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Computer modelling of wood pellet stoves and boilers connected to solar heating systems
Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
Högskolan Dalarna, Akademin Industri och samhälle, Miljöteknik.
Visa övriga samt affilieringar
2006 (Engelska)Ingår i: Proc on USB of Pellets 2006, 30 May - 1 June, Jönköping, Sweden, Jönköping, Sweden, 2006Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
Abstract [en]

When optimizing systems for wood pellet and solar heating, there is a need for realistic computer models of stoves and boilers in order to perform simulation studies. The objective of this work was to develop and verify a mathematical model for wood pellet stoves and boilers for use in system simulations with TRNSYS calculating both the energy balance and CO-emissions (carbon monoxide). Laboratory measurements have been carried out on three pellet stoves, one traditional and two with gas-liquid heat exchangers, and four pellet boilers. A mathematical two-node model of a stove was developed and implemented as a TRNSYS component. Parameters were identified for two stoves and three boilers. This new model makes it possible to perform detailed simulations with time steps less than a minute of complete wood pellet heating systems and to derive long term values, such as annual values, of efficiency and emissions for the boiler or stove in a system context under realistic conditions. In addition, parametric studies can be used in order to investigate how different operation principles and system design affect these values. The simulated energy balance of a water jacketed stove investigated in this work agreed well with measured data during both stationary and dynamic conditions.

Ort, förlag, år, upplaga, sidor
Jönköping, Sweden, 2006.
Nyckelord [en]
Pellets, stoves, boilers, efficiency, emissions, emission reduction
Identifikatorer
URN: urn:nbn:se:du-2105OAI: oai:dalea.du.se:2105DiVA, id: diva2:521612
Konferens
Pellets 2006, Jönköping, Sweden, 30 May - 1 June, 2006
Tillgänglig från: 2006-05-16 Skapad: 2006-05-16 Senast uppdaterad: 2013-09-03Bibliografiskt granskad
Ingår i avhandling
1. Combined solar and pellet heating systems for single-family houses: How to achieve decreased electricity usage, increased system efficiency and increased solar gains
Öppna denna publikation i ny flik eller fönster >>Combined solar and pellet heating systems for single-family houses: How to achieve decreased electricity usage, increased system efficiency and increased solar gains
2006 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In Sweden, there are about 0.5 million single-family houses that are heated by electricity alone, and rising electricity costs force the conversion to other heating sources such as heat pumps and wood pellet heating systems. Pellet heating systems for single-family houses are currently a strongly growing market. Future lack of wood fuels is possible even in Sweden, and combining wood pellet heating with solar heating will help to save the bio-fuel resources. The objectives of this thesis are to investigate how the electrically heated single-family houses can be converted to pellet and solar heating systems, and how the annual efficiency and solar gains can be increased in such systems. The possible reduction of CO-emissions by combining pellet heating with solar heating has also been investigated. Systems with pellet stoves (both with and without a water jacket), pellet boilers and solar heating have been simulated. Different system concepts have been compared in order to investigate the most promising solutions. Modifications in system design and control strategies have been carried out in order to increase the system efficiency and the solar gains. Possibilities for increasing the solar gains have been limited to investigation of DHW-units for hot water production and the use of hot water for heating of dishwashers and washing machines via a heat exchanger instead of electricity (heat-fed appliances). Computer models of pellet stoves, boilers, DHW-units and heat-fed appliances have been developed and the parameters for the models have been identified from measurements on real components. The conformity between the models and the measurements has been checked. The systems with wood pellet stoves have been simulated in three different multi-zone buildings, simulated in detail with heat distribution through door openings between the zones. For the other simulations, either a single-zone house model or a load file has been used. Simulations were carried out for Stockholm, Sweden, but for the simulations with heat-fed machines also for Miami, USA. The foremost result of this thesis is the increased understanding of the dynamic operation of combined pellet and solar heating systems for single-family houses. The results show that electricity savings and annual system efficiency is strongly affected by the system design and the control strategy. Large reductions in pellet consumption are possible by combining pellet boilers with solar heating (a reduction larger than the solar gains if the system is properly designed). In addition, large reductions in carbon monoxide emissions are possible. To achieve these reductions it is required that the hot water production and the connection of the radiator circuit is moved to a well insulated, solar heated buffer store so that the boiler can be turned off during the periods when the solar collectors cover the heating demand. The amount of electricity replaced using systems with pellet stoves is very dependant on the house plan, the system design, if internal doors are open or closed and the comfort requirements. Proper system design and control strategies are crucial to obtain high electricity savings and high comfort with pellet stove systems. The investigated technologies for increasing the solar gains (DHW-units and heat-fed appliances) significantly increase the solar gains, but for the heat-fed appliances the market introduction is difficult due to the limited financial savings and the need for a new heat distribution system. The applications closest to market introduction could be for communal laundries and for use in sunny climates where the dominating part of the heat can be covered by solar heating. The DHW-unit is economical but competes with the internal finned-tube heat exchanger which is the totally dominating technology for hot water preparation in solar combisystems for single-family houses.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Energy and Environmental Technology, KTH - Royal Institute of Technology, 2006
Nyckelord
Pellet, pelleteldning, kamin, panna, solvärmesystem, varmvattenberedning, systemutformning, småhus, elbesparing, verkningsgrad, emissioner, rökgasförluster, skorstensförlust, diskmaskin, tvättmaskin
Nationell ämneskategori
Energiteknik
Identifikatorer
urn:nbn:se:du-2405 (URN)
Disputation
2006-12-13, Sal M3, KTH, Brinellvägen 64, Stockholm, 10:00
Opponent
Handledare
Tillgänglig från: 2006-12-05 Skapad: 2006-12-05 Senast uppdaterad: 2013-09-03Bibliografiskt granskad

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Persson, TomasFiedler, FrankRönnelid, MatsBales, Chris
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