CHAPTER 1 ENERGY SOURCES

1A. Forms of Energy

Energy may be described as "the ability to produce heat". Power is the rate of energy flow from one place or form to another. If no energy flows across the boundaries of a given region (an "isolated system"), then the total amount of energy inside remains constant, although many forms of energy may be present, in varying amounts. Some forms of energy are listed in Table lA1, and units of energy are described in Appendix A. Strictly speaking, energy is not "the ability to do work", since thermal energy cannot be fully converted into work.

lB, Energy Demand energy uses

Energy is needed in food production, transportation, communication, heating and cooling buildings, materials processing and manufacturing, and virtually all aspects of modern life. The distribution of energy usage in the United States is illustrated in Table lB1.

The historical growth of energy input to the food system and of food energy consumed in the United States are shown in Fig. 1Bl. More and more energy input is needed per calorie of food produced, as we attempt to grow food on arid lands, replenish exhausted soil nutrients, etc.

Great amounts of energy are needed to produce materials, such as lumber, cement, metals, and plastics, for construction and industry. The energy required to produce one kilogram of various materials is shown in Table 182, along with the fraction of the product price which is due to energy cost. As ores become scarce and depleted, more energy must be expended for mining, refining, and pro- cessing. Recycling of scarce materials also demands more energy consumption, for separation, transportation, and processing of materials.

relation to standard of living

The gross national product (GNP) per capita is one measure of the "standard of living" in a country. The relationship between the GNP per capita and the energy consumption per capita for various countries is shown in Fig. lB2.

1

2 lA, Forms of Energy

TabZe ZAZ. Some forms of energy (mks units) .

form definition variables

rest-mass energy = mOc2 m0 = particle rest mass (kg) (IAl) C = speed of light (m/s)

kinetic energy = mc2-m0c2 m = relativistic mass of (IA21 particle (kg)

kinetic energy = mv2/2 m = mass (kg) (lA3) (nonrelativistic

case) V = speed (m/s) << c

electrostatic = q 1q2/4mzOr ql,q2= charges (C) (lA4) potential energy EO = permi ttivi ty of free space of 2 point charges (F/m)

r = distance between the charges

T (ml

thermal energy = m / dT Cm m = mass (kg) (lA5) 0

‘rn = heat capacity (J/kg-K)

T = temperature (K)

potential energy = Gmlm2/r G = constant (J-m/kg2) hw of gravitation ml ?m2 = masses (kg)

r = distance between the masses (m)

potential energy = kx2/2 k = spring constant (J/m2) (lA7) of spring X = extension of spring (m)

work = Id;; dz = differential path length ww + (ml

F = force (N)

rotational kinetic = Itl?/2 I = moment of inertia (Js2) (IA91 energy w = angular speed (t-ad/s)

electric field = /d;: cE2/2 E = electric field (V/m) dz = differential volume (m3)

(1AlO) energy

vo 1 ume E = permittivity of the

material (F/m)

magnetic field energy

= /d;: B2/2p

vo 1 ume

B = magnetic induction (T) (lAl1) 1-I = permeability of medium

(H/m)

energy stored in capacitor

energy stored in inductance

= c@/2

= LIZ/2

= capacitance (F) (lAl2) 5 = voltage (V)

L = inductance (H) (lAl3) I = current (A)

lB, Energy Demand 3

TabZe ZBI. Distribution of energy usage in the United States, 1968. From Stanford Research Institute, Patterns of Energy Consumption in the United States, U.S. Government Printing Office, Washington, 1972. industrial

primary metals chemicals petroleum refining food and related products

paw stone, clay, glass, concrete other

percent

8.7

E:: 2.2 2.1 2.1

13.3 41.2

TabZe lB2. TypicaZ energy contents of materiak and manufactured pro- ducts. The actual values of a given product may vary considerably from these values, From The Technology of efficient Energy Utilization, NATO Science Conunittee Conference (1973). Reprints avaiZabZe from Pergamon Press

ratio of energy energy cost input to value of (MJ/kg) product

transportation

gas01 ine jet fuel distillate and res raw materials other

idual fuel

17.1

;:;

0.3 1.2

25.2

comme rc i a 1

steel 25-30 0.3 copper 25-30 0.05 aluminum 60-270 0.4 magnes i urn 80-100 0.1 glass

(bottles) 30-50 0.3 plastic 10 0.04 paper 25 0.3 inorganic

chemicals (average) 12 0.2

cement 0.5 1 umber z 0.1

space heating air conditioning asphalt and road oils water heating refrigeration other

residential

space heating water heating refrigeration cooking other

6.9 1.8 1.6 1.1 1.1

ii+

11.0 2.9 1.1 1.1

2.4 19.2

Fig. lB1. Annual energy input to United States food system and annua2 food energy consumed in the United States for the ;;er;od 1940-1970. 1 ExaJoule (EJ) =

J. 1 EJ/year = 31.7 GW. Adapted from ENERGY: SOURCES, USE, AND RODE IN HUMAN AFFAIRS, by CaroZ E. Steinhart and John S. Steinhart. @ 1974 by Wadsworth Publishing Company, Inc. Reprinted by permission of Wadsworth Publishing Company, Belmont, California, 94002.

10

0

annual food energy consumed

a. ' I . I 1940 1950 1960 1970 1980

4 lC, Energy Sources

10 Fig. lB2. Gross nationa; product per capita vs. per-capita energy consumption rates for various countries, 2977-78 data. AC = Argentina, AL = Australia, AU = Austria, BR = Brazil, CA = Canada,

z

CH = China, CZ = CzechosZovakia, EG = &

East Germany, FR = France, GR = Greece, mO -

HU = Hungary, ID = Indonesia, IN = India, . 1 IR = Iran, IT = Italy, JA = Japan, MX = z Mexico, PK = Pakistan, SA = South Africa, q SK = South Korea, SP = Spain, SW = ik Sweden, SZ = Switzerland, TU = Turkey, 0 UK = United Kingdom, UR = USSR, US = USA, WC = West Germang.

predictions of demand O-t

The total energy consumption rate of the world P, may be written as the sum of

L I.1

sz SW ’ FRWG ‘#

JAAU ’ AL

, UK EG

/ SK /

/ CH /

/ IO /

PK IN

/ I 1 1

KW/CAP 10

the energy consumption rates of the various geographical regions:

pW = “k NkPk

(Watts) (1Bl)

where Nk is the population of region k and pk is the average per-capita energy

consumption rate of that region (W/person). Both Nk and pk are increasing in almost every region of the world.

Estimates of the growth of populations and per-capita energy consumption rates for various geographical regions from 1975 to 2025 are shown in Table 183. The uncertainty in the 31 TW total is about + 30%. (1 TW = 1012 W). Similarly, the world energy demands in 2000 and 2050 are estimated to be around 18 TW and 50 TW. World energy production rates must be greatly expanded to supply these needs, especially in developing nations.

lC, Energy Sources power flows

Renewable energy sources, such as solar, geothermal, biomass, hydroelectric, wind, wave, and tidal power, are limited by the usable power they provide. Non- renewable fossil and nuclear fuels are limited by the total amount of energy they can provide.

About 178,000 TW of solar energy are incident on the earth, of which various amounts are reflected, reradiated, absorbed by evaporation and flow into wind, waves, and photosynthesis (Fig. 1Cl). Geothermal heat flow and tidal power add about 35 TW to the balance. Although the solar and geothermal power flows are large, the useful fractions are small.

The rate of consumption of fossil fuels is limited by availability, transpor- tation facilities, and environmental impact. An estimate of the complete cycle of world petroleum production is shown in Fig. lC2. Production will probably decline after the year 2000. The restrictions of fossil fuel consumption necessary to

lC, Energy Sources 5

TabZe lB3. Ccwparison of popuZations,per-capita power demands, and total power demands in 1975 and estimated for 2025. Fra R. M. Rotty, %mstraints on fossi fueZ use", Interactions of Energy and CZimate, Bach, Pankrath and WiZZioms, editors, ReideZ PubZishing Co., 1980; and R. M. Rotty, Energy & 881-890 (1979).

populations Nk pk total power demands Nkpk (TW = 1012 W)

REGION (millions) 1975 2025

( :hg;l;mal k,l;l:c,w 1 growth 1975 2025 ratio --- - ---

N. America 237 315 11.5 15.0 2.72 4.74 W. Europe 305 447 1.70 2.47 i:: E. Europe 81 USSR 359 480 ;*Ei 1;*2 1.90 6.54 Japan, Australia, N.Z, 128 320 4:3 6:3 0.55 2.02 2': Latin America 323 797 0.93 2.8 0.30 2.22 7.4 Africa 370 885 0.16 0.06 0.94 16 China & Indochina 1029 1714 0.61 :$I 0.63 3.43 5.4 South Asia 1170 2665 0.20 0.23 2.80 12 Mid-East 110 353 1.0 2; 0.11 1072 16

--- --- World average

or total 4031 7976 2.0 3.4 8.20 26.9 3.3

178000 TW solar radiation incident

62000 TW reflected

76000 TW heat reradiated immediately

nuclear fuels

conduction to surface

0.3 TW geothermal heat convection in volcanoes and hot springs

Fig. ICI. TerrestriaZ pawer fZaws. PracticaZZy aZZ incident energy is uZtimateZy reradiated as heat (not show). Based on data from M. K. Eubbert, "Energy resources of the em?th", Scientific American (September, 19711, J. M. Weingart, "GZobaZ aspects of sunzight as a major energy source", Energy 5 775-798 (19791, and J. M. Weingart, private conmzunication, 1981.

6 lD, Solar Energy

247 X 108 tonnes

Year

Fig. lC2. Estimate of world crude oiZ production rates for the future. From Energy axd Technology Review, March 1977, p. 6. Courtesy 0fLLiVL.

YEAR

Fig. lC3, Necessary limits on fossi Z fue 2 conswnption, if the increases of

prevent various increases in atmospheric atmospheric CO2 concentration are to be CO2 concentrations are shown in Fig. 1~3. kept below 50%, 100%, and 200%. What

change can safely be tolerated is not If the CO2 concentration becomes yet known, From W. HaefeZe and W.

too high, then the resulting climate Sassin, Energy strategies, Energy J 147 change could melt the polar ice caps, (1976). Copyright 19 76, Pergmnon increasing the ocean levels and flooding press, Ltd. major coastal cities. Therefore, not all of the available coal can be safely burned.

limits of usable energy

Estimates of the limits of various energy sources are listed in Table 1Cl. Comparing these values with the estimated power demand of 50 TW in the year 2050, we see that only solar, fission, and fusion power can meet our long-term energy needs.

Nuclear fission power appears to be the most economical power source in the near .future. It has an excellent safety record. Solutions to environmental pro- blems, such as radwaste disposal, have been found, but political opposition is hindering its development.

Some estimates of solar power available in 2030 have been over 10 TW, but the 3 TW limit reflects the time it takes to manufacture and move enormous quan- tities of material and to "penetrate the market" economically (Haefele, 1979).

1D, Solar Energy Solar heating and cooling of buildings is already economically competitive in

some locations, Solar electric power, however, may take longer to be economically attractive. Four schemes are receiving wide attention: photovoltaic, satellite

lD, Solar Enemy 7

Table lC1. Limits of various energy sources. Data from Rotty (1976), Weingart (1979), Hubbert (1975), HaefeZe (1979), and WaZton and Spooner (1976). These are rough estimates, but indicate the order of magnitude which coon be expected.

renewable energy sources

ing solar electric, heating & cool

biomass

wind power

wave power & tidal power

hydroelectric power

geothermal power

organic wastes

practically recoverable fossi 1 fuels

coal E lignite (2.35~1012 tons)

crude oi 1 (2.1~10~~ barrels)

natural gas (3.4~10~~ m3)

tar-sand oi 1 (3~10~~ barrels)

shale oil (1.9x1O11 barrels)

total

nuclear fission fuels

‘J-235

u-238, Th-232

nuclear fusion fuels

I ithium for DT reactors on land

POWER LIMITS, TW

by 2030 ultimately

$3 ~1001

3 10

1 3 . 1 1

1.5 2.9 0.2 0.4 0.1 0.1

ENERGY LIMITS

Joules TW-yea rs

53.2~10~~ 1690

12.4~10~~ 390

13.1x1021 415

1 .8x1021 57

1.1x1021 35 i1 .6x1021 2590

Joules

1 022

’ 1o25

. TW-years

300

’ 3x105

Joules

2xlOT’f

TW-years

6x1 o4 in oceans, containing 0.17 ppm Li 2x107-8 6x108

deuterium in oceans 8x10~~ 2x101’

power stations , solar thermal, and ocean thermal power.

The simplest is photovoltaic panels (solar cells), which can be located on individual buildings. They cost about 10 $/peak Watt in 1980. Mass production may reduce the price by an order of magnitude or more, as it did for the manu- facture of transistors. However, a storage system will more than double the initial cost, and the average power is about l/4 the peak power, so the effective cost per average Watt is an order of magnitude higher than the peak-Watt cost.

8 lE, Fusion Reactions Solar satellite power stations (SSPS) would collect power with photovoltaic

panels on a satellite station in geosynchronous orbit (stationary over one point on earth) and transmit the power to earth via 2.45 GHz microwaves. While they appear to be technologically feasible, the SSPS can be economical only if major reductions in the cost of orbiting heavy payloads are achieved.

The most popular solar thermal electric conversion (STEC) schemes involve a central boiler heated by sunlight from an array of heliostats (reflectors). For example, a 10 MWe demonstration plant at Barstow, California, uses a central tower boiler surrounded by about 1800 heliostats, each with 40 m2 area, and incorporates 3-4 hours of thermal energy storage in rock and heat-transfer oil (Caloria). Assuming that a 50% load factor were achieved with on-site thermal storage, commercial STEC plants of similar design operating under ideal solar conditions might cost 2000-3000 $/kWe, if collector costs could be held to 100 $/m2 or less.

Ocean thermal electric conversion (OTEC) systems use a fluid with a low boiling temperature , such as ammonia, to run a Rankine cycle heat engine from ocean tem- perature gradients. For example, warm surface water at 300 K could evaporate ammonia in a boiler and drive a vapor turbine. Cool subsurface sea water at 278 K could cool the ammonia condenser to complete the cycle. Because the AT is so small (around 20 K), the cycle efficiency will be very low, necessitating high water flow rates and large, expensive heat exchangers. Other dominant cost items are the floating ocean platform, the cold water pipe, and the cable to carry the electricity to shore. Alternatively, the electricity could be used to produce hydrogen by electrolysis of water, and liquified hydrogen could be shipped as a fuel. Excluding the cable cost, a 250-400 MWe plant is expected to cost about 2000 $/kWe (1978 $).

It appears that various forms of solar power could produce electricity at costs of 70-100 mills/kWh, compared with about 20-40 mills/kWh for other sources (1 mill = .OOl $). Rapid deployment of solar electric power stations is limited by the huge surface areas which must be covered with collectors. The 24-hour average solar power flux in the Southern United States is on the order of 200- 300 W/m2. The flux is somewhat higher near the equator, and lower in northern latitudes. About 100 TW thermal energy might ultimately be collected by covering 10% of the earth's desert areas with collectors. This is the basis for the speculative figure of Table lC1.

In spite of the advantages of solar power, it is still desirable to develop cheaper power stations which do not require a sunny climate, large collector areas, and large energy storage systems.

lE, Fusion Reactions energy release

Nuclei with intermediate masses have the lightest average masses per nucleon, as shown in Fig. 1El. When light elements are fused together or heavy elements are split apart, the resulting intermediate elements have less mass per nucleon. The excess mass AM is converted into kinetic energy :

lE, Fusion Reactions 9 W = 4Mc2 = (total inital mass - total final mass)c2

where c is the speed of light. .

EXAMPLE PROBLEM 7El 1 .OOlO -

(1El)

CaZcuZate the energy reZeased by the reaction D + T+ 4He + n.

Using nuclear masses from App. B, we c have

AM = 2.013553 + 3.015501 - 4.001503 - 1.008665 = 0.018887 u = 3.13631x1O-2g kg,

so W = AMc2 = 2.8188x10-l2 J = 17.593 MeV. 79990 -

0

Fig. lE1. m

Average mass per melleon vs. atomic mass nwnber. From R. D. Evans,

F.9985 -

The Atomic IVzuZeus, p. 295, copyright 9 1955, McGraw-Hill, Neu York. Used by ?9980- I I I I pemrission of McGraw-Hi22 Book Company. 0 50 100 150 200

Atomic Mass Number A

fusion fuels

Possible fusion reactor fuels include H, D, T, 3He, 6Li, and llB. Some nuclear reactions of interest are shown in Table 1El. If the initial particles have energies ~0.1 MeV, then the kinetic energy of the reaction products is divided up approximately in inverse proportion to their masses (to conserve mom- entum). For the DT reaction, the neutron gets 4/5 and the alpha particle (4He) gets l/5 of the kinetic energy.

The DT reaction is the most probable reaction at temperatures attainable in fusion reactors. (Reaction rates and probabilities will be discussed in Chapter 2.) Since deuterium constitutes 0.0153% of natural hydrogen, it is very abundant. The amount of tritium in nature is negligible, so it must be produced artificially. It can be produced by neutron absorption in lithium, as indicated in Table 1El.

(Seawater contains 0.17 ppm of Li and 0.003 ppm of U.) The DT reaction has the following disadvantages: * It is necessary to breed tritium from lithium (Chapter 27). * The 14.1 MeV neutrons cause radiation damage and make walls radioactive

(Chapter 24). * Precautions are needed to minimize release of radioactive tritium

(Chapter 28). * Only l/5 of the reaction energy is carried by charged particles and can be

directly converted into electricity (Chapter 26).

The two branches of the DD reaction (DDn, DDp) have roughly equal probabil- ities. If the T and 3He produced by these reactions react with more deuterium, then the net reaction is

6D + 2H + 2n + 24He + 43.2 MeV (1E2)

10 lF, Fusion Reactors Table lE1. NucZear Reactions of Interest. Numbers in parentheses are approx- imate energies of reaction products, MeV. The exact energies vary with angle q $n$derf partitle energies. !l!he symboh p, d, t, n, and a represent 1 '1 '1 ' 0 n, and ,He.

energy yield name fusion reactions abbreviated form MeV Joule -

DT: D + T + 2He (3.s) + in (14.05) T(d,n)4He 17.59 2.818xlo-'2

DDn : zHe(.82) + in(2.45) D(d,n) 3He 3.27 5.24~10-~~ D+D+

DDp : T(l.01) + ~(3.02) D(d,p)T 4.03 6.46x10-‘3

TT: T + T + in + ln + ZHe T(t,2n)4He 11.3 1.81~10’~~

D-3He: D + ZHe + ;Hei3.66) + ~(14.6) 3He (d , p) 4He 18.3 2.93x10-12

p-6Li : p + :Li + ZHe + ZHe 6Li (p,a) 3He 4.02 6.44x10-13

p-llB: p +ltB + 3(zHe) 11B(p,2a)4He 8.68 1.39x10’12

reactions for breeding tritium (Natural lithium is 7.5% 6Li, 92.5% 7Li.)

n-6Li : !Li + in(therma1) -t 7*- IzT2.5~

;He(2.05) + T(2.73) 6Li (n,a)T 4.78 7.66x10=

n-7Li : ZLi + in (fast) + T + ZHe + in 7Li (n,n’ ,a)T -2.47 -3.g6x10-13 (endothermic)

which is called the "catalyzed DD reaction", since the high-probability DT reaction has the effect of a catalyst. The average yield per deuteron is 7.2 MeV, which is an energy yield of 3.44~10'~ J/kg. The "catalyzed DD" fuel cycle eliminates the need to breed tritium from lithium, but it requires higher temper- atures and has lower power densities than the DT reaction. Because of the more advanced technology required for the DD and D-3He reactors, these are called "advanced fuel" reactors.

The 3He produced in a DD reactor could either be burned in the same reactor or burned in a "satellite reactor" using primarily the D-3He reaction. The advantage of D-sHe satellite reactors is that the neutron emission rate could be greatly reduced, resulting in much less wall activation and radiation damage.

The p-6Li and p- llB reactions are practically free of neutron emission, and all the reaction products are charged particles, amenable to direct conversion. How- ever, these "exotic fuels" also have low power densities and require even higher temperature operation than the "advanced fuels", so it will be difficult to make an economical reactor using the exotic fuels.

IF, Fusion Reactors The two main requirements for building a fusion reactor are to heat the fuel

to ignition temperature and to confine it while it "burns".

Why is heating necessary before fusion reactions occur ? The positively charged nuclei repel each other, and cannot approach close enough for a nuclear reaction to occur unless they have high relative velocities.

1F. Fusion Reactors 11 Imagine trying to break an egg inside a foam rubber sphere by throwing other

eggs in foam rubber spheres at it. They will merely bounce off unharmed unless you throw them at high velocity. In this analogy the egg is like the nucleus of deuterium or tritium, and the foam rubber represents the coulomb potential field surrounding the nucleus. Only when the ions have large relative velocities can they push through the coulomb barrier to produce a nuclear reaction.

In order to overcome the barrier, the ion's kinetic energy must almost equal the potential energy of repulsion of the two point charges, For example, the required ener y (about 5x10-l 3

for a deuteron and a triton to approach within a nuclear diameter m) is found from Eq. (lA4) to be about 290 keV. Because of the

quantum-mechanical "tunneling" effect and because some particles have much higher velocities than the average, the actual fuel temperatures required for the DT reactions are

T z 10 keV -.lOs K. (lF1)

The ion"

required confinement time T is given approximately by the "Lawson criter-

where n is the plasma ion density (ions/m3). required confinement time is about 1 s.

If n = 102* mm3, then the

The temperatures required to burn various fuels will become apparent from a study of nuclear reaction rates in Chapter 2. Following a discussion of radia- tion losses in Chapter 3, the confinement times required for various conditions will be derived in Chapter 4.

research progress

Fusion research experiments fall into two general categories: magnetic confinement and inertial confinement. Magnetic confinement employs strong magnetic fields to provide thermal insulation between the plasma and the chamber walls. Inertial confinement allows free plasma expansion and cooling, but relies on an extremely high density n to attain the Lawson criterion in the short expansion time (typically a few ns). The high density is attained by compressing a solid fuel pellet to over 1000 times its initial density, using laser beams or ion beams.

Fusion research experiments began in the 1950's, with hopes of rapid success, but plasma instabilities spoiled confinement. Ways to prevent various instabilities were found in the 1960's, as plasma theory made great progress. Many nations shifted experimental emphasis to tokamaks in the 1970's, following Soviet experimental success. Major experimental programs in inertial confinement fusion (ICF) were initiated in the 1970's, following optimistic predictions of attainable energy yields, In the late 1970's several other plasma confinement schemes have shown promise, including tandem mirrors, the field reversed pinch, ohmically-heated toroidal experiment, stellarators, Elmo bumpy torus, and compact toroids.

The magnetic confinement and ICF programs will both demonstrate break-even conditions (fusion power exceeding input power) in the mid-1980's, but many engineering problems remain. A Fusion Engineering Device will be constructed to demonstrate small-scale power production, to test reactor materials, and to develop various aspects of fusion technology.

12 lF, Fusion Reactors

Fig. 3Fl. Schematic diagram of a magnetic confinement fusion power pkwzt. From H. J. WiZZenbeq, T. J. Kabele, R. P. May, axd C. E. WiZZingham, "MateriaZs flow, recycle, and disposal for deuterium-tritium fusion", PA?&2830 (1978), Fig. 1, p.3.

power plants

Some elements of a fusion power plant are illustrated in Fig. 1Fl. The plasma heating system is not shown. An ICF power plant will have similar components, but no magnet coils (unless the blast chamber walls are magnetically protected).

Potential applications of fusion power are shown in Fig. lF2. Fusion reactor design studies estimate electrical power costs of about 35-40 mills/kWh (1980 constant $),which are comparable to costs of power from fission and fossil fuel plants. Estimated costs of solar electrical power are 70-100 mills/kWh (Weingart, 1979). Fusion power will be especially valuable if

* fuel imports are limited * coal use cannot rapidly increase (due to mining, transportation, or

environmental limitations) * the LMFBR is not rapidly cotmnercialized * solar electric power costs do not become competitive * discount (interest) rates are not too high * fusion can be developed rapidly.

The development of fusion power will probably cost about30 billion dollars.

FORMS OF FUS I ON ENERGY OUTPUT

lF, Fusion Reactors 13

PROCESSES POTENT I AL

APPLICATIONS

I METHANOL HYDROGEN & COAL

I . I I I . “ “ L I .

OF FISSION WASTES

I ) NEUTRON ACTIVATION ANALY S I S

NEUTRON RAD I OGRAPHY

I ELECTRICITY I

/ --) IRON E ALUMINUM FUSION TORCH WITH

+ PLASMA CENTRIFUGE ORE REDUCTION

WASTE MATERIAL RECYCLE I

HYDROGEN BY PHOTOLYS IS OR

L RAD ’ *’ “- ’ -

FERTILIZER HYDROGEN &

NITROGEN IULY>IS 1

METHANE GAS HYDROGEN & I

X-RAYS, GAMMA-RAYS, ULTRAV I OLET

RADIATION

1 tlYlJKULY3lS J

. FISH & SHRIMP

PRODUCTION

I t STERILIZATION 1 ) & SEWAGE

TREATMENT I

INDUSTRIAL ) DISTRICT HEATING &+ GREEN HOUSE

AIR CONDITIONING AGRICULTURE & HYDROPONICS 4

Fig. lF2. Potential applications of fusion power. ("Magnetic Fusion Program Swnrnq Docwnent", Report HCP/T3168-01, prepared by TRW, Inc. for the U. S. Department of Energy, 1979.)

14 lG, Sumnary

lG, Summwy The world power demand will rise to tens of TeraWatts in the 21st century.

Most of the rise will be in developing nations, so efforts by industrialized countries to conserve energy will not prevent the power demand increase. Fossil fuels will be nearly exhausted by 2030, except for coal. Environmental problems, such as CO2 accumulation in the atmosphere, may limit the allowable coal consumption. Tidal, wave, wind, hydroelectric, geothermal, biomass, and organic ;;+,Q;E power together will be inadequate to meet-the earth's long-term energy

. Only fission, solar, and fusion power will be adequate.

Fission breeder reactors are already successful. The huge collector areas and energy storage systems required by solar electric power plants make it difficult to bring costs down. Fusion power plants offer the prospects of continuous operation and cheap, abundant fuel. However, there are still many problems to solve, and it will be many more years before the development of fusion power is complete.

Problems

If a person's body burns 2000 kcal/day of food energy, what is his average Altabolism (Watts) ? How many TW food energy would be needed to feed eight billion people at this rate ? If each Joule of food energy required 8 J input to agriculture, how many TW would be required for agriculture ?

2. Calculate the energy yields of the DDn and DDp reactions.

3. Estimate the energy costs of the following forms of energy ($/MJ) : a. 1 liter of gasoline at $ 0.50 (heat of combustion 47 MJ/kg, and density

705 kg/m3 ). b. 1 slice of apple pie (300 kcal) at $ 0.90 . c. electricity at 50 mills/kWh. d. energy storage in a lead-acid battery storing 80 Amp-hr at 12 V and

costing $ 50 . e. work by a draft horse laboring 8 hours/day at a power of 1 kW, and

costing $ 15/day for care.

4. A 3 GWth (Gigawatts thermal power) fusion reactor operates at full power 70 % of the time for a year, burning catalyzed DD fuel. How many kg of deuterium will be consumed ? How many cubic metres of water are needed to extract this much deuterium ?

5. How many litres of gasoline are required to produce the same energy as the energy of deuterium from 1 liter of water burned in a catalyzed DD reactor ? (Data on gasoline is given in Problem 3a.)

6. A fusion reactor has a cylindrical coil with 8 = 5 T inside and 8 = 0 outside. The coil current is 10 kA, and the internal volume is 500 ma. Estimate the ( approximate stored energy of the magnetic field (Table JAJ) and the coil inductance.

7. Assuming that the world power consumption grows at 6 %/year from PO= 8 TW in 1980, and that 80 % of the power comes from fossil fuels, in what year would the fossil fuels be exhausted ? [ W = / dt P(t) 1.

1, Bib1 iowaphy 15

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solar energy

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fusion

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