Alexander Thur, Simon Furbo, Louise Jivan Shah

Department of Civil Engineering, BYG DTU, Technical University of Denmark
Brovej — Building 118, DK-2800 Kgs. Lyngby, Denmark
e-mail: alt@bvg. dtu. dk. sf@byg. dtu. dk. lis@byg. dtu. dk
phone: +45 /4525 — 1887, fax: +45 / 4525 — 1755

Introduction

The energy savings for a solar heating system depend on a number of quantities related to the energy system before and without a solar heating system and after installation of the solar heating system. Often these quantities are not known. It is therefore difficult to determine the energy savings with a good accuracy. In many European countries most solar heating systems are installed in houses with an oil fired boiler or a natural gas burner. For such energy systems the savings when adding a solar heating system are determined by the following quantities:

Before solar heating:

The efficiency of the boiler/burner The electricity consumption of the boiler/burner Service costs of the boiler/burner After installation of a solar heating system:

The net utilized solar energy of the solar heating system

Energy savings due to turning off the boiler/burner during summer periods

The efficiency of the boiler/burner

The electricity consumption of the boiler/burner

The electricity consumption of the solar heating system

Service costs of the boiler/burner

Service costs of the solar heating system.

Some of the most important quantities in connection with energy savings for solar heating systems are the energy savings achieved by turning off the boiler/burner during summer periods (when efficiency of the boiler/burner typically is rather low) after installation of the solar heating system. The paper will present measurements from practice of the efficiency of an oil fired boiler and of two natural gas burners. Based on these measurements it is possible to determine the energy savings by turning off the boiler/burner during summer. Further, based on theoretical calculations, estimates of the energy savings for solar heating systems will be presented. Similar results are reported from a field test in Sweden [1].