A potentway to heat portables

Withmould and money on mymind, I reached up to the air ductcrossing the ceiling of the school portable, and sure enough, warm air waswafting in eventhough the room’selectricfurnacewasshut down. Outsideitwassunny, but barelyabovezero.
Per Drewes, senior engineer for alternative energy at Ontario Hydro Technologies, held a digital thermometer to the air duct. « 28.5 ° Celsius.’’ He heldit at table level in the middle of the room. « 25 °.’’ He looked at me with a happy grin. “How about that?” No electricityrequired. No fuel. Just a section of aluminumsiding, called a Solarwall, mounted on an outsidewall. The sidingisperforatedwithpinholes, and insetwith a few photovoltaiccells.


The guysfrom Toronto Hydro, the Toronto District Board of Education, and Conserval Engineering Inc. of Downsview, which manufactures the Solarwall, grinnedtoo. And thatwasa signal for the 26 children, whospendtheirschool time in this portable, to raisemayhem up a notch. And for Katie Lynn, theirteacher, to smiletolerantly. Sheconfidedlaterthatshedidn’tmindthisclassroom invasion of ours because the childrenwereexcited about being in an experiment and, besides, shehadincorporated the dailyexperimentresultsintostudies about the weather.


The experimentaims at cutting the cost of heating portables by up to a third. And at circulatingfresh air thatwill help combat mould.


Brian Ross, supervisingengineer/electrical for the Toronto board, saysmouldis not a problem in this portable at West PreparatorySchool, a public elementaryschoolnear Bathurst St. and Eglinton Ave., becauseitisequippedwith a « ventilator’’ — a forced air system thatkeepsfresh air circulating. For portables withoutventilators, mouldcouldbe a problem, hesaid, and Solarwallscouldbe a partial solution.


The main focus withthis portable, however, iscost. Heatingitelectricallyisexpensive: $1,800 a schoolyear. You canheat a whole house for that. Ross expects to cut the electricity bill by $600 ayear.


This Solarwallis an experimental prototype, six metreswide and 2.5 metres high, with a strip of photovoltaicsacross the top. John Hollick, president of Conserval, saysthat once regularmanufacturingbegins, the installedcostwillbebetween $4,000 and $5,000. If Solarwalls are incorporatedinto the manufacture of portables, the costwillbelessthan $2,000.


According to Ross, the board has 835 portables, and a quarterlackventilators. However not all portables willbesuitable for a Solarwall, becausetheyneed to have asouth-facingwall, and it has to be free of shadowsfromtrees or other buildings.


Nevertheless, if only 5 per cent of the board’s portables — 42 units — are suitablyplaced, thatstilloffers a potentialsaving of $25,000 a yearafter the Solarwalls are paid for. Ross estimatesthat a Solarwallwillpay for itself in five to sevenyears, and in halfthat time if it’sincorporatedinto the manufacture of a portable.


Conserval has been sellingSolarwalls for severalyears, but thisis the first to includephotovoltaics. Theygenerateelectricityfromsunshine, and power twosmall fans at the top of the siding.


As the sunwarms the siding, air isdrawnthrough the pinholes, picking up heat as it passes through. The warmed air thenrises up the spacebetween the siding and the wall of the portable, and ispushed by the fans into the classroom.


The experimentismostly to find the right balance between the amount of warm air generated by the Solarwall, and the strength of the fans. If the fans runtoopowerfully, theywill push air into the classroombeforeitisadequatelyheated.


The balancingistricky, because the intensity of sunlight isconstantlychanging, while the generation of electricity has to constantly match the warming power of the perforatedsiding.


« We’restriving for simplicity. And we’restriving for hands off, maintenance free operation,’’ saysDrewes. It’s a great goal, and it looks as if they’realmostthere.

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