Eoin Hodge1, Chris Gibbons2

1: Energy Engineering Group, Mechanical Engineering Department, Cork Institute of Technology, Bishopstown, Cork, Ireland, email: ehodge@cit. ie 2: Energy Engineering Group, Mechanical Engineering Department, Cork Institute of Technology, Bishopstown, Cork, Ireland.

Introduction

The European Union’s long term strategy for energy supply security is geared to ensuring, for the well being of its citizens and the proper functioning of the economy, the uninterrupted physical ability of energy products on the market, at a price which is affordable for all consumers, while respecting environmental concerns and looking towards sustainable development, as detailed in Articles 2 and 6 of the treaty on European Union. Environmental concerns, which are now shared by the majority of the public and which include damage caused by the energy supply system, whether such damage is of accidental origin (oil slicks, nuclear accidents, etc.) or connected to emissions of pollutants, have highlighted the weaknesses of fossil fuels and the problems of atomic energy. The European Union target is to double the contribution of renewable energy sources from 6% to 12% of total energy consumption by the year 2010. An integral part of the EU renewables strategy is to achieve one million PV systems and five million square metres of solar collectors, by the 2010 date [2].

From an Irish perspective, an average of 3kWh/m2 of solar energy reaches Ireland everyday, being equivalent to more than 100 litres of oil per m2 per year, and is 600 times the total national energy consumption. With the recent consequence of being Europe’s fastest growing economy manifesting itself in the form of huge rises in energy use and thus pollution, we are now the second largest producers of CO2 emissions per capita, and already far exceed our emission limits under the Kyoto protocol [3].

Most solar cells presently on the market are based on silicon wafers, the so-called first generation technology. As this technology has matured costs have become increasingly dominated by material costs. In the last ten years, continuous work has brought the efficiency of standard cells to the 25% region

[4] . A switch to second generation or thin film technology cells now seems imminent. Thin film technology eliminates the silicon wafer and offer the prospect of reducing material and manufacturing costs, but they exhibit lower efficiencies of around 10% for a commercial device. Third generation or tandem cells are currently at a ‘proof of concept’ research level, with a theoretical conversion rate of 86.8% being asserted [4]. Whatever the material construction and manufacturing method of cells, the thermal effect of overheating will prevail in the semiconductor and it is accepted that a lowered temperature will bring about an increase in conversion efficiency [1].

The aim of this project is to improve the efficiency of PV electrical output, by convectively cooling the cells through perforations in them. As the cells heat

up they lose efficiency. As the panel heats up a loss in efficiency of 0.5% per °C increase in temperature has been recorded [1].