F. Fiedler1*, C. Bales1 and J. Vestlund1

1 Solar Energy Research Center SERC, Hogskolan Dalama, S-78188 Borlange, Sweden
* Corresponding Author, ffi@du. se

Abstract

In this study the monitoring results of prototype installation of a recently developed solar combisystem have been evaluated. The system, that uses a water jacketed pellet stove as auxiliary heater, was installed in a single family house in Borlange/Sweden. In order to allow an evaluation under realistic conditions the system has been monitored for a time period of one year.

From the measurements of the system it could be seen that it is important that the pellet stove has a sufficient buffer store volume to minimize cycling. The measurements showed also that the stove gives a lower share of the produced heat to the water loop than measured under stationary conditions. The solar system works as expected and covers the heat demand during the summer and a part of the heat demand during spring and autumn. Potential for optimization exists for the parasitic electricity demand. The system consumes 680 kWh per year for pumps, valves and controllers which is more than 4% of the total primary heating energy demand.

1. Introduction

Solar heating systems that provide domestic hot water and space heating, so called solar combisystems, have become more and more popular in the Middle and Northern European countries. Solar combisystems usually require an auxiliary heat source to be able to provide enough heat even in the seasons with low solar irradiation. In Sweden, electrical heaters and wood boilers are typically used as auxiliary heaters in solar combisystems. In recent years wood pellet boilers and stoves have also become a good alternative. The design of solar combisystems has been studied intensively in the IEA-SHC Task 26 “Solar combisystems”. A number of systems have then been, based on system simulations, optimised and improved. The results from Task 26 including a variety of technical reports and design tools are available for the public [6].

Within the Nordic research project REBUS a new combined solar and pellet heating system for the Nordic market has been designed, built and tested [4]. During this project typical existing system solutions for this combination have been investigated by the help of measurements and computer simulations [2]. It has been shown that these system solutions, due to their design and size, are often not suitable for typical Swedish houses without heating room. Also the thermal performance, such as heat losses and solar savings, offered potential for improvements. These finding have been included for the design of the new system. The first prototype of the REBUS system was tested intensively in the lab. The second improved prototype was installed in a single family house and has been monitored for a time period of one year.