Electric cars.

That's not the point, though.

Most people don't 'get' them at all - but you can't get a petrol engined car with that interior space and auto box from anyone else that'll turn in around 50mpg, even if you're driving it like a rental - I only get

(And it's not worth comparing with the current generation of 'eco' diesels, either, as the latest small capacity stuff may have low emissions, but in the real world they're gutless and thirsty, and that's before you've stuck an auto box of some kind on them)

Gutless isn't a problem around town. I suspect used for what they are really intended for short trips urban enviorement you get a reasonable return no small engined car is going to give you performance and your not going to get decent mpg if you use these vehicles at motorway speeds

Actually, the Eco diesels should excel on the motorway - and they can be coaxed to reasonable economy if you stick to 70mph or less. But you have to get there with all the speed of continental drift - it's on urban roads where the economy takes a nose-dive.

Hybrids are amazing around town and lose out on the motorways, but I was still getting 48mpg from mine - my colleagues were getting 10-20mpg more, though.

The latest model Prius on a trip to Scotland was getting over 60mpg as evidenced by the fact that the lifetime mpg rose to 59mpg during the run with me driving, with the owner it has not been quite so good. Two heavy people plus luggage at over 70 where plausible. There are few cars that outdrag a Prius in normal driving at the traffic light grandprix, the performance is perfectly adequate, and anyone that says it isn't has clearly not actually used one in real world conditions.

total petrol.

The twin turbo petrol VW's ain't gutless. Still prefer diesel for the torque.

No such thing.

They're super and turbo charged. You're right, they're not gutless (and nobody claimed they are!) - but they're unreliable and thirsty.

OH OK then.

They must have improved it dramatically from the early ones. I drove a Mk1 from London to Aberdeen and back again - fully loaded in one direction, just me in the other. It had to be driven hard just to keep up. Fuel used

- not some guestimate based on the OBC - came out at 28 mpg. Rather worse than my petrol auto BMW which wouldn't have been so hard work. It was also a perfectly horrid car to drive on the open road. Going up Shap it was reduced to under 60 mph - it's a long time since I'd driven a car that slow.

Of course around town with a charged battery it felt quite lively. But dire on the open road where the battery spend most of the time exhausted.

Oh - it wasn't just a poor example I had. Autocar reported similar poor fuel consumption in give and take driving. Only in heavy stop start traffic did it shine.

The Mk1 was pretty awful - but the Mk2 was a completely different proposition - and was really the coming of age of hybrid as an emerging and usable technology.

The best renewable technology, and often forgotten, is heat pump technology. Taking heat from the environment. It works with no clouds or wind, even in winter. It is basically the fridge in reverse, using a fluid with low boiling point, such that it can absorb heat from environment when liquid at low temp and give off heat when gas form at higher temperature. The problem though is delicate valve control and

pumping, although modern computer control could help. The pump takes some of the energy, but there is a total gain.

It sounds a bit crazy at first that you can extract energy from cold environment and put it into e.g a warm building. But the trick is the two-phase liquid/gas medium. each state satisfies second law of thermodynamics. Systems are commercially available, but it is still quite a considerable outlay. But compare this with solar panels, and I think heat pump will come out on top, at least for domestic heating.

Second problem: Efficient recovery of electricity from heat. Looking around on internet, there is a lot of research in this area. E.g. they are trying to get electricity back from the inevitable heat loss in the internal combustion engines, especially bigger engines in buses and lorries.

Too bulky for many installations. The heat supplied to the building is at a low temp and really only any good if you have space for air ducting or underfloor heating.

But that's at air temp 7°C and higher, just when you need it most it's piss poor. The CoP drops a lot on cold days and really takes a hit if it's below zero. Only thing to do is oversize the unit and pay for the power it eats or buy a gas boiler.

I know someone with one these.

For vehicle use a fuel cell needs a compact high energy density fuel. Hydrogen is pretty poor, needs a very expensive tank, there is no supply infrastructure. So a hydrocarbon like LPG is about the best choice for a hybrid electric / fuel cell range extender. A fuel cell's efficiency means far less fuel is needed to go the same distance (about 1/3 to

So long as you are good distance from the water supply, incoming mains water in UK is always between 9°C and 13°C. That's because only a few feet down the ground temp is nearly constant. A bore hole heat exchanger or subsurface grid (under lawn or car park) will work in all weathers. But the cost of installing either makes them unattractive.

The thing is with electric cars is that they are so expensive. It took a lot of money to develop and research them and that cost has been placed onto the price tag.

I think electric cars will have their day but at the moment there are better fuel efficient alternatives out there which are cheaper.

Mercedes Service

Cars with internal combustion engines were very expensive initially. In the 1930s a car was a similar price to a house. Investment and economy of scale has brought the price down to a few percent of the cost of a house today.

The difficulty with electric cars by contrast is the energy density of the fuel store. A tank of petrol or diesel is much lighter than a rechargeable battery giving comparable range; as well as being much cheaper. Over 100 years of development has not altered the situation - a rechargeable battery now is possibly only twice the capacity weight-for-weight than a battery of around 1900.

A substantial part of the motor industry would agree with you there. Toyota= , for instance, are pulling their all electric iQ citycar and Audi has cann= ed the A2 Electric supermini. Both companies are suggesting that at present= hybrid and Plug in Electric hybrid is the way to go.

While BMW is still going ahead with the Electric i3 there is a hybrid versi= on in parallel.

The harsh judgement of economics of production and the high purchase price = is putting the dampeners on right now. However in the future?

It isn't just the weight, but the time taken to charge it. You can fill a tank of petrol or diesel in a couple of minutes, charging a battery takes hours.