Yep and nope! The ones I saw at an agricultural show last week had NiCd battery backup for the air fan:- the screw feed does stop though, so in a prolonged outage, it will go out. Auto-ignition models exist.
The screwfeed pushes the fuel up a burn tube, from a bulk bin, to meet air slits or 'tuyeres' near the tube top, fed by a fan. The fire is actually 'upside down', the ash comes out at the top and falls off the edge of the 'volcano' and drops into a pan. On tickover, the feed runs for a few seconds several times an hour to keep the fire in, chip controlled of course. On full demand a searing white flame appears, [ these models had glass doors and were actually space heaters, not furnaces or boilers ]. The vendor must have been confident about the efficiency - he had two machines running in an open-front mobile, with the exhausts straight into the sales area with no flues. But this is France- just up the rue a roadside sausage-griller was pushing out enough blue acrid smoke to give Arnold a seizure!
Alan
ps. The pellets BTW were about $140 a ton, = c. 180 US Gallons of diesel oil on a calorific comparison. They are delivered by 'tanker', blown in to the store by air blast.
