The Death Of Fossil Fuels

[dyqik]

Oh, and furnaces are not the same thing as boilers. Boilers here either generate steam for steam radiators (common in older houses), or hot water for radiators (uncommon, usually baseboard radiator), or radiant underfloor heating (maybe more common than radiators, in newer houses in climates where AC isn't required). Furnaces directly heat air and send it through ducts around the house (probably the most common form of heating built into houses over the past century).

Replacing or supplementing a furnace with a heat pump to add central AC and moderate temperature heating is common - the cost differential between adding/replacing AC and adding a heat pump is essentially zero with the available rebates and tax credits. The running costs of natural gas furnaces are still lower than heat pumps in winter - the break-even is about a COP of 4 with our electricity and gas prices here over the past few years. But for oil or propane - which covers a lot of houses, as many places do not have gas supply pipes, the break-even COP is about 2.

For houses built without air ducts for a furnace, it's more common to install mini-split heat pumps, at least up here where most houses are multi-storey and often don't have enough attic space for ducts. Where houses are more commonly single level (e.g. Texas), it's usually easy enough to install ducts in the attics.

[Holylol]

Quick question on the definition of the COP that is announced by manufacturers for heat pump:
Is it defined as the ratio of heat power produced to mechanical power provided by the compressor? Or is it the ratio of heat power produced to electrical power provide to the compressor?
(so, is the compressor efficiency accounted for in the COP?)

[dyqik]

Quick question on the definition of the COP that is announced by manufacturers for heat pump:
Is it defined as the ratio of heat power produced to mechanical power provided by the compressor? Or is it the ratio of heat power produced to electrical power provide to the compressor?
(so, is the compressor efficiency accounted for in the COP?)

In the spec sheet for my heat pump, it's stated COP is equal to output heat/wall plug power. Resistive electric heat is also widely stated to have a COP of 1.0.

[FlammableFlower]

[urlhttps://www.theguardian.com/environment/2022/ma ... l-security]Hell's teeth they're slow, aren't they?[/url] I suppose we should be just a little bit thankful that some Tories are waking up to the idea that more renewables are a good thing...

[TimW]

Some peeps are claiming to have developed hydrogen tanks for aircraft...

that have demonstrated a 75% mass reduction compared to existing state-of-the-art aerospace cryotanks (metal or composite).
...
enabling H2-powered aircraft and eVTOL manufacturers to store as much as 10 times more LH2 fuel without adding mass.

https://www.compositesworld.com/news/hy ... ogen-tanks

Could be bit of a game-changer.

An aircraft equipped with GTL dewar tank technology could achieve as much as four times the range of a conventional aircraft using aviation fuel, cutting aircraft operating costs by an estimated 50% on a dollar-per-passenger-mile basis.

[Grumble]

Some peeps are claiming to have developed hydrogen tanks for aircraft...

that have demonstrated a 75% mass reduction compared to existing state-of-the-art aerospace cryotanks (metal or composite).
...
enabling H2-powered aircraft and eVTOL manufacturers to store as much as 10 times more LH2 fuel without adding mass.

https://www.compositesworld.com/news/hy ... ogen-tanks

Could be bit of a game-changer.

An aircraft equipped with GTL dewar tank technology could achieve as much as four times the range of a conventional aircraft using aviation fuel, cutting aircraft operating costs by an estimated 50% on a dollar-per-passenger-mile basis.

Awesome, the future is coming

[jimbob]

Some peeps are claiming to have developed hydrogen tanks for aircraft...

that have demonstrated a 75% mass reduction compared to existing state-of-the-art aerospace cryotanks (metal or composite).
...
enabling H2-powered aircraft and eVTOL manufacturers to store as much as 10 times more LH2 fuel without adding mass.

https://www.compositesworld.com/news/hy ... ogen-tanks

Could be bit of a game-changer.

An aircraft equipped with GTL dewar tank technology could achieve as much as four times the range of a conventional aircraft using aviation fuel, cutting aircraft operating costs by an estimated 50% on a dollar-per-passenger-mile basis.

This seems surprising:

"Based on our internal analysis of a De Havilland Canada Dash 8 Q300, which seats 50 to 56 passengers, the standard PW123B engine would typically support a range of 1,558 kilometers,” said Sergei Shubenkov, co-founder and head of R&D at HyPoint. “By implementing HyPoint's system and a standard liquid hydrogen tank, the same aircraft could achieve five hours of flight time or a max range of 2,640 kilometers. With GTL's tank, it could fly for 8.5 hours or a max range of 4,488 kilometers, indicating that this aircraft could fly three times further with zero emissions by using HyPoint and GTL compared with conventional aviation fuel," "That's the difference between this plane going from New York to Chicago with high carbon emissions versus New York to San Francisco with zero carbon emissions."

How is the hydrogen managing to achieve a greater range than kerosene? Even with a standard H₂ tank and their "HyPoint system"?

If it works for aerospace, would that also work for other systems? I'm thinking marine engines.

[Grumble]

Some peeps are claiming to have developed hydrogen tanks for aircraft...

that have demonstrated a 75% mass reduction compared to existing state-of-the-art aerospace cryotanks (metal or composite).
...
enabling H2-powered aircraft and eVTOL manufacturers to store as much as 10 times more LH2 fuel without adding mass.

https://www.compositesworld.com/news/hy ... ogen-tanks

Could be bit of a game-changer.

An aircraft equipped with GTL dewar tank technology could achieve as much as four times the range of a conventional aircraft using aviation fuel, cutting aircraft operating costs by an estimated 50% on a dollar-per-passenger-mile basis.

This seems surprising:

"Based on our internal analysis of a De Havilland Canada Dash 8 Q300, which seats 50 to 56 passengers, the standard PW123B engine would typically support a range of 1,558 kilometers,” said Sergei Shubenkov, co-founder and head of R&D at HyPoint. “By implementing HyPoint's system and a standard liquid hydrogen tank, the same aircraft could achieve five hours of flight time or a max range of 2,640 kilometers. With GTL's tank, it could fly for 8.5 hours or a max range of 4,488 kilometers, indicating that this aircraft could fly three times further with zero emissions by using HyPoint and GTL compared with conventional aviation fuel," "That's the difference between this plane going from New York to Chicago with high carbon emissions versus New York to San Francisco with zero carbon emissions."

How is the hydrogen managing to achieve a greater range than kerosene? Even with a standard H₂ tank and their "HyPoint system"?

If it works for aerospace, would that also work for other systems? I'm thinking marine engines.

It’s possible that this fuel tank is bigger than the kerosene tanks, but it doesn’t look like it’ll fit in the wings, so either it takes up passenger/cargo space or it gets slung under the wings and increases drag. Another factor is an electrical motor is a lot lighter than a combustion engine so it might make some savings there.

[dyqik]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

[jimbob]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

Volume is pretty important when air resistance is such a large factor in power usage.

[TimW]

The Airbus plan for hydrogen involves a tank in the body of the plane at the rear. The normal way to add volume to a plane is by a stretch, so that's a similar transformation. I assume it doesn't dramatically affect air resistance?

[shpalman]

The previous discussion in this thread started back here I think.

[dyqik]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

Volume is pretty important when air resistance is such a large factor in power usage.

It's not when installing the tank doesn't change the volume of the plane

[Gfamily]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

I saw a figure that if the Saturn V rocket burned Liquid Hydrogen rather than RP1 (kerosene), the LH tank would need to be 7x larger (almost twice as large in each dimension).

[dyqik]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

I saw a figure that if the Saturn V rocket burned Liquid Hydrogen rather than RP1 (kerosene), the LH tank would need to be 7x larger (almost twice as large in each dimension).

That's energy density by volume, not by weight. And the tank weights would have been much higher with 50s/60s tech.

[Gfamily]

The energy density by weight of hydrogen is 2.8 times that of gasoline or jet fuel, so if the tank is a bit less than half the weight of the hydrogen, you get a factor of 2 in energy storage per kg.

To that you can add another factor of about two for efficiency improvements of fuel cells and electric motors vs combustion engines.

I don't think volume is the limiting factor in aircraft cargo capacity, but weight.

I saw a figure that if the Saturn V rocket burned Liquid Hydrogen rather than RP1 (kerosene), the LH tank would need to be 7x larger (almost twice as large in each dimension).

That's energy density by volume, not by weight. And the tank weights would have been much higher with 50s/60s tech.

Yes, obviously; but 7x the fuel volume (even if not adding fuel weight) has to go somewhere. So either there will be longer bodies of the same cross section (7x longer?), or wider bodies.
Or the need for a significant reduction in payload volume.

[dyqik]

I saw a figure that if the Saturn V rocket burned Liquid Hydrogen rather than RP1 (kerosene), the LH tank would need to be 7x larger (almost twice as large in each dimension).

That's energy density by volume, not by weight. And the tank weights would have been much higher with 50s/60s tech.

Yes, obviously; but 7x the fuel volume (even if not adding fuel weight) has to go somewhere. So either there will be longer bodies of the same cross section (7x longer?), or wider bodies.
Or the need for a significant reduction in payload volume.

Does that affect the actual limits on capacity?

[jimbob]

That's energy density by volume, not by weight. And the tank weights would have been much higher with 50s/60s tech.

Yes, obviously; but 7x the fuel volume (even if not adding fuel weight) has to go somewhere. So either there will be longer bodies of the same cross section (7x longer?), or wider bodies.
Or the need for a significant reduction in payload volume.

Does that affect the actual limits on capacity?

If you have wider bodies, then you're affecting the air resistance. Which is important at the start.

[Gfamily]

The A320 has a cargo capacity of about 37m^3
Replacing the 27,000 litres of fuel capacity with ~190,000 litres of LH is going to take all of that and more.

ETA Clearly, it's not going to be a straight swap, but as a back of the envelope calculation, I don't think it's too far out to say "it's not going to make a negligible difference"

[dyqik]

Yes, obviously; but 7x the fuel volume (even if not adding fuel weight) has to go somewhere. So either there will be longer bodies of the same cross section (7x longer?), or wider bodies.
Or the need for a significant reduction in payload volume.

Does that affect the actual limits on capacity?

If you have wider bodies, then you're affecting the air resistance. Which is important at the start.

The question is whether you need wider bodies, and whether that makes a big difference to the coefficient of drag.

Remember, fuel isn't only stored in the bodies right now, but also in the wings. And a wider body doesn't necessarily make a huge difference to the drag, which is dominated by wings etc. Not having fuel tanks in the wings may open up a bit more design space.

[dyqik]

The A320 has a cargo capacity of about 37m^3
Replacing the 27,000 litres of fuel capacity with ~190,000 litres of LH is going to take all of that and more.

ETA Clearly, it's not going to be a straight swap, but as a back of the envelope calculation, I don't think it's too far out to say "it's not going to make a negligible difference"

You've missed the factor of two improvement in efficiency of fuel cells vs combustion engines there - it's more like 100k liters of LH2 needed.

That takes up an additional 7m of fuselage length (cabin width is 3.7m), which is enough that you'd not just add it all while keeping the same diameter of the body.

It's not simple to add, but it's certainly not non-viable to include in a design, particularly since it doesn't weigh very much.

[shpalman]

Yes, obviously; but 7x the fuel volume (even if not adding fuel weight) has to go somewhere. So either there will be longer bodies of the same cross section (7x longer?), or wider bodies.
Or the need for a significant reduction in payload volume.

Does that affect the actual limits on capacity?

If you have wider bodies, then you're affecting the air resistance. Which is important at the start.

https://en.wikipedia.org/wiki/Airbus_Beluga

[Martin_B]

The A320 has a cargo capacity of about 37m^3
Replacing the 27,000 litres of fuel capacity with ~190,000 litres of LH is going to take all of that and more.

ETA Clearly, it's not going to be a straight swap, but as a back of the envelope calculation, I don't think it's too far out to say "it's not going to make a negligible difference"

You've missed the factor of two improvement in efficiency of fuel cells vs combustion engines there - it's more like 100k liters of LH2 needed.

That takes up an additional 7m of fuselage length (cabin width is 3.7m), which is enough that you'd not just add it all while keeping the same diameter of the body.

It's not simple to add, but it's certainly not non-viable to include in a design, particularly since it doesn't weigh very much.

Adding the fuel in the fuselage body might also make the aircraft handle significantly differently at take-off and landing (ie, 'full' and 'empty'). Changing the centre of gravity of the plane can make huge changes to trims required.

Maybe the computer systems can handle that these days such that the pilots won't notice the difference, and I doubt that the answer will be as simple as adding a 7m fuel tank at the back of the fuselage, but any sort of long, thin fuel tank stretching along the fuselage to counter centre of gravity changes will negate savings in fuel tank weight, and could add access and safety issues.

[Gfamily]

The A321 is about 7 metres longer than the A320, so it's not too much of a stretch to make it work.

[Martin_B]

The A321 is about 7 metres longer than the A320, so it's not too much of a stretch to make it work.

Elongating the fuselage isn't the bit I had concerns about. Both the A320 & A321 will have a centre of gravity somewhere around the wings and it won't change significantly between loaded and unloaded conditions.