Brad Ideas - Two sources on energy, and using heat - Comments

I had an argument with the

Chris Cooper — Mon, 19 Jul 2010 04:01:35 -0700

I had an argument with the salesperson when i decided to buy some more contemporary radiators, for an extension to my house. He tried to convince me that they were more efficient than standard radiators!!

Energy thoughts

DaveC — Mon, 25 May 2009 21:01:44 -0700

I read most but not all of MacKay's book, missing the section on cars. Excellent point about electric car's energy uses. MacKay is very concerned about "carbon footprint." A critical error not to count the fossil fuel use to make electricity for an electric car.

Where I live, electricity is about 80% from coal, 10% natural gas, 4% hydro, others minimal. Although the utilities are building mostly new gas turbine generation plants, gas is still a pretty expensive way to make electricity. Residential microturbines, especially with a mechanical linkage to the air conditioner are intriguing. I suspect they won't be competitive in the current market, because the turbines wouldn't have enough operating time to justify the capital expense. Interesting question how the economics would change with increasing fossil fuel prices. Free market resource consumption economy prevailing, I bet centralized coal fired electrical generation blocks out residential gas microturbines for decades to come.

Although it doesn't seem politically viable, IMHO the logical public policy approach is an increasing coal extraction task at the mine. You pretty much nailed the issue with subsidizing residential PV.

Great post, deserves wide reading.

Overhead power

brad — Sat, 09 May 2009 07:10:16 -0700

Cars may need two wires (like a trolley bus) which is more complex, and has many other issues. Plus you can only go where the wires are — or you need batteries or an engine anyway. You get wires ruining the look of the streets, unless one can design a safe ground based power system, which is hard to do to work in the rain and deliver all that current.

Lots of power means high voltage, and fire risks.

What about powering the car off the grid

Ed — Sat, 09 May 2009 03:51:56 -0700

As you pointed out above with hybrids you lose a fair amount of energy just converting it from gasoline into electric power. Additionally, the bigger the battery you put in the car to extend its range in the electric mode, the heavier it is to move the car around. In San Francisco, some of the bus lines are powered by overhead electric wires. I was wondering about extending that overhead grid and using it to power bumper car style cars (cars powered off overhead wires). It seems like that would remove a lot of weight from the cars, you wouldn't need to use electricity to push either batteries or gasoline around, so you could probably get by with a smaller engine. Also you would be drawing power directly off the grid using what ever local clean power is cheapest (hydro, solar, wind, geothermal or nukes). The bumper cars at Great America were pretty light, but I have no idea how fast they went.

Two sources on energy, and using heat

brad — Thu, 07 May 2009 13:04:16 -0700

I was reminded yesterday, after posting more on the cost-effectiveness of energy sources, to point out an interesting new book on the economics of energy. The book is Sustainable Energy With the Hot Air by David MacKay, a physics professor from Cambridge University. What’s important about the book is that he pays hard attention to the numbers, and demonstrates that certain types of alternative energy are likely to never make sense, while others are more promising.

I only have a few faults to pick with the book, and he’s not unaware of them. He decides to express energy in the odd unit of “kilowatt-hours per day” as he feels this will make numbers more manageable to the reader. Of course with time in the numerator and denominator, it’s a bit strange to the scientist in me. (It’s the same as about 42 watts.) In a world where we often see people say “kilowatt” when they mean “kilowatt-hour” I suppose one deserves credit for using a correct, if strange unit.

My real quibble is over his decision to measure energy usage at the tank, so that an electric car’s energy usage is measured in the battery, while a gasoline car is measured in the fuel tank. Today we burn fuel to make electricity, and so electric cars actually consume 3 times the energy they put in the batteries. That’s a big factor. MacKay argues that since future energy sources (such as solar) might generate electricity without burning fuel, that this is a fair way to look at it. This is indeed possible but I think it is necessary to look at it both ways — how efficient the vehicles are today (and will be if we still generate electricity from heat) and how they might be in the future. Generating electricity from heat does complicate the math of energy in ways that people can’t agree on, so I understand his temptation.

Yesterday I was also pointed out to a solar power site called SolarBuzz. This is a pro-solar-panel site, and is rare in that it seems to do its math right. I haven’t looked at all the numbers, and I am surprised wthat with the numbers they show that they are such boosters. Their charts of payback times all focus on power costs from 20 to 50 cents/kwh. Those costs are found in Europe, and in the tiers of California, but the U.S. national average is closer to 10 cents, where there is no payback. They also use 5% for their interest rate, a low rate that is only found in strange economic times such as these — but justifiable in a chart today.

Brad Ideas - Two sources on energy, and using heat - Comments

I had an argument with the

Energy thoughts

Overhead power

What about powering the car off the grid

Two sources on energy, and using heat

Pure heating is highly wasteful