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Solar Photo Voltaic (PV) vs. Solar Thermal Panels

Solar PV (Photo Voltaic) Panels are used to generate electricity (the term “Photo Voltaic” refers literally to the conversion of light into electricity). Solar PV Panels are distinct from Solar Thermal Panels which are primarily used to provide Daily Hot Water (DHW), but can also be used to heat your property. Solar Thermal Panels are presented as a separate Product Category on the Enerfina website.

Types of Solar PV Cells and Panels

Solar PV Panels or Modules are made up of a number of interconnected Solar PV Cells, (typically 125x125mm or 156x156m in size, for Mono and Poly Crystalline Cells). While there is a broad selection of solar PV cells available on the international market, the majority of these fall in three categories:

(1) Mono Crystalline or Monocrystalline Silicon cells;

(2) Poly Crystalline or Polycrystalline Silicon cells;

(3) Thin Film

(1) Monocrystalline Cells are made from a solid Mono Crystal, in which the lattice of the entire cell is without grain boundaries. Mono Crystalline PV Cells may render a higher level of efficiency than Poly Crystalline Cells due to the pureness of the material.

(2) Polycrystalline cells on the other hand, are a solid material composed of many crystallites of varying size and orientation. Poly Crystalline Cells can be recognized by visible grains or a “metal flake effect” and may cost slightly less than Mono Crystalline PV Cells.

(3) Thin Film Solar Cells use a fine layer of semiconducting material, such as amorphous silicon, cadmium telluride or copper indium gallium selenide, to harvest electricity from sunlight at a lower cost than Mono or Poly Crystalline Silicon cells.

Solar PV Panel Efficiency and Expected Lifespan

Traditional Mono and Poly Crystalline Solar PV Cells typically have stable efficiency levels of between 13 - 17.5%, and have an expected Lifespan of 20-25 years.

In the past, while Thin Film Solar Cells have had lower efficiency levels than Mono or Poly Crystalline Cells (6-10%), steady progress is being made, with some recent Thin-Film products exhibiting a efficiency level of 15-20% in ideal laboratory conditions. Ongoing research is under way with regard to the expected Lifespan of Thin-Film cells.

House with Solar PV Panel System

Sizing a Solar PV System

One of the key points to consider when sizing a Solar PV System is whether the system will be Stand Alone or connected to the Grid. For a Stand Alone System, the energy output of the Solar PV Panels and the Storage capacity of the batteries should be high enough to operate electrical devices at night and on cloudy days, when less sunlight is available.

Grid-connected (or Grid-tied) Solar PV Systems feed excess electrical capacity back to the local mains electrical Grid. When insufficient electricity is generated by the Solar PV system, or the batteries are not fully charged, power can be drawn down from the electricity Grid to make up the shortfall.

Solar PV Panels come in various sizes, such as 160W, 180W, 200W, 220W and even higher in certain cases. Small residential installations start from 1 kW (which would be 5-6 Panels), while 2-3 kW Installations and above, are quite common. Ancillary equipment such as cables and an Inverter are required to complete the installation.

Roof Orientation and Angle of Panel

To maximise efficiency, Solar Panels should ideally be mounted on a South / South-East / South-West facing roof, away from shadows from trees, surrounding buildings or chimneys. This enables the panels to receive as much direct solar radiation as possible. Solar Panels will also work on East or West facing roofs. For example, an East-West installation can involve installing Solar Panels on both the East and West facing roofs.

With regard to the Angle of Installation, the Solar Panel / Collector is most effective when the sun is at a 90° angle with the plane of the Collector. However, the solar angle changes throughout the day and the year. On average, the optimum inclination angle for Solar Panels in the United Kingdom and Ireland is around 30-40°, which fortunately, is also the normal pitch of a roof in this part of Europe.

Solar PV Panels - Benefits

(i) Easy to install in a New Build or to integrate into an existing property (Renovation / Retrofit).

(ii) Stand Alone or Grid Tied Systems available.

(iii) Opportunity to generate an income by selling electricity back to the Grid.

(iv) Environmentally friendly, sustainable energy source.

(v) Affordable renewable energy technology with a long Lifespan.

(vi) Minimal maintenance.

Solar PV Panels - Considerations

(i) Does your property have a roof with a Southerly orientation, or with an East / West orientation?

(ii) Are you considering a Stand Alone or a Grid Connected Solar PV System?

Solar PV Panels - Grants

For further information with regard to Renewable Energy Grants and Incentives for Solar PV Systems, please refer to the Feed In Tariffs Section, on the Grants page of the website.