the sinclair c5 - 20 years ahead of its time ?

Ben84

mech wrote: »

First of all, The 1.3 litre Ford Ka is listed as being 70bhp, which is 52,220W. I don't know where 37,000W comes from.

Is that the current production model? They were available in smaller engine sizes in the past.

mech wrote: »

However, that isn't a realistic indication of power consumption as it's a peak figure. At 60mph on the flat it would probably be using less than half that. Less still at slower speeds. You only need the 50kW for acceleration and climbing hills. Fairly brief usage. So you size the electric motor in your electric or hydrogen fuelcell car to match this, but it doesn't tell you how much electricity you will consume any more than the 28kW rating of my heating boiler tells me how much gas I use.

That's a fair point. It is very hard to tell how much energy a car uses because there are many variables. It would be helpful to have averages. A lot of energy is lost in normal driving conditions. It's not just how efficient your engine is or what output it's running out, a lot of energy has to be wasted by regularly breaking and stopping the car.

mech wrote: »

To sensibly gauge the required solar capacity you first need to know the number of miles you can drive per kWh. For plug-in electric vehicles you can find figures of between 2 miles and 4 miles per kWh for vehicles that exist today. That's mains-to-wheels, so includes battery losses. (These are proper everyday cars, not lightweight plastic tricycles which probably do >10miles per kWh).

Electric motors are significantly more efficient than internal combustion engines, but electric has other large energy losses earlier in production and distribution. Around 60% of the energy input at the power plant is lost by the time it reaches your socket. This is a common problem with any process that depends on many energy conversions.

mech wrote: »

You don't need a transformer. Just attach the panels directly to the electrolytic cell.

Average mileage is generally taken to be 12,000 miles per year in the UK. That's 33 miles a day, averaged. Not very challenging.

12,000 miles at 3 miles per kWh is 4,000kWh. A 6kW solar array should be able to generate that in a year.

But this is a hydrogen powered car, not an electric car. You'll need a fuel cell to make hydrogen become electric. Fuel cells using hydrogen are about 50% efficient, and these inefficiencies seem difficult to overcome. Fuel cells also become more inefficient when you draw more current from them, and the motor needed to drive a normal car will draw a lot of energy, so this limitation until resolved will be a big problem for fuel cells in demanding applications. I believe the 6kW solar array has at least doubled.

mech wrote: »

When there isn't enough sun you could top up from the grid and sell the excess onto the grid in summer (obviously the grid will need some backup capacity for this to work). Is it cost effective? At £5,000 per kW of installed photovoltaic panels in a domestic system: no. Is it feasible at some time in the future? Possibly.

One of the reasons why I said you'd need a lot of solar cells is because of those months, usually January-February time in this climate when solar cells produce very little electric. The average distribution of solar energy collected by solar PV is very unequally distributed across the year, thus the need for a massive solar PV array.

However, using the national grid as a battery isn't something I'm so enthusiastic about, which is why I didn't even mention the idea. We need energy when we need it, not when the natural environment happens to provide renewable energy. January-February is a perfect example, as this is when houses all across the UK will be plugging in electric fires, and yet there is very little solar energy available. If everyone used the national grid as a battery we would end up with a surplus of energy at times we may not need it, and a shortage when we do need it.

The reason why it's possible to sell electric back to the power company is because they're obliged to buy your excess electric, and this is where the plan would not work if many people did it. In summer the national grid would get flooded with excess electric and everyone's meters would go backwards, so when the winter comes and we would need electric from the grid we wouldn't be paying for it, and yet it would have to come from conventional sources that need to be paid for. The power plants and distribution infrastructure cost a lot of money to build and operate. There is no way the exceptionally favourable conditions under which companies are currently obliged to buy your surplus electric could be enjoyed by any large numbers of the public, which is why I'm unconvinced that using the national grid as a battery is going to be the answer for most of us.

mech wrote: »

That's because your figures were unrealistic.

It's not so simple as that. I have carefully considered them, I just don't agree that using the national grid as a battery is going to work on a large scale, which is why I believe we'd all need huge impractical amounts of our own equipment. I also don't believe the process of turning solar PV output in to energy that's moving your car is as efficient as you suggested. There are so many conversions going on, and some like the fuel cell are big losses.

mech wrote: »

Solar concentrators in hot countries driving free-piston stirling generators could be another option. This is already more efficient than the most efficient experimental photovoltaic panels. The problem is how to export all that electricity to places such as the UK. An energy carrier is needed. This is where hydrogen could come in useful.

Large scale solar thermal is likely to be the best answer. People can share the cost that way and bring it down hopefully. Still, as I've said earlier in another post, solar thermal plants currently make very little electric compared to conventional ones, even though some of them achieve good efficiency. They also depend on the weather and occupy large amounts of land.

The reality of powering cars that resemble ones we have today with renewable energy, and us owning as many as we do and driving them as much as we do, still looks very difficult. My biggest annoyance with politicians and energy companies who talk about hydrogen is that very few (none I've heard) have dared even suggest we might just have to have less cars and drive less in the future, and yet that possibility seems much more realistic right now. Large scale hydrogen power is still looking unlikely, and until we overcome a good number of the many problems I don't want to bank our future on it. Particularly not when we have many other answers like public transport available right now.

moonrakerz

Ben84 wrote: »

Is that the current production model? They were available in smaller engine sizes in the past.

Ka has always been 1.3 - apart from the Street/Sport Kas which were 1.6

Cardew

IIRC early Beetles and 2CVs made do on about 20kW, and although they didn't accelerate as fast as my Ferrari!, something in that order would suffice for a town car.

Leaving aside how the electricity is generated, the problem for any alternative propulsion car is still the ability to store sufficient energy for even a modest range.

freddykruggar

http://www.teslamotors.com/