黄金分割率理论Ξ
E nergy E ff i ciency and R ene w a b le E nergy R esources
CHAN- K AI Marcel , LAN Sheng-fang
( C ollege of forestry ,S outh C hina Agricultural University , G uangzhou 510642 ,C hina) Abstract : Exciting new techn olog ies have b een invented to u renewable energ y sources. Ocean thermal诗可以兴
electric conversion , tid al and w ave pow er stations and g eothermal steam source can produ ce uf u l am o unts of
energ y in some localities. One o f the m ost promising techn olog ies is d irect electricity g eneration b y Photo2 v oltaic cells. S ince solar energ y is availab le everywhere , Photov oltaic collectors cou ld provid e clean , inex2 pensive , non- pollu ting , renew able energ y , ind epend ent of cen tral pow er g rids or fu el- su pply systems.
我的大学规划Biomass also may have some m od ern applications. In add ition to d irect combustion , b iomass can b e convert2
ed into Methane or Ethanol , w hich are lean - burning , easily storab le and transportab le fu els. The alterna2
tive us of b iomass also allow nu trients to b e returned to the s oil and help redu ce our reliance on expensive , energ y- consu ming artificial fer tilizers. Fu el w oo d , w in d mills an d w aterw heels , for instance , once su pplied a
major part o f the ex tern al energ y for hu man activities. M ore major conrvation m ethods , su ch as home insu2
lation and energ y- efficient appliances and transpor tation , can d rastically redu ce ener g y consu mption and sim2 ilarty redu ces energ y expens. Our natural resources , our environmen t and our pocket b ooks all b enefit from
carefu l and efficient energ y consu mption.
K ey w or d s : ener g y efficiency ; energ y resources ; renew ab le energ y
CL C numb er : TK01 Docum ent cod e : A Article I D : 100828873 (2001) 01 ,2 20065205
1 Introduction
E nergy derves its reputati on as one of our m ost critical resources. Without it , life w ould cea . We derive energy from the food we eat . Through photosynthesis , the plant life we consum e both direct2 ly and indirectly when we eat m eat ; depends on energy from the sun. The m aterials we u t o build our hous and produce the goods we consum e are ex tracted from the earth’s crust , then transform ed into finished products with ex penditures of energy.
E nergy efficiency is the short- run key to sustainable devel opm ent becau it offers the opportunity to increa living standards without increasing energy consum pti on. E nhanced energy efficiency , which can stretch energy supplies , sl ow clim ate changes and buy tim e to devel op alternative energy resources , can be achieved in a variety of ways.
N onrenewable energy resources (fossil fuels and nuclear power) currently provide about 95 % of the comm ercial energy ud w orldwide . Large supplies of fossil fuels rem ain in the earth , but we are rapidly using the easily retrievable deposits. E conom ics and environm ental cost increa as we turn to m ove rem ote and risky resources. Maintaining our technol ogical society consum es so m uch energy that we soon will run out of affordable supplies and face unacceptable environm ental effects unless we radi2 cally change our consum pti on patterns or find som e new , clean renewable energy resources.
The devel oped countries of the w orld have only 20 % of the total w orld populati on but consum e 2/ 3 of all comm ercial energy. I f the rest of the w orld were to u energy at the per capita rate that we
Ξ收稿日期: 2001201204 ; 作者简介: 陈盖(1967 - ) , 男, 马达加斯加来华留学博士生.
66 生态科学第20 卷do , there w ouldn’t be enough fossil fuel to support all of us. Furtherm ore , the environment couldn’
t withstand the assault of ex tracting and burning all that fuel . E nergy consum pti on is rising rapidly in devel oping countries. S om e people argue that the other four-fifths of the w orld cannot ri to the sam e standard of living we now enj oy.
But fossil fuels and nuclear power are not only opti ons. R enewable sources such as s olar and wind power could provide m ost of the energy we need.
In this paper , we will l ook at som e valuable energy alternatives m easures that can reduce energy
consum pti on , as well as som e promising renewable energy resources that offer ex citing prospects for
sustainable , environm entally benign future .
2 Eval u ating energy resources : N et energy
The only energy that really counts it takes energy to get energy. F or ex am ple , oil m ust be found ,
pum ped up from beneath the ground , transported to refinery and converted to uful fuels ( s uch as gasoline , diel fuel and heating oil) , then transported to urs , and then burned in furnaces and cars before it is uful to us. E ach of the step s us energy and the cond law on energy tells us that each tim e we u energy to perform a task ; som e of it is al ways wasted and is degraded to l ow quality energy.
The usable am ount of high- q uality energy available from a given quantity of an energy resource is its Net energy —the total uful energy available from the resources over its lifetim es , minus the am ount of energy ud (the first law of energy) , autom atically wasted (the cond law of energy) and unneces2 sarily wasted in finding , processing , concentrating and transporting to its urs. Net energy —not the total energy available from a particular energy resource —is the only energy that really counts. Net en2 ergy is like your net spendable incom e —y our wages minus tax es and other deducti ons.
F or ex am ple , suppo that for each 10 units of energy in oil in the ground we have to u and waste a total of 8 units of energy to find , ex tract , process and transport the oil to urs. Then we have only 2 units of net energy available from each 10 units of energy in the oil .
3 The importance of improving energy eff i ciency :
R educing energy w a s te
E nergy efficiency is a m easure of energy produced com pared to energy consum ed.
The easiest , fastest and cheapest way to get m ore energy with the least environmental im pact is to eliminate much of this energy wasted by m aking lifestyle changes that reduce energy consum pti on (walking or biking for short trip s , turning off unneeded light ) .
Another equally im portant way is to increa the efficiency of the energy conversi on device we u .E nergy efficiency is the percentage of total energy input that does uful w ork (is not converted to l ow- q uality , esntially uless heat )in an energy conversi on system. Im proving energy efficiency m eans getting the sam e w ork out of a device with a l ower energy input . The energy conversi on devices we u vary in their energy efficiencies. We can save energy and m oney by bu
ying the m ost energy - efficient hom e heating system , water heaters , cars , refrigerator , com puter and other appliances that are available and by supporting rearch to invent even m ore energy- e fficient devices.
The net efficiency of the entire energy delivery process for a space heater , water heater or car is determined by each step in the energy conversi on process. F or ex am ple , the quence of energy- u sing (and energy wasting) step s involved in using electricity produced form fossil or nuclear fuels is in ex2
第1 , 2 期陈盖等: 能量效率与可更新能源67 tracti on —transportati on —pr ocessing —transportati on to power plant —electric generati on —
transm issi on —e nd u .
R educing energy waste : is one of the planet’s best and m ost im portant econom ic and environmen2 tal bargains becau it m akes non renewable fossil fuels last l onger ; give us m ore tim e to pha in re2 newable energy resources ; decreas dependence on oil ; reduces l ocal and gl obal environm ental dam2 age becau lesson each energy resource w ould provide the sam e am ount of uful energy ; save m ore m oney , provides m ore j obs and prom otes m ore econom ic
growth per unit of energy than other alterna2 tives ; im proves com petitiveness in the internati onal m arket - place .
4 Solar energy
团建活动有哪些
The sun rves as a giant nuclear furnace in space , constantly bathing our planet with a free ener2 gy supply. S olar heat drives winds and the hydrol ogic cycle .All bi om ass , as well as fuels and our food ( b oth of which are derived from bi omass) , results from conversi on of light energy (photon) into chemi2 cal bond energy by photosynthetic bacteria , algae and plants.
The average am ount of solar energy arriving at the top of the atm osphere is 340 watts per square
m eter . About hal f of this energy is absorbed or reflect by the atm osphere (m ore at high latitude at the equator) , but the am ount reaching the earth’s surface is som e 8000 tim es all the comm ercial energy ud each year .
S olar therm al system s collect and transform radiant energy from the sun into therm al energy ( h eat) at high tem perature , which can be ud directly or converted to electricity.
S olar energy can be converted directly into electrical energy by Photovoltaic ( PV) cells , comm on2
ly called S olar cells. The PV offers an ex citing potential for capturing solar energy in a way that will
provide clean , versatile , renewable energy. This sim ple device has no m oving parts , negligible m ain2
tenance costs , produces no polluti on and has a lifetim e equal to that of a conventi onal fossil fuel or nu2
clear power plants.
5 E nergy from bioma s s
Photosynthetic organism s have been collecting and storing the sun’s energy for m ore than 2 billi on years. It w ould be ridicul ous to consider consuming all green plants as fuel , but bi om ass has the po2 tential to becom e a prim e source of energy. It has m any advantages over nuclear and fossil fuels be2 cau of its renew ability and easy accessibility. Bi om ass resources ud as fuel include w ood , w ood chip s , bark , branches , leaves , starchy roots and other plant and m aterials.
Many form of a bi om ass or organic m atter in plants produced through photosynthesis , can be burned directly as a s olid fuel or converted into gaous or liquid bi ofuels.
In agricultural areas , crop s residues ( s uch as cane sugar residues , rice husks , cotton stalks and
coconut shells) and anim al manure can be collected and burned or converted into bi ofuels. Since 1985 , Hawaii has been burning bagas (the residues left after sugarcane harvesting and pr ocessing) t o supply alm ost 10 % of its electricity.
Plants , organic wastes , wage , pulp s and paper mill sludge and other form of solid bi om ass can
be converted by bacteria and vari ous chemical process into gaous and liquid bi ofuels. Ex am ple in2
蔬菜汤
cludes bi ogas (a mixture of 60 % m ethane and 40 % Di oxin carbon) , liquid ethanol (ethyl or grain al2
cohol) and liquid m ethanol (m ethyl or w ood alcohol) .
T w o billi on people , about 40 % of the total w orld populati on depends on firew ood and charcoal as
their prim ary energy source .Of the people , 3/ 4 does not have adequate , affordable supply. Most of
68 生态科学第20 卷
the people are in the less - devel oped countries where they face a daily struggle to find enough fuel to warm their hom es and cook their food. The problem is intensi fying becau rapidly growing populati on in m any third w orld countries create increasing dem ands for firew ood and charcoal from a diminishing supply.
E nergy from the earth’s f o rces
5
The winds , waves , tides , ocean therm al gradients and ge otherm al areas are renewable energy sources . Although available only in lected l ocati ons , the sources could m ake valuable contributi ons to our total energy supply.
511 H ydropo w er
In a large- scale hydropower project , a high dam is built across a large river to create a large rervoir . The stored water then fl ows through huge pipes at controlled rates , spinning turbines and producing electricity. Such projects have advantages and disadvantages.
Advantages : downstream fl ooding is reduced ; provides water for year- r ound irrigati on of cropland ; can produce cheap electricity ; rervoir is uful for recreati on and fishing.
Disadvantages: enorm ous l oss of water through evaporati on ; mass of water can cau earth2 quakes ; fl ooded land destroys forest or cropland and displaces people ; danger of collap ; downstream cropland and estuaries are deprived off nutrient- rich silt ; migrati on and spawning of som e fish are dis2 rupted ; ex pensive to build.
512 Wind energy
Since 1980 the u of wind to produce electricity has been growing rapidly. In 1994 there were nearly 20 000 wind turbines w orldwide , m ost grouped in cluster called Wind farm that collectivity pro2 duce 3 000 m egawatts of electricity.
Advantages : unlimited source of energy and even ex cluding environmentally nsitive areas ; is about 5 tim es current w orld electricity u ; can be built in 6 m onths to a year and then easily ex panded as needed ; emit no heat - trapping di oxin carbon or other air pollutants ; the land under wind turbines can be ud for grazing cattle and other purpo and leasing land for wind turbines can provide extra incom e for farm er and ranchers ; one of the w orld’sp cheapest ways t o produce
electricity.
Disadvantages : might interfere with the flight pattern of m igratory birds in certain areas ; have killed birds of Prey (especially Hawks , Falcons and E agles) that prefer to hunt al ong the sam e ridge lines that are ideal for wind turbines ; occupy places with wind and weather too vere for residential or other devel opment ; destroy the n of isolati on and natural beauty.
513 G eother m al energy
The earth’s internal tem perature can provide a uful source of energy in som e places. High- tem2 perature , high-pressure steam fields ex ist bel ow the earth’s surface . Around the edges of continental plates or where the earth’s crust overlays m agm a ( m olten rock) pool cl o to surface , this energy is ex presd in the form of hot springs , geyrs and fum aroles.
Advantages : a vast , reliable and som etim es renewable supply of energy for areas near rervoir sites ; m oderate Net energy yields for large and easily accessible rervoir sites ; fewer di oxin carbon e2 m issi ons than fossil fuel ; com petitive cost of producing energy.
Disadvantages : can be depleted within a few decades ; can destroy or degrade forest or other e2 co
system s ; som e areas the ex tracti on of hot water from hot water rervoirs caus land to sink ; caus m oderate to high l ocal air and water polluti on ; noi , odor and l ocal clim ate changes ; the cost of tap2
第 1 , 2 期 陈盖等 : 能量效率与可更新能源 69 ping geotherm al energy is too high.
514 T id al an d w a ves energy
Ocean tides and waves contain enorm ous am ounts of energy that can be harnesd to do uful w ork.风险规避
Advantages : a free source ( t he m oon ’s gravitati onal attracti on ) ; a m oderate net uful energy yield ; no di oxin carbon is added to the atm osphere ; air polluti on is l ow ; little land is disturbed.
Disadvantages : a tiny contributi on to gl obal electricity supplies ; few suitable sites ; constructi on costs are high ; tidal energy can harm ∃ even destroy ∃ the ecol ogical functi oning of estuaries.
T wice a day water that fl ows into and out of coastal bays and estuaries in high and l ow tides can be ud to spin turbines to produce electricity.
The kinetic energy in ocean waves , created prim arily by wind , is another potential source of elec 2 tricity. A wave power to m ake a little contributi on to gl obal electricity producti on , ex cept in a few coastal areas with the right conditi on. C onstructi on costs are m oderate to high and the net uful energy yield is m oderate , but equipment could be dam aged or destroyed by saltwater corrosi on and vere storm s.
515 Ocean ther m al electric conv ersion
T em perature di fferentials between upper and l ower layers of the ocean ’s water also are a poten 2 tial source of renewable energy.
Disadvantages include the energy cost of pum ping up deep water (which could eliminate m ost of energy advantage of the system ) ; saltwater corrosi on of pipes and equipm ent , vulnerability to storm dam age and ecol ogical destabiliz ati on from the up welling of deep ; nutrient- rich water and l ocal alter 2 nati ons of ocean tem perature .
画灯笼图片R eferences :
1 MI LNE T A , G R ATS ON D ,NI M LOS M. C ataly tic hot- g as clean u p of b iomass- p rodu ced 烦心事图片
synthetic g as A . In : K LAN D L ,ed. Energ y and w astes from b iomass ⅩⅣM . Chicag o : Institu te o f G as techn olog y ,1991. 759 -
780.
ODUM E P. Basic ecolog yM . C BS C olleg e p ub lishing , The Dryd en press ,1983. 86 - 169.
RIV A G . Utilization o f renew ab le energ y source and energ y - saving techn olog y b y small- scale milk plants and co 2l lection cen tersM . 1992. 17 - 39.
V O G T. Energ y conrvation and u of renew ab le energ y in the b io- i ndustriesM . Perg am on press ,1991. 574. WOODS J , H A LL D O. Bioenerg y for d evelopment : Technical and Environmental d imension. FAO Environment and Energ y paper ,1994. 7 - 42. 2 3 4 5
能量效率与可更新能源
陈 盖 , 蓝盛芳
(华南农业大学林学院 , 广东 广州 510642)
要 : 一些可更新能源可减少甚至消除我们对化石能和核能的依赖 , 其中很多虽然已为人类使用数百 摘 年 , 但因为化石能的普遍使用 , 一直都为起人类的注意 。人类已发明了新技术来利用这些可更新能源 。 其利用有赖于一定的技术是既定的事实 , 目前有成功建立这样的能源工业还是十分昂贵的 。如果人类生 产经济和市场允许的话 , 这些新技术经进一步改进和简化后 , 就可以降低成本 , 并且应用起来也很可 靠 。相对于开发应用核能 , 水能 和化石能数以百万计的投资耗费来讲 , 用于可更新资源的资金可谓微乎 其微 。虽然传统能源和替代能源各具优点 , 但保护能源往往还是解决能源短缺最便宜 , 最容易的途径 。 关键词 : 能量效率 ; 能源 ; 可更新能源
