Lecture V

Physics 367

Production and Distribution of Electrical Energy



Energy is used for many different purposes:

to heat ourselves,
to cool ourselves,
to cook,
to move from one place to another.

Where does this energy come from?

US Energy Sources


Energy may be deployed in a number of ways or end uses.

US Energy End Uses

Electricity

is generated from our natural resources.
is central to our national energy policy.

we must discuss both production and end use.


Production of Electricity

it costs 3kWh of energy from fossil fuels [thermal energy] to produce 1kWh of electric energy.

it costs 1kWh of energy from hydro or photovoltaic sources to produce 1kWh of electric energy.

there are two units kWhe and kWht which may be chosen to report energy.


Accounting

Plants built for generation of electricity from fossil fuels or coal are among the most concentrated sources of water and air pollution.

As we saw yesterday, burning

100 kilograms of coal per second,

produces about

  15 kilograms of ash per second,
    5 kilograms of sulfur dioxide per second,
300 kilograms of flue gases per second.

We need some way to account for this
We must discuss efficiency


End Use

Space heat is the single largest end use in

the residential and
commercial sectors.

Conservation measures here will make a difference.


Other end uses in the residential sector include:

space heat
water heat
cooking
refrigeration
air conditioning

Our lives would not be the same without electricity.

Air conditioning helped settle the Sunbelt!


 Ohio's Greatest Home Newspaper
dispatch logo
                    Sunday, October 4, 1998



Wind turbines twirl on the hills above Mojave, Calif. California is the birthplace of wind power in the United States and the first state to let customers pick the source of their electricity. Choices also include solar and geothermal.

Click here for a picture of wind turbines.


Clean power attracting customers in California

State becomes first to offer a choice of energy sources

Sunday, October 4, 1998

Martha Bellisie
Associated Press

TEHACHAPI, Calif. -- The three-bladed propellers play an eerie wind waltz - a steady whoosh, whoosh, whoosh - as the persistent breeze blows.

The sleek, angular towers, reaching up to 140 feet, stand like sentries guarding the grassy hillsides that lead to California's high desert.

``To me, they look like giiant toy pinwheels flickering in the afternoon sun,'' said Geraldine Veatch, who lives just west of Tehachapi Pass, where more than 4,900 wind turbines spin out enough energy anually to power 250,000 homes.

``Some say they're an eyesore. But I'd rather have wind turbines than nuclear power plants.''

California is the birthplace of wind power in the United States. It's also the first state to let consumers choose the source of the electricity they use. Now the rest of the country is watching to see how wind farms and other pollution-free, or ``renewable,'' energy producers fare in a competive marketplace.

Power sources considered renewable include wind, solar, geothermal, biomass (electricity produced by burning garbage) and small hydroelectric plants (which don't significantly impact wildlife and water).

Before March 31, a handful of utilities held a monopoly on the state's $20 billion power industry. The system made sense, given the high cost of producing and transmitting electricity and the need for reliable electricity in this energy-dependent age.

But California's deregulation legistration, passed in 1997, opened the market in the same way the airlines and long-distance phone industries were restructured.

``Deregulation actually doesn't have anything to do with the flow of electricity, it has to do with the flow of money,'' said Rich Ferguson, spokesman with the Sacramento-based Center for Energy Efficiency and Renewable Technologies.

``You used to have to give all your money to the monopoly utility. Now you can choose an independent supplier.''

Whether consumers will use their buying power to demand lower prices or whether they'll be willing to actually pay more for nonpolluting choices of electricity genreation are unanswered questions.

About 69,000 residential customers have switched their power providers from utilities to independent suppliers since the program started late last year, according to California Energy Commission spokeswoman Claudia Chandler.

But the utility industry is not yet able to determine how many of those customers chose renewable power sources, Chandler said.

Ferguson said the majority were likely green switches.

``It's the biggest factor in the competitive market,'' he said. ``Prices aren't a strong marketing factor at this point.''

Several high-profile companies have gone green.

Patagonia, a Venture-based outdoor clothing company, announced recently that it has committed to using 100 percent wind energy to power its 14 California facilities.

``We decided, as a company, to participate in eliminating, or reducing the dirty power that's on the grid by replacing it with clean power,'' said Patagonia spokeswoman Lu Setnicka.

But the company won't be going off the grid and running power lines direct to wind turbines. Instead, it has contracted to buy its electricity from Enron Energy Services. Enron is building a 16-megawatt wind farm near Palm Springs to accomodate the contract.

Toyota Motor Sales also committed to using a mix of renewables - including wind ,solar and geothermal - to power its Torrance and Irvine headquarters. The division also is working on switching over to renewable energy at its Long Beach docking facility and an auto parts supply facility.

California electric customers can call an independent power source and choose from a variety of packages.

For instance for an extra $7.45 to $16.90 a month, consumers can choose a package from Southern California Edison's Earthsource 50 or 100 programs, offering power that is either 50 percent or 100 percent from renewable sources.


Electricity Needs are defined in terms of load:

Base load
Intermediate load
Peak load

See Energy Figure 6.3


Base load is the most economical for a utility to supply. Base load (~50%) is generated all day....always running....maintenance proceeds continuously. The largest generating plants are designed for base load production. The hardest plants to turn on are also dedicated for base load production.

See Energy Figure 6.5, 6.8


Economy of scale: Bigger is cheaper?

Surface area goes as r2, but volume goes as r3. If the cost goes as the surface area

the bigger the building the cheaper the usable space

But bigger costs more to get started. The result is that most utilities use a mixture of generating facilities to satisfy demand.

See Energy Figure 6.5, 6.8


What to do Next?

How should we approach the future needs of electrical energy?

build more plants
build larger plants
co-generate electricity
use renewable sources
increase efficiency
cut transmission losses
...


Problem of the day

A population of cows on a farm is in steady state. The birth rate is 7 calves per year and the average residence time for a cow on the farm is 6 years. How large is the herd?

When the flow of a substance into a herd, lake, atmosphere or other box is equal to the outflow of the substance, then the amount or stock of that substance in the box will be constant. This is called a steady state or equilibrium. In this condition the ratio of the stock in the box to the flow rate (in or out) is called the residence time.

Thus if Fin is the rate of inflow to the box and Fout is the rate of outflow, the steady state condition is:

Fin = Fout

Letting M be the stock and T be the residence time then

M/Fin = M/Fout = T


Solution:

What do we know?

The residence time, T, is 6 years
The inflow, Fin, is 7 calves/year

The stock, or how large the herd is, M is unknown

so:

M/Fin = T

or

M = T x Fin

M = 6 yrs x 7 cows/yr = 42 cows