C. Yousif1*, C. Fernandez Vazquez2 and V. Buhagiar[1]

1 Institute for Energy Technology, University of Malta, Triq il-Barrakki, Marsaxlokk, MXK 1531, Malta

2 E. T.S. Ingenieros Industriales, Universidad de Valladolid, Paseo del Cauce, s/n 47005 Valladolid, Spain

3 Faculty of Architecture & Civil Engineering, University of Malta, Tal-Qroqq, Msida, MSD 2080, Malta

Corresponding Author, charles. yousif@um. edu. mt

Abstract

This paper describes the results obtained from analysing the performance of a number of water- in-glass direct solar heating systems, which were installed on the first Energy Saving Social Housing Project in Malta. The efficiency of the systems varied between 30 and 80%, depending on the season and the hot water usage profile of the users. It was concluded that the ‘Efficiency term could be confusing to the users, as low efficiency is usually associated with a pessimistic outcome. A new parameter had to be introduced, which could provide a better explanation of the performance of the systems. This was termed the ‘Future Utilisation Potential Factor, FUPF, which is the fraction of hot water reserve for each month to the current hot water consumption. For the first time, answers to frequently asked questions were found for Malta, especially with regards to the real savings that could be expected from a solar system, the typical hot water consumption of different users, the amount of energy losses to be expected overnight and the number of days that a back-up electric heating element would be expected to switch on. These results could be instrumental to recommend solar systems, which would better fit the needs of the clients, not only based on the number of persons, but also on their hot water usage profile and any future increase in their hot water demand.

Keywords: Solar heating, evacuated-tube, water-in-glass, domestic.

1. Introduction

The domestic sector in Malta widely utilises electric boilers to heat water, which typically accounts for 15 to 30% of the household’s electricity demand. With the introduction of fuel surcharge on electricity and water bills (90% in 2008), the cost of heating water has risen dramatically. Solar heating in Malta has been introduced in the 1980’s; however it was only recently that the market started to become more active. The National Census of 2005 showed that only 5,010 solar heaters were installed in homes, covering a mere 3.6% of Maltese households [1] . Following the Government’s decision to give capital grants of up to 25% in 2006, the uptake of solar heating increased to some extent and is now estimated to have reached 10,000 to 12,000 units. Some of the major reasons for the relatively slow uptake, in spite of capital grants, were described in another publication [2] . These could be summarised as lack of legislation, poor access to information and education on solar heating and negative experiences of some users that result in skepticism in a small island scenario.