The Economist - USA (2019-11-30)

The EconomistNovember 30th 2019 Science & technology 71

2

O

n theprinciplethatnonewsis

goodnews,thefactthataidshas

droppedoutoftheheadlinesissurelya

goodthing.Nevertheless,it doesno

harmfortheworldtoberemindedfrom

timetotimethattheillnesshasnotgone

away.Tothatend,unaidsandtheWorld

HealthOrganisation,theinternational

agencieschargedwithdealingwiththe

epidemic,promoteDecember1stas

WorldaidsDay.

Thisyearisthelastbeforethetarget

dateforthesuccessofthelatestofthe

agencies’campaignstorollouttheanti-

retroviraldrugsthatbothkeepthose

alreadyinfectedwithhivaliveandstop

thempassingtheviruson.Thispartic-

ularcampaigniscalled90-90-90.Its

aimsarethat,bytheendof2020,90%of

allthosearoundtheworldwhoarein-

fectedwillknowtheyareinfected;90%

ofthatgroupwillbereceivingsustained

antiretroviraltherapy;and90%ofthose

receivingtherapywillhavehadthevirus

effectivelysuppressed.

The90-90-90campaignfollowsthe 3

by5 initiative,begunin2003,toput3m

peopleonthedrugsby2005,andthe

subsequenttargetof 15 by15.Thelatest

estimateisthat38mpeopleareinfected

withhiv, so90-90-90implies28mbeing

treatedsuccessfully.Asthechartshows,

doingthisby 2020 isunlikely.Whether

thatisseenasa failure,though,depends

onyourpointofview.Hadthetarget

beenreachedeasilyiswouldsurelyhave

beencriticisedasunambitious.

Regardlessofwhen90-90-90is

achievedthenextaim,95-95-95,isal-

readypencilledinfor2030.Thisisalso

theyearsetbytheun’s SustainableDe-

velopmentGoalsfortheendofaidsasa

publichealththreat.

Theexactmeaningofthatphraseis

unclear.Butinprincipleeliminatinghiv

ispossiblewithexistingtechnology.As

hashappenedwithsmallpoxandpolio,

theidentificationandtreatmentofall

whoareinfectedwouldstopnewcases

arising.Theslogansforthisare“zero

newhivinfections”,“zeroaids-related

deaths”and(aidsbeinganillnessthat

hasalwaysbeensurroundedbypreju-

dice)“zerodiscrimination”.

Unlikesmallpoxandpolio,however,

thereisnovaccineagainsthiv. If this

stateofaffairscontinues,eliminating

theviruswillmeangivingdrugstoall

thoseinfecteduntiltheyhavediedof

othercauses.It willalsomeansomeone

payingforthosedrugs.And,inthecase

ofthoselivinginthepoorestpartsofthe

world,that“someone”isoftengoingto

betaxpayersinrichcountries,who

alreadycontributeabout$8bna yearto

theanti-aidseffort.Exterminatinghiv,

then,willbea hugeundertakingandan

expensiveone.Butnot,withluck,an

impossibleone.

Remember,remember

AIDS

Slowly,AIDSisbeingbeatenback

Dispatchesfromthebattlefront

Source:UNAIDS 2019 estimates

NewcasesofHIV,worldwide,m

2000 05 10 15 18

4

3

2

1

0

AwareofHIVstatus

2000 05 10 15 18 20

100

80

60

40

20

0

Viralload

suppressed

UNAIDS90-90-90

targetsfor 2020

Receiving

antiretroviral

treatment

Treatmentstatus

%ofHIV-positivepopulation

3 by 5

UNAIDSinitiativeslaunched:

15 by 15 90-90-90

run for their money: liquid air.

At a temperature of -196°C, all of air’s

component gases will liquefy. Doing this is

a routine, electrically driven industrial

procedure. Storing liquefied gases in bulk

is also a routine piece of engineering. The

result occupies a 700th of the volume of

those gases at room temperature—so,

when liquid air is warmed and allowed to

expand, it does so forcefully. Using a device

called a Dearman engine (after its inventor,

a Briton named Peter Dearman), that force-

ful expansion can be employed to spin tur-

bines, and thus generators, thereby recov-

ering part of the electricity used to liquefy

the air in the first place.

Expanding possibilities

Such cryogenic energy storage’s main pro-

ponent, a firm in London called Highview

Power, has been running a pilot grid-scale

plant in Bury, near Manchester, since April

2018. This can store 15 megawatt-hours
      (mw-hr) of energy, which is enough to pow-
      er about 5,000 homes for three hours.
      At the moment, the plant in Bury recov-
      ers as electricity just over half of the power
      used to liquefy the air in the first place.
      With design tweaks, that could probably be
      increased to 60%. Moreover, the technol-
      ogy’s inventor, Ding Yulong, sees a path to
      yet greater efficiency. As head of an energy-
      storage group at the University of Birming-
      ham, Dr Ding has spent years experiment-
      ing with a small test plant. The trick, he
      says, is to capture, probably in oil or salt,
      the heat generated as the air is compressed
      prior to its liquefaction. Some of this heat
      can then be used to boost the warming of
      the liquid air as it enters the Dearman en-
      gine. This adds oomph to the expansion,
      thereby increasing the power output.
      The rest of the heat from the compres-
      sion can be used to power a piece of refrig-
      eration kit called an absorption chiller. The
      cold this chiller creates would reduce the
      amount of electricity needed to liquefy the
      air in the first place. Dr Ding reckons that
      recycling waste heat in this way will in-
      crease the efficiency of biggish cryogenic-
      energy-storage plants to at least 69%. That
      is close to the figure obtained by banks of
      lithium-ion batteries.
      Having proved the technology, and
      raised the money to do so, the firm now
      plans to build a commercial-scale British
      plant. According to Highview’s boss, Javier
      Cavada, this will have almost twice the
      storage capacity of the world’s largest exist-
      ing lithium-ion battery, the Hornsdale
      Power Reserve in South Australia, which
      can squirrel away a mere 129mw-hr (though
      Hornsdale has a maximum power output
      of 100mw, which is twice that of Highview’s
      proposal). Construction should begin early
      next year at an as-yet-undisclosed site in
      northern England.
      Over the next two years Highview also

hopes to announce additional 250mw-hr

plants, including two it plans to build in

America for Tenaska, an energy company

in Nebraska. And Enel Group, Italy’s largest

electricity firm, is interested as well. Ac-

cording to Gianluca Gigliucci, who is lead-

ing Enel’s study of the technology, the com-

pany will soon build a grid-scale plant if

the business case for doing so appears at

least reasonable.

To take on lithium-ion batteries in a se-

rious way cryo-batteries—as Highview

dubs the technology—will have to show

that they are able to respond rapidly to fluc-

tuating demand in the way lithium-ion

cells can. They will also have to be able to

match, in future, the fall in price over the

years that such cells show every sign of

continuing to demonstrate. If they can do

these things, though, they could well

emerge as competitors in the grid-scale-

storage stakes. 7