THE OBJECTIVE IS THE DEVELOPMENT OF AN AUTOMATIC, EFFICIENT, NON-POLLUTING, VARIABLE OUTPUT, CENTRAL-HEATING BOILER SPECIFICALLY FOR PEAT AND BIOMASS PELLETS.
The ultimate objective of the contractors is the establishment of the PELLET FUEL SYSTEM, thereby enabling peat and biomass (straw or wood) pellets to replace distillate oil as the main central heating fuel. Although these fuels have been significantly less expensive than distillate oil on an energy basis for a considerable time they have never seriously challenged oil for 3 reasons. Firstly oil fired central heating boilers operate at far higher efficiencies than solid fuel competitors, secondly they are highly controllable in that the user can control both the temperature of the heated space and the periods during which they are heated. Finally oil is cleaner and more convenient than solid fuel, it leaves no ash and, being a liquid, it can be delivered through pipes and stored in tanks, etc.
The 2 immediate objectives are the development of an automatic, highly controllable, clean and convenient pellet fired central heating boiler which operates at high efficiency over a wide range of output, and to devise the microprocessor based control system for this boiler. The plan is to package this fully automatic pellet boiler together with existing pellet handling devices thereby establishing the PELLET FUEL SYSTEM, through which peat and biomass pellets will provide the controllable, convenient, and nonpolluting central heating at a cost well below that of oil fired boilers.
Regarding the environmental aspects, a transfer to these fuels will bring about a reduction in acid-rain and minimises the unnecessary production of carbon dioxide. These fuels take in carbon dioxide through the respiratory process during their growth.
With respect to maintenance and reliability consideration was given to achieving high efficiency without employing a heat exchanger which could require weekly cleaning, similarly clean methods of ash disposal were pursued, and great effort went into devising a boiler control system which would not require an input from a circulating water flo wmeter. These can be expensive and unreliable.
The eventual outcome was a combustion-chamber, without a heat exchanger, which operated at an efficiency of approximately 60% over an output range from 20% to 100%. This design was arrived at after 6 designs had been tested, and it has not yet been optimised. A control system has also been devised which adjusts the boiler output, while operating in either the Air Mode or the Water Mode. In the former mode it employs a room temperature error signal, and in the latter mode, it employs water temperature error signals only. The boiler provides the user with a user friendly menu driven program (the boiler can be programmed to operate at specified outputs for specified periods).
THIS BOILER TOGETHER WITH EXISTING PELLET BULK-HANDLING TECHNOLOGY WILL CONSTITUTE A PACKAGE WHICH WILL PUT PEAT AND BIOMASS IN A POSITION WHERE IT WILL PROVIDE COMFORT-HEAT AS CONVENIENTLY AS OIL DOES AT PRESENT, AT A GREATLY REDUCED COST.
IT IS THE ULTIMATE INTENTION TO DEVELOP AND ASSEMBLE SUCH A PELLET-FUEL PACKAGE. THE OBJECTIVE OF THIS RESEARCH PROJECT IS THE OPTIMISATION OF THE DESIGN OF THE COMBUSTION ZONE OF THE PROPOSED BOILER, THROUGH A THOROUGH INVESTIGATION INTO THE FACTORS WHICH INFLUENCE THE COMBUSTION OF, AND THE HEAT-TRANSFER FROM, PEAT AND BIOMASS PELLETS, AT DIFFERENT OUTPUTS.
THE RESULTS SHOULD PROVIDE THE SPECIFIC INFORMATION ON THE COMBUSTION OF PEAT AND BIOMASS PELLETS, REQUIRED FOR THE DESIGN OF AN AUTOMATIC, EFFICIENT, VARIABLE-OUTPUT, PELLET BOILER.
THE PROPOSED OBJECTIVE IS THE ACHIEVEMENT OF AN EFFICIENCY ABOVE 65% (AND HOPEFULLY REACHING 80%) OVER AN OPERATING RANGE FROM MAXIMUM OUTPUT, DOWN TO 10% OF MAXIMUM OUTPUT, I.E. SLUMBERING. THE BOILER WILL THEN HAVE THE CAPABILITY OF PROVIDING BOTH CENTRAL-HEATING DURING THE WINTER MONTHS AND ECONOMIC DOMESTIC HOT WATER DURING THE SUMMER MONTHS WITHOUT IT BEING NECESSARY TO FREQUENTLY EMPLOY THE AUTOMATIC, START-UP ELECTRIC ELEMENT. THIS ELEMENT IS CONSIDERED TO BE A DELICATE COMPONENT WHICH COULD LEAD TO UNRELIABILITY. PEAT PELLETS IN PARTICULAR HAVE GOOD SLUMBERING CHARACTERISTICS.
Funding SchemeCSC - Cost-sharing contracts