Tuesday, 31 May 2011

CO2 and fuels

A friend of mine commented to me about the previous blog article and mentioned that LPG was clearly the way to go on fuels.

Certainly I agreed that it burns cleaner, but I wasn't so sure about the amounts of CO2. A quick search reveals that (just like I uncovered in my Masters Thesis):
  • few know the facts
  • everyone likes to cite things poorly
  • different sources disagree
From my own experience of using an LPG car I get higher consumption of fuel, but the lower costs of the LPG compared to petrol offset this. Typically I use about 15L/100Km of LPG in my 6cyl car which then gets about 10L/100 when run on Petrol.

Now this NRMA site suggests that the mass of CO2 gas released of the exhaust pipe by the burning of one litre of fuel is:
  • 2.3 kg for Petrol
  • 1.5 kg for LPG.
however they refer to the Australian Greenhouse Office website where I am unable to verify such a figure easily (searching with this search query). None the less, if we run with that (as it seems reasonable) we would get (based on my above ratio) that I need to burn 1.5 times more LPG than I do Petrol which would result in:

1.5 x 1.5Kg = 2.25Kg or bloody close to petrol.

So, as Julius would ask "why is it so"??

Well energy stored in the chemistry is different. LPG is normally a simple hydrocarbon.

Energy is stored in the chemistry as the strengths of the bonds, Carbon can bond to Carbon in a single or a double bond, with something like 611 kJ/mol for C=C vs. 347 kJ/mol for C-C difference.

So without many Carbon Carbon double bonds LPG will not be able to store as much energy among the carbon and hydrogen in the compound as would something more complex (like petrol). Don't you wish you'd listened in chemistry more?

So to get the same power (you still want to drive at the same speed don't you?) then you simply must burn more LPG, thus the choice of LPG or Petrol would seem more or less CO2 neutral.

However, if you think about it, we burn petrol (or LPG) to get energy to power our engines. So if you have a choice to burn 2 butane molecules

or one benzene molecule

We would get more CO2 from the butane (because we'd have 8 carbon atoms) and we would get both more energy from the Benzene and less CO2, because it only has 6 carbon atoms and all the double bonds.

This is not an accident, chemists in the early 20th century poured over chemical understandings in order to get the most energy in the most compact form. So when you burn petrol you're burning stuff like:

and some of this

with a little of this tossed in to add to the energy per liter of fuel

The advantages however of LPG are not that its a compact energy storage, or that it gives us less CO2, rather its in other aspects. To quote from Wikipedia:
Two recent studies have examined LPG-fuel-oil fuel mixes and found that smoke emissions and fuel consumption are reduced
an advantage is that it is non-toxic, non-corrosive and free of tetra-ethyl lead or any additives
It burns more cleanly than petrol or fuel-oil and is especially free of the particulates from the latter

so, its not to say that I think LPG isn't a good fuel (in fact I've chosen it for my car) but just that I don't want people to be thinking that somehow its going to save the global CO2 problems (if you think we have one).

Saturday, 21 May 2011

Do electric scooters dream of being petrol powered?

Its starting to get fashionable to talk about Electric Cars again. The other day I was in at the local scooter shop getting a tyre sorted out for my Yamaha T-Max scooter (and pondering a purchase of a new 50cc scoot for my wife) when I spotted this electric scooter. So (being an engineering sort of fella) it is exactly in my nature to use this situation to mull over the whole thing (and present it to people who may not have thought about it).

I have been interested in the concept of an electric scooter for a while now but had not really done much research on the topic.

So since it was right in front of me I thought I'd ask some questions, take some pictures and write about it here.

I will say from the start that I like the idea of an electric scooter for city work more than petrol ones for the simple fact that most scooters are 2 strokes, stink and pollute something fierce.

India made a great move when they legislated their nasty "auto" taxis to use CNG rather than the regular 2 stroke ones of the past. Emissions fell and everyone is healthier and happier for it.

Its true that electric engines will need power from the regular power stations, which are in the main coal fired (at least in Australia). However at the very least we move this pollution to a single more efficient generation source (while introducing an number of other inefficiencies in the middle) which can be more controlled and monitored.

Before dribbling on about that too much I thought I'd toss in a comment about the rear drive on the scooter. A brush-less 48Volt 4000Watt hub mounted motor: man that means it can suck 83 amps!! wow

Which makes for some interesting observations about the changes in engineering of the swingarm and frame (because the forces are different now).

The motor can suck up to 4000 watts of energy out of your buttery but of course will only pull as much as is needed for keeping a constant speed when cruising along at a steady speed (say 50Kmh). This is of course exactly like a petrol powered motor, which sucks fuel faster when pulling power than does when cursing along. Interestingly both produce about 4000 Watts of energy (yes, 49cc scooter or electric scooter give you the same power to take off) which should come as no surprise because thats regulated by government.

[aside: to put this sort of tiddly power delivery into perspective, a "vanilla" motorcycle like a Suzuik GS500 has a motor that will deliver at least 38,000 Watts and a timid car like a Ford KA which squirts out something like 48,000 Watts of power. So as things go the electric scooter is not pushing the engineering envelope here]

Putting energy in:

People somehow think of petrol as fuel but electricity as energy, I blame our schools for creating this schizophrenic view of reality. The reality is that fuel (petrol, gas) is energy in liquid form. We release that energy by burning it. Motors turn that energy release into movement.

The electric bike stores energy in rechargeable batterys and gets the energy to recharge the battery from your wall socket using something like this:

This little device (which is about the size of a small shoe box) is the charger for the scooter.

To charge your scooter up you have to plug this in to the wall power and into the bike. You can not really run a long extension lead to of from it, or you will loose power so we meet:

Problem #1 - where can I recharge

If you have your own house and garage you can probably charge it up in your garage, but if you live in an apartment its quite unlikely you have power available where you park your scooter. So you'll need to find a place where you can park it and recharge it: which takes 4 hours. In contrast the regular scooter recharges with fuel at the local servo and takes about 5 minutes to fill and pay for.

So, with fuel being (at the time of writing) about $1.5 a Liter a petrol powered scooter takes about 5L in the tank and will set you back about $7.50 to fill up from dead empty. Its unlikely you'll run it dry, so you'll probably put in 3L at a time and walk into the servo to pay your $4 bill while grinning at the people who fill up their cars and are paying something like $60 for that.

So what does it cost to "fill up" the Electric scooter?

Well of course electricity costs, in my area right now power you pull out of the wall costs you about 19c per 1000 watts per hour. Its normally written as kWH which seems to confuse people who often profess to not understand their power bill. Its not all that had to get. Essentially if you plug in and turn on something which uses 1000W (or a kilo watt or 1kW) and leave it turned on for an hour it cost you 19c.

So how does this apply to the Electric scooter?

Looking at the charger we see that it supplies about 900Watts to the battery. I'm certain it is not 100% efficient so lets give it some grace and assume that its going to pull out 1000Watts of power from your power point in your home (or wherever its plugged into).

So (based on the above rate for power) a 4 hour charge will cost you something less than a dollar, 78c our thereabouts.

According to the information I have on the scooter (which you can verify here) For this princely sum you get to travel 90Km (only under particular conditions).

That is quite attractive. Sounds like its quite positive when reading the basics. So lets plumb into the ownership and do a little bit of thinking:

cost comparison

Ok, so 80 cents gets you 90Km on the scooter, but it will of course vary on how you ride and in what conditions. 90Km is of course also the maximum distance, so if you commute across town 25Km you'll not quite get two trips into the one charge (as 50 + 50 will put you out of battery) and you can't stop and top up on the way like you can with a petrol bike. The actual distance you will get may be less depending on factors like:
  • hills
  • number of traffic lights
  • how heavy you are on the throttle on take off (kiss bye bye to fast take offs)
This means that (unless you want to be pushing it home) you'll have to top up every day (fine if you park in a garage in your home, annoying if you have a flat).

So you may be plugging in again and paying that 80c every day instead of the potential discussed by the maker and seller of the bikes.So it may become more like 80c for that 50K round trip.

If you were to consider a petrol scooter (as a comparison) such as the Honda Scoopy, assuming you get something like 3l / 100Km (and some have suggested you can get 1.4L/100Km) you will pay $4.50 for 100Km or $2.25 for that 50Km round trip. Clearly the Electric scooter is in the lead here.

Yet, thats a worst case scenario too, as if do you get 1.5L/100km (which is actually likely) then that'll be more like $1.12 for the trip. Starting to look less like a clear winner as its much the same fuel cost as the 80c for the scooter isn't it?

Of course with the petrol version you have the flexibility that you KNOW how much is in your fuel tank, battery charge level is not as accurate and will depend on how cold it is. You can top up your fuel in minutes but need hours (back home where your charger is) to top up the electric scooter.

So this begs the question of how much is the convenience that petrol provides worth to you?


Back on the costs: an acquaintance of mine who has an electric bicycle (less power so smaller and cheaper battery) recently changed battery from the standard one. How much did that cost? Well think in numbers closer to $1000 than $500 and you're on the path.

So unless you're after a battery for one of those tiddly little electric bicycles (with all that implies) you're thinking big money for a battery for this scooter. This starts to lead into the next problem identified for the Electric Scooter and that is:

Problem #2 real operation costs:

Anyone who has owned a vehicle knows that there is inevitably more cost than just putting fuel into it. For a start there is repairs and depreciation. So, thinking about the above battery example, how long will your rechargeable battery last and what will it cost?

Well its only covered by 1 year warranty. So assuming you use the battery optimally (charge and discharge according to the makers ideals) you'll certainly get a year out of it, perhaps two. But what if you don't use it optimally and it fails outside of the warranty? Are you going to learn to do that or is convenience going to get in the way?

Consider that at the fuel prices of $1.50 /Liter (and before you say that may rise over 2 years ask yourself if power won't) you will get 20,000Km of travel from $450 of petrol.(*calculated at the worst fuel economy)

So using our example again: if you travel 25Km each way to work, thats 50Km per day = 400 days of travel.

Now, if that battery needs replacement (and ask anyone in Remote Control Helicopters how often that happens) then you'll be up for something between $500 and $1000 or perhaps more.

Yes, that's right ... your entire year of fuel bill will blown on a battery replacement. Which means in another way of thinking about it, that you are actually costing yourself an extra 80c a trip just for the hell of it when using an electric scooter.(not to mention all the issues like where do you charge it if you live in a high rise apartment without a garage)

Ok, but we're CO2 free right? That's got to be worth something hasn't it? Well, let me introduce you to ...

Problem #3 - CO2 generation

Its hard to get figures but it seems that (for coal powered stations) about 900g of CO2 is released for every kW of electricity. So given that the Electric Scooter will need upto 4kW from the wall every day (using the above situational example) it will thus end up generating about 3.6Kg of C02. Of course you could run it to the edge and charge every second day (and push it home occasionally) halving that figure, but that's up to you (and pushing is good exersize).

In comparison burning petrol will release about 625g of C02 for every Liter burnt, but if assuming you burn 1.5 Liters for your 50Km (that's 3L / 100Km) trip, at about a 1Kg of C02 (Note: these calculations are based on figures for C02 in petrol from here). If you get better fuel economy then you'll generate less.

so yep ... the petrol version generates less CO2 as well.

Its not looking good to me at this point ...


Naturally at this point someone will make the observation that Electric Scooters are at the beginning of their evolution and that petrol engines benefit from decades of development. Well if you have never gone to school or been taught to do any reading you may believe that line.

Let me assure you that both are quite developed technologies.

Petrol motors are actually not significantly advanced compared to 40 years ago (only we've worked on mainly curbing their emissions of other stuff) when you could buy a 70cc Honda Cub (lovely scooter) which used almost exactly the same amount of petrol as the bikes do today.

Then there is the Brushless DC motors used in the scooters, these have been in commercial use since 1886. So its mainly the battery technology which is changed to make storage more compact and perhaps controller circuits to make the motors more flexible. The basic physics of power required to move something hasn't changed between the motor types.

This does not effect the cost and pollution aspects of this calculation (except to say that modern batteries may be a more significant pollution issue than lead acid batterys).

Problem #4 - capital costs

Right now (if you look closely at the first picture) you'll see that we have been considering an electric scooter equivalent to a 50cc scooter costs about $4250, while a 4 stroke *(more powerful, much cleaner burning less polluting than 2 50cc stroke) Honda Scoopy will cost you about $2500

Yes, you did read that right, you'll pay nearly double for a less powerful electric scooter which will likely produce as much C02 (if that's of interest to you) and certainly more other significant toxic waste (read up on the disposal of Li batteries) than will result in the choice of a modern 4 stroke petrol powered scooter (compared to 2 stroke motors which are quite dirty creatures).

An excellent document prepared for the Victorian Competition and Efficiency Commission (here) suggests that scooters are more more effective people movers than cars are in cities. No surprise there...

To make the case even more for scooters, according to that same report: "A 2000 report (Motorcycle Transport, Powered Two Wheelers in Victoria) by transport researcher, Professor Marcus Wigan, found that motorcycle riders were the only transport mode to indicate no time delays as part of a trip."

There are articles available written to counterpoint this blog post (such as this one) where they suggest that Electric bikes are better than petrol powered ones. Its worth noting that these are largely written by people who actually sell the electric alternative (but not the electricity).

Its interesting to note that in the post I cited above the author makes the comparison between a electric bicycle and a postie bike (Honda CT110). The CT110 is a work horse, it'll carry another 40kg of mail and still accelerate and travel at 60Kmh if you desire, but the author makes a disingenuous comparison with an electric bicycle (which only carries you and you have to pedal too) comes out on top (when he ignores the battery issue). Yet the bicycle has a motor which wouldn't have enough power to pull the skin of a custard when compared to a postie bike ... gosh, bet that'll be popular on the farm!

But what about Solar charging? That would be CO2 free...

Well that's a good point (especially if you ignore the production of panels). If you were to get a 1.5 kW system it would likely produce enough energy on a good day to charge your scooter (if you left it at home) within 5 hours (you don't get 1.5kW all the time out of them, ask someone who owns one). So for the additional investment of $2500 (around about and you won't be back feeding the grid while your charging) you can be comfortable in the knowledge that you won't pay that extra 80c a day (but you'll still pay the other costs)

Woo hoo

But that's then an investment:
  • $4200 for the scooter, and
  • $2500 for the solar charger system (no rebate on that one)
taking your investment to $6700 for a system which needs you to leave the bike home duringthe day for charging ... sounds great to you too?

Depreciation bell ringing yet?

So in summary:

It seems like the following to me
  • I will save a little per trip (a best case of about 80c for a 50Km trip vs $1.25)
  • but I pay double to purchase ($4200 vs $2500)
  • unknown depreciation losses (but its fair to say you can't loose more than $2500 on the petrol scooter)
  • pay more for ongoing operational costs (the battery will die, motors often last ages)
  • actually create more pollution in almost every way by using an electric scooter over a petrol one.
  • You have to be able to park it where you can charge it (in a secure place or risk getting your charger stolen)
  • if your running low in power on the way home you can not just stop in to a servo to top up.
Why are you buying the scooter? Economy? Environmentally friendly?

The bottom line is if you want to be really environmentally friendly, go get a 110cc 4 stroke scooter stop driving your car and help save the worlds atmosphere and resources.

Monday, 2 May 2011

Alternative "normal" - Pentax 110 24mm

One of the things I've looked for is a reasonable "normal" lens for my G1 that's reasonably fast. now keep in mind when reading this, that this is under 'ideal' conditoins. I had plenty of time to focus and focused carefully using the magnification on screen in the GH1. On a GF you may miss the focal point and have nothing focused at all ...

Ok lets start off with the kit 14-45 zoom at about 24mm at f4.8 (wide open)


now, lets look at the Pentax 110 24mm lens ... there is no aperture, so its at f2.8


you don't even need to be pixel peeping to see that its reasonably soft around the edges. Just take a look at the green fabric in the middle foreground

At this overview size there isn't much obvious advantage in DoF between f2.8 and 4.8 ... in fact its really only just over a stop.

So lets have a quick pixel peep at the middle of the image where I focused on (manually) with each of the lenses. These images are about 50% scaled on this page, but if you click the image you'll get a 100% screen grab of the image.

The Kit zoom at 24mm


and then the 110 24mm lens


now lets look at the middle edge of the frame ... the Kit zoom

and the 110 24mm

hmmm ... not my thing, but maybe yours


for me I just don't see any significant advantage in the DoF found in the Pentax 110 lens over the kit zoom. These images really should show this more as the target is quite close to the camera, when compared to shallow normal depth of field on full fame 35mm images the difference here is not so much.

The 110 lenses are certainly nice and compact, almost absurdly so on the G1 / GH1 cameras ..

Perhaps on the GF it may be a more sensible alternative. However for me at least the Olympus 17mm or the Panasonic 20mm (despite it being more expensive) would be a better choice for a fixed focal length lens.

Why? well you get
  • AF
  • immediate zoom to confirm focus by just turning the lens (you need to press a few buttons)
  • something other than "wide open" (you know, you can stop down to 5.6 and really sharpen up)
Personally I still like the Pentax 110 50mm lens, as this is a bit longer than the kit 14-45, brighter by a few stops and really is compact.


I'm sure it makes even more sence on the GF. So for travllling light you can stick the 50mm lens in your pocket easily and when you pack that with either a normal (like the Oly 17mm or the Panasonic 20mm) you get a great compact two lens outfit.

The 18mm or the 24mm Pentax 110 ... well in my view you its sota fun to play with (and you'll need the adaptor for the 50mm, but you can leave home without it.

If you can get through the Japanese, I recommend reading this site. It was written before there were even commercial adaptors for mounting the 11o lenses on the G1


palm sunday

the palm tree has been busy disturbing the TV antenna, not to mention posing a threat to the house should a storm make it bang against the roof. I blogged about this back in June

and so we decided to get rid of it ... a week late for Palm sunday however.

the antenna remained intact.

no problem (except the fence :-)