Transmission and Distribution Losses in the US Estimated at 7.2% in 1995

[Wilms]

I've been pondering increased local solar/wind electrical generation as one means to ease our reliance on conventional methods of production.

I considered the more local the generation, the less line-loss was incurred. And so I wonder what percentage of our electrical generation goes to I²R losses.

Googled offered Wikipedia which offered this link which answered an additional question I had. Does the amount of I²R loss increase as system load is increased?

You Ohm's lawyers already knew.

Energy losses in the U.S. T&D system were 7.2% in 1995, accounting for 2.5 quads of primary energy and
36.5 MtC. Losses are divided such that about 60% are from lines and 40% are from transformers (most of
which are for distribution).

Technologies that can improve efficiency and reduce carbon emissions are high-voltage DC (HVDC) transmission,
high-strength composite overhead conductors, and power transformers and underground cables that use
high-temperature superconductors (see related technology profile).

High-efficiency conventional transformers also could have significant impacts on distribution system losses. In
addition, energy storage and real-time system monitoring and control systems could improve system reliability
and customer access to competitive generation, including renewable power producers.

There is no active U.S. program for HVDC development or improved distribution transformer technologies.

http://climatetechnology.gov/library/2003/tech-options/tech-options-1-3-2.pdf

Is this an underappreciated advantage to solar/wind generation. Especially for rural service?


On the other hand, this British gov paper suggest that as more unreliable sources (namely, wind) are added to the grid the more expensive it becomes to operate.

It went over my head, but I could sort of imagine.

QUANTIFYING THE SYSTEM COSTS OF ADDITIONAL RENEWABLES IN 2020
http://www.dti.gov.uk/energy/developep/080scar_report_v2_0.pdf


Anyone here know about this stuff?

[Dogmudgeon]

1. Superconductivity is one proposed solution

But so-called "room temperature superconductivity" is a long way off, unless you consider -200C a comfortable room temperature!

However, some of the problems are problems of perspective -- for instance, the use of the word "unreliable" rather than "intermittent". Just a change in the way a problem is described can open up whole new ways of solving it. If wind/solar/tidal and other renewable, intermittent energy sources are to succeed, we will simply have to improve support for them; e.g., local grids ("intra-grids" on the "Intergrid") and new methods of storing energy.

This is also a reason why I support nuclear power. I don't think we can build enough renewable energy infrastructure fast enough to prevent disaster. In 1970, when we first became aware of this situation, we thought we had about 30 years. It would have been effortless to develop renewables, but they were laughed into obscurity. It would have been possible to make nuclear energy much safer, but the industry got caught in a political whipsaw of its own making. Today, we have ten years or less, even with the successful power-down of the late 1970s. We will need to not only provide power to residences, but to entire industrial and agricultural worlds that demand far more energy than collected our personal needs. Food, for example, requires between three and ten calories of energy to produce one calorie of nutrition. (These are usually calculated as kilocalories, or kCal.) And with all due respect to the vegetarians, eliminating animal husbandry won't change that calculus very much.

The most likely -- logical -- outcome is disaster.

I hope I'm wrong about the entire picture. A couple of breakthroughs and some enlightened planning, and we'll make it over the hump. But, sadly, we can depend on neither.

--p!

[Wilms]

4. "but they were laughed into obscurity"

:cry::grr:

[Buck Turgidson]

2. Line losses are proportional to system load.

Most of the line losses are due to resistance heating as shown by your I-squared-R relationship. Distant generation => Longer transmission lines => More resistance. For a given transmission line, Greater load => More current (I) => More losses.

One way of reducing transmission line losses is to raise the voltage. Think V=IxR. For a given transmission line, if Resistance is constant, Higher Voltage (V) => Lower current (I) => Lower losses.

Another way to reduce losses is to reduce the resistance. There have been some advances in superconducting (R=zero) transmission lines.

So, you are on target. The most efficient electrical system would be a local generator producing electrical energy on demand at load voltage levels. Power companies refer to this as distributed generation. Essentially get rid of the transmission system, get rid of the voltage transformation and get rid of voltage rectification (AC-DC conversion).

Some options besides solar/wind for local generation:

1. Micro-turbines -- A box in the backyard that runs on natural gas or propane.
2. Fuel cells -- A box in the backyard that runs on natural gas or propane.

In any case, distributed generation potentially implies that no grid is required. Every household is it's own little, unconnected electrical system. You still have to ask the question, is that more or less reliable than a conventional grid? Probably depends on your location where rural customers are subject to power outages from wind/trees/ice, etc.

[Wilms]

5. Thanks for the help. n/t

[skids]

3. That's nothing....

...Look at the amount of heat we throw away (into local ecosystems that don't handle it well) generating the electricity in the first place. That's where the big energy loss is, and it's why CHP units are an attractive technology -- heating water and doing cooling/heating with the waste heat.

As far as whether home generation solves that problem -- no, not really. Despite the 7-8% lost in transmission and distribution, those large systems are still a heck of a lot more efficient than a lot of small systems. Converting the power from your windmill or panels into socket power, or feeding it back to the grid, or throwing in into/out of batteries, or DC level adjustments all take their "tax" out of your home system and the accumulate can easily add up to more than 7-8%.

If every off-the-gridder ran most of their appliances off of DC power of the same voltage emitted by their generator, and those appliances were engineered for efficient use of DC, and they had super-efficient ultracapacitor storage then we could see a savings in this area, but as it is it's the source/independent control of the off-the-grid solutions that is attractive, not any efficiency gain.

[Wilms]

6. Thanks for the interesting points.

I can imagine the efficiency on the generation end is lackluster, and even more so for small scale operations.

But the common solution for generation, as well as transmission and distribution ineffeciencies is to generate more power. Seems a bigger PV panel, or a bigger windmill, is preferable to a bigger coal/nuke/gas generator. Is that correct or did I leave out a varible?

[skids]

7. Actually CHP efficiency is pretty high...

...some of the new small cogen appliances are at least as efficient as some of the power plants still in service.

But yes, adding wind and wave, and eventually solar when the producers get off their butts and manufacture something at the right price point, is much preferable. Small distributed projects may not save anything
on T&D waste, by the way, but they do have another advantage: redundancy, route diversity, and robustness.