilogram is the metric
Feel free to use any units you personally prefer .. calories , kwh , joules , BTUs , ERGs , etc .. etc .. any of them can easily be converted to any other.

I don't exclusively use wh .. but it is the main unit of energy I use most often.

Quote:
Originally Posted by jeff5may View Post
Liion batteries come in around 0.8 on the same scale.
0.8 Mj is about ~222wh
LiFePO4 and Toshiba SCiB LTO I have are closer to around ~120wh/kg.

Quote:
Originally Posted by jeff5may View Post
you cannot break even.
Better than break even is regularly achieved with any modern heat pump operating over a COP of 1.

A heat pump operating at a COP of 3 provides 3 energy units of heat/cooling for every 1 energy unit of electricity input you give it .. what ever unit of energy you like .. wh , joule , ERG , calorie , etc.

Quote:
Originally Posted by jeff5may View Post
The going rate is 25 equivalent watts per square meter. This is with 10% pv panels.
No.

Standard 1 Sun condition is 1000 input light watts per square meter .. a 10% conversion efficient PV panel would output 100watts per square meter .. not the 25w you claimed.

The ~10% you sited has not been the 'going rate' for PV for about ~20 years now .. Maybe back in the days of Windows Me O.S. , but a few things have changed/improved in technology in the last ~20 years .. ~18% is the 'going rate' today .. low end systems are ~15% .. average systems ~18% .. high end systems up ~22% .. and top of the line systems up near ~39%.

The PV panels I got operate at 20.5% conversion efficiency .. soo, anybody using 20~30 year old ~10% PV doesn't matter to me .. in the 1 square meter area of your example under standard 1 sun conditions these ~20.5% conversion efficiency panels would result in ~205watts.

Quote:
Originally Posted by jeff5may View Post
In effect, you're replacing a continuous duty burner of a certain size with a PV energy concentrating storage system capable of less service at higher expense. YOLO, it's just money...
Correction
To spend less money .. to get a more capable system .. that pollutes less .. and enjoy many entertaining hours of a tinkering project along the way.

Quote:
Originally Posted by jeff5may View Post
The best way to use your dehumidifier scale phase change contraption is to integrate it into your window HRV.
Correction.
The pump I am using is a larger scale heat pump than a household dehumidifier is.

Quote:
Originally Posted by jeff5may View Post
Put each heat exchanger at the downwind end and reflect the heat outdoors or indoors, depending on the season. 300 CFM per ton of refrigeration, or 10 watts per CFM of heat transfer, is the standard target indoors. This setup beats the above solar concentrating system described above by a factor of COP times ten. All day and all night
No.

Although what you propose would work .. it would not be COP times ten .. aka a COP of 30 .. no , that is impossible from the arrangement you suggest.

Oh that's right .. we also have 'ton' as a unit of energy .. aka "freezing or melting of 1 short ton of pure ice at 0 C in 24 hours" because humans just love using lots of different energy unit terms.

Your proposed system will be worse under some conditions.

Lower COP
Heat pumps get lower COP / efficiency the larger the difference in temperature between the hot side and cold side .. doing as you suggest would result in the system trying and get the most wh of heat to living space when it is the coldest outside temperature .. thus your design would result in a lower net average COP of the heat pump.

300CFM is allot of air flow .. for a ~800sqft with ~10ft tall rooms .. that's an entire house air change 55x every 24hr day .. Far to fast , and too often for me .. a little fresh air is one thing , but I think that is going a bit overboard.

In my design the winter night time heat pump doesn't have to work as hard as your design would .. my thermal storage will not be 10F temperature to try and pull heat out of .. thus I will get a higher/better average COP.

Quote:
Originally Posted by jeff5may View Post
All day and all night, without batteries. Off grid? No problem. Just run it off the power inverter.
Inverters need a energy source .. at night , something like batteries .. in order to function.

Quote:
Originally Posted by jeff5may View Post
A combined system is only as strong as its weakest component.
Sometimes .. not always.

Some combined systems are more robust than a single non-combined system would have been .. there can be a redundancy in the system design .. or the additional combinations can improve net performance (not be entirely dependent on it to function at all).

For example in my system design .. If 1 of the 2 heat pumps fail .. the system will still work (just not as well) .. even if both heat pumps fail .. the system will still work (just not as well) .. even if grid fails .. my system will still work (just not for as long as with grid) .. even if PV fails entirely .. my system will still work (just more from grid than if they do work) .. even if the solar thermal collector fails .. you guessed it .. my system will still work (just not as well) .. etc ... etc.
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