Investigation into control systems for low emission, high efficiency biomass furnaces for heating residential and office buildings.

Status

finished

Summary

The project started in September 2000 and will be completed in October 2001. Therefore only preliminary results are available at the moment.

The project contains the following work steps:

1. Adaptation of the test facilities of Joanneum Research so that the investigations can be carried out

In this work step, the test facilities of Joanneum Research will be adapted to allow the investigations on the control system that is to be developed to be carried out. A small biomass furnace has already been connected to a heat exchanger which is able to simulate the heat demand of different buildings. The furnace will be controlled at first by a personal computer. Later, an "SPS" control unit will be used. The control components will be fitted with input channels for the different signals which may be sent from a "Building of Tomorrow" (temperatures, state of the mechanical components of the heating system, user interface, etc.) in such a way that a complete simulated 'building' can be connected to the furnace ("Building-Simulator").

The result of this work step (Milestone MS1) was the completion of a control test rig, suitable for carrying out the planned tests.

This work step was completed as planned in December 2000. Figure 1 shows the adapted control test rig with a 50 kW biomass furnace which was placed at the disposal of Joanneum Research by the project's industrial partner, the company Herz.

2. Testing and optimisation of the combustion control of a selected biomass furnace

This work step has to be carried out between January and August 2001.

During this stage, different control programs will be tested according to the heat demand data of different buildings, acquired in the project "Specifications for biomass heating systems for buildings with low energy demand" , which was also carried out within the framework of the "Building of Tomorrow" programme.

The result of this work step, (Milestone MS2), will be detailed knowledge about the transfer of advanced control techniques from large scale to small scale biomass furnaces. Preliminary results of the investigations show that the characteristics of the 50 kW biomass furnace - from the point of view of combustion control - are similar to those of large scale furnaces. Figure 2 shows that the characteristics of the CO-emissions, the O2-concentration and the combustion chamber temperature depend on the input signal of the flue gas fan, which determines the amount of air for combustion. One can see that the CO-concentration of flue gas, measured with an analyser (CO), and the related signal, measured with a so called "Figaro-Sensor", show a significant minimum when the input signal of the flue gas fan is at a certain level. It can therefore be expected that the control systems and algorithms of large scale biomass furnaces, which continually try to move towards this minimum, can also be successfully used in small scale furnaces. However, the control systems will have to be produced at adequately low cost if their application in small scale combustion plants is to be economically viable. In view of the possibilities offered by high-tech electronics, though, one can expect that it will be possible to meet this condition.

3. Testing and optimisation of the power control of the furnace using a "Building simulator"

This work step has also to be carried out between January and August 2001.

In this stage, tests concerning the optimised heat management of the "Building of Tomorrow" will be carried out with the control test rig. The control test rig furnace will be operated according to a heat demand scenario of a low energy building obtained from the project "Specifications for biomass heating systems for buildings with low energy demand", which was mentioned above. In these tests, the following heat relevant components of the building will be taken into account:

• the heat consuming components (radiators, boilers etc.)
• the heat sources (solar collectors, heat recovery plants, heat pumps, electrical components etc.), and
• the heat accumulating components (puffer storage etc.).

The result of this work step, (Milestone MS3), will be detailed knowledge about the power control of small scale biomass furnaces directed towards high efficiency and low emissions.

4. Recommendations for optimised control of the heating system for the "Building of Tomorrow"

This work step has to be carried out in September and October 2001.

In this stage, recommendations for an optimised control unit for the heating system for the "Building of Tomorrow" will be elaborated.

The result of this work step (Milestone MS4) and the final result of the project will be a compilation of all the different results and recommendations from the project. This will help industrial partners to develop optimised control units for the heating system of the "Building of Tomorrow".

All team members are staff of Joanneum Research, Institute of Energy Research

Contact

Dipl.-Ing. Dr. Reinhard Padinger
Joanneum Research, Institute of Energy Research
Elisabethstraße 5
A 8010 Graz
Tel.: +43 316 876 1333
Fax: +43 316 876 1320
E-Mail: reinhard.padinger@joanneum.at