# Tag Info

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Electricity production optimization is a very complex subject. It is also affected by many parameters , which I will try to outline below. TL;DR: Demand is constantly monitored and supply is constantly adjusted TL;DR 2: Lshaver's excellent post is a suggested reading after reading this, because it expands and explains what happens at timescales ranging from ...

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Timescales on the grid Power demand fluctations can be broken into timescales from micro-seconds to decades. On the "decades" end of the scale, the power industry and utility regulators work together to plan and fund construction of power plants and the associated transmission and distribution infrastructure. When you turn your air conditioner off ...

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Thermodynamic efficiency vs. fuel economy When you cite an efficiency of 25-30% for an internal combustion energy, you're talking about the thermodynamic efficiency of the engine. This is, at the theoretical level, based on a temperature differential. It has nothing directly to do with the fuel. When you cite a fuel economy of 34 miles per gallon, you're now ...

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There are certainly a few reasons why acetylene is not a very practical fuel for an IC engine. Perhaps the most important is that it is inherently unstable and tends to explode under pressure, this makes it much more difficulty to store as it must be dissolved in acetone in an inert matrix, unlike say propane which can just be liquefied. This means that ...

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Yes, they monitor demand and due to differences in how different power stations are controlled they can increase or reduce output to match demand. Some power plants like nuclear run at full output as they are slow to change, but others like Dinorwig (in the UK) can go from standby to max output in 12 seconds and reduce to half quickly. Danish researchers did ...

7

Note: This is specific to gasoline based engines. Assuming your car was produced after the ~1990's it is equipped with a Deceleration Fuel Cut-Off (DFCO) system which cuts the fuel flow to the engine when the gas pedal is not depressed and the car is in gear. In this case it is more fuel efficient to stay in gear because you are letting gravity run the ...

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The plot in the question does not apply to the situation being asked. The power capacity of an automotive engine is dynamically changed while driving by both altering the RPM and by throttling the airflow in the intake. The peak efficiency of a car engine is somewhere midrange, with inefficiencies under both high and low loadings. At 10% loading, the ...

6

Peak Demand One of the biggest issues in the electricity business is managing peak demand. This is the maximum amount of electricity needed at any one time. Typically this will be the middle of the day on the hottest days in the summer, as that combines household usage (everyone is awake), office usage (everyone is at work, or at least before the pandemic...)...

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TL;DR: the MM in MMtoe is probably related to the Latin Numeral M (for 1000). In that context MM means one thousand thousands (i.e. one million) Although this is very confusing, the bottom line is that to (my understanding) $$1 \text{ MMtoe} = 1 \text{ Mtoe} = 10^6\text{ toe}$$ Where: 1 toe = 11.63 megawatt-hours (MWh) 1 Mtoe = 1 MMtoe= 11.63 terawatt-...

5

In a modern car with electronic engine control, fuel injection, etc, the amount of engine power is always dependent on what the ECU is doing in response to the driver's control inputs like throttle position, brake pressure, etc. If the ECU also knows what gear you are in, it is straightforward to calculate whether you could produce the same amount of power ...

4

You probably want to look at stochiometric ratios by mass. However this is a difficult problem to solve from first principals as for an IC engine air is essentially free and monitoring its consumption in bulk is not a major priority. I suspect at the mistake you have made is confusing mass ratios with volume ratios. As air is a gas and as such has very ...

4

The answer depends a great deal on the control system around the engine, and how fast you are going down the hill relative to the gear you are in. For a basic engine system, like 1960s or earlier, at idle throttle setting the fuel usage would go up a bit with engine speed. The higher engine speed would make a higher vacuum, which would pull in more fuel-...

3

Consider to simplify the model to two wheels in line as in a bicycle. For nice round figures, the tires are inflated to 100 pounds per square inch. The load is two hundred pounds and is placed over the rear tire in such a way as to fully load the rear axle and completely unload the front. The footprint of the rear tire is now two square inches. In order ...

3

The difference is in the drag coefficient. Typical drag coefficient of the 50's cars have been in the range of 0.38 to 0.42 or so. typical drag coefficient of modern cars even the ones not renowned for their streamlined body is ranging from 0.26 to 0.34. drag is the retarding force exerted on moving bodies by the media they are moving in. it tries to slow ...

3

Petrol engines have a very poor efficiency at low load... no ifs or buts. The 34mpg efficiency is not quoted at low load. There is an ideal speed at which maximum mileage occurs... engine efficiency increases as load increases, however, air drag losses increase as the square of the speed. There are two major reasons for the poor efficiently at low load: ...

3

I know it's an old thread, but I can't resist taking a stab at it. Especially when there's so much bad or unrelated info in the other answers. Thermal efficiency and fuel mileage ARE related - there are other factors to consider though. Fuel energy density is a factor. For gasoline engines it's about 44.5 HP-hours (since mpg occurs over some time and ...

3

I can give you an analogy: For a DC electric motor, efficiency is highest at a point LESS THAN its maximum rated power. The loss mechanisms are friction from fast rotation, and magnetic core losses (current going through the iron alloy) as a torque-independent parameter. If it weren't for magnetic losses, the efficiency would be maximum at torque=0. So ...

2

Rephrasing your question: 1. How much energy does a car use at 60mph doing 34mpg? 2. What is its efficiency if it requires 20hp to maintain constant speed? In SI units: Car at 26.8m/s doing 14.4km/L requires 14.9kW Empirical data: * HHV for gasoline approx 47MJ/Kg * Density of gasoline approx 0.74 Kg/L => ~ 35MJ/L Calculations: PowerIn = (...

2

Bear in in mind that the chart shown relates to the thermal efficiency of the engine alone and doesn't consider a moving car as a complete system and also that the vertical axis appears to be labeled as a ratio rather than a percentage efficiency so 0.2 on the graph is equivalent to 20% For a car as a whole, engine load is not independent of speed as drag ...

2

In your scenarios, there are two places that the energy ends up: as kinetic energy in the vehicles themselves (0.5 × mass × velocity squared) and as losses (rolling resistance, air resistance, etc.). There are two possibilities regarding your two scenarios. The two scenarios occur in the same amount of time. This means that the total energy is ...

1

Some engine manufacturers use BSFC which is the fuel consumption compared to the power produced. As you know the engines you want to look at you should be able to get the figures.

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It's more than possible. The 2020 Toyota Prius already claims it with 58 on the highway and 56 combined highway and city. The limit is higher. Here is an article that covers a lot of details

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Your range of "gasoline to sunflower oil" (in a comment) is too small. Turbine engines run very well on natural gas, when used for gas pumping applications. Combustion is continuous, so auto-ignition and flash point are not very relevant except for light-up, and you can use a different fuel for that if need be. The only real limitation is clean burning. ...

1

IF I understand your question, you're asking why we need a main metering system with any moving parts. It sounds like your assumption is that, as the throttle is opened, the increased airflow should pull a commensurately larger volume of fuel through the jet to keep the mixture correct. In a rough sense, that's true, but... That passage is a limiting factor, ...

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Use the fuel specified by the manufacturer in the car's manual and/or near the gas cap. Likely a High Octane Fuel based on your question. If you're referring to Octane levels... The higher the Octane, the harder it is to ignite the fuel. In the case of High Compression Engines(typically in sports cars like you mention in your question) lower octane fuel can ...

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Due to the dangers involved with storing and transporting compressed or liquid acetylene, you would probably have to make use of an onboard acetylene generator, fueled with calcium carbide. Acetylene generators are safe, but generally produce hot gas, which reduces specific power, and has a tendency towards preignition and even backfiring. So, it can be ...

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That chart is suspect. If you look at the Web page it was taken from, it is clear that the author of that page does not understand the basic terms that he is using, like "load", "power", "torque", etc. The chart may be correct if we interpret "load" as "torque", as it is well known that engine efficiency improves as torque increases and spin decreases (...

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