Anti log burner brigade

[twentysix by twentyfive]

You're dead or alive.

Schrodinger again

 

[roubaixtuesday]

700 bar sounds a hell of a lot. Normal SCUBA tanks are 230bar with 300bar as a heavier and less satisfactory alternative. You don't even get the expected extra 50% in a 300 bar tank as at the higher pressures gas becomes less compressible as it were. 700bar tanks would be extremely thick and heavy and it would cost a lot more (energy and money) to pump it up that high, as well as not getting as much extra as you'd think. Hydrogen is also somewhat problematic material reacting with steel and so on. You really don't want your 700bar tank going brittle !

Carbon fibre rather than steel for the Mirai, and ~90kg weight for 5kg hydrogen, from Wiki:

High-pressure hydrogen tanks[edit]​

The Mirai's high-pressure hydrogen tank and rechargeable battery pack on top
The Mirai has two hydrogen tanks with a three-layer structure made of carbon fiber-reinforced plastic consisting of nylon 6 from Ube Industries[50] and other materials. The tanks are 122 litres (27 imp gal; 32 US gal) combined,[51] and store hydrogen at 70 MPa (10,000 psi). The tanks have a combined weight of 87.5 kg (193 lb),[45][42] and 5 kg (11 lb) capacity.

 

[roubaixtuesday]

There is Dinorwig Hydro etc ? And I've heard similar plans to have warehouses of weights that can be raised to the heights when it's windy or sunny and then spun down to produce electric when we need them ?

Dinorwig's total capacity is very small compared to winter energy usage.

Dinorwig capacity is quoted as 9 GWhr

https://en.wikipedia.org/wiki/Dinorwig_Power_Station#:~:text=The scheme can supply a,9.1 GWh (33 TJ).

Annual UK electricity demand is 320TW, so a Dinorwig scale supply would only run the grid for 15 minutes.

Dinorwig is intended to balance usage a bit during the day, not to store energy between seasons.

Scaling up electricity storage is very, very difficult.

 

[icowden]

I wouldn't expect leakage to be an issue with this - apparently the Toyota Mirai has hydrogen leak detectors.

It's unlikely to leak though given it will mostly be empty due to the lack of places to actually fill up with Hydrogen...

 

[roubaixtuesday]

It's unlikely to leak though given it will mostly be empty due to the lack of places to actually fill up with Hydrogen...

You're right of course but the biggest issue with hydrogen is I think the round cycle efficiency; compressing gas to 700bar takes a mahoosive* amount of power. I think I've seen figures quoted that the round cycle efficiency is only about 30% or something. So you need 3x the generation capacity with hydrogen vs batteries.

* Customary unit of measure. One mashoos = 1 kWhr/kg. Various figures around 6 mahoos are quoted online.

 

[BoldonLad]

There is Dinorwig Hydro etc ? And I've heard similar plans to have warehouses of weights that can be raised to the heights when it's windy or sunny and then spun down to produce electric when we need them ?

There has long been hydro electric storage schemes, which are similar to what you describe, but, using pumped water instead of weights.

I didn't say there was NO means to store electricity, I said that efficient storage was a challenge.

 

[BoldonLad]

You're right of course but the biggest issue with hydrogen is I think the round cycle efficiency; compressing gas to 700bar takes a mahoosive* amount of power. I think I've seen figures quoted that the round cycle efficiency is only about 30% or something. So you need 3x the generation capacity with hydrogen vs batteries.

* Customary unit of measure. One mashoos = 1 kWhr/kg. Various figures around 6 mahoos are quoted online.

Very interesting, but, at no point was I suggesting we use hydrogen to power cars, or, anything else, other than possible generators which could produce electricity. I am not a technical expert, but, as I understand it, generation of electric and distribution of electricity are well understood and developed technologies, what we do not have are similar technologies to store "green" electricity, for use on demand, rather than when the wind blows, sun shines, etc etc

Caveat: I could be wrong

 

[BoldonLad]

Dinorwig's total capacity is very small compared to winter energy usage.

Dinorwig capacity is quoted as 9 GWhr

https://en.wikipedia.org/wiki/Dinorwig_Power_Station#:~:text=The scheme can supply a,9.1 GWh (33 TJ).

Annual UK electricity demand is 320TW, so a Dinorwig scale supply would only run the grid for 15 minutes.

Dinorwig is intended to balance usage a bit during the day, not to store energy between seasons.

Scaling up electricity storage is very, very difficult.

MY point exactly

 

[Gillstay]

In the past I chose a diesel car because of the reduced CO2 emissions thinking I was doing "the right thing". There was no cost saving for me personally with the way my company car deal was structured, so if anything it was a slight sacrifice vs the more hooligan inclined petrol alternative. Anyhow the trend went against diesel subsequently for reasons of particulate pollution so it seem it was the wrong choice.

If your after helping with global CO2 then a diesel as it emits less, is better if your after helping local humans with breathing problems then its petrol. So you may not have been wrong, it depends on your outlook.

 

[Profpointy]

Carbon fibre rather than steel for the Mirai, and ~90kg weight for 5kg hydrogen, from Wiki:

High-pressure hydrogen tanks[edit]​

View attachment 716440 The Mirai's high-pressure hydrogen tank and rechargeable battery pack on top
The Mirai has two hydrogen tanks with a three-layer structure made of carbon fiber-reinforced plastic consisting of nylon 6 from Ube Industries[50] and other materials. The tanks are 122 litres (27 imp gal; 32 US gal) combined,[51] and store hydrogen at 70 MPa (10,000 psi). The tanks have a combined weight of 87.5 kg (193 lb),[45][42] and 5 kg (11 lb) capacity.

5kg hydrogen would presumably have similar calorific value as a couple of gallons of petrol, so nearly 90kg of carbon fibre to merely contain it seems bonkers, although if they put up with a bigger volume at 200bar I guess they could reduce the weight required

 

[roubaixtuesday]

5kg hydrogen would presumably have similar calorific value as a couple of gallons of petrol, so nearly 90kg of carbon fibre to merely contain it seems bonkers, although if they put up with a bigger volume at 200bar I guess they could reduce the weight required

Hydrogen quoted here as having ~3x the calorific value of petrol on a weight basis.

https://world-nuclear.org/information-library/facts-and-figures/heat-values-of-various-fuels.aspx

So 5kg h2 is ~15kg petrol, ~20 litres I guess.

But I don't think many people believe hydrogen will emerge as a mainstream vehicle fuel, battery seems much better on almost all fronts.

 

[Ming the Merciless]

If your after helping with global CO2 then a diesel as it emits less, is better if your after helping local humans with breathing problems

Then it’s don’t bloody drive if your journey is less than 5 miles…

 

[Deleted member 35268]

I have a log burner and I use it occassionally at weekends when it's really cold in Winter (Oct-Feb). Rather than put the heating on for the whole house, it warms up the living room. I use seasoned wood and the burner is a fairly efficient model (rated at 77%), a Scan Andersen.

As an aside - I cycle to work 90% of the year rather than drive, a saving of £800 in fuel, and about 1.5 metric tonnes of C02.

I "liked" to think I was environmentally aware, but alas my stove is obviously a contradiction to that.

 

[ebikeerwidnes]

I have a log burner and I use it occassionally at weekends when it's really cold in Winter (Oct-Feb). Rather than put the heating on for the whole house, it warms up the living room. I use seasoned wood and the burner is a fairly efficient model (rated at 77%), a Scan Andersen.

As an aside - I cycle to work 90% of the year rather than drive, a saving of £800 in fuel, and about 1.5 metric tonnes of C02.

I "liked" to think I was environmentally aware, but alas my stove is obviously a contradiction to that.

Long term - and from a World Wide viewpoint - then this is pretty friendly
the wood burner is using CO2 that was recently fixed from the air - so you are simply sending it back rather than using old rotten dinosaurs

it is the local pollution that can be the problem - but from what I have read seasoned wood it not too bad
The problem is that a lot of people dry the wood out for a few weeks and then burn it - and this is the problem in urban areas

 

[MrGrumpy]

The problem is that a lot of people dry the wood out for a few weeks and then burn it - and this is the problem in urban areas

You soon find out if your wood is not dry enough ! When your gas bill for the year can run to into nearly £2k a year , you’re going to try and shave that anywhere you can . I’ve offset some of my carbon foot print . Bought an EV and fitted solar PV to the house . I think I can justify firing up my log burner on cold nights or weekends .