The cou­pling of re­new­able en­er­gy with de­sali­na­tion has un­der­stand­ably cre­at­ed a re­al glob­al buzz. Af­ter all, it’s a match that’s meant to be (like a long en­gage­ment with­out the wed­ding). The de­sali­na­tion mar­ket is try­ing to shift its lega­cy im­age of pro­vid­ing pure wa­ter (potable drink­able wa­ter) as­so­ci­at­ed with the high en­er­gy cost. Part­ner­ing with clean­er and sus­tain­able en­er­gy sources is al­ways a good way to do so.

Merg­ing Re­new­able En­er­gy and De­sali­na­tion has been dis­cussed at length from pre­vi­ous Caribbean Wa­ter and Waste­water As­so­ci­a­tion (CWWA) con­fer­ences. Bring­ing to­geth­er these two (re­new­able en­er­gy and de­sali­na­tion) with­out a ma­jor break­through of a large-scale, in­de­pen­dent­ly pow­ered projects com­ing on­line can solve much of the wa­ter re­sources is­sues fac­ing the Caribbean.

par­tic­u­lar­ly suit­able in­stru­ment in sup­port­ing Small Is­land De­vel­op­ing States (SIDS) in adapt­ing to the con­se­quences of cli­mate change con­sists of in­vest­ing in the de­vel­op­ment and es­tab­lish­ment of ef­fi­cient re­new­able en­er­gy-de­sali­na­tion in­fra­struc­ture. These kinds of in­vest­ments can not on­ly in­crease wa­ter re­silience but al­so pro­mote a much-need­ed syn­er­gy be­tween these in­ex­tri­ca­bly linked re­sources (en­er­gy and wa­ter) whilst strength­en­ing the co­op­er­a­tion be­tween the pub­lic util­i­ties.

To­day, the ma­jor­i­ty of the Caribbean’s econ­o­my with the ex­cep­tion of T&T is en­tire­ly de­pen­dent on diesel fu­el or nat­ur­al gas. For decades, res­i­dents of Union Is­land (part of St Vin­cent and the Grenadines) had to en­dure ex­ces­sive noise and air pol­lu­tion that came with diesel pow­er plants as well as coat­ings of black soot over homes.

The Caribbean re­gion is ide­al for ex­po­nen­tial growth in the re­new­able en­er­gy sec­tor. Un­for­tu­nate­ly, re­new­able en­er­gy still plays on­ly a mi­nor role in the Caribbean’s en­er­gy gen­er­a­tion, even thou the re­gion’s con­di­tions are ide­al for lever­ag­ing green sus­tain­able en­er­gy. Sun (so­lar en­er­gy) and wind are abun­dant, in ad­di­tion to ge­ot­her­mal en­er­gy and hy­dropow­er sys­tems with the abil­i­ty to free all Caribbean is­lands en­tire­ly from fos­sil fu­els. In the Caribbean re­gion, so­lar pow­er is ad­van­ta­geous not on­ly be­cause of abun­dant sun­light but al­so be­cause so­lar en­er­gy sys­tems have seen a tremen­dous drop in in­stal­la­tion prices and on­go­ing main­te­nance costs. Map­ping wa­ter needs with re­new­able en­er­gy sources will be a strate­gic tool for plan­ning any Caribbean coun­try’s new de­sali­na­tion sys­tems. Re­new­able en­er­gy-pow­ered de­sali­na­tion can be a key en­abler for con­tin­ued growth es­pe­cial­ly for coun­tries that re­ly on wa­ter for in­dus­tri­al use, agri­cul­ture and/or ir­ri­ga­tion.

As such, re­new­able en­er­gy gen­er­a­tion should be seen by gov­ern­ments and pub­lic util­i­ties across the Caribbean as a valu­able eco­nom­ic in­vest­ment that re­duces ex­ter­nal, so­cial, en­vi­ron­men­tal and op­er­a­tional costs. Gov­ern­ment agen­cies and the pri­vate sec­tors may, there­fore, wish to take the evolv­ing mar­ket op­por­tu­ni­ties and long-term im­pacts of de­sali­na­tion tech­no­log­i­cal op­tions in­to con­sid­er­a­tion when plan­ning their ca­pac­i­ty, in­fra­struc­ture, and sus­tain­able wa­ter sup­ply de­mands.

The dom­i­nant de­sali­na­tion process­es used across the globe to­day are based on Re­verse Os­mo­sis (RO) and Mul­ti-Stage Flash (MSF) which con­sti­tute 60.0 per cent and ap­prox­i­mate­ly 27 per cent of the world­wide ca­pac­i­ty, re­spec­tive­ly. The fea­si­bil­i­ty of each tech­nol­o­gy de­pends on spe­cif­ic con­di­tions such as en­er­gy prices, wa­ter qual­i­ty and the tech­ni­cal re­sources of the re­gion. Ther­mal de­sali­na­tion process­es such as Mul­ti-Stage Flash (MSF) in­volves dis­til­la­tion where­by saline feed-wa­ter (typ­i­cal­ly sea­wa­ter) is heat­ed to va­por­ise, caus­ing fresh wa­ter to evap­o­rate and leave be­hind high­ly saline so­lu­tions (the brine). Fresh­wa­ter is then ob­tained from vapour cool­ing and con­den­sa­tion.

Fur­ther, mem­brane de­sali­na­tion in­cor­po­rates mem­branes to sep­a­rate fresh wa­ter from saline feed-wa­ter. The feed-wa­ter is brought to the sur­face of the mem­branes, which se­lec­tive­ly pass­es wa­ter mol­e­cules through and ex­cludes the salts. Dur­ing Re­verse Os­mo­sis (RO), the sea­wa­ter pres­sure is in­creased above the os­mot­ic pres­sure, thus al­low­ing the de­sali­nat­ed wa­ter to pass through se­mi-per­me­able mem­branes, leav­ing salt par­ti­cles be­hind.

De­sali­na­tion process­es such as Re­verse Os­mo­sis (RO) or Mul­ti-Stage Flash (MSF) dri­ven by the use of re­new­able en­er­gy (so­lar, wind, ge­ot­her­mal and hy­dropow­er sys­tems) can pro­vide a sus­tain­able way to pro­duce fresh wa­ter for some Caribbean re­gions. It is an eco­nom­i­cal­ly at­trac­tive op­tion as the costs of re­new­able en­er­gy tech­nolo­gies con­tin­ues to de­cline and the prices of fos­sil fu­els re­main un­sta­ble.

Us­ing lo­cal­ly avail­able re­new­able en­er­gy re­sources for de­sali­na­tion (ei­ther Re­verse os­mo­sis or Mul­ti-Stage Flash (MSF) process­es are high­ly like­ly to be a cost-ef­fec­tive so­lu­tion par­tic­u­lar­ly in Caribbean re­gions with poor in­fra­struc­ture for fresh­wa­ter trans­mis­sion and dis­tri­b­u­tion. As­sess­ing the tech­ni­cal fea­si­bil­i­ty and cost ef­fec­tive­ness of re­new­able de­sali­na­tion plants re­quires de­tailed analy­ses, in­clud­ing a va­ri­ety of fac­tors, such as lo­ca­tion, qual­i­ty (salin­i­ty) of feed-wa­ter in­put and fresh-wa­ter out­put, the avail­able re­new­able en­er­gy source, plant ca­pac­i­ty and size, and the avail­abil­i­ty of grid elec­tric­i­ty.

The right com­bi­na­tion of a re­new­able en­er­gy source with a spe­cif­ic de­sali­na­tion tech­nol­o­gy can be the key in match­ing both pow­er and wa­ter de­mands across the Caribbean re­gion eco­nom­i­cal­ly, ef­fi­cient­ly and in an en­vi­ron­men­tal­ly friend­ly way.

Dr Ki­ran To­ta-Ma­haraj

Head of Civ­il and En­vi­ron­men­tal En­gi­neer­ing

Cen­tre for Wa­ter, Com­mu­ni­ties and Re­silience(CW­CR)

Uni­ver­si­ty of the West of Eng­land, Bris­tol (UWE Bris­tol)

Email: Ki­ran.To­ta-Ma­haraj@uwe.ac.uk