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Whatever happened to the water-fueled engine?

 
 
parados
 
  1  
Sun 12 Jun, 2011 02:35 pm
@georgeob1,
I think you've failed to include the efficiency in your calculation now george.


Some rough numbers....

A liter of gasoline would get you about 20% return.
10 kwh of electricity gets you 80%.

You get 4 times the return from electricity.
1.50/4 = .375
georgeob1
 
  1  
Sun 12 Jun, 2011 08:31 pm
@parados,
That works only if you can find some free electricity floating around in nature. In fact you can't. Electric power is produced in a heat engine that burns coal, natural gas or is fuelled by nuclear fission. Assuming it was produced in a modern compoind cycle gas turbine plant (about the only thing EPA will permit now) . The thermodynamic efficiency of this process is only slightly greater than that of a moderrn automobile burbing compressed natural gas (the same fuel). Add in the added losses in transmission, battery storage & discharge and the electric motor and you have a significant net loss in the comparison.
raprap
 
  1  
Mon 13 Jun, 2011 12:06 am
The Otto (gasoline) and low speed diesel have thermodynamic efficiencies in the range of 25% to 35%-efficiency. A super-critical steam plant (coal) is about 45% thermodynamic efficiency and a steam cooled combined gas turbine is about 60% thermodynamic efficient.

Toyota by using turbos and high compression ratios is shooting for a 45% thermodynamic efficiency from a car engine.

However, the thermodynamic lost heat is already lost in generating electricity from the wall plug---you pay for a kw-hr and you get a kw-hr.

Rap
0 Replies
 
parados
 
  1  
Mon 13 Jun, 2011 07:46 am
@georgeob1,
So, if I pay 15 cents per kwhr I only get .3 kwhr for that 15 cents?

Where do you get your electricity from?
0 Replies
 
georgeob1
 
  1  
Mon 13 Jun, 2011 01:19 pm
There's a lot of mistated "fact" and confusion over the the differences between the energy efficiencies of power systems and their current retail prices. In addition Raprap's "facts" concerning the thermodynamic efficiencies of heat engines are generally high - even relative to the most efficient (but little used) prototype experimental plants.

In the first place the price of a unit of energy, whether expressed as BTUs, or KwHr, or FtLbs or KgM varies with the fuel medium itself (i.e. coal, petroleum, natural gas, or enriched uranium). These prices depend on demand, availability and the cost associated with the infrastructure for distributing it. In general enriched uranium is the cheapest fuel, by a fairly large margin, in terms of cost per unit of useful energy. The price of natural gas in the U.S. has fallen dramatically in the last six months, mostly due to the large expected supply associated with the new shale finds in several areas of the country (and around the world). The resultant increased demand and the emerging shortage of the water required to extract the gas will likely cause the price to rise back closer to its earlier levels. We have all seen that the price of petroleum is highly variable, moving up or down with demand and production rates. To further complicate the matter production rates for all fossil fuels vary with demand and expected future prices, with the quantity of "recoverable reserves themselves depending on the expected future price.

70% of the electrical power in this country is derived from coal or natural gas, 22% from nuclear plants, 6% from dams & geothermal plants, and the rest from direct imports (Canadian hydropower) and renewables. The overall average thermodynamic efficiency of electrical power production & distribution in the country is 33%. You can readily verify this by consulting the U.S. Department of Energy, Energy Information Agency website (the last line in the table lists energy losses).

Using $.15/KwHr electrical power and $4.25/gal of gasoline as a cost factor, and the fact that 1 gallon of gasoline yields 36.6 KwHr of heat energy, that's equivalent to an energy equivalent gasoline price of about about $5.00/gallon - about 20% more than the avereage gasoline price in the USA today. Admittedly the efficiency of an electric car, including battery motor and mechanical losses, is about 75%, compared to about 33% for a compressed natural gas vehicle. However the government pressure, subsidies and mandated shares for renewable fuels are likely to raise electricity prices almost twofold in the very near future. Moreover the increased demand for electrricity to power vehicles (if it occurs, which I doubt) will further strain an already undercapitalized, over regulated industry, raising prices stillo further.

Bottom line - more fossil fuel useage will be required by a transition to electric vehicles than if we simply converted to CNG engines, and while there may be an initial operating cost savings, they are far less than the amnortized cost of the more expensive battery required. Furthermore their widespread use will significantly raise the price of the electrical energy it consumes.
raprap
 
  1  
Mon 13 Jun, 2011 01:54 pm
@georgeob1,
First I'm low and now I'm high.

Generally georgeob1 you're right back to where I started. 15 cents per kw-hr is equivalent to $5/gal gasoline for a heating value (100% energy equivalent @~20,000 BTU/lb & gas @~6lb/gal). So at 33% overall efficiency (including the second law) for an Otto cycle transportation is really equivalent to 45cents 14/0.33) per kw-hr.

Granted this is a rough calc, but it is good to within +/-25%.

Now for natural gas for a car/truck it either has to be held in a very high pressure tank or cryogenically. Either one presents safety hazards.

I'm not going to get into references for data as somehow I feel they're the same.

Rap
farmerman
 
  1  
Mon 13 Jun, 2011 02:55 pm
@raprap,
liquified gas doesnt burn until its re vaprozed, its easy to make robust storage tanks for propane or LNG. We have plenty of fleets that are propane or LNG powered. propane is just 2 more carbons per molecule
raprap
 
  1  
Mon 13 Jun, 2011 04:54 pm
@farmerman,
but those two little carbons have a hell of an effect on boiling point. LNG (liquified natural gas) is a lot colder.

For an interesting cosequence see LNG explosion Cleveland 1944

Rap
farmerman
 
  1  
Mon 13 Jun, 2011 05:07 pm
@raprap,
How many gasoline explosions have there been since 1944? Thousands? LNG or CHG are as safe (maybe safer) than gasoline. It doesnt pool, Actually diesel is more dangerous for car fires than gaasoline because gas evaporates before it can reach a flash point if it leaks on to a hot engine.

LNG is safer still.
georgeob1
 
  1  
Mon 13 Jun, 2011 10:34 pm
@raprap,
raprap wrote:
First I'm low and now I'm high.


I don't know why. My original contention - to which you objected with a diversion 0n current prices - was that running a conventional automobile with CNG as a fuel would involve lower consumption of fossil fuels or naturaL gas than would using that fuel to generate electricity, distribute it to a home, charge a battery that would drive a motor. I have demonstrated my point clearly.

Fossil fuel prices, particularly including gasoline and natural gas, are highly variable and change rapidly - and independently of each other.

Our electrical generating capacity was nearly at capacity before the economy contracted, and our distribution grid seriously lacking in redundancy and backup options. As the economy picks up and power demand rises we will soon be back to serious limits in capacity, with brownouts and all the rest. We need significant investment in both generating plants and more distribution networks. However the chokehold of expanded government regulatory activism is preventing both, just as it is limiting production of fuels. The EPA is working hard to shutdown our coal fired generating plants, and doing so without any feasible way to replace them. States, such as California and others that have established mandates for the production of about 20% of power by renewables will very soon see their rates rise by about 25% (since the utilities are required to charge prices based on the average cost of production). The financial economies you see now won't pay for the higher cost of the vehicle and will soon turn into negatives.
raprap
 
  1  
Mon 13 Jun, 2011 10:47 pm
@farmerman,
I'm sorry farmerman but on this I disagree-diesel is a combustible liquid, gasoline is a flammable liquid, LNG is a flammable gas, so is methane but tankage requirements are worse (very high pressure or cryogenic), hydrogen is an explosive gas.....as for the difference in incident frequency should be normalized to populations. How many gas tanks do you know of, vs methane tanks?

BTW one of the bitches I heard from responders over the years is spill control. With diesel (#2 fuel oil) you have spill control, with gasoline you control access and area, and pretty much let it burn.

I guess we can't reach a consensus all the time.

Rap
raprap
 
  1  
Mon 13 Jun, 2011 11:04 pm
@georgeob1,
It's been years since I've been involved with utilities. I understand that the present system is running on the same rails they were in 1990 and it is taxed by demand and reliability, and that coal power is where the locomotive was in 1948, in a rudimentary flux.

I also happen to know that most power plants have a design life of 25 years and are 50 years old . But your concern that electric vehicles are the camel breakers is IMHO bushwah. You're going to have to convince me.

Rap
0 Replies
 
raprap
 
  1  
Mon 13 Jun, 2011 11:18 pm
@georgeob1,
BTW georgeob1 I'm a strong advocate of the pumped storage solution to intermittent renewable power sources. And EPRI is doing some amazing things with batteries.

I'm also a believer in the unexpected--say something like a Johnnie Cab, consisting of your passenger container on a commercial, computer operated 24-7 skid pad. You get from place to place in your living room, faster than you do now.

Rap
farmerman
 
  1  
Tue 14 Jun, 2011 12:40 am
@raprap,
volatility is the reason that gasolime isnt as great a hazrd for engine fires. Thats a safety hint from the auto dealers.
No2 isnt diesell, diesel is a complex ester, not a fatty acid. You ave to remove the glycerine from no 2 to make diesel. You can probably burn no 2 in a diesel engine but its less chemically efficient because of the glycerine content.
georgeob1
 
  1  
Tue 14 Jun, 2011 09:44 am
@raprap,
raprap wrote:

BTW georgeob1 I'm a strong advocate of the pumped storage solution to intermittent renewable power sources. And EPRI is doing some amazing things with batteries.


I'm sure the utilities are grateful for your support. Pumped storage has been in widespread use for over sixty years now. The conventional hydroelectric option enables the recovery of about 50% of excess electrical energy used to pump water up the dam. Other, largely untested options, including compressing inert gasses into geologic voids and recovering the energy through turbines, are being exploired as well. Some promise recovery fractions as high as 60%, but that's about it.

The average capacity factor of land based wind turbines is about 27% - that means if you install (say) 10 MW of turbine capacity you get only 2.7MW of power 24/7., whereas with nuclear you get 9.2 MW (based on the average performance of our 100 or so nuclear plants over the past ten years).

Taken together the storable power output of renewable power sources is a rather pathetically small fraction of the installed capacity.

I know EPRI very well, as I suspect does farmerman. My company does a lot of business with them. They are an industry funded research institute - generally better than their government counterparts, but like them primarily interested in self preservation and promotion. I haven't yet see them do anything fast.

Improvements in battery technology are indeed being made, bit most consist in marginal improvements in the capacity and reliability of current lithium batteries. Hysteresis, cost, and reliability remain limiting factors. No order of magnitude breakthroughs are likely any time soon.
Walter Hinteler
 
  1  
Tue 14 Jun, 2011 11:56 am
@georgeob1,
georgeob1 wrote:
Pumped storage has been in widespread use for over sixty years now.


The oldest, still working pumped-storage power plants (ten, if I counted correctly) are between 78 and 86 years old. (The first full-scale pumped-storage power plant in Germany had two 30-MW sets and was completed in 1930.)


0 Replies
 
raprap
 
  1  
Tue 14 Jun, 2011 12:04 pm
@georgeob1,
If I remember an exercise on wind turbines they are theoretically capable of extracting a maximum of 69% of the energy from the wind (that ugly 2nd law again).

And the 9,2mw for nuclear power is 92% availability, I assume. If so that pretty good considering that most of the nuclear plants are more than 30 years old.

Years ago I remember something about off peak power balancing--that is space and water heating systems being controlled by the generators and distributors such that they'd have the capacity to even the demand nearer to the capacity. Is this still being done?

Rap
georgeob1
 
  1  
Tue 14 Jun, 2011 01:01 pm
@raprap,
I don't know about the 69% numbere. I assume it refers to the fraction of the kinetic energy passing through the rotor disc: if so that is generally compatable with the aerodynamic efficiency of a helicopter or autogyro rotor. Propellers and subsonic aerodynamics have been around for a long time. Additional breakthroughs aren't likely.

The 27% capacity factor for wind turbines is a consequence of typical variations in wind speed and direction. The wind turbine must be built to withstand the highest local winds, and that involves attaching a turbine able to extract the energy at high wind speeds (just to keep the rotor from failing). The result is the installed capacity is necessarily biased towards the 90th percentile wind speed, while average power production is based on the average wind speed. Since the available energy is a function of the square of the wind speed, the difference is considerable. The best modern offshore wind turbines in the North Sea get capacity factors of about 32%, but on land 27% is generally the best you can do, and most do less than that.

If you include capacity factor the capital cost per MW output of wind turbines is almost twice that of nuclear plants. (There's a lot of concrete in the foundation of a 300ft tall, 300 ft rotor diameter wind turbine.)

The capacity factors of nuclear plants are limited only by outages for refuelling and maintenance. Nuclear fuel is a good deal cheaper (and less environmentally harmful) than coal so the utilities generally throttle back on the coal plants at night and keep the nuclear plants running at 100% 24/7. Thus coal fired plants average capacity factors of about 78%, while the nukes get 92%. Prior to 1980, in the early years, the nuclear plants didn't do as well - there was a learning curve involved there for both the utilities and the regulators.

Even at today's low natural gas prices, electrical power from nuclear plants is a lot cheaper than that from coal or gas powered plants - and they are less than half the cost of wind or
parados
 
  1  
Thu 16 Jun, 2011 07:49 am
@georgeob1,
But wind is a whole lot cheaper than nuclear fuel.

And this brings up your earlier argument about how the infrastructure can't handle an increase caused by electric cars.
Most of the current electricity is used during the day.
Most electric cars will be charged at night when there is excess capacity which currently causes reductions in electrical production at those times.
georgeob1
 
  1  
Thu 16 Jun, 2011 08:31 am
@parados,
Wind is free, but operating a wind farm is quite expensive. Lots of land & power transmission from individual turbines involved. It ain't easy or cheap to do maintenance of a 5 MW generator atop a 300 foot tower in an open field.) I have also noted the very large differences in Capital costs per MW delivered - data from the DOE Energy Information Agency website - a cost that is amortized over the life of the turbine (or nuclear plant).

I agree that there is extra generation capacity at light and that things like smart grids and differential rates could squeeze out added effective capacity from our existing power sources. However our transportation system consumes an amount of energy roughly equal to 40% of total electrical generation, and there isn't enough reserve capacity to meet even a large fraction of that. Solar power doesn't work at night and wind has an even lower nightime capacity factor than in the day, so they won't help much.

Power consumption follows economic activity fairly closely, and our demand is down right now with a very depressed economy. However, when it comes back we will very quickly find ourself dangeously close to the limits of our generation & transmission systems, and subject to cascading failures & interruptions. It takes years just to get environmental permits for new powerplants and more years to build them. We already face a critical situation, even without any new sources of demand.
 

 
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