Countries all over the world except a few backward ones, backed by their governments are concerned with fossil fuel energy usage and are promoting renewable energy sources such as solar, wind, geothermal, bio mass generated thermal energy etc. Ireland and other members of EU are in the forefront in this exercise. The simplest and best money saver in the long run is harnessing solar energy for water heating.

Harnessing Solar Energy

Harnessing solar energy is done with three different basic methods. viz.

• Passive Method

Using various techniques that harness the sun’s energy just the way it comes for day lighting, visual aesthetic effects, heating, and also insulating and air sealing, shading and landscaping, orientation of building features etc. by the architects (whether new construction or retrofitting).

• Active Method

Active method is mainly dealing with Water Heating for domestic service or space heating. It is one of the most popular methods the world over including Europe for the purpose. The basic technique is the use of a solar collector to entrap solar energy in the medium of water (or occasionally an antifreeze) heat it and use it for a remote space heating or use it for service hot water (after sending through a heat exchanger).

When solar energy heated water (medium) is used for both applications the system is called a solar combisystem. A system gaining popularity in low energy homes in Ireland is a solar combisystem using air as a medium of thermal energy transfer. The regulated ventilation system and the heat energy collected at the solar collector are transferred to the indoor space to be heated in a single system.

Another newer Innovation uses the collected thermal energy as a source of heat in small capacity heat pumps.

A solar water heating system if correctly designed and installed, will easily account for 50 – 60% of the space heating requirement of an average Northern European home.

• Photo Voltaic (PV) systems

A PV Solar system converts sun’s energy rays impinging on it’s semiconductor panels (also called modules) converting them to DC (direct current) electricity. An array or a group of solar modules are either series or parallel connected to obtain the required voltage (generally 600 VDC maximum) and the generated power is conducted to an inverter panel where it is converted to AC electricity at 230 VAC/50hz/single phase.

Where there is no grid power supply close at hand, even in Ireland, stand alone solar PV panels or arrays are used. The electrical power supply thus available at home can be used just the way low voltage grid power supply is used, including water heating, lighting, in appliances etc.

It is interesting to note that it is not necessary at all to have direct sunlight falling on the panels for the conversion of solar energy to electricity. The panels in the Northern hemisphere are always southerly oriented for optimum collection. The generation of electricity is less in the colder seasons (when the least amount of it is needed) and high in the summer (when you require it most).

A "buy back" system is in effect in Ireland now where if your production of AC power is in excess of your needs, you can feed it to the national grid for financial benefits.

According to available statistics in year 2005, there have only been 3500 Irish homes equipped with solar heating system compared to over 5 million EU households, all using free solar energy.

The technology to heat water for domestic or commercial property applications with solar energy is today well developed. The collection of solar thermal energy, heating water with efficiently, storage, distribution, minimizing losses in transit are some processes that have been fine tuned. It is also a process with low contribution to CO2 emissions in the fight against global warming.