3 ms·

Interesting. It claims "95% combined heat and electrical efficiency". I'm assuming this number is comparing immediately after the electrical generation occurs (

Interesting. It claims "95% combined heat and electrical efficiency". I'm assuming this number is comparing immediately after the electrical generation occurs (i.e. - this doesn't have any transmission losses, while the electrical grid does). Does anyone have any comments on the comparison in overall gas -> electrical output efficiency between large grid-scale natural gas plants and small natural gas generators like this one?

jsmith45 4y ago
Gas power plants on the grid are pretty inefficient. Like a modern furnace they are pretty efficent at getting the heat energy out of the gas. However the efficiency of turning the heat into electricity is low. They get something like an average of 40% overall efficiency. The best gas turbine plants on the market can get about 60% efficiency max. If the power plants were able to provide the excess heat to nearby businesses and the like, they could be a lot more efficient overall, and there are some that have tried to do that, but transporting heat itself is not an easy thing to do efficiently, and many plants are things like peaker plants, which don't run consistently, making it even harder to sensibly use the "waste" heat in the nearby communities. Then there is the grid losses. Grid transmission loses 5 to 6% of the power in the US, making the grid 94-95% efficent.
- Schroedingersat 4y ago
  If energy were a little more expensive you could have jerry can sized packs of sodium acetate or similar. But noone really wants to fill up their boot with jerry cans and burn $3 worth of fuel for $2 worth of low grade heat. I wonder if there is a better PCM or thermochemical battery that could be worth moving on a not-train somewhere? Something that beats ice but works at not-4-degrees. Lye is okay but still a bit shy.
smartmic 4y ago
Wikipedia has some reasonable figures about Cogeneration fuel cells (Ene-Farm is one of those "MicroCHP" fuel cell systems for home usage[1]: > Co-generation systems can reach 85% efficiency (40–60% electric and the remainder as thermal).[5] Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90% For the "95% […] efficiency", I guess they take the hydrogen heat input for calculation of efficiency. What I miss are the losses from conversion of natural gas to hydrogen. This has to be considered when comparing efficienies eg. with gas fired power plants. So when it comes to large-scale Combined Heat and Power plants [2], it depends. There are not only different types of power plants (coal fired, gas fired, etc.) but also the heating part varies (process steam, district heating, etc.). If you go thermodynamically strict, you would also have to consider the quality of heat (at which pressure & temperature level is the heat extracted). This is normally not considered in the standard efficiency formula. [1] https://en.wikipedia.org/wiki/Fuel_cell#Efficiency_of_leading_fuel_cell_types https://en.wikipedia.org/wiki/Fuel_cell#Efficiency_of_leadin... [2] https://en.wikipedia.org/wiki/Cogeneration https://en.wikipedia.org/wiki/Cogeneration
i_am_proteus 4y ago
I suppose there's some ambiguity in the wording... there's no way it's 95% electrical generation efficiency. The key is that waste heat from electrical generation is used to heat an otherwise-cold home, and perhaps the hot water. That efficiency isn't going to be possible when it's warm outside.
cogman10 4y ago
Combining heat + electrical energy makes the stats really muddy. Does 10% of the burned energy end up as electricity? Or is it more like 30%? Hard to tell. The real question is, what do you do with that heat when you don't want it? What's the efficiency then? I will say, it would be pretty neat if one day we could get a mutli-device heat pump system going. Wouldn't it be cool if the heat pulled from your home was dumped into the water heater before being extracted vented? Or if instead of your fridge having a heat pump, it simply tied into a home heat pump system? This sort of thing would call for a centralized compressed lines. And, perhaps the reason that's not happened is because we don't want to worry about what happens when toxic gasses discharge into the home. Still, would be pretty neat if we could have a centralized cold and hot compressed gas system for buildings.
- aftbit 4y ago
  Commercial and larger residential buildings often have water at various temperatures as a utility. There will be a machine room that has large water-to-water heat pumps, then a chiller tower on the roof that takes hot water, evaporates some and cools the rest, then returns it to the hot-side heat exchanger. The cold side will circulate water around the building, where it will be used in water-to-air heat exchangers on the room or unit level to cool the building. In most climates, larger buildings need more cooling than heat, but doing the same thing with a hot water system is quite common as well.
- Dylan16807 4y ago
  > Combining heat + electrical energy makes the stats really muddy. > Does 10% of the burned energy end up as electricity? Or is it more like 30%? Hard to tell. > The real question is, what do you do with that heat when you don't want it? What's the efficiency then? And also, because electricity can pump heat so effectively, 10% efficiency in electricity is more valuable than 30% efficiency in heat.
- Schroedingersat 4y ago
  > This sort of thing would call for a centralized compressed lines The exchanger doesn't need to be the working fluid. You could have Freezer | Fridge | Ground | 30 degree water | 70 degree water With each | indicating water or another coolant in an insulated pipe. Insulate each reservoir and place it inside/outside depending on climate. Insulation on longer runs of piping might need to be exotic and expensive (aerogel or double walled vacuum sections), but there wouldn't be much of it. We already do something similarish for some AC systems

jsmith45 4y ago

Gas power plants on the grid are pretty inefficient. Like a modern furnace they are pretty efficent at getting the heat energy out of the gas. However the efficiency of turning the heat into electricity is low. They get something like an average of 40% overall efficiency. The best gas turbine plants on the market can get about 60% efficiency max. If the power plants were able to provide the excess heat to nearby businesses and the like, they could be a lot more efficient overall, and there are some that have tried to do that, but transporting heat itself is not an easy thing to do efficiently, and many plants are things like peaker plants, which don't run consistently, making it even harder to sensibly use the "waste" heat in the nearby communities. Then there is the grid losses. Grid transmission loses 5 to 6% of the power in the US, making the grid 94-95% efficent.

Schroedingersat 4y ago
If energy were a little more expensive you could have jerry can sized packs of sodium acetate or similar. But noone really wants to fill up their boot with jerry cans and burn $3 worth of fuel for $2 worth of low grade heat. I wonder if there is a better PCM or thermochemical battery that could be worth moving on a not-train somewhere? Something that beats ice but works at not-4-degrees. Lye is okay but still a bit shy.

smartmic 4y ago

Wikipedia has some reasonable figures about Cogeneration fuel cells (Ene-Farm is one of those "MicroCHP" fuel cell systems for home usage[1]: > Co-generation systems can reach 85% efficiency (40–60% electric and the remainder as thermal).[5] Phosphoric-acid fuel cells (PAFC) comprise the largest segment of existing CHP products worldwide and can provide combined efficiencies close to 90% For the "95% […] efficiency", I guess they take the hydrogen heat input for calculation of efficiency. What I miss are the losses from conversion of natural gas to hydrogen. This has to be considered when comparing efficienies eg. with gas fired power plants. So when it comes to large-scale Combined Heat and Power plants [2], it depends. There are not only different types of power plants (coal fired, gas fired, etc.) but also the heating part varies (process steam, district heating, etc.). If you go thermodynamically strict, you would also have to consider the quality of heat (at which pressure & temperature level is the heat extracted). This is normally not considered in the standard efficiency formula. [1] https://en.wikipedia.org/wiki/Fuel_cell#Efficiency_of_leading_fuel_cell_types https://en.wikipedia.org/wiki/Fuel_cell#Efficiency_of_leadin... [2] https://en.wikipedia.org/wiki/Cogeneration https://en.wikipedia.org/wiki/Cogeneration

i_am_proteus 4y ago

I suppose there's some ambiguity in the wording... there's no way it's 95% electrical generation efficiency. The key is that waste heat from electrical generation is used to heat an otherwise-cold home, and perhaps the hot water. That efficiency isn't going to be possible when it's warm outside.

cogman10 4y ago

Combining heat + electrical energy makes the stats really muddy. Does 10% of the burned energy end up as electricity? Or is it more like 30%? Hard to tell. The real question is, what do you do with that heat when you don't want it? What's the efficiency then? I will say, it would be pretty neat if one day we could get a mutli-device heat pump system going. Wouldn't it be cool if the heat pulled from your home was dumped into the water heater before being extracted vented? Or if instead of your fridge having a heat pump, it simply tied into a home heat pump system? This sort of thing would call for a centralized compressed lines. And, perhaps the reason that's not happened is because we don't want to worry about what happens when toxic gasses discharge into the home. Still, would be pretty neat if we could have a centralized cold and hot compressed gas system for buildings.

aftbit 4y ago
Commercial and larger residential buildings often have water at various temperatures as a utility. There will be a machine room that has large water-to-water heat pumps, then a chiller tower on the roof that takes hot water, evaporates some and cools the rest, then returns it to the hot-side heat exchanger. The cold side will circulate water around the building, where it will be used in water-to-air heat exchangers on the room or unit level to cool the building. In most climates, larger buildings need more cooling than heat, but doing the same thing with a hot water system is quite common as well.
Dylan16807 4y ago
> Combining heat + electrical energy makes the stats really muddy. > Does 10% of the burned energy end up as electricity? Or is it more like 30%? Hard to tell. > The real question is, what do you do with that heat when you don't want it? What's the efficiency then? And also, because electricity can pump heat so effectively, 10% efficiency in electricity is more valuable than 30% efficiency in heat.
Schroedingersat 4y ago
> This sort of thing would call for a centralized compressed lines The exchanger doesn't need to be the working fluid. You could have Freezer | Fridge | Ground | 30 degree water | 70 degree water With each | indicating water or another coolant in an insulated pipe. Insulate each reservoir and place it inside/outside depending on climate. Insulation on longer runs of piping might need to be exotic and expensive (aerogel or double walled vacuum sections), but there wouldn't be much of it. We already do something similarish for some AC systems