Diploma Thesis Defense by Mr Konstantinos Andreou
Thesis Title: «Application of semi-transparent PVs on offices and lighting energy needs analysis»
Thursday 17 September 2020, at: 12:00, Venue: https://tuc-gr.zoom.us/j/98568550222?pwd=aHVhQURyRExlWGJMek81aU1jWXo2QT09
- Associate Professor Dionysia Kolokotsa (advisor)
- Professor Theocharis Tsoutsos
- Professor Konstantinos Kalaitzakis
One of the major challenges in modern times, is energy saving. Commercial buildings and offices are a big part of the real estate sector and they have big potential for saving energy. Beside saving energy, the aim is also to achieve visual and thermal comfort for people working in the building. Semi- transparent photovoltaics is a relatively new technology with big potential development, especially in Greece and other countries where there is a lot of sunshine for most of the year. The main challenge in developing this technology is the increase of performance of the semi-transparent PV for greater electricity production, but also the achievement of better transparencies, so people that are inside the building will have a better view of the external environment.
This paper focuses on the application of semi-transparent PVs in offices set in Athens, through modelling with the objective to find the amount of electricity produced, the availability of natural daylight, but also the energy needs for artificial lighting, while changing the basic variables like transparencies, WWR, date and time. DIALux and RETscreen expert are the software tools used for the modelling. The basic parameter for modelling, was to cover the offices with 500 lux as standard EN12464 requires. Four semi-transparent PVs were taken, which three of them was made from a-Si with transparencies 10%, 20% and 30% respectively and one which was made from c-Si with transparency 38%. They were applied through modelling on a four-floor building with south orientation and WWR ranged from 30% to 80% increased 10% at a time. The date, was set on 21st of December and 21st of June, which are the two solstices of the year, and two in between dates 21st of March and 21st of September for three hours of the day, 10:00 am, 13:00 p.m. and 16:00 p.m. The main conclusions of this paper, are that as WWR is increasing which means bigger surface covered with semi-transparent PVs and as transparency is decreasing , electricity production is rising. Although c-Si had the greater transparency, it had the most electricity production, concluding that c-Si is about four times more efficient that a-Si. Moreover, 21st of September and 21st of March had the least energy needs for artificial lighting, because of increased natural daylight which in most of the cases, caused glaring effect, especially at the offices close to window. Thus, shade rollers must necessarily be used for better visual comfort and to avoid glaring. Additionally, the energy balance for all the cases was positive, except the one with WWR 30% and 10% transparency, because of the low available natural lighting getting into the offices. Energy balance was calculated by subtracting the energy needed for artificial lighting, from the energy produced by the semi-transparent PVs.