the global status of renewable energy technologiesrenewables.ru/pdf_doc/10_2005touryan.pdf ·...

International Scientific Journal for Alternative Energy and Ecology ISJAEE ¹ 10(30) 2005Ìåæäóíàðîäíûé íàó÷íûé æóðíàë «Àëüòåðíàòèâíàÿ ýíåðãåòèêà è ýêîëîãèÿ» ÀÝÝ ¹ 10(30) 2005 69

© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

ECOLOGICAL ASPECTS OF ALTERNATIVE ENERGY AND ECOLOGY OFMEGAPOLISES, CITIES AND VILLAGES

ÝÊÎËÎÃÈ×ÅÑÊÈÅ ÀÑÏÅÊÒÛ ÈÑÏÎËÜÇÎÂÀÍÈß ÀËÜÒÅÐÍÀÒÈÂÍÎÉÝÍÅÐÃÅÒÈÊÈ, ÝÊÎËÎÃÈß ÌÅÃÀÏÎËÈÑÎÂ, ÌÀËÛÕ ÃÎÐÎÄÎÂ, ÄÅÐÅÂÅÍÜ

THE GLOBAL STATUSOF RENEWABLE ENERGY TECHNOLOGIES

K. J. Touryan

NREL1617 Cole Blvd. MS 1635 Golden, CO 80401

Phone: 303-275-3009; fax: 303-275-3040; e-mail: [email protected]

The inability of fossil fuels to keep up with the rapidly increasing demand for energy, especially indeveloping countries, is making imperative the search for alternate energy sources. Renewable technologies,including the use of hydrogen, offer new hope of meeting this increasing demand in significant ways.To this end, we review the status of several of these renewable energy technologies and their readinessto compete in the energy market, in the immediate future.

Ñòàòüÿ ïîñòóïèëà â ðåäàêöèþ 11.11.2005. The artiñle has entered in publishing office 11.11.2005.

Introduction

As we enter the 21st century, all indicationsare that the world will run out of fossil fuelsmuch sooner than past predictions. In fact, mostforecast point to the time frame of 2010–2015when oil production world wide, will peak, and2020, when natural gas production will peak(Fig. 1). Coal may last until the end of the centu-ry, but subject to stringent environmental con-trols. In fact, there are five global trends that areconverging, to make the introduction of new ener-gy technologies, such as renewable energy andhydrogen, viable options to replace a significantportion of the increasing global energy demand.These five are: 1) Increasing environmental aware-ness specially as it pertains to the emission ofgreen house gases; 2) The availability of new tech-nology options, such as energy from wind, solar,biomass and hydrogen from renewable resources;3) World energy demand growth, specially in Asia;

4) Increased security risks, with terrorists attack-ing power oil/gas pipelines, refineries and largepower plants, plus uncertainties in the availabilityof fossil fuel resources caused by political unrest,

As part of the NREL Technology Transfer Team, Ken Touryan manages avariety of technology transfer activities, including NREL’s Initiatives forProliferation Program (IPP). Ken created the IPP program at NREL and hasmanaged this multi-laboratory effort for the past nine years. The IPP programwas initiated in 1994 to control and reduce the global threat represented bynuclear, chemical and biological weapons. IPP aims to identify and developnon-military applications for defense technologies and create high-tech commercialemployment opportunities for weapons scientists and engineers. Under Ken’sleadership, this program has created many successful partnerships betweenU.S. firms and former weapons scientists, provided synergies with NREL’sapplied research, and established a unique link between NREL’s technical expertiseand global security.

Kennel J. Touryan,Ph. D., Manager,

NIS Country Programs,Chief Technology Analyst

Fig. 1. Source: John F. Bookout (President of Shell USA),“Two Centuries of Fossil Fuel Energy”. InternationalGeological Congress, Washington DC; July 10,1985.Episodes, Vol. 12. P. 257–262 (1989).

1860 1900 1940 1980 2020

300

200

100

0

Demandscenario

Millions of barrels per day (oil equivalent)

CoalNon-Fossil

Oil

Gas Tar & ShaleAdd’IO&G

International Scientific Journal for Alternative Energy and Ecology ISJAEE ¹ 10(30) 2005Ìåæäóíàðîäíûé íàó÷íûé æóðíàë «Àëüòåðíàòèâíàÿ ýíåðãåòèêà è ýêîëîãèÿ» ÀÝÝ ¹ 10(30) 200570

© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

and 5) Increasing business interest in the energyfield, with the potential profitable markets forintroducing new sources of energy.

It is important to note, that renewable energyRE technologies (RET), including the proposedhydrogen economy, are well poised to respond tothe above five challenges. RETs are environmen-tally far more benign than fossil fuels. Unlike oiland gas resources, they are evenly distributedthroughout the world and are available to everycountry, and they are easier to protect againstterrorism, because by their very nature they oper-ate as distributed systems.

Renewable energy resources include: wind,solar, biomass, geothermal, hydro and ocean en-ergy. Because of lack of space, in this paper wewill focus on wind, solar and biomass, and onlytouch upon geothermal, hydro and marine sourcesof energy. We will also cover briefly, the use ofhydrogen as the fuel that can meet future globaltransportation needs.

Resource Assessment

In order to estimate the viability of using agiven renewable energy technology, one needs togather data on the availability of the resource it-self, whether it be wind, solar, biomass, etc., Infact, there are certain minima below which thenew technology will not be competitive with fossilfuel sources. For example, at today’s cost of elec-tricity, at 4–10 cents a kWhr, wind will becomeeconomical only if it is available at 300,000 kWhrs/year, or more (Fig. 2).

Same goes for the solar insolation. One needsover 2000 solar hours/year, before one can usesolar hot water or photovoltaic (PV) power to re-place fossil fuels. For each location, careful meas-urements must be taken, over a period of least ayear, plus using meteorological data, covering aperiod of 10 years, before consideration is givenfor the use of wind turbines or solar PV panels.At the National Renewable Energy Laboratory(NREL), computerized mapping techniques exist,based on GIS and meteorological data that can beused to obtain global, mesoscale or microscale dis-tribution of winds and/or solar insolation for anycountry in the world. In addition, NREL has de-veloped software (VIPOR, HOMER and Hybrid 2)that can evaluate the economic feasibility for theuse of any renewable technology, in any location,based on input data that includes the local energyresource, the fossil fuel price (or cost of electrici-ty), the availability of a power grid, etc.

Wind Energy

Of all the RETs, wind energy is the most com-petitive in the present market and has made thewidest penetration, to date; 40,000 MW world wide.In 2003, wind provided 15 billion kWhrs of energyworld wide at an average cost of 5–6 cents/Whr.Germany is the lead country in the use of wind

1860 1900 1940 1980 2020

45

30

15

0

Wind

CO

E c

ents

/kW

h1860 1900 1940 1980 2020

PV

CO

E c

ents

/kW

h

100

80

60

40

20

0

1860 1900 1940 1980 2020

Biomass12

9

6

3

0

CO

E c

ents

/kW

h

Geothermal

1860 1900 1940 1980 2020

CO

E c

ents

/kW

h

10

8

6

4

2

0

Solar

1860 1900 1940 1980 2020

CO

E c

ents

/kW

h

70

60

50

40

30

20

10

0

Fig. 2. The costs of diferent forms of renewable energy

Ýêîëîãè÷åñêèå àñïåêòû èñïîëüçîâàíèÿ àëüòåðíàòèâíîé ýíåðãåòèêè, ýêîëîãèÿ ìåãàïîëèñîâ, ìàëûõ ãîðîäîâ, äåðåâåíü


© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

energy, followed by Denmark, Spain, the UK andthe USA. The new trend for installing wind farms isthe use of very large machines, 1–5 MW per unit,and moving the wind farms, off shore, to conservespace. In addition to larger machines, future inno-vations include: advanced blade materials and man-ufacturing, low speed direct drive generators, cus-tom power electronics, feedback control of drive trainand rotor loads and more flexible structurally. Thetarget O&M cost for the next generation turbines is3 cents/kWhr. As far as their environmental impactis concerned, the only issues are the aesthetics oflarge wind farms near populated areas and bird-kills, especially along bird migration paths.

Solar Thermal Energy

Along with wind energy, the use of solar ther-mal power for hot water is commercially availableand in wide use in temperate climates, such asIsrael and Cyprus. Not so for space heating; toocostly for Northern climates. The main emphasisthese days is on electric power generation usingsolar energy to heat a working fluid, convert it tosteam and run engines or turbines. Three types ofconcentrating solar power technologies are underdevelopment: single-axis tracking parabolic troughsystems, dual tracking dishes, or flat plates withFresno lenses, and power towers (Fig. 3). Troughtechnology is the most advanced of the above threesystems. It has 354 MW of commercial power gen-eration in operation in South West California(Kramer Junction) It operates in a hybrid modewith natural gas, using organic Rankine cycle forpower generation. Plans are to install 1000 MWsystems by 2010, reducing O&M costs from12 cents/kWhr to 4 cents/kWhr.

The dual tracking dish systems employ Bray-ton or Sterling cycle engines at their focus, andcome in 25–30 kW units. The receiver and gener-ator are integrated into a single assembly that ismounted at the mirrored dish. To reduce the costof reflectors, glass is replaced by thin reflectivepolymer membranes stretched across each receiversection, with another membrane stretched on theback, creating a partial vacuum that in turn formsspherical shapes that are ideal for the dish con-centrator. Even the Fresno lenses are made of poly-

acrylic material rather than glass, providing uptot 300 sun concentration. Dish concentrator sys-tems are well suited as distributed power genera-tors. The third dual tracking system is the powertower. The Solar Two, 10 MW systems, with 400heliostats is operational at Dagett California, us-ing molten salt for storage, which is then used toboil water and run a steam turbine. As with theparabolic trough system, power towers can operatein a hybrid mode as solar/fossil plants.

Solar Photovoltaic Energy

Direct conversion of solar energy to electrici-ty, with no moving parts, and no intermediatesteps, makes solar photovoltaic technology (PV)the most desirable energy conversion system. Mono-crystalline or poly-crystalline silicon (c-Si) cellsrepresent over 90 % of commercially available PVsystems. World PV Cell/module production exceed-ed 1 GW in 2004 and is growing at the rate of30–40 % per year. Shortages in the availability ofsolar grade silicon has led to the development ofthin film solar cells such as amorphous Si(a-Si), cadmium telluride cells (CdTe), and gal-lium indium di-selenide cells (CIGS), Also a neweffort is underway for using thin film crystallineSi cells (<100 microns). Of these thin film cells,a-Si cells have the widest commercial applicationat present. The third type of PV cells is the gal-lium indium phosphide/GaAS, multijunction cellsthat operate under 500 suns, with efficiencies ap-proaching 40 %. The most efficient crystalline Sicells are at 25 % and the most efficient thin filmcells are closer to 19 % (CdTe cells). Finally, re-search activities are underway to use organic ma-terials, such as polymers to generate the PV ef-fect. The key parameters for thin films are: highefficiency, availability of abundant, non-toxic ma-terials that are durable and stable.

Because demand of solar cells has always ex-ceeded production (Fig. 4), the cost of cells, perpeak watt has remained in the 3–5 cent range. Costswill come down to competitive levels with wind en-ergy, when continuing improvements of cell effi-ciencies are accompanied by mass production ofthe solar cells. Another major effort is an innova-tive mounting system for PV panels that could be

Fig. 3. Three types of concentrating solar power technologies

Ê. ÒóðüÿíÑîñòîÿíèå òåõíîëîãèé âîçîáíîâëÿåìîé ýíåðãèè â ìèðå


© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

used for roof or faced mounting, retrofit, or newbuild. One such integrated system consists of flex-ible a-Si modules that are mounted onto the tilesthus constituting both a roofing material and pow-er generation unit for the building.

PV cells are energy intensive in their produc-tion, Thus, one important consideration for theuse of photovoltaics, is the energy payback. Forexample, for a 20 % efficient cell, the payback inthe sunbelt region is 2.5 years and in the north-ern regions, closer to 5 years. Just for curiosity,in order to generate the entire electric power needsof the USA (3.3 TW) using PV arrays, with 10 %system efficiency at the consumer, one would needan area of 400 by 400 km (four times the size ofBelgium).

Energy from Biomass

The traditional use of biomass has always beendirect burning of wood and agricultural wastes asfuel. The next two most common approaches arethat of gasifying wood (syngas), or biogas produc-tion from organic material. The next level of so-phistication is the production of ethanol by fermen-tation of sugars. The most common feedstocks arecorn and sugar cane. The obvious advantage ofbiomass is that it can be converted into transporta-ble fuels; gas or liquid. To that end, the feedstockavailable for conversion is: trees, grasses, bio-prod-uct crops, agricultural crops, agricultural residues,animal wastes and municipal solid wastes.

The conversion processes can be: enzymaticfermentation, gas/liquid fermentation, and acidhydrolysis fermentation, and gasification, prod-uct synthesis from syngas, combustion and co-firing. The end products are then: fuels such asethanol, methanol, hydrogen, electricity, heat andchemicals (plastics, solvents, etc.).

Finally, bio-diesel can replace fossil fuel baseddiesel, using vegetable oils, mixed with metha-nol. In the US, 1 % of all commercial trucks run

on bio-diesel, with little or no engine modifica-tions.

Hybrid systems

Renewable resources such as wind, or solar en-ergy, are intermittent or diurnal. When used in astand-alone mode, they require storage. Storing en-ergy from wind and solar, in batteries, flywheels,pumped hydro, are expensive and cumbersome.A more practical approach would be to connect thewind turbine or the PV array to the electric grid,allowing the utility to ‘purchase power’ when it i. e.being generated through wind or solar energy. An-other approach is to use hybrid power systems, withdiesel generators as back up. The advantages aremany. They include: use of local renewable resourc-es; can range in size from small household systems(100 Wh/day) to ones supplying whole areas (10’sof MWhrs/day), and combine many technologies toyield power, tailored to the local resources and thecommunity. Potential components include: PV, windmicro-hydro, river-run hydro, biomass, batteries, andconventional generators (Fig. 5). Under funding fromthe USDOE, NREL has developed several models forconducting options analysis on any hybrid system,

Fig. 4. World PV Cell/Module Production in Megawatts (1988–2002)

550500450400350300250200150100

500

PV array

Fig. 5. Wind/Diesel/PV hybrid system

Wind turbine

Invertor

Generator

DC sourcecenter

Batteries

DC loads AC loads



© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

in any location to determine the economic viabilityof the system. These models can be found on thewebsite, under www.nrel.gov (Homer, Viper andHybrid 2). Using these codes, NREL has sized anumber of hybrid systems for villages in all partsof the world...

Life Cycle Analysis

Because renewable resources are diffuse, inter-mittent and diurnal, it is very important to ensurethat the life cycle of the system is a net energyproducer, with a reasonableenergy payback. The for-mula to be used for this analysis can be given by:

Q(net) = Q(rate of production) –– [Q(energy consumed in operation) + E/T],

where E is the energy invested in its productionand T is the lifetime.

A series of life cycle assessments (LCA) havebeen conducted at NREL on biomass, coal, andnatural gas systems, including hybrid modes, inorder to quantify the environmental benefits anddrawbacks of each (Fig. 6). The results show quiteclearly that overall, biomass power provides sig-nificant environmental benefits over conventionalfossil-based power systems, and they consume verysmall quantities of natural resources and have anet energy balance.

There are four major tracks in the develop-ment and use of hydrogen as the replacementfuel for transportation. production, transport, uti-lization and storage. Developmental work is un-der way on all four tracks, simultaneously. Thetraditional source of hydrogen has been frommethane, using the steam reform process. Thefuture lies in hydrogen production from renewa-ble resources. These include: photoelectrochemi-cal production from water; photobiological pro-duction from algae; from biomass (steam reformprocess using methane from biomass); solar ther-mal hydrogen production, and co-production ofelectricity and hydrogen from renewable technol-ogies, such as wind/PV – electrolysis (Fig. 7).

Fig. 7. Wind/PV – electrolysis

Fig. 6. A series of life cycle assessments

Benefits of a Hydrogen Economy

As with ethanol and methanol, hydrogen wouldbe a key transportation fuel, which roughly con-stitutes 1/3 of the world energy consumption. Forexample, if the US makes full use of hydrogen,from renewable sources, its dependence on oil willbe reduced from 20 million barrels a day to 11million a day. It will give us feedstock diversity,and the power generated can be decentralized, thusmeeting a countries energy security requirements.Environmentally, greenhouse gas emissions willbe removed, and there will be an improvement ofthe local air quality. Finally, hydrogen will reducethe balance of payments for country, like the USthat imports over 55 % of its oil.

Hydrogen, transportation will most probablyutilize the existing natural gas pipelines. As forutilization, intense R&D efforts are under way todevelop PEM (Proton exchange membrane) Hy-drogen fuel cells. These cells combine hydrogenwith oxygen to produce electricity, heat and wa-ter. The potential benefits of fuel cells are signif-icant; however, many challenges must be overcomebefore fuel cell systems will be a competitive alter-native for customers. Cost, performance and du-rability of fuel cell components are key areas thatneed to be addressed.

These components include the PEM membrane,the catalyst, and the bipolar plates. The latter forexample should be lightweight, gas impermeableand amenable to mass production.

Significant improvements over currently avail-able hydrogen storage technologies are required ifhydrogen is to become a viable energy carrier. Com-pact, lightweight carbon adsorbent materials havebecome interesting for possible use in a hydrogenstorage system. Of particular interest are the na-nostructure carbons, such as carbon single-walledand multiwalled nanotubes (SWNT and MWNT)that can store significant amounts of hydrogen atroom temperature (8–10 wt %). These nanotubestacks would then replace the bulky, 5000 psi stor-age tanks and provide adequate storage in exist-ing auto fuel tanks, replacing gasoline with hy-drogen.

Ê. ÒóðüÿíÑîñòîÿíèå òåõíîëîãèé âîçîáíîâëÿåìîé ýíåðãèè â ìèðå


© 2

005 S

cien

tific T

echnical

Cen

tre

«TA

TA»

© 2

005 Í

àó÷í

î-ò

åõíè÷å

ñêèé ö

åíòð

«TA

TA»

Other Renewable Technologies

The renewable energy technologies that wehave not talked about are; geothermal energy; smallhydro and various marine renewables, such as tid-al waves, tidal current turbines and ocean thermalgradient generators.

Work on geothermal energy is ongoing,worldwide. By its very nature, however, geother-mal is highly localized, primarily in regions aroundthe Pacific rim, and in other volcanically activeregions. Today, 8000 MW electricity is being pro-duced from geothermal power, in 21 countries.There are four types of geothermal resources:hydrothermal; geo-pressurized; hot dry rock, andmagma. To extract geothermal power, economi-cally, one needs the overlap of three key parame-ters. These include high permeability strata, andwater saturation at high temperatures (above120 °C). Limited space here will not allow for adetailed treatment of geothermal source of ener-gy. Suffice it to say that costs in cents per kWhr,has decreased form 10–16 cents, down to 5–8cents. Work is being done to improve the tech-nology, reduce drilling costs and expand the re-source base.

Hydro-power plants represent a mature tech-nology. Work is now being concentrated on themodernization of small hydro power plants, rang-ing from a low of 100 kW, to 2 MW. These sys-tems use either the run-of-the river resources orsubmersed dams across the river. The key improve-

ments lie in the production of new turbines with88–90 % efficiencies. The small hydro potentialin Asia, is estimated to be 80,000 MW.

Marine Renewable: tidal waves, ocean currents,ocean waves and ocean thermal gradients are allless developed technologies. England has been lead-ing the development of oscillating wave generatorsand tidal current technologies, with other Europeancountries, Australia and Japan, following suite.Much work was done in the 70’s and 80’s usingocean thermal gradient energy conversion, both off-shore and on-shore. These temperature gradientsare small, about 20 °C, thermodynamic efficienciesare very low, requiring very large structures forgenerating power. Component tests on these sys-tems have been done, primarily by the Japanese, butthey do not constitute a major investment at thistime (unlike oscillating wave energy converters).

Concluding remarks

Increasing demand for oil by developing coun-tries, such as China and India, are placing greatstress on the world demand for oil. In fact, newpredictions place the peak oil production date, closerto 2015 and the peak natural gas production at2020. It is imperative that world emphasis on theuse of renewable technologies and conservationmeasures be given a careful consideration. As men-tioned in the Introduction, five converging factorshave made renewable technologies attractive forexpanded use, with a reasonable target of 20 %use, globally by 2020.


the global status of renewable energy technologiesrenewables.ru/pdf_doc/10_2005touryan.pdf ·...

Documents