Food for thought on en­ergy

Cook­ing with­out elec­tric­ity has ma­jor ben­e­fits, writes Philip Lloyd

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CHANGES in cook­ing en­ergy could have a ma­jor im­pact on SA’s car­bon emis­sions. A re­cent study, funded by the Paraf­fin Safety As­so­ci­a­tion of SA, set out to in­ves­ti­gate whether al­ter­na­tive cook­ing fu­els could re­duce the peak load and also re­duce car­bon diox­ide (CO²) emis­sions.

Cook­ing with elec­tric­ity has a sig­nif­i­cant neg­a­tive im­pact on SA’s car­bon foot­print and places a mas­sive ex­tra load on the na­tional elec­tric­ity grid ev­ery evening. If house­holds con­verted to liq­uid petroleum gas (LPG) or paraf­fin ap­pli­ances in­stead it would re­duce peak evening elec­tric­ity con­sump­tion con­sid­er­ably and ben­e­fit the en­vi­ron­ment.

Be­fore the re­cent tar­iff hikes elec­tric­ity used to be the cheap­est op­tion for cook­ing meals. Now, how­ever, LPG and paraf­fin are be­com­ing more cost-ef­fec­tive by com­par­i­son. Cook­ing with LPG or paraf­fin also has the ad­van­tage of be­ing very much more en­vi­ron­men­tally friendly, pro­duc­ing CO² emis­sions way be­low those of elec­tric­ity from coal-fired plants.

It is es­ti­mated that 47% of all homes in SA cook on elec­tric­ity (Cen­sus 2001), which adds more than one-sixth of SA’s gen­er­at­ing ca­pac­ity to the evening peak.

If large num­bers of house­holds moved to cook­ing with mod­ern paraf­fin or LPG­fired ap­pli­ances in­stead it would en­able Eskom to sup­ply elec­tric­ity more ef­fi­ciently, as the power util­ity would no longer have to fire up ad­di­tional peak-time power plants to cope with the de­mand. Lit­tle elec­tric­ity can be stored for fu­ture use, so elec­tric­ity pro­duc­tion has to vary to meet the de­mand.

Bring­ing Eskom’s gas tur­bine plants on­line to cope with peak de­mand is costly. Cook­ing there­fore re­quires much cost­ly­gen­er­ated power and has a rel­a­tively large car­bon foot­print.

A study by the En­ergy In­sti­tute could have a ma­jor im­pact on SA’s car­bon emis­sion. It ex­am­ined the ef­fi­ciency of a num­ber of ap­pli­ances used to cook in low­in­come homes, as well as the emis­sions of the var­i­ous fu­els.

It was con­ducted be­fore the re­cent sig­nif­i­cant elec­tric­ity rate hikes and showed that elec­tric­ity was the pre­ferred op­tion for cook­ing on the ba­sis of cost. How­ever, with re­cent price hikes elec­tric­ity has now be­come roughly com­pa­ra­ble with the cost of paraf­fin.

Sim­i­larly, the cost of LPG is ex­pected to halve, which will also makes its cost of use com­pa­ra­ble to that of paraf­fin. Gel fuel seems likely to re­main an ex­pen­sive op­tion. It is al­ways prefer­able to cook us­ing a lo­cal source of en­ergy than to rely on dis­tant gen­er­a­tion.

The high ef­fi­ciency of us­ing elec­tric­ity is com­pletely off­set by the low ef­fi­ciency of gen­er­a­tion and the losses in trans­mis­sion and dis­tri­bu­tion.

Cook­ing re­quires heat, and pro­vid­ing heat by the di­rect com­bus­tion of fuel is far prefer­able to us­ing heat to gen­er­ate elec­tric­ity and the elec­tric­ity in turn to gen­er­ate heat.

The very con­sid­er­able re­duc­tion in car­bon emis­sions of us­ing a fuel di­rectly in the home sug­gests that a pro­gramme to con­vert homes from elec­tri­cal cook­ing to fu­elled cook­ing could gen­er­ate sig­nif­i­cant car­bon cred­its.

I rec­om­mend sub­sidised con­ver­sion to gas or paraf­fin cook­ing, as this would be a sim­ple way in which the de­mand for peak power could be trimmed.

Some idea of the ben­e­fit to be gained may be judged from the ex­pe­ri­ence when elec­tri­cal cook­ers were swapped for LP gas cook­ers on the Cape Flats. (Ven­ter, L. and van der Walt, M-L. 2007. A greener shade of brown: The abil­ity of com­mu­ni­ca­tion to re­duce de­mand rapidly.)

The con­ver­sion of 100 000 homes re­duced the de­mand by 40MW. Con­ver­sion of about 5-mil­lion homes from elec­tri­cal cook­ing could re­duce the peak de­mand by about 2 000MW, which would have a con­sid­er­able im­pact on the mag­ni­tude of the evening peak. To en­cour­age con­ver­sion there need to be im­prove­ments in the ef­fi­ciency of the use of paraf­fin-fu­elled ap­pli­ances, or the cost of LPG at re­tail­ers needs to fall sig­nif­i­cantly.

Philip Lloyd wishes to ac­knowl­edge Eskom Re­search and In­no­va­tion Di­vi­sion for con­duct­ing the re­search.

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