IT IS ALL ABOUT THERMAL ENERGY STORAGE

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1 IT IS ALL ABOUT THERMAL ENERGY STORAGE Bo Nordell Dept. of Civil nd Environmentl Engineering Luleå University of Technology SE Luleå, Sweden, ABSTRACT The globl ir temperture increse is n indequte mesure of globl wrming, which should be considered in terms of energy. The ongoing globl wrming mens tht het hs been ccumulting since 1880, in ir, ground, nd wter. Before explining this wrming by externl het sources the net het emissions on Erth must be considered. Such emissions, from e.g. the globl use of fossil fuel nd nucler power, must contribute to globl wrming. The im of this study ws to compre globlly ccumulted nd emitted het. The het ccumulted in ir corresponds to 6.6% of the globl wrming, while the remining het is stored in the ground (31.5%), melting of (33.4%), nd se wter (28.5%). Emitted net het corresponds to 74% of ccumulted het, during the sme period. The missing het (26%) must hve other cuses; e.g. the result of incresing CO 2 concentrtion into the tmosphere. 1. INTRODUCTION Globl men tempertures hve been compiled bsed on long-term ir temperture mesurements [NCDC-NOAA, 2007]. These tempertures (Fig 1) re seprted into one monthly Se Surfce Temperture (SST) nd one monthly Lnd Are Temperture (LAT). The globl men temperture is the re weighted men of LAT nd SST. In 1880, SST ws 15.9 o C nd LAT ws 8.6 o C, with globl men of 13.6 o C. Until 2000, SST hd incresed by 0.5 o C nd the LAT 1.2 o C. The corresponding globl men temperture increse ws 0.7 o C. However, the globl men ir temperture increse is indequte mesure of globl wrming, nd independent of wht cuses the wrming it should be considered in terms of energy [Pielke et.l., 2004; Pielke. 2005]. Here, globl wrming is considered s the globl energy ccumultion in ir, ground, nd wter, since Before explining the globl wrming by extrterrestril het sources, the net het emissions on Erth should be considered. Such emissions, het dissiption from the e.g. globl use of fossil fuel nd nucler power, must contribute to globl wrming. In current study, ccumulted nd emitted het were estimted nd compred. Fig. 1. Globl Lnd Are Temperture (LAT) nd Se Surfce Are Temperture (SST), [NCDC-NOAA].

2 2. GLOBAL HEAT ACCUMULATION Performed clcultions include the period The methods used to clculte het ccumultion in the ir, ground nd wter re described in Appendix A nd in [Nordell nd Gervet, 2009]. 2.1 Het Accumultion in Ground As result of the incresed ir temperture lso the ground surfce hs wrmed up nd het hs been conducted into the ground. The het content of the ground incresed by 23.4 kwh m - 2 from 1880 to This het conduction into the ground neither occurs in permfrost res, defined s perennil ground, nor on glcier or icings [NSIDC, 2007]. Such res, which re ffected differently by the globl wrming, re included in the melting of nd its contribution to the se level rise. Glcited res ( m 2 ) [Singh nd Singh, 2001] nd permfrost res of the world ( m 2 ) thus reduce the totl lnd re ( m 2 ) ffected by the heting to m 2. The totl ground het ccumultion since 1880 then becomes kwh. 2.2 Het Accumultion in Air The het ccumultion in ir (moist sttic energy) ws estimted seprtely for over the se surfce nd lnd surfce. Hence, different men ir tempertures over se nd lnd were considered. The totl het ccumultion in ir is kwh of which 44.6% is distributed over the lnd re. 2.3 Het Accumultion in Wter The het ccumultion in ocen wter ws estimted from the globl se level rise (GSLR), compiled by the Permnent Serv for Men Se Level [PSMSL, 2007]. The GSLR is result of vrious fctors; e.g. melting lnd, therml expnsion, incresing wter vpor in ir, permnent removl of wter from quifers, deforesttion nd loss of soil moisture, reduction in the extent of wetlnds, deep infiltrtion of irrigtion wter, nd ocen sedimenttion. [Hrvey, 2000] There re vrious dt regrding the contribution of therml expnsion to the 20 th century se level rise. The most commonly suggested therml volume expnsion rte is presently 0.5 mm per yer [Church et.l., 2001, Antonov et.l., 2002]. Recent studies show considerbly lower vlues [Ishii et.l. 2003] nd it is reported tht the ocen wter hs been cooled for severl yers [Lymn et.l. 2006]. Stellite mesurements show tht lrge-scle El Nino like ocen temperture fluctutions occurred between 1955 nd 1995 [Ishii et.l. 2003]. Such fluctutions nd the recently reported ocen temperture decrese is result of lrge-scle nd long-cycled (~15 yers) ocen circultion, leding to melting of se nd subsequent cooling of the wter. Bsed on the temperture fluctutions between 1955 nd 1995 therml expnsion rte of 0.02 mm yer -1 ws estimted [Ishii et.l. 2003]. Since this expnsion, i.e. 1 mm over the lst 50 yers, is result of globl wrming the expnsion until 1955 is neglected. Assuming tht the se wter heting occurred in the top 1,000 m of wter, this 1 mm therml expnsion corresponds to kwh of het. Recent estimtes of the totl se level rise due to the melting of smll glciers nd Greenlnd is bout 60 mm. Here, this contribution ws estimted to bout 50 mm until The min uncertinty is whether the mss of Antrctic is decresing or incresing, i.e. cuses the se level to rise or not [Hrvey, 2000]. If the mss of on Antrctic increses, the totl melt het will be correspondingly less. The energy required to melt glciers nd permfrost, totling 50 mm se level rise, is kwh. The totl re of se is m 2 of which m 2 is floting on the northern hemisphere. The estimted nnul melting ws 0.38%±0.02% on the northern

3 hemisphere nd 0.02%±0.48% [NSIDC, 2007b] on the southern. During the sme period the totl thinning of the 3 m thick ws estimted to 4% [Johnnessen et.l. 2003]. Here, vlues for the northern hemisphere re used, while the very uncertin vlues for the southern hemisphere re disregrded. The resulting nnul melting of 258 km 3 se requires kwh yer -1, during The totl se melting during the lst 120 yers is considered proportionl to the energy consumption during the sme period, see Fig 3, resulting in the melting of 10 4 km 3 of se nd corresponding het bsorption of kwh. The totl het ccumultion in ocen wter during , i.e. by heting of se wter nd melting of lnd nd se, then dds up to kwh. The globl het ccumultion in the ir, ground nd wter during is thus kwh ( J). This het is distributed in ir (6.6%), ground (31.5%), wter (28.5%), nd melting of lnd nd se (33.3%) ccording to Fig 2. It is notble tht the het content in ir only corresponds to 6.6% of the globl wrming. Fig. 2. Totl globl wrming i.e. het ccumultion in ir, ground, nd wter/ since 1880.The totl het ccumultion is kwh ( J). 4. GLOBAL NET HEAT GENERATION The mjor nturl het source is the geotherml het flow but het is lso generted by, e.g. volcnic eruptions, erthqukes, nd meteorites. Non-nturl het sources include the globl use of fossil fuel, nucler power, nd deforesttion. Het emissions from nucler bomb tests nd conventionl bombs lso dd to the net het genertion. Fig. 3. Annul World Consumption of Commercil Non-Renewble Energy, [CDC, 2007]. 4.1 Commercil Energy The world s consumption of commercil non-renewble energy from 1880 to 2000 [CDIAC, 2007; EIA, 2007] is shown in Fig 3. The totl commercil energy consumption is kwh ( J). All this energy dissiptes into het. A useful key vlue is tht the globl energy consumption in 2000 ws pproximtely kwh ( J).

4 4.2 Volcnoes nd Erth ukes An verge of 1.4 million erthqukes occurs ech yer on Erth. Almost ll o these re considered prt of nturl net heting. The therml energy relesed from few lrge volcnic eruptions during the lst 120 yers ws estimted bsed on [Simkin nd Siebert, 1994]. 4.2 Nucler Bomb Tests nd Conventionl Bombs More thn 2,000 nucler tests, tmospheric nd underground, were crried out, Though nucler explosions hve gret power, relesed energy ws smll becuse of its short durtion. Energy relesed by conventionl bombs ws lso investigted. It ws found tht bomb explosions do not men ny significnt net heting. 4.3 Non-commercil Fossil Fuel Consumption Fossil fuel consumed outside the energy mrket is not included in globl energy sttistics. Exmples of such non-commercil energy re, for exmple flres t gs nd oil fields, fires t col fields nd in underground col mines, nd petroleum products tht re not used in energy production e.g. in the production of plstics. Also deforesttion contributes to net heting. 4.4 Gs Flring Flring of ssocited gs ws common industry prct in the erly "decdes" of oil production, when there were virtully no gs mrkets, or concerns regrding the environment or rtionl use of hydrocrbon resources. The gs flring in Afric lone is presently equivlent to hlf of tht continent s power consumption. Fewer thn 20 countries ccount for more thn 85 percent of gs flring nd venting. The mgnitude of this problem is underlined by the World Bnk s The News Flre [GGFR, 2007; WB, 2007], which is devoted to reducing the globl gs flring. 4.5 Underground Col Fires Hundreds of col fields re burning out of control round the world. Some of the oldest nd lrgest col fires occur in Chin, the United Sttes, nd Indi [Strcher nd Tylor, 2004]. Those burning underground cn be difficult to locte nd re not included in this net het estimtion. 4.6 Deforesttion The deforesttion since 2000 is 200 km 2 /dy nd the globl forest re hs bee reduced by 11.1 Mkm 2 since Here, it ws ssumed tht this wood ws burnt or decomposed. 4.7 Nucler Power Since the men efficiency nucler electricity is 33% the resulting het emission is tw s high t generted electricity. Wste het from nucler power plnts mens smll shre of the globl het emissions but hs lrge impct loclly. Sweden s nucler power plnts e.g. generte 70 TWh e. Thus, 140 TWh of wste het is emitted into the se wter. This mount of het is 40% greter thn the nnul spce heting demnd of ll buildings in Sweden. A summry of the net het genertion is given in Tble 1. The min prt (~70%) of the net het emissions ( kwh) results from of the commercil consumption of oil, gs, col nd nucler power, while other non-renewble het sources totls kwh nd miscellneous het sources (volcnoes, erth qukes etc.) mens kwh. The globl net het genertion between 1880 nd 2000 ws kwh ( J).

5 Tble 1: Globl Net Het Genertion, Het Genertion Rtio Commercil Non-Renewble Energy Consumption (10 14 kwh) (10 18 kj) (%) Crude oil Gs Col Nucler TOTAL Other Non-Renewble Het Sources Gs flring Col fires Deforesttion Production of plstics Wste Het from Nucler Power TOTAL Miscellneous Het Sources Volcnoes Erthqukes Nucler tests Wrs (bombs) TOTAL TOTAL: NET HEAT EMISSION TOTAL: ACCUMULATED HEAT MISSING HEAT CONCLUDING REMARKS Independent of wht cuses the globl wrming it should be considered s energy ccumultion on Erth. Performed estimtions of globl het ccumultion in ir, ground, nd globl net het emissions include the yers from 1880 to It ws found tht the ir only contins 6.6% of globlly ccumulted het. The remining het (Figure 4) is ccumulted in ground (31.5%), se wter (28.5%), se melt (11.2%) nd lnd melt (22.2%), The net het emissions contributes to 74% of the globl wrming. The missing het (26%) must hve other cuses, e.g. the greenhouse effect, nturl vrition of the climte, nd/or underestimtion of net het emissions. Performed clcultions re conservtive i.e. both the globl het ccumultion nd the het emissions re underestimted. The underestimted het ccumultion mens tht the missing het in Fig. 4 is too high. Also the underestimtion of net het emission gives the sme result. Fig. 4. Globl Wrming nd Het Sources. The circle represents the globl wrming i.e. the globl het ccumultion It is seen tht 74% of the wrming is result of het emission while the remining 26% (missing het) must hve other cuses. Most mesures lredy tken to combt globl wrming re beneficil lso for current explntion. Renewble energy should be promoted insted of using fossil fuels. However, CO 2 sequestrtion nd subsequent storge will hve very little effect on the globl wrming. It is lso concluded tht nucler power is not solution to globl wrming but prt of the problem.

6 Methods used APPENDIX A Het ccumultion in ground: It ws ssumed tht the temperture of the ground surfce ws equl to the globl lnd re temperture (LAT), see Fig. 1, nd tht the men therml properties of the ground nd geotherml het flow re known. Becuse of the incresing ground surfce temperture het is conducted from the ground surfce into the ground. The ground temperture chnge ws determined by one dimensionl het conduction: 2 T 1 2 z α T t = 0 (1) where T is the ground temperture, t time, λ the therml conductivity of the ground, α =λ/c v the therml diffusivity, C v the volumetric het cpcity of the ground, nd z the verticl direction. Eq. (1) ws numericlly solved for T(z=0)=LAT(t) nd T(z=400)=C, time step of 0.5 h during 120 yers, nd length step of 0.1 m. A ground therml conductivity of 2.5 W m -1 K -1, volumetric het cpcity of 0.6 kwh m -3 K -1, nd geotherml het flow of W m -2 were ssumed. The resulting het ccumultion in the ground () cused by the temperture chnge ΔT(z) fter 120 yers of globl wrming ws clculted by: g 0 = C ΔT(z) z (2) D v D is ny depth t which the ground temperture is undisturbed by the globl wrming. Eq. (2) ws solved for the boundry conditions used bove. In performed clcultions, sufficient D=400 m ws used since the temperture disturbnce did not rech below depth of 270 m. Het ccumultion in ir: In clculting the het ccumultion in ir, its temperture profile ws ssumed liner from the ground surfce to height of 5,500 m, where the Erth s effective temperture occurs (-18.8 o C) [Slby, 1996]. The men reltive humidity ws ssumed unchnged from 1880 to It ws estimted to be 62%, fter re weighting of dt for different ltitudes [CDC, 2007]. The clcultions were seprted into two ir volumes, i.e. ir over se nd lnd surfce. The het content of ir (moist sttic energy) over se surfce nd lnd surfce, s + l, is expressed by: H s o = A C ρ (z) ΔT (z) z + L Δm (z) z + A C ρ (z) ΔT (z) z + L Δm (z) z (3) p s where C is the specific het of dry ir (J/kg, o C), Δ T ( o C) is the ir temperture chnge, L is the ltent het of vporiztion (J/kg), Δm the bsolute humidity (kg/m 3 ). A s nd A l represent the se surfce re nd lnd surfce re. Het required for melting: The het required to melt is lso seen s kind of het ccumultion. Performed clcultions re bsed on estimted volumes of melted lnd, se, nd permfrost from It ws lso ssumed tht melted is blck, i.e. trnsprent 3 with density of ρ = kg / m with ltent het (melt het) of L =334 kj/kg. The totl mount of energy required to melt V (m 3 ) of is then given by: H l o p l l V ρ L = (4) Het ccumultion in se wter: The het ccumultion in se wter is the totl chnge in sensible het i.e. the het required to wrm up the wter. This heting is indirectly estimted from estimtions of the volume expnsion of heted wter. The volume expnsion ΔV is given by; V = α V o Δ T Δ (5)

7 Where α is the therml coefficient of ocen with slinity of 35 ppm. Since α is reltively liner the estimted se level increse s result of therml expnsion ( Δ V ) Eq.(5) gives the temperture increse ( T ) is Δ ) of the se wter. The corresponding sensible het ccumultion in se wter ( sw thus given by; sw 1000 = C ΔT(z) z (6) 0 nd the totl het ccumultion in the ocen wter is thus + s sw w becomes; = (7) Totl het ccumultion: The totl globl het ccumultion is given by the sum of het ccumultion in ir, ground, nd sewter; + + totl = (8) g s Error estimtion APPENDIX B Net Het Genertion: Included net het genertion is relible i.e. ll net het included is relly emitted, see Tble 1. The mjor prt Commercil Energy Consumption is s good s interntionl energy sttistics. Other non-renewble het is underestimted since e.g. underground col fires were excluded nd tht deforesttion does not include reduced biomss in norml forestlnd. The min uncertinty is in Miscellneous Het Sources or rther het emissions from erthqukes nd volcnoes. Even though only few such rre events were included it could be questioned if some of these should be seen s prt of bckground heting, which mens tht they should not be included. All together it is estimted tht the globl het emissions re underestimted by less thn 10%. Globl Het Accumultion: Het ccumultion in ir is relible s the globl temperture chnge reported by NCDC. The het ccumultion into the ground is underestimted since the globl men vlue for the ground therml conductivity ws ssumed t 2.5 W/m,K, which corresponds to crystlline bedrock from the ground surfce nd downwrds. In res with 10 m soil cover (~1 W/m,K) or sedimentry bedrock the resulting therml conductivity would rther be 2.0 W/m,K which would reduce the totl het ccumultion in the ground by 6.3% of the totl het ccumultion. Het bsorbed my se melting until 2000 ws overestimted since the melted re ws ssumed to hve the men thickness of 3 m. In more recent studies it ws ssumed tht the thickness of melted re ws linerly thinner to 0 t the edge of the field. For tht reson the clculted mss of se ws too high, which reduces the totl het ccumultion by 5.6% (Figure 2). The min uncertinty in this estimtion is the sensible het ccumultion in se wter becuse of the vrious estimtions nd mesurements of se wter temperture. In current study, mesurements (estimtions) tht give the se wter temperture over the longest period (~50 yers) were chosen. Even though the wrming of se wter is the min uncertinty in performed clcultions I see no relible wy to estimte this error nd this prt is therefore left unchnged. Assuming tht this estimtion of the uncertinty of used dt is correct the net het genertion would mximlly be incresed by 10% nd the globl het ccumultion decresed by 11.9%. These mximum errors ll together reduce the mount of missing het (unexplined heting) from 26% to 5.5%, which mens tht lmost ll of the globl wrming would be explined by net het emissions.

8 ACKNOWLEDGEMENT Performed reserch hs depended on students, who over severl yers mde different substudies on this subject; Sergi Ms Miret (Globl Het Storge), Lr Nunes de Crvlho (Nucler Tests), Ann-Mrie Alkngs nd Susnne Lmberg (Wrs, Meteorites nd Erthqukes), Nicols Pget (Volcnos), Hubert Boulnger nd Dmien Orcel (Se Level Rise), Dr. Jules Dim for his overview on the subject, nd Dr. Görn Hellström for vluble comments. Severl of the performed sub-studies were repeted by even more students. I m most grteful to ll of them. REFERENCES Antonov J.I., Levitus S., nd Boyer T.P., Steric se level vritions during : Importnce of slinity. J. Geophys. Res. 107 (C12):8013. CDC, The Climte Dignosis Center, CDIAC, US Crbon Dioxide Informtion Anlysis Center, Church J.A., Gregory J.M., Huybrechts P., Kuhn M., Lmbeck K., Nhun M.T., in D., Woodworth P.L., et.l., Climte Chnge 2001: the Scientific Bsis. Chp 11. Chnges in Se Level. 3 rd Assessment Report of the IPCC. Cmbridge Univ. Press, Cmbridge. EIA, US Energy Informtion Administrtion Gervet B., Het Emissions from Gs Flring, Col Fires, Deforesttion, nd Plstics. Luleå University of Technology. GGFR, The News Flre. GGFR Globl Gs Flring Reduction. Hrvey L.D.D, Climte nd Globl Environmentl Chnge, Prent Hll, Hrlow. Ishii M., Kimoto M., nd Kchi M., Historicl ocen subsurfce temperture nlysis with error estimtes. Monthly Wether Review 131, Lymn J.M., Willis J.K., nd Johnson G.C., Recent Cooling of the Upper Ocen. Geophys. Res. Letters 33, L18604, doi: /2006gl NCDC-NOAA, Globl Surfce Temperture Anomlies. Nordell, B., Gervet B., Globl Energy Accumultion nd Net Het Emission. Int. Journl of Globl Wrming. (Accepted for publiction) NSIDC, Ntionl Snow nd Ice Dt Center. Frozen Ground Dt Center. NSIDC, 2007b. Ntionl Snow nd Ice Dt Center. Johnnessen O.M., Bengtsson L., Miles M., Kuzmin S., Semenov V.A., Alekseev G.V., Ngurnui A.P., Pielke R.A., Het Storge Within the Erth System. Forum, Americn Meteorologicl Society, p Pielke R.A., Dvey C. nd Morgn J.A, Assessing globl wrming with surfce het content. EOS. Americn Geophysicl Union. 85: PSMSL, Permnent Serv for Men Se Level, Slby M.L., Fundmentls of Atmospheric Physics. Acdemic Press, New York. Simkin T., nd Siebert L., Volcnoes of the World, 2nd Ed: Geoscience Press /Smithsonin Inst. Globl Volcnism Progrm, Tucson. Singh P. nd Singh V.P., Snow nd Glcier Hydrology. Kluwer Acdemic Publishers. Dordrecht. Strcher G.B. nd Tylor T.P., Col fires burning out of control round the world: thermodynmic recipe for environmentl ctstrophe. Interntionl Journl of Col Geology 59: 7 17(2004). WB, The World Bnk. Globl Gs Flring Reduction Inititive. Report World Bnk Group.