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Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
We have plenty of sunlight.
America for the cost of a round of stimulus or a fraction of the cost of one of it's wars could build solar thermal plants to supply it's entire electricity generation almost all of the time (distribute it over a couple of the many high sun-day deserts the US has, throw in 2 days worth of heat storage and the chance of having to start up your non renewable backup plants is small) and a HVDC distribution net.
The present level of energy consumption doesn't have to be a problem, at this point we are simply making it one ...
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I read about this in popsci a while ago. The idea is to make roads out of solar panels --instead of asphalt we'll have glass panels. They have a few problems though. 1; Dirt on the road. 2; Winter 3; They cost 10K per 10 sqft panel.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
Steve McConner wrote ...
The problem is just that we use far more energy than what we eat. 1kW per person is considered some sort of reasonable target for world power consumption. I exceed it a little myself, Americans exceed it by about a factor of 4. But the consumption of food energy is only a couple of hundred watts per person.
Effectively we each have an army of about 10 slaves, and they all have to be fed. Currently they eat oil, but once the oil runs out, they will have to be fed some other way, or scrapped. The world production of all the kinds of bio-stuff combined is not enough.
I ride a bike to work, so my transport is already powered by sugar, cakes, pasta, bread, pizza and so on.
1kW per person seems quite high, unless this is meant to include not just personal electricity usage, but also energy usage such as heating oil, petrol, and so on. Right now my household averages 250W per capita, more like 750W per capita during the hottest summer months.
At any rate, I don't think it's a solution to the world's energy problems, for sure. I was thinking more along the lines of a personal power port in the range of 5-20W. Just enough to run a personal device or two, like a tablet or smart phone, for convenience's sake. Many people in developed nations are now consuming more energy than they need, so it doesn't seem like the energy would be missed. Whether the technology ever becomes safe and commercially viable is another matter all together.
Of course, ultra caps with low leakage and energy densities on par with rechargeable batteries can give us some other really great and clever ways to harvest energy from humans. For example, I have a crank-powered radio that works quite well. Unfortunately, since the circuit is simplistic and poorly designed, something like 90% of my cranking power is wasted in the voltage regulator, and as heat in the batteries. If I crank faster, the efficiency is worse. A good set of ultra-caps would let me generate enough electricity to run the radio for hours in just a minute or two of vigorous cranking, rather than in ten minutes of trying to crank at the optimal speed. A small, pocket-sized crank charger might be just the thing to top off a dead smart phone or notebook battery. Similarly, one could design a regenerative braking system for bicycles that would charge personal devices for little to no extra effort at all.
Registered Member #3040
Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237
Apparently my sister and brother in law have had combined power and heat solar panels fitted to their house, bearing in mind they live near Wales, not known as the sunniest of places they are providing enough electricity for their needs plus they sell some back. The heat side only provides a pre-heat to their existing heating system so it needs less conventional energy to finish the job. Maybe the future is in localised energy production rather than centralised.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Chris Russell wrote ...
1kW per person seems quite high, unless this is meant to include not just personal electricity usage, but also energy usage such as heating oil, petrol, and so on.
It includes everything including food, as far as I know. And the target was 2kW.
Martin: The UK government is currently offering 25p per kWh for electricity generated by these small renewable plants. That makes them attractive to a lot of householders. We'll have to see how long that survives the budget cuts, though.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Can someone who knows more about cars than me calculate the rate at which energy is transferred to a car by filling the tank with petrol? My guess is that it's something like a litre per second and that's about 37KW For the capacitors in the original post to live up to the expectation of charging in seconds and also providing energy equivalent to a petrol tank you would need to be talking tens or hundreds of kilowatts. How does anyone plan to plug that in to the power grid?
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Wow, 40 cents a kilowatt-hour? That's really expensive, power only costs about 5 cents a kilowatt-hour here.
Good point bored chemist. If the power grid can't supply the watts then the electric car is dead. IMO, the hydrogen fuel cell is the way to go. Fill her up in a minute or so and you're good to go, just like gas. The problem we have though is making a reliable cell. The best technology that doesn't involve platinum is the proton exchange membrane, but it doesn't last very long and can't supply a whole lot of current. I like the HHO cars though because it's easy to make your own fuel at home.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
A liter per second seems a little fast, but it's in the correct ballpark, I think. Here in the US, pumps are limited to an absolute maximum of 37.8 liters per minute. Most stations will want to get close to that so that customers can get in and out quickly, but not so close that aging components could lead to an EPA fine, so say 0.5L per minute on average.
As far as straight up energy, petrol has about 34MJ/liter, so the average fuel pump delivers around 17MW. Of course, that's not a fair comparison, as internal combustion engines can only make use of a fraction of that energy, around 20% for an efficient car. That's still a staggering 3.4MW.
If we assume that the average petrol powered car is 20% efficient and has a fuel capacity of 45 liters, that's a total equivalent energy reserve of 306MJ. If electric cars are to have the same range, and they're around 80% efficient, they'll need a total of 383MJ. That's hours and hours to "fill up" at any sort of sane charging rate.
So, overall, even if the right energy density were possible, there are some logistical problems to overcome with trying to make electric cars a drop-in replacement for petrol cars.
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Hybrid batteries tease big energy capacity while charging in seconds
