13 1 million litr es of HFO per y ear T he en vi r onment wins t oo CO2 emis sions will shrink by about 39 000 t onnes per y ear and on a sunn y day the solar power will allow at least thr ee of the HFO g ener at ors t o be shut down f or maint enanc e during the day with out aff ecting pr oduction T he icing on the cak e S t ansbury said is that by using bat t eries the oper ation will be able t o almost entir ely dispense with the use of the diesel g ener at ors which ar e cur r ently used only in situations that r equir e emer g ency power such as t aking a mill down and quickly r est arting it as they ar e able t o spin up power r apidly t o meet spik es in demand HFO g ener at ors which pr o duc e power at about two thir ds the cost of diesel g ener at ors ar e not as eff icient f o r quick st a rt or emer g ency situations in the same w a y as diesel ones as they t a k e long er t o bring on line and run most eff iciently when used at 85 per c ent of their nominal capacity B2Gold is considering omit ting diesel g ener at ors fr om futur e plant designs even those without solar and using on demand bat t ery power t o t a k e up the slack when nec es sary and then r echar ging the bat t eries with ex c e s s HFO or solar capacity T he solar inst allation at F e k ola will consist of 92 7 36 mono cryst alline pas siv at ed emit t er and r ear c ell PER C solar mod ules 385390 w a t tpeak capacity fr om Canadian Solar arr ang ed in 3 312 string s over 69 4 hect ar es connect ed t o 2 7 6 in vert ers T he arr ays use a single axis tr acking s y st em fr om Arr ay T echnologies that tips the panels up t o maximiz e the amount of solar r adiation they r e c eive at an y given time of day A dual axis tr acking s y st em that also turns panels fr om side t o side w as ev aluat ed but it w as det ermined that the additional complexity and capit al cost as sociat ed with this could not be justif ied E v ery thing is pulled t o g ether and contr olled by an int egr at ed contr ol s y st em that is being developed t o combine W a rt sila s GEMS s y st em with the existing supervisory contr ol and dat a acquisition SCAD A s y st em being used t o curr ently run the HFO plant T his int egr at ed contr ol s y st em count ers power spik es allows st artup of milling equipment without f iring up additional engines and permit s oper ations t o maximiz e the time HFO engines ar e down T he s y st em also allows f or r emot e monit oring of the power st ation As solar output incr eases in the morning g ener at ors can be shut down minimizing wear and fuel con sumption T he aut omat ed s y st em compensat es f or is sues with g ener at ors even in the middle of the night f eeding bat t ery power t o k eep pr oduction running unint errupt ed B2Gold r elied on two German r enew able ener gy companies Suntr ac e which w as the pr oject lead and Bay W a r e t o do the pr oject analysis engineering designs lay out s f inal cost esti mat e and pr ocur ement ev aluations As the pr oject pr ogr es ses their employ ees will also as sist with sit e inst allation commis sioning and tr aining of the solar plant oper at ors T racking the weather T he f inal piec e is a weather f o r e casting s y st em by Reuniw at t that allows oper at ors t o f i gur e out how much sunshine and ther ef or e how much solar power t o expect on an y given day It even includes cloud det ection capabilities If y ou ha ve a day when y o u ve g ot some sunshine and then y o u ve g ot some clouds and y o u r e trying t o pr oduc e a signif i cant amount of y our power with solar y ou ha ve t o k eep what we call spinning r eserve online S t ansbury explained What that means is if the cloud bank thick ens a lit tle bit the pr oduction fr om y our solar panels is g oing t o dr op Y ou ha ve t o mak e sur e that y ou ha ve enough HFO g ener at ors online that they can pick up that diff er enc e So on a cloudy day let s say y ou r eally need two g ener at ors running at 85 per c ent eff iciency that s kind of the s w eet spot and y our solar is picking up the r est of it But if y o u ve g ot a cloudy day y ou pr obably ha ve t o run thr ee engines because y ou need that spinning r eserve t o pick up an y dr op that y ou might ha ve in the solar pr oduction because of clouds or an y other int erruptions W ith the bat t ery s y st em y ou don t need t o do that y ou just run the two engines y ou need If ther e s a period of time wher e additional power is r equir ed the bat t ery supplies that power so it allows y ou t o run y our fuel engines much mor e eff iciently because y ou ha ve the bat t eries as part of y our s y st em T h at sa ves a lot of money sinc e the HFO engines do not run eff iciently at 60 t o 65 per c ent capacity It is har der on them as they do not achieve complet e combustion of the fuel Running them at a f airly high load minimiz es the amount of fuel con sumed per kilow a t t hour and is easier on them fr om a maint e nanc e point of view T he bat t eries r echar g e onc e r equir ement s abat e using ex c e s s output fr om either the solar or HFO g ener a t o rs as it is a v ailable B2 Gold is developing sever al other deposit s near the F e k ola oper ation W ith the addition of solar power at F e k ola it may be pos sible t o power other smaller pr oc es sing plant s fr om the c e n tr aliz ed F e k ola power inst allation and do so at a lower cost than other power supply options T he logic of k eeping all of the power g ener ation capacity in one plant mak es a tr emendous amount of sense So we r e looking at w a ys that we can expand the solar component and pr obably expand the bat t ery compo nent t o the plant if we wer e t o add additional pr oduction f acili ties in the ar ea said S t ansbury CIM MayJune 2020 MaiJuin 2020 37 ener gy efciency The seven megawatt solar power plant at B2Gold s Otjikoto Mine is ser ving as a model for the one at Fekola Courtesy of Christian Stiebahl