Get the BOILSIM-EXCEL software now: Contact DGC.

AN OPERATIONAL ANNUAL-EFFICIENCY-METHOD FOR DOMESTIC CENTRAL-HEATING BOILERS

All over the world there have been debates and actions to reduce CO2-emissions and the greenhouse effect.

It is known that the figures obtained in laboratory during type testing are not always representative of the real performances of the appliances because the boiler performance will depend on the installation conditions. Therefore, the concept of annual efficiency (or seasonal efficiency) has been developed.

With the support of the EU-commission, a number of EU-partners (about ten EU test-and-research institutes as well as two manufacturers) have joined their efforts in order to produce BOILSIM: a harmonised method which could be widely used. As more than 4 million boilers are installed every year in the EU, the impact of only very small improvements of efficiency are extremely important.

Work done & Results obtained
The method (in a first phase-project 1 dedicated to heating function alone) was developed and implemented - after validation - in a computer programme (BOILSIM).

For the time being;  after a pre-study (project 2); the method is extended with sanitary hot water production (project 5, for combi-boilers). Additional tools for use of BOILSIM on the replacement market have also been developed. Data on existing boilers are gathered, and methods to estimate the efficiency of installed boilers are being developed in order to calculate the energy savings obtained by replacement (project 4).

Parallel with this, a demonstration project has been carried out in Denmark (project 3, and boiler data bases are being developed (in Holland and Denmark).

The demonstration project consists of an example of extended use of the method on the Danish market. The utilisation of the results obtained is being discussed with the authorities and the boiler suppliers.

Today, the method consists of a powerful engineering tool. It can also be used for labelling purposes. The EU-commission has also shown interest in using part of the results in support of the application of a EU-directive (project 6).

New application are presently developed for a wider use of BOILSIM for the diagnosis of heating installations (project7).

Moreover, Boilsim was used in a European project for application of tools for replacement of domestic boilers (project 8).

For the time, some countries are planning to use the software for the application of the new energy in buildings directive. A specific EXCEL version was developed and can be obtained from DGC.

Principle of the method
For a given external temperature and a given installation it is possible to calculate the so-called operating conditions (load, flow etc.). These are used as input by the model to calculate a part-load efficiency with the help of a boiler part-load efficiency model.

The annual performance of a boiler is obtained by the addition of several periods where the external temperature and so the operating conditions (load, etc.) can be considered as constant.

The model parameters are calculated from CEN type tests.

The part-load model has been validated by comparison of tests performed on about 30 boilers. This is more than 240 individual tests on different kinds of boilers (incl. condensing, modulating etc.). The comparison has proven that the model is at least as good as measurements and is certainly much more reliable for low loads, for which it is known that measurements suffer from a bad accuracy.

Finally, the overall method has been implemented in an easy-to-use computer program called BOILSIM.  (A specific EXCEL version was developed and can be obtained from DGC).

Utilisation of the method
There are several levels of utilisation:

Presently, the computer program developed can be used by designers, architects etc. in order to find the best-fitted boiler for an installation or to improve an existing installation (optimization of the control-system parameters, night set-back or not etc.).

A manufacturer who wants to improve his boiler can also use the program, as it gives details on boiler losses.

For non-computer-equipped users, the method could be used as a basis to produce material to inform of the real performances of the boiler under different installation conditions. This could be very simple (label) or more sophisticated (serial of curves giving the annual efficiency as a function of the influencing installation parameters as heat demand, water temperature, control system, etc.).

For an effective and wide range of use, there would be a clear advantage to have a common-boiler data base connected to the program. This data base could be created on the basis of the European type testing report.

The future of the method
Presently BOILSIM is already operational but it is developed further in order to widen the application range. There are also discussions on having the programme available on INTERNET. More and more customers are interested in energy saving. BOILSIM on INTERNET could offer a quick and efficient evaluation of the heating installation stimulating the replacement of older boilers.

For the time, some countries are planning to use the software for the application of the new energy in buildings directive.